Titanium zirconium polysilicate-chitosan composite flocculant, preparation method and application thereof

Abstract

This invention discloses a polytitanium zirconium silicate-chitosan composite flocculant, its preparation method, and its application, relating to the field of environmental technology. The method includes the following steps: Step 1, preparation of chitosan acetic acid solution: Chitosan is dissolved in a dilute acetic acid solution to obtain a chitosan acetic acid solution; Step 2, preparation of the polytitanium zirconium silicate-chitosan composite flocculant: Under water bath conditions, the chitosan acetic acid solution is added to a polytitanium zirconium silicate salt solution, and the mixture is stirred and polymerized uniformly. The pH value of the solution is adjusted, and the polymerization is continued with stirring until it matures, thus obtaining the polytitanium zirconium silicate-chitosan composite flocculant. The composite flocculant of this invention achieves a turbidity and organic matter removal rate of over 90%, realizing the synergistic effect of inorganic and natural polymers. It has advantages such as low dosage, high removal efficiency, and environmental friendliness, providing a novel and efficient technical solution for drinking water pretreatment, urban sewage, and industrial wastewater treatment, and has significant theoretical value and engineering application prospects.

Description

Technical Field

[0001] This invention relates to the field of environmental technology, specifically to a polysilicate-zirconium-chitosan composite flocculant, its preparation method, and its application. Background Technology

[0002] With the acceleration of industrialization and urbanization, water pollution has become increasingly serious, and traditional water treatment processes are struggling to meet the demand for the synergistic removal of multiple complex pollutants. Coagulation-flocculation, as a fundamental unit process in water treatment, has long relied primarily on the single action of traditional inorganic coagulants (such as aluminum and iron salts) to remove colloids and suspended solids. However, these traditional flocculants often exhibit insufficient efficiency or increased byproduct risks when treating complex water qualities such as low turbidity water, water containing high concentrations of organic matter, nutrients, and emerging pollutants (such as nanoparticles).

[0003] Therefore, those skilled in the art are dedicated to addressing the problems existing in the above-mentioned background technology, aiming to construct a composite flocculant material that combines high-efficiency removal performance, good ecological safety, and engineering applicability, in order to solve the problems of insufficient removal efficiency, ecological risks, and narrow applicability of traditional flocculants when treating complex water quality. Summary of the Invention

[0004] The present invention provides a polysilicate titanium zirconium-chitosan composite flocculant, its preparation method and application, aiming to solve the problems existing in the above-mentioned background art.

[0005] To achieve the above-mentioned technical objectives, the present invention mainly adopts the following technical solutions:

[0006] In a first aspect, the present invention discloses a method for preparing a polyzirconium titanium silicate-chitosan composite flocculant, comprising the following steps:

[0007] Step 1, Preparation of chitosan acetate solution: Dissolve chitosan in dilute acetic acid solution to prepare chitosan acetate solution;

[0008] Step 2: Preparation of polytitanium zirconium silicate-chitosan composite flocculant: Under water bath conditions, the chitosan acetic acid solution is added to the polytitanium zirconium silicate salt solution, stirred and polymerized evenly, the pH value of the solution is adjusted, and stirring and polymerization are continued until the solution is matured to obtain the polytitanium zirconium silicate-chitosan composite flocculant.

[0009] In a preferred embodiment of the present invention, in step 1, the concentration of the dilute acetic acid is 0.1 mol / L, and the chitosan acetic acid solution contains 1 wt.% chitosan by weight.

[0010] In a preferred embodiment of the present invention, in step 2, the mass ratio of chitosan to polyzirconium titanium silicate is chitosan: polyzirconium titanium silicate = 0.2-0.4, the polyzirconium titanium silicate salt is polyzirconium titanium silicate chloride, the pH is adjusted to 1.5-3.5 with sodium hydroxide solution, the polymerization is continued for 1 hour with stirring, and the curing is carried out for 24 hours. The polymerization temperature of chitosan and polyzirconium titanium silicate is 20-50℃.

[0011] Preferably, in step 2, the pH of the solution is adjusted to 2.5–3.5.

[0012] In a second aspect, the present invention discloses a polysilicate zirconium-chitosan composite flocculant prepared by the method described in the first aspect.

[0013] Thirdly, this invention discloses the application of the polyzirconium silicate-chitosan composite flocculant as described in the second aspect in drinking water pretreatment, urban sewage and industrial wastewater treatment.

[0014] In a preferred embodiment of the present invention, the flocculation conditions of the composite flocculant in water treatment are determined using response surface methodology, including the following steps:

[0015] Step 71: Add the composite flocculant to the water treatment system;

[0016] Step 72: Using the response surface methodology, with pH, ​​the amount of composite coagulant added, and the rapid stirring time as independent variables, and turbidity removal rate and organic matter removal rate as response variables, a second-order polynomial regression model is established to predict the optimal flocculation conditions.

[0017] Step 73: Determine the optimized combination of flocculation parameters based on the model;

[0018] Step 74: Perform water treatment operations according to the optimized combination of flocculation parameters.

[0019] In a preferred embodiment of the present invention, in step 72, the regression equation for the turbidity removal rate is:

[0020] Turbidity removal rate = -84.1 + 34.08 pH + 31.74 Dosage + 7.94 Rapid stirring time - 2.258 pH² - 6.457 Dosage² - 1.109 Rapid stirring time²;

[0021] The regression equation for the organic matter removal rate is: Organic matter removal rate = -98.3 + 35.75 pH + 34.80 dosage + 8.98 rapid stirring time - 2.389 pH² - 6.913 dosage² - 1.306 rapid stirring time²;

[0022] The unit for rapid stirring time is min, and the unit for dosage is ml / L.

[0023] In a preferred embodiment of the present invention, the optimal flocculation conditions determined in step 73 are: pH=7.10, dosage=2.65mL / L, and rapid stirring time=4.83min.

[0024] In a preferred embodiment of the present invention, in step 74, water treatment operation is performed according to the optimized combination of flocculation parameters, with a predicted turbidity removal rate of 98.86% and a predicted organic matter removal rate of 96.77%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention effectively combines titanium zirconium polysilicate with chitosan, achieving a combined effect of multiple mechanisms such as charge neutralization, adsorption-bridging, and structural enhancement through the synergistic effect of the two, thereby improving the flocculant's ability to reduce turbidity, COD, and UV in wastewater. 254 In addition to improving the removal efficiency of indicators such as pH, it can also broaden the applicable pH range and water quality types, reduce the dosage of traditional inorganic flocculants, and improve the overall stability and safety of the water treatment process.

[0027] This invention, through response surface methodology optimization experiments, determined the optimal flocculation conditions for water treatment using a composite flocculant. At pH 7.1, PSTZ-CTS exhibited the best charge neutralization effect, with a zeta potential close to zero, promoting particle aggregation and sedimentation in the water. At a dosage of 2.65 mL / L and a rapid stirring time of 4.8 min, the composite flocculant demonstrated the highest removal efficiency. With increasing dosage, the zeta potential of the composite flocculant gradually approached zero, achieving optimal charge neutralization, weakening the electrostatic repulsion between particles, and promoting floc formation and sedimentation. Attached Figure Description

[0028] Figure 1 Figure 1 shows the effect of chitosan CTS and polytitanium zirconium silicate PSTZ on the coagulation effect at different ratios.

[0029] Figure 2 This is a graph showing the effect of polymerization pH on coagulation efficiency.

[0030] Figure 3 This is a graph showing the effect of polymerization temperature on coagulation.

[0031] Figure 4 FTIR spectrum of PSTZ-CTS composite flocculant;

[0032] Figure 5 X-ray diffraction pattern of PSTZ-CTS composite flocculant;

[0033] Figure 6 Scanning electron microscopy analysis of PSTZ-CTS composite flocculant;

[0034] Figure 7 The graph shows the effect of composite flocculant dosage on coagulation effect.

[0035] Figure 8 The graph shows the effect of water sample pH on the coagulation effect of composite flocculant.

[0036] Figure 9 The graph shows the effect of rapid stirring time on the coagulation effect of composite flocculants.

[0037] Figure 10 The graph shows the effect of settling time on the coagulation performance of the composite flocculant.

[0038] Figure 11 The response surface and contour plot of pH and dosage to turbidity removal rate;

[0039] Figure 12 The response surface and contour plot of dosage and rapid stirring time to turbidity removal rate;

[0040] Figure 13 The response surface and contour plot of pH and rapid stirring time to turbidity removal rate;

[0041] Figure 14 The response surface and contour plot of pH and dosage to organic matter removal rate;

[0042] Figure 15 The response surface and contour plot of organic matter removal rate to dosage and rapid stirring time;

[0043] Figure 16 The response surface and contour plot of pH and rapid stirring time to organic matter removal rate;

[0044] Figure 17 Zeta potential analysis of water samples containing PSTZ-CTS composite coagulant under different pH conditions;

[0045] Figure 18 This is a comparison chart of the treatment effects of PSTZ and PSTZ-CTS on low turbidity water. Detailed Implementation

[0046] The present invention will be further described below in conjunction with the accompanying drawings and embodiments / test examples. However, it should be understood that these detailed descriptions and embodiments / test examples are merely for more detailed and specific illustration and should not be construed as limiting the present invention in any way.

[0047] This invention provides a general and / or specific description of the materials and methods used in the experiments. While many of the materials and methods of operation used to achieve the objectives of this invention are well known in the art, they are still described in as much detail as possible herein. It will be apparent to those skilled in the art that, unless otherwise stated, the materials and methods used in this invention are well known in the art.

[0048] This invention focuses on the synergistic formulation design and performance enhancement of a polytitanium zirconium silicate-chitosan composite coagulant (PSTZ-CTS). Using an optimized PSTZ formulation as the inorganic base and natural high-molecular-weight chitosan (CTS) as the organic coagulant aid, a composite system was constructed by adjusting parameters such as the PSTZ:CTS mass ratio, polymerization pH, and polymerization temperature. The JAR test was used to evaluate the synergistic effects of the composite flocculant dosage, sedimentation time, rapid stirring time, and simulated water sample pH on the flocculation treatment effect. The results show that the effective composite of PSTZ and chitosan achieves a combined effect through multiple mechanisms, including charge neutralization, adsorption-bridging, and structural enhancement, which is expected to improve the performance of flocculation treatment for turbidity, COD, and UV radiation. 254 In addition to improving the removal efficiency of indicators such as pH, it can also broaden the applicable pH range and water quality types, reduce the dosage of traditional inorganic flocculants, and improve the overall stability and safety of the water treatment process.

[0049] The following is a description through specific embodiments.

[0050] Example 1: Preparation of PSTZ-CTS Composite Coagulant

[0051] Preparation of chitosan acetic acid solution (CTS): First, prepare an acidic solvent in a clean container by mixing deionized water with an appropriate amount of acetic acid to make a 0.1 mol / L dilute acetic acid solution. Accurately weigh chitosan powder and slowly add it to the acetic acid solution in batches, while continuously stirring with a magnetic stirrer at room temperature to prevent the chitosan powder from clumping. The dissolution of chitosan in the acetic acid aqueous solution is based on the protonation of its amino groups by acetic acid, thereby forming a homogeneous swollen solution under acidic conditions. Continue stirring until the chitosan is completely dissolved and the solution is homogeneous with no obvious solid particles, to obtain the desired 1 wt.% chitosan acetic acid solution.

[0052] Preparation of polyzirconium titanium silicate chloride-chitosan composite flocculant: Under a water bath at 35℃, a predetermined amount of polyzirconium titanium silicate chloride flocculant was added to a beaker, and then placed on a magnetic stirrer for stirring. Then, according to a CTS:PSTZ mass ratio of 3, chitosan acetate solution was added to the beaker. After uniform stirring, a certain amount of sodium hydroxide solution was added to adjust the pH to 3. Stirring was continued for 1 hour, followed by maturation for 24 hours to obtain the polyzirconium titanium silicate chloride-chitosan composite flocculant.

[0053] The composite flocculant prepared in Example 1 was structurally characterized, and the results are as follows: Figures 4-6 As shown. Among them, The FT-IR transmittance spectra of CTS, PSTZ, and PSTZ-CTS composites are presented. All samples exhibit a broad peak at approximately 3440 cm⁻¹, corresponding to the stretching vibrations of hydroxyl (–OH) and amino (–NH) groups, respectively. This indicates that both CTS and PSTZ samples possess abundant hydrophilic functional groups on their surfaces. The lower transmittance of this peak in PSTZ suggests a higher hydroxyl / amino group density, while the variation at this peak in the PSTZ-CTS composite suggests hydrogen bonding or coordination between CTS molecules and the PSTZ surface. PSTZ samples exhibit distinct characteristic peaks, such as the organic or heterocyclic vibration at 1634.9 cm⁻¹, the Si-O / Ti-O related vibration at 1073.7 cm⁻¹, the characteristic skeletal vibration at 793.1 cm⁻¹, and the low-frequency skeletal peak at 457.2 cm⁻¹. These peaks are still identifiable in the composite material, but the peak shape and transmittance have changed, especially showing a slight increase in peak intensity near 1073.7 cm⁻¹, which indicates that the introduction of CTS molecular chains has affected the vibration of the inorganic skeleton.

[0054] Compared to the CTS sample, the PSTZ-CTS complex retains the typical functional group absorption characteristics of CTS (such as C=O and N–H vibrations near 1650 and 1550 cm⁻¹) and also exhibits skeletal vibration peaks similar to those of PSTZ. This superposition of peak positions and intensity variation reflects the existence of a significant interfacial interaction mechanism within the complex, making the characteristic binding of the two components more compact.

[0055] In summary, the FT-IR spectra show that the composite of CTS and PSTZ not only retains their respective functional groups and skeletal vibrational characteristics, but also induces intensity changes and slight shifts in certain peak positions. This is consistent with the tight structural bonding and functional modification mechanism of composite materials, providing spectroscopic evidence for improving material properties.

[0056] While the original PSTZ crystalline phase diffraction peaks were still identifiable, the overall peak intensity was significantly reduced, and some peaks showed slight broadening. This decrease in peak intensity and change in peak shape is mainly attributed to the introduction of chitosan, which coats the PSTZ crystal interface and introduces crystal defects, thus reducing the orderliness of the crystal planes. Furthermore, in the lower diffraction angle range, the composite sample exhibited a smoother background signal, consistent with the amorphous characteristics of chitosan as an amorphous polymer component. These XRD characteristics indicate that interfacial interactions occurred between CTS and PSTZ during the composite process, resulting in a composite material that retains the main crystalline phase structure of PSTZ while exhibiting characteristics of crystalline phase intensity attenuation and enhanced amorphous background. This is consistent with the interfacial mixing effect and changes in crystallinity of the composite material.

[0057] like Figure 6 As shown in the image, scanning electron microscopy morphological comparison reveals that single polytitanium zirconium silicate (PSTZ) exhibits relatively regular blocky particle characteristics, with a relatively smooth particle surface and a lack of polymeric interfacial structures. However, in the composite system with added chitosan (CTS), numerous smaller deposits appear on the particle surface, the polymeric network structure significantly increases, and obvious bridging and bonding phenomena are observed between particles. This change in microstructure indicates that CTS, as a polymeric auxiliary agent, achieves effective interfacial coupling with PSTZ, resulting in better particle dispersion and a more complex structure in the composite system.

[0058] These morphological differences directly reflect the stronger structure-building ability of the composite system during flocculation. Compared to single PSTZ, the PSTZ-CTS composite system, due to the participation of polymer chains, forms more adsorption bridging and cross-linked network structures at the microscale. This provides richer binding sites for the capture, aggregation, and sedimentation of pollutant particles, thus significantly improving the stability and removal efficiency of the flocs. This result reveals the mechanism by which CTS enhances the performance of the PSTZ coagulation system at the microscopic level, providing clear morphological support for further development of highly efficient composite coagulants.

[0059] Experiment 1: Investigating the effect of the CTS to PSTZ ratio on coagulation performance.

[0060] Experimental water sample: The experimental water sample was prepared according to the method of simulating typical surface water quality. 50 mg of kaolin and 10 mg of humic acid were weighed and added to 1 L of deionized water. The mixture was stirred evenly with a magnetic stirrer to fully disperse the kaolin and mix it with the humic acid to obtain a representative experimental water sample.

[0061] Experimental Methods: Coagulation experiments were conducted using a six-unit stirrer. After adding 1L of experimental water sample to each beaker, a pre-set amount of composite coagulant was added. The stirrer was immediately started for rapid stirring at 400 rpm for 3 minutes to ensure rapid dispersion of the coagulant and full contact with suspended solids in the water sample, simulating the rapid mixing stage of the coagulation process. Then, the stirring speed was switched to slow stirring at 120 rpm for 20 minutes to simulate the flocculation stage conditions, promoting the growth and aggregation of microflocculations. After stirring, the samples were allowed to settle for 30 minutes to allow the generated flocs to settle. Once settling was complete, a sample of the clear liquid approximately 2 cm below the water surface was taken as the test sample and used for residual turbidity measurement and UV spectrophotometer determination. 254 Absorbance value is used to evaluate the suspended solids removal performance and organic pollutant removal effect of coagulants.

[0062] Water quality testing methods:

[0063] (1) Measurement of turbidity

[0064] Turbidity was determined using a turbidimeter method, with Nephelometric Turbidity Units (NTU) representing the degree of light scattering caused by suspended particles in the water sample. This method complies with the national industry standard "Determination of Turbidity in Water - Turbidimeter Method (HJ1075-2019)" and is operated in accordance with ISO 7027-1:2016 quantitative determination method. During measurement, the water sample to be tested was placed in a clean sample cup, and calibration was performed according to the instrument's instruction manual before testing. The turbidity value of the water sample was recorded to evaluate the change in turbidity of the water before and after coagulation treatment.

[0065] (2) Determination of humic acid

[0066] The evaluation of organic matter content in water samples was performed using UV. 254 Absorbance was used as an indicator, and the ultraviolet absorbance (UV) of the water sample at a wavelength of 254 nm was measured using a UV-Vis spectrophotometer. 254 This method is based on the absorption characteristics of organic matter in water to 254 nm ultraviolet light, and can serve as a rapid indicator of changes in total organic matter. During measurement, the water sample is placed in a clean quartz cuvette. Using deionized water as a reference, the instrument is baseline-calibrated, and the absorbance of the water sample is directly measured at 254 nm. The corresponding UV values ​​are recorded. 254 Absorbance values ​​are used to evaluate the removal efficiency of coagulants on organic matter in water.

[0067] The results showed that the coagulant had different CTS:PSTZ mass ratios on turbidity and UV radiation. 254The turbidity removal performance varies with dosage. In the turbidity removal rate curves, when CTS:PSTZ = 0.2 and 0.4, the system achieves extremely high removal efficiency within a dosage range of 2–3 mL, and the turbidity removal rate tends to stabilize with further increases in dosage, demonstrating highly efficient removal capabilities. In contrast, when CTS:PSTZ = 0.6, 0.8, and 1.0, the turbidity removal rate of the system shows a gradual upward trend with increasing dosage, but its peak value is significantly lower than that of the low-ratio system; at a dosage of 5 mL, the higher CTS content actually causes a slight decrease in turbidity removal rate. This is because the hydrolyzed metal complex of PSTZ can provide multiple positive charge centers, which is beneficial for the electrical neutralization and adsorption of negatively charged colloids and organic matter, while an appropriate amount of CTS can promote the formation of large-sized flocs through long-chain polymer bridging, improving settling properties. When the proportion of CTS in the composite system is too high, its own polymer chains may limit the optimal binding with colloidal particles in the water, thus affecting the density and settling performance of the flocs. Regarding the removal rate of organic matter, the overall trend of each formulation system was similar to that of turbidity removal, but the values ​​were significantly lower, indicating that the removal of organic matter was more difficult than the instability and aggregation of suspended particles. For low-ratio systems (CTS:PSTZ=0.2, 0.4), UV... 254 The removal rate reached near its maximum value around a dosage of 3 mL and then stabilized or slightly decreased. This reflects that PSTZ, as an inorganic polymer, possesses excellent adsorption and charge neutralization capabilities for organic pollutants. Under appropriate compounding ratios, it can promote the removal of dissolved organic matter by enhancing charge neutralization and bridging adsorption effects. When the CTS ratio increased to 0.6–1.0, the UV254 removal rate showed little change with increasing dosage and remained relatively low overall. This may be because when the ratio is too high, the CTS polymer chains themselves may form a large polymer network in water, occupying some active sites in the composite system. This results in poor floc density and a reduction in effective contact sites, thereby reducing the overall UV254 removal efficiency.

[0068] Experimental Example 2: Investigating the effect of polymerization pH on coagulation effect

[0069] The experimental water sample and experimental method are the same as in Experiment 1.

[0070] The study clearly demonstrates the significant impact of the polymerization pH of the composite coagulant PSTZ-CTS on its flocculation performance. The turbidity removal rate fluctuated significantly with changes in polymerization pH. Under polymerization pH conditions of 1.5–2.0, PSTZ-CTS exhibited high turbidity removal efficiency, which increased rapidly with increasing dosage. As the polymerization pH increased to approximately 2.5–3.0, the turbidity removal rate reached or approached its maximum value at all dosage levels and maintained high stability under high dosage conditions. This indicates that this polymerization pH range facilitates the formation of effective positively charged metal hydroxyl complexes and bridging networks within the composite coagulant, contributing to charge neutralization of colloidal particles and the formation of large-sized flocs. Further increasing the polymerization pH to 3.5–4.0 resulted in a decreasing trend in turbidity removal rate. Especially at pH 4.0, regardless of dosage, the turbidity removal efficiency was significantly lower than in the intermediate pH range, indicating that excessively high polymerization pH conditions may lead to a decrease in the composite efficiency of chitosan and PSTZ, thereby weakening the overall flocculation performance of the composite agent. Regarding organic matter removal, the polymerization pH also significantly affects the composite agent. At lower pH conditions, the organic matter removal rate shows a marked increase with increasing dosage, but the overall level is not as high as under intermediate pH conditions. When the polymerization pH reaches 3.0, the organic matter removal rate peaks in the 2–3 mL range with increasing dosage and remains at a high level even at 4–5 mL. This phenomenon indicates that this polymerization pH is conducive to constructing a composite structure that possesses both strong charge neutralization ability and enhanced adsorption bridging, thereby more effectively capturing and settling suspended solids and organic matter. In contrast, the inorganic organic matter removal efficiency decreases significantly at pH=4.0, suggesting that excessively high polymerization pH may affect the active distribution of functional groups in the composite network, weakening the affinity of the composite agent for soluble organic matter.

[0071] Overall, the polymerization pH of PSTZ-CTS between 2.5 and 3.5 significantly improves flocculation performance. The composite structure synthesized within this range enhances the formation of positively charged metal hydroxyl complexes and optimizes the physicochemical bonding between chitosan and the inorganic components. This facilitates the synergistic effect of charge neutralization and adsorption-bridging, thereby enhancing the removal of turbidity and organic matter. Excessively high or low polymerization pH conditions are detrimental to the formation of effective flocculation structures, leading to performance degradation of the composite agent.

[0072] Experimental Example 3: Investigating the effect of polymerization temperature on coagulation effect

[0073] The experimental water sample and experimental method are the same as in Experiment 1.

[0074] This reflects the effect of the polymerization temperature of the composite coagulant on its performance in removing turbidity and organic matter. (a) It was found that under various temperature conditions, the turbidity removal rate generally increased first and then decreased with increasing dosage, but the peak value and trend of removal efficiency differed significantly at different temperatures. At polymerization temperatures of 20℃ and 30℃, the turbidity removal rate increased rapidly at dosages of approximately 2–3 mL. With further increases in dosage, the removal rate slightly decreased but remained at a high level. At temperatures of 40℃ and 50℃, the turbidity removal rate generally remained high across the entire dosage range, with peak values ​​slightly higher than at lower temperatures. This indicates that moderately increasing the polymerization temperature helps in the formation of PSTZ-CTS active sites and the construction of bridging structures, resulting in more effective flocculation of suspended particles by the composite system. In contrast, the turbidity removal rate was generally low at 60℃, especially in the medium and high dosage ranges, where the peak value was lower than at other temperatures. This suggests that excessively high polymerization temperatures may lead to thermal degradation of the chitosan chain structure or a decrease in the stability of the composite network, thereby weakening the overall coagulation performance of the composite agent. The response of organic matter removal efficiency to polymerization temperature was generally consistent with the trend of turbidity removal, but it better reflected the effect of temperature on the adsorption-bridging interaction of organic matter. At 20℃, the organic matter removal rate increased with increasing dosage, reaching a peak around 3 mL and then decreasing. When the temperature increased to 30℃ and 40℃, the organic matter removal rate was significantly higher than that at 20℃ under most dosage conditions, with the peak value at 40℃ even exceeding 85%, highlighting the promoting effect of moderate temperature on the interaction between the composite structure and organic matter. As the polymerization temperature further increased to 50℃, the organic matter removal rate was relatively stable overall, but decreased compared to the peak value at 30–40℃. At 60℃, the organic matter removal efficiency was relatively low across all dosage ranges, consistent with the trend of turbidity removal, reflecting that high temperature may weaken the synergistic effect between CTS and PSTZ and the adsorption capacity of the composite structure for dissolved organic matter.

[0075] Experiment 4: Investigating the effect of dosage on coagulation effect

[0076] The experimental water sample and experimental method are the same as in Experiment 1.

[0077] The turbidity removal rate and UV index of PSTZ-CTS composite coagulant under different dosage conditions were demonstrated. 254Removal rates. As the dosage increased from 1.5 mL to 3.5 mL, both turbidity and organic matter removal rates showed a trend of initial increase followed by stabilization. Specifically, at a dosage of 2.5 mL, the turbidity removal rate reached 99.18%, and the organic matter removal rate was 94.76%, both demonstrating optimal removal effects. With increases in dosage to 3 mL and 3.5 mL, the removal efficiency decreased slightly but remained at a high level. The data shows that at lower dosages, such as 1.5 mL, the turbidity removal rate was 73.19%, and the organic matter removal rate was 74.62%, significantly lower than the effects at higher dosages. This indicates that lower dosages failed to provide sufficient active sites for effective charge neutralization and adsorption. With increasing dosage, the removal efficiency of turbidity and organic matter gradually improved, reaching its peak at a dosage of 2.5 mL. When the dosage was further increased to 3 mL and 3.5 mL, the removal rate decreased slightly. In particular, the removal effect at 3.5 mL was slightly lower in turbidity removal rate, indicating that excessive dosage may lead to excessively dense flocs, thereby affecting sedimentation performance and effective removal.

[0078] Experiment 4: Investigating the effect of water sample pH on coagulation effect

[0079] The experimental water sample and experimental method are the same as in Experiment 1.

[0080] The turbidity removal rate and organic matter removal rate of the PSTZ-CTS composite coagulant were compared under different pH conditions for different water samples. The turbidity removal rate showed high efficiency under neutral to slightly alkaline conditions (pH=6–8), with turbidity removal rates reaching 95.92% and 99.25% at pH=6 and pH=7, respectively, and organic matter removal rates reaching 93.61% and 95.83%, respectively. When the pH value was further increased to 8, the composite system still maintained high turbidity removal efficiency (92.74%) and organic matter removal efficiency (89.97%), indicating that the composite coagulant has good adaptability and stability over a wide pH range. In contrast, the turbidity removal rate of the single PSTZ system at pH=8 was only about 21.56%, and the organic matter removal rate was about 64.58%, showing that when the single system encountered alkaline water samples, its ability to coagulate suspended particles and capture organic pollutants decreased significantly.

[0081] The superiority of the composite system over the single system stems primarily from the synergistic effect between PSTZ and CTS. Under neutral to weakly alkaline conditions, the metal hydrolyzed complexes of PSTZ can electrically neutralize colloids and organic matter in water. Simultaneously, the amino and hydroxyl groups in the chitosan segments can effectively capture fine particles and dissolved organic matter through adsorption-bridging interactions, forming larger flocs with better settling properties. In the composite system, the polymer chains of CTS not only provide additional adsorption sites but also expand the flocculation network structure, allowing the composite flocculant to maintain high removal efficiency even at higher pH conditions. In contrast, under alkaline conditions (e.g., pH=8), the binding capacity of single PSTZ to colloidal particles and organic matter is significantly weakened, resulting in a substantial decrease in turbidity removal efficiency. This synergistic effect indicates that in practical water treatment applications, single inorganic polymer flocculants may be limited under specific pH conditions, while the introduction of natural high-molecular-weight chitosan can significantly enhance the adaptability and purification performance of the coagulant. This result verifies the superior performance of PSTZ-CTS over a wide pH range.

[0082] Experimental Example 5: Investigating the effect of rapid stirring time on coagulation effect

[0083] The experimental water sample and experimental method are the same as in Experiment 1.

[0084] This indicates that the rapid stirring time has a significant impact on the removal performance of the PSTZ-CTS composite coagulant. With a rapid stirring time of 1-2 min, the removal rates of turbidity and organic matter steadily increased with increasing stirring time, with the turbidity removal rate increasing from approximately 78.45% to 91.84% and the organic matter removal rate increasing from 75.92% to 88.29%. As the rapid stirring time further increased to 3 min and 4 min, the removal effect continued to improve, but the rate of improvement gradually decreased. Particularly at 5 min, the composite coagulant exhibited optimal performance, with a turbidity removal rate of 99.95%, an organic matter removal rate of 96.83%, and residual turbidity reduced to an extremely low level (approximately 0.03 NTU). These results demonstrate that a rapid stirring time of 5 min provides sufficient kinetic conditions for the formation of stable, uniform, and highly efficient flocs in this composite system. When the rapid stirring time was further extended to 6 minutes, the removal efficiency showed a slight downward trend, with a turbidity removal rate of 95.38% and an organic matter removal rate of 92.47%. This may be because the prolonged high-speed stirring caused a shearing and damaging effect on the already formed flocs, causing some flocs to disintegrate or become loose, thus reducing the flocculation-sedimentation efficiency. This phenomenon indicates that in the flocculation process of a composite system, the rapid stirring stage needs sufficient time to promote adequate contact and reaction between the coagulant and the suspended solids, but it should not be prolonged excessively to prevent damage to the already formed flocs.

[0085] Experiment 6: Investigating the effect of settling time on coagulation effect

[0086] The experimental water sample and experimental method are the same as in Experiment 1.

[0087] This study demonstrates the performance of PSTZ-CTS composite coagulant in removing turbidity and organic matter under different settling times. At shorter settling times, the improvement in turbidity and organic matter removal rates is significant, especially at 10 minutes, where the turbidity removal rate is 95.64% and the organic matter removal rate is 88.05%. With increasing settling time, the removal rate gradually increases, reaching 98.94% for turbidity and 94.28% for organic matter at 20 minutes, exhibiting the best removal effect. However, when the settling time exceeds 20 minutes, the removal effect tends to plateau. At 30 minutes, the turbidity removal rate slightly decreases to 95.83%, and the organic matter removal rate is 90.42%, while the residual turbidity increases to 2.64 NTU. This phenomenon indicates that with prolonged settling time, the composite flocs may fail to effectively remove some pollutants due to excessive sedimentation or deagglomeration.

[0088] Example 2: Optimization of Flocculation Conditions in Water Treatment Process Using Composite Flocculants Based on Response Surface Methodology

[0089] 1. Response surface experimental design

[0090] This embodiment systematically investigates the interactive effects of pH, dosage of polytitanium zirconium silicate-chitosan (PSTZ-CTS) composite coagulant, and rapid stirring time on flocculation performance and their optimal conditions. The present invention uses the response surface methodology, with turbidity removal rate and organic matter removal rate as response indicators, to conduct multi-factor optimization experiments.

[0091] The experiment used a Box-Behnken design; the response surface design factors and levels are detailed below. The experimental design and results are shown in [link to experimental design]. .

[0092] surface Response Surface Design Factors and Levels Table

[0093]

[0094] surface Response surface methodology experimental design and results

[0095]

[0096] 2. Regression Model Fitting and Analysis of Variance

[0097] Multiple regression analysis was performed on the Box-Behnken response surface experimental data using Minitab 22 software to fit a complete quadratic model, and significant terms were screened using a stepwise method. Response surface models were established with pH, ​​PSTZ-CTS composite coagulant dosage, and rapid stirring time as independent variables, and turbidity removal rate and organic matter removal rate as response variables, respectively.

[0098] (1) Regression model and statistical test of turbidity removal rate

[0099] The fitting results of the quadratic regression model for turbidity removal rate are shown below. The model summary shows that S=1.4690, R²=98.34%, R²(adjusted)=95.36%, and R²(predicted)=73.77%, indicating that the model has a high degree of fit to the experimental data and good explanatory power, but its predictive power is slightly lower than the adjusted R², which may be due to the limitation of the number of experimental points.

[0100] surface Summary of turbidity removal rate models

[0101]

[0102] Analysis of variance The results showed that the overall model was highly significant (P < 0.001); the lack-of-fit term (P = 0.103 > 0.05) showed no significant lack of fit, indicating a suitable model. The linear terms (pH, dosage, rapid stirring time), quadratic terms (pH², dosage², rapid stirring time²), and interaction terms (pH × dosage, dosage × rapid stirring time, rapid stirring time²) were all significant (P < 0.01 or P < 0.05), with pH and pH² showing the largest F-values, indicating that pH was the dominant factor.

[0103] surface Analysis of variance table for turbidity removal rate

[0104]

[0105] The diagnosis of outlier observations showed that the standardized residuals of observations 1 and 11 were -2.08 and 2.08, respectively. The residuals were relatively large but did not exceed three times the standard deviation, so their impact on the model was limited.

[0106] The regression equation for turbidity removal rate expressed in uncoded units is:

[0107] Turbidity removal rate = -84.1 + 34.08 pH + 31.74 Dosage + 7.94 Rapid stirring time - 2.258 pH² - 6.457 Dosage² - 1.109 Rapid stirring time²;

[0108] (2) Regression model and statistical test of organic matter removal rate

[0109] The fitting results of the quadratic regression model for organic matter removal rate are shown in Table 4-4. The model summary shows that S=1.6144, R²=98.22%, R²(adjusted)=95.02%, and R²(predicted)=72.25%, indicating a high degree of fit, but the predictive ability is slightly lower than that of the adjusted R².

[0110] surface Summary of Organic Matter Removal Rate Models

[0111]

[0112] Analysis of variance The results showed that the overall model was highly significant (P < 0.001); the lack-of-fit term (P = 0.042 < 0.05) indicated slight lack of fit, but the overall model remained applicable. The linear terms (dosage amount, rapid stirring time), quadratic terms (pH², dosage²), and interaction terms (pH × dosage, dosage × rapid stirring time, rapid stirring time × rapid stirring time) were significant (P < 0.01 or P < 0.05), with pH² and dosage × dosage terms having a prominent effect, indicating that pH and dosage have a strong nonlinear regulatory effect on humic acid removal.

[0113] surface Analysis of variance table of organic matter removal rate

[0114]

[0115] The abnormal observation diagnosis showed that the standardized residuals of observations 1 and 11 were -2.01 and 2.01, respectively. The residuals were large but did not exceed the critical range.

[0116] The regression equation for organic matter removal rate expressed in uncoded units is:

[0117] Organic matter removal rate = -98.3 + 35.75 pH + 34.80 dosage + 8.98 rapid stirring time - 2.389 pH² - 6.913 dosage² - 1.306 rapid stirring time²;

[0118] Both response models showed high goodness of fit (adjusted R² > 95%), but the predicted R² was relatively low, possibly due to limitations in the number of experimental points. pH and dosage were the main influencing factors, with significant quadratic and interaction terms, reflecting the synergistic flocculation mechanism of PSTZ-CTS composite coagulant under acid-base and dosage control. Rapid stirring time had a weak effect, but moderate stirring was beneficial for floc formation.

[0119] 3. Response surface and contour line analysis

[0120] Based on the established quadratic regression model for turbidity removal rate, Minitab22 software was used to plot response surface plots and contour plots of the interactions between various factors, further revealing the combined effects of pH, dosage, and rapid stirring time on turbidity removal rate. The third factor was fixed at the median level, and the results are as follows: - As shown.

[0121] (1) Response surface and contour analysis of turbidity removal rate

[0122] (a) and (b) are the response surface plot and contour plot of turbidity removal rate under the interaction of pH and dosage, respectively. The response surface exhibits a distinct parabolic shape with a single peak region. The removal rate reaches its highest level (>96%) near pH 6.0–7.5 and dosage 2.4–3.0 mL / L, indicating that the charge neutralization and adsorption bridging effects of the PSTZ-CTS composite coagulant are optimal in this range. The contour plot shows that the optimal operating window is elliptical, centered at pH=7.0 and dosage=2.7 mL / L. The removal rate gradient decreases rapidly towards both sides of pH and at both ends of dosage, indicating that the influence of pH on the removal rate is greater than that of dosage.

[0123] (a) and (b) are the response surface plot and contour plot, respectively, under the interaction of dosage and rapid stirring time. The surface slope is relatively gentle, with the peak value located in the region of dosage 2.5–3.0 mL / L and rapid stirring time 3.5–5.0 min, and the removal rate is >93%. Too short a rapid stirring time (<3 min) leads to insufficient mixing, while too long a time (>5 min) may damage the floc structure, both of which reduce the removal rate, indicating that moderate rapid stirring is beneficial to the rapid growth and sedimentation of flocs.

[0124] (a) and (b) are the response surface plot and contour plot, respectively, of the interaction between pH and rapid stirring time (dosage fixed at 2.5 mL / L). The surface also exhibits a parabolic shape, with peak values ​​at pH 6.5–7.5 and rapid stirring time 3.5–5.0 min, where the removal rate is >92%. The removal rate drops sharply after the pH deviates from neutral, and the effect of rapid stirring time is relatively small, but the optimal range is concentrated in 3.5–5.0 min, reflecting the promoting effect of moderate stirring time on particle destabilization and flocculation.

[0125] Combining the three sets of response surfaces and contour plots, the turbidity removal rate exhibits significant nonlinear characteristics and interactive effects. pH is the dominant factor, with its quadratic term having the greatest impact; dosage is the second most important factor, with an optimal point for appropriate dosage; the effect of rapid stirring time is relatively weak. The optimal region is concentrated at pH=7.0, dosage=2.7mL / L, and rapid stirring time=4.0min. The contour plot shows that the optimal window is elliptical, and the gradient of pH's influence on the removal rate is the steepest, indicating that the PSTZ-CTS composite coagulant has the best flocculation efficiency at near-neutral pH.

[0126] (2) Response surface and contour analysis of organic matter removal rate

[0127] (a) and (b) are the response surface plot and contour plot of organic matter removal rate under the interaction of pH and dosage, respectively. The response surface exhibits a distinct parabolic shape, with the peak region located at pH 6.0–7.5 and dosage 2.4–3.0 mL / L, where the removal rate is >95%. The contour plot shows that the optimal window is nearly circular, centered at pH=6.8 and dosage=2.7 mL / L. The removal rate gradient decreases rapidly towards both sides of pH and at both ends of dosage, indicating that the PSTZ-CTS composite coagulant is optimal for organic matter removal at near-neutral pH, and the adsorption and bridging effects are significantly weakened after the pH deviates from neutral.

[0128] (a) and (b) are the response surface plot and contour plot, respectively, under the interaction of dosage and rapid stirring time. The surface slope is relatively gentle, with the peak value located in the region of dosage 2.5–3.0 mL / L and rapid stirring time 4.0–5.0 min, and the removal rate >92%. Too short a rapid stirring time (<3.5 min) leads to insufficient mixing, while too long a time (>5.5 min) may destroy the organic matter-coagulant composite flocs, both of which reduce the removal rate, reflecting the promoting effect of appropriate stirring time on the adsorption and flocculation of organic matter.

[0129] (a) and (b) are the response surface plot and contour plot, respectively, under the interaction of pH and rapid stirring time. The surface also exhibits a parabolic shape, with the peak value located at pH 6.5–7.5 and rapid stirring time 3.5–5.0 min, where the removal rate is >90%. The removal rate drops sharply after the pH deviates from neutral, and the effect of rapid stirring time is relatively small, but the optimal range is concentrated in 3.5–5.0 min, indicating that moderate rapid stirring is beneficial to the sufficient contact and bridging sedimentation of PSTZ-CTS and humic acid.

[0130] Combining the three sets of response surfaces and contour plots, the organic matter removal rate exhibited significant nonlinear characteristics and interactive effects. pH was the dominant factor, with its quadratic term having the greatest impact; dosage was the second most significant factor, with an optimal point for appropriate dosage; the effect of rapid stirring time was relatively weak. The optimal region was concentrated at pH = 6.8–7.0, dosage = 2.7 mL / L, and rapid stirring time = 4.0–4.5 min. The contour plots showed that the optimal window was narrower than that for turbidity removal, reflecting that humic acid removal was more sensitive to pH and dosage.

[0131] 4. Multi-response optimization and determination of optimal conditions

[0132] To comprehensively consider the synergistic optimization effect of turbidity removal rate and organic matter removal rate, the Minitab22 response optimizer was used to perform multi-response optimization on the established quadratic regression model. With the maximization of turbidity removal rate and organic matter removal rate as the objective, weights of 0.4 and 0.6 were set, respectively, and global optimization was performed within the experimental range (pH 5–9, dosage 1.5–3.5 mL / L, rapid stirring time 2–6 min). The optimization results are as follows: As shown.

[0133] surface PSTZ-CTS Response Optimization Results

[0134]

[0135] The optimization results show that the optimal conditions are: pH=7.10, dosage=2.65mL / L, and rapid stirring time=4.83min. Under these conditions, the predicted turbidity removal rate is 98.86% (95% confidence interval: 96.78%–100.93%), and the predicted organic matter removal rate is 96.77% (95% confidence interval: 94.49%–99.05%). The composite optimization score is 1.00, indicating that the model has found an ideal global optimum within the experimental range. To verify the reliability of the model's predictions, an actual verification experiment was conducted under the optimal conditions (pH=7.1, dosage=2.65mL / L, rapid stirring time=4.8min). The verification results are as follows: As shown.

[0136] surface Verification of experimental results under optimal conditions

[0137]

[0138] The measured turbidity removal rate was 97.6% (deviation from the predicted value of 1.26%), and the organic matter removal rate was 97.3% (deviation from the predicted value of 0.47%), with deviations of less than 2%, verifying the accuracy and reliability of the response surface model.

[0139] Compared to PSTZ, the PSTZ-CTS composite coagulant has a wider optimal pH range. As analyzed earlier, PSTZ's removal rate decreases significantly when the pH deviates from neutral. However, with the organic modification of chitosan, the optimal pH of PSTZ-CTS extends to 5.5–8.0. This is due to the additional charge neutralization and adsorption bridging capabilities provided by the cationic amino groups of chitosan over a wider pH range, making the composite coagulant more tolerant to pH fluctuations in actual water bodies.

[0140] 5. Flocculation Mechanism Analysis

[0141] like As shown, the Zeta potential of the water sample after PSTZ-CTS composite coagulant addition showed a significant positive shift with increasing dosage, reflecting a typical flocculation process dominated by charge neutralization mechanism. At pH 5, the initial Zeta potential was approximately -18 mV. As the dosage increased from 1.5 mL / L to 3.5 mL / L, the Zeta potential gradually rose from -10.5 mV to +8.0 mV, crossing the isoelectric point (around 3.0 mL / L), indicating that the coagulant hydrolysis products effectively neutralized the negative charge on the particle surface, promoting charge neutralization and subsequent flocculation. Further increasing the dosage to 3.5 mL / L resulted in a significantly positive Zeta value, indicating that excessive addition triggered particle restabilization. At pH 7, the initial Zeta potential was approximately -28 mV, rising to +1.8 mV at a dosage of 2.5 mL / L, close to zero, achieving optimal charge neutralization. At 3.5 mL / L, it further increased to +10.5 mV, also reflecting restabilization. At pH 9, the initial Zeta potential was more negative (approximately -35 mV). The Zeta potential increased slowly with increasing dosage, reaching +4.0 mV at 3.5 mL / L. This indicates that the positive charge strength of the coagulant hydrolysis products weakens in an alkaline environment, leading to a decrease in charge neutralization efficiency. However, a near-isoelectric point can still be achieved with appropriate dosage, and a high removal rate is maintained through the adsorption bridging and net-sweeping mechanism of chitosan. Overall, increasing pH leads to a greater negative initial Zeta potential, requiring a higher dosage to approach the isoelectric point. Excessive dosage generally induces a positive shift in the Zeta potential and a decrease in removal efficiency. These results confirm that the PSTZ-CTS composite coagulant mainly exerts its flocculation efficiency through charge neutralization, with an optimal dosage of approximately 2.5–3.0 mL / L, significantly regulated by pH. Compared to pure PSTZ, chitosan modification allows the Zeta potential to effectively approach zero across the entire pH range of 5–9, significantly widening the pH adaptation window and demonstrating significant synergistic effects.

[0142] 6. Analysis of the treatment effect of low turbidity water

[0143] For low-turbidity water samples with an initial turbidity of 10.0 NTU, the PSTZ-CTS composite coagulant exhibited significantly better flocculation performance than PSTZ. For example... As shown, under conditions of pH=7 and rapid stirring time of 4 min, the turbidity removal rate of PSTZ-CTS at all dosage levels was higher than that of pure PSTZ, with an improvement of 9.8%–14.3%. At the optimal dosage of 2.5 mL / L, the removal rate of PSTZ-CTS reached 96.8%, while that of PSTZ was only 85.1%, with a residual turbidity of about 1.5 NTU, making it difficult to achieve deep purification. Low-turbidity water has a low particle concentration and few collision opportunities. Pure PSTZ mainly relies on charge neutralization and net sweeping, resulting in small and loose flocs with slow settling. The addition of chitosan significantly enhances the adsorption bridging effect. Its long-chain cationic amino groups connect dispersed particles into large and dense flocs through electrostatic adsorption and hydrogen bonding, resulting in fast settling speed and significantly improving the removal efficiency of low-turbidity water. Furthermore, PSTZ-CTS maintained a high removal rate even with excessive dosage (3.5 mL / L) and exhibited better tolerance than pure PSTZ, indicating that the composite coagulant has a wider operating window and higher stability in the treatment of low-turbidity water.

[0144] This invention optimized the preparation conditions of the composite coagulant using response surface methodology and systematically studied its effects on turbidity and organic matter removal efficiency in water treatment. Experimental results showed that the optimal preparation conditions for the PSTZ-CTS composite coagulant were: pH = 7.1, dosage = 2.65 mL / L, and rapid stirring time = 4.8 min. Under these conditions, the predicted turbidity removal rate of the PSTZ-CTS composite coagulant was 98.86% (95% confidence interval: 96.78%–100.93%), and the predicted organic matter removal rate was 96.77% (95% confidence interval: 94.49%–99.05%). The actual turbidity removal rate and organic matter removal rate were 97.6% and 97.3%, respectively, indicating that the coagulant exhibited extremely high removal efficiency under these conditions.

[0145] (1) Optimization results of response surface methodology

[0146] Response surface methodology (RSM) optimization results show that pH has a significant impact on the removal efficiency of PSTZ-CTS coagulant. At pH 7.1, PSTZ-CTS exhibits the best charge neutralization effect, with a Zeta potential close to zero, promoting particle aggregation and sedimentation in the water.

[0147] (2) Optimization of dosage and stirring time

[0148] Response surface methodology experiments determined that the PSTZ-CTS composite coagulant exhibited the highest removal efficiency at a dosage of 2.65 mL / L and a rapid stirring time of 4.8 min. With increasing dosage, the Zeta potential of the PSTZ-CTS composite system gradually approached zero, achieving optimal charge neutralization and reducing electrostatic repulsion between particles, thus promoting floc formation and sedimentation.

[0149] (3) Mechanism of action of PSTZ-CTS composite system

[0150] The advantages of the PSTZ-CTS composite system mainly stem from the introduction of CTS. The interaction between the polymer structure of CTS and PSTZ particles forms a more complex bridging and netting structure, which enhances the composite system's effectiveness in treating low-turbidity water samples. Furthermore, the addition of CTS improves the dispersibility of PSTZ, resulting in stronger repulsive forces between particles and further optimizing the coagulation effect.

[0151] (4) Optimal coagulant preparation conditions

[0152] Based on the optimization results of the comprehensive response surface methodology, the optimal preparation conditions for the PSTZ-CTS composite coagulant were determined to be pH=7.1, dosage=2.65 mL / L, and rapid stirring time=4.8 min. Under these conditions, the removal efficiency of turbidity and organic matter reached its maximum. With increasing dosage, the electrical properties of the composite system gradually approached the isoelectric point, achieving optimal charge neutralization and promoting pollutant removal.

[0153] (5) Application prospects and applicability

[0154] This invention demonstrates that the PSTZ-CTS composite coagulant can effectively remove suspended solids and organic pollutants from water under different pH conditions, exhibiting the best coagulation effect, especially at pH=7.1. The PSTZ-CTS composite system is not only suitable for neutral and weakly acidic environments, but also maintains good stability in alkaline water samples, showing broad application prospects.

[0155] (6) Performance in low-turbidity water samples

[0156] In low-turbidity water samples, the PSTZ-CTS composite coagulant consistently outperformed PSTZ alone. Even at low dosages, PSTZ-CTS maintained a high removal rate, demonstrating its excellent adaptability to low-turbidity water samples. Particularly at a dosage of 2.5 mL / L, the removal rate of PSTZ-CTS was significantly higher than that of PSTZ alone, indicating that the addition of CTS effectively enhances the removal capacity of PSTZ in low-turbidity water samples.

[0157] It should be noted that the specific embodiments described above enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail with reference to the accompanying drawings and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention patent.

Claims

1. A method for preparing a polyzirconium titanium silicate-chitosan composite flocculant, characterized in that, Includes the following steps: Step 1, Preparation of chitosan acetate solution: Dissolve chitosan in dilute acetic acid solution to prepare chitosan acetate solution; Step 2: Preparation of polytitanium zirconium silicate-chitosan composite flocculant: Under water bath conditions, the chitosan acetic acid solution is added to the polytitanium zirconium silicate salt solution, stirred and polymerized evenly, the pH value of the solution is adjusted, and stirring and polymerization are continued until the solution is matured to obtain the polytitanium zirconium silicate-chitosan composite flocculant.

2. The preparation method of the polyzirconium titanium silicate-chitosan composite flocculant according to claim 1, characterized in that, In step 1, the concentration of the dilute acetic acid is 0.1 mol / L, and the chitosan acetic acid solution contains 1 wt.% chitosan by weight.

3. The preparation method of the polyzirconium titanium silicate-chitosan composite flocculant according to claim 1, characterized in that, In step 2, the mass ratio of chitosan to polyzirconium titanium silicate is 0.2-0.4, the polyzirconium titanium silicate salt is polyzirconium titanium silicate chloride, the pH is adjusted to 1.5-3.5 with sodium hydroxide solution, the polymerization is continued for 1 hour with stirring, and the curing is carried out for 24 hours. The polymerization temperature of chitosan and polyzirconium titanium silicate is 20-50℃.

4. The preparation method of the polyzirconium titanium silicate-chitosan composite flocculant according to claim 1, characterized in that, In step 2, adjust the pH of the solution to 2.5–3.

5.

5. A polysilicate titanium zirconium-chitosan composite flocculant prepared by the method according to any one of claims 1-4.

6. The application of the polysilicate titanium zirconium-chitosan composite flocculant as described in claim 5 in drinking water pretreatment, urban sewage and industrial wastewater treatment.

7. The application according to claim 6, characterized in that, Determining the flocculation conditions of the composite flocculant in water treatment using response surface methodology includes the following steps: Step 71: Add the composite flocculant to the water treatment system; Step 72: Using the response surface methodology, with pH, ​​the amount of composite coagulant added, and the rapid stirring time as independent variables, and turbidity removal rate and organic matter removal rate as response variables, a second-order polynomial regression model is established to predict the optimal flocculation conditions. Step 73: Determine the optimized combination of flocculation parameters based on the model; Step 74: Perform water treatment operations according to the optimized combination of flocculation parameters.

8. The application according to claim 7, characterized in that, In step 72, the regression equation for the turbidity removal rate is: Turbidity removal rate = -84.1 + 34.08 pH + 31.74 Dosage + 7.94 Rapid stirring time - 2.258 pH² - 6.457 Dosage² - 1.109 Rapid stirring time²; The regression equation for the organic matter removal rate is: Organic matter removal rate = -98.3 + 35.75 pH + 34.80 dosage + 8.98 rapid stirring time - 2.389 pH² - 6.913 dosage² - 1.306 rapid stirring time²; The unit for rapid stirring time is min, and the unit for dosage is ml / L.

9. The application according to claim 8, characterized in that, In step 73, the optimal flocculation conditions were determined as follows: pH=7.10, dosage=2.65mL / L, and rapid stirring time=4.83min.

10. The application according to claim 8, characterized in that, In step 74, water treatment is performed based on the optimized combination of flocculation parameters, with a predicted turbidity removal rate of 98.86% and a predicted organic matter removal rate of 96.77%.

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