Sb(III) removal from aqueous solution by a novel nano-modified chitosan (NMCS)

A series of environmental and health problems caused by the release of large quantities of antimony into the water environment have received wide social concern in a number of regions worldwide. Finding a feasible treatment technology is the best choice for the sustainable remediation of antimony pollution. A novel nano-modified chitosan (NMCS) was prepared by grafting iron oxide nanoparticles (Nano-Fe3O4) and carboxylate metal organic frameworks (MOFs) denoted as MIL-100(Fe) onto chitosan. The NMCS before and after adsorption was characterized by analytical tools including Fourier transform infrared and X-ray photoelectron spectroscopy. Batch experiments with variable NMCS dose, solution pH, and competing anions were used to evaluate the most efficient way to remove Sb (III) from aqueous solutions. The results showed that removal efficiency increased with the increase of the NMCS concentration and solution pH, respectively. The maximum removal efficiency of Sb(III) was 96.8%, at pH 11 with 1.5 g/L of NMCS when treating a Sb(III) model solution of 10 mg/L, which is much higher than that with Nano-Fe3O4 or MOFs. Compared with the efficient removal of Sb(III) under acid conditions, NMCS has a higher removal efficiency under alkaline conditions. The effect of common anions such as sulfate, carbonate, nitrate and chloride ions, on the removal of Sb(III), was minor. The removal of Sb(III) could be clearly described by pseudo-second order sorption kinetics and Freundlich isotherm, which suggested inner-sphere surface binding mechanisms. The presence of Sb (III) on NMCS was confirmed by an X-ray photoelectron spectroscopic analysis, and those functional groups binding to Sb (III) were identified using Fourier transform infrared analysis. The ability of NMCS to be regenerated was good and further enhanced by the possibility of magnetic recovery. Overall, the findings tested in this study showed that the NMCS developed can effectively remove Sb(III) from aqueous solutions and can be effectively recovered and reused.