Efficiency of chitosan catalyst in removing malachite green from their aqueous solutions

This paper describes a green method for treating chemical contamination caused by malachite green from their aqueous solutions using chitosan as a solid catalyst under suitable reaction conditions, including dye concentrations, reaction time, catalyst amounts, and pH. Using UV-Visible measurements, complete removal (99%) was achieved under reaction conditions (80 ppm, 2 hr., 0.08 g, and pH = 11), respectively. The removal reaction was caused by chemical adsorption on the chitosan surface by using Fourier transform infrared (FT-IR) spectroscopy. The chitosan spectrum was clearly changed after treatment as well as exhibiting absorption bands was appeared and vanished in the fingerprint region (400–1400 cm-1). Additionally, new bands were seen in the broad band of (O-H) groups at (3415.93-3462.22 cm-1) and secondary imine groups at (1604.77 cm-1) and at double-bond region (1500-2000 cm-1). Accordingly, changes in the catalyst surface were observed both before and after the removal reaction using atomic force microscopy (AFM). Furthermore; the Nano scale characteristics, surface roughness, particle size, and topography parameters were examined. The surface area increased dramatically from (953.9 to 5224 nm²) and the mean diameter of the surface particles increased significantly from (23.70 to 54.94 nm), these changes were resulted from the malachite green adsorption on the surface. With the arithmetic mean height increasing from (18.65 to 45.01 nm) and the root-mean-square height increasing from (20.49 to 50.27 nm), the topological parameters of the chitosan surface also showed a significant increase in roughness. The results clearly indicated that the removal reaction occurred on the chitosan surface through its high chemisorption capacity and catalytic oxidation of malachite green.