Adsorption of crystal violet dye by agricultural rice bran waste: Isotherms, kinetics, modeling and influencing factors

Abstract

In this study, the potential of modified rice bran (MRB) was investigated for the elimination of crystal violet (CV) from plotted effluent. In this regard, rice bran (RB) was modified by chlorosulfonic acid. The results of FTIR, EDX, and SEM analysis showed structural change, an increase in the amount of sulfur, and the formation of a new band (998 and 1,225 cm-1) in MRB, respectively. The impact of different variables such as contact time, MRB dosage, pH, CV concentration, and ions content on removal efficiency was studied by using batch experiments. In addition, response surface methodology was employed to optimize the experiments. The maximum removal efficiency of 97.4% was obtained at the adsorbent dosage of 2 g L-1, initial CV concentration of 100 mg L-1, and contact time of 42.75 min. The highest adsorption capacity of 603 mg g-1 was acquired by the Langmuir model. The best description of kinetic data was achieved by the Elovich model. The thermodynamic study of the adsorption indicated an endothermic and spontaneous reaction. MRB could be regenerated by HCl 0.5 mol L-1 and removal efficiency was declined 10 percent after 5 adsorption/desorption cycles. It was concluded that MRB is an operational adsorbent to remove CV from effluents.