A polyaluminum ferric titanium sulfate coagulant and its preparation method

Abstract

This invention relates to the field of coagulant technology and discloses a polyaluminum ferric silicate coagulant and its preparation method, comprising the following steps: S1 coal gangue is calcined to obtain modified coal gangue; S2 modified coal gangue is acid-leached to obtain coal gangue acid leaching solution; S3 the coal gangue acid leaching solution is subjected to titanium doping, pH adjustment, polymerization, centrifugation, and aging to obtain the coagulant. The preparation method provided by this invention, after activation and modification, undergoes acid leaching, polymerization, centrifugation, aging, and drying to prepare the polyaluminum ferric silicate coagulant. By optimizing the calcination temperature, modification ratio, acid concentration, polymerization pH, polymerization temperature, and polymerization time, the coagulation performance of the coagulant can be improved, thereby increasing the wastewater pollutant removal rate.

Description

Technical Field

[0001] This invention relates to the field of coagulant technology, and more specifically, to a polyaluminum ferric titanium silicate coagulant and its preparation method. Background Technology

[0002] Coagulation or flocculation is the most commonly used technology for treating pollutants in wastewater. Its purpose is to aggregate fine organic or inorganic particles (such as colloids and suspended particles) in raw water into large flocs for subsequent removal through sedimentation and filtration. During this process, some soluble substances, such as natural organic matter (NOM) and metal ions, can also be removed. Coagulants are diverse, including natural coagulants, metal coagulants, and mixed coagulants, but due to cost and efficiency considerations, aluminum and iron salt coagulants are currently the most widely used in my country. However, aluminum and iron salt coagulants still have drawbacks. Residual aluminum in water treated with aluminum salt coagulants can be harmful to human health, while water treated with iron salt coagulants has higher color and corrosiveness, causing certain impacts on water treatment processes. Furthermore, with the continuous improvement of drinking water hygiene standards, seeking inexpensive and efficient coagulants is an inevitable path for coagulation-based water treatment.

[0003] In recent years, titanium salts have been increasingly used as raw materials for coagulant preparation, attracting widespread attention. The hydrolysis and coagulation processes of titanium salt coagulants differ from those of other inorganic salt coagulants. Titanium coagulants produce superior flocs with characteristics such as low-temperature turbidity, low effluent toxicity, and significantly lower residual aluminum and iron concentrations in the coagulated effluent compared to aluminum / iron coagulants. Therefore, titanium coagulants can overcome the shortcomings of traditional aluminum / iron coagulants, particularly the health risks posed by residual aluminum and the side effects of iron on subsequent water treatment systems. Summary of the Invention

[0004] The technical problem solved by this invention:

[0005] This invention provides a polyaluminum ferro-titanium silicate coagulant prepared from coal gangue, thereby realizing the development and utilization of coal gangue and achieving low cost and high efficiency of the coagulant.

[0006] The technical solution adopted in this invention is as follows:

[0007] First, the present invention provides a method for preparing a polyaluminum ferric titanium silicate coagulant, comprising the following steps:

[0008] S1 coal gangue is roasted to obtain modified coal gangue;

[0009] S2 modified coal gangue is acid leaching to obtain coal gangue acid leaching solution;

[0010] S3 coal gangue acid leaching solution is processed by titanium doping, pH adjustment, polymerization, centrifugation, and aging to obtain a coagulant.

[0011] According to some preferred embodiments, coal gangue sieved through a 200-mesh sieve is calcined with anhydrous calcium carbonate and anhydrous sodium carbonate to obtain modified coal gangue. The mass ratio of anhydrous calcium carbonate and anhydrous sodium carbonate to coal gangue is 0.4~1.4:1, and the calcination temperature is 750~1000℃. Specifically, the modification ratio can be 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1, or 1.4:1; the specific calcination temperature can be 750, 800, 850, 900, 950, or 1000℃. The mass ratio of anhydrous calcium carbonate to anhydrous sodium carbonate is 1:1.

[0012] According to some more preferred embodiments, the mass ratio of anhydrous calcium carbonate and anhydrous sodium carbonate to coal gangue is 1:1, and the calcination temperature is 850°C.

[0013] According to some preferred embodiments, the acid leaching treatment involves an acid concentration of 2-7 mol / L, a leaching time of 1.5-4 h, and a leaching temperature of 60-90 °C. Specifically, the acid concentration can be 2, 3, 4, 5, 6, or 7 mol / L; the leaching time can be 1.5, 2, 2.5, 3, 3.5, or 4 h.

[0014] According to some preferred embodiments, the acid leaching treatment is performed with an acid concentration of 4 mol / L and a leaching time of 3 h.

[0015] According to some preferred embodiments, titanium doping involves adding titanium tetrachloride for doping, adjusting the pH to 0.5-3 with sodium hydroxide, and carrying out the polymerization reaction at 40-90°C for 1-6 hours. The polymerization pH can specifically be 0.5, 1, 1.5, 2, 2.5, or 3. The polymerization temperature can specifically be 40, 50, 60, 70, 80, or 90°C. The polymerization time can specifically be 1, 2, 3, 4, 5, or 6 hours.

[0016] According to some preferred embodiments, the pH value is adjusted to 1.5, and the polymerization reaction is carried out at 70°C.

[0017] According to some preferred embodiments, the curing process is carried out at 30~50℃ for 10~15 hours.

[0018] Second, the present invention provides a polyaluminum ferric titanium silicate coagulant obtained by the aforementioned preparation method.

[0019] The beneficial effects achieved by this invention are as follows:

[0020] The polyaluminum ferric silicate coagulant provided by this invention is prepared from coal gangue. After activation treatment, the crystalline state inside the coal gangue is converted to an amorphous state, while also exhibiting a large specific surface area and high chemical activity. Following activation and modification, the coagulant undergoes acid leaching, polymerization, centrifugation, aging, and drying to obtain the polyaluminum ferric silicate coagulant. By optimizing the calcination temperature, modification ratio, acid concentration, polymerization pH, polymerization temperature, and polymerization time, the coagulation performance of the coagulant can be improved, thereby enhancing the wastewater pollutant removal rate. Attached Figure Description

[0021] Figure 1 The graph shows the effect of calcination temperature on the leaching rates of iron, aluminum, and silicon.

[0022] Figure 2 The graph shows the results of the leaching rates of iron, aluminum, and silicon compared to the modified product.

[0023] Figure 3 The graph shows the effect of acid concentration on the leaching rates of iron, aluminum, and silicon.

[0024] Figure 4 The graph shows the effect of acid leaching time on the leaching rates of iron, aluminum, and silicon.

[0025] Figure 5 The effect of calcination temperature on turbidity (a) and UV 254 (b) COD Cr (c) Graph showing the removal rate;

[0026] Figure 6 To modify and compare turbidity (a) and UV 254 (b) COD Cr (c) Graph showing the removal rate;

[0027] Figure 7 The effect of acid concentration on turbidity (a) and UV 254 (b) COD Cr (c) Graph showing the removal rate;

[0028] Figure 8 The effect of acid leaching time on turbidity (a) and UV 254 (b) COD Cr (c) Graph showing the removal rate;

[0029] Figure 9 To polymerize the effect of pH on turbidity (a) and UV. 254 (b) COD Cr (c) Graph showing the removal rate;

[0030] Figure 10 The effect of polymerization temperature on turbidity (a) and UV 254 (b) COD Cr (c) Graph showing the removal rate;

[0031] Figure 11 The effect of polymerization time on turbidity (a) and UV 254 (b) COD Cr (c) Graph showing the removal rate;

[0032] Figure 12 This is a flowchart of the Fe2O3 detection method;

[0033] Figure 13 This is a flowchart of the Al2O3 detection method;

[0034] Figure 14 This is a flowchart of the SiO2 detection method;

[0035] Figure 15 This is a flowchart of the CODcr determination process. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0037] In this invention, the coal gangue used is taken from the gangue mountain in Panzhihua City, Sichuan Province. The main mineral phases of the coal gangue are quartz, calcite, kaolin and montmorillonite mixed layer. The main chemical components are shown in Table 1.

[0038] Table 1 Chemical composition of coal gangue raw material

[0039]

[0040] This invention uses coal gangue as raw material to prepare polyaluminum ferrosilicon sulfate titanium through thermal activation, acid leaching, polymerization, centrifugation, and aging.

[0041] Step 1: Activation of coal gangue by roasting

[0042] Because coal gangue itself has low activity, the ion precipitation rate is not high during direct acid leaching. Therefore, the coal gangue is activated before acid leaching. Coal gangue that has passed through a 200-mesh sieve is mixed evenly with anhydrous calcium carbonate and anhydrous sodium carbonate (mass ratio 1:1), placed in a crucible, and then calcined in a muffle furnace. The mixture is calcined at a predetermined temperature for 2 hours at a controlled heating rate. The calcined coal gangue is then removed and allowed to cool naturally to obtain activated modified coal gangue powder.

[0043] Step 2: Acid leaching of coal gangue

[0044] Sulfuric acid is used for acid leaching because hydrochloric acid is volatile and has a poor leaching effect. Coal gangue contains clay minerals (Al₂O₃·2SiO₂·2H₂O). At high temperatures, a certain concentration of acid can increase the leaching rate of Al₂O₃, and the following reaction will occur:

[0045] Al2O3·2SiO2·2H2O +3H2SO4→Al2(SO4)3+2H2SiO3+3H2O

[0046] The main reaction that occurs between sulfuric acid and Fe2O3 in the leaching of coal gangue is:

[0047] Fe₂O₃ + H₂SO₄ → Fe₂(SO₄)₃ + H₂O

[0048] First, weigh 20g of activated and modified coal gangue powder and place it in a 300ml conical flask using weighing paper. Add a certain proportion of sulfuric acid solution. Place a magnetic rotor in a beaker, seal the mouth of the beaker with plastic wrap, and then place it in a constant temperature water bath and stir for a period of time. After removing it, pour it into a centrifuge tube and centrifuge at 4000 r / min for 5 min to separate the solid and liquid. Pour out the liquid in the centrifuge tube; this is the acid leaching solution. Complexometric titration of the acid leaching solution can determine the content of metal ions and the leaching rate.

[0049] Step 3: Preparation of polyaluminum iron titanium silicate sulfate

[0050] The modified coal gangue, after acid leaching, was mixed with titanium tetrachloride solution in a 100ml beaker at a specific iron-titanium ratio. The pH of the mixed solution was adjusted to a preset value of 1.5 using 400g / L NaOH. A magnetic rotor was added, the mixture was sealed with plastic wrap, and placed in a magnetically stirred tank at a preset temperature for polymerization for a period of time. After polymerization, the sample solution was poured from the beaker into a centrifuge tube and centrifuged at 4000 r / min for 5 min. The supernatant was collected and placed in a 100ml beaker for constant temperature curing for a period of time. After curing, the sample was removed and dried in an oven at 105℃. After drying, the sample was ground to obtain the polyaluminum silicate iron titanium sulfate (PSAFT) product.

[0051] The polyaluminum iron titanium silicate prepared above was subjected to a coagulation experiment.

[0052] Preparation of simulated wastewater: Take the experimental kaolin stock solution and dilute it with ultrapure water to 1L, making the turbidity of the solution reach 100±5 NTU to obtain simulated wastewater; then weigh 0.2125g of dried potassium hydrogen phthalate and add it to the prepared simulated wastewater, shake thoroughly, and set aside. The COD of this simulated wastewater is... Cr The theoretical value is 500mg Finally, the UV radiation of the simulated wastewater could be measured using a laboratory spectrophotometer.254 The absorbance is 2.168 ± 0.002 Abs.

[0053] Coagulation experiment: 300 ml of simulated wastewater was pipetted into a 500 ml beaker, and an appropriate amount of PSAFT was added. The pH was adjusted to 8 with 0.5 mol / L sulfuric acid solution or sodium hydroxide solution. The mixture was then stirred rapidly for 60 s and slowly for 600 s using a JJ-4 six-stage stirrer, after which the stirrer was removed. After standing for 1800 s, the supernatant of the wastewater was collected for water quality index determination.

[0054] Methods for detecting metals in coal gangue acid leaching solution: The methods for detecting metal ions in coal gangue acid leaching solution shall be in accordance with the methods in GB / T14563-2020.

[0055] (1) The detection method and procedure for Fe2O3 are as follows: Figure 12 As shown.

[0056] The formula for calculating Fe2O3 content is as follows:

[0057]

[0058] (2) The detection method and procedure for Al2O3 are as follows: Figure 13 As shown.

[0059] Formula for calculating Al2O3 content:

[0060]

[0061] (3) The detection method and procedure for SiO2 are as follows: Figure 14 As shown.

[0062] The formula for calculating SiO2 content is as follows:

[0063]

[0064] Determination of water quality indicators:

[0065] (1) Measurement of turbidity

[0066] Take an appropriate amount of water sample into a turbidity vial and measure it using a digital turbidity meter. Wait until the data on the turbidity meter stops fluctuating before taking the reading. The data in that zone is the turbidity.

[0067] (2) UV 254 Measurement

[0068] The absorbance of the supernatant was measured at 254 nm using a UV spectrophotometer; this absorbance is the UV value. 254 .

[0069] (3) The procedure for determining CODcr is as follows: Figure 15 As shown.

[0070] The formula for calculating CODcr content is as follows:

[0071]

[0072] Experiment 1: Effect of different calcination temperatures on metal ion leaching rate

[0073] 20g of activated coal gangue was used for acid leaching experiments under the conditions of an acid concentration of 6mol / L, an acid leaching time of 2.5h, and an acid leaching temperature of 75℃. The roasting temperatures were varied (750℃, 800℃, 850℃, 900℃, 950℃, 1000℃). The contents of iron ions, aluminum ions, and silicon ions in the acid leaching solution were measured. The experimental results are as follows: Figure 1 As shown.

[0074] Depend on Figure 1 The results show that the leaching rates of ferric oxide and aluminum oxide increase with increasing calcination temperature, reaching their highest values ​​at 850℃, with ferric oxide reaching 35.69% and aluminum oxide reaching 35.27%. The leaching rate of silica also increases with increasing calcination temperature; since the calcination temperature in this experiment was 1000℃, the silica leaching rate was highest at 1000℃. The total metal ion concentration reached a maximum of 7.589 g / mL at 850℃. This may be because roasting coal gangue makes it more porous. Under high-temperature roasting, the internal crystal structure of coal gangue changes from crystalline to amorphous. Kaolinite has a large specific surface area and high chemical reactivity, which allows aluminum oxide to be leached by acid. However, as the temperature continues to rise, mullite and quartz are formed, leading to a decrease in the activity of coal gangue and a drop in the leaching rate of metal ions. In summary, at a calcination temperature of 800℃, the iron ion content is 1.82%, the aluminum ion content is 5.47%, and the silicon ion content is 0.299%.

[0075] Experiment 2: Effect of Modification Ratio on Metal Ion Leaching

[0076] 20g of activated coal gangue was used in an acid leaching experiment under the following conditions: calcination temperature of 850℃, acid concentration of 6mol / L, acid leaching time of 2.5h, and acid leaching temperature of 75℃. The ratio of calcium carbonate to sodium carbonate was varied (0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.4:1). The content of metal ions in the acid leaching solution was determined. The experimental results are as follows: Figure 2 As shown.

[0077] Depend on Figure 2The results showed that the leaching rates of ferric oxide, aluminum oxide, and silicon dioxide increased with the increase of the calcium carbonate and sodium carbonate modification ratio. At a 1:1 ratio, both the leaching rate and the total metal ion concentration reached their highest levels, with ferric oxide reaching 59.42%, aluminum oxide reaching 54.5%, and silicon dioxide reaching 0.0133%. The total metal ion concentration reached 11.851 g / mL. This situation may occur when the content of calcium carbonate and sodium carbonate is low, preventing them from fully mixing and reacting with the coal gangue. This results in less CO2 production, leading to a smaller specific surface area of ​​the coal gangue. Furthermore, the poor solubility of coal gangue in acid prevents the sufficient extraction of iron and aluminum ions through acid leaching. The presence of calcium carbonate and sodium carbonate promotes the forward reaction of the coal gangue acid leaching. After a ratio of 0.6:1, the ion leaching rate rapidly increases, reaching equilibrium at a ratio of 1:1, where the ion leaching rate peaks. After 1:1, due to excess calcium carbonate and sodium carbonate, some cannot mix with the coal gangue to react, and the ion leaching rate tends to return to equilibrium. In summary, a modification ratio of 1:1 yields the optimal metal ion leaching rate, at which the iron ion leaching rate is 3.02%, aluminum ion leaching rate is 8.45%, and silicon ion leaching rate is 0.381%.

[0078] Experiment 3: Effect of acid concentration on metal ion leaching rate

[0079] 20g of activated coal gangue was used for acid leaching experiments under the following conditions: calcination temperature of 850℃, modification ratio of 1:1, acid leaching time of 2.5h, and acid leaching temperature of 85℃. The acid concentration was varied (2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L). The content of metal ions in the acid leaching solution was determined. The experimental results are as follows: Figure 3 As shown.

[0080] Depend on Figure 3The results showed that the leaching rates of ferric oxide, aluminum oxide, and silica increased with increasing sulfuric acid concentration, reaching their highest values ​​at 4 mol / L. The leaching rates of ferric oxide reached 38.65%, aluminum oxide 53.57%, and silica 0.02%, while the total ion concentration reached 10.806 g / mL. Beyond 4 mol / L, the leaching rate of metal ions decreased over time, and the increase in the total metal ion concentration slowed. This may be because sulfate ions can enhance the charge neutralization and adsorption bridging ability of copolymers such as iron and aluminum ions, thereby strengthening the coagulation ability of aluminum and iron. It can increase the degree of polymerization of these copolymers, increasing their charge number, making it easier for them to combine with negatively charged particles to form flocs during coagulation. The flocculation process involves continuous combination and growth, eventually leading to sedimentation. The removal rate reached its highest value at 4 mol / L. However, when the amount of sulfate introduced is too large, its stability will change, and precipitation is easily formed, leading to a decrease in the leaching rate of metal ions. In summary, the ion leaching rate is optimal at an acid concentration of 4 mol / L, at which point the leaching rates are 1.97% for iron ions, 8.3% for aluminum ions, and 0.536% for silicon ions.

[0081] Experiment 4: Effect of acid leaching time on metal ion leaching rate

[0082] 20g of activated coal gangue was used in an acid leaching experiment under the following conditions: roasting temperature of 850℃, modification ratio of 1:1, acid leaching temperature of 85℃, and acid concentration of 4mol / L. The leaching time was varied (1.5h, 2h, 2.5h, 3h, 3.5h, 4h). The content of metal ions in the acid leaching solution was determined. The experimental results are as follows: Figure 4 As shown.

[0083] Depend on Figure 4 The results showed that the leaching rates of ferric oxide, aluminum oxide, and silicon dioxide increased with increasing acid leaching time, reaching their highest values ​​at 3 hours. The leaching rates of ferric oxide reached 40.58%, aluminum oxide 43%, and silicon dioxide 0.021%, while the total metal ion concentration reached 9.257 g / mL. As the acid concentration continued to increase, the leaching rates of iron, aluminum, and silicon ions began to decrease, while the increase and decrease of the total metal ion concentration became gradual. This may be because when the acid leaching time is less than 3 hours, iron and aluminum ions react with sulfate ions (SO42-) during the reaction. 2-The reaction produces insoluble salts, which enter the filter residue and are separated after centrifugation. This results in a low leaching rate of iron and aluminum ions. After 3 hours, iron and aluminum ions may react with residual sulfate ions to form corresponding complex complexes, which remain in the acid leaching solution obtained after centrifugation. Since this experiment uses complexometric titration with EDTA, the stability of these complex complexes with iron and aluminum ions is much higher than the stability of the complexes formed between EDTA and iron and aluminum ions. During titration, EDTA cannot titrate and measure the portion of iron and aluminum ions that form complex complexes, leading to a decrease in the leaching rate of metal ions. In summary, the optimal ion leaching rate is achieved when the acid leaching time is 3 hours, at which point the leaching rates are 2.06% for iron ions, 6.67% for aluminum ions, and 0.527% for silicon ions.

[0084] Experiment 5: Effect of calcination temperature on the coagulation effect of PSAFT

[0085] 20g of activated coal gangue was used for acid leaching experiments at different roasting temperatures (750℃, 800℃, 850℃, 900℃, 950℃, and 1000℃) under conditions of 6mol / L acid concentration, 2.5h acid leaching time, and 75℃ acid leaching temperature. 20ml of the acid leaching solution was used, and titanium tetrachloride was added according to a specific iron-titanium ratio. The pH was adjusted to 1.5 with 400g / L sodium hydroxide. Polymerization was carried out at 70℃. After polymerization, the beaker was removed and placed in a 40℃ water bath for 12h for curing. Coagulation experiments were then performed on PSAFT polymerized at different polymerization temperatures. The results are as follows: Figure 5 As shown.

[0086] Depend on Figure 5 It is evident that the removal rate of pollutants in wastewater increases with the increase of coal gangue roasting temperature, reaching its peak at 850℃. This may be because roasting coal gangue makes it more porous. Under high-temperature roasting, the internal crystal structure of coal gangue changes from crystalline to amorphous. Kaolinite has a large specific surface area and high chemical reactivity, enabling acid leaching of alumina. However, as the temperature continues to rise, mullite and quartz are formed, reducing the activity of coal gangue and decreasing the leaching rate of metal ions. In conclusion, the optimal removal rate of pollutants in wastewater is achieved at a roasting temperature of 850℃. At this temperature, the COD... Cr UV 254 The removal rates of turbidity were 40.93%, 34.29%, and 95.9%, respectively.

[0087] Experiment 6: Effect of Modification Ratio on PSAFT Coagulation Performance

[0088] 20g of activated coal gangue was used for acid leaching experiments under the following conditions: calcination temperature of 850℃, acid concentration of 6mol / L, acid leaching time of 2.5h, and acid leaching temperature of 75℃. The modification ratios were varied (0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.4:1). 20ml of the acid leaching solution was used to add titanium tetrachloride according to a specific iron-titanium ratio. The pH was adjusted to 1.5 with 400g / L sodium hydroxide. Polymerization was carried out at 70℃. After polymerization, the beaker was removed and placed in a 40℃ water bath for 12h for curing. Coagulation experiments were then performed on PSAFT polymerized at different polymerization temperatures. The results are as follows: Figure 6 As shown.

[0089] Depend on Figure 6 The results show that the removal rate of pollutants in wastewater increases with the increase of the coal gangue modification ratio, and the highest pollutant removal rate is achieved at a modification ratio of 1:1. The leaching rate of Si is very low, while the leaching rates of iron and aluminum ions increase continuously with the increase of the modification ratio. When the content of calcium carbonate and sodium carbonate is low, calcium carbonate and sodium carbonate cannot fully mix with coal gangue to react, resulting in less CO2 generation. This leads to a smaller specific surface area of ​​coal gangue, making it difficult for iron and aluminum ions to be fully extracted by acid leaching. The presence of calcium carbonate and sodium carbonate can promote the acid leaching reaction of coal gangue. After a modification ratio of 0.6:1, the ion leaching rate increases rapidly, and reaches equilibrium at a ratio of 1:1, where the ion leaching rate reaches its peak. After a ratio of 1:1, due to excess calcium carbonate and sodium carbonate, some cannot mix with coal gangue to react, and the ion leaching rate tends to reach equilibrium. In conclusion, the optimal pollutant removal rate in wastewater is achieved at a modification ratio of 1:1. At this point, the COD... Cr UV 254 The removal rates of turbidity were 36.83%, 37.81%, and 96.6%, respectively.

[0090] Experiment 7: Effect of acid concentration on PSAFT coagulation effect

[0091] 20g of activated coal gangue was used for acid leaching experiments under the following conditions: roasting temperature of 850℃, modification ratio of 1:1, acid concentration of 6mol / L, acid leaching time of 2.5h, and acid leaching temperature of 75℃. The acid concentrations were varied (2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, and 7 mol / L). 20ml of the acid leaching solution was used to add titanium tetrachloride according to a specific iron-titanium ratio. The pH was adjusted to 1.5 with 400g / L sodium hydroxide. The polymerization reaction was carried out at 70℃. After the polymerization reaction, the beaker was removed and placed in a 40℃ water bath for 12h for curing. Coagulation experiments were then performed on PSAFT polymerized at different polymerization temperatures. The results are as follows: Figure 7 As shown.

[0092] Depend on Figure 7The results show that the removal rate of pollutants in wastewater increases with increasing acid concentration, reaching its peak at an acid concentration of 4 mol / L. This is likely because sulfate ions enhance the charge neutralization and adsorption bridging capabilities of copolymers such as iron and aluminum ions, thereby strengthening the coagulation ability of aluminum and iron. Sulfate ions can increase the degree of polymerization of these copolymers, increasing their charge number, making it easier for them to combine with negatively charged particles to form flocs during coagulation. These flocs continuously combine, grow, and eventually settle. The removal rate is highest at 4 mol / L. However, when the amount of sulfate ions introduced is too large, their stability changes, leading to precipitation and a decrease in the removal rate of wastewater pollutants. In conclusion, the optimal removal rate of pollutants in wastewater is achieved at an acid concentration of 4 mol / L. At this concentration, the COD... Cr UV 254 The removal rates of turbidity were 57.33%, 38.5%, and 95.69%, respectively.

[0093] Experiment 8: Effect of acid leaching time on PSAFT coagulation effect

[0094] 20g of activated coal gangue was used for acid leaching experiments under the following conditions: roasting temperature of 850℃, modification ratio of 1:1, acid concentration of 6mol / L, acid leaching temperature of 70℃, and acid concentration of 4mol / L. The leaching time was varied (1.5h, 2h, 2.5h, 3h, 3.5h, 4h). 20ml of the leaching solution was used to add titanium tetrachloride according to a specific iron-titanium ratio. The pH was adjusted to 1.5 with 400g / L sodium hydroxide. The polymerization reaction was carried out at 70℃. After the polymerization reaction, the beaker was removed and placed in a 40℃ water bath for 12h for curing. Coagulation experiments were then performed on PSAFT polymerized at different polymerization temperatures. The results are as follows: Figure 8 As shown.

[0095] Depend on Figure 8 The results showed that the removal rate of pollutants in wastewater increased with the increase of acid leaching time, reaching its highest level at 3 hours. This may be because when the acid leaching time is less than 3 hours, iron and aluminum ions react with sulfate ions (SO42-) during the reaction process. 2- The reaction produces insoluble salts that enter the filter residue and are separated after centrifugation. This results in a low leaching rate of iron and aluminum ions. After 3 hours, iron and aluminum ions may react with residual sulfate ions to form complex complexes, which remain in the acid leaching solution obtained after centrifugation. Since this experiment uses EDTA for complexometric titration, these complex complexes are more stable than the complexes formed by EDTA and ions, making accurate titration impossible. This leads to a decrease in the removal rate of pollutants in the wastewater. In conclusion, the optimal pollutant removal rate in wastewater is achieved when the acid leaching time is 3 hours. At this time, the COD... Cr UV 254The removal rates of turbidity were 77.6%, 36.21%, and 96.03%, respectively.

[0096] Experiment 9: Effect of polymerization pH on PSAFT coagulation effect

[0097] 20 ml of coal gangue acid leaching solution was added to titanium tetrachloride according to a specific iron-titanium ratio. The pH was adjusted using sodium hydroxide (0.5, 1, 1.5, 2, 2.5, 3). The reaction was carried out at 70℃ for 2.5 h. After the polymerization reaction was completed, the beaker was removed and placed in a 40℃ water bath for 12 h of curing. Coagulation experiments were then performed on PSAFT polymerized at different polymerization temperatures. The results are as follows: Figure 9 As shown.

[0098] Depend on Figure 9 The results show that the removal rate of pollutants in wastewater increases with the increase of polymerization pH, reaching its highest at a polymerization pH of 1.5. This may be because, with increasing pH, Ala and Fea, which determine the performance of coagulants, gradually transform into Alb and Feb or Alc and Fec. The charge neutralization, adsorption bridging, and entrapment sweeping effects of the coagulated samples are all enhanced. Under these conditions, the colloids in the wastewater deviate from steady-state equilibrium, resulting in a higher removal rate of pollutants. As the pH continues to rise, the Alc produced in the coagulant is positively correlated with the increase or decrease in the alkalinity of the polymerization solution. Therefore, the hydrolysis of Al and Fe proceeds in the direction of Alc formation, leading to the formation of sodium hydroxide sol precipitate. The molecular chain coiling weakens the bridging effect, resulting in poorer coagulation performance of the coagulant and a lower removal rate of pollutants in the wastewater. In conclusion, the optimal removal rate of pollutants in wastewater is achieved at a polymerization pH of 1.5. At this pH, the removal rate of COD from the wastewater is significantly improved. Cr UV 254 The turbidity removal rates were 62.4%, 37.2%, and 96.84%, respectively.

[0099] Experiment 10: Effect of polymerization temperature on the coagulation effect of PSAFT

[0100] Take 20 ml of coal gangue acid leaching solution, add titanium tetrachloride according to a certain iron-titanium ratio, adjust the pH to 1.5 with 400 g / L sodium hydroxide, and perform polymerization reactions for 2.5 h at different polymerization temperatures (40℃, 50℃, 60℃, 70℃, 80℃, 90℃). After the polymerization reaction is completed, remove the beaker and place it in a 40℃ water bath for 12 h for curing. Then, perform coagulation experiments on PSAFT polymerized at different polymerization temperatures. The results are as follows. Figure 10 As shown.

[0101] Depend on Figure 10The results show that the removal rate of pollutants in wastewater increases with increasing polymerization temperature, reaching its highest level at 70℃. This is likely because, from 40℃ to 70℃, the polymerization rate accelerates, increasing the hydroxyl content of the copolymer, lengthening the copolymer chains, and enhancing adsorption bridging, trapping, and sweeping effects, thus increasing the degree of polymerization of the coagulant and improving coagulation performance. After reaching 70℃, the polymerization reaction reaches equilibrium, but the alkalinity increases, causing metal ions to transform towards Alc and Fec. These polymers are less stable, leading to a decrease in the degree of polymerization of the coagulant sample and consequently a decrease in wastewater removal rate. In conclusion, the optimal pollutant removal rate is achieved at a polymerization temperature of 70℃. At this temperature, the COD of the wastewater pollutant... Cr UV 254 The turbidity removal rates were 47.2%, 36.8%, and 94.68%, respectively.

[0102] Experiment 11: Effect of polymerization time on PSAFT coagulation effect

[0103] Take 20 ml of coal gangue acid leaching solution, add titanium tetrachloride according to a certain iron-titanium ratio, adjust the pH to 1.5 with 400 g / L sodium hydroxide, and polymerize at 70℃. Polymerization reactions were carried out at different times (1 h, 2 h, 3 h, 4 h, 5 h, 6 h). After the reaction, the beaker was removed and placed in a 40℃ water bath for 12 h to mature. Coagulation experiments were then performed on PSAFT polymerized at different pH values. The results are as follows: Figure 11 As shown.

[0104] Depend on Figure 11 The results showed that the removal rate of pollutants in the wastewater increased with increasing polymerization time, reaching its highest point at 3 hours. This is likely because, from 1 hour to 3 hours, the polymer chain length of the coagulant increases with the extension of polymerization time, forming hydroxyl copolymers. This enhances the adsorption bridging effect during coagulation, gradually improving the coagulation effect and increasing the pollutant removal rate. After reaching the optimal level at 3 hours, the OH- ions in the polymerization solution... - As the concentration of pollutants gradually decreases, the content of hydroxyl complexes produced also decreases, causing the polymerization reaction of the coagulant to proceed in the reverse direction. This leads to a decrease in the degree of polymerization of the coagulant and a reduction in the pollutant removal rate. In conclusion, the optimal pollutant removal time is 3 hours. At this time, the COD of the wastewater pollutant... Cr UV 254 The turbidity removal rates were 52%, 36.7%, and 93.68%, respectively.

Claims

1. A method for preparing a polyaluminum ferric titanium silicate coagulant, characterized in that, Includes the following steps: S1 coal gangue is roasted to obtain modified coal gangue; coal gangue that has passed through a 200-mesh sieve is roasted with anhydrous calcium carbonate and anhydrous sodium carbonate to obtain modified coal gangue. The mass ratio of anhydrous calcium carbonate and anhydrous sodium carbonate to coal gangue is 0.4~1.4:1, and the roasting temperature is 750~1000℃; the mass ratio of anhydrous calcium carbonate to anhydrous sodium carbonate is 1:

1. S2 modified coal gangue is acid leaching to obtain coal gangue acid leaching solution; S3 Coal gangue acid leaching solution is processed by titanium doping, pH adjustment, polymerization, centrifugation, and aging to obtain a coagulant; Titanium doping: titanium tetrachloride is added for doping, the pH value is adjusted to 0.5~3 with sodium hydroxide, and the polymerization reaction is carried out at 40~90℃ for 1~6h.

2. The preparation method of the polyaluminum ferric titanium silicate coagulant according to claim 1, characterized in that, Anhydrous calcium carbonate and anhydrous sodium carbonate, in a mass ratio of 1:1 to coal gangue, were roasted at 850℃.

3. The preparation method of the polyaluminum ferric titanium silicate coagulant according to claim 1, characterized in that, Acid leaching treatment: acid concentration of 2~7 mol / L, leaching time of 1.5~4 h, and leaching temperature of 60~90℃.

4. The preparation method of the polyaluminum ferric titanium silicate coagulant according to claim 3, characterized in that, Acid leaching treatment: acid concentration of 4 mol / L, acid leaching time of 3 h.

5. The method for preparing the aluminum-iron-titanium silicate coagulant according to claim 1, characterized in that, Adjust the pH to 1.5 and carry out the polymerization reaction at 70°C.

6. The preparation method of the polyaluminum ferric titanium silicate coagulant according to claim 1, characterized in that, Maturation: Maturate at 30~50℃ for 10~15 hours.

7. A polyaluminum ferric titanium silicate coagulant obtained by the preparation method according to any one of claims 1 to 6.

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