A KrCl exciplex flow-through photoreactor for degrading 4-chlorophenol:Experimental and modelling

Abstract

A KrCl exciplex flow-through photoreactor has been used for the removal of 4- chlorophenol. UV/H2O2 and photo-Fenton processes were tested. Considering the degradation of the different compounds, the molar ratio H2O2:4-chlorophenol did not show a significant influence on 4-chlorophenol while an optimum ratio of 25:1 was established for the photoproducts. The presence of the Fenton reagent led to a considerable improvement in the photodegradation of both the substrate and by- products, and an optimum Fe2+ concentration of 5 mg L-1 was determined. Under these conditions, total degradation was attained for a range of substrate concentrations between 50 and 150 mg L-1 and for reaction volumes of 500 mL. A photodegradation mechanism was also proposed, based on the formation of two intermediate compounds that quickly degrade to the primary photoproducts previously identified. A kinetic model was developed and theoretical conversion values of the 4-chlorophenol and the photoproducts were compared with the experimental ones, reaching a high degree of agreement (xcalc = 0.9964 xexp, R2 = 0.9986) and validating the proposed model. This system simulation using relatively high reaction volumes and including the by-products in the kinetic equations represents a first approach with a view to operating in continuous or semi-continuous systems that allow the scaling up of the process.