Evaluation of Polymeric Silico-Aluminum-Ferric Coagulant (PSAC) Derived from Volcanic Rock in Removal of Algae and Phosphorus from Water

Coagulation is a core technology for treating micro-polluted water containing algae and phosphorus. The development of a new coagulant is crucial for reducing operational costs in water treatment plants and similar enterprises. However, compared with traditional chemical coagulants, mineral-based materials have received relatively less attention in the development of high-efficiency coagulants, and their application potential remains to be fully explored, while traditional coagulants such as polyaluminum chloride (PAC) still dominate the market. This study investigated the effectiveness of a polysilicate aluminum ferric coagulant (PSAC) derived from volcanic rock. The influence of various parameters during synthesis and application on PSAC performance was examined, including NaOH dosage, polymerization temperature, silicic acid content, aging time, water environment pH, water quality type, and coagulant dosage. Performance was evaluated based on the removal efficiency of turbidity, UV254, algae density, and total phosphorus. The results showed that the optimal preparation conditions for PSAC are: NaOH dosage of 8 mL, polymerization temperature of 60 °C, inclusion of silicic acid, aging for 72 h, and a pH range of 7–8. Under these conditions, the coagulant demonstrated high removal efficiency for the targeted pollutants. At a PSAC dosage of 80 mg/L, the removal rates for UV254, algae, and total phosphorus were 90.2%, 99.2%, and 96.4%, respectively, with stable coagulation performance observed across different water qualities. Overall, PSAC exhibits good removal efficiency for UV254, total phosphorus, and algae, indicating its great potential as a coagulant for water and wastewater treatment.