Waste polishing powder-shell powder composite material and preparation method and application thereof

Abstract

The application discloses a waste polishing powder-shell powder composite material and a preparation method and application thereof, and belongs to the technical field of sewage treatment. The composite material is composed of waste polishing powder and shell powder in a mass ratio of 0-6:0-3. The preparation method comprises the following steps: placing the waste polishing powder in a sulfuric acid solution, performing magnetic stirring pyrolysis at 60 DEG C, filtering out insoluble substances in the waste polishing powder after the reaction is completed, and cooling to room temperature, adjusting the pH value to be higher than 2; adding the shell powder, performing ultrasonic cleaning, adding an alkaline solution to adjust the pH value to be greater than 11 while performing magnetic stirring, and performing magnetic stirring at 60 DEG C, cooling to room temperature after the reaction is completed, washing until the waste polishing powder-shell powder composite material is neutral, drying, and grinding to obtain the waste polishing powder-shell powder composite material. The waste polishing powder-shell powder composite material has excellent utilization prospect, can be used for removing phosphates and heavy metal ions in water at the same time, and has the advantages of simple preparation method, low cost, high efficiency and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a waste polishing powder-shell powder composite material, its preparation method, and its application. Background Technology

[0002] Phosphorus (P) is a non-renewable resource and an essential nutrient for biological growth, playing a significant role in global food production. However, excessive release of phosphates into water bodies leads to eutrophication, posing a serious threat to aquatic ecosystems. Simultaneously, with rapid industrialization, large amounts of heavy metal ions are discharged into water bodies through industrial wastewater from mining and smelting, fertilizer manufacturing, leather production, battery manufacturing, electroplating, rubber, woodworking, and textile dyeing, causing severe pollution. Representative examples include cadmium (Cd), copper (Cu), lead (Pb), arsenic (As), and chromium (Cr). Heavy metals, due to their serious health risks and severe pollution, have become one of the most concerning pollutants in water pollution. Currently, most municipal sewage and industrial wastewater contain both phosphorus and heavy metal pollution. Therefore, finding a highly efficient, environmentally friendly, low-cost, and simple-to-prepare material that can simultaneously remove phosphate and heavy metal ion pollutants from water bodies is of significant practical importance.

[0003] The main methods for removing phosphorus and heavy metal ions from water bodies include chemical precipitation, biological methods, ion exchange, and adsorption. Among these, adsorption is considered the most promising method due to its advantages such as low cost, simple operation, high efficiency, and rapid reaction. Currently developed adsorbents mainly include metal oxides or metal hydroxides represented by Fe and La, clay minerals such as bentonite and palygorskite, industrial and agricultural wastes such as fly ash and straw, and carbon-based materials such as biochar. Metal hydroxide materials are particularly noteworthy due to their stable crystal structure and strong corrosion resistance. Among the many adsorbent materials, nanomaterials are attracting attention as potential solid-phase adsorbents due to their large specific surface area, high stability, and high adsorption capacity.

[0004] Based on the principles of soft and hard, Lewis acid and base interactions, hard base phosphates prefer to react with hard acid metal ions (Fe). 3+ Mg 2+ Ca 2+ Al 3+ Zr 4+ La 3+ and Ce 3+(etc.) to form complexes. Metal doping is considered an effective method to modify the structure of compounds and optimize adsorption performance through electron acceptors (p-doping) or donors (n-doping). According to previous studies, metal hydroxides can provide more adsorption sites than metal oxides in the same form, which is beneficial to phosphate adsorption reactions. In addition, the abundant hydroxyl groups on the surface of metal hydroxide materials can undergo effective complexation and chemical precipitation reactions with heavy metal ions, thereby removing heavy metal ions.

[0005] Current research focuses on the modification and reuse of waste materials and the preparation of novel adsorbents for removing pollutants from water. Waste not only occupies a large amount of space but also pollutes the environment. Reusing waste can achieve waste-to-waste treatment, conserve resources, and improve economic efficiency. For example, discarded eggshells, crab shells, orange peels, straw, and tailings from industrial waste can effectively remove phosphates with slight treatment; discarded walnuts can remove arsenic ions; corn cobs and corn stalks, sawdust, pomegranate peels, and melon rinds can effectively remove copper ions; and industrial waste (fertilizer) can remove heavy metals such as Pb and Cd. However, among existing adsorbents, those with specific adsorption properties for both phosphates and heavy metal ions in water are rare. In current research, rare earth elements La and Ce have attracted much attention due to their excellent removal effects on phosphates and heavy metal ions in water; however, pure rare earth elements La and Ce are expensive. Shells are a type of natural material containing calcium, which is non-toxic, harmless, and widely available. Although they have some adsorption capacity for phosphates and heavy metal ions, their performance is unstable. Currently, most methods utilize waste shells to prepare calcium-containing biochar, but this process is not only complex but also requires high temperatures. Waste rare earth polishing powder (CeLa2O3F3) is rich in La and Ce. Combining it with shell powder to prepare adsorbents for adsorbing phosphates and heavy metal ions can overcome the common problems of existing adsorbents, such as high cost, insufficient adsorption capacity, complex material preparation, and inability to simultaneously remove anionic and cationic pollutants, while also achieving waste-to-waste treatment. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention aims to provide a waste polishing powder-shell powder composite material, its preparation method, and its application, for the simultaneous removal of phosphate and heavy metal ions from water. The surface structure and physicochemical properties of the material are characterized, the influencing factors of the adsorption process are investigated through batch experiments, and the adsorption mode and adsorption mechanism are determined based on the characterization results. At the same time, the effectiveness of the target material in treating actual wastewater is verified.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows:

[0008] A waste polishing powder-shell powder composite material is provided, which is composed of waste polishing powder and shell powder in a mass ratio of 0-6:0-3.

[0009] Furthermore, the mass ratio of the waste polishing powder to the shell powder is 5:1.

[0010] A method for preparing waste polishing powder-shell powder composite material includes the following steps:

[0011] Waste polishing powder was placed in sulfuric acid solution and pyrolyzed with magnetic stirring at 60°C. After the reaction was completed, the undissolved substances were filtered out and the mixture was cooled to room temperature. The pH value was then adjusted to above 2.

[0012] Shell powder was added, and after ultrasonic cleaning, an alkaline solution was added to adjust the pH value to be greater than 11 while magnetic stirring was performed. The mixture was magnetically stirred at 60°C. After the reaction was completed, it was cooled to room temperature and washed until it showed a neutral pH. The mixture was then dried and ground to obtain a waste polishing powder-shell powder composite material.

[0013] Furthermore, the magnetic stirring time is 2 hours.

[0014] Furthermore, the ultrasonic cleaning time is 10 minutes.

[0015] Furthermore, the shell powder is shell powder that has passed through a 200-mesh sieve, and the waste polishing powder-shell powder composite material is ground and then passed through a 200-mesh sieve.

[0016] Furthermore, the alkaline solution is sodium hydroxide.

[0017] Application of waste polishing powder-shell powder composite material prepared by the preparation method of waste polishing powder-shell powder composite material in wastewater treatment.

[0018] Furthermore, the wastewater contains phosphates and heavy metal ions.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The waste polishing powder-shell powder composite material prepared in this invention can simultaneously remove phosphate and heavy metal ions from water. Results show that after pretreatment of the waste polishing powder and shell powder, rare earth elements La and Ce were effectively extracted from the polishing powder via acid pyrolysis. A co-precipitation method was used to combine the polishing powder and shell powder at a mass ratio of 5:1 to prepare PB-5 nanocomposite material. SEM and XRD characterization of the surface morphology and crystal structure revealed that La and Ce exist as rod-shaped La(OH)3 and Ce(OH)3, respectively, while Ca exists as Ca(OH)2. BET characterization showed that PB-5 is a mesoporous material with an average pore size of 9.658 nm, and the PB-5 obtained at a mass ratio of 5:1 has the largest specific surface area, 134.655 m². 2 / g. Furthermore, PB-5 is simple to prepare, low in cost, highly efficient, and environmentally friendly, making it an adsorbent with excellent application prospects for removing phosphorus and heavy metals from water. Attached Figure Description

[0021] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0022] Figure 1 The removal efficiency of waste polishing powder and shell powder under different mass ratios;

[0023] Figure 2 SEM image (ab) and EDS map (ce) of PB-5;

[0024] Figure 3 XRD pattern (a) and N2 adsorption desorption curve (b) of PB-5;

[0025] Figure 4 The effects of time on adsorption (a), pH on phosphate adsorption, and pH after the reaction (b) on Cu. 2+ Effects of adsorption (c), Effects of coexisting ions on phosphate adsorption (d), Effects of coexisting ions on Cu 2+ The effect of adsorption (e);

[0026] Figure 5 Langmuir isotherm (a) for adsorbed phosphate, Freundlich isotherm (b) for adsorbed phosphate, Temkin isotherm (c) for adsorbed phosphate, and Cu adsorption isotherm. 2+ Langmuir isotherm (d), adsorbed Cu 2+ Freundlich isotherm (e), adsorbed Cu 2+ Temkin isotherm (f), pseudo-first-order and pseudo-second-order dynamics (g), Elovich dynamics (h);

[0027] Figure 6 The images show the Zeta potential before and after the adsorption reaction (a), XRD patterns before and after the adsorption reaction (b), and FTIR patterns before and after the adsorption reaction (c).

[0028] Figure 7 XPS spectra before and after the reaction (a), P2p after phosphate adsorption (b), and Cu adsorption... 2+ Later Cu2p(c);

[0029] Figure 8 La3d spectra of the composite material (a), La3d spectra after phosphate adsorption (d), and Cu adsorption... 2+ La3d spectrum (g), Ce3d spectrum of the composite material (b), Ce3d spectrum after phosphate adsorption (e), Cu adsorption 2+ Ce3d spectrum (h), Ca2p spectrum of the composite material (c), Ca2p spectrum after phosphate adsorption (f), Cu adsorption 2+ Post-Ca2p spectrum (i);

[0030] Figure 9 For the cyclic desorption experiment (a), the release of PB-5 under different pH conditions (b);

[0031] Figure 10 PB-5 is used for the simultaneous removal of phosphate and Cu from actual wastewater. 2+ . Detailed Implementation

[0032] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] I. Materials and Methods

[0035] 1. Materials

[0036] The materials used in this study included polishing powder produced by Baotou Huaxing Rare Earth Technology Co., Ltd., commercially available shell powder (specific specifications are shown in Table 1), sulfuric acid (H2SO4), sodium hydroxide (NaOH), ascorbic acid (C6H8O6), sodium chloride (NaCl), sodium nitrate (NaNO3), sodium sulfate (Na2SO4), sodium bicarbonate (NaHCO3), potassium chloride (KCl), calcium chloride (CaCl2), potassium dihydrogen phosphate (KH2PO4), copper sulfate (CuSO4), ammonium molybdate ((NH4)MoO4), and potassium antimony tartrate (C8H4K2OSb2). All chemicals were of analytical grade and purchased from Aladdin Chemical Co., Ltd. (China). Unless otherwise specified, deionized water (DI) was used to prepare solutions in the experiments. The actual wastewater was taken from the aeration tank of the Gongzhufu Wastewater Treatment Plant in Hohhot, China.

[0037] Table 1.1. Composition and content of waste polishing powder and shell powder

[0038]

[0039] 2. Material Preparation

[0040] Weigh 5g of waste polishing powder and place it in 200ml of 5mol / L sulfuric acid solution. Pyrolyze at 60℃ with magnetic stirring for 2 hours. After the reaction, filter out undissolved substances (such as polishing pads and glass) and cool to room temperature. Adjust the pH to above 2. Add 1g of shell powder that has passed through a 200-mesh sieve. Ultrasonically clean for 10 minutes, then add NaOH solution while magnetically stirring until the pH is greater than 11 (at this point, a precipitate will appear in the beaker, and the color change can be visually observed). Stir magnetically at 60℃ for 2 hours. After the reaction, cool to room temperature and wash until neutral. Then dry, grind, and pass through a 200-mesh sieve for later use.

[0041] II. Analysis and Characterization

[0042] 1. Experimental Procedure

[0043] A certain amount of anhydrous KH₂PO₄ and CuSO₄ were dissolved in deionized water to prepare 1000 mg / L phosphate and Cu 2+ For all adsorption experiments, the stock solutions were diluted to the desired concentrations with deionized water. For adsorption isotherms, the concentrations of phosphorus and copper ranged from 5 mg / L to 200 mg / L, and the test temperatures were 10°C, 25°C, and 35°C, respectively. Furthermore, the initial concentrations of the phosphate solution and the copper ion solution were fixed at 60 mg / L and 70 mg / L, respectively. In adsorption kinetic studies, the post-reaction solution concentrations were determined after a selected adsorption time. For pH and coexisting ions (Cl...),... - , Na + K+ Ca 2+ The pH was adjusted using HCl and NaOH solutions. Desorption cycling was performed using 2 mol NaOH solution. All experiments were conducted in 250 mL Erlenmeyer flasks and shaken in a constant-temperature shaking incubator at 200 rpm. Each experiment was repeated three times, and the average value was taken. After the experiments, the equilibrium adsorption capacity (q) was calculated. e The efficiency (E) is calculated using equations (1) and (2):

[0044]

[0045]

[0046] Where, q e Indicates equilibrium adsorption capacity (mg / g), C o and C e V represents the initial and equilibrium concentrations (mg / L), V represents the solution volume (L), and m represents the adsorbent mass (g).

[0047] 2. Characterization

[0048] The crystal structure (α1, α2) was analyzed using an X-ray diffraction spectrometer (XRD, Ultimal V, Rigaku) ​​equipped with a copper anode (CuK). The 2θ range was 5–90°, and the operating voltage was 40 kV and 40 mA. The surface morphology and structure of the adsorbent were characterized by scanning electron microscopy (SEM, Quanta 25, FEI, USA) at 20 kV. The functional groups on the material surface were analyzed by Fourier transform infrared spectroscopy (FTIR, Nicolet iS5, Thermo Fisher, USA) at 400–4000 cm⁻¹. -1 Identification was performed within the specified range. Furthermore, the specific surface area and porosity of the material were characterized at 77 K using a surface area analyzer (TriStarⅡ3020, USA). The zeta potential of the material was measured using a Zeta potential analyzer (Zetasizer Nano ZS, Malvern, UK) to locate the zero-point charge. X-ray photoelectron spectroscopy was performed using a standard Al Kα X-ray source (XPS, Thermo SCIENTIFIC ESCALAB 250xi, USA) to investigate the interactions between phosphate and copper ions and the adsorbent. A shaking incubator (SHAK116, Vison Scientific Co, Korea) was used to agitate the samples in the adsorption experiments. Inductively coupled plasma atomic emission spectrometry (ICP-A800, Agilent Technologies, USA) was used to measure the La / Ce content in the solution.

[0049] III. Results and Discussion

[0050] 1. Determination of the optimal mass ratio of waste polishing powder to shell powder required for the target material

[0051] The removal efficiency of polishing powder and shell powder under different mass ratios is shown in Table 2. Figure 1 As shown in the figure, for phosphate removal, as the mass ratio of polishing powder to shell powder increases from 1:1 to 6:1, the removal rate increases from 40% to 92%. At 6:1, the removal efficiency no longer changes compared to 5:1, indicating that the continuous increase of polishing powder during adsorbent preparation may lead to partial overlap and aggregation of the adsorbent layer, resulting in a reduction in the total surface area of ​​the adsorbent and no further increase in removal efficiency. With the increase of shell powder doping (polishing powder to shell powder mass ratios of 5:0, 5:1, 5:2, and 5:3), the phosphate removal efficiency first increases and then decreases. Since Ca has a lower affinity for phosphorus than La and Ce, excessive Ca will lead to material accumulation and a decrease in the adsorption capacity of the synthesized material for phosphorus. Therefore, 5:1 is determined to be the optimal ratio for phosphorus removal.

[0052] As the mass ratio of polishing powder to shell powder gradually increases from 1:1 to 6:1, for Cu 2+ The removal rate increased from 80% to 90%, and at a ratio of 6:1, the removal efficiency remained unchanged compared to 5:1. However, when the polishing powder mass was constant, with the increase of shell powder content (polishing powder to shell powder mass ratios of 5:0, 5:1, 5:2, and 5:3), Cu... 2+ The removal efficiency showed a trend of increasing, decreasing, and increasing again. The removal rate at 5:3 was almost the same as that at 5:1, but the removal rate of phosphate decreased significantly. Therefore, 5:1 is also an effective ratio for removing Cu. 2+ The optimal ratio was determined. Therefore, PB-5 was identified as the target material and applied to all subsequent experiments.

[0053] Table 2. Removal efficiency of polishing powder and shell powder under different mass ratios

[0054]

[0055] 2. Material Characterization

[0056] Figure 2 (ae) displays the SEM image and EDS spectrum of PB-5. Figure 2As shown in a) and 2b), the morphology of the cubic crystals is consistent with that of Ca(OH)2 in the literature (K.Wang, N.Peng, D.Zhang, H.Zhou, J.Gu, J.Huang, C.Liu, Y.Chen, Y.Liu, J.Sun, Efficient removal of methylene blue using Ca(OH)2 modified biochar derived from rice straw, Environmental Technology & Innovation (2023).). The structure of the cubic rod-like bodies matches the morphology of La(OH)3 and Ce(OH)3, indicating that La, Ce, and Ca have been stably bonded together. The EDS spectrum shows the elemental composition of the PB-5 composite material surface. The spectrum shows that the La, Ce, and Ca elements are relatively uniformly distributed in the composite material, proving that the PB-5 composite material was successfully prepared.

[0057] The crystal composition of the PB-5 composite material was determined by XRD, such as... Figure 3 As shown in Figure a, in the PB-5 X-ray diffraction pattern, the peaks at 15.53°, 28.10°, and 47.14° represent La(OH)3 and Ce(OH)3 (PDF#83-2034 and PDF#74-0665), while the peaks at 18.2° and 54.1° represent Ca(OH)2 (PDF#81-2041). This indicates that the two raw materials, waste polishing powder and shell powder, successfully combined with Ca(OH)2 in the forms of La(OH)3 and Ce(OH)3, demonstrating successful material preparation. This is also consistent with the SEM characterization results mentioned earlier.

[0058] The N2 adsorption-desorption isotherm of PB-5 composite material is as follows: Figure 3 As shown in b. The BET curve spectrum shows that the adsorption-desorption isotherm follows a type IV isotherm, indicating that the adsorbate can react well with the adsorbent surface at relatively low pressure. Simultaneously, the spectrum shows a type H3 hysteresis line, indicating that the material is either mesoporous or macroporous. Combined with the pore size distribution diagram, the total pore volume of the material is 0.2821 cm³. 3 The average pore size is 9.658 nm, indicating a mesoporous structure (2-50 nm). This suggests monolayer adsorption, and mesoporous materials exhibit greater chemical stability during use. Mesoporous materials are considered promising adsorbents for water pollutants due to their high porosity, large adsorption capacity, and ability to accelerate adsorption reactions. Specific surface area is a crucial factor in adsorption capacity; the PB-5 composite material has a specific surface area of ​​134.655 nm. 2The relatively large specific surface area of ​​PB-1 (37.163 m² / g) indicates that a larger specific surface area is beneficial for the exposure of active sites on the inner surface of the material. 2 The specific surface area of ​​PB-2 is 57.145 m² / g. 2 The specific surface area of ​​PB-3 is 66.535 m² / g. 2 The specific surface area of ​​PB-4 is 84.923 m² / g. 2 / g, which shows that as the content of waste polishing powder increases, the specific surface area of ​​the composite material also increases. PB-5 has the largest specific surface area and therefore has the best adsorption performance. Therefore, PB-5 is the best adsorbent material, which is consistent with the previous research.

[0059] 3. Results and Discussion of Batch Experiments

[0060] (1) Time

[0061] Figure 4 a shows the effect of reaction time on adsorption efficiency, phosphate, and Cu. 2+ The removal rate reached 80% after 30 minutes of reaction, indicating that the adsorption process of PB-5 on both substances was completed rapidly within 30 minutes, and the adsorption reached equilibrium at 180 minutes.

[0062] (2) pH, coexisting ions

[0063] Phosphate exists in different forms at different pH values, making it crucial to study the effect of pH changes on adsorption efficiency. At pH < 2, phosphate exists as H3PO4; at pH 2 ≤ pH ≤ 7, phosphate exists as... Phosphate exists in the form of pH 7 < pH ≤ 12. Phosphate exists in the form of phosphate at pH > 12. It exists in form.

[0064] Experimental results are as follows Figure 4 As shown in bc, phosphate and Cu 2+ The adsorption efficiency is highly pH-dependent. Phosphate removal initially increases and then decreases with increasing pH in the range of 1-12, reaching a peak of 97% at pH 3. This is likely because acidic conditions facilitate the release of hydroxyl groups from the material surface into the solution, thus promoting the exchange process between hydroxyl groups and phosphate. This aligns with existing research, as higher pH values ​​lead to deprotonation and negative charge of the adsorbent, while also competing for adsorption sites. However, the removal efficiency remains high within the pH range of 3-7, because at this pH, the phosphate in the solution is primarily in the form of... The removal efficiency is not ideal in the pH range of 7-10 because the phosphate in the solution is in the form of... Compared to This further promotes adsorption. It is worth noting that phosphate removal rates remain high at pH=1 and pH=2, the reason for which will be explained in the adsorption mechanism section. Furthermore, the pH value increases after the reaction, indicating that the OH- ions in the solution... - The increased content of phosphate suggests that ligand exchange occurred between the -OH group on PB-5 and the phosphate group.

[0065] The pH value of a solution significantly affects the metal speciation, surface charge, and stability of the adsorbent; therefore, studying the effect of pH changes on the adsorption efficiency of metal ions is crucial. Studies have shown that when pH is less than 6, copper ions are predominantly Cu(II) in the solution, while at pH greater than 6, copper ions precipitate as copper hydroxide, which is not included in this study. Therefore, to avoid the conversion to copper(II) hydroxide precipitate affecting the experiment, the effect of pH within the range of 1-6 on the reaction process was investigated. Figure 4 As shown in c, Cu increases with pH in the range of 1-6. 2+ The removal rate showed a continuous increasing trend, with Cu at pH=6. 2+ The removal rate was the highest, consistent with existing studies. However, the adsorption capacity was zero under pH 1 and 2 conditions, which may be due to the material's poor adhesion to Cu in an overly acidic environment. 2+ The number of effective adsorption sites decreases, and electrostatic repulsion also leads to low adsorption capacity at lower pH conditions. Furthermore, as the pH increases, the amount of OH- in the solution decreases. - It will increase, which is beneficial to Cu 2+ The surface complexation reaction between Cu and the adsorbent is beneficial. 2+ The removal of.

[0066] Selecting adsorption performance is an important factor to consider when evaluating adsorbents. This experiment investigated the adsorption performance of Cl... - , Na + K + Ca 2+ The effects of several ions on adsorption are shown in 4d and 4e. When the concentration increased from 0 mol / L to 0.1 mol / L, phosphate adsorption was inhibited, and the removal rate decreased from 97% to 27%. The effect on phosphate adsorption is mainly attributed to the increase in solution pH due to increased concentration, which in turn reduces the amount of phosphate adsorbed. Other coexisting ions in the water also affect phosphate and Cu. 2+ Adsorption had no significant effect; furthermore, the figure shows that Ca... 2+ When the concentration increased to 0.1 mol / L, the adsorption efficiency of both ions increased slightly, indicating that Ca... 2+ Once a certain concentration is reached, it will react with phosphate, which is consistent with existing research.

[0067] (3) Isotherms and dynamics

[0068] Isotherm models reflect the relationship between adsorbate concentration and adsorption capacity of adsorbent in equilibrium, which is crucial for a deeper understanding of adsorption behavior. Figure 5 af showed that PB-5 had initial phosphate, Cu 2+ Adsorption isotherms at concentrations ranging from 5 to 200 mg / L, including those for phosphate and Cu. 2+ The adsorption process was conducted at pH 3 and pH 6, respectively. The experimental data were fitted to three models: Langmuir, Freundlich, and Temkin. The model equations are as follows:

[0069]

[0070]

[0071]

[0072] In the formula, C e (mg / L) represents the phosphate concentration at equilibrium, q e (mg / g) represents the adsorption capacity of phosphate, q max (mg / g) represents the theoretical maximum adsorption capacity, K L (L / mg) and K F ((mg / g) / (mg / L)1 / n) are constants in the Langmuir and Freundlich models, respectively; n is the heterogeneous molecule, which is related to the adsorption strength, and B T =RT / b, b(J·mol) -1 ) is the Temkin constant related to the heat of adsorption, and R is the gas constant (8.314 J·mol⁻¹). -1 ·K -1 T(K) and K are absolute temperatures, K T The equilibrium corresponds to the maximum binding energy (L·mg). -1 The binding constant of ).

[0073] The results showed that for phosphate and Cu 2+ The adsorption of phosphate and Cu was better fitted by the Langmuir isotherm model compared to the Freundlich and Temkin isotherm models, indicating that phosphate and Cu adsorption... 2+The adsorption process was predominantly monolayer adsorption with a homogeneous adsorbent surface. Fitting parameters are shown in Tables 3 and 4. In the Freundlich isotherm model, the 1 / n reaction adsorption strength is high; when 1 / n is greater than 2, adsorption is difficult, and when 1 / n is between 0.1 and 0.5, adsorption is easy. In this study, 1 / n was consistently between 0.1 and 0.5, indicating that the adsorption process proceeded easily. The Langmuir isotherm model can be used to estimate the adsorption capacity; the maximum adsorption capacity for phosphate reached 66.26 mg / g, and for Cu... 2+ The maximum adsorption capacity can reach 79.34 mg / g.

[0074] Table 3. Isotherm model parameters for P adsorption in PB-5 composite material

[0075]

[0076] Table 4. Cu adsorption of PB-5 composite material 2+ isotherm model parameters

[0077]

[0078] Figure 5 g and Figure 5 h showed that PB-5 adsorbed phosphate and Cu. 2+ The fitting formulas for the pseudo-first-order dynamic model, the pseudo-second-order dynamic model, and the Elovich dynamic model are as follows:

[0079]

[0080]

[0081]

[0082] Where, q e (mg / g) and q t (mg / g) represent the phosphate adsorption capacity at equilibrium and reaction time t (min), respectively. K1 (min) -1 Kα and K2 (g / (mg·min)) are the pseudo-first-order and pseudo-second-order adsorption rate constants, respectively. α is the initial adsorption constant, and β is the adsorption constant. As shown in the figure, compared to the pseudo-first-order kinetic model, phosphate and Cu2... 2+ The adsorption of both follows pseudo-second-order kinetics and the Elovich mode, indicating that both adsorption processes are mainly chemisorption, and the adherence to the Elovich mode suggests a faster adsorption rate. Fitting parameters are shown in Tables 5 and 6.

[0083] Table 5. Kinetic model parameters for P adsorption in PB-5 composite material

[0084]

[0085] Table 6. Cu adsorption of PB-5 composite material 2+ kinetic model parameters

[0086]

[0087]

[0088] 4. Adsorption mechanism

[0089] (1) Zeta potential

[0090] Figure 6 a demonstrated the adsorption of phosphate and Cu by PB-5. 2+ The Zeta potentials before and after are shown in the graph, indicating the pH of PB-5. pzc =3.68, below which it carries a positive charge, and the lower Zeta potential also explains why there is good phosphate removal at pH values ​​of 1 and 2, i.e., the predominantly positively charged adsorbent and the negatively charged phosphate ions are electrostatically attracted. At lower pH values, the material and Cu 2+ Electrostatic repulsion occurs, Cu 2+ Adsorption occurs almost non-existently. This also explains why the adsorption amount is 0 at pH values ​​of 1 and 2. After the composite material adsorbs phosphate, the pH... pzc The pH dropped to 2.66. Clearly, the presence of phosphate anions caused the adsorbent surface to carry a greater negative charge, leading to a decrease in pH. pzc This phenomenon typically occurs in the inner spheres of ligand exchange as the pH changes towards lower values. Furthermore, the zeta potential of the material gradually decreases with increasing pH, due to the OH-... - This leads to a decrease in the surface positive charge density of the material, eventually resulting in a negative charge. The electrostatic repulsion of this negative charge against phosphate ions causes a gradual reduction in adsorption capacity, which is consistent with the research mentioned earlier. Composite material adsorbs Cu 2+ Post-pH pzc Cu rose to 4.23 2+ The presence of [something] causes the adsorbent surface to carry more positive charges, leading to a decrease in pH. PZC A change in pH towards a higher value, however, is not sufficient for electrostatic attraction alone to cause an increase in zero-point charge. The change in charge indicates that electron transfer and ligand exchange occurred in the solution, resulting in a successful adsorption process. Studies have shown that the changes in charge and pH are caused by the complexation reaction of the material through ligand exchange within the spheres.

[0091] (2) XRD

[0092] PB-5 adsorbs phosphate and Cu 2+ XRD patterns before and after are as follows Figure 6As shown in b, new characteristic peaks appeared. The peaks at 2θ = 21.8°, 26°, and 39.2° are characteristic peaks of hydroxyapatite (HAP). Generally, when the initial phosphorus concentration is 0-100 mg / L and the Ca / P molar ratio exceeds 1.67, Ca... 2+ OH - Phosphate and phosphate can form the most stable thermodynamic phase, HAP. ICP detection results show that Ca in the solution... 2+ The content can reach 4.32 mg / L, Ca 2+ Phosphate ions react to form metal phosphates, which explains why Ca... 2+ The phosphate removal rate slightly improved with increasing concentration. The diffraction peak intensities before and after phosphate adsorption remained almost unchanged, indicating that the composite material's crystal structure remained relatively stable and unaltered. (Adsorption of Cu) 2+ The XRD patterns before and after clearly show the adsorption of Cu. 2+ The main crystal structure of the material remained unchanged. However, new characteristic peaks appeared. The peaks at 2θ = 23.8°, 31.4°, 33.5° and 35.8° were attributed to the formation of Cu(OH)2, indicating that Cu(OH)2 was generated due to surface precipitation during the reaction.

[0093] (3) FTIR

[0094] FTIR spectroscopy revealed that PB-5 adsorbed phosphate and Cu 2+ Changes in functional groups before and after. For example... Figure 6 As shown in c, the adsorption temperature was 851 cm⁻¹ before adsorption. -1 The sharp vibrational peak at 1400 cm⁻¹ is caused by the vibration of Ce-OH and La-OH bonds; -1 The vibrational peak at 1495 cm⁻¹ is caused by the vibration of the Ca-OH bond; -1 The peak is attributed to The stretching vibration is caused by the conversion of some La(OH)3 to La2(CO3)3 during the material's contact with CO2 in the air; 1576cm -1 The Ce-O bond vibration observed was attributed to Ce. 3+ Produced by reaction with ligands; at 739 cm -1 Ca-O bond vibration was observed at the site.

[0095] After the phosphate adsorption reaction, at 851 cm -1 The peaks representing Ce-OH and La-OH disappeared at 1053 cm⁻¹, while those at 1053 cm⁻¹... -1 The presence of characteristic vibrational peaks belonging to phosphorus is attributed to [the following]. Asymmetric vibration of the PO bond in the middle at 616 cm⁻¹ -1A Ce-OP group was observed at 574 cm⁻¹; -1 La-OP groups were observed at the adsorption site, confirming the successful reaction and the participation of hydroxyl groups, indicating ligand exchange during adsorption. Simultaneously, at 1400 cm⁻¹... -1 The peak at 3440 cm⁻¹ is considered a characteristic peak of calcium hydroxide. The decrease in the characteristic peak after reaction with phosphate indicates that calcium hydroxide participated in the phosphorus uptake reaction, i.e., the formation of HAP. -1 The vibrational peak at 3440 cm⁻¹ is attributed to the stretching vibration of the hydroxyl group (-OH), while the peak at 3440 cm⁻¹ is observed after adsorption. -1 The location moved to 3405cm -1 This indicates that the bonding between the ion and the hydroxyl group is formed through surface complexation, suggesting the presence of surface complexation during phosphorus adsorption. After adsorption, at 400-700 cm⁻¹... -1 The appearance of a new peak value also indicates that a complexation reaction occurred during the adsorption process.

[0096] Adsorption of Cu 2+ The FTIR spectra before and after the reaction show that the copper adsorption reaction occurred at 1100 cm⁻¹. -1 A vibrational peak belonging to copper metal ions appeared at 600 cm⁻¹; -1 The vibrational peak at that location is attributed to adsorbed Cu. 2+ The functional groups of the material subsequently changed, with hydroxyl groups participating in the reaction. At 3440 cm⁻¹ -1 The vibrational peak at 3440 cm⁻¹ is attributed to the stretching vibration of the hydroxyl group (-OH), while the peak at 3440 cm⁻¹ after adsorption is complete. -1 The location moved to 3403cm -1 This means that the bond between the ion and the hydroxyl group is formed through surface complexation, i.e., Cu 2+ It is removed by forming a complex. After adsorption, it is located at 400-700 cm⁻¹. -1 The appearance of a new peak value also indicates that a complexation reaction occurred during the adsorption process.

[0097] (4) XPS

[0098] PB-5 adsorbs phosphate and Cu 2+ XPS spectra before and after are as follows Figure 7 As shown in Figure a, peaks for C1s, O1s, Ca2p, La3d, and Ce3d can be clearly observed before adsorption. After adsorbing phosphate, PB-5 exhibits a characteristic peak for P2p, and adsorbs Cu... 2+ The appearance of the characteristic peak of Cu2p indicates that the adsorption reaction was successful.

[0099] exist Figure 8 The peaks at 835.6 eV and 839.1 eV in a represent La3d 5 / 2The peaks at 852.2 eV and 855.3 eV represent La3d 3 / 2 .like Figure 8 As shown in d, after adsorbing phosphate, La3d 5 / 2 The peaks shifted to 835.2 eV and 838.7 eV, La3d 3 / 2 The peaks shifted to 851.9 eV and 855.0 eV, with binding energies shifting by 0.4 eV and 0.3 eV, respectively. This is due to the transfer of valence electrons from La3d to form La-OP coordination complexes, attributed to La... 3+ and PO4 3- Ligand exchange occurred, consistent with previous studies, and the -OH group in La-OH can be readily replaced by phosphate species to form a complex. The spectrum of Ce3d is shown in the figure. Figure 8 The peaks at 882.6 eV and 889.2 eV in b represent Ce3d 5 / 2 The peaks located at 898.3 eV and 901.1 eV represent Ce3d. 3 / 2 The point at 885.9 eV represents the satellite peak. For example... Figure 8 As shown in e, after adsorbing phosphate, Ce3d 5 / 2 The peak shifts to 882.4 eV and 889.4 eV, Ce3d 3 / 2 The peaks shifted to 898.2 eV and 901.0 eV, shifted by 0.2 eV and 0.1 eV respectively. This can be attributed to Ca. 3+ and A Ce-OP coordination complex was formed through ligand exchange, consistent with FTIR characterization. Figure 8 As shown in c and 8f, the peak at 346.7 eV before adsorption represents Ca2p. 3 / 2 The peak at 350.3 eV represents Ca2p 1 / 2 After adsorbing phosphate, Ca2p 3 / 2 The peak shifts to 346.8 eV, Ca2p 1 / 2 The peak shifted to 350.4 eV, and the binding energy shifted by 0.1 eV. The blue shift of the Ca2p binding energy indicates that Ca... 2+ If Ca successfully combines with phosphorus, 2+ When it combines with phosphorus, it is largely due to Ca. 2+ The adsorption of phosphate groups forms hydroxyapatite, and the Ca2p spectrum of the material after adsorption is relatively disordered, indicating that the Ca content in PB-5 decreases after adsorption, and Ca successfully participates in the adsorption, which is consistent with the previous study.

[0100] like Figure 8 As shown in gi, Cu adsorption 2+ After that, La3d 5 / 2The peaks shifted to 835.1 eV and 838.6 eV, La3d 3 / 2 The peaks shifted to 851.9 eV and 855.0 eV, with binding energies shifting by 0.5 eV and 0.3 eV, respectively. Ce3d 5 / 2 The peaks shifted to 883.2 eV and 889.8 eV, Ce3d 3 / 2 The peaks shifted to 898.4 eV and 901.2 eV, with binding energies shifting by 0.6 eV and 0.1 eV, respectively. (Ca2p) 3 / 2 The peak shifts to 347.0 eV, Ca2p 1 / 2 The peak shifted to 350.3 eV, and the binding energy shifted by 0.3 eV. The shift in binding energy is attributed to electron transfer from La, Ce, and Ca elements, resulting in the formation of new complexes. This is due to the interaction between the hydroxyl and oxide groups on the surface of the composite material and Cu. 2+ A complexation reaction occurs. Figure 7 The peak at 940.3 eV in c is a satellite peak, indicating that the adsorption process has been completed. The peaks at 934.9 eV and 943.7 eV are attributed to Cu2p. 3 / 2 The peaks at 954.6 and 962.6 eV are attributed to Cu2p. 1 / 2 This result indicates that Cu(OH)2 was formed during the adsorption process. Based on previous studies, Cu... 2+ The removal is accompanied by the formation of Cu hydroxide, which reacts with -OH groups on the material surface. 2+ It precipitates onto PB-5.

[0101] (5) Reusability

[0102] In this part of the experiment, a relatively high initial concentration of contaminants was set to ensure that all adsorption sites on the material were occupied. During the elution process, a 2 mol / L NaOH solution was used to elute the adsorbed material. Figure 9 As shown in Figure a, the adsorption efficiency of the material decreases with increasing number of analyses. Even after three analyses, the phosphate removal efficiency remains above 60%, while Cu... 2+ The removal efficiency can be maintained at around 80%, indicating that PB-5 has good recyclability.

[0103] (6) Environmental stability of materials

[0104] like Figure 9As shown in b, when the pH value is greater than 4, the release of La and Ce in the solution after the reaction is 0, and the release gradually decreases as the pH value increases within the range of 1-3. At pH=3, the release of La after phosphate adsorption is 0.05 mg / L, and the release of Ce is 0.03 mg / L. Currently, the dietary intake of lanthanum for adults in my country is 0.485 μg / kg BW. Based on the average Chinese body weight of approximately 33 kg, the intake of lanthanum for adults is approximately 95.70 mg. Since 70% of a person's body weight is liquid, i.e., a liquid volume of 46 liters, this means that the concentration of lanthanum in the human body through diet can reach 33.95 mg / L. In fact, lanthanum does not easily accumulate in the human body and mainly accumulates in human excrement. Currently, there is no evidence of poisoning from insoluble or soluble lanthanum. As for cerium, there is currently no unified limit on the concentration of cerium release causing environmental pollution, and there have been no reported incidents of low concentrations of La and Ce causing environmental harm. In practical applications, maintaining a pH ≥ 3 will prevent the material from causing secondary pollution to the environment.

[0105] (7) Actual wastewater verification

[0106] Figure 10 The results showed that PB-5 is effective against phosphate and Cu. 2+ The simultaneous removal effect in actual wastewater was demonstrated. At 25℃ and a dosage of 1 g / L, both pollutants were completely removed within 30 minutes, indicating that PB-5 effectively removes phosphates and Cu. 2+ It has excellent removal effect on actual wastewater.

[0107] IV. Conclusion

[0108] This study prepared a material for adsorbing phosphates and Cu from water using waste polishing powder and shell powder at a mass ratio of 5:1. 2+ The composite material PB-5 contains rare earth elements (La, Ce) from waste polishing powder and Ca from shell powder. 2+ It exists in the form of hydroxide in the PB-5 composite, which is a mesoporous composite material with an average pore size of 9.658 nm and a molecular weight of 134.655 nm. 2 Large specific surface area per g. For phosphates and Cu 2+ Adsorption was completed rapidly within 30 minutes, and adsorption equilibrium was reached within 180 minutes. (This refers to the removal of coexisting ions in water.) Besides affecting phosphate adsorption, other coexisting ions also affect phosphate and Cu. 2+ The adsorption process was not significantly affected, but the adsorption capacity was strongly dependent on pH. At 25℃, the highest adsorption capacities for phosphate and copper ions were 66.26 mg / g and 79.34 mg / g, respectively, at pH 3 and 6. Furthermore, the adsorbent exhibits excellent recyclability; actual wastewater verification experiments demonstrated that PB-5 effectively adsorbs phosphate and copper ions.2+ It has excellent removal effect, and maintaining a pH ≥ 3 during actual use will not cause secondary pollution to the environment.

[0109] Adsorption mechanism studies have shown that phosphate and Cu 2+ The adsorption of these substances is all monolayer chemisorption, and the adsorption mechanism includes electrostatic attraction, surface precipitation, and surface complexation. PB-5 is low in cost, simple to synthesize, and highly efficient and environmentally friendly; therefore, PB-5 is expected to become a highly efficient and promising adsorbent.

[0110] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-mentioned technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by substituting the above-mentioned features with technical features disclosed in this application (but not limited to) that have similar functions.

Claims

1. A composite material of waste polishing powder and shell powder, characterized in that, The composite material is made from waste polishing powder and shell powder in a mass ratio of 5:

1. Its preparation method includes the following steps: Waste polishing powder was placed in sulfuric acid solution and pyrolyzed with magnetic stirring at 60°C. After the reaction was completed, the undissolved substances were filtered out and the mixture was cooled to room temperature. The pH value was then adjusted to above 2. Add shell powder, ultrasonically clean, and magnetically stir while adding alkaline solution to adjust the pH value to be greater than 11. Stir magnetically at 60℃. After the reaction is completed, cool to room temperature and wash until it shows neutral. Dry and grind to obtain waste polishing powder-shell powder composite material. The waste polishing powder is CeLa2O3F3.

2. The method for preparing the waste polishing powder-shell powder composite material according to claim 1, characterized in that, Includes the following steps: Waste polishing powder was placed in sulfuric acid solution and pyrolyzed with magnetic stirring at 60°C. After the reaction was completed, the undissolved substances were filtered out and the mixture was cooled to room temperature. The pH value was then adjusted to above 2. Shell powder was added, and after ultrasonic cleaning, an alkaline solution was added to adjust the pH value to be greater than 11 while magnetic stirring was performed. The mixture was magnetically stirred at 60°C. After the reaction was completed, it was cooled to room temperature and washed until it showed a neutral pH. The mixture was then dried and ground to obtain a waste polishing powder-shell powder composite material.

3. The method for preparing the waste polishing powder-shell powder composite material according to claim 2, characterized in that, The magnetic stirring time is 2 hours.

4. The method for preparing the waste polishing powder-shell powder composite material according to claim 2, characterized in that, The ultrasonic cleaning time is 10 minutes.

5. The method for preparing the waste polishing powder-shell powder composite material according to claim 2, characterized in that, The shell powder is shell powder that has passed through a 200-mesh sieve, and the waste polishing powder-shell powder composite material is ground and then passed through a 200-mesh sieve.

6. The method for preparing the waste polishing powder-shell powder composite material according to claim 2, characterized in that, The alkaline solution is sodium hydroxide.

7. The application of the waste polishing powder-shell powder composite material according to claim 1 or the waste polishing powder-shell powder composite material prepared by the preparation method according to any one of claims 2-6 in wastewater treatment.

8. The application according to claim 7, characterized in that, The wastewater contains phosphates and heavy metal ions.

Images