Journal
JOURNAL OF ENVIRONMENTAL MANAGEMENT
Volume 141, Issue -, Pages 61-69Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2014.03.020
Keywords
Pharmaceutical; Chloride; Mineralization; UV; Ultrasound
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Funding
- JCCM (gs1) [POII10-0114-3563]
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The mineralization of pharmaceutical wastewater containing chloride ions using a UV/H2O2/Fe(II) process was studied. The addition of Fe(II) to the UV/H2O2 system did not improve the degradation efficiency due to inhibition of the photo-Fenton reaction, at acid pH, in the presence of chloride ions in these wastewaters. The increase of pH from 2 to 7 increased the degree of mineralization under UV photolysis of H2O2 because more HO center dot radicals are available by HOCl center dot dissociation reaction. Under the selected operation conditions ([H2O2](o) = 11,500 ppm, [Fe(II)] = 0 ppm, [TOC](o) = 125 ppm and pH = 7), 100% of TOC removal was attained in 120 min. A significant synergistic effect of combining photolysis (UV/H2O2) and sonolysis was observed. Sonophotolysis (UV/H2O2/ultrasound) technique significantly increased the degree of mineralization (100% TOC removal in 90 min using 6500 ppm H2O2) when compared with each individual process. Sonochemical reaction was favored by the presence of chloride ions since the concentration of contaminants at the gas liquid interface increased. Free radicals reaction was the controlling mechanism in the UV/H2O2/ultrasound system. HO center dot radicals were the main oxidative intermediate species in the process, although hydroperoxyl radicals (HO2 center dot) also played a role. The contribution of thermal-pyrolytic reaction (in gas-phase) to sonophotolysis process was negligible. (C) 2014 Elsevier Ltd. All rights reserved.
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