Research On The Emission And Reduction Technology Of Methyl Siloxane In The Environment Of Typical Industrial

This article mainly focuses on the environmental behavior of methyl,phenyl,and brominated siloxanes in typical oilfields,and mainly consists of the following 4chapters:Chapter 1 The main chain of siloxane is composed of alternating silicon oxygen[Si-O] units.Two side chain organic groups are connected to the silicon atom.The side chain organic groups can be methyl,phenyl,vinyl,or trifluoride,propyl and so on.Introduces the physicochemical properties and applications of siloxane and its conversion products,and then reviews the recent research progress on its toxicity/bioaccumulation effects,environmental distribution,and migration and transformation behavior.Chapter 2 At present,the pretreatment and instrumental analysis methods of modified siloxane are still immature,and there are only a few reports in the literature.Perfected and optimized the pretreatment methods of phenylsiloxane and brominated siloxane in different media(water samples,oil samples,sludge,sediments and biological samples),and established GC-MS detection method of phenylsiloxane and brominated siloxane.Chapter 3 After the introduction of phenyl groups in methylsiloxane,the surface tension and hydrophobicity of polyphenylmethylsiloxane are better than those of polymethylsiloxane,so polyphenylmethylsiloxane may be used as a defoamer in the oil recovery process,and the small molecule phenylsiloxane(P3,P4,etc.)may appear as an impurity in the oil recovery process and then be released into the surrounding environment of the oil field.Studies the environmental distribution characteristics of methyl and phenylsiloxanes in Shengli Oilfield.Six phenylsiloxane isomers(cis-P3,trans-P3,cis-P4,trans-P4 a,trans-P4 b,trans-P4c)and cyclic methyl siloxane(D4,D5,D6)were detected in sludge samples from oilfield wastewater treatment stations,the total concentration of cyclic methylsiloxane(∑CMS,D4-D6)is 6208-227573 ng/g,and the total concentration of phenylsiloxane Σ(P4+P3)is 58-15439 ng/g,the concentration level of phenylsiloxane is much lower than that of cyclic methylsiloxane.Phenylsiloxanes were found in the sediments of 23 lakes and rivers around the oilfield.The concentration ranges of cis-P3,trans-P3,cis-P4,trans-P4 a,trans-P4 b,and transP4 c were as follows: LOD-107.66 ng/g,<LOD-182.15 ng/g,<LOD-100.64 ng/g,<LOD-92.45 ng/g,<LOD-67.60 ng/g,<LOD-60.33 ng/g,this work confirmed that the oilfield extraction process can lead to environmental emissions of methyl and phenylsiloxanes.Chapter 4 Since 2007,electro-oxidation technology has been applied in two petroleum wastewater treatment stations(Shin Nan and Guang Li)in Shengli Oilfield,and it may oxidize halogen ions(from the water in the reservoir)to free halogen.The halogenated products of methylsiloxane may be generated during the treatment of similar wastewater.Studies the emission sources,environmental distribution and bioaccumulation of methyl bromide in oil fields.First of all,this study confirmed the bromination of methylsiloxane during the electrooxidation process of the oil extraction wastewater treatment plant.Monomethylsiloxane was detected in the sludge of two oil extraction wastewater treatment stations equipped with electrooxidation devices.Brominated products(Br-cVMS),where the concentration ranges of D3D(CH2Br),D4D(CH2Br),and D5D(CH2Br)are 27.8-82.5 ng/g dw,180-337 ng/g dw,156-604ng/g dw.Bromomethylsiloxane was detected in the sediments of lakes near the oil production wastewater treatment station and freshwater mussels.The concentration of D3D(CH2Br)in the sediments ranged from <LOQ-103 ng/g dw(df = 37%),D4D(CH2Br)is <LOQ-131 ng/g dw(df = 37%),D5D(CH2Br)is <LOQ-101 ng/g dw(df = 32%).The concentrations of D3D(CH2Br),D4D(CH2Br)and D5D(CH2Br)in Anodonta woodiana are 10.8-303 ng/g dw(df = 100%),11.3-385 ng/g dw(df = 100%)and <LOQ-297 ng/g dw(df = 88%),in Corbicula fluminea it is 9.9-264 ng/g dw(df =100%),7.3-311 ng/g dw(df = 100%)and <LOQ-238 ng/g dw(df = 88%).Compared with the corresponding parent methyl siloxane,bromomethyl siloxane shows stronger environmental persistence and bioaccumulation.The average BSAF of Br-cVMS in freshwater mussels is 1.1-1.5 higher than the parent cVMS,the half-life of Br-cVMS is1.3-2.2 times longer than the half-life of parent cVMS.