Ferrate fe(VI)-coated sand

Abstract

This disclosure relates to a water treatment composition and the method of making the composition. The composition is a ferrate(VI)-coated sand. The ferrate-coated sand is made by mixing the sand with tetraethyl orthosilicate followed by adding the sand to a solution of potassium ferrate.

Description

FERRATE FE(VI)-COATED SANDCROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application 63 / 652,869 filed May 29, 2024, the entire disclosure of which is hereby incorporated by reference.STATEMENT OF GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with Government support under Grant No. 2242483 awarded by the National Science Foundation (NSF). The Government has certain rights in the invention.BACKGROUND

[0003] Chemical oxidation is a process utilized in water treatment to facilitate the destruction of harmful trace organic compounds such as pharmaceuticals and personal care products, pesticides, antibiotics, and industrial chemicals. Traditionally, chemical oxidation is achieved by addition of ozone or chlorine due to their potential for disinfection. However, the application of these chemicals can lead to the formation of harmful transformation products (e.g., halogenated byproducts).

[0004] Ferrate (Fe(VI)) is a multifunctional water treatment agent of interest due to its benign environmental impact yet effective for disinfecting, coagulating, and oxidizing. Fe(VI) decomposition in water produces short-lived Fe(V) and Fe(IV) intermediates which are highly effective oxidants.

[0005] Ferrate Fe(VI) is considered an environmentally benign chemical because it reduces into non-toxic Fe(III) species during application, which is often used as coagulants and adsorbents in water treatment.

[0006] However, the use of Fe(VI) as a water treatment technology for contaminant destruction is limited due to its chemical instability in solution. As the solutionpH increases to alkaline pH ranges (pH > 7.3), the Fe(VI) aqueous stability increases; however, its oxidizing power decreases.

[0007] Under acidic conditions, Fe(VI) exists as the short-lived and highly reactive protonated species HTeOi . H2FeO4, and HFeOy which undergo hydrolysis reactions to form Fe(III) species via formation and decomposition of intermediate species Fe(V) and Fe(IV) phases. Consequently, these hydrolysis reactions compete with Fe(VI)- contaminant reactions during water treatment.

[0008] The addition of SiCh gels during Fe(VI) application can facilitate Fe(V) / Fe(IV) generation and stabilize Fe(VI) reactivity for enhanced treatment. However, the application of SiCh gels is impractical and requires post-treatment disposal.SUMMARY

[0009] This disclosure leverages the SiCh stabilization and cataly tic effects on Fe(VI) to develop a Fe(VI)-coated sand water treatment media. The Fe(VI)-coated sand was synthesized by coating potassium ferrate onto sand modified with a tetraethyl orthosilicate (TeOS) precursor.

[0010] The ferrate-coated sand comprises sand particles, wherein the sand particles comprise at least 50% silica; a coating of silicate groups on an exterior of the sand particles; and ferrate(VI) ions [FeOz)]2-bonded to the coating, wherein a surface composition of the ferrate-coated sand particles comprises at least 1 wt. % of Fe.

[0011] The surface composition of the ferrate-coated sand comprises up to 6.5 wt.% of Fe.

[0012] The balance of the surface composition comprises Si, O, K, and unavoidable impurities.

[0013] The surface composition comprises from 3.6 wt.% to 40.8 wt.% of Si, from 36.4 wt.% to 57 wt.% of O, and from 1.8 wt.% to 53.5 wt.% ofK, and the unavoidable impurities include at least Cl.

[0014] The silicate groups comprise orthosilicate groups.

[0015] The sand particles comprise greater than 90% by weight silica (SiO2).

[0016] A method of making ferrate-coated sand comprises, mixing sand in tetraethyl orthosilicate to form silicate-coated sand, followed by drying the silicate-coated sand; adding the dried silicate-coated sand to a solution of potassium ferrate; allowing ferrate(VI) ions to bind to the coating; and separating the excess solution of potassium ferrate.

[0017] The method of making ferrate(VI)-coated sand further comprises adding from 0.4 ml to 0.6 ml of tetraethyl orthosilicate per gram of sand.

[0018] The method of making ferrate(VI)-coated sand further comprises adding from 25 to 26 grams of the silicate-coated sand per 100 ml of potassium ferrate solution.

[0019] A method of treating wastewater comprises, treating the wastewater containing a contaminant with a ferrate(VI)-coated sand of any of the embodiments described above.

[0020] The method includes placing the ferrate(VI)-coated sand in a sand filtration unit.

[0021] The method uses ferrate(VI)-coated sand which includes silicate groups on an exterior of the sand particles and ferrate(VI) ions [FeC^]2-bonded to the sand particles.

[0022] The method treats a contaminant including one or more of organic compounds and trace metals or a combination thereof.

[0023] The method treats organic compounds that are selected from the group consisting of phenol, acetaminophen, benzotriazole, and sulfamethoxazole, or a combination thereof.

[0024] The method treats trace metals that are selected from the group consisting of copper, lead, and zinc, or a combination thereof.

[0025] The method further comprises adding at least one compound selected from humic acid, bovine serum albumin, alginate, and octanoic acid.

[0026] The method further comprises treating for divalent cations before treating the wastewater with the ferrate (VI) coated sand.

[0027] The method further comprises treating the wastewater to adjust pH before treating the wastewater containing a contaminant with a ferrate (VI) coated sand.

[0028] A method of treating wastewater for a contaminant comprises, adding at least one compound to the wastewater, wherein the at least one compound is selected from humic acid, bovine serum albumin, alginate, and octanoic acid or a combination thereof; and treating the wastewater with a ferrate(VI)-coated sand.

[0029] The method further comprises treating for divalent cations before treating the wastewater with the ferrate(VI)-coated sand.

[0030] The method further comprises removing divalent cations with chemical precipitation, ion exchange, or membrane filtration.

[0031] The method further comprises treating the wastewater to adjust pH before treating the wastewater with the ferrate(VI)-coated sand.

[0032] The method further comprises adding a borate buffer or phosphate buffer to adjust the pH of the wastewater.

[0033] The method further comprises, in the presence of divalent cations in the wastewater, treating the wastewater with the Fe(VI)-coated sand to remove trace metals.

[0034] The method further comprises, in the presence of divalent cations in the wastewater, treating the wastewater with the Fe(VI)-coated sand to oxidize contaminants containing electron-donating moieties.

[0035] The electron-donating moieties include phenol or amine moieties or a combination of phenol and amine.

[0036] A method of treating wastewater comprises, in the presence of divalent cations in the wastewater, treating the wastewater with a ferrate (VI) coated sand to oxidize a contaminant having phenol or amine moieties. The contaminant can be acetaminophen.

[0037] This summan' is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.DESCRIPTION OF THE DRAWINGS

[0038] The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0039] FIGURE 1 is a graph showing total Fe leached from the Fe(VI)-coated sand prepared with and without TeOS-sand modification (3 hr. reaction);

[0040] FIGURE 2 shows bar graphs of total aqueous Fe concentration after 1 g / L Fe(VI)-coated sand was stirred in 1% v / v HNOs for 1 min, 1 hr, 12 hrs and 24 hrs (the Fe(VI)-coated sand was prepared with virgin sand (no TeOS), 3hr. reacted with TeOS sand, and 24hr. reacted TeOS sand;

[0041] FIGURE 3 is a graph showing spectroscopic analysis of TeOS stability on TeOS-coated sand, the UV-Vis spectrum of the supernatant of 1 g / L TeOS-coated sand (dashed line) placed in 10 mM borate buffer and sonicated was compared to the UV-Vis spectrum of TeOS (4 mL solution), the absence of a peak at 292 nm in the spectrum of the TeOS-sand indicates that TeOS did not leach from the TeOS-coated sand surface;

[0042] FIGURES 4A, 4B, 4C are graphs showing kinetics of Fe(VI), Fe(III) and total Fe leached from 1 g per L Fe(VI)-coated sand into a 10 mM NaJ34O7solution at pH 7(FIGURE 4A), pH 8 (FIGURE 4B), pH 9 (FIGURE 4C) as a function of time, where max total Fe refers to the maximum mass of Fe that would leach of the surface of Fe(VI)-coated sand, which was determined by mixing 1 per L Fe(VI)-coated sand into 1% v / v HNCh;

[0043] FIGURES 5A, 5B, 5C are graphs showing kinetics of Fe(VI), Fe(III) and total Fe leached from 1 g / L Fe(VI)-coated sand with 3hr-TeOS sand modification into a 10 mM Na2HPO4 / NaH2PO4solution at pH 7 (FIGURE 5 A), pH 8 (FIGURE 5B). pH 9 (FIGURE 5C) as a function of time, where max total Fe refers to the maximum mass of Fe that would leach of the surface of Fe(VI)-coated sand, which was determined by mixing 1 g / L Fe(VI)-coated sand into 1% v / v HN03 and measuring total Fe in solution, wherein the total Fe refers to the total Fe leached into solution at a given time;

[0044] FIGURES 6A, 6B are graphs showing decay of Fe(VI) in (FIGURE 6A) 0.21 g / L K2FeO4 powder and (FIGURE 6B) 1 g / L Fe(VI)-coated sand, where the 0.21 g / L initial concentration of IGFeCU was chosen to obtain a concentration of Fe(VI) that will be equivalent to the concentration of total Fe in the Fe(VI)-coated sand system;

[0045] FIGURE 7 is a graph showing the total Fe and Fe(VI) coating mass leached from Fe(VI)-coated sand surface as a function of time, where 3 g / L Fe(VI)-coated sand was mixed with 1 % v / v HNOs for the total Fe measurement, and for the Fe(VI) coating mass determination, 3 g / L Fe(VI)-coated sand was mixed with 5 mM Na2HPO4 / lmM NaB4O? buffer;

[0046] FIGURES 8A, 8B are graphs of (FIGURE 8B) effect of Fe(VI)-coated sand dose on the removal of 236 ± 0.6 mg per L phenol in 10 mM borate buffer pH 9 and (FIGURE 8A) the measured Fe(VI) concentration remaining in solution after 30 min of reaction with phenol treatment;

[0047] FIGURES 9A, 9B, 9C, 9D are graphs showing degradation of 219 ± 12 mg per L phenol in 10 mM borate buffer pH 9 by (FIGURE 9A) 12.6 mg per L Fe(VI) powder and (FIGURE 9B) 2 g per L Fe(VI)-coated sand, the phenol removal efficiency(left axis) and phenol to maximum aqueous Fe(VI) concentrations ratio (right axis) are shown with respect to time, where the Fe(VI) concentration at 5 min was taken as the maximum aqueous Fe(VI) concentration, and (FIGURES 9C, 9D) show corresponding changes in aqueous Fe;

[0048] FIGURES 10A, 10B are graphs showing removal of 283 ± 2.1 mg per L phenol and 865 ± 15 mg per L PMSO by 2 g per L Fe(VI)-coated sand, and (FIGURE B) changes in aqueous Fe concentration;

[0049] FIGURES 11 A, 11B are SEM images of non-coated Ottawa sand, and FIGURES 11C, 11D are SEM images of Fe(VI)-coated sand;

[0050] FIGURES 12A, 12B, 12C are graphs showing removal of nominally 500 pg / L Cu. Pb. Zn (each) by 2 g / L Fe(VI)-coated sand (FIGURE 12A) in the M9 system; and in the presence of nominally 500 pg / L ACM, BZT and SMZ (each) (FIGURE 12B) in the MO9 and (FIGURE 12C) MO7.5 systems;

[0051] FIGURES 13 A, 13B. 13C, 13D are graphs showing removal of nominally 500 pg / L trace organics (FIGURES 13A, 13C) and trace metals (FIGURES 13B, 13D) by 26±1.8 mg / L Fe(NO3)3in the (A) MO9 system and (B) MO7.5 system;

[0052] FIGURE 14A, 14B, 14C, 14D are graphs showing control experiments (no Fe(VI)-coated sand) with nominally 500 pg / L Cu, Pb and Zn in (FIGURE 14A) M9 system; (FIGURE 14B) MO9 systems in the presence of select trace organics (FIGURE 14C) MO7.5 system in the presence of select trace organics and (FIGURE 14D) the synthetic wastewater effluent solution in the presence of select trace organics;

[0053] FIGURE 15 is a graph showing normalized degradation of nominally 500 pg / L ACM, BZT, SMX (each) by 2 g / L Fe(VI)-coated sand in the 09 system;

[0054] FIGURE 16 is a graph showing normalized degradation of nominally 500 pg / L ACM, BZT, SMX by 2 g / L Fe(VI)-coated sand in the MO9 system in the presence of nominally 500 pg / L Cu, Pb, Zn (each);

[0055] FIGURE 17 is a graph showing normalized degradation of nominally 500 pg / L ACM, BZT, SMX by 2 g / L Fe(VI)-coated sand in the MO7.5 system in the presence of nominally 500 pg / L Cu, Pb, Zn (each);

[0056] FIGURES 18A, 18B are graphs showing removal of nominally 500 pg / L (each) of (FIGURE 18 A) ACM, BZT, and SMX; and (FIGURE 18B) Cu, Pb, and Zn by 2 g / L Fe(VI)-coated sand in synthetic wastewater effluent solution as a function of time;

[0057] FIGURE 19A is a graph showing degradation of nominally 250 pg / L PHE in 10 mM Na2B4O7 pH 9 buffer in the presence of 10 mg-C / L synthetic effluent organic matter by 2 g / L Fe(VI)-coated sand (open circles) and in the absence of Fe(VI)-coated sand (shaded circles);

[0058] FIGURE 19B is a graph showing normalized concentration of total organic carbon (TOC) during degradation of nominally 250 pg / L PHE by 2 g / L Fe(VI)- coated sand (open squares) and in the absence of Fe(VI)-coated sand (shaded squares);

[0059] FIGURE 20A is a graph showing normalized concentration of nominally 50 pg / L (each) of ACM, PHE, and SMX treated by 2 g / L Fe(VI)-coated sand in SWE in the presence of sEfOM;

[0060] FIGURE 20B is a graph showing normalized concentration of nominally 50 pg / L (each) of Cu and Zn treated by 2 g / L Fe(VI)-coated sand in SWE in the presence of sEfOM;

[0061] FIGURES 21 A, 21 B, 21 C, 21D are graphs showing normalized degradation of nominally 50 pg / L (each) of ACM, PHE, and SMX by 2 g / L Fe(VI)-coated sand in the presence of nominally 50 pg / L of Cu, Pb, and Zn (each) in the SWE matrix in the presence of (FIGURE 21 A) BSA only, (FIGURE 2 IB) HA only, (FIGURE 21 C) ALG only, and (FIGURE 2 ID) OA only

[0062] FIGURE 22A, 22B, 22C, 22D are graphs of control experiments (no Fe(VI)-coated sand) with nominally 50 pg / L ACM, SMX, PHE, Cu, Pb and Zn each in(FIGURE 22A, 22B) the absence of synthetic effluent organic matter and (FIGURE 22C, 22D) the presence of nominally 10 mg-C / L synthetic effluent organic matter.

[0063] FIGURES 23A, 23B, 23C, 23D are graphs showing concentrations of nominally 50 pg / L (each) of Cu, Pb, Zn in the presence of nominally 50 pg / L of ACM. PHE, and SMX (each) reacted with 2 g / L Fe(VI)-coated sand in the SWE matrix in the presence of (FIGURE 23A) BSA only, (FIGURE 23B) HA only, (FIGURE 23C) ALG only, and (FIGURE 23D) OA onlyDETAILED DESCRIPTION

[0064] This disclosure is related to Fe(VI)-coated sand, to a method of making the Fe(VI)-coated sand, and to the use of the Fe(VI)-coated sand as water treatment media for the removal of organic and trace metal contaminants.

[0065] The acronyms in this disclosure shall have the following meanings.

[0066] ABTS-(2,2’-azinobis-(3-ehtylbenzothiazoline-6-sulfonate)

[0067] ACM-acetaminophen

[0068] ALG-alginate

[0069] BSA-bovine serum albumin

[0070] BZT-benzotri azole

[0071] EfOM-effluent organic matter

[0072] HA-humic acid

[0073] ICP-OES-inductively coupled plasma optical emission spectroscopy

[0074] OA-octanoic acid

[0075] PHE-phenol

[0076] PMSO-methyl phenyl sulfoxide

[0077] sEfOM-synthetic effluent organic matter

[0078] SEM-scanning electron microscopy

[0079] SMX-sulfamethoxazole

[0080] SWE-synthetic wastewater effluent

[0081] SWW-synthetic wastewater

[0082] TeOS-tetraethylorthosilicate

[0083] TOC-total organic carbon

[0084] Coating Fe(VI) onto a sand surface presents an opportunity for increasing Fe(VI) stability and for better deployment of Fe(VI) in water treatment applications. The Fe(VI)-coated sand offers an environmentally benign water treatment media that would be applicable to treatment systems (e g., advanced wastewater treatment systems) where sand filtration systems are already in use. The Fe(VI)-coated sand limits the need for solid substrates like SiO2 gels that may require post-treatment disposal. The reduction of Fe(VI) to Fe(III) after treatment and the potential for synergistic treatment processes (i.e.. oxidation, coagulation, disinfection, and filtration) due to Fe(VI) multimodal properties make this Fe(VI)-coated sand a cost-effective and eco-friendly water treatment media suitable for deployment in many water treatment applications. Removal of organic compounds by the Fe(VI)-coated sand can occur through removal by aqueous Fe(VI), removal by suspended Fe(III) particles, and removal on the sand surface.

[0085] The synthesis method disclosed produces viable and stable Fe(VI)-coated sand. The method includes initially modify ing the sand with a coating of tetraethyl orthosilicate (TeOS). The method using TeOS modified sand yielded Fe(VI)-coated sand media with at least 44% by weight greater Fe bound to the surface and a greater binding attachment compared to comparative media produced without TeOS sand modification. In this disclosure, the terms “ferrate-coated sand’’ and “Fe(VI)-coated sand” and “ferrate(VI)- coated sand” shall refer to the sand first coated with a silicate surface modification then coated with, for example, potassium ferrate, unless otherwise stated.

[0086] Tetraethyl orthosilicate is a representative silicate described in this disclosure. A silicate can be any polyatomic anion having silicon and oxygen with thegeneral formula [SiO4-x]n. Orthosilicates have the general formula |SIO4|4“. The orthosilicates can have from 1 to 4 alkyl substituents selected from Cl or C2.

[0087] This disclosure describes the effects of water chemistries (i.e., pH and buffers) on the rate of Fe(VI) decomposition and leaching from the Fe(VI)-coated sand surface. The mass of Fe(VI) leached from the media surface increased with increasing pH from 7 to 9. The Fe(VI) self-decay was accelerated at pH 7 (k = 3.87 mg'1L'1hr'1) and slowed with increasing pH (k = 0.04 mg'1L'1hr'1at pH 9). Borate ions promoted a faster decay (k = 2.22 mg L'1hr'1) of the Fe(VI)-coated sand compared to phosphate ions (k = 3.39 mg L'1hr'1).

[0088] This disclosure describes the treatment of phenol by the Fe(VI)-coated sand and by a K2FeO4 (Fe(VI)) powder. The comparison revealed that the Fe(VI)-coated sand had a removal capacity7that is 1.4 times greater than that of Fe(VI) powder (51% removed by the ferrate-coated sand after 5 min compared to 37% removed by the powder). Furthermore, the fast and complete removal of phenol in the presence of phenyl methyl sulfoxide (PMSO) compared to the incomplete removal of phenol in the absence of PMSO indicates an increased production of highly reactive Fe(V) and Fe(IV) intermediate species. Decomposition of Fe(VI) from the surface in the presence of methyl phenyl sulfoxide (PMSO) suggests that reactive Fe(V) and Fe(IV) formation occurs at a faster rate than with K2FeO4 powder addition. In the presence of PMSO, phenol removal was approximately 1.1 times higher, which suggests Fe(V) / Fe(IV) involvement.

[0089] This disclosure describes the use of the Fe(VI)-coated sand for the treatment of organic compounds, such as acetaminophen (ACM), benzotriazole (BZT), sulfamethoxazole (SMX), and trace metals, such as copper (Cu). lead (Pb), and zinc (Zn). in ultrapure and synthetic wastewater. The Fe(VI)-coated sand can be used for the treatment of wastewater including many organic compounds and trace metals that are common contaminants found in wastewater effluents.

[0090] This disclosure describes the effect of effluent organic matter (EfOM) composition, such as octanoic acid (OA), bovine serum albumin (BSA), alginate (ALG) and humic acid (HA), on Fe(VI)-coated sand treatment of acetaminophen (ACM), phenol (PHE). sulfamethoxazole (SMX), copper (Cu), lead (Pb), and zinc (Zn) in a synthetic wastewater effluent matrix.

[0091] This disclosure describes the treatment capacity of Fe(VI)-coated sand in a complex and varied matrix containing whole EfOM or EfOM components, trace metals, and organic compounds commonly found in wastewater effluents to evaluate the Fe(VI)- coated sand media under representative water treatment contexts.

[0092] EfOM is a mixture of natural organic matter, soluble microbial products and micropollutants and is a component of secondary effluent discharge and tertiary treatment for wastewater reuse applications. The presence and subsequent removal of EfOM during wastewater treatment can aid in alleviating the chemical toxicity of wastewater effluents.

[0093] In the treatment of acetaminophen, benzotriazole, sulfamethoxazole, copper, lead, and zinc, the Fe(VI)-coated sand reactivity was influenced by the solution pH and the aqueous chemistry. For example, removal of Zn and Pb improved by 52% and 49% in the presence of trace organics indicating that trace metals removal was enhanced by Fe(III) phases formed during Fe(VI) reaction with the trace organics.

[0094] While oxidation with the Fe(VI)-coated sand of trace organic compounds increased as pH decreased, trace metals sorption was more favorable at higher pH (i.e.. pH 8 and 9). Oxidation efficiency of trace organics by the Fe(VI)-coated sand was highest for ACM and SMX. BZT degradation was limited due to formation of Cu-BZT complexes. The presence of divalent cations (i.e., Ca2+and Mg2+) in synthetic wastewater effluent solutions can catalyze Fe(VI) self-decay and promote Fe(III) production and subsequent trace metals removal; however, oxidation of trace organics could be hindered.

[0095] Fe(VI)-coated sand treatment of acetaminophen (ACM), benzotriazole (BZT), sulfamethoxazole (SMX), copper (Cu), lead (Pb), and zinc (Zn) revealed that the Fe(VI) had a greater affinity for the trace organics, especially for ACM for which removal efficiency exceeded 90%. The presence of Cu in the treatment systems inhibited BZT removal due to the formation of Cu-BZT complexes. A faster removal of ACM and SMX was achieved at pH 7.5 compared to pH 9 indicating that the lower, environmental pH is favorable for trace organic oxidation due to the increased presence of HFeOL ions in solution. The removal of ACM and SMX decreased at pH 9 in the presence of trace organics and at pH 8 in the presence of trace metals and inorganics ions, suggesting that at pH values where HFeOC ions exist in smaller quantities, the removal of trace organics depends on the ratio of Fe(VI) to contaminants.

[0096] While Cu and Pb removal was partially attributed to the removal of their mineral solid phases, Zn removal occurred solely via interaction with the Fe(VI)-coated sand. Thus, the increased removal of Zn in the presence of trace organics indicated that trace metals removal was achieved by Fe(III) formed in solution after Fe(VI) reaction with the trace organics.

[0097] While the effluent organic matter influenced the degradation of SMX and PHE, there was no observed effect for ACM. For example, in the presence of HA, 80% PHE degradation was observed within 15 min of reaction by the Fe(VI)-coated sand compared to only 60% in the presence of BSA. BSA was observed to decrease Fe(VI)- coated sand reactivity towards SMX and PHE. Removal of Cu, Pb and Zn was near complete in the presence of OA within 15 min of reaction but varied (59-100%) in the presence of BSA, HA and ALG indicating that EfOM composition also affects Fe(VI)- coated sand reactivity towards metals.

[0098] The synthetic EfOM (sEfOM) including BSA, HA, OA, and ALG interacted with the trace metals and not the trace organics in the reaction systems in theabsence of the ferrate-coated sand media. These interactions (e.g., metal complexation) coupled with pH effects and sorption to solid mineral phases facilitated trace metals removal by the ferrate-coated sand in the wastewater effluent matrix. While sEfOM had an overall enhancing effect on the degradation of the trace organics, BSA promoted a faster decomposition of Fe(VI) thus reducing trace organics removal efficiency.

[0099] This disclosure demonstrates the potential for Fe(VI)-coated sand media for treatment of multiple contaminants in complex matrices such as in wastewater effluents. Here, the contaminant concentrations tested can be higher than typical concentrations of trace organics and trace metals in the environment.

[0100] Given the multimodal properties of Fe(VI) (i.e., oxidant, disinfectant, and coagulant), the use of Fe(VI) could reduce economical and spatial costs for water treatment plants by combining pre-disinfection, oxidation, and coagulation into one unit. Therefore, the use of a Fe(VI)-coated sand media could be beneficial in water treatment systems that include filtration units as sand (composed of greater than 80% SiCh content is a widely used filtration media).

[0101] An embodiment of the disclosure includes a ferrate-coated sand, comprising: sand particles, wherein the sand particles comprise at least 50% silica; a coating of silicate groups on an exterior of the sand particles; and ferrate(VI) ions [FeO^2-bonded to the coating, wherein a surface composition of the ferrate-coated sand particles comprises at least 1 wt. % of Fe.

[0102] The application of a silicate coating, such as TeOS, increases the bonding of Fe(VI). The silicate coating can also enhance the storage life of Fe(VI)-coated sand modified with TeOS. The mass (mg Fe / g sand) leached from the Fe(VI)-coated sand surface as a function of time ranges from about 2 from 0 to 7 days to about 1.5 after 10 days for Fe(VI), and from about 7.5 to about 6 from 0 to 3 days and about 6.5 after 10 days for total Fe.

[0103] The surface composition can comprise up to 6.5 wt.% of Fe.

[0104] The ferrate(VI)-coated sand of claim 1, wherein a balance of the surface composition comprises Si, O, K, and unavoidable impurities.

[0105] The surface composition can comprise from 3.6 wt.% to 40.8 wt.% of Si. from 36.4 wt.% to 57 wt.% of O, and from 1.8 wt.% to 53.5 wt.% of K, and the unavoidable impurities include at least Cl.

[0106] The silicate groups can comprise orthosilicate groups.

[0107] The sand particles comprise greater than 90% by weight silica (SiO2).

[0108] In an embodiment, a water treatment media comprises the ferrate-coated sand.

[0109] In an embodiment, a method of making ferrate(VI)-coated sand, comprises mixing sand in tetraethyl orthosilicate to form silicate-coated sand, followed bydrying the silicate-coated sand; adding the oven-dried silicate-coated sand to a solution of potassium ferrate(VI); allowing ferrate(VI) ions to bind to the sand particles; and separating the excess solution of potassium ferrate(VI).

[0110] The method can comprises adding from 0.4 ml to 0.6 ml of tetraethyl orthosilicate per gram of sand. However, other silicates may be used.

[0111] The method can comprises adding from 25 to 26 grams of the silicate- coated sand per 100 ml of potassium ferrate solution.

[0112] Spectroscopic characterization of the sand surfaces indicates greater Fe(VI) coating densities in the presence of TeOS. TeOS modification of the sand prior to Fe(VI) coating increased Fe(VI) binding to the sand surface.

[0113] The decay rate of the ferrate (Vl)-coated sand is 0.23 mg L^hr1. For comparison, the decay rate of K2FeO4powder is 1.14 mg L^hr1.

[0114] In an embodiment, a method of treating water and wastewater can comprise treating the wastewater containing a contaminant with a ferrate(VI)-coated sand.

[0115] The ferrate(VI) coated sand is placed in a sand filtration unit.

[0116] The ferrate(VI) coated sand can include silicate groups on an exterior of the sand particles and ferrate(Vl) ions [FeO4]2' bonded to the sand particles.

[0117] The contaminant can include one or more of organic compounds and trace metals or a combination thereof.

[0118] The organic compounds are selected from the group consisting of phenol, acetaminophen, benzotriazole, and sulfamethoxazole, or a combination thereof.

[0119] The trace metals are selected from the group consisting of copper, lead, and zinc, or a combination thereof.

[0120] The method further comprises adding at least one compound selected from humic acid, bovine serum albumin, alginate, and octanoic acid.

[0121] The method further comprises treating for divalent cations before treating the wastewater with the ferrate (VI) coated sand.

[0122] The method further comprises treating the wastewater to adjust pH before treating the wastewater containing a contaminant with a ferrate (VI) coated sand.

[0123] A method of treating wastewater for a contaminant comprises, adding at least one compound to the wastewater, wherein the at least one compound is selected from humic acid, bovine serum albumin, alginate, and octanoic acid or a combination thereof; and treating the wastewater with a ferrate(VI)-coated sand.

[0124] The method further comprises treating for divalent cations before treating the wastewater with the ferrate(VI)-coated sand.

[0125] The method further comprises removing divalent cations with chemical precipitation, ion exchange, or membrane filtration.

[0126] The method further comprises treating the wastewater to adjust pH before treating the wastewater with the ferrate(VI)-coated sand.

[0127] The method further comprises adding a borate buffer or phosphate buffer to adjust the pH of the wastewater.

[0128] The method further comprises, in the presence of divalent cations in the wastewater, treating the wastewater with the Fe(VI)-coated sand to remove trace metals.

[0129] The method further comprises, in the presence of divalent cations in the wastewater, treating the wastewater with the Fe(VI)-coated sand to oxidize contaminants containing electron-donating moieties.

[0130] The electron-donating moieties include phenol or amine moieties or a combination of phenol and amine.

[0131] A method of treating wastewater comprises, in the presence of divalent cations in the wastewater, treating the wastewater with a ferrate (VI) coated sand to oxidize a contaminant having phenol or amine moieties. The contaminant can be acetaminophen.

[0132] An advantage of Fe(VI) is its reduction into Fe(III) species, thus making it possible for the dual treatment of organic contaminants through oxidation and inorganic contaminants through adsorption by Fe(VI) in a single unit process.

[0133] Applying the Fe(VI)-coated sand media presents an opportunity for advancing water treatment processes with additional capabilities (i.e., oxidation, coagulation, and disinfection) due to the multimodal properties of Fe(VI). However, pH and matrix composition in treatment systems also greatly influence Fe(VI)-coated sand reactivity. For example, divalent cations lessened the oxidation of trace organics but increased trace metals removal by Fe(VI)-coated sand.

[0134] The use of a silicate, such as TeOS, as a coating on the sand prior to applying the potassium ferrate results in an increase in the Fe(IV) coating density. Spectroscopic characterization of TeOS-modified sand surfaces indicates greater Fe(VI) coating densities in the presence of TeOS.

[0135] Referring to FIGURE 1, ICP-OES analysis of the temporal Fe leached from the Fe(VI)-coated sand revealed that Fe(VI)-coated sand synthesized with TeOS-sand had approximately 44% higher initial Fe loading compared to unmodified sand, indicating a higher Fe coating density in the presence of TeOS. The decay rate of Fe(VI) of TeOS modified sand is 4.34±0.74 mg / L-min compared to 2.44 ±0.32 mg / L-min of non-modified sand. In this disclosure, the terms “ferrate-coated sand,” “Fe(VI)-coated sand”, “ferrate(VI)-coated sand” shall refer to Fe(VI)-coated sand modified with a silicate, such as TeOS, unless stated otherwise.

[0136] FIGURE 2 shows bar graphs illustrating the amount of Fe leached from TeOS-modified and unmodified sand at various leaching times and for various mixing times of the TeOS with the sand prior to potassium ferrate addition. ICP-OES analysis of the acid-treated leachate from the TeOS modified and unmodified sand surfaces confirm that TeOS modification increases Fe coating mass.

[0137] Additionally, as illustrated in FIGURE 3, spectroscopic analysis revealed a stable TeOS coating (i.e., no leaching of TeOS) on the sand surface. Had the TeOS leached from the sand surface, the UV-Vis spectrum of the supernatant of TeOS-sand sonicated in the 10 mM borate buffer would have shown an absorbance peak at 292 nm as corresponding to the presence of TeOS.

[0138] The solution pH and buffering ions can govern Fe(VI)-coated sand stability. FIGURES 4A, 4B, 4C and FIGURES 5A, 5B, 5C are graphs illustrating total Fe, Fe(VI), and Fe (III) concentration leached from TeOS modified sand at a pH of 7, 8, and 9 in a buffered solution of borate and phosphate, respectively. Analysis of Fe(VI) leaching kinetics suggests that the Fe(VI)-coated sand aqueous stability increases with increasing pH. Leaching experiments were conducted with the Fe(VI)-coated sand in buffered solutions (10 mM phosphate and 10 mM borate) at pH 7, 8, and 9 to evaluate the effect of pH and inorganic ions on the aqueous stability of the media. Initially, the Fe(VI)-coatedsand was sonicated in 1% HNCh to desorb all the Fe from the coated sand surface and to quantify the total Fe coating density on the media. This total Fe (9.4±0.8 mg / L) is designated as the maximum total Fe coating on the sand. The maximum total Fe concentration was greater than the aqueous total Fe concentrations at time t (t = 5-180 min) suggesting that Fe(VI) desorption from the coated sand is not instantaneous.

[0139] A delayed desorption of Fe(VI) from the TeOS-coated sand surface presents an opportunity for improved treatment of organic contaminants during water treatment. In solution, the Fe(VI)-coated sand media would include: (i) aqueous Fe(VI) leached from the sand surface; (ii) aqueous Fe(III) leached from the sand surface or produced from aqueous Fe(VI) decay; (iii) Fe(III) solids suspended in solution; and, (iv) Fe(VI) and / or Fe(III) bound to the sand surface. Thus, contaminant removal can occur simultaneously via reactions with Fe(VI) and Fe(III) in different phases and configurations.

[0140] The Fe(VI)-coated sand exhibited slower decomposition kinetics at circumneutral pH. Fe(VI) stability' tests confirm that the Fe(VI) leached from the Fe(VI)- coated sand was more stable at pH 9 than at pH 7 and 8. Aqueous decomposition of Fe(VI) was minimal at pH 9. The aqueous Fe(VI) decay rates in the borate buffer were estimated at 355.4, 0.82, 0.004 mg'1L'1hr'1at pH 7, 8, 9 respectively. At pH 7, the dominant Fe(VI) species is HFeOT (-67%) which has a higher oxidizing potential than the deprotonated FeC>42'. The high oxidizing potential of the dominant HFeOT species and fast reactions with water result in the instability of aqueous Fe(VI) at pH 7. The self-decay of aqueous Fe(VI) was lessened at pH 8 and can be attributed to the dominant species, FeO42' (-83%) being less reactive than the HFeC ' species.

[0141] Due to the increased production of Fe(III) at pH 7 and 8. sorption and coagulation can be the major mechanisms of contaminant removal whereas at pH 9, oxidation of organic compounds may be the more dominant treatment mechanism.

[0142] At pH values where Fe(VI) decays faster, the treatment of organic contaminants by the Fe(VI)-coated sand media may occur by these pathways: (i) physical adsorption of the contaminants on the coated sand surface followed by oxidation by surface-bound Fe(VI) species, (ii) sorption to surface-bound Fe(III) particles; (iii) limited oxidation by Fe(VI) in the aqueous phase, and (iv) sorption and coagulation with Fe(III) particles in the aqueous phase.

[0143] The aqueous stability of the Fe(VI)-coated sand is also affected by the buffering ions. At pH 8 and 9, aqueous Fe(VI) and total aqueous Fe concentrations were lower in the borate buffer than in the phosphate buffer. At pH 8, the total aqueous Fe concentration in the borate buffer within 0.5 hour of mixing was 4.26 ± 0.27 mg / L and 7.43±0.76 mg / L in the phosphate buffer. Additionally, the total Fe concentrations at pH 7 and 8 were constant in the phosphate buffer as seen in FIGURES 5A, 5B, yet the Fe concentration decreased with time in the borate buffer except at pH 9 as seen in FIGURE 4C. These results imply that while Fe desorption from the media surface is lessened in the borate buffer, Fe(VI) decay was enhanced. A linear regression fitted to the measured Fe(VI) concentrations in both buffered solutions at pH 8 shows that the slope for the borate buffer was 65% smaller than the slope for the phosphate buffer indicating that Fe(VI) decay was slower in the phosphate buffer. The results of the leaching experiments suggest faster Fe(VI) decay would occur when the Fe(VI)-coated sand media is placed in certain pH and buffering conditions.

[0144] FIGURES 6A and 6B compare the decay rates of the Fe(VI) coated sand and a potassium ferrate powder. FIGURE 6A shows the stability’ of Fe(VI) when K2FeO4 powder is dissolved in the borate buffer at pH 9. FIGURE 6A shows Fe(VI) decays faster at a rate of 1.14 mg L'1hr1compared to the Fe(VI)-coated sand in FIGURE 6B where Fe(VI) decay was estimated at 0.23 mg L'1hr1. FIGURE 6B validates the SiCh stabilization effect on Fe(VI).

[0145] FIGURE 7 is a graph to illustrate the stability of the Fe(VI) coated sand stored for various lengths of time. The stability of the stored Fe(VI) coated sand was assessed by determining changes in total Fe and Fe(VI) on the sand surface at time t (in days) after the Fe(VI)-coated sand was produced. The total measured Fe varied between 5.69±0.99 to 7.39±1.01 mg Fe / g sand. The degree of variability could be due to slight differences in coating density at different sites on the sand surface. Fe(VI) concentrations (-2.43 mg Fe(VI) / g sand) remained constant for up to 7 days after media production then slightly decreased (1.29 mg Fe(VI) / g sand) after 7 days.

[0146] FIGURE 8B is a graph showing the removal of phenol at various doses of the Fe(VI) coated sand at a pH of 9, and FIGURE 8A is a graph showing the Fe(VI) concentration at the same doses remaining after 30 minutes. As seen in FIGURE 8B. the removal of phenol increases with increasing doses of the Fe(VI)-coated sand and plateaus after 2 g / L. At this dose, 97% removal of phenol at an initial concentration of 236 pg / L was achieved.

[0147] FIGURES 9A and 9B are graphs comparing the phenol degradation efficiency and FIGURES 9C and 9D show the aqueous Fe concentration of the Fe(VI)- coated sand and an Fe(VI) powder (i.e., 2 g / L Fe(VI)-coated sand and 12.6 mg / L JGFeCh powder). Comparing FIGURES 9A and 9B shows that the Fe(VI)-coated sand enhances the treatment time of ferrate Fe(VI) toward organic compounds. Both the ferrate Fe(VI)- coated sand and the IGFeCh powder had similar removal efficiencies (85% for K2FeO4 powder and 83% for Fe(VI)-coated sand) of phenol at the end of the reaction time (2 hour); however, phenol removal was faster by the Fe(VI)-coated sand. After 5 minutes, the removal of phenol by Fe(VI)-coated sand was 51%, but only 37% by the IGFeCU powder. This accelerated treatment by Fe(VI)-coated sand could lead to rapid degradation of organic contaminants which has economic benefits for water treatment plants.

[0148] FIGURES 9C and 9D show higher aqueous Fe(VI) concentrations of 5.76- 9.77 mg / L for the the Fe(VI)-coated sand compared to 0.28-1.87 mg / L for the IGFeC powder, which could explain the enhanced treatment of phenol by Fe(VI)-coated sand. A faster decay was observed of aqueous Fe(VI) for the feFeCh powder (3.79 mg-iL-ihr1) compared to the Fe(VI)-coated sand (0.35 mg-JL^hr1).

[0149] The slower decay of Fe(VI) in the Fe(VI)-coated sand can indicate more Fe(VI) available in solution for longer periods of time, suggesting that more organic compounds could be treated simultaneously by the Fe(VI)-coated sand. The slower Fe(VI) decay in the Fe(VI)-coated sand system also confirms the S1O2 stabilization effect on Fe(VI) reactivity’. Furthermore, reduced decay rates of aqueous Fe(VI) also generate low er quantities of Fe(III) particles in solution which could decrease the frequency for Fe(III) sludge disposal post-treatment. The removal of phenol by Fe(VI)-coated sand can be threefold: (i) removal in the aqueous phase, (ii) sorption / coagulation with Fe(III) solids, and (iii) removal on the sand surface.

[0150] FIGURES 10A and 10B are graphs showing that Fe(VI)-coated sand had greater reactivity towards phenol in the presence of PMSO which can indicate an increased presence of reactive species. The removal capacity' of Fe(VI)-coated sand for phenol and PMSO was assessed using different concentrations of the organic compounds (i.e., 283 pg / L phenol and 865 pg / L PMSO; 245 pg / L phenol and 394 pg / L PMSO; and, 520 pg / L phenol and 739 pg / L PMSO). In the absence of PMSO, phenol removal by Fe(VI)-coated sand was estimated at 51% within 5 min (see FIGURE 9B), whereas in the presence of PMSO, the removal efficiency was 80-97%.

[0151] As a result of the reaction between the Fe(VI)-coated sand and PMSO. reactive species Fe(V) and Fe(IV) will increase due to their production from Fe(VI) selfdecay and Fe(VI) reaction with PMSO thereby increasing phenol removal. In multipollutants systems, the combination of greater Fe(VI) reactivity' promoted by SiO2 andFe(V) / Fe(IV) production from Fe(VI) reactions could result in more effective treatment than in aqueous K2FeO4 powder systems.

[0152] FIGURES 11 A and 1 IB are SEM images of non-coated Ottawa sand and FIGURES 11C and 11D are SEM images of Fe(VI)-coated sand of the disclosure. The SEM images indicate that the Fe(VI) coating alters the surface morphology of the Ottawa sand. The surface roughness of the non-coated Ottawa sand increased following the TeOS and Fe(VI) coating.

[0153] Elemental analysis of the surface composition indicated mostly Si (32.5%) and O (54.5%) for the unmodified Ottawa sand. The carbon detected on the Ottawa sand can be attributed to the carbon coating sample preparation done prior to analysis to reduce electrical charge on the non-conductive sand samples. On the Fe(VI)-coated sand surface, 33.7% K, 1%C1, and 1.7% Fe were detected confirming the successful coating of the potassium ferrate (K2FeO4).

[0154] The efficacy of the Fe(VI)-coated sand was evaluated in multiple contaminant systems and at different pH values of 7.5 and 9. These pH values were chosen to assess the Fe(VI)-coated sand reactivity when its aqueous stability is high (i.e., at pH 9) and at environmentally relevant pH (i.e., pH 7.5). Batch kinetics experiments were conducted in four different phases: (i) all trace organics in a pH 9, 10 mM sodium borate buffer solution (the “09 system”); (ii) all trace metals in a pH 9, 10 mM sodium borate buffer solution (the “M9 system”); (iii) trace organics and metals together in a pH 9, 10 mM sodium borate buffer solution (the “MO9 system”); and, (iv) trace organics and metals together in a pH 7.5, 10 mM sodium borate buffer solution (the “MO7.5 system”).

[0155] In-situ formation of Fe(III) can enhance the removal of trace metals. The Fe(VI)-coated sand exhibited lower reactivity7and removal efficiency toward the trace metals compared to trace organics. Furthermore, the reactivity toward Pb was greater than that of Cu and Zn. The batch adsorption results shown in FIGURES 12A, 12B, 12C andFIGURES 13B, 13D suggest that the trace metals are removed via interaction with Fe(III) particles generated during the reduction of leached Fe(VI) in the reaction solution. For example, 100% removal of Pb and 94% removal of Zn (FIGURE 13C) were observed after the 3 h reaction in the test evaluating Fe(III) removal capacity (i.e., Fe(III) solids only), whereas the Fe(VI)-coated sand treatment in the MO9 system only yielded 61% removal of Pb and 28% for Zn after 3 h reaction (FIGURE 12B). Additionally, the removal of Pb and Zn by Fe(VI)-coated sand was achieved at 23% and 26% in the M9 system in the absence of trace organics (FIGURE 12A). These data suggest that Fe(III) phases formed as a result of oxidation of trace organics and subsequent Fe(VI) reduction can increase Pb and Zn removal. At pH 9, Fe(VI) is stable and reacts slowly with water to form Fe(III), but this reduction can be accelerated in the presence of organic compounds reacting with and reducing Fe(VI).

[0156] Analysis with a chemical equilibrium model, such as Visual MINTEQ®, suggests that Pb removal is governed by its chemical speciation in solution. In the pH 9, 10 mM borate buffer, Visual MINTEQ® analysis indicates that Pb(OH)2is oversaturated in solution which could contribute to precipitate formation. In the M9 control samples (i.e.. no Fe(VI)-coated sand), the removal of Pb after 3 hours was 1.6 times greater than in the M9 system. Thus, the removal of Pb within the pH 9, 10 mM borate buffer system can be predominantly facilitated by sample filtration of precipitates prior to ICP-MS measurements. The processes governing trace metals removal in treatment systems could be three-fold: (1) removal via filtration of solid phase precipitates formed due to oversaturation; (2) sorption to aqueous Fe(III) phases generated during reduction of leached aqueous Fe(VI); and, (3) sorption onto the Fe-coated sand surface.

[0157] Referring to FIGURES 12A, 12B, 12C show that trace metals removal by the Fe(VI)-coated sand decreased as pH decreased, especially in the case of Zn. In the MO7.5 system, the removal efficiencies of Zn and Pb decreased by 7 and 14% comparedto removal in the MO9 system. The isoelectric point of Fe(III) (hydr)oxide species is between pH 7 and 8.5; thus at pH 9, the removal of Pb can be driven by electrostatic interactions of the abundant Pb(OH)+species and the negatively charged Fe(III) (hydr)oxide surfaces. Furthermore, at pH 9. Fe(VI) exists predominantly as FeO42', which could also interact electrostatically with Pb(OH)+species. In the case of Zn, the abundant species at pH 9 is Zn(0H)2 and removal can occur through physical sorption of Zn either on the Fe(VI)-coated sand surface or within Fe(III) (hydr)oxide lattices. Conversely, at pH 7.5, Pb2+and Zn2+are the more abundant species and may sorb weakly to the neutral Fe(III) (hydr)oxides surface. The pH effect on metal removal in the Fe(VI)-coated sand treatment systems is also mirrored in the Fe(III) reaction systems shown in FIGURE 13C and 13D. After the 3-hr reaction with Fe(III), the removal of Zn increased from 31% at pH 7.5 to 94% at pH 9.

[0158] FIGURES 14A, 14B, 14C, 14D show that Cu removal was greater in the control experiments absent Fe(VI)-coated sand, regardless of solution pH. Visual MINTEQ® analysis reports CuO and Cu(OH)2 as the oversaturated mineral phases present in solution, thus the high removal efficiencies observed in the control samples could be attributed to the formation of these mineral phases which were removed during filtration. Furthermore, greater Cu removal efficiencies were achieved in the MO7.5 and MO9 control systems. For example, the presence of trace organics in the MO9 control system led to a 58% increase in Cu removal which suggests that Cu can be interacting with the trace organics.

[0159] The Fe(VI)-coated sand exhibited a greater oxidation potential towards ACM and SMX compared to BZT. FIGURES 15, 16, and 17 indicate the oxidation of the three select trace organics by the Fe(VI)-coated sand. For all of the test reaction systems, the degradation of ACM was complete and occurred rapidly (within 15 min). Oxidation efficiencies of 100% were achieved for SMX in the 09 (FIGURE 15) and MO7.5 reactionsystems (FIGURE 17) and 90% oxidation in the MO9 system (FIGURE 16) after the 3-hr reaction. For BZT, the oxidation efficiency was 37% in the 09 system (FIGURE 15), but no removal was detected in the M09 and MO7.5 systems (FIGURES 16, 17). The greater removal of ACM and SMX can be attributed to the high Fe(VI) selectivity’ towards electron-donating moieties such as phenols (present in ACM) and anilines (present in SMX).

[0160] The solution matrix and pH can influence the oxidation potential of ACM and SMX by the Fe(VI)-coated sand. The presence of trace metals in the MO9 system led to a 26% decrease in SMX oxidation capacity within 5 min of reaction compared to oxidation in the 09 system (i.e., absence of trace metals) as seen in FIGURES 15A and 16A. The SMX oxidation capacity increased from 21% at pH 9 (FIGURE 16A, MO9 system) to 100% at pH 7.5 (FIGURE 17A, MO7.5 system) within 5 min of reaction.

[0161] This difference can be explained by the differences in Fe(VI) chemical speciation at pH 7.5 compared to pH 9. At pH 7.5, Fe(VI) is comprised of 38.7% HFeOT and 61.3% FeO42'. HFeOT species can have a higher oxidation potential than FeO42' species which may result in greater degradation of ACM and SMX at pH 7.5. At pH 9, the degradation of the trace organics decreased as seen in FIGURE 16A which could be due to three effects: (1) the less reactive FeO4’ species is dominant at pH of 9 (i.e., 98%); (2) the presence of more contaminants in solution result in greater competition for reactions with Fe(VI); and, (3) Fe(VI) decays to intermediate and Fe(III) phases faster when there are more contaminants present.

[0162] Fe(VI) can decay faster in the MO9 and MO7.5 systems containing all contaminants compared to the systems containing one type of contaminant. To enhance the decomposition of trace organics during wastewater treatment with more complex matrices containing multiple contaminant types, higher doses of Fe(VI)-coated sand or higher Fe(VI) mass loadings on the sand surface may be required. However, within a 3-hr reactionperiod, removal efficiencies of 90% or greater were still achieved for ACM and SMX despite the mass of contaminants present.

[0163] BZT complexation with Cu can inhibit BZT treatment by the Fe(VI)- coated sand. BZT is used as a corrosion inhibitor for Cu and can form metal complexes with Cu+and Cu2+through electron transfer between the BZT nitrogen atoms. However, the presence of Cu did not enhance BZT degradation (FIGURES 16-17). In the 09 system, FIGURE 15 shows up to 37% removal of BZT after 3 hours of reaction; however, in the MO9 and MO7.5 systems containing metals, FIGURES 16 and 17 show an artificial increase in the measured aqueous BZT concentrations. The increase was higher for the pH 7.5 condition after 2 hours of reaction. The reaction between the Cu-BZT complexes and the Fe(VI)-coated sand can lead to the decomplexation of the Cu-BZT and the release of aqueous Cu and BZT into solution. While the decomplexation of the Cu-BZT complex was observed by the increase in Cu-BZT concentration, the free BZT did not react further with Fe(VI), which could be due to the lesser Fe(VI) affinity towards BZT, which was observed in FIGURE 15.

[0164] A synthetic wastewater effluent solution (SWW) was made using sodium bicarbonate (NaHCOg), sodium chloride (NaCl), sodium phosphate dibasic heptahydrate (Na2HPO4’7H2O), magnesium chloride hexahydrate (MgC12 6H2O), magnesium nitrate hexahydrate (Mg(NO3)2'6H2O), calcium chloride dihydrate (CaC12 2H2O), and calcium nitrate tetrahydrate (Ca(NO3)2 4H2O). The composition is given in Example 11.

[0165] Trace organic oxidation by Fe(VI)-coated sand is lessened in the synthetic wastewater (SWW) reaction system. Referring to FIGURE 18 A, after 3 hours of reaction with the Fe(VI)-coated sand, only 7.24% removal of SMX was achieved. While the oxidation efficiency of ACM remained high at 98.4%, the degradation was slower in SWW compared to degradation in the borate buffer solutions seen in FIGUERS 15-17. Oxidation of BZT in the SWW was minimal, and an artificial increase in the aqueous BZTconcentration was observed during the reaction period. The divalent cations in the SWW can impede ferrate oxidation. In the SWW treatment system, Fe(VI) has predominantly FeO i2-ions (83.4%); thus, the Ca2+and Mg2+ions present may react with FeO42'to catalyze Fe(VI) decomposition and decrease the oxidation of ACM and SMX.

[0166] Conversely, the SWW constituents enhanced trace metal removal by the Fe(VI)-coated sand. Referring to FIGURE 18B, greater (>94%) and faster (within 5 min of reaction) removal efficiencies were recorded for all three trace metals in the SWW reaction system compared to the treatment systems in borate buffer. While the removal of Cu and Pb can be partially attributed to the removal of solid phases through filtration, the removal of Zn is completely achieved by the Fe(VI)-coated sand.

[0167] Referring to FIGURE 13D. in the SWW control samples in the absence of Fe(VI)-coated sand, Zn removal did not occur; however, the presence of the Fe(VI)-coated sand led to a 94.7% removal of Zn in SWW as seen in FIGURE 18B. Therefore, while the self-decomposition of Fe(VI) by the Ca2+and Mg2+ions hindered transformation of trace organics within the SWW matrix, the faster generation of Fe(III) species in solution promoted trace metals removal. However, the effect of Ca2+and Mg2+might be limited to interferences with oxidative processes in the treatment systems.

[0168] The decreased oxidation efficiency of trace organics coupled with the enhanced removal of trace metals in the SWW matrix suggest a hierarchy in Fe(VI) reactivity toward contaminants and co-existing ions. The significant difference in ACM and SMX oxidation efficiencies in the SWW matrix (91%) compared to the difference in the oxidative removal of ACM and SMX in the MO9 (10%) and MO7.5 (no difference) systems demonstrates preferential affinity of the Fe(VI)-coated sand for ACM. Furthermore, the diminished oxidation of SMX and BZT in the SWW matrix indicates that Fe(VI) favorably reacts with hydrophilic and protonated ACM, divalent cations, and watermolecules in the SWW system. Additionally, these three interactions boost formation of Fe(III) phases to significantly improve trace metals removal.

[0169] Batch experiments were conducted under synthetic wastewater effluent (SWE) conditions to evaluate the effects of synthetic effluent organic matter (sEfOM) in a more representative matrix. Approximately 100 mg of the Fe(VI)-coated sand was added to a 50 mL test tube containing nominally 50 pg / L each of ACM, PHE, SMX, Cu, Pb and Zn and 10 mg-C / L of sEfOM in the SWE solution. The sEfOM included: 2.5 mg-C / L BSA, 2 mg-C / L ALG, 0.5 mg-C / L OA, and 5 mg-C / L HA to represent the protein, carbohydrate, fat. and humic fractions typical of EfOM, respectively. Synthetic wastewater effluent (SWE) solution includes the composition given in Example 12.

[0170] The effluent organic matter can enhance degradation of trace organics with the Fe(VI) coated sand. Referring to FIGURE 19A, in a 10 mM Na2B4O?pH 9 buffer, 79.4% of PHE was degraded after 5 min of reaction compared to only 51% degradation without sEfOM.

[0171] Further, referring still to FIGURE 19A, control experiments in the absence of Fe(VI)-coated sand indicate negligible interactions of PHE with sEfOM. Additionally, referring to FIGURE 20 A, 12% of SMX was removed by the Fe(VI)-coated sand whereas 7.2% of SMX was removed in the same SWE matrix without sEfOM.

[0172] As described above, low SMX removal efficiency was attributed to the presence of multiple contaminants and SWE constituents lowering aqueous Fe(VI) availability and limiting Fe(VI) oxidation capacity. Despite the addition of sEfOM, the removal of SMX was enhanced. Referring to FIGURE 20 A, a lOx lower initial SMX concentration (50 pg / L) was employed compared to 500 pg / L used for FIGURE 18. The enhanced SMX degradation with sEfOM could be due to the: (1) increased mass ratio of Fe(VI) to contaminants; or, (2) sEfOM reactions with Fe(VI) generating more reactivespecies. The phenolic moieties in HA and ALG in the sEfOM may enhance Fe(VI) reactivity toward the trace organics.

[0173] The bovine serum albumen limits and alginate promotes Fe(VI)-coated sand reactivity. BSA interactions with Fe(VI)-coated sand can impede degradation of trace organics. Referring to FIGURES 21A, 21B, 21C, 21D, SMX degradation within 15 min of reaction was 6.4%, 20%, 32% and 37% in the BSA-, HA-, ALG-, and OA-only systems, respectively.

[0174] Fe(VI) reactivity can be influenced by sEfOM composition. FIGURE 21 A indicates that BSA decreases Fe(VI)-coated sand reactivity toward SMX and PHE. Referring to FIGURE 20 A, 12% SMX and 75% PHE removal was observed after the 1-hr. reaction period in the presence of all sEfOM components; however, when only BSA was present, the removal efficiencies for SMX and PHE in the same 1-h period were 9.2% and 79% respectively.

[0175] Referring to FIGURE 21B and 12D, when HA or OA were used as sEfOM components, 30% SMX and 100% PHE was removed. When only ALG was used, 100% degradation of both SMX and PHE were observed from FIGURE 21C. Comparable results from tests using all sEfOM components and BSA only suggests that BSA may govern Fe(VI)-coated sand reactivity. Referring to FIGURE 22C, control experiments conducted without the Fe(VI)-coated sand and with sEfOM showed no removal of any trace organics; thus, the reduced removal of SMX and PHE may be due to interactions between BSA and the Fe(VI)-coated sand as opposed to interactions between BSA and contaminants.

[0176] ACM degradation by the Fe(VI)-coated sand was independent of the sEFOM composition. 100% degradation of ACM was attained within 15 min of reaction in all treatment systems explored as seen in FIGURES 20 and 21. Referring to FIGURES 22A and 22C, control experiments showed no ACM removal in the absence of media indicating that ACM does not react with the sEfOM components nor with the trace metalspresent in the reaction systems. The highly effective removal of ACM may result from the presence of more electron-donating moieties (i.e., phenol and amine) in its structure which may promote faster reactions with Fe(VI). There is rapid ACM degradation independent of the solution matrix (i.e., pH, mono- and divalent cations). While PHE is also an electrondonating compound, its removal was less than that of ACM as seen in FIGURES 20 and 21.

[0177] The complexation of trace metals to sEfOM drives removal. The removal of trace metals can occur via: (i) sorption to sEfOM components; (ii) precipitation of mineral phases (e.g.. CuO(S)); (iii) sorption to the Fe(VI)-coated sand; and (iv) sorption to Fe(III) phases formed from Fe(VI) decomposition. High removal of trace metals by Fe(VI)- coated sand at alkaline pH (i.e. pH 8 and 9) can be due to precipitation of metal hydroxide solids that are removed via fdtration. The solution pH in the SWE matrix prior to Fe(VI)- coated sand addition was 8. Visual MINTEQ® analysis indicated that Cu and Pb mineral phases (e.g., CuO(s), Pbs(PO4)3Cl(s)) are oversaturated in solution. After 1 h of reaction with the Fe(VI)-coated sand, Fe(VI) dissolution caused the solution pH to increase to 1 1.0 which promotes the formation of metal precipitates. These precipitates may be removed during filtration prior to ICP-MS analysis or via sorption to other solid phases (e.g., the Fe(VI)- coated sand, Fe(III) precipitates). At pH 11, Fe(VI) exists predominantly as the more chemically stable FeO-i2’ species. Thus, sorption to Fe(III) phases may be minor due to decreased decay of Fe(VI) at this pH value. Furthermore, sorption to the sand surface can contribute to the overall trace metals removal.

[0178] Removal of Pb by Fe(VI)-coated sand in the presence of sEfOM can be driven by its affinity to HA. However, an increase in Pb concentration and TOC can occur after adding Fe(VI)-coated sand to the reaction mixture. This phenomenon could be explained by a decoupling of the Pb-HA complexes after reaction with Fe(VI) which would artificially increase the measured aqueous Pb concentration.

[0179] Referring to FIGURES 23 A, 23B, 23C, 23D, the batch experiments with individual sEfOM suggest Cu forms stronger complexes with OA compared to BSA, HA, and ALG. Similar to Pb, Cu was not detected at time to in the HA-only system indicating an uptake of Cu by HA. The initial Cu concentration in the BSA-only and ALG-only systems were 14±1.0 pg / L and 13±0.5 pg / L. Cu was also not detected in the OA-only system, suggesting preferential affinity of Cu to OA and HA. After addition of the Fe(VI)- coated sand, ICP-MS analyses still detected no Cu in the OA-only system, whereas an increase in measured Cu concentration was observed in the HA-only (FIGURE 23B), BSA- only (FIGURE 23A) and ALG-only (FIGURE 23C) systems, and in the presence of all sEfOM components (FIGURE 20B). The dissolution of Cu complexes can result in an artificial increase of Cu concentration in solution as the reaction progresses. Greater than 50% removal of TOC was noticed in the BSA-only system. The dissolution of Cu and Pb could be due to structural changes of sEfOM which could lead to changes in the interactions between sEfOM and the trace metals.

[0180] All four sEfOM components contained Cu, Pb, and Zn in pg / L levels. Cu concentration increases artificially after reaction with the Fe(VI)-coated sand partly due to the release of inherent Cu bound to the sEfOM components — especially in the BSA-only and ALG-only systems. Conversely, no artificial concentration increase of Zn was observed as seen in FIGURES 21B and 23, although the leachate Zn content (73-157 pg / L) in the sEfOM components is greater than the Cu content (16-33 pg / L) suggesting that Cu complexes in wastewater effluent systems are more susceptible to interactions with the Fe(VI)-coated sand media. The measured Pb content (1.8-5.3 pg / L) in the sEfOM components was significantly lower than that of Cu and Zn. Hence, additional treatment processes may be needed for Cu removal in water treatment applications of Fe(VI)-coated sand.

[0181] Example 1 (Synthesis of Fe(VI)-coated sand)

[0182] The Fe(VI)-coated sand was synthesized by adding sand to a solution of potassium ferrate. First, the sand (for example, ‘‘Ottawa sand” having 30-40 mesh, greater than 90% by weight SiO2) was washed with 1 M HNOs for 24 hours and rinsed with deionized water until the pH of the rinse solution was within pH 6-8. The washed sand was then dried at 105 °C for 24 hours in an oven. To promote binding of ferrate to the sand surface, 15 mL of TeOS was added to 30 g of pre-washed sand, mixed for 3 hours, and dried at 105 °C for 24 hours in the oven. The TeOS modified sand, designated as TeOS- sand, was added to the potassium ferrate (t FeOj) solution. Another TeOS-sand was also synthesized by mixing the TeOS (15 mL) and cleaned sand (30 g) for 24 hours before drying. The K.2FeO4 solution was prepared via a wet oxidation process. A suitable method can be found in Guan et al. (W. Guan. Z. Xie and J. Zhang. J. Spec! rose. 2014. 2014, 1-8). A saturated solution of 13 M KOH was prepared, chilled, and stored at 4 °C throughout the synthesis to maintain cold temperature conditions. Approximately 15 g of Ca(OCl)2 was added to 25 mL of the saturated KOH solution, then the mixture was stirred for 30-60 min and filtered to obtain a yellow solution of potassium hypochlorite. An additional 20 mL of the saturated KOH solution was added to the yellow filtrate and the mixture was placed in an ice bath for 20-30 min to precipitate potassium chloride. The potassium chloride suspension was further filtered, then 8 g of pulverized ferric nitrate was added in small portions (about 0.50 g / min) for 15 min to the filtrate solution under cooling conditions (4 °C) to form IGFeO-i. A recirculating chiller was used to maintain the temperature of the potassium ferrate throughout the synthesis. The generated solution of potassium ferrate was stirred for an hour before the addition of 50 mL of saturated KOH. The solution was vigorously stirred at 500 rpm for 5 min and left to stand for 30 min. Next, 25 g of the TeOS- sand was added to the K2FeO4 solution and stirred for 24 hours at 4 °C to allow the Fe(VI) to coat the sand surface. The K2FeO4 supernatant was decanted, and the synthesized Fe(VI)- coated sand was centrifuged at 4000 rpm for 10 min to remove the excess solution beforebeing dried in a vacuum oven for more than 24 hours. The Fe(VI)-coated sand was stored under vacuum when not in use to limit exposure to air and prevent ferrate decomposition.

[0183] Example 2 (Detection of Fe(VI) on the media surface)

[0184] In an alkaline solution, Fe(VI) has an absorption peak at 510 nm. The presence of the Fe(VI) on the Fe(VI)-coated sand surface was determined via UV-Vis spectroscopy. The Fe(VI)-coated sand was placed in a 5 mM Na2HPO4 / l mM Na2B4O? solution (pH 9.25) and sonicated for 5 min to desorb Fe(VI) from the coated sand surface for direct UV-Vis measurement of the Fe(VI) leachate. The leachate solution was reacted with ABTS (2,2'-azinobis-(3-ehtylbenzothiazoline-6-sulfonate) to measure the absorbance corresponding to the formation of an ABTS+radical at 415 nm.

[0185] Example 3 (Fe coating density on the media surface)

[0186] The total Fe mass coated on the sand was measured via inductively coupled plasma orbital emission spectrometry (ICP-OES) using an Inductively Coupled Plasma-Optical Emission Spectrophotometer (ICP-OES). The Fe(VI)-coated sand was placed in a 1% HNO- solution and sonicated for 5 min to leach all the Fe coating. The leachate was further diluted with the 1% HNOs solution before ICP-OES analysis.

[0187] Example 4 (Aqueous stability of the Fe(VI) coating on the sand surface)

[0188] Batch experiments were conducted to evaluate the aqueous stability of the Fe(VI)-coated sand and the desorption of Fe(VI) from the media surface. Approximately 50 mg of Fe(VI)-coated sand was added to 50 mL of 10 mM Na2HPO4 / NaH2PO4 or 10 mM Na2B4O? buffer and stirred at 40 rpm. The buffer solutions were adjusted to pH 7, 8, 9 using HC1 or NaOH to determine the effects of solution pH on Fe(VI) stability. At designated time intervals, aliquots of the samples were filtered using 0.2 pm, 25 mm diameter cellulose acetate syringe filters. Aqueous concentrations of Fe(VI) were determined using the ABTS method and aqueous total Fe using ICP-OES. Tests revealed that Fe(VI) and Fe(III) were the dominant Fe species in solution when the Fe(VI)-coated sand was placed in bufferedsolutions (pH 9); thus, aqueous Fe(III) concentrations were calculated as the difference between the measured total Fe and Fe(VI). The results are shown in FIGURES 4 and 5. The aqueous stability of Fe(VI) in the absence of silica stabilization was also assessed for comparison with the Fe(VI)-coated sand. A stock solution of FUFeCU powder was diluted to approximately 21 mg / L in 10 mM Na2B4Ch buffer at pH 9 and stirred at 40 rpm. At designated times, a 1 mL aliquot was taken and filtered using 0.2 pm, 25 mm diameter cellulose acetate syringe filters, then residual Fe(VI) concentrations were determined using the ABTS method. Results are shown in FIGURE 6A.

[0189] Example 5 (Fe(VI)-coated sand media storage stability)

[0190] Total Fe and aqueous Fe(VI) measurements were taken at designated time intervals (t = 1, 3. 5, 7, and 11 days) after Fe(VI)-coated sand production to quantify Fe coating on the sand surface and to assess the media stability during storage. At each sampling time, approximately 3 g / L of Fe(VI)-coated sand was removed from the vacuum oven and placed in a 5 mM NazHPO-i / 1 mM Na2B4O7 solution (pH 9.25) and sonicated for 5 min to desorb Fe(VI) from the coated sand surface. The leachate solution was then reacted with ABTS to determine the aqueous Fe(VI) concentration. The same coated sand dose (3 g / L) was simultaneously measured and placed in a 1% v / v HNCh solution and sonicated for 5 min before total Fe measurements. Results are shown in FIGURE 7.

[0191] Example 6 (Phenol removal experiments)

[0192] Batch experiments to evaluate the Fe(VI)-coated sand media capacity for phenol treatment were conducted in 10 mM Na2B4O? buffer at pH 9 in media bottles wrapped ith aluminum foil to maintain dark conditions. The effect of Fe(VI)-coated sand dose on phenol removal was determined to identify the optimal media dose for water treatment. Different amounts (i.e., 22.8±1.1, 42.6±0.8, and 80.7±1.0 mg) of Fe(VI)-coated sand were added to 20 mL solutions of 10 mM Na2B4O? containing phenol (236±0.6 pg / L) to obtain media doses of 1, 2, and 4 g / L. The mixtures were shaken for 30 min at 40 rpm.Then, a 2 mL aliquot was quenched with 20 pL of 500 mM Na?SCh to stop the reaction between Fe(VI) and phenol. The mixture was filtered with a 0.2 pm, 25 mm diameter cellulose acetate syringe filter to measure residual phenol using high performance liquid chromatography (HPLC) methods. Results are shown in FIGURE 8.

[0193] Example 7 (Removal kinetics experiments)

[0194] Removal kinetics experiments were initiated by adding approximately 200 mg of Fe(VI)-coated sand to 100 mL of a 10 mM Na2B40v buffer solution containing phenol. At designated time intervals, an aliquot of 2 mL was sampled and pretreated as above before HPLC analysis. An additional aliquot of 1 mL was taken simultaneously to measure aqueous Fe(VI) concentration by the ABTS method. Another 1 mL aliquot was further diluted with a 10 mM Na2B4O? buffer solution and quenched with HNOs (trace metals grade) to measure total aqueous Fe by ICP-OES. A 4 mL aliquot was also taken and filtered with a 0.2 pm, 25 mm diameter cellulose acetate syringe filter for UV-Vis scanning between 200-650 nm for detection of oxidation products with absorbances outside of the range of the HPLC diode array detector. Results are show n in FIGURE 9B.

[0195] The removal of phenol by Fe(VI) powder was also investigated to compare the performance of the Fe(VI)-coated sand media against Fe(VI) powder in the absence of silica stabilization. Fe(VI) stock solution (i.e., in the absence of sand) was freshly prepared by diluting approximately 12.6 mg / L of K.2FeO4 powder in 10 mM Na2B4O? buffer. The stock solution was used within 15 min of preparation to minimize Fe(VI) self-decay. 10 mL of the stock solution was added to 90 mL of a 10 mM Na2B4O? buffer solution containing phenol to initiate phenol removal. Results are sho n in FIGURE 9A.

[0196] Example 8 (Evaluation of Fe(VI)-coated sand oxidation mechanisms)

[0197] To assess the media reactivity toward multiple organic compounds and probe oxidation mechanisms, phenol removal by Fe(VI)-coated sand was assessed in thepresence of PMSO. Fe(VI)-coated sand (2 g / L) was added to pH 9 borate buffer solutions containing PMSO and phenol at different concentrations (250 pg / L or 500 pg / L phenol and 400 pg / L or 800 pg / L PMSO). Aliquots were sampled and analyzed as described above. HPLC samples were analyzed for phenol, PMSO and PMSO2). Results are shown in FIGURES 10A and 10B.

[0198] Example 9 (Quantification of Fe(VI) purity)

[0199] The purity of Fe(VI) in the K2FeO4 powder was determined by measuring a K2FeO4 powder and dissolving in 5 mM Na2HPO4 / l mM Na2B4O? solution (pH 9.25). The Fe(VI) concentration was determined using the absorbance at 510 nm. This purity of Fe(VI) is then determined as the ratio of calculated Fe(VI) concentration to the theoretical measured K2FeO4 powder concentration. The purity of Fe(VI) in the K2FeO4 was estimated at approximately 88%. The purity of Fe(VI) in the Fe(VI)-coated sand was also evaluated. This was achieved by taking an aliquot of K2FeO4 slurry obtained prior to sand addition and freeze-drying it. The dry product obtained was then used as K2FeO4 powder for purity calculation and the Fe(VI) purity was estimated at 8-9%.

[0200] Example 10 (Removal of Trace Metals and Organics in Ultrapure Water)

[0201] Batch experiments were conducted to evaluate the Fe(VI)-coated sand removal capacity of the contaminants in a pure water matrix containing only 10 mM sodium borate buffer. Stock solutions of each contaminant were prepared in Milli-Q water except for SMX, which was prepared in methanol. All experiments were conducted in triplicates and samples were shaken on a Fisherbrand™ multi-purpose tube rotator at 40 rpm.

[0202] The efficacy of the Fe(VI)-coated sand was evaluated in multiple contaminant systems and at different pH values (pH 7.5 and 9). These pH values were chosen to assess the Fe(VI)-coated sand reactivity7when its aqueous stability7is high (i.e., at pH 9) and at environmentally relevant pH (i.e., pH 7.5). Batch kinetics experiments were conducted in four different reaction systems: (i) all three trace organics in a pH 9, 10 mMsodium borate buffer solution (09 system); (ii) all three trace metals in a pH 9, 10 mM sodium borate buffer solution (M9 system); (iii) trace organics and metals together in a pH 9, 10 mM sodium borate buffer solution (MO9 system); and, (iv) trace organics and metals together in a pH 7.5, 10 mM sodium borate buffer solution (MO7.5 system). The concentration of the contaminants was targeted at 500 pg / L each, and the dose of the Fe(VI)-coated sand was 2 g / L for all reaction systems. At designated time intervals, a 2 mL aliquot of samples containing the organic compounds was quenched with 20 pL of 500 mM Na2SCh to stop the reaction between Fe(VI) and the organic compounds, then filtered with a 0.2 pm. 25 mm diameter cellulose acetate syringe filter before analysis using high performance liquid chromatography (HPLC) methods. Liquid chromatography-mass spectrometry (LC-MS) grade methanol (500 pL) was added to 500 pL of the quenched and filtered aliquot for high-resolution mass spectrometry (HRMS) analyses to determine transformation products of the organic compounds. For all samples, a 3 mL aliquot was taken and filtered with a 0.2 pm, 25 mm diameter cellulose acetate syringe filter, and then 1 mL of the aliquot was used to measure the aqueous Fe(VI) concentration via the 2,2'- azinobis(3-ehtylbenzothiazoline-6-sulfonate) (ABTS) colorimetric method via UV-vis spectroscopy using a Shimadzu UV-2700 spectrophotometer. The remaining aliquot was diluted with a 10 mM sodium borate buffer solution and acidified to 2% trace metal grade nitric acid for inductively coupled plasma orbital mass spectrometry (ICP-MS) analysis using a PerkinElmer Nexion 2000B inductively coupled mass spectrometer.

[0203] Control experiments in the absence of the Fe(VI)-coated sand were conducted to assess the stability and reactivity of the trace metals and organics in solution for all four reaction systems. In addition, the role of Fe(III) phases in the Fe(VI)-coated sand reactivity was evaluated. A weighted amount (1.3 ± 0.1 mg) of Fe(NO3)3• 9H2O was added to 50 mL of either apH 9, 10 mM sodium borate buffer solution or apH 7.5, 10 mM sodium borate buffer solution containing all the trace metals and trace organics. The finalFe(III) concentration (26 ± 1.8 mg / L) in solution was chosen as an overestimate of the total Fe concentration (12.6 ± 5.1 mg / L) possible in solution if all of the Fe were to leach from the sand surface. At designated times, aliquots were taken and filtered prior to ICP-MS and HPLC analyses.

[0204] Example 11 (Removal of Trace Metals and Organics in a Synthetic Wastewater Effluent Matrix)

[0205] Batch kinetics experiments were also conducted under synthetic wastewater (SWW) effluent conditions to characterize the effects of the wastewater effluent matrix on the Fe(VI)-coated sand treatment capacity for the select trace contaminants. The synthetic wastewater (SWW) composition included: NaHCCh (96 mg / L). NaCl (83 mg / L), MgCh 6H2O (19 mg / L), Mg(NO3)2-6H2O (10 mg / L), CaCh 2H2O (89 mg / L), Ca(NOs)24H2O (10 mg / L), and Na2HPO4 (1 mg / L). Batch experiments were conducted by adding approximately 100 mg of Fe(VI)-coated sand in 50 mL of SWW in 50 mL polypropylene centrifuge tubes containing nominally 500 / zg / L of ACM, BZT, SMX, Cu, Pb, and Zn each. At designated time intervals, aliquots were sampled and analyzed.

[0206] Example 12 (Treatment of Trace Metals and Organics in the Presence of Synthetic Effluent Organic Matter)

[0207] Batch experiments were conducted under synthetic wastewater effluent (SWE) conditions to evaluate the effects of synthetic effluent organic matter (sEfOM) in a more representative matrix. Approximately 100 mg of the Fe(VI)-coated sand was added to a 50 mL test tube containing nominally 50 pg / L each of ACM, PHE, SMX, Cu, Pb and Zn and 10 mg-C / L of sEfOM in the SWE solution. The sEfOM included: 2.5 mg-C / L BSA. 2 mg-C / L ALG, 0.5 mg-C / L OA, and 5 mg-C / L HA to represent the protein, carbohydrate, fat, and humic fractions typical of EfOM, respectively.

[0208] Table 1. Composition of the synthetic wastewater effluent solution

[0209] >Component Concentration UnitCa2+26Mg213Na+58.8CF 100 mg / LHCCE 70NO3‘ 10PO43’ 0.3 pH 8.0±0.1 S.U.

[0210] At designated time intervals, a 4-rnL aliquot was collected and quenched with 100 pL of 500 mM Na^SO? to stop the reaction between Fe(VI) and the organic compounds, then filtered with a 0.2 pm, 25 mm diameter cellulose acetate syringe filter before trace organics analyses (500 pL of filtrate) and trace organic carbon (TOC) analyses (1.5 mL of filtrate diluted 6 times with ultrapure water). Another 500 pL of the filtrate was diluted and acidified to 2% nitric acid for trace metals analyses. Additionally, 1 mL aliquot of the reaction solution was taken for aqueous Fe(VI) concentration analysis. To probe the effect of each sEfOM component on Fe(VI) reactivity, batch experiments with the same initial conditions described above were performed using single sEfOM components at 10 mg-C / L. Control experiments in the absence of Fe(VI)-coated sand were conducted to determine interactions between the select contaminants and the sEfOM. Additional control experiments in the absence of both Fe(VI)-coated sand and sEfOM were also conducted to determine the stability of the trace contaminants in solution. All experiments wereconducted in triplicate using ultrapure water (resistivity: 18.2 MQ-cm). Results are shown in FIGURES 19-23.

[0211] Example 13 (Removal of Phenol in the Presence of Synthetic Effluent Organic Matter)

[0212] Approximately 100 mg of Fe(VI)-coated sand was added to 50 mL of ultrapure water buffered with 10 mM Na2B4O? at pH 9 containing roughly 250 ug / L of PHE and 10 mg-C / L of synthetic EfOM (2.5 mg-C / L BSA, 2 mg-C / L ALG, 0.5 mg-C / L OA, and 5 mg-C / L HA in 50-mL polypropylene centrifuge tubes. At designated time intervals, a 2-mL aliquot was quenched with 20 pL of 500 mM Na2SOs to stop the reaction between Fe(VI) and PHE, then filtered with a 0.2 pm, 25 mm diameter cellulose acetate syringe filter before analysis using high performance liquid chromatography (HPLC) with a diode array detector. At each time, another 4-mL aliquot was collected, filtered, then reserved for further analyses: (i) 1 mL was used for aqueous Fe(VI) concentration analysis via the 2,2’-azinobis-(3-ehtylbenzothiazoline-6-sulfonate) (ABTS) colorimetric method using a Shimadzu UV-2700 spectrophotometer; and (ii) 2 mL were diluted 4.5 times with ultrapure water for total organic carbon measurements using a Shimadzu TOC-L analyzer.

[0213] While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

CLAIMSThe embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Ferrate-coated sand, comprising: sand particles, wherein the sand particles comprise at least 50% silica; a coating of silicate groups on an exterior of the sand particles; and ferrate(VI) ions [FeO^2-bonded to the coating, wherein a surface composition of the ferrate-coated sand particles comprises at least 1 wt % of Fe.

2. The ferrate-coated sand of claim 1, wherein the surface composition comprises up to 6.5 wt.% of Fe.

3. The ferrate-coated sand of claim 1, wherein a balance of the surface composition comprises Si, O, K, and unavoidable impurities.

4. The ferrate-coated sand of claim 3, wherein the surface composition comprises from 3.6 wt.% to 40.8 wt.% of Si. from 36.4 wt.% to 57 wt.% of O, and from 1.8 wt.% to 53.5 wt.% of K, and the unavoidable impurities include at least Cl.

5. The ferrate-coated sand of claim 1, wherein the silicate groups comprise orthosilicate groups.

6. The ferrate-coated sand of claim 1, wherein the sand particles comprise greater than 90% by weight silica (SiO2).

7. A water treatment media comprising the ferrate-coated sand of any one of claims 1 to 6.

8. A method of making ferrate-coated sand, comprising:mixing sand in tetraethyl orthosilicate to form silicate-coated sand, followed by drying the silicate-coated sand; adding the dried silicate-coated sand to a solution of potassium ferrate; allowing ferrate(VI) ions to bind to the coating; and separating the excess solution of potassium ferrate.

9. The method of making ferrate(VI)-coated sand of claim 8, comprising: adding from 0.4 ml to 0.6 ml of tetraethyl orthosilicate per gram of sand.

10. The method of making ferrate(VI)-coated sand of claim 9, comprising: adding from 25 to 26 grams of the silicate-coated sand per 100 ml of potassium ferrate solution.

11. A method of treating wastewater, comprising: treating the wastewater containing a contaminant with a ferrate(VI)-coated sand of any of claims 1-6.

12. The method of claim 11. wherein the ferrate(VI)-coated sand is placed in a sand filtration unit.

13. The method of claim 11, wherein the ferrate(VI)-coated sand includes silicate groups on an exterior of the sand particles and ferrate(VI) ions [FeOJ2-bonded to the sand particles.

14. The method of claim 11, wherein the contaminant includes one or more of organic compounds and trace metals or a combination thereof.

15. The method of claim 14. wherein the organic compounds are selected from the group consisting of phenol, acetaminophen, benzotriazole, and sulfamethoxazole, or a combination thereof.

16. The method of claim 14, wherein the trace metals are selected from the group consisting of copper, lead, and zinc, or a combination thereof.

17. The method of claim 14, further comprising adding at least one compound selected from humic acid, bovine serum albumin, alginate, and octanoic acid.

18. The method of claim 14, further comprising treating for divalent cations before treating the wastewater with the ferrate (VI) coated sand.

19. The method of claim 14, further comprising treating the wastewater to adjust pH before treating the wastewater containing a contaminant with a ferrate (VI) coated sand.

20. A method of treating wastewater for a contaminant, comprising: adding at least one compound to the wastewater, wherein the at least one compound is selected from humic acid, bovine serum albumin, alginate, and octanoic acid or a combination thereof; and treating the wastewater with a ferrate(VI)-coated sand.

21. The method of claim 20, further comprising treating for divalent cations before treating the wastewater with the ferrate(VI)-coated sand.

22. The method of claim 21, further comprising removing divalent cations with chemical precipitation, ion exchange, or membrane filtration.

23. The method of claim 20, further comprising treating the wastewater to adjust pH before treating the wastewater with the ferrate(VI)-coated sand.

24. The method of claim 23, further comprising adding a borate buffer or phosphate buffer to adjust the pH of the wastewater.

25. The method of claim 20, further comprising, in the presence of divalent cations in the wastewater, treating the wastewater with the Fe(VI)-coated sand to remove trace metals.

26. The method of claim 20, further comprising, in the presence of divalent cations in the wastewater, treating the wastewater with the Fe(VI)-coated sand to oxidize contaminants containing electron-donating moieties.

27. The method of claim 26, wherein the electron-donating moieties include phenol or amine moieties or a combination of phenol and amine.

28. A method of treating w astewater, comprising: in the presence of divalent cations in the wastewater, treating the wastewater with a ferrate (VI) coated sand to oxidize a contaminant having phenol or amine moieties.

29. The method of claim 28, wherein the contaminant is acetaminophen.

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