Optimization of operational parameters affecting phenol degradation in a photocatalytic system under visible light irradiation

"Phenol and its water-soluble derivatives are among the most important toxic pollutants. In recent years, the use of MOFs as photocatalysts for wastewater treatment has attracted much attention. Combining a MOF with a semiconductor that can minimize electron-hole recombination can be very effective in photocatalytic reactions."

In this research, TiO2/MIL88 composites with different percentages of titanium dioxide were synthesized using a one-pot hydrothermal method and investigated for phenol removal in a hexagonal photoreactor. The unique hexagonal design of the reactor increases the surface area available for radiation, resulting in more effective removal of contaminant. In order to achieve the highest degradation efficiency, the variables: amount of photocatalyst, reaction time, phenol concentration, pH, and H2O2 concentration (ml/L) were selected as effective parameters on the photocatalytic degradation process. In order to design the experiments, Design Expert software was used, and among the RSM methods, Box Behnken method was selected.

Catalyst characterization analyzes showed that TMA10 composite was correctly synthesized. Using this composite, the optimal conditions for the maximum efficiency of phenol degradation (95.96%) are as follows: initial concentration of phenol 58 mg/L, pH equal to 7.51, reaction time 68.61 minutes, H2O2 concentration equal to 0.18 mL/L, and the amount of catalyst equal to 0.4 g/L was obtained.

The results of photocatalytic experiments showed that TMA10 composite (10 molar ratio TiO2:MOF) has a better performance than other composites in phenol degradation. Photoluminescence (PL) analysis showed that the better performance of TMA10 composite is due to the reduction of electron-hole recombination in it. Also, analysis of variance showed that the quadratic model fits well with the data.