Simultaneous removal of phenol and chromium reduction from the aqueous solution with photocatalytic process in the presence of ZnO-activated carbon fibre composite

Simultaneous removal of phenol and chromium Cr(VI) reduction in aqueous solution was evaluated using ZnO-activated carbon fibre (ZnO/ACF) composite in a photoreactor. ZnO/ACF composite was synthesised by the hydrothermal method, and its characteristics were characterised by techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy and Fourier transform infrared analysis. The effect of some operational factors such as pH, composite dosage, initial concentrations and contact time on the removal efficiency was studied through the photocatalytic runs using ZnO/ACF composite. SEM analysis demonstrated that the flowerlike structure of ZnO adhered successfully to the ACF surface. XRD analysis also confirmed patterns for the wurtzite hexagonal phase of ZnO and ACF for ZnO/ACF composite. Results of photocatalytic experiments showed that 20 mg/L of Cr(VI) and 20 mg/L of phenol were completely removed in acidic conditions with 1.5 g/L of ZnO/ACF after 45 and 50 min, respectively. With an increase in the concentration of pollutant from 5 to 20 mg/L, the k(obs) values decreased from 0.0512 to 0.0059 for phenol and decreased from 0.0489 to 0.0057 for chromium, while the electrical energy per order (E-E0) increased from 99.77 to 856.15 kWh/m(3)for phenol and increased from 93.78 to 847.18 kWh/m(3) for chromium. The use of ZnO/ACF composite is considerably improving the performance of the photocatalytic process. Therefore, ZnO/ACF/ultravioletcould be recommended as an effective process to simultaneously removal of phenol and Cr(VI) reduction in toxic wastewater.