Prospectives on Application of Magnetic Powders from Coal Fly Ash for Wastewater Treatment

Abstract

Magnetic separation is a method for separating particles based on their magnetic properties. Application of magnetic powders (MP) from coal fly ash (CFA) for wastewater treatment has been considered to be a promising approach to improving the separation efficiency. This paper aims to review the perspectives on application of magnetic powders from coal fly ash (MP-CFA) for wastewater treatment based on three major technological functions. MP-CFA can enhance the treatment ability of phosphorate removal through magnetic flocculation-sedimentation process. Among three commonly used phosphorus removal coagulants, i.e., ferric chloride, aluminum sulfate and poly aluminum chloride (PAC), the addition of MP results in the best performance for the floc settling of PAC coagulation. The alkali modified MP can further improve the coagulation precipitation for chemical phosphorus removal. MP-CFA also can enhance the removal of heavy metals by adsorption and chemical precipitation. The MP effectively adsorbs copper ions at low concentration by removing copper ions through chemical precipitation, which can be speed up by adding the magnetic powder, especially using the alkali modified MP. MP-CFA can be delivered to activated sludge process to improve the solid-liquid separation of sludge from treated wastewater. Activated sludge supplemented with MP exhibits excellent settleability and concentration of mixed liquid volatile suspended solids (MLVSS) can be greatly increased to enhance volumetric biotreatment capacity.