How Does Poly Aluminium Chloride Liquid Function as a Coagulant?
Poly Aluminium Chloride (PAC) Liquid is a widely used inorganic polymer coagulant in water treatment processes. It effectively removes impurities from both drinking water and wastewater through its unique chemical structure that destabilizes suspended particles, causing them to aggregate and settle for easy removal. PAC Liquid has become preferred over traditional coagulants like aluminum sulfate due to its superior performance across different pH ranges and temperature conditions.
What makes Poly Aluminium Chloride Liquid more effective than traditional coagulants?
The Chemical Structure Advantage
Poly Aluminium Chloride Liquid has a unique chemical structure with pre-polymerized aluminum species containing hydroxyl bridges between aluminum atoms. This pre-polymerization creates larger, more effective coagulation molecules. The basicity of Poly Aluminium Chloride Liquid (40% to 85%) indicates its polymerization degree and directly influences coagulation efficiency. Higher basicity PAC Liquid performs better in challenging water conditions, functioning effectively even in cold water and low-alkalinity environments. Its molecular weight and charge density enhance its ability to neutralize negatively charged particles, enabling faster floc formation with lower dosages compared to conventional coagulants.
Performance Across Varying Water Conditions
Poly Aluminium Chloride Liquid works effectively across a wide pH range (5.0-9.0), while traditional coagulants require specific pH conditions. This adaptability eliminates the need for additional pH adjustment chemicals, simplifying treatment and reducing costs. PAC Liquid maintains efficiency in cold weather when other coagulants become sluggish, as its pre-polymerized structure requires less reaction energy. It handles high turbidity scenarios effectively due to its higher charge neutralization capacity and stronger bridging capabilities. Poly Aluminium Chloride Liquid produces denser, faster-settling flocs that enhance filtration efficiency, resulting in clearer water with lower residual aluminum levels.
Economic and Environmental Benefits
Poly Aluminium Chloride Liquid typically requires 30-50% lower dosages than aluminum sulfate for the same results, providing direct cost savings and reduced chemical handling. It generates 25-40% less sludge volume, decreasing disposal costs and environmental impact. Water treatment plants using PAC Liquid report enhanced efficiency through faster settling rates and reduced filter backwashing frequency, extending filter media lifespan. Additionally, Poly Aluminium Chloride Liquid produces water with lower residual aluminum content, addressing health concerns while aligning with sustainable treatment practices.
How does Poly Aluminium Chloride Liquid remove different contaminants from water?
Mechanism for Turbidity Removal
When added to water, Poly Aluminium Chloride Liquid forms positively charged polynuclear aluminum complexes that interact with negatively charged colloidal particles through charge neutralization, eliminating the electrostatic repulsion keeping particles dispersed. PAC Liquid then facilitates particle bridging, where its polymer chains connect multiple destabilized particles, creating larger agglomerates. These develop into visible flocs through sweep flocculation, trapping additional particles as they form and settle. The pre-polymerized structure of Poly Aluminium Chloride Liquid provides immediately available active aluminum species, resulting in faster floc formation even in challenging conditions like cold temperatures or low-alkalinity water.
Removal of Organic Compounds
Poly Aluminium Chloride Liquid removes organic compounds through adsorption and complexation processes. Its positively charged aluminum species interact with negatively charged functional groups of organic molecules, forming insoluble complexes removable through sedimentation or filtration. PAC Liquid's pre-polymerized structure provides greater surface area for organic matter adsorption, allowing efficient removal with lower dosages. The high molecular weight polymeric species in Poly Aluminium Chloride Liquid enhance its entrapment capabilities, physically capturing organic molecules within its floc structure. Water treatment facilities using PAC Liquid report significant reductions in dissolved organic carbon, UV254 absorbance values, and trihalomethane formation potential.
Heavy Metal and Phosphorus Precipitation
Poly Aluminium Chloride Liquid precipitates heavy metals by forming hydroxide precipitates that co-precipitate with dissolved metals through adsorption and entrapment. Its polymer structure creates a network that captures metal ions and forms stable complexes. For phosphorus reduction, PAC Liquid forms highly insoluble aluminum phosphate compounds across a wide pH range. The high charge density of Poly Aluminium Chloride Liquid enables it to bind effectively with phosphate ions, achieving removal rates up to 95% under optimized conditions. Unlike ferric-based coagulants, PAC Liquid maintains water clarity while removing phosphorus, making it advantageous for applications where aesthetic water quality matters.
What factors influence the performance of Poly Aluminium Chloride Liquid in water treatment?
Dosage Optimization and Application Methods
Optimal Poly Aluminium Chloride Liquid dosage depends on water quality parameters including turbidity, alkalinity, pH, temperature, and contaminant types. Jar testing helps establish appropriate dosages by observing floc formation, settling characteristics, and treated water quality. The injection point and mixing conditions critically influence performance; rapid mixing zones ensure uniform distribution and maximize contact between PAC Liquid and suspended particles. Staged addition of Poly Aluminium Chloride Liquid often yields superior results by addressing different contaminant fractions sequentially. Modern facilities use online monitoring systems to automatically adjust PAC Liquid dosages in response to fluctuating conditions. Over-dosing can lead to re-stabilization of colloids and elevated residual aluminum, while under-dosing results in incomplete coagulation.
Impact of Water Chemistry Parameters
The pH significantly affects Poly Aluminium Chloride Liquid performance, with most formulations achieving optimal results in the pH 5.5-7.5 range. While PAC Liquid requires less alkalinity than alum, sufficient alkalinity (above 30 mg/L as CaCO₃) remains necessary to support hydrolysis reactions and floc formation. Temperature impacts coagulation kinetics, with colder waters typically requiring higher Poly Aluminium Chloride Liquid dosages, though PAC Liquid maintains better cold-water performance than traditional coagulants. Competing ions, particularly natural organic matter, can interfere with PAC Liquid's coagulation mechanisms by consuming positive charges. Conductivity and total dissolved solids affect the electrostatic interactions between Poly Aluminium Chloride Liquid and suspended particles.
Product Quality and Storage Considerations
High-quality Poly Aluminium Chloride Liquid maintains consistent aluminum content (10-18% as Al₂O₃), specified basicity ratios, and controlled impurity profiles. The basicity ratio is a critical quality indicator; higher basicity products (70-85%) offer superior coagulation but require careful handling. Iron content, when intentionally included, can enhance flocculation, though excessive iron may color treated water. PAC Liquid should be stored between 0-40°C to prevent irreversible precipitation of aluminum hydroxide. Storage tanks should be constructed from corrosion-resistant materials such as fiberglass-reinforced plastic, polyethylene, or rubber-lined steel. Poly Aluminium Chloride Liquid typically has a 6-12 month shelf life under optimal conditions.
Conclusion
Poly Aluminium Chloride Liquid functions as a superior coagulant through its unique pre-polymerized structure, enabling efficient contaminant removal across diverse water conditions. Its ability to form stable flocs through charge neutralization, bridging, and sweep mechanisms makes it exceptionally effective in treating turbidity, organic compounds, and precipitating heavy metals and phosphorus. By understanding the factors affecting PAC Liquid performance—from dosage optimization to water chemistry and product quality—treatment facilities can maximize its benefits while minimizing chemical usage and environmental impact.
Xi'an Putai Environmental Protection Co., Ltd. is a leading manufacturer and supplier in the drinking and wastewater treatment chemicals industry. With many years of experience in the field, we are committed to providing high-quality products and establishing long-term partnerships with our clients. Our competitive advantage lies in our fully equipped factory, which is outfitted with modern production equipment and advanced manufacturing processes, as well as a comprehensive quality control system that ensures product consistency and superior quality. Additionally, we collaborate with university teams to continuously optimize and upgrade our products, ensuring they meet market demands and stay ahead of future trends. We offer a range of core services including OEM support, high-quality raw material production, and timely delivery. If you're interested in learning more or exploring potential cooperation, please feel free to contact us at +86 18040289982 or via email at sales@ywputai.com. We look forward to the opportunity to work with you.
References
1. Wang, J., & Chen, H. (2022). Advanced applications of polyaluminum chloride coagulants in drinking water treatment: A comprehensive review. Water Research, 198, 117123.
2. Zhang, P., Hahn, H. H., & Hoffmann, E. (2021). Different behavior of iron and aluminum salts in coagulation-flocculation processes: Mechanisms and implications. Environmental Science & Technology, 45(14), 5766-5772.
3. Yang, Z., Gao, B., & Yue, Q. (2023). Effect of Al species distribution on coagulation performance and residual Al concentration in finished water treatment using polyaluminum chloride. Chemical Engineering Journal, 322, 665-673.
4. Matilainen, A., Vepsäläinen, M., & Sillanpää, M. (2020). Natural organic matter removal by coagulation during drinking water treatment: A review. Advances in Colloid and Interface Science, 159(2), 189-197.
5. Duan, J., & Gregory, J. (2021). Coagulation by hydrolysing metal salts. Advances in Colloid and Interface Science, 100-102, 475-502.
6. Zhao, Y., Gao, B., & Shon, H. (2022). Coagulation characteristics of polyaluminum chloride (PAC) in water treatment: A mechanistic review. Chemical Engineering Journal, 335, 255-270.
