Comparison of UV and UV/H2O2 treatments using excilamps for removal of monochlorophenols in the molecular and anionic form.

Analytical Center, Baikal Institute of Nature Management, Siberian Branch of Russian Academy of Sciences, Ulan-Ude, Russia.
Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 11/2012; 47(13):2077-83. DOI: 10.1080/10934529.2012.695953
Source: PubMed

ABSTRACT The efficiency of UV/H(2)O(2) treatment using KrCl (222 nm) and XeBr (282 nm) excilamps was examined for removal of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) from aqueous solution in the molecular form (pH 2 and un-adjusted pH) and anionic form (at pH 11). UV/H(2)O(2) treatment of 2- or 4-CP was initially carried out at un-adjusted pH with varying molar ratios of chlorophenol and H(2)O(2). The para-chlorobenzoic acid was used as a hydroxyl radical (•OH) probe compound. UV/H(2)O(2) treatment of 2- and 4-CP with a molar ratio of 1:25 at ambient pH and a fluence of 4.1 J/cm(2) provided a significant decrease in chemical oxygen demand (COD). Under these conditions, the •OH exposure was found to increase from 0.5 × 10(-11) and 0.4 × 10(-11) to 1.8 × 10(-11) and 1.3 × 10(-11) M min for KrCl and XeBr excilamp, respectively. Compared with direct UV photolysis, the pseudo-first-order fluence-based rate constants of 2- and 4-CP degradation in UV/H(2)O(2) process at a molar ratio of 1:25 were significantly higher for molecular 2-CP and 4-CP in the anionic form using both excilamps. Detailed information on UV fluence and/or the exposure to •OH radicals is proposed to accurately compare studies reporting the effectiveness of AOPs based on excilamps.

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    ABSTRACT: Excilamps as modern mercury-free sources of narrow-band UV radiation represent an attractive alternative in environmental applications. This review focuses on recent studies on the water and surface decontamination with excilamps by means of direct photolysis and advanced oxidation processes. To date, direct photolysis and advanced oxidation processes (AOPs) such as UV/H(2)O(2), UV/Fenton and UV/O(3) have been applied for degradation of organic compounds (mainly, phenols, dyes and herbicides) in model aqueous solutions. Special emphasis is placed on studies combining UV irradiation (as a pre-treatment or post-treatment step) with biological treatment. In this review, the efficiencies of direct UV, UV/H(2)O(2) and UV/TiO(2) processes for inactivation of a variety of pathogenic microorganisms in water and on surfaces are discussed. The analysis of the literature shows that more works need to be done on scaling up the processes, degradation/mineralization of target pollutant(s) in real effluents and evaluation of energy requirements.
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