Synthesis and characterisation of activated carbon supported catalysts: photocatalytic degradation of olive wastewater solutions using these catalysts

Abstract

The aim of this study is to synthesize and characterize four different types of activated carbon supported catalysts and evaluate their effectiveness in the photocatalytic degradation of olive mill wastewater (OMW) generated during the olive oil production process. The four photocatalysts synthesized by using the sol-gel method were: TiO2/AC, V2O5/TiO2/AC, WO3/TiO2/AC and V2O5/WO3/TiO2/AC. The photocatalysts were characterised by using TEM, SEM, XRD, FTIR analytical technniques and BET analyses. The degradation performance of these calatalysts was evaluated by investigating the the removal of pollutants such as color, phenol, lignin and COD from OMW. In addition, the effects on photocatalytic degradation were investigated in detail by considering the catalyst type, catalyst amount, suspension pH and contact time. From the experimental results, V2O5/TiO2/AC catalyst showed superior performance compared to the remaining catalysts. In order to increase the oxidation effect, ozone (O3) and hydrogen peroxide (H2O2) were used as supporting oxidising agents either together or separately in some experiments. When ozone and UV were used together, the highest removal rates for color, phenol, lignin and COD were 87%, 91%, 60% and 70%, respectively, and when the catalyst and H2O2 were used together, the highest removal rates were 24%, 55%, 35% and 42%, respectively, for color, phenol, lignin and COD. When the catalyst, UV/O3 and H2O2 were used together, the removal rates for color, phenol, lignin and COD were 95%, 90%, 60% and 58%, respectively, after 6 hours. Under optimum conditions, photocatalytic degradation of various pollutants in the presence of supporting oxidants such as O3 and H2O2 reached almost 80–95%. In conclusion, the findings of this research address a major environmental concern in the treatment of OMW by presenting an innovative catalytic method for the effective degradation of OMW wastewater.