Research On Oxidation Of Sulfamethoxazole In Aqueous Solution By Peroxymonosulfate Activated With Ferrous/Hydroxylamine

Sulfamethoxazole (SMX) is a kind of broad spectrum antibiotics, the detection frequency is very high in surface water. Once it is released to the natural water environment, it will be difficult to be degraded by microorganism and easy to be enriched in vivo. So, the harmful effect antibiotics on natural environment and human health can not be ignored. However, it is difficult to thoroughly remove SMX from aquatic environment via the traditional wastewater treatment process. Therefore, it is necessary to develop an effective technology for SMX treatment and then improve the removal rate of sulfonamide antibiotics.Radical (SO4-?·OH)-based advanced oxidation processes,extremely has the potential of development and application in the field of water treatment. In this paper, peroxymonosulfate(PMS) activated by ferrous and hydroxylamine hydrochloride (NH2OH) (Fe2+/NH2OH/PMS)system was chosen to investigate degradation efficiency, influencing factors and degradation mechanism of SMX. Furthermore, the degradation efficiency of SMX in real water was explored in Fe2+/NH2OH/PMS system.The research results showed that the degradation efficiencies of SMX could reach 73.4%in Fe2+/NH2OH/PMS system. Compared with Fe2+/PMS system, degradation efficiency of SMX was increased by 54.5% in Fe2+/NH2OH/PMS system. The degradation of SMX was fitted with the pseudo-second-order kinetic model. The results of influence factors indicated that SMX degradation efficiency first increased and then decreased with the increase of persulfate dose; the degradation of SMX was improved with the increase of Fe2+concentration(0?M?15?M) and inhibited with further increase of Fe2+ to 20?M; SMX degradation efficiency increased with increasing of NH2OH concentration from OmM to 0.4mM, but 1.0mM of NH2OH resulted in a decrease in SMX removal; SMX removal rate decreased with the increase of SMX dose; elevating temperature in the system promoted PMS activation and improved the oxidation efficiency of SMX; SMX degradation efficiency was raised then decreased with increasing initial pH (2.0?9.0), the maximum removal rate of 73.4% was obtained at pH=3.0. In addition,the co-existing substrates (SO42-?Cl-?HCO3- and humic acid)promoted the degradation of SMX, but the effects of substrates were not obvious.The research of degradation mechanism of SMX indicated that both sulfate radicals(SO4-) and hydroxyl radicals (-OH) could be the primary reactive species and the quantities of ·OH by SMX consumption was 0.472?M in Fe2+/NH2OH/PMS process. Six degradation intermediates were detected in Fe2+/NH2OH/PMS process. Based on the generation path of degradation intermediates, oxidation of the amine group at the benzene ring to derive the nitrate SMX?hydroxylation of the benzene ring?cleavage of the .sulfonamide bond were proposed as the major degradation mechanism of SMX in the system.Based on the oxidation of Fe2+/NH2OH/PMS, for the pharmaceutical industry wastewater and the Wenchang sewage effluent, the removal rate of SMX was 70.8% and 86.2%,respectively; the removal of TOC was 50.2% and 47.1%, respectively; and the removal of UV254 was 38.2% and 33.1%, respectively.The research would provide an important reference for the advanced treatment of SMX via Fe2+/NH2OH/PMS system.