Removal of Cr(VI) from acid wastewater by BC/ZnFe₂O₄ magnetic nanocomposite via the synergy of absorption‐photocatalysis

Photocatalysis is a promising solar energy conversion technology due to its potential applications in water treatment, searching for highly efficient photocatalytic materials and structures is highly desirable. Herein, we have prepared a series of biochar(BC)/ZnFe₂O₄ magnetic nanocomposite by the calcination‐hydrothermal two step method. BC/ZnFe₂O₄ owns a broad photoabsorption edge at ~ 630 nm and improved photoabsorption from 800 to 1300 nm . PL spectra of BC/ZnFe₂O₄ shows a weaker intensity compared with BC and ZnFe₂O₄ , and BC/ZnFe₂O₄ generates a stronger photocurrent density (~ 0.08 μA cm⁻² ) than that of BC (0) or ZnFe₂O₄ (0.03 μA cm⁻² ) under the visible light irradiation, implying efficient separation efficiency of photogeneration carriers. The investigation of pH (3, 5, 7, 9, 11) sensitivity of BC/ZnFe₂O₄ demonstrates that removal efficiency of Cr(VI) achieves the highest rate at pH = 3. Under visible light irradiation, BC/ZnFe₂O₄ as photocatalyst can remove 80% Cr(VI), higher than that of BC (0) or ZnFe₂O₄ (44%). In addition, the BC/ZnFe₂O₄ composite exhibits excellent cycling stability and can be easily separated for recycling due to its excellent stability and unique magnetic properties . This work has presented a promising strategy in adsorption‐photocatalytic treatment of acidic wastewater containing Cr(VI). Copyright © 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.