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-chlorophenol at 50 mg L(-1) levels was realised in 3h. 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(2)O(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.
Gaya
Umar Ibrahim
UI
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, UPM Serdang, Selangor DE, Malaysia.
Abdullah
Abdul Halim
AH
Zainal
Zulkarnain
Z
Hussein
Mohd Zobir
MZ
D000838:Anions; D002396:Catechols; D002733:Chlorophenols / Q000737:chemistry / Q000528:radiation effects*; D007700:Kinetics; D010782:Photolysis; D013535:Suspensions; D014873:Water Pollutants / Q000528:radiation effects*; D018508:Water Purification / Q000379:methods; D015034:Zinc Oxide / Q000737:chemistry*
D000838:Anions; D002396:Catechols; D002733:Chlorophenols; D013535:Suspensions; D014873:Water Pollutants; C029107:4-chlorophenol; C034221:catechol; D015034:Zinc Oxide