A composite nano-adsorbent for simultaneously removing heavy metals and phenolic pollutants from wastewater and its preparation method

Abstract

The present invention discloses a composite nano-adsorbent and a preparation method thereof. The composite nano-adsorbent comprises polystyrene microspheres grafted with cysteine as a matrix, and hydrated cerium oxide nanoparticles are immobilized within the pores of the microspheres. The preparation method of the composite nano-adsorbent is as follows: first, chloromethylated polystyrene microspheres are subjected to an amination reaction, whereby the chlorine in the chloromethyl group is replaced by an amino group, thereby producing aminomethylated polystyrene microspheres AMPM. Then, using AMPM as a matrix, (NH)4Ce(NO3)6 as a Ce precursor, and NaOH as a precipitant, HCO is immobilized in the pores of AMPM in the form of nanoparticles to produce an intermediate HCO@AMPM. Finally, cysteine is grafted onto the AMPM via an amidation reaction using the catalytic effect of HCO, resulting in the composite nano-adsorbent HCO@CPM, which can simultaneously remove heavy metals and phenolic pollutants from wastewater.

Description

Technical Field

[0001] The invention relates to a composite nano-adsorbent for simultaneously removing heavy metals and phenolic pollutants in wastewater, and also relates to a preparation method of the composite nano-adsorbent. Background Art

[0002] Heavy metal pollution in water bodies is a global environmental pollution problem that has serious negative impacts on human health and the ecological environment. Studies have shown that water bodies contaminated by heavy metals can cause significant damage to the human body even at relatively low concentrations. Therefore, countries around the world have established relatively strict safety control standards for the allowable content of heavy metals in water bodies. Heavy metal wastewater mainly comes from industries such as metallurgy, electroplating, medicine, and machinery manufacturing. In the mineral processing process of the metallurgical industry, due to the use of a large amount of flotation agents, phenolic organic matter is easily formed after conversion. As a result, heavy metal and phenolic pollutants are often present in metal mineral processing wastewater. Their combined toxicity can cause irreversible and serious damage to biological systems and human health even at relatively low concentrations. Therefore, how to efficiently remove heavy metal and phenolic pollutants from wastewater is an urgent problem that needs to be solved in the water treatment industry.

[0003] The common methods for treating composite wastewater containing heavy metals and phenols pollutants on the market currently include adsorption, enhanced coagulation, catalytic oxidation, biological methods, etc. Among them, the adsorption method has the characteristics of low cost, stable performance, simple operation, and good deep treatment effect. At present, the common adsorbents for treating wastewater containing heavy metals and phenols pollutants mainly include activated carbon, natural mineral adsorbents, macroporous adsorption resins, etc. However, the above-mentioned adsorbents mainly adsorb pollutants through their porous structure and large specific surface area. They generally contain only one or one type of adsorption sites and can only adsorb charged ionic pollutants or neutral molecular pollutants. They cannot achieve the simultaneous adsorption and removal of heavy metals and phenols pollutants in wastewater. At the same time, the above-mentioned adsorbent materials also lack selectivity during the adsorption process and are easily interfered with by other coexisting pollutants in the wastewater. It is often necessary to add excessive adsorbents to achieve the desired effect, thereby greatly increasing the treatment cost. Therefore, it is of great significance to develop new adsorbent materials that can simultaneously and selectively remove heavy metals and phenols pollutants. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a composite nano-adsorbent that can simultaneously and deeply remove heavy metals and phenolic pollutants in wastewater. Another purpose of the present invention is to provide a method for preparing the above-mentioned composite nano-adsorbent.

[0005] Technical solution: The composite nano-adsorbent for simultaneously removing heavy metal and phenol pollutants in wastewater of the present invention uses polystyrene microspheres with cysteine grafted on the surface as carriers, and hydrated cerium oxide nanoparticles are fixed in the pores of the polystyrene microspheres.

[0006] Polystyrene microspheres contain a large number of pores with a pore size of 10 to 110 nm.

[0007] Among them, in the composite nanoadsorbent, the grafting rate of cysteine is 68-71% (the grafting rate refers to the ratio of the number of cysteine groups to the total number of replaceable functional groups on the adsorbent), and the mass fraction of Ce is 12.7-17.6% (the mass fraction of Ce refers to the ratio of the mass of Ce to the total mass of the adsorbent).

[0008] The preparation method of the composite nano-adsorbent comprises the following steps:

[0009] (1) Chloromethylated polystyrene (resin) microspheres (CMPM) were added to dimethyl sulfoxide (DMSO) and allowed to stand to obtain solution A. The purpose of adding DMSO in this step was to allow the CMPM to fully swell and facilitate subsequent reactions.

[0010] (2) Hexamethylenetetramine (HMTA) and potassium iodide (KI) were added to solution A to obtain solution B, and solution B was stirred and reacted under heating conditions in a water bath. The purpose of adding HMTA in this step is to replace the chlorine atoms on the chloromethyl groups of CMPM, and the purpose of adding KI is to act as a catalyst to reduce the activation energy of the reaction.

[0011] (3) filtering out the polystyrene microspheres after the reaction in step (2) and transferring them to a hydrochloric acid methanol solution and continuously stirring the reaction; the purpose of this step is to acid-hydrolyze the HMTA attached to the polystyrene microspheres to generate primary amines;

[0012] (4) filtering out the polystyrene microspheres after the reaction in step (3), washing them with methanol and deionized water in sequence until the effluent water contains no chloride ions, and then drying them in an oven to obtain aminomethylated polystyrene microspheres (AMPM). The purpose of this step is to remove the residual reagents and hydrochloric acid in the polystyrene microspheres;

[0013] (5) Dissolve (NH)4Ce(NO3)6, HNO3, and NaNO3 in an aqueous solution of ethanol to obtain a mixed solution; in the mixed solution, the concentration of (NH)4Ce(NO3)6 is 0.18-0.55 mol / L, the concentration of NaNO3 is 2-5 mol / L, and the concentration of HNO3 is 3-5 mol / L; in the aqueous solution of ethanol, the volume ratio of anhydrous ethanol to water is 2-3:10; in this step, an excess of NO3 is added - To generate cerium nitrate complex ion Ce(NO3) m 3-m The purpose of adding anhydrous ethanol is to improve the permeability of the mixed solution, so that the cerium nitrate complex ions can fully enter the internal pores of the hydrophobic polystyrene microspheres (AMPM);

[0014] (6) adding the aminomethylated polystyrene microspheres of step (4) to the mixed solution of step (5), and stirring the mixture under water bath heating conditions; wherein the solid-liquid ratio of the aminomethylated polystyrene microspheres to the mixed solution is 50-150 g / L; the water bath temperature is 50-60° C., the stirring speed is 200-300 rpm, and the stirring is continued until the solution is fully concentrated (the degree of concentration is that the mixed solution is supersaturated and crystals begin to precipitate); the purpose of this step is to preload the negatively charged cerium nitrate complex ions in the mixed solution into the internal pores of the aminomethylated polystyrene microspheres through thermal concentration and ion exchange;

[0015] (7) Filter out the polystyrene microspheres after the reaction in step (6) and transfer them to a NaOH solution with continuous stirring; wherein the mass concentration of the NaOH solution is 10-15%, the solid-liquid ratio of the polystyrene microspheres to the NaOH solution is 50-150 g / L; the stirring speed is 200-300 rpm, and the stirring reaction time is 8-10 h; the purpose of this step is to make the Ce(NO3) preloaded in the pores of the polystyrene microspheres m 3-m It fully reacts with sodium hydroxide to form cerium hydroxide precipitation in situ in the pores;

[0016] (8) The polystyrene microspheres obtained after the reaction in step (7) were filtered out, rinsed with NaCl solution and deionized water in sequence until the effluent was neutral, and then fully soaked with anhydrous ethanol, and then dried in an oven to obtain aminomethylated polystyrene microspheres HCO@AMPM loaded with hydrated cerium oxide (HCO) nanoparticles; the purpose of this step is to convert the hydroxylated polystyrene microsphere matrix into a stable chlorine type (converting the primary amino group from -NH3 + OH - Converted to -NH3 + Cl - ) and remove the residual OH groups on the surface and in the pores of the nanocomposite - The purpose of drying is to dehydrate the cerium hydroxide to form stable nano-hydrated cerium oxide crystal particles;

[0017] (9) Dissolving cysteine in N,N-dimethylformamide (DMF) to obtain solution C; the concentration of cysteine in solution C is 0.1 to 0.3 mol / L; DMF is used as a solvent in this step to fully dissolve cysteine, and DMF as a polar organic solvent can fully enter the pores of the polystyrene microspheres, so that cysteine can fully contact with the functional groups on the polystyrene microspheres (functional groups refer to primary amino groups connected to the polystyrene skeleton, primary amino functional groups are grafted on the surface and interior of the polystyrene microspheres, and HCO is deposited in the pores of the microspheres);

[0018] (10) adding the HCO@AMPM prepared in step (8) to solution C in step (9), heating in a water bath and continuously stirring to react; wherein the solid-to-liquid ratio of HCO@AMPM to N,N-dimethylformamide is 50 to 150 g / L;

[0019] During the reaction, cysteine is deprotonated under the catalytic action of hydrated cerium oxide nanoparticles and enriched in the microspheres through complexation. It then undergoes an amidation reaction with the primary amino groups (primary amines) on the polystyrene backbone, forming amide bonds that are fixed to the resin surface and pores. Heating in a water bath at 60-70°C provides the activation energy required for the reaction and accelerates the reaction process. Stirring for 8-10 hours ensures that the cysteine fully reacts and is grafted onto the polystyrene microsphere backbone.

[0020] (11) The polystyrene microspheres after the reaction in step (10) are filtered out, fully soaked with anhydrous ethanol, and then placed in an oven for drying to obtain a composite nanoadsorbent HCO@CPM; the ethanol soaking in this step is to remove the DMF and unreacted cysteine remaining on the surface and in the pores of the microspheres; the constant temperature drying is to remove the residual anhydrous ethanol.

[0021] Wherein, in step (1), the solid-liquid ratio of chloromethylated polystyrene (resin) microspheres to dimethyl sulfoxide is 20 to 50 g / L; and the standing time is 8 to 12 hours.

[0022] Wherein, in step (2), in solution B, the mass concentration of HMTA is 20-50 g / L, and the mass concentration of KI is 30-75 g / L; the water bath temperature is 70-80° C., the stirring speed is 200-300 rpm, and the stirring reaction time is 6-8 h.

[0023] Wherein, in step (3), the concentration of hydrochloric acid (HCl) in the hydrochloric acid methanol solution is 6 to 8 mol / L; the stirring speed is 200 to 300 rpm, and the stirring reaction time is 2 to 4 h.

[0024] Wherein, in step (4), the drying temperature is 50-70° C., and the drying time is 8-12 h.

[0025] In step (8), the mass concentration of the NaCl solution is 10-15%, the solid-liquid ratio of the polystyrene microspheres to anhydrous ethanol is 100-200 g / L, and the immersion time is 0.5-1.0 h (anhydrous ethanol can fully penetrate into the interior of the polymer and replace the water inside the polymer to facilitate subsequent drying); the drying temperature is 50-70° C., and the drying time is 8-12 h.

[0026] Wherein, in step (10), the water bath temperature is 60-70° C., the stirring speed is 200-300 rpm, and the stirring reaction time is 8-10 h.

[0027] Wherein, in step (11), the solid-liquid ratio of polystyrene microspheres to anhydrous ethanol is 100-200 g / L, the immersion time is 0.5-1.0 h; the drying temperature is 50-70° C., and the drying time is 8-12 h.

[0028] The application of the composite nano-adsorbent HCO@CPM in treating wastewater containing heavy metals and phenolic pollutants is as follows:

[0029] (1) Filtering wastewater containing heavy metals and phenolic pollutants to remove large particles and colloidal pollutants in the wastewater, and adjusting the pH of the filtrate to between 4.0 and 8.0; the initial concentration of heavy metal ions in the filtrate is 5 to 10 mg / L, and the initial concentration of phenolic pollutants is 30 to 60 mg / L;

[0030] Heavy metal ions in wastewater mainly include lead, copper, cadmium, etc., with concentrations ranging from 5 to 10 mg / L. Phenolic pollutants mainly include phenol, p-nitrophenol, cresol, etc., with volatile phenol concentrations ranging from 30 to 60 mg / L.

[0031] (2) The filtrate is passed through an adsorption tower filled with a composite nano-adsorbent HCO@CPM. When the water flows through the HCO@CPM adsorption bed, heavy metals and phenolic pollutants are adsorbed by the composite nano-adsorbent.

[0032] At 25-35°C, the wastewater is passed through an adsorption tower filled with the composite nano-adsorbent HCO@CPM at a flow rate of 4-15 BV / h (BV is bed volume), effectively adsorbing heavy metals and phenolic pollutants in the wastewater onto the composite nano-adsorbent HCO@CPM. The wastewater treatment capacity of each batch is 500-1000 BV. The total lead concentration in the adsorbed effluent is less than 0.5 mg / L, the total cadmium concentration is less than 0.1 mg / L, the total copper concentration is less than 0.5 mg / L, and the volatile phenol concentration is less than 0.5 mg / L.

[0033] (3) When the concentration of heavy metals or volatile phenols in the effluent reaches the breakthrough point, adsorption is stopped; HCl solution, NaOH solution, and deionized water are used in sequence to desorb and regenerate the composite nano-adsorbent HCO@CPM in the adsorption tower, and the regenerated adsorbent is recycled. When the adsorption reaches the breakthrough point (total lead concentration exceeds 0.5 mg / L, or total cadmium concentration exceeds 0.1 mg / L, or total copper concentration exceeds 0.5 mg / L, or volatile phenol concentration exceeds 0.5 mg / L), adsorption is stopped and desorption and regeneration are carried out in sequence using 4 BV 1 mol / L HCl solution, 6 BV deionized water, 2 BV 1 mol / L NaOH, and 8 BV deionized water at a flow rate of 0.5 to 2 BV / h.

[0034] The present invention discloses a preparation method of a composite nano-adsorbent HCO@CPM for simultaneously removing heavy metal and phenol pollutants from wastewater. The method comprises the following steps: first, aminomethylating chloromethylated polystyrene microspheres (CMPM) to obtain aminomethylated polystyrene microspheres (AMPM) with primary amines on the side chains; then, loading hydrated cerium oxide nanoparticles HCO into the pores of the AMPM (the hydrated cerium oxide nanoparticles have two functions in the system: first, acting as a catalyst, utilizing the abundant oxygen vacancies in their crystal lattice to activate and enrich the carboxyl groups in cysteine, thereby grafting new functional groups (amino-NH2 and thiol-SH) onto the polystyrene microsphere skeleton; and second, acting as an adsorbent, enhancing the selective adsorption of heavy metal ions by the material through internal coordination and complexation during the water treatment process); then, amidating reaction is carried out between cysteine and the primary amine groups on the microsphere skeleton to introduce a "thiol-amino" bifunctional group (thiol is sensitive to Hg) onto the polystyrene skeleton. 2+ 、Cd 2+ Soft acid heavy metal ions have strong complexing ability to Pb 2+ 、Cu 2+ 、Zn 2+ The heavy metal ions of the boundary acid also have good complex adsorption capacity, so they can selectively adsorb heavy metal ions from the heavy metal-phenol composite system, and the amino group can be positively charged (-NH3 + ), and then adsorb weakly acidic phenolic pollutants through electrostatic attraction and hydrogen bonding, thereby achieving simultaneous adsorption of heavy metals and phenolic pollutants in wastewater; at the same time, the introduction of long chains formed by cysteine is also conducive to enhancing the hydrophobic effect on the surface of the resin microspheres, thereby better resisting the interference of other coexisting anions in the wastewater such as chloride ions and sulfate ions on the selective adsorption of the adsorbent. After the adsorption is completed, the adsorbent can be regenerated in steps to achieve efficient desorption of phenolic pollutants and heavy metals (the regeneration mechanism is: first, use HCl solution under acidic conditions to make heavy metals and H in the desorption solution react with each other). + Ion exchange occurs for desorption, and after washing with deionized water, NaOH solution is used to neutralize the residual acidic substances, and phenol pollutants are ionized under alkaline conditions and desorbed by ion exchange with OH-), which is convenient for subsequent further recovery and reuse.

[0035] The present invention loads HCO nanoparticles within the pores of aminomethylated polystyrene microspheres. Utilizing the catalytic effect of HCO, cysteine is grafted onto the polystyrene microsphere surfaces via a catalytic amidation reaction, achieving efficient grafting of cysteine onto the polystyrene surface. The resulting composite nanoadsorbent possesses adsorption properties for both heavy metals and phenolic pollutants, enabling the simultaneous adsorption and removal of heavy metals and phenolic pollutants from wastewater. The adsorbent also enables rapid separation and desorption after adsorption, facilitating recycling.

[0036] Beneficial effects: Compared with the prior art, the present invention has the following significant effects:

[0037] (1) The composite nano-adsorbent HCO@CPM prepared by the present invention immobilizes HCO nanoparticles in the pores of aminomethylated polystyrene microspheres. HCO has a stable crystal structure and contains a large number of oxygen vacancies, which can effectively activate the carboxyl groups on cysteine, greatly reducing the activation energy required for the amidation reaction. The amidation reaction process of aminomethylated polystyrene microspheres grafted with cysteine can be carried out under mild conditions without the need for high temperature and high pressure operation, and also avoids the use of toxic and harmful condensing agents and activators, thereby reducing the pollution to the environment during the material preparation process. In addition, the complexation effect of HCO nanoparticles on carboxyl groups is also beneficial to the enrichment of cysteine, thereby increasing its grafting rate on the surface of polystyrene microspheres.

[0038] (2) The composite nano-adsorbent HCO@CPM prepared by the present invention simultaneously introduces thiol, amino and HCO nanoparticles on polystyrene microspheres, wherein: thiol is a soft base, which is effective for the common Pb 2+ 、Cu 2+ 、Zn 2+ 、Cd 2+ Heavy metal ions such as phenols have strong complexing ability and can enrich heavy metal ions from heavy metal-phenol pollutant wastewater system and adsorb and fix them through complexation and electrostatic effects; in the amino water environment, they are positively charged (-NH3 + ), can adsorb weakly acidic phenolic pollutants through electrostatic and hydrogen bonding interactions; the benzene ring structure on the polystyrene skeleton can also achieve adsorption of phenolic pollutants through π-π interaction; the loaded HCO nanoparticles can achieve selective adsorption of heavy metal ions through internal coordination and complexation. Under the combined action of the above active groups, the adsorption capacity and adsorption selectivity of HCO@CPM for heavy metals and phenolic pollutants are significantly improved;

[0039] (3) The composite nano-adsorbent HCO@CPM prepared by the present invention has different adsorption mechanisms for each active group, and can be efficiently desorbed from phenolic pollutants and heavy metals through a simple step-by-step regeneration process. After regeneration, it can be reused for adsorption treatment of heavy metal-phenolic pollutant wastewater, reducing adsorbent consumption and greatly reducing wastewater treatment costs.

[0040] (4) The composite nano-adsorbent HCO@CPM prepared by the present invention is particularly suitable for the treatment of complex industrial wastewater containing heavy metals and phenolic pollutants, and can efficiently remove heavy metals and phenolic pollutants in wastewater. The material of the present invention is used to treat wastewater with an initial heavy metal concentration of 5-10 mg / L and a volatile phenol concentration of 30-60 mg / L. The total lead concentration in the treated water is stably reduced to below 0.5 mg / L, the total cadmium concentration is stably reduced to below 0.1 mg / L, the total copper concentration is stably reduced to below 0.5 mg / L, and the volatile phenol concentration is stably reduced to below 0.5 mg / L, meeting the concentration limit requirements in the pollutant emission standards of relevant industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the structure of the composite nano-adsorbent of the present invention;

[0042] Figure 2 for Figure 1 Chemical structure diagram of the adsorbent material;

[0043] Figure 3 This is the infrared spectrum (FT-IR) of the composite nano-adsorbent prepared in Example 2; Figure 3 This indicates that the thiol and amino groups were successfully grafted onto the adsorbent;

[0044] Figure 4 This is a scanning electron microscope (SEM) image of the composite nano-adsorbent prepared in Example 2; Figure 4 This indicates that the adsorbent monomer is spherical;

[0045] Figure 5 This is a transmission electron microscope (TEM) image of the composite nano-adsorbent prepared in Example 2; Figure 5 This indicates that HCO was successfully loaded into the adsorbent, and the particle size of HCO was approximately 10-20 nm;

[0046] Figure 6 The X-ray diffraction (XRD) pattern of the composite nano-adsorbent prepared in Example 2; Figure 6 The XRD characteristic diffraction peaks of HCO@CPM are consistent with the characteristic peaks of CeO2 standard spectrum, indicating that the HCO loaded inside HCO@CPM exists in the form of cerium oxide crystals with cubic fluorite structure;

[0047] Figure 7 This is a comparison chart of the adsorption performance of the composite nano-adsorbent prepared in Example 2 and other adsorbents for Pb and cresol;

[0048] Figure 8 This is a process diagram for preparing materials using the method of the present invention. DETAILED DESCRIPTION

[0049] Example 1

[0050] The preparation method of the composite nano-adsorbent HCO@CPM of the present invention comprises the following steps:

[0051] (1) In a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 5 g of chloromethylated polystyrene microspheres (CMPM) and 250 mL of dimethyl sulfoxide (DMSO) were added in sequence and allowed to stand for 8 h to allow the CMPM to fully swell, thereby obtaining solution A.

[0052] (2) adding hexamethylenetetramine (HMTA) and potassium iodide (KI) to solution A of step (1) to obtain solution B; controlling the concentration of HMTA in solution B to 20 g / L and the concentration of KI to 30 g / L, and stirring the mixture in a water bath at 70° C. for 6 h (stirring speed: 200 rpm);

[0053] (3) The reaction system of step (2) was cooled to room temperature, the polystyrene microspheres obtained by the reaction were filtered out, and transferred to a hydrochloric acid methanol solution with a HCl concentration of 6 mol / L, and stirred at a stirring speed of 200 rpm for 2 h;

[0054] (4) filtering the polystyrene microspheres obtained in step (3), washing them with methanol and deionized water in sequence until the effluent water contains no chloride ions, and drying them in an oven at 50° C. for 12 h to obtain aminomethylated polystyrene microspheres (AMPM);

[0055] (5) Fully dissolving (NH)4Ce(NO3)6, HNO3, and NaNO3 in 100 mL of an aqueous solution containing 20% (V / V) ethanol to obtain a mixed solution; controlling the concentration of (NH)4Ce(NO3)6 in the mixed solution to be 0.18 mol / L, the concentration of NaNO3 to be 2 mol / L, and the concentration of HNO3 to be 3 mol / L;

[0056] (6) adding AMPM to the mixed solution of step (5) at a solid-liquid ratio of 50 g / L; stirring continuously at a stirring speed of 200 rpm in a water bath at 50° C. to fully concentrate the solution;

[0057] (7) The polystyrene microspheres obtained in step (6) were filtered out and transferred into 100 mL of a 10% NaOH solution, and stirred at 200 rpm for 8 h; the solid-to-liquid ratio of the polystyrene microspheres to the NaOH solution was 50 g / L;

[0058] (8) The polystyrene microspheres obtained in step (7) were filtered out and rinsed with a 10% NaCl solution and deionized water in sequence until the effluent was neutral. The microspheres were then soaked in 50 mL of anhydrous ethanol for 0.5 h (the solid-to-liquid ratio of the polystyrene microspheres to the anhydrous ethanol was 100 g / L), and then dried in a 50°C oven for 12 h to obtain aminomethylated polystyrene microspheres HCO@AMPM loaded with hydrated cerium oxide nanoparticles.

[0059] (9) Dissolve cysteine in 100 mL of N,N-dimethylformamide (DMF) to obtain solution C. The concentration of cysteine in solution C is controlled to be 0.1 mol / L.

[0060] (10) Adding the HCO@AMPM prepared in step (8) to solution C in step (9), stirring the mixture at 200 rpm in a water bath at 60°C for 8 h; wherein the solid-to-liquid ratio of HCO@AMPM to N,N-dimethylformamide is 50 g / L;

[0061] (11) The polystyrene microspheres after the reaction in step (10) were filtered out, soaked in 50 mL of anhydrous ethanol for 0.5 h (the solid-liquid ratio of polystyrene microspheres to anhydrous ethanol was 100 g / L), and then placed in an oven at 50° C. for 12 h to obtain the composite nano-adsorbent HCO@CPM.

[0062] 5 mL (approximately 4.8 g) of the composite nano-adsorbent HCO@CPM from Example 1 was loaded into a jacketed glass adsorption column (16 × 160 mm). 10 L of simulated wastewater (with an initial Cd concentration of 5 mg / L, an initial phenol concentration of 30 mg / L, and a pH of 4.5 ± 0.5) was passed through the HCO@CPM bed at a flow rate of 70 mL / h, with a processing capacity of 5000 mL / batch. After adsorption by HCO@CPM, the effluent Cd concentration dropped to 0.08 mg / L, and the phenol concentration dropped to 0.35 mg / L.

[0063] 20 mL of 1 mol / L HCl solution, 30 mL of deionized water, 10 mL of 1 mol / L NaOH solution, and 40 mL of deionized water were sequentially passed through the composite nano-adsorbent HCO@CPM of Example 1 at a flow rate of 10 mL / h for desorption. The two desorption liquids (HCl solution and NaOH solution) were concentrated to recover phenol and cadmium, respectively. After desorption, the composite nano-adsorbent HCO@CPM can be reused for the simultaneous adsorption treatment of wastewater containing both heavy metal ions and phenolic pollutants.

[0064] Example 2

[0065] The preparation method of the composite nano-adsorbent HCO@CPM of the present invention comprises the following steps:

[0066] (1) In a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 10 g of chloromethylated polystyrene microspheres (CMPM) and 360 mL of dimethyl sulfoxide (DMSO) were added in sequence and allowed to stand for 10 h to allow the CMPM to fully swell, thereby obtaining solution A.

[0067] (2) adding hexamethylenetetramine (HMTA) and potassium iodide (KI) to solution A of step (1) to obtain solution B; controlling the concentration of HMTA in solution B to 35 g / L and the concentration of KI to 40 g / L, and stirring the mixture in a water bath at 75° C. for 7 h (stirring speed: 200 rpm);

[0068] (3) The reaction system of step (2) was cooled to room temperature, the polystyrene microspheres obtained by the reaction were filtered out, and transferred to a hydrochloric acid methanol solution with an HCl concentration of 7 mol / L, and stirred at a stirring speed of 250 rpm for 3 h;

[0069] (4) filtering the polystyrene microspheres obtained in step (3), washing them with methanol and deionized water in sequence until the effluent water contains no chloride ions, and drying them in an oven at 60° C. for 10 h to obtain aminomethylated polystyrene microspheres (AMPM);

[0070] (5) Fully dissolving (NH)4Ce(NO3)6, HNO3, and NaNO3 in 100 mL of an aqueous solution containing 25% (V / V) ethanol to obtain a mixed solution; controlling the concentration of (NH)4Ce(NO3)6 in the mixed solution to be 0.36 mol / L, the concentration of NaNO3 to be 3.5 mol / L, and the concentration of HNO3 to be 4 mol / L;

[0071] (6) adding AMPM to the mixed solution of step (5) at a solid-liquid ratio of 100 g / L; stirring continuously at a water bath temperature of 55° C. and a stirring speed of 250 rpm to fully concentrate the solution;

[0072] (7) The polystyrene microspheres obtained in step (6) were filtered out and transferred into 100 mL of a 12% NaOH solution, and stirred at 250 rpm for 9 h; the solid-to-liquid ratio of the polystyrene microspheres to the NaOH solution was 100 g / L;

[0073] (8) The polystyrene microspheres obtained in step (7) were filtered out and rinsed with a 12% NaCl solution and deionized water in sequence until the effluent was neutral. The microspheres were then soaked in 70 mL of anhydrous ethanol for 0.75 h (the solid-to-liquid ratio of the polystyrene microspheres to the anhydrous ethanol was 143 g / L), and then dried in a 60°C oven for 10 h to obtain aminomethylated polystyrene microspheres HCO@AMPM loaded with hydrated cerium oxide nanoparticles.

[0074] (9) Dissolve cysteine in 100 mL of N,N-dimethylformamide (DMF) to obtain solution C. The concentration of cysteine in solution C is controlled to be 0.2 mol / L.

[0075] (10) Adding the HCO@AMPM prepared in step (8) to solution C in step (9), stirring the mixture at 250 rpm in a water bath at 65°C for 9 h; wherein the solid-to-liquid ratio of HCO@AMPM to N,N-dimethylformamide is 100 g / L;

[0076] (11) The polystyrene microspheres after the reaction in step (10) were filtered out, soaked in 70 mL of anhydrous ethanol for 0.75 h (the solid-liquid ratio of polystyrene microspheres to anhydrous ethanol was 143 g / L), and then placed in an oven at 60° C. for 10 h to obtain the composite nano-adsorbent HCO@CPM.

[0077] 10 mL (approximately 9.6 g) of the composite nano-adsorbent HCO@CPM from Example 2 was loaded into a jacketed glass adsorption column (16 × 160 mm). 15 L of simulated wastewater (with an initial concentration of 8 mg / L of lead and 45 mg / L of cresol, and a pH of 6.0 ± 0.5) was passed through the composite nano-adsorbent HCO@CPM from Example 2 at a flow rate of 100 mL / h, with a treatment capacity of 8000 mL / batch. After adsorption by the HCO@CPM from Example 2, the effluent lead concentration dropped to 0.06 mg / L, and the cresol concentration dropped to 0.41 mg / L.

[0078] 40 mL of 1 mol / L HCl solution, 60 mL of deionized water, 20 mL of 1 mol / L NaOH solution, and 80 mL of deionized water were sequentially passed through the composite nano-adsorbent HCO@CPM of Example 2 at a flow rate of 10 mL / h for desorption. The two desorption liquids were concentrated to recover phenol and lead, respectively. After desorption, the composite nano-adsorbent HCO@CPM can be reused for the simultaneous adsorption treatment of wastewater containing both heavy metal ions and phenolic pollutants.

[0079] Example 3

[0080] The preparation method of the composite nano-adsorbent HCO@CPM of the present invention comprises the following steps:

[0081] (1) In a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 15 g of chloromethylated polystyrene microspheres (CMPM) and 300 mL of dimethyl sulfoxide (DMSO) were added in sequence and allowed to stand for 12 h to allow the CMPM to fully swell, thereby obtaining solution A.

[0082] (2) adding hexamethylenetetramine (HMTA) and potassium iodide (KI) to solution A of step (1) to obtain solution B; controlling the concentration of HMTA in solution B to 50 g / L and the concentration of KI to 75 g / L, and stirring the mixture in a water bath at 80° C. for 8 h (stirring speed: 300 rpm);

[0083] (3) The reaction system of step (2) was cooled to room temperature, the polystyrene microspheres obtained by the reaction were filtered out, and transferred to a hydrochloric acid methanol solution with an HCl concentration of 8 mol / L, and stirred at a stirring speed of 300 rpm for 4 h;

[0084] (4) filtering the polystyrene microspheres obtained in step (3), washing them with methanol and deionized water in sequence until the effluent water contains no chloride ions, and drying them in an oven at 70° C. for 8 h to obtain aminomethylated polystyrene microspheres (AMPM);

[0085] (5) Fully dissolving (NH)4Ce(NO3)6, HNO3, and NaNO3 in 100 mL of an aqueous solution containing 30% (V / V) ethanol to obtain a mixed solution; controlling the concentration of (NH)4Ce(NO3)6 in the mixed solution to be 0.55 mol / L, the concentration of NaNO3 to be 5 mol / L, and the concentration of HNO3 to be 5 mol / L;

[0086] (6) adding AMPM to the mixed solution of step (5) with a solid-liquid ratio of AMPM to the mixed solution of 150 g / L; stirring continuously at a water bath temperature of 60° C. and a stirring speed of 300 rpm to fully concentrate the solution;

[0087] (7) The polystyrene microspheres obtained in step (6) were filtered out and transferred into 100 mL of a 15% NaOH solution, and stirred at 300 rpm for 10 h; the solid-to-liquid ratio of the polystyrene microspheres to the NaOH solution was 150 g / L;

[0088] (8) The polystyrene microspheres obtained in step (7) were filtered out and rinsed with a 15% NaCl solution and deionized water in sequence until the effluent was neutral. The microspheres were then soaked in 75 mL of anhydrous ethanol for 1 h (the solid-to-liquid ratio of the polystyrene microspheres to the anhydrous ethanol was 200 g / L), and then dried in a 60°C oven for 8 h to obtain aminomethylated polystyrene microspheres HCO@AMPM loaded with hydrated cerium oxide nanoparticles.

[0089] (9) Dissolve cysteine in 100 mL of N,N-dimethylformamide (DMF) to obtain solution C. The concentration of cysteine in solution C is controlled to be 0.3 mol / L.

[0090] (10) adding the HCO@AMPM prepared in step (8) to solution C in step (9), stirring the mixture at 300 rpm in a water bath at 70°C for 10 h; wherein the solid-to-liquid ratio of HCO@AMPM to N,N-dimethylformamide is 150 g / L;

[0091] (11) The polystyrene microspheres after the reaction in step (10) were filtered out, soaked in 75 mL of anhydrous ethanol for 1 h (the solid-liquid ratio of polystyrene microspheres to anhydrous ethanol was 200 g / L), and then placed in an oven at 70°C for 8 h to obtain the composite nano-adsorbent HCO@CPM.

[0092] 15 mL (about 14.4 g) of the composite nano-adsorbent HCO@CPM of Example 3 was loaded into a jacketed glass adsorption column (16×160 mm). 15 L of simulated wastewater (in the wastewater, the initial concentration of Cu was 10 mg / L, the initial concentration of p-nitrophenol was 60 mg / L, and the pH was 7.5±0.5) was passed through the column at a flow rate of 60 mL / h.

[0093] Example 3 composite nano-adsorbent HCO@CPM, with a processing capacity of 7500 mL / batch; after adsorption by Example 3 HCO@CPM, the Cu concentration in the effluent dropped to 0.05 mg / L, and the p-nitrophenol concentration dropped to 0.48 mg / L.

[0094] 60 mL of 1 mol / L HCl solution, 90 mL of deionized water, 30 mL of 1 mol / L NaOH solution, and 120 mL of deionized water were sequentially passed through the composite nano-adsorbent HCO@CPM of Example 3 at a flow rate of 7.5 mL / h for desorption. The two desorption liquids were concentrated and then p-nitrophenol and copper were recovered. After desorption, the composite nano-adsorbent HCO@CPM can be reused for the simultaneous adsorption treatment of wastewater containing both heavy metal ions and phenolic pollutants.

[0095] Example 4

[0096] The comprehensive flotation wastewater of a copper-lead-zinc sulfide ore (total copper concentration of 4.37 mg / L, total lead concentration of 2.56 mg / L, total zinc concentration of 1.35 mg / L, and volatile phenol concentration of 47.6 mg / L) was flowed into a shallow sand filter. The sand filter used quartz sand as the filter medium, the filter material particle size was 0.5 mm, the filter material layer height was 60 cm, the filtration rate was controlled at 12 m / h, and the effluent suspended particulate matter (SS) concentration was less than 5 mg / L.

[0097] When the pressure difference between the inlet and outlet of the sand filter reaches 0.1 MPa, backwashing is carried out. The backwashing water flow rate is controlled at 60 m / h (filter layer expansion 20%) and the backwashing time is 2 minutes.

[0098] 10 mL (approximately 9.6 g) of the composite nano-adsorbent HCO@CPM from Example 2 was loaded into a jacketed glass adsorption column (16 × 160 mm). 10 L of the filtrate, after sand filtration, was passed through the bed of the composite nano-adsorbent HCO@CPM from Example 2 at a flow rate of 50 mL / h, with a processing capacity of 5500 mL / batch. After adsorption by HCO@CPM, the effluent Cu concentration dropped to 0.38 mg / L, the Pb concentration to 0.13 mg / L, the Zn concentration to 0.10 mg / L, and the volatile phenol concentration to 0.31 mg / L.

[0099] 40 mL of 1 mol / L HCl solution, 60 mL of deionized water, 20 mL of 1 mol / L NaOH solution, and 80 mL of deionized water were sequentially passed through the composite nano-adsorbent HCO@CPM of Example 2 at a flow rate of 10 mL / h for desorption. The two desorption liquids were concentrated to recover phenol and lead, respectively. After desorption, the composite nano-adsorbent HCO@CPM can be reused for the simultaneous adsorption treatment of wastewater containing both heavy metal ions and phenolic pollutants.

[0100] Example 5

[0101] The composite nano-adsorbent HCO@CPM after desorption in Example 4 was subjected to the adsorption-desorption process four times according to the steps in Example 4, with a processing capacity of 5500 mL / batch. After the fourth adsorption, the effluent Cu concentration of the wastewater filtrate in Example 4 dropped to 0.45 mg / L, the Pb concentration dropped to 0.31 mg / L, the Zn concentration dropped to 0.29 mg / L, and the volatile phenol concentration dropped to 0.47 mg / L, still meeting the effluent water quality requirements.

[0102] Comparative Example 1

[0103] The preparation methods of Comparative Example 1 and Example 2 are basically the same, the only difference being that potassium iodide is not added in step (2).

[0104] 10 mL (approximately 9.6 g) of the composite nano-adsorbent HCO@CPM from Comparative Example 1 was loaded into a jacketed glass adsorption column (16×160 mm). 15 L of simulated wastewater (with an initial concentration of 8 mg / L of lead and 40 mg / L of cresol, and a pH of 6.0±0.5) was passed through the HCO@CPM at a flow rate of 100 mL / h, resulting in a treatment capacity of 8000 mL / batch. After adsorption by the HCO@CPM, the effluent concentrations of lead and cresol were 2.6 mg / L and 34.7 mg / L, respectively.

[0105] Since potassium iodide is not added in step (2), the C-Cl bond of the chloromethyl group is difficult to break, resulting in incomplete aminomethylation of HMTA on the microspheres. Since cerium ions mainly enter the polymer through ion exchange with primary amino groups and thermal concentration, incomplete aminomethylation will affect the exchange of cerium ions, making it difficult for cerium ions to enter the interior of the polymer, affecting the subsequent HCO nanoparticle loading, and further causing the grafting of cysteine to fail to proceed smoothly, ultimately resulting in a significant decrease in its adsorption performance for Pb and cresol.

[0106] Comparative Example 2

[0107] The preparation method of Comparative Example 2 is basically the same as that of Example 2, with the only difference being that hydrated cerium oxide nanoparticles are not loaded, that is, the treatments of steps (5) to (8) are not performed to obtain nano-adsorbent CPM.

[0108] 10 mL (approximately 9.6 g) of the composite nano-adsorbent CPM from Comparative Example 2 was loaded into a jacketed glass adsorption column (16 x 160 mm). 15 L of simulated composite wastewater (Pb concentration of 8 mg / L, cresol concentration of 30 mg / L, pH 6.0 ± 0.5) was passed through the Comparative Example 2 adsorbent bed at a flow rate of 100 mL / h, with a processing capacity of 8000 mL / batch. After adsorption by the Comparative Example 2 CPM, the effluent Pb concentration was 7.8 mg / L, and the cresol concentration dropped to 1.55 mg / L, failing to meet the relevant heavy metal emission concentration limits.

[0109] Since hydrated cerium oxide nanoparticles were not loaded in the polystyrene microspheres, the amidation reaction between the primary amino group on the surface of the microspheres and cysteine was difficult to carry out at 65°C, resulting in incomplete amidation reaction, the thiol group was not introduced into the polystyrene skeleton, and no hydrated cerium oxide nanoparticles were loaded, which ultimately led to a significant decrease in the adsorption performance of heavy metal Pb.

[0110] Comparative Example 3

[0111] The preparation method of Comparative Example 3 is basically the same as that of Example 2, with the only difference being that: step (5) of Comparative Example 3 is: fully dissolving (NH)4Ce(NO3)6 and NaNO3 in 100 mL of water to obtain a mixed solution; controlling the concentration of (NH)4Ce(NO3)6 in the mixed solution to be 0.36 mol / L and the concentration of NaNO3 to be 3.5 mol / L; and composite nano-adsorbent HCO@CPM.

[0112] 10 mL (approximately 9.6 g) of the HCO@CPM composite nano-adsorbent from Comparative Example 3 was loaded into a jacketed glass adsorption column (16 x 160 mm). 15 L of simulated composite wastewater (Pb concentration of 8 mg / L, cresol concentration of 30 mg / L, pH 6.0 ± 0.5) was passed through the bed of the composite nano-adsorbent from Comparative Example 2 at a flow rate of 100 mL / h, with a treatment capacity of 8,000 mL / batch. After adsorption by the HCO@CPM from Comparative Example 3, the effluent Pb concentration was 6.7 mg / L, and the cresol concentration dropped to 8.59 mg / L, failing to meet the relevant heavy metal emission concentration limits.

[0113] Since HNO3 and ethanol were not added in step (5), the pH of the solution and NO3 - The concentration cannot reach Ce 4+ Complexation to form cerium nitrate complex anion Ce(NO3) m 3-m The requirements lead to Ce 4+ On the other hand, the mixed solution has difficulty penetrating into the pores of the hydrophobic AMPM. The two factors together result in only a small amount of Ce being pre-loaded on the surface of the AMPM microspheres, so that the HCO generated by the subsequent deposition reaction is only coated on the AMPM surface. HCO nanoparticles fail to form inside the AMPM pores, making it difficult to play a catalytic role in subsequent steps. This leads to incomplete cysteine grafting, a significant decrease in the adsorption capacity for heavy metal ions, and blocking the pores on the adsorbent surface, affecting its overall adsorption effect.

Claims

1. A composite nano-adsorbent for the simultaneous removal of heavy metals and phenolic pollutants in wastewater, characterized by: The composite nano-adsorbent uses polystyrene microspheres with cysteine grafted on the surface as carriers, and hydrated cerium oxide nanoparticles are fixed in the pores of the polystyrene microspheres; The preparation method of the composite nano-adsorbent comprises the following steps: (1) Chloromethylated polystyrene microspheres were added to dimethyl sulfoxide and allowed to stand to obtain solution A; (2) Hexamethylenetetramine and potassium iodide are added to solution A to obtain solution B, and solution B is stirred and reacted under heating conditions in a water bath; (3) Filtering the polystyrene microspheres after the reaction in step (2), transferring them into a hydrochloric acid methanol solution and continuously stirring the reaction; (4) filtering out the polystyrene microspheres after the reaction in step (3), washing them with methanol and deionized water in sequence until the effluent water contains no chloride ions, and then drying them in an oven to obtain aminomethylated polystyrene microspheres; (5) Dissolving (NH)4Ce(NO3)6, HNO3, and NaNO3 in an aqueous solution of ethanol to obtain a mixed solution; in the mixed solution, the concentration of (NH)4Ce(NO3)6 is 0.18-0.55 mol / L, the concentration of NaNO3 is 2-5 mol / L, and the concentration of HNO3 is 3-5 mol / L; in the aqueous solution of ethanol, the volume ratio of anhydrous ethanol to water is 2-3:10; (6) Adding the aminomethylated polystyrene microspheres of step (4) to the mixed solution of step (5), stirring and reacting under heating conditions in a water bath; wherein the solid-liquid ratio of the aminomethylated polystyrene microspheres to the mixed solution is 50-150 g / L; the water bath temperature is 50-60°C, the stirring speed is 200-300 rpm, and stirring is continued until the solution is fully concentrated; (7) Filter out the polystyrene microspheres after the reaction in step (6), transfer them to a NaOH solution and continue stirring; wherein the mass concentration of the NaOH solution is 10-15%, and the solid-liquid ratio of the polystyrene microspheres to the NaOH solution is 50-150 g / L; the stirring speed is 200-300 rpm, and the stirring reaction time is 8-10 h; (8) The polystyrene microspheres obtained after the reaction in step (7) were filtered out, rinsed with NaCl solution and deionized water in sequence until the effluent was neutral, then fully soaked with anhydrous ethanol, and then dried in an oven to obtain aminomethylated polystyrene microspheres HCO@AMPM loaded with hydrated cerium oxide nanoparticles; (9) Dissolve cysteine in N,N-dimethylformamide to obtain solution C; the concentration of cysteine in solution C is 0.1-0.3 mol / L; (10) Adding the HCO@AMPM prepared in step (8) to solution C in step (9), heating in a water bath and continuously stirring to react; wherein the solid-liquid ratio of HCO@AMPM to N,N-dimethylformamide is 50-150 g / L; (11) The polystyrene microspheres after the reaction in step (10) were filtered out, fully soaked with anhydrous ethanol, and then dried in an oven to obtain a composite nano-adsorbent HCO@CPM; in the composite nano-adsorbent, the grafting rate of cysteine was 68~71%, and the mass fraction of Ce was 12.7~17.6%.

2. The composite nano-adsorbent according to claim 1, characterized in that: In step (1), the solid-liquid ratio of chloromethylated polystyrene microspheres to dimethyl sulfoxide is 20-50 g / L; and the standing time is 8-12 h.

3. The composite nano-adsorbent according to claim 1, characterized in that: In step (2), in solution B, the mass concentration of hexamethylenetetramine is 20-50 g / L, and the mass concentration of potassium iodide is 30-75 g / L; the water bath temperature is 70-80°C, the stirring speed is 200-300 rpm, and the stirring reaction time is 6-8 h.

4. The composite nano-adsorbent according to claim 1, characterized in that: In step (3), the hydrochloric acid concentration in the hydrochloric acid methanol solution is 6-8 mol / L; the stirring speed is 200-300 rpm, and the stirring reaction time is 2-4 h.

5. The composite nano-adsorbent according to claim 1, characterized in that: In step (4), the drying temperature is 50-70°C and the drying time is 8-12 hours.

6. The composite nano-adsorbent according to claim 1, characterized in that: In step (8), the mass concentration of the NaCl solution is 10-15%; the solid-liquid ratio of polystyrene microspheres to anhydrous ethanol is 100-200 g / L, the immersion time is 0.5-1.0 h; the drying temperature is 50-70° C., and the drying time is 8-12 h.

7. The composite nano-adsorbent according to claim 1, characterized in that: In step (10), the water bath temperature is 60-70°C, the stirring speed is 200-300 rpm, and the stirring reaction time is 8-10 h.

8. The composite nano-adsorbent according to claim 1, characterized in that: In step (11), the solid-liquid ratio of polystyrene microspheres to anhydrous ethanol is 100-200 g / L, the soaking time is 0.5-1.0 h; the drying temperature is 50-70° C., and the drying time is 8-12 h.

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