Optimization and modelling of Cd(II) removal from aqueous solution with composite adsorbent prepared from Alternanthera philoxeroides biochar and bentonite by response surface methodology

Abstract

The current study aimed to optimize Cd(II) removal from aqueous solutions by a composite adsorbent (BCB) prepared from Alternanthera philoxeroides (AP) biochar (BC) and bentonite (BE) using response surface methodology (RSM). The results showed that the loading of BE did not significantly change the microstructure of BC but increased the number of functional groups. The X-ray diffraction (XRD) analysis showed that precipitation was the primary mechanism of Cd(II) adsorption. The adsorption behavior for Cd(II) fitted the Freundlich model. The pH, adsorbent dosage, and initial Cd(II) concentration were the main influencing factors affecting Cd(II) adsorption. There were significant interactions between pH and adsorbent dosage, adsorbent dosage, and initial concentration. The optimum adsorption conditions for Cd(II) with the maximum adsorption level of 89.4% were: 6.55 pH, 0.04 g adsorbent dosage, and 68.7 mg∙L-1 initial concentration. Overall, the BCB exhibited great potential as an efficient sorbent for the Cd(II) removal from aqueous solutions.

Interactive Effects of Inorganic–Organic Compounds on Passivation of Cadmium in Weakly Alkaline Soil

“…Therefore, the excellent specific adsorption or surface complexation ability of MnO 2 for Cd may substantially contribute to the greatest synergistic effects of MnO 2 -based compound amendments on Cd passivation. For clay mineral-based compound materials, i.e., MMT-and AT-based compound materials, the synergistic effects of clay minerals and organic components on Cd passivation may be attributed to the O-H groups and Si-O-Si of the compound amendments, strengthening the precipitation, electrostatic interactions, ion exchange, and surface complexation of Cd in soils [57,58]. The synergistic mechanisms of CM-based compound materials for Cd passivation may be that the abundant carboxyl or hydroxyl functional groups on the surface of organic components of the compound amendments enhanced the CM-induced co-precipitation reaction of Cd, promoted the formation of insoluble metal phosphates, or increased the proportion of organically bound Cd [53].…”