Fabrication of ferrihydrite-loaded magnetic sugar cane bagasse charcoal adsorbent for the adsorptive removal of selenite from aqueous solution

[Display omitted] •Ferrihydrite-loaded magnetic sugar cane bagasse charcoal adsorbent (FH@Fe3O4@SCBC) was synthesized.•FH@Fe3O4@SCBC realized enhanced adsorptive separation performance for Se(IV).•FH@Fe3O4@SCBC achieved maximum theoretical adsorption capacity for Se(IV) of 95.15 mg g−1.•Se(IV) adsorption efficiency of FH@Fe3O4@SCBC decreased by 1% after five recycled uses, 11.5 % after ten recycled uses.•The removal mechanism of Se(IV) by FH@Fe3O4@SCBC was investigated. Herein we report the fabrication of ferrihydrite-loaded magnetic sugar cane bagasse charcoal adsorbent (FH@Fe3O4@SCBC) by in-situ growth method, which was in turn applied for the adsorptive removal of Se(IV) from aqueous solution. The prepared adsorbents were characterized by SEM-EDS, BET, XRD, VSM, FT-IR, and XPS analyses, and the effect of reaction temperature and pH on Se(IV) removal rate was investigated. Experimental results revealed that the maximum concentration of released Fe ions (0.20 mg L−1) was lower than the WHO highest authorized standard value for Fe in drinking water (0.30 mg L−1) indicating that FH@Fe3O4@SCBC adsorbent has good stability. Experimental results of adsorption kinetics and isotherms revealed that adsorption of Se(IV) by FH@Fe3O4@SCBC mainly occurred via chemisorption and monolayer adsorption and the maximum theoretical adsorption capacity Se(IV) was 95.15 mg g−1. The experiment on the coexisting anions showed that SO42− and PO43− exhibited a significant effect on the adsorption process of Se(IV) while Cl− and NO3− exhibited an insignificant effect. A proposed adsorption mechanism showed that Se(IV) removal included FH@Fe3O4@SCBC inner-sphere complexation, electrostatic interaction, and reduction reaction. According to VSM analysis, FH@Fe3O4@SCBC showed enhanced magnetic response thus facilitating its efficient and facile magnetic separation. Furthermore, FH@Fe3O4@SCBC realized minimal loss in adsorption activity (decreased by 11.5 %) after 10 consecutive reuses. This study provides a facile and cost-effective approach for the fabrication of highly stable FH@Fe3O4@SCBC adsorbent with high adsorption capacity, fast magnetic separation, and excellent recycling advantages making it a promising material for the remediation of Se(IV) from wastewater.