Cross-linked Polyvinyl Alcohol/polytetrafluoroethylene Membrane Separation And Recovery Of High-salinity Alkaline Cellulose Wastewater

Membrane technology,as an environmentally friendly treatment process without secondary pollution,has been applied in the field of macromolecule and saline-alkali recovery.However,it is accompanied by a large amount of energy consumption and high processing cost.In addition,for the recovery of alkali and salt,the stability of the membrane material in the lye will become a key factor limiting the recovery of alkali.In response to the above problems,in this thesis,a hydrophilic polymer with good alkali resistance-polyvinyl alcohol(PVA)was chosen as the membrane material and polytetrafluoroethylene(PTFE)was chosen as the organic additive to prepare the PVA/PTFE membrane through heat and glutaraldehyde(GA)cross-linking.First,the non-solvent induced phase inversion method(NIPS)was used to prepare PVA/PTFE membranes.After a reasonable cross-linking strategy,heat cross-linked PVA/PTFE membranes and chemical cross-linked PVA/PTFE membranes were obtained.The influence of PTFE,polyethylene glycol(PEG1000)and glutaraldehyde(GA)content on the structure and performance of the membrane was systematically studied.The performance of heat cross-linked and chemical cross-linked PVA/PTFE membrane for Carboxymethyl Cellulose Sodium(CMC)and saline-alkali separation was tested.The saline-alkali permeability,CMC removal rate and flux were 93.0%,99.3%,220.00(L/m²h)and 93.4%,99.4%,89.20(L/m²h),respectively.In addition,the chemical cross-linked PVA/PTFE membrane showed stable and effective separation performance in the 24 h separation test.Secondly,the heat cross-linked PVA/PTFE membrane and chemical cross-linked PVA/PTFE membrane were used in the diffusion dialysis(DD)process.The alkali resistance of the membrane was explored.The surface morphology of the membranes was characterized by scanning electron microscopy(FESEM).The DD performance of the membrane results showed that the heat cross-linked PVA/PTFE membrane has the best diffusion dialysis effect:U_OHis 0.0227 m/h,and the separation coefficient(S)is 16.01.In the actual separation of CMC and saline-alkali,it was found that the heat cross-linked PVA/PTFE membrane has a higher ion flux,6.40 mol/m²·h(Na OH 2g/L)and 2.69 mol/m²·h(Na Cl 2g/L).The heat cross-linked PVA/PTFE membrane also has excellent performance in the process of multiple dialysis,and its alkali concentration(Na OH 2g/L)can be reduced by half in three DD processes.In this study,PVA/PTFE membranes were prepared in a reasonable cross-linking manner,and high salinity cellulose wastewater was treated by cross-flow filtration and diffusion dialysis,respectively.Ultrafiltration membrane was combined with diffusion dialysis membrane to expand the application scope of PVA membrane.