Recent Advances on Magnetic Natural Coagulant: a Mini Review

Abstract

Utilisation of natural coagulants in water and wastewater treatment has gained a considerable amount of interest in recent years. This is possible due to its advantages such as being renewable, being affordable at a relatively low cost, producing biodegradable sludge with less sludge generation. However, there are some drawbacks in the utilisation of natural coagulant, namely its long settling time and increase of organic content when a crude plant extract is used. To surmount these obstacles, a combination of magnetic iron oxide nanoparticle (IONP) with natural coagulant (i.e. magnetic natural coagulant) is introduced to enhance the coagulation performance. The purpose of this review is to provide extensive discussions on the recent progress of magnetic natural coagulant, especially over the last ten years. Most of the recent studies used protein extract from legumes as an active coagulating agent in the magnetic natural coagulant preparation with two different approaches. The dispersion approach used crude extract functionalised with IONP, while the adsorption approach immobilised protein on the surface of unmodified or modified IONP. In both approaches, protein acts as an active coagulating agent with a charge neutralisation mechanism. Due to the presence of IONP, the settling time is greatly reduced under the presence of external magnetic force, typically from 60–90 min to 5–30 min, while maintaining a good coagulation performance in various types of water – wastewater. Future studies of other coagulant preparation methods, applications to other active coagulating agents, and efforts to increase the coagulation efficiency are needed prior to its pilot – commercial scale application.