Different photodegradation behavior of 4-tert-octylphenol under UV and VUV irradiation in aqueous solution

Abstract

Abstract Comparative study on 4- tert -octylphenol degradation under UV (253.7 nm) and VUV (combined 253.7 nm and 184.9 nm) radiation in aqueous solution was performed in laboratory scale in this paper. Excitation light played the key role on 4- tert -octylphenol photodegradation. 93.5% 4- tert -Octylphenol was decomposed after 20-min VUV radiation while only 49.5% degradation efficiency was achieved after 4- tert -octylphenol received UV radiation for the same irradiation time. Other factors influencing 4- tert -octylphenol degradation efficiency included solution pH, initial concentration and natural water constituents. Initial 4- tert -octylphenol concentration and pH exhibited different influence pattern on 4- tert -octylphenol degradation under UV and VUV radiation. 4- tert -Octylphenol photodegradation products were discerned by HPLC and GC–MS. 4- tert -octylcatechol was recognized as predominant photoproducts under both UV and VUV radiation. Trace amount of phenol was also detected when 4- tert -octylphenol was subjected to VUV radiation. Degradation of 4- tert -octylphenol upon UV radiation was, therefore, predicted to be initiated by the photoejection of an electron from excited 4- tert -octylphenol, whereas 4- tert -octylphenol photolysis upon VUV radiation may also involve the direct C C bond cleavage from excited 4- tert -octylphenol. No matter the excitation light wavelength, photopolymization process was found to occur at high initial 4- tert -octylphenol concentration. Special attention should be paid to the photopolymerization phenomena during practical application of 4- tert -octylphenol photodegradation.