Assessment of the UV/Chlorine process as an advanced oxidation process

Several organic compounds were used as radical scavengers/reagents to investigate the possibility of the UV/chlorine process being used as an advanced oxidation process (AOP) in the treatment of drinking water and wastewater. The UV/H2O2 process was selected as a reference, so that the results from the UV/chlorine process could be compared with those of the UV/H2O2 process. Methanol was added to active chlorine solutions at both pH 5 and 10 and into hydrogen peroxide samples. The photodegradation quantum yields and the OH radical production yield factors, which are significant in evaluating AOPs, were calculated for both the UV/chlorine and the UV/H2O2 processes. The yield factor for the UV/chlorine process at pH 5 was 0.46 ± 0.09, which is much lower than that of the UV/H2O2 process, which reached 0.85 ± 0.04. In addition to methanol, para-chlorobenzoic acid (pCBA) and cyclohexanoic acid (CHA) were added to active chlorine solutions and to H2O2 solutions, to evaluate the efficiencies of oxidizing these organic compounds. The specific first-order reaction rate constants for the oxidation of pCBA and CHA, using the UV/chlorine process, were lower than those found using the UV/H2O2 process.