Ultrasonic assisted removal of methyl orange and bovine serum albumin from wastewater using modified activated carbons: RSM optimization and reusability

The removal of industrial pollutants from water remains a significant challenge in water treatment processes. This study investigated the efficacy of powder-activated carbon (PAC), thermally modified PAC (TPAC), and chemically modified PAC (CPAC) for removing bovine serum albumin (BSA) and methyl orange (MO) from simulated wastewater. After undergoing treatment, the BET surface area of TPAC increased to 823 m2 g−1, while that of CPAC increased to 657 m2 g−1 compared to the initial surface area of pristine PAC, which was 619 m2 g−1. Batch adsorption experiments assisted by ultrasonication were conducted to evaluate the impact of solution pH, initial concentration, and contact time on the adsorption capacities (qmax) of BSA and MO. TPAC demonstrated superior performance, achieving qmax values of 152 mg g−1 for MO and 133 mg g−1 for BSA, compared to PAC, which provided qmax values of 124 mg g−1 and 112 mg g−1, respectively. Furthermore, pH levels of 3 and 5 were identified as highly effective for the removal of MO and BSA from water, respectively. The adsorption kinetics of both MO and BSA followed pseudo2nd-order (R2 > 0.99) reaction kinetics under both batch and ultrasonic conditions, confirming the removal of contaminants through chemisorption. The adsorption trends also satisfied the Langmuir isothermal model, indicating the formation of a uniform monolayer during the adsorption process of these contaminants. To understand the simultaneous effect of all the variables, response surface methodology (RSM) using central composite design (CCD) was used to predict the adsorption capacities of CPAC. After five adsorption cycles, the removal efficiencies of MO (from 98% to 80%) and BSA (from 55% to 40%) decreased in the CPAC system. The results suggested that CPAC can be effectively utilized to remove MO from wastewater.