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 is highly desirable. Herein, we have prepared a series of biochar(BC)/ZnFe2O4 magnetic nanocomposites by the calcination‐hydrothermal two‐step method. BC/ZnFe2O4 owns improved photoabsorption from 400 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, BC/ZnFe2O4 composites exhibit excellent cycling stability and can be easily separated for recycling due to its stability and unique magnetic properties. This work has presented a promising strategy in adsorption‐photocatalytic treatment of acidic wastewater containing heavy metals. Photocatalysis: BC/ZnFe2O4 magnetic nanocomposite was prepared by the calcination‐hydrothermal two‐step method, and it owns an improved photoabsorption from 400 to 1300 nm. BC/ZnFe2O4 exhibits high separation efficiency of photoelectron hole pairs and excellent photocatalytic activity for reducing Cr(VI).