Study On Acrylamide Adsorbents And Adsorption Ultrafiltration Membranes

As a common flocculant in drinking water treatment industry,Polyacrylamide can remove colloidal substances and suspended solids in water.Polyacrylamide has no toxicity,but in the process of use,a small amount of residual polyacrylamide in water will produce carcinogenic polar small molecule acrylamide through degradation.No matter the traditional drinking water purification process or the third generation drinking water purification process with ultrafiltration as the core technology,it can not effectively remove acrylamide.In order to make the third generation drinking water purification process have the function of removing this potential hazard,and prepare the ultrafiltration membrane which can remove acrylamide,this dissertation carried out two aspects of research:the selection of adsorbents and the preparation of adsorption ultrafiltration membrane.At present,there are few reports about acrylamide adsorbent and adsorption ultrafiltration membrane.Therefore,this study not only has high theoretical value,but also has a certain amount of practical value.In this dissertation,the adsorption properties of 36 kinds of adsorbents were studied.The 0.1 g adsorbent was put into 50 m L acrylamide solution with mass concentration of 240 mg·L^-1 and acrylamide was adsorbed by the adsorbent for 24 hours at 303K.The following conclusions were drawn:Several kinds of materials have better adsorption effect on acrylamide,such as activated carbon,modified Si O₂aerogel and chitosan.The maximum adsorption capacity was 27.51 mg·g^-1,3.75 mg·g^-1and 2.77mg·g^-1 respectively.The kinetic,isotherm and thermodynamic studies of acrylamide on activated carbon showed that the adsorption kinetics can be well fitted to the pseudo-second-order kinetics model,the adsorption isotherm can be well fitted to the Freundlich adsorption model,and the adsorption activation energy was about 6.26k J·mol^-1.Then activated carbon（AC）and modified Si O₂ aerogel（MTMOS）were selected as additives,polyethersulfone（PES）was used as substrate,polyvinylpyrrolidone（PVP）was used as porogen,N’N-2-methyl acetamide（DMAC）was used as solvent,two kinds of adsorption ultrafiltration membranes were prepared by phase inversion method.The membrane was characterized by scanning electron microscope and contact anglemea suring instrument.The pure water flux,rejection rate and anti pollution performance of the membrane were tested by ultrafiltration device.Finally,the adsorption performance of the membrane for acrylamide was explored.（1）When the addition of AC varied from 0wt%to 10wt%:the hydrophilicity,pure water flux recovery rate and anti pollution ability of the membrane were improved,the initial rejection rate of membrane to bovine serum albumin decreased from 88.34%to60.61%,when the content of AC was 4wt%,the pure water flux of the membrane reached the maximum of 195.42 L·m^-2·h^-1,which was 32.36%higher than that of pure PES membrane of 132.19 L·m^-2·h^-1.With the increase of AC content from 0wt%to10wt%,the saturated adsorption capacity of membrane for acrylamide increased from0.59 mg·g^-1 to 4.97 mg·g^-1.The adsorption kinetics of acrylamide on the membrane can be well fitted to the pseudo-second-order kinetics model,and the adsorption isotherm of acrylamide can be well fitted to the Freundlich adsorption isotherm model.When 10mg·L^-1 acrylamide solution was used as feed solution for filtration experiment,the removal rate of acrylamide by PES/AC membrane reached 4.80%,and the recovery rate of membrane was more than 90%after cleaning with methanol.（2）When the addition of MTMOS varied from 0wt%to 30wt%:the hydrophilicity,pure water flux recovery rate and anti pollution ability of the membrane were reduced,The initial rejection of bovine serum albumin by membrane increased from 72.15%to84.50%,when the addition of MTMOS was 30wt%,the pure water flux of the membrane reached the maximum of 180.72 L·m^-2·h^-1,which was 22.50%higher than that of pure PES membrane of 140.05 L·m^-2·h^-1.With the increase of MTMOS content from 0wt%to 30wt%,the saturated adsorption capacity of membrane for acrylamide increased from 0.76 mg·g^-1 to 2.53 mg·g^-1.The adsorption kinetics of acrylamide on the membrane can be well fitted to the pseudo-second-order kinetics model,and the adsorption isotherm of acrylamide can be well fitted to the Freundlich adsorption isotherm model.When 10 mg·L^-1 acrylamide solution was used as feed solution for filtration experiment,The removal rate of acrylamide by PES/MTMOS membrane was only 2.10%when it was the highest.After cleaning with methanol,the recovery rate of membrane was more than 90%.