An optimization andmodeling approach for H₂O₂/UV-C oxidation of a commercial non-ionic textile surfactant using central composite design

BACKGROUND: Industrial surfactants are biologically complex organics that are difficult to degrade and may cause ecotoxicological risks in the environment. Until now, many scientific reports have been devoted to the effective treatment of surfactants employing advanced oxidation processes, but there is no available experimental study dealing with the optimization and statistical design of surfactant oxidation with the well-established H ₂O₂/UV-C process. RESULTS: Considering the major factors influencing H₂O₂/UV-C performance as well as their interactions, the reaction conditions required for the complete oxidation of a commercial non-ionic textile surfactant, an alkyl ethoxylate, were modeled and optimized using central composite design-response surface methodology (CCD-RSM). Experimental results revealed that for an aqueous non-ionic surfactant solution at an initial chemical oxygen demand (COD) of 450 mg L^-1, the most appropriate H₂O₂/UV-C treatment conditions to achieve full mineralization at an initial pH of 10.5 were 47mmol L^-1 H ₂O₂ and a reaction time of 86 min (corresponding to a UV dose of 30 kWh m^-3). CONCLUSION: CCD allowed the development of empirical polynomial equations (quadratic models) that successfully predicted COD and TOC removal efficiencies under all experimental conditions employed in the present work. The process variable treatment time, followed by the initial COD content of the aqueous surfactant solution were found to be the main parameters affecting treatment performance, whereas the initial H ₂O₂ concentration had the least influence on advanced oxidation efficiencies. The H₂O₂ concentration and surfactant COD were found to be more important for TOC abatement compared with COD abatement.