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

Abstract

Abstract The removal of arsenic from water remains a major challenge. Graphene-based material is widely used to remove arsenic from water due to their layered structure with high surface area. However, the removal of arsenic from water by iron- lanthanum (Fe-La) functionalized graphite sheets is rarely reported. Here, we have successfully fabricated nanoscale graphite sheets and synthesized Fe-La modified nanocrystalline hybrid material to efficiently removal As(III) from aqueous solution. The X-ray diffraction (XRD), Atomic Force Microscope (AFM), Fourier Transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and zeta potential were used to characterized the morphology, functional groups, crystalline structure and valance state of materials to explore the effect and mechanism of Fe-La-graphite sheets (FL-graphite sheets) on As(III) removal from water. The material had the rough surface and Fe/La were evenly distributed on its surface. The results of As(III) adsorption experiments showed that the adsorption density of FL-graphite sheets for As(III) was 51.69 mg·g− 1, which was higher than that of graphite sheet (21.91 mg·g− 1), La-graphite sheet (26.06 mg·g− 1) and Fe-graphite sheet (40.26 mg·g− 1). The FL-graphite sheets conformed to the Freundlich adsorption isotherm, and the maximum adsorption density was 53.62 mg·g− 1. The pseudo second-order provided the best simulation for data of As(III) adsorption experiments, indicating that chemical reactions are the main rate-control step. XRD, XPS, and FTIR analysis revealed that the oxidation and complexation reaction on the surface of FL-graphite sheet was the main mechanism of As(III) removal. Ecotoxicity assessment revealed that FL-graphite sheets has little influence on rice germination and growth, but reduced the toxicity of As(III) to rice by forming protective film in rice rhizosphere. Therefore, the FL-graphite sheets has good practical application value in purifying As(III) polluted water with litter ecotoxicity.