Synthesis and characterization of ZnO@RSDBC composites and their Photo-Oxidative degradation of Acid Orange 7 in water

In this study, a novel series of rectorite/sludge derived biochar (RSDBC) supporting ZnO (ZnO@RSDBC) composites were fabricated and characterized by scanning electron microscope, transmission electron microscope, fourier transform infrared spectroscopy, nitrogen gas uptake, UV–Vis absorption spectroscopy and X-ray diffraction techniques. From the SEM and TEM results, ZnO particles were well loaded on RSDBC, forming a core-shell ZnO@RSDBC structure. The observed strong XRD and FTIR characteristic peaks indicated that the ZnO@RSDBC was successfully synthesized. The calculated band gap energy was 3.25 eV which the result was in agreement with the theoretical band gap value of ZnO. After characterization, the photocatalytic performances of ZnO@RSDBC catalyst were evaluated by the heterogeneous Photo-Oxidative process (ZnO@RSDBC/PS/Vis) for the elimination of Acid Orange 7 (AO7). Key factors affecting the reaction were tested, including initial pH, PS concentration, catalyst dosage, initial dye concentration, and reaction temperature. The optimal conditions were found to be: PS concentration 2 mM; catalyst dosage 0.9 g/L; initial pH value 7.0 and 30 °C of reaction temperature. Further radical quenching tests of different scavengers showed that h+、SO4•− and HO• are responsible in the process of AO7 decolorization. In addition, the sample exhibited high color removal ability (95%) and stable performance after three successive runs. The catalyst also presented excellent removal effect for Methyl orange, Rhodamine B and Methylene blue. These results indicate that ZnO@RSDBC is an efficient Photo-Oxidative catalyst for remediation of dyes.