Use of NIR/NaBH4 combinatorial techniques for simultaneous and high-efficient adsorption of heavy metal ions from contaminated water by Chitosan/Au Janus microdisks

This article discusses the creation of a disk-shaped microsorbent with Janus morphology made with chitosan and coated with gold on one side using the sputtering technique. The aim of the research is to explore how sodium borohydride and near-infrared (NIR) light can enhance the adsorption of heavy metal ions by our synthesized adsorbent. The changes in surface morphology and composition of the chitosan part of Janus microdisks, after acid treatment and crosslinking reaction, before and after adsorption process were investigated through scanning electron microscopy (SEM). The chitosan/Au Janus microdisks were utilized in auto-catalyzed adsorption of heavy metals including, Pb, Cu, Cd, Zn, and Ni, in the presence of sodium borohydride. The isotherm, kinetic, and thermodynamic curves of adsorbance in the presence of metals were investigated. In addition, the performance of Janus microsorbents in the co-existing ions solution was studied under different conditions. The synthesized microsorbents can remove Cu ions selectively from contaminated water (>99 %) with the help of sodium borohydride. In addition, the NIR light irradiation exhibited a synergistic effect on the adsorption of Cd, Ni, and Pb ions in the presence of sodium borohydride. The borohydride ions can change the surface charge of microdisks after adsorption on their surface and increase the adsorption rate of metal cations. In addition, NIR light irradiation can accelerate the reaction of sodium borohydride with metal ions.