Experimental and DFT study on the removal of sulfadiazine by activated carbon prepared from Rubus alceifolius

This study describes the synthesis of activated carbon from locally derived biomass Rubus alceifolius using ZnCl2 as an activating agent for sulfadiazine (SDZ) removal from wastewater. The adsorbent material was characterized by Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), N-2 adsorption-desorption isotherms, and zero-point charge (pH(zpc)). Brunauer-Emmett-Teller (BET) surface area and total pore volume of the synthesized carbon were found to be 233 m(2) g(-1) and 0.16 cm(3) g(-1), respectively. Batch adsorption studies were carried out under varying initial concentrations, adsorbent dosage, temperature, contact time, and pH to comprehend the effects of different operating parameters on the removal efficiency for sulfadiazine from wastewater. The equilibrium isotherm study fitted well with the Langmuir model with maximum adsorption capacity (q(m)) of 29.57 mg g(-1). The adsorption kinetic was best fitted by the pseudo-second-order model. Thermodynamic process of adsorption of SDZ onto activated carbon was found to be spontaneous and endothermic. Theoretical investigations using density functional theory (DFT) calculations suggested that the adsorption of SDZ onto functionalized activated carbon is favorable. Among the oxygen-containing functional groups, the carboxyl group appeared to have the largest effect on the adsorption process. However, DFT calculation showed that the presence of all three oxygen-containing functional groups enhanced the adsorption of SDZ, compared with pristine activated carbon.