Enhanced photocatalytic performance of iron oxides@HTCC fabricated from zinc extraction tailings for methylene blue degradation: Investigation of the photocatalytic mechanism

Photocatalytic processes are efficient methods to solve water contamination problems, especially considering dyeing wastewater disposal. However, high-efficiency photocatalysts are usually very expensive and have the risk of heavy metal pollution. Recently, an iron oxides@hydrothermal carbonation carbon (HTCC) heterogeneous catalyst was prepared by our group through co-hydrothermal treatment of carbohydrates and zinc extraction tailings of converter dust. Herein, the catalytic performance of the iron oxides@HTCC was verified by a nonbiodegradable dye, methylene blue (MB), and the catalytic mechanism was deduced from theoretical simulations and spectroscopic measurements. The iron oxides@HTCC showed an excellent synergy between photocatalysis and Fenton-like reactions. Under visible-light illumination, the iron oxides@HTCC could be excited to generate electrons and holes, reacting with H2O2 to produce center dot OH radicals to oxidize and decompose organic pollutants. The removal efficiency of methylene blue over iron oxides@HTCC at 140 min was 2.86 times that of HTCC. The enhanced catalytic performance was attributed to the advantages of iron oxides modification: (1) promoting the excitation induced by photons; (2) improving the charge transfer. Furthermore, the iron oxides@HTCC showed high catalytic activity in a wide pH value range of 2.3-10.4, and the MB removal efficiency remained higher than 95% after the iron oxides@HTCC was recycled 4 times. The magnetically recyclable iron oxides@HTCC may provide a solution for the treatment of wastewater from the textile industry.