Iron-lanthanum supported on graphite sheets for As(III) removal from aqueous solution: kinetics, thermodynamic and...

Graphene-based material is widely used to remove arsenic from water due to its layered structure with high surface area. Here, we have successfully synthesized Fe-La bimetallic modified graphite sheet materials to more efficiently remove As(III) from aqueous solution. The results showed that Fe-La-graphite sheets (FL-graphite sheets) have a larger specific surface area (194.28 m²·g^-1) than graphite sheets (2.80 m²·g^-1). The adsorption capacity of FL-graphite sheets for As(III) was 51.69 mg·g^-1, which was higher than that of graphite sheets (21.91 mg·g^-1), La-graphite sheets (26.06 mg·g^-1), and Fe-graphite sheets (40.26 mg·g^-1). The FL-graphite sheets conformed to the Freundlich and Dubinin-Radushkevich isotherm, and the maximum adsorption capacity was 53.62 mg·g^-1. The removal process obeys intra-particle diffusion and pore diffusion for As(III). The results of batch adsorption experiments and characterization analyses demonstrated that oxidation, ligand exchange, and inner sphere complexation mechanisms involved in the adsorption of FL-graphite sheets to As(III) in comparison with graphite sheets. In addition, electrostatic attraction mechanism was found vital in the adsorption. Ecotoxicity assessment revealed that FL-graphite sheets have little influence on rice germination and growth, but reduced the toxicity of As(III) to rice. Therefore, the FL-graphite sheets have good practical application value in purifying As(III) polluted water with litter ecotoxicity.