Degradation Efficiency And Mechanisms Of Selected Pharmaceuticals By Potassium Permanganate

With rapid increase of drugs demand and drugs abuse,the residual drugs in the environment becomes serious pollution problem.Several typical drugs,such as anticancer drugs 5-fluorouracil(5-FU)and cytarabine(Ara-C),sulfa drugs sulfathiazole(STZ)and glucocorticoid drugs prednisolone(PRED)were selected as target compounds in this survey.The degradation kinetics,the effect of different factors and degradation mechanisms of the reaction between the potassium permanganate and those selected drugs were studied in this paper.Firstly,the degradation efficiency and mechanisms of anticancer drugs 5-FU and Ara-C with potassium permanganate were determined.In this experiment,the reaction of 5-FU and potassium permanganate contained multiple elementary reactions and the total reaction order was 1.63.The kinetic model can be described as-d[5-FU]/dt = kapp[5-FU]t0.77[KMn O4]t0.86.Whlie the degradation kinetics of Ara-C followed a generalized second-order rate law,and the reaction rate constant was 1.17 M-1·s-1(p H=4.0±0.1,25?).The temperature,p H and water quality had great influence on both reactions.Trace 5-FU and Ara-C could not be completely removed by trace potassium permanganate(35 ?M).Intermediate products of 5-FU and Ara-C were analyzed by gas chromatography and mass spectrometry(GC-MS)and the possible degradation pathways were also proposed.Secondly,the sulfa drugs STZ degradation efficiency and mechanism with potassium permanganate were also investigated in this paper.The degradation kinetics of STZ followed generalized second-order rate law,and the reaction rate constant was 5.55 M-1·s-1(p H=7.0±0.1,25?).The effects of temperature,p H,water quality and other factors on the degradation of STZ were investigated.With the increase of p H(in the range of 5-10),the reaction rate constant increased and finally reached maximum at p H of 8.0.Low removal rate between the trace STZ and trace potassium permanganate(20 ?M)reaction system was proved.GC-MS and liquid chromatography and time of flight mass spectrometry(LC-TOF)were used to detect intermediate products of STZ and a possible degradation mechanism was inferred.Finally,the glucocorticoids PRED degradation efficiency and mechanism with potassium permanganate were studied.The reaction of PRED and potassium permanganate also followed generalized second-order rate law,with the reaction rate constant of 4.17 M-1·s-1(p H=7.0±0.1,25?).The degradation rate of PRED was promoted when temperature raised.While the p H,NH4+,HCO3-and humic acid had fewer effect on the reaction.The intermediate products of PRED were determined by GC-MS and LC-TOF,a suggestive degradation pathway was also proposed in this paper.