Red Mud-Based Polyaluminum Ferric Chloride Flocculant: Preparation, Characterization and Flocculation Performance

Abstract

In this work, red mud was used as raw material to extract Al and Fe with hydrochloric acid. The high-efficiency polyaluminum iron chloride (PAFC) flocculant was prepared via adjusting the pH of the leaching solution, the molar ratio of aluminum and iron, and the polymerization temperature. The effect of synthesis and flocculation conditions on the flocculation performance of aged landfill leachate was investigated. The results confirmed that the PAFC prepared at the polymerization pH of 2.5, the Al/Fe molar ratio of 8, and the polymerization temperature of 70 °C had the optimum flocculation effect. The flocculation consequences of PAFC and commercial polyaluminum iron chloride flocculant (CPAFC) under different flocculation conditions were compared. The chemical oxygen demand (COD), UV254, chroma and settlement height of PAFC at flocculant concentration of 60 g/L and solution pH of 6 were 72.2%, 79.2%, 82.9% and 9.5 cm (within 90 min), respectively. PAFC has excellent flocculation performance and can be used as a simple, potentially low-cost wastewater treatment agent in industrial applications.