Novel Bio-Sorbent for Arsenic Removal from Aqueous Solution: Kinetics, Isotherms, and Thermodynamics

Arsenic is known as a potential threat to the environment. Therefore, this research aims to assess the arsenic removal efficiency from an aqueous solution, by a novel bio- sorbent based on the Sour-Lemon Peel (SLP). To treat SLP, a combination of two methods (treated with mineral acids and high temperature) was used, and a designed bio-sorbent called SLP-activated/ carbonized. The SLP-activated and SLP- carbonized were also prepared using hydrochloric acid (HCl) and 400°C temperature, respectively, to compare the results of each of the three methods. Afterward, adsorption parameters such as pH, initial ion concentration, bio-sorbent dosage, contact time, and temperature were assessed. It was found that the combination method has provided a higher adsorption capacity so that, up to ~99% arsenic removal was observed with SLP-activated/carbonized at pH of 7.0 and 40°C. The adsorption capacities for SLP- carbonized and SLP-activated were 87.92% (pH:7, 60°C) and 78.50% (pH:6, 90°C), respectively. Moreover, adsorption kinetics data indicated the best fit with the pseudo-second-order model. The maximum bio-sorption capacity by the Langmuir isotherm model was also recorded for SLP-activated/carbonized (53.47 mg/g). Notably, arsenic adsorption on studied bio-sorbents takes place spontaneously and through chemisorption along with the endothermic nature of the bio-sorption process and reduction of random collisions in the solid-liquid phase.