Influence of substituent type and position on photooxidation of phenolic compounds: Response surface methodology approach

The combined influence of process (pH and [H2O2]) and structural (substituent type and position) parameters influencing the degradation of phenolic pollutants in water by UV/H2O2 processes is studied using modified miscellaneous 34 full factorial design and response surface methodology (RSM). The model wastewaters consisted of eight phenolic pollutants containing hydroxyl (–OH), chloro (–Cl), nitro (–NO2), and methyl (–CH3) substituents in ortho and para position. It was determined that all studied phenols obey first-order degradation kinetic, which is influenced significantly by all studied process and structural parameters. The quadratic polynomial model is used to describe these effects. Different optimal operating conditions and values of observed first-order degradation rate constants (kobs) were determined for each of the phenolic pollutants indicating the significant influence of type and position of substituent to parent pollutant degradation and structurally determined degradation pathway. kobs were correlated with the second-order degradation rates with hydroxyl radicals (kHOkHO) as well as with several physical and structure related properties of studied phenolics using Spearman rank coefficient.

► We study the degradation of eight phenolic compounds by UV/H2O2 process. ► We investigate the combined influence of process and structural parameters using RSM. ► The type and position of substituent significantly influence the degradation kinetic. ► We observe clear correlation of kHOkHO with structure-related and physical properties.