Diatomite-chitosan composite with abundant functional groups as efficient adsorbent for vanadium removal: Key influencing factors and influence of surface functional groups

Abstract

In this study, a diatomite-chitosan composite (CS-DE-10 %) was prepared through an in-situ self-assembly method to efficiently remove vanadium (V) from wastewater for the first time. The CS-DE-10 % composite showed higher removal efficiency (96.5 %) for vanadium than diatomite and chitosan alone, meanwhile, which can effectively decrease the toxicity of vanadium by reduce V (V) to V (IV) due to its functional groups that can provide the active atoms. The possible reason for the improved adsorption capacity of the CS-DE-10 % adsorbent was the enhanced specific surface area and pore volume, which increased by about 9 and 4 times in contrast with pure chitosan. Additionally, functional groups in the composite, such as OH, CO, CO, NCO and NH2, also contributed to the enhanced removal ability. Moreover, the pseudo-second order kinetic model and Freundlich isotherm model can better describe the adsorption process, and the adsorption process included three distinct regions: bulk, film, and pore diffusion based on the intraparticle diffusion model. Besides, physical adsorption, electrostatic interaction and surface complexation were involved in the adsorption process. This work suggests that the diatomite-chitosan composite may be used as a promising, efficient, and environmentally friendly adsorbent for the remediation of heavy metal pollution.