Statistical modeling of phenolic compounds adsorption onto low-cost adsorbent prepared from aloe vera leaves wastes using CCD-RSM optimization: effect of parameters, isotherm, and kinetic studies

The experiments were designed based on the central composite design (CCD) and were analyzed and modeled by response surface methodology (RSM) to demonstrate the operational variables and the interactive effect of four independent variables on two responses. The results showed that the adsorption rates of both phenolic compounds (bisphenol A and pentachlorophenol) were increased by increasing contact time and adsorbent dose. The highest phenolic compounds adsorption was obtained at a pH of 6. Based on the analysis of variance of the results obtained from different models, a quadratic model was chosen to estimate the removal of phenolic compounds by the adsorption process using modified sorbent. The linear regression coefficient ( R 2 ) between experiments and different response values in the model was 0.96 for bisphenol A and 0.75 for pentachlorophenol. The optimum values for the studied variables were the pH of 6, the adsorbent dose of 4.2 g/L, the contact time of 65 min, and the concentration of the phenolic compounds of 40 mg/L. Under the mentioned conditions, the removal efficiency of pentachlorophenol and bisphenol A by the adsorbent was 93.1% and 87.06%, respectively. According to the results, the modified adsorbent in the removal of phenolic compounds follows the Freundlich isotherm and pseudo-second-order kinetics. The results showed that the adsorption onto modified adsorbent was able to provide the relatively high removal efficiency of phenolic compounds. This method can also be used to treat wastewater from petroleum and petrochemical industries containing phenolic compounds.