Treatment of lead contaminated water using synthesized nano-iron supported with bentonite/graphene oxide

Abstract

Conventional nano-iron is widely used in heavy metal contaminated groundwater remediation. However, it is easily oxidized when exposed to the air or re-aggregated under water soaking conditions. In this study, a nano-sized iron supported by graphene oxide/bentonite is proposed which is synthesized by liquid-phase reduction method. The TEM test results showed that the support effect of graphene oxide/bentonite well solved shortcomings of conventional nano-iron, since the flaky structure of graphene oxide and layered bentonite could effectively disperse nano-iron particles. The TEM images indicated that nano-iron supported by graphene oxide/bentonite at a weight ratio of 4:1:7.3 (nanoiron:graphene oxide:bentonite) yielded the smallest particle size, and most particle size was less than 30 nm. The test results show that addition of graphene oxide could improve the removal of lead ions, especially in acidic environment as compared to bentonite alone supported nano-iron. The optimum dosage of graphene oxide was found to be 6.98% based on the removal rate of lead. It was found that the removal rate of lead by graphene oxide/bentonite supported nano-iron increased with the increase of pH of simulated contaminated groundwater. The temperature was found to affect the removal rate of lead ions as well. The adsorption of lead ions by graphene oxide/bentonite supported nano-iron conformed to quasi-second order reaction kinetic model, and the adsorption isotherm well fit the Langmuir model. Keywords: Graphene oxide, Bentonite, Nano-iron, Lead ions, Removal rate