Removal of Cd from aqueous solution by chitosan coated MgO-biochar and its in-situ remediation of Cd-contaminated soil.

In this study, magnesium oxide biochar-chitosan composite (MgO-BCR-W) prepared through modification with MgCl2 and chitosan was investigated as an adsorbent for the removal of Cd from the aquatic and soil environment. Kinetic and thermodynamics revealed that the Cd(II) adsorption onto MgO-BCR-W was well fitted by pseudo-second-order and the Langmuir adsorption isotherm. The adsorption capacities of rice husk biochar (BCR) and MgO-BCR-W for Cd(II) reached 11.09 mg/g and 59.66 mg/g, respectively. Attractively, the computed values of RL ranged between 0 and 1, suggesting that the adsorption of Cd(II) onto MgO-BCR-W is favourable. Characterisations of the adsorbents revealed that the synergistic effect of surface complexation and precipitation mechanisms played a major role in the removal of Cd. In soil incubation experiment, the addition of MgO-BCR-W at the level of 2% was most effective in Cd stabilization compared to the control, which reduced the content of bioavailable Cd by 22.32%. Furthermore, it reduced the acid extractable Cd by 24.77%, while increased the residual Cd content by 22.24%. The results demonstrated that MgO-BCR-W could be used as an effective and eco-friendly adsorbent for Cd remediation in both water and soil environment.

Enhanced adsorption of Cd(II) from aqueous solution by a magnesium oxide-rice husk biochar composite.

In this study, a magnesium oxide-rice husk biochar composite (MgO-BCR) was successfully prepared by a MgO impregnation method, and its adsorption performance was investigated in Cd(II) aqueous solution. A pseudo-second-order kinetic model described the Cd(II) adsorption behaviour on BCR and MgO-BCR well, while a Langmuir adsorption isotherm was more suitable for Cd(II) adsorption on the adsorbent. The fitting results of the monolayer model indicated that the number of ions captured by per site varied between 0.97 and 1.09. The calculated thermodynamic parameters indicated that Cd(II) adsorption onto MgO-BCR was spontaneous and endothermic. Characterisation of the adsorbent revealed that in situ precipitation, surface complexation, and electrostatic attraction contributed to the Cd(II) adsorption. The adsorption capacities of rice husk biochar (BCR) and MgO-BCR for Cd(II) reached 6.36 and 18.1 mg/g, respectively. The results demonstrated that MgO-BCR composite could be used as an effective and eco-friendly adsorbent to enhance the removal of Cd(II) from aqueous solution.

Removal of both cationic and anionic contaminants by amphoteric starch.

A novel amphoteric starch incorporating quaternary ammonium and phosphate groups was applied to investigate the efficiency and mechanism of cationic and anionic contaminant treatment. Its flocculation abilities for kaolin suspension and copper-containing wastewater were evaluated by turbidity reduction and copper removal efficiency, respectively. And the kinetics of formation, breakage and subsequent re-formation of aggregates were monitored using a Photometric Dispersion Analyzer (PDA) and characterized by flocculation index (FI). The results showed that amphoteric starch possessed the advantages of being lower-dosages-consuming and being stronger in shear resistance than cationic starch, and exhibited a good flocculation efficiency over a wide pH range from 3.0 to 11.0.