Hierarchical effect of surface oxidation on Cd2+ adsorption was confirmed.
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Relationship between surface oxidation degree and biochar yield was demonstrated.
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Over-oxidation would result in a low-down biochar yield.
Abstract
Quantitative effects of surface oxidation on Cd2+ adsorption performance of biochar derived from long-root Eichhornia Crassipes plants were systematically investigated. It was revealed that oxidation degree was positively related with the intensity of surface functional groups and harmless for the structural stability, while biochar yield would decline sharply resulting from for over-oxidization. Correspondingly, the Cd2+ adsorption capacity exhibited an uptrend with the increasing oxidation on account of the abundant adsorption sites. Moreover, Cd2+ adsorption on the biochar with different oxidation degrees were also investigated comprehensively, indicating adsorption performances in a similar trend highly sensitive to solution pH and ionic strength. In addition, the adsorption isotherms were found to manifest the saturated adsorption capacity for Cd2+ increased from 0.333 mol/g to 0.487 mmol/g at 30 °C by strengthening oxidation. All synthesized biochar could keep consistent adsorption performance in multiple adsorption-desorption cycles.
