Response surface modeling,isotherm, thermodynamic and optimization study of arsenic (V) removal from aqueous solutions using modified bentonite-chitosan (MBC)

Arsenic contamination, a worldwide concern, has received a great deal of attention due to its toxicity and carcinogenicity. In the present study, we focused on the combined application of modified bentonite and chitosan (MBC) for the removal of As(V). Arsenic removal experiments were carried out to determine the amount of As(V) adsorbed as a function of pH (2-8), sorbent dosage (0.1-1.5 g/L), As(V) concentration (20-200mg/L) and time (60-240 min). The system was optimized by means of response surface methodology. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant (R²≈97.3%). Optimized values of pH, sorbent dosage, initial As(V) concentration and time were found to be 3.7, 1.40 g/L, 69mg/L, and 167min, respectively. The results reveal that the prepared adsorbent has a high adsorption capacity (122.23mg/g) for As(V) removal. Among the isotherm models used, the Langmuir isotherm model was the best fit for the obtained data. The adsorption kinetics following a pseudo-second-order kinetic model was involved in the adsorption process of As(V). Thermodynamic studies confirmed the spontaneous and endothermic character of adsorption process.