The Preparation Of Layer-by-layer Self-assembled Composite Membrane And Its Pervaporation Performance

This paper aimed to prepare a high performance pervaporation composite membrane by layer by layer self-assembled method.The effects of parameters on the dehydration separation performance of the composite membrane were investigated by orthogonal experiment.The performance of the electric field assisted coating on the pervaporation membrane was verified.Poly(N,N-dimethylaminoethyl methacrylate)(PDMAEMA)and poly(acrylic acid)(PAA)were used as polycation and polyanion,respectively,and they were assembled on the negatively charged reverse osmosis polyamide membrane to build up PDMAEMA/PAA composite membrane to separate ethylene glycol/water mixtures.The L25 orthogonal array was used to investigate the effect of some parameters(number of bilayers,deposition time,heat treatment time,ratio of polyelectrolytes and PDMAEMA pH)on the morphology and pervaporation performance of membranes.The experimental results showed that the hydrophilicity of the composite membrane increased when the outermost layer is PAA.The permeation flux of layer by layer self-assembled membrane was 1.65 kg/(m2h)and the separation factor was 159.The results of variance analysis showed that the number of layers and the deposition time of single layer had the greatest influence on the pervaporation performance of the composite membrane.On this basis,an electric field was applied to assist in the preparation of the E-PDMAEMA/PAA composite membrane.The L9 orthogonal array was used to study the effects of coating number,coating time and voltage gradient on the pervaporation performance of the composite membrane.The effects of the electric field on the membrane structure and the dehydration performance of ethylene glycol were compared.The results showed that the electric field to assist the preparation of layer-by-layer self-assembled composite membrane can effectively improve the pervaporation performance of the composite membrane,and the electric field had no effect on the membrane surface structure.When the voltage gradient was 100 kV/m,the permeation flux of E-PDMAEMA/PAA composite membrane was increased by 80%and the separation factor was increased by 173%compared with the composite membrane prepared without electric field.