Solar heterogeneous photocatalytic degradation of phenol on TiO 2 /quartz and TiO 2 /calcite: a statistical and kinetic approach on comparative efficiencies towards a TiO 2 /glass system.

Phenol is a widely used synthetic organic compound, which according to global estimations, is discharged into the environment at a rate of 10 tons/year through industrial waste. Phenol is a recalcitrant pollutant, and human exposure to water containing phenolic substances can lead to health issues. It has been found both in drinking water and wastewater. Solar heterogeneous photocatalytic phenol degradation, measured through chemical oxygen demand, was performed on a thin film tilted plate reactor with TiO 2 immobilized onto different support materials. A full factorial experimental design (4 × 3 × 3) was carried out to statistically evaluate if the independent variables' effects were significant. Four advanced oxidation processes (photolysis, photolysis + H 2 O 2 , heterogeneous photocatalysis, and heterogeneous photocatalysis + H 2 O 2 ), three support materials (quartz, calcite, and glass), and three pH levels (3, 5.4, and 9) were evaluated. Reaction kinetics were fitted to the pseudo-first-order reaction rate and data was analyzed with an ANCOVA and means test, considering solar light intensity as a covariate. Photolysis/calcite at pH 5.4 and heterogeneous photocatalysis + H 2 O 2 /glass plate at pH 3 gave the best results, with a reaction rate constant k ph  = 3.047 × 10 -3  min -1 and k phC  = 4.498 × 10 -3  min -1 , respectively. The three independent variables and their interactions had a significant effect in the phenol degradation (p < 0.05).