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

• Main Authors: Gaya, Umar Ibrahim, Abdullah, Abdul Halim, Zainal, Zulkarnain, Hussein, Mohd. Zobir
• Format: Article
• Language: English; English
• Published: Elsevier 2009
• Online Access: http://psasir.upm.edu.my/id/eprint/16187/1/Photocatalytic%20treatment%20of%204.pdf; http://psasir.upm.edu.my/id/eprint/16187/

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 SO42−, HPO4−, S2O82− and Cl− revealed two anion types: active site blockers and rate enhancers. Fortunately, Cl− and SO42− 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.