Occurrence Of Parabens In Aquatic Environment And The Degradation Mechanism Of The Chemical Pre-oxidation Process

Parabens have been widely used as antimicrobial in many products,and they have been detected in surface water,groundwater,drinking water,sewage effluets,air,dust and soils.And the pollution of aqueous enviroments has posed a threat to the aqueous secrity.In this study,the occurrence of parabes were investigated in several water bodys including lake water,groundwater,rivers and tap water.Moreover,the degradation kinetics and mechanisms of parabens oxidized by sodium hypochlorite and chlorine dioxide were studied.The occurrence of parabens in several kinds of water bodies was investigated.The total amount of parabens in lake water was lower,while the concentration of parabens in groundwater was larger,ranging from 51.59 ng/L to 77.70 ng/L,and the source of these drugs was domestic sewage.The concentration of parabens in rivers ranged from 18.13 to 42.47 ng/L,which was mainly due to the sewage treatment plant.However,parabens were also detected in tap water,which indicated that the removal effect on parabens in water treatment plant was poor,and it is necessary to explore effective methods to remove parabens.The reactivity and fate of parabens during chlorination were investigated in this work.Chlorination kinetics of MeP,EtP,PrP and BuP were studied in the pH range of 4.0 to 11.0 at 25±1 °C.The total reaction orders of 1.614,2.019,1.851 and 1.860 for MeP,EtP,PrP and BuP,respectively,were obtained at pH 7.0.The rate constants depended on the solution pH,temperature,and NH4+ concentration were also studied.The maximum kapp was obtained at pH 8.0,and the minimum value was obtained at pH 11.0.The reaction rate constants increased with increasing temperature.When NH4+ was added to the solution,the reaction of parabens was inhibited due to the rapid formation of chloramines.Two main transformation products,3-chloro-parabens and 3,5-dichloro-parabens,were identified by GC-MS,and a reaction pathway was proposed.Dichlorinated parabens accumulated in solution,which is a threat to human health and the aqueous environment.The reactivity and fate of parabens oxidized by chlorine dioxide were investigated in this work.Degradation kinetics of MeP and PrP were studied in the pH range of 4.0 to 7.0 at 15±1?C.The values of kapp were determined to be 84.3 M-1·s-1 and 83.2 M-1·s-1 for MeP ana PrP,respectively,at pH 5.0 with the concentration of ClO2 at 50 μM.The rate constants depended on the solution pH,temperature,HA and HCO3-concentration were also determined.When the pH values ranged from 4 to 5,the kapp increased slowly,and subsequently the kapp increased rapidly with the p H values increased to 7.The reaction rate constants increased with increasing temperature.The reaction of parabens was inhibited when HA was added to the solution,whlie the reaction rate was increased after adding HCO3-.Two main degradation products were identified by GC-MS,and a reaction pathway was proposed.