One-step preparation of lignin-based magnetic biochar as bifunctional material for the efficient removal of Cr(VI) and Congo red: Performance and practical application

[Display omitted] •The LMB was successfully prepared via one-step hydrothermal carbonization method.•The LMB + PS system demonstrated 94.3 % of CR (100 mg/L) removal efficiency at 60 min.•LMB exhibited 100% Cr(VI) and 82% CR removal efficiencies in simulated wastewater.•LMB can be applied to remove Cr(VI) and CR from different contaminated water bodies. The lignin-based magnetic biochar (LMB) was fabricated with a facile one-step solvothermal method. The spherical Fe3O4 was successfully loaded on the lignin-based biochar. LMB could efficiently remove Cr(VI) and Congo red (CR) synergistically with the adsorption of biochar and the catalytic/reduction of Fe3O4. LMB showed a removal efficiency of 100 % for Cr(VI) (100 mg/L) at 30 min. The LMB could be a catalyst to activate persulfate (PS) to degrade CR. The LMB + PS system showed a removal efficiency of 94.3 % for CR at 60 min. Moreover, LMB could simultaneously remove 41.5 % of Cr(VI) and 91.5 % of CR in the mixed Cr(VI) and CR solution. The simulated wastewater studies showed that LMB exhibited superior high Cr(VI) (100 %) and CR (82 %) removal efficiencies with the coexistent of anions, cations, and organic matter. LMB can be effectively applied to remove Cr(VI) and CR and purify different contaminated water bodies.