Removal of arsenic from wastewater using mixed metal hydroxides and biopolymers

Abstract

Arsenic is one of the contaminants in wastewater which becomes a worldwide environmental problem. Therefore, several simple and cost-effective techniques have been developed for arsenic removal. This study reports on the removal of arsenic by coprecipitation method with variable combinations of the well-known metal salts, such as FeCl3 or AlCl3 with the environmentally friendly inorganic metal salts, such as MgCl2 or CaCl2, which is called “mixed metal system”. Moreover, for improving the low toxicity from sludge production, hence the coprecipitation techniques using mixed metal salts as coagulants combine with biopolymers (alginate or chitosan) as flocculants for arsenic removal were also studied. Under the optimum conditions, the results showed that the arsenic removal efficiency from simulated wastewater were about 95.4% and 96.8%, at pH9 by using 2.5MgFe/As and 2.5CaFe/As, consecutively. In addition, the arsenic removal efficiency of the combination between mixed metal and biopolymer systems were increased at pH9 for 0.7%w/v of alginate combine with 1.25MgFe/As, and it also increased at pH7 for 0.7%w/v of alginate combine with 1.25, 1.5 and 2.0CaFe/As system.