| In recent years,with haze weather occuring frequently,people have been paying increasing attention to air quality.Volatile organic compounds（VOC）emitted from transportation,industrial production and people’s lives are one of the important sources of pollution.In addition,due to the decrease of fossil resources on the earth and the unreasonable use of fossil resources,human beings are facing two major problems,energy and environment.Therefore,searching for alternative energy sources and environmental protection is the current research hotspots.Firstly,as a new alternative energy source,biogas is produced by anaerobic digestion of organic matter in landfills and sewage treatment plants.However,a small amount of volatile methylsiloxane（VMS）in biogas has seriously hindered the application and development of biogas.Because the combustion of VMS will produce tiny SiO2 crystals,which will cause serious wear and tear to the machine and shorten its service life.To solve the problem of safe utilization of biogas energy,its quality must be improved.Therefore,it is very important to study on the VMS removal from biogas.Secondly,benzene homologues,such as benzene,toluene,ethylbenzene and xylene,are the main members of volatile organic compounds.It mainly comes from various industrial and living activities,such as chemical production,building decoration and vehicle emissions.When it spreads into the environment,it will seriously endanger human health.In mild cases,it will cause skin allergies,respiratory diseases and endocrine disorders.In serious cases,it will cause liver and kidney damage,cardiovascular diseases and even canceration.Therefore,the elimination of such pollutants is an important topic in environmental governance research,and has practical significance.Silica gel material is a kind of material which is cheap,easy to obtain and has very good porosity,thus is widely used.However,the preparation,functional regulation and application development of silica gel materials still need to be further studied.On the basis of previous work,this paper continues to explore the preparation methods of silica gel materials,and regulate the structure and function of silica gel materials to improve their performance,for purification treatment of benzene series VOC and VMS.The specific research methods and results are as follows:1.Preparation of functionalized silica gel materials and performance evaluation of VMS purification.（1）Acetylated silica gel material（Ac@SG）was successfully prepared by acylation reaction,and the optimum preparation conditions were obtained:reaction temperature was 90oC,reaction time was 10 h,mass ratio was 3:8.Compared with silica gel,the micropore volume and specific surface area of Ac@SG increased from 0.13 cm3·g-1 and 286.4 m2·g-1 to0.16 cm3·g-1 and 368.9 m2·g-1,respectively,and the hydrophobic properties also improved significantly.In the VMS adsorption evaluation experiment,the acetylation modification of silica gel significantly improved the purification performance of VMS.At room temperature,the breakthrough time（tB）for Ac@SG adsorbing L2 was 54.3 min,the penetration adsorption capacity（QB）was 281.6 mg·g-1,the saturated adsorption capacity（Qm）was 303.9 mg·g-1,the tB for Ac@SG adsorbing D4 was 29 h,QB was 850.8 mg·g-1 and Qm was 915.7 mg·g-1.In addition,it was found that lowering the temperature and increasing the height of adsorption bed were beneficial to the adsorption of L2 by Ac@SG,but the presence of water had no significant effect on the adsorption.The adsorbent was recycled five times by thermal desorption method,and it was found that the adsorbent had stable performance.（2）The porosity of silica gel material is a main factor affecting the purification of VMS.In order to investigate the effect of porosity on the purification performance of VMS,silica gel with ink-like bottle pore was prepared by polyethyleneimine（PEI）mixing graft/regulate methods.Compared with SG material,the average pore radius and specific surface area were increased.In the preparation of materials,the optimum adsorption material for VMS was obtained by 3.0 of pH and adding 1.0 g PEI,and the optimum tB was 56.3 min and QB was289.0 mg·g-1.The characterization of PEI-regulated silica gel（PEI@SG）and VMS purification were studied.It was found that the main adsorption mechanisms for L2 were monolayer adsorption on microporous surface and mesoporous wetting adsorption,and the adsorption performance decreased with temperature increasing.In addition,there was no significant change in recycling of PEI@SG for five times,and t B kept 5256 min.The results showed that PEI@SG had good recycling performance.（3）In order to explore the effect of hydrophobicity on the removal performance of VMS,hydrophobic aerogel material(NA@SGair)was successfully prepared by chemical step by step synthesis method,and its contact Angle is 142.3o,with good hydrophobic performance.The results of SEM and BET showed that the pore size and pore volume of silica gel changed before and after hydrophobicity regulation.In the study of NA@SGairir adsorbing L2,it was found that hydrophobic regulation helped to enhance the adsorption properties of silica gel on L2.Compared with silica gel aerogels(SGair),tB and QB increased from 29.6 min and 152mg·g-1 to 55.2 min and 283.4 mg·g-1,respectively.The tB and QB remained unchanged in recycling of NA@SG for five times by thermal desorption method,which proved that the material had good reusability performance.2.Study on the efficient purification of o-Xylene by silica gel supported sulfuric acid and its mechanism.Silica gel supported sulfuric acid（SSSA）was successfully prepared by isovolumetric impregnation method,and the removal performance of o-Xylene by SSSA was studied on a dynamic adsorption platform.The results showed that this method not only had a high removal rate of o-xylene and could be recycled,but also obtained useful chemical products,3,4-Dimethylbenzene sulfonic acid and Bis（3,4-dimethyl）benzene sulfone.The by-product is water and the treatment process is environment-friendly.In addition,it was found that H2SO4loading and adsorption temperature were the main factors which affected the removal of o-Xylene by SSSA.The results showed that the optimum adsorption conditions were the loading of 20 mmol·g-1 and adsorption temperature of 130140 oC.Finally,according to the characterization results of SEM,FTIR and NMR,it was proposed that the removal of o-Xylene by SSSA followed the chemical reaction adsorption mechanism.To sum up,in view of the purification of two typical VOC pollutants,four types of silica gel materials have been successfully developed,such as,acetylated silica gel（Ac@SG）,polyethyleneimine-regulated silica gel（PEI@SG）,hydrophobic silica aerogel(NA@SGair)and silica gel supported sulfuric acid（SSSA）.After evaluating the performance of the above four materials in purifying o-xylene and VMS,the relevant influencing factors and purification mechanism are discussed.It can provide new materials and methods for the purification of VMS in biogas and the treatment of benzene-based VOCs pollution,which has important theoretical and practical significance. |
