Photo-Fenton effect of 4-chlorophenol in ice

The photoconversion of 4-chlorophenol (4-CP) in a simulated sunlight-Fenton system was investigated in ice and aqueous solution. It was found that the hydroxyl radical (OH) had an important effect on the photoconversion of 4-CP in both phases, but the effects of Cl−, SO42−, NO3−, and HCO3− were different. In aqueous solution, the photoconversion efficiency of 4-CP was proportional to the OH concentration, and hence, Cl− and HCO3− as OH scavengers prohibited the photoconversion; SO42− had little effect; NO3− promoted the process under certain conditions owing to OH being generated by the photolysis of NO3−. In ice, however, the photoconversion efficiency of 4-CP was not proportional to the concentration of OH. The photoconversion efficiency of 4-CP increased with increasing concentrations of all ions, although the OH remained almost constant, only increasing or decreasing slightly. This provides new evidence for the presence of a quasi-liquid layer (QLL). Hydroxylation products were detected in both phases. All photoproducts in aqueous solution contained only a single benzene ring, whereas in ice, dimers were also detected.