Removal of cd(II) from aqueous solution by clay-biochar composite prepared from Alternanthera philoxeroides and bentonite

Abstract

A novel bentonite-biochar (APB) composite was prepared by incorporating bentonite (BE) with Alternanthera philoxeroides (AP) biochar for the adsorptive removal of Cd(II) from aqueous media. The APB and the pristine biochar (PB) prepared from the AP were produced at 300 °C under a nitrogen environment. The adsorption capabilities of the BE, PB, and APB were tested for the removal of Cd(II) from aqueous solution. The results showed that the pH substantially affected the adsorption of Cd(II) by the PB and APB. The adsorptive capacity of the Cd(II) onto the PB and APB gradually increased as the pH was increased to 6.0, and there was no significant change in adsorption as the pH was further increased to 8.0. The adsorption kinetic data of the PB and APB were fitted to a pseudo-second-order (PSO) adsorption kinetic model and an intraparticle diffusion (ID) model. The Freundlich model matched the experimental data better than the Langmuir model, indicating that the adsorption was heterogeneous. Thermodynamic study revealed that the adsorption was mainly physisorption, and the adsorption process was endothermic and spontaneous, while the orderliness of all adsorption systems decreased. The results demonstrated that the APB was an effective adsorbent for the removal of Cd(II) from aqueous media.