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.
