Preparation And Properties Of Forward Osmosis Membrane Based On Lignocellulose Derivatives

Lignocellulosic materials are a kind of natural polymer materials with development potential.It can replace synthetic polymer materials and reduce the dependence on fossil resources and environmental pollution.As one of the important components of biomass,wood-based biomass is mainly composed of cellulose,hemicellulose and lignin.The development of forward osmosis separation membranes based on lignocellulose derivatives as raw materials can save costs,protect the environment,and achieve high-value utilization of biomass.Forward osmosis technology is a new type of osmosis-driven membrane separation technology developed in recent years.It is different from pressure-driven membrane separation technologies such as nanofiltration,ultrafiltration,and reverse osmosis.It does not require external pressure and has alternative anti-pollution capabilities.The performance is widely used in the fields of desalination,sewage treatment,food processing,medicine control and seawater power generation.In this study,we propose to use lignin and cellulose derivatives,namely sodium lignosulfonate(SL)and cellulose triacetate(CTA),to prepare a new type of polyethyleneimine/sodium lignosulfonate forward osmosis membrane and surface Pattern the cellulose triacetate forward osmosis membrane,and further optimize the prepared forward osmosis membrane to improve its separation performance.(1)Multilayer PEI/SL positive permeation membranes were prepared by electrostatic layer-by-layer self-assembly method using sodium lignosulfonate and polyethyleneimine(PEI)as the polyanionic and polycationic electrolytes,respectively.The forward osmosis performance test found that the separation effect of the PEI/SL membrane with 2 layers is the best,with a water flux of 4.4LMH and a reverse salt flux of 4.02 g MH.(2)Further using the microporous channels of carbon nanotubes(CNTs)to prepare CNTs modified PEI/SL forward osmosis membranes by dispersing CNTs in PEI or SL solutions separately or at the same time,and align them by exploring CNTs Permeating CNTs can increase the water flux of the PEI/SL membrane,and when the CNTs are dispersed in the SL polyelectrolyte solution at a concentration of 0.075 g/L,the separation effect of the modified membrane is the best,and the water flux is increased to 7.32 LMH,reverse salt The flux is 3.56 g MH,and it shows good anti-pollution ability.(3)Using CTA as the membrane material,a patterned template was used to prepare the patterned(Y and X pattern)CTA forward osmosis membrane by the immersion phase inversion method,and the effect of the surface pattern on the membrane structure and performance was studied.Compared with the unpatterned flat CTA membrane,the water flux of the patterned CTA membrane is significantly improved,and the CTA-X patterned membrane has the best separation effect.Its water flux is 53.16 LMH,and the reverse salt flux is 0.46 g MH(AL-FS mode).(4)In order to further improve the separation performance of CTA membrane,use p-nitrophenol(PNP)as a plasticizer to modify the CTA membrane.PNP modification can increase the water flux but reduce the reverse salt flux.Its water flux size is: flat modified(32.38 LMH)<Y modified(40.62 LMH)<X modified(58.56 LMH),reverse salt The flux size is: flat modified(0.2 g MH)<X modified(0.27 g MH)<Y modified(0.48 g MH).Therefore,the X-patterned membrane after PNP treatment has the best selectivity.