A comprehensive dynamic kinetic model for the UVC/H2O2 process: application to zinc bacitracin degradation in wastewater as a case study

A dynamic kinetic model is presented for the UVC/H2O2-driven process. The model comprises 103 reactions, including background species, such as HCO3-/CO32-, NO2-, NO3-, SO42-, Cl-, and H2PO4-/HPO42/PO43- anions, and effluent organic matter (EfOM) was validated based on experimental data obtained for the photooxidation of the nonribosomal peptide antibiotic zinc bacitracin (Zn-Bc, 34 mu mol L-1). The set of ordinary differential equations for 38 species was combined with the molar balances describing the recirculating tubular photoreactor used. Predictions for the photolytic and UVC/H2O2 processes confirmed the good agreement with experimental data, enabling the estimation of fundamental kinetic parameters, such as the direct photolysis quantum yield (CYRILLIC CAPITAL LETTER EF254 nm, Zn-Bc = 0.0143 mol Einstein(-1)) and the second-order rate constants for the reactions of Zn-Bc with HO center dot, HO2 center dot, and O-2(center dot-) radicals (2.64 x 10(9), 1.63 x 10(3), and 1.49 x 10(4) L mol(-1) s(-1), respectively). The predicted optimum process conditions correspond to [H2O2](0) = 6.8 mmol L-1 and a specific photon emission rate of 11.1 x 10(-6) Einstein L-1 s(-1). Zn-Bc photooxidation was significantly impacted by wastewater constituents, particularly EfOM and HCO3-/CO32- (i.e., alkalinity), resulting in a degradation rate about 32% lower compared to that obtained in deionized water. In particular, EfOM acts as a strong radical scavenger and inner filter. In addition, simulations pointed out the continuous tubular photochemical reactor as the best configuration for treating Zn-Bc-containing wastewater. This study hence provides a comprehensive modeling approach, especially useful for predicting the effect of complex water matrices on the performance of the UVC/H2O2 treatment process.