Developing goethite modified reed-straw biochar for remediation of metal(loids) co-contamination.

Arsenic and cadmium contamination, along with their associated environmental risks, is a global concern, and the synergistic stabilization of cations and oxyanions in contaminated environments is challenging. In this study, goethite-modified biochar (BC-Gt) was synthesized and investigated for its remediation potential in co-contamination of cadmium (Cd) and arsenic (As), compared to pristine reed-straw biochar (BC) and goethite (Gt). BC-Gt exhibited the highest maximum adsorption capacities in the binary As and Cd solution (As: 126.02 mg·g−1, Cd: 125.12 mg·g−1). BET-SSA, SEM-EDS, XRD, FTIR and XPS analyses revealed various mechanisms of co-adsorption of As and Cd on BC-Gt, including ion exchange, electrostatic interaction, surface precipitation and complexation. Moreover, the specific adsorption of Cd(II) involved cation-π interaction, while limited oxidation-reduction of As(V) occurred during adsorption. BC-Gt also displayed profound stabilization effects in As, Cd and lead (Pb) co-contaminated soils, with maximum removal efficiencies of 63.98 %, 83.67 % and 83.92 %, respectively. BC-Gt outperformed BC and Gt in transforming the exchangeable fraction (Exc) into reducible (Red), oxidizable (Oxi) and residual (Res) fractions of As, Cd and Pb. This study provides evidence in the potential of BC-Gt for remediating co-contamination of As and Cd in water, as well as As, Cd and Pb in soil. [Display omitted] • Goethite-modified biochar (BC-Gt) adsorbing mixed As(V) and Cd(II) solution was tested. • Ion exchange, electrostatic interaction, and precipitation were the common mechanisms. • Cd(II) involved in cation-π interaction while As(V) had reduction. • BC-Gt effectively immobilized As, Cd and Pb from the co-contaminated soils. • BC-Gt transformed exchangeable into other relatively immobile fractions of As, Cd and Pb. [ABSTRACT FROM AUTHOR]