Removal of Cr(VI) from Acid Wastewater by BC/ZnFe 2 O 4 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)/ZnFe 2 O 4 magnetic nanocomposites by the calcination‐hydrothermal two‐step method. BC/ZnFe 2 O 4 owns improved photoabsorption from 400 to 1300 nm. PL spectra of BC/ZnFe 2 O 4 shows a weaker intensity compared with BC and ZnFe 2 O 4 , and BC/ZnFe 2 O 4 generates a stronger photocurrent density (∼0.08 μA cm −2 ) than that of BC (0) or ZnFe 2 O 4 (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/ZnFe 2 O 4 demonstrates that removal efficiency of Cr(VI) achieves the highest rate at pH=3. Under visible light irradiation, BC/ZnFe 2 O 4 as photocatalyst can remove 80 % Cr(VI), higher than that of BC (0) or ZnFe 2 O 4 (44 %). In addition, BC/ZnFe 2 O 4 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.