Efficient removal of Cr(VI) and bisphenol A by a tannic acid-functionalized porous biochar

Abstract

Heavy metals and organic compounds pose significant environmental risks. In this study, tannic acid-functionalized porous biochar (T-PBC) was prepared at room temperature to remove Cr(VI) and bisphenol A (BPA) from aqueous solutions. Porous biochar was synthesized using a self-blowing method. The modification of TA aimed to increase the surface oxygen-containing functional groups (OFGs). The characteristics and structure of the T-PBC were investigated by SEM, BET, XRD, FTIR, particle size analysis, and XPS. The maximum adsorption capacities for Cr(VI) and BPA at pH 2.50 were 218.71 and 320.51 mg/g, respectively. The adsorption kinetics and isotherms for Cr(VI) on T-PBC were best described by pseudo-second-order kinetic and Langmuir models. Conversely, the adsorption of BPA was best fitted with the pseudo-second-order kinetic and Freundlich models. Two phenomena occur in the binary system of Cr(VI) and BPA: the promotion with adding a low concentration of another pollutant and inhibition by adding high concentrations toward to target pollutant adsorption (Cr(VI)/BPA). In addition, the removal efficiency of Cr (VI) by T-PBC from an electroplating wastewater reached 83.04%. The main adsorption mechanisms for Cr(VI) and BPA on T-PBC were revealed in this study. This work provides a reference for the co-adsorption of heavy metals and organics and indicates the potential application of T-PBC for adsorption of complex pollutants.