Rate parameter estimation for 4-chlorophenol degradation by UV and organic oxidants

The main objective of this study was to evaluate the rate parameters of degradation/mineralization of 4-chlorophenol (4-CP) using organic oxidants, viz., peroxy acetic acid (PAA), para nitro benzoic acid (PNBA), and methyl ethyl ketone peroxide (MEKP), in basic media, in combination with UV irradiation at 254 nm. All the experiments were conducted with varying time intervals, under identical conditions of UV irradiation and pH. The reactions were followed by HPLC analysis for residual concentration and GC–MS for mineralization, and intermediates/product identification. In the present investigation, the residual concentration data of 4-CP against time were analyzed for reaction order determination by differential and integral methods. The differential method yielded fractional order of reaction for all organic oxidants under consideration. Initially the profile was observed to be linear in the time span of 0–45 s for all the organic oxidants used and thus, first-order approximation was applied. The curvilinear path, which followed up till 300 s, was approximated to first-order and second-order kinetics. No noteworthy results were observed for pseudo-first order rate equation. The change in the nature of the curves was attributed to the formation of intermediates/reaction products.