Enhanced photocatalytic oxidation degradability for real cyanide wastewater by designing photocatalyst GO/TiO2/ZSM-5: Performance and mechanism research

Abstract

Cyanide wastewater contains highly toxic contaminants such as free cyanide and metal-cyanide complex, it is necessary to find the appropriate degradation technologies. In this study, a simple and effective photocatalyst with enhanced adsorption and photocatalytic activity was developed. A new composite photocatalyst was successfully prepared by solid-state dispersion (SSD) method, which combined graphene oxide (GO), nano titanium dioxide (nano-TiO2) and silicon-based zeolite (ZSM-5). The techniques of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), N2 adsorption–desorption test, X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the samples. The experiments with different content of nano-TiO2, different wavelengths of light source, different catalyst dosage, control experiments of different materials, and the determination of pH value and zeta potential were also carried out. The results showed that the 3.0 g/L of GTZ-60 (GO/TiO2/ZSM-5 composite photocatalyst with a content of 60 wt% TiO2) has the highest photocatalytic degradation efficiency under ultraviolet wavelength which the degradation efficiency of total cyanide and copper could reach 98.73% and 98.96%, respectively. The degradation of total cyanide followed the pseudo-first-order kinetics. The photoelectric properties of GTZ-60 obviously improved the migration and separation of photogenerated electrons (e−) and holes (h+), so that high photocatalytic efficiency was obtained. XPS analysis showed that cyanide was finally degraded to carbon oxide and nitrogen oxide. Copper and zinc are removed in the form of copper (Ⅱ) and zinc (Ⅱ).