Photocatalytic treatment of 4-chlorophenol in aqueous ZnO suspensions: Intermediates, influence of dosage and inorganic anions

The photocatalytically driven removal of eco-persistent 4-chlorophenol from water using ZnO is reported here. Kinetic dependence of transformation rate on operating variables such as initial 4-chlorophenol concentration and photocatalyst doses was investigated. A complete degradation of 4-chlorophen...

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Veröffentlicht in:Journal of hazardous materials 2009-08, Vol.168 (1), p.57-63
Hauptverfasser: Gaya, Umar Ibrahim, Abdullah, Abdul Halim, Zainal, Zulkarnain, Hussein, Mohd Zobir
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Sprache:eng
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Zusammenfassung:The photocatalytically driven removal of eco-persistent 4-chlorophenol from water using ZnO is reported here. Kinetic dependence of transformation rate on operating variables such as initial 4-chlorophenol concentration and photocatalyst doses was investigated. A complete degradation of 4-chlorophenol at 50 mg L −1 levels was realised in 3 h. Analytical profiles on 4-chlorophenol transformation were consistent with the best-line fit of the pseudo zero-order kinetics. The addition of small amounts of inorganic anions as SO 4 2−, HPO 4 −, S 2O 8 2− and Cl − revealed two anion types: active site blockers and rate enhancers. Fortunately, Cl − and SO 4 2− commonly encountered in contaminated waters enhanced the rate of 4-chlorophenol degradation. The reaction intermediates and route to 4-chlorophenol mineralisation were elucidated by combined RP-HPLC and GC–MS methods. In addition to previously reported pathway products of 4-chlorophenol photo-oxidation catechol was detected. A radical mechanism involving o-hydroxylation is proposed to account for the formation of catechol.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2009.01.130