The Study On Preparation And Application Of Multilayer Polysulfonamide Composite Membranes

With the gradual development of the industry,the material composition of the system to be separated becomes ever more complicated,and material handling becomes more difficult.This puts forward higher requirements and standards for the membrane separation technology,that is,the membrane for treating the material system not only has excellent separation and selection performance,but also has good physical and chemical resistance（such as acid and alkali resistance,solvent resistance et）.At present,acidic wastewater in industrial production is the most common.Common commercial polyamide membranes and cellulose acetate membranes cannot handle strong acid materials due to insufficient acid tolerance,while other polymers with good acid tolerance（such as polysulfone）,the membranes prepared by the polymers have poor separation effect.Therefore,selecting a membrane material which has both decent acid stability and good film-forming properties is expected to realize the large-scale application of membrane separation technology to industrial acid material processing.In this study,polysulfonamide（PSA）reverse osmosis membrane with excellent separation performance and good acid stability was prepared by spin-coating multi-layer interfacial polymerization.First,l,3,6-naphthalene trisulfonyl chloride（NTSC）and triethylenetetramine（TETA）synthesized according to the literature are two-phase reaction monomers.Polysulfonamide reverse osmosis composite membrane was prepared by multilayer interfacial polymerization on a porous polyethersulfone（PES）support layer.The effects of monomer concentration and interfacial polymerization layer on the separation performance of reverse osmosis membrane were systematically studied to obtain the best membrane preparation parameters.Afterwards,the surface physicochemical properties and morphology of the polysulfonamide reverse osmosis membrane were characterized by instrumental analysis such as ATR-FTIR,Zeta potential,CA and ellipsometry.Then,the cross-flow test was used to evaluate the separation performance of polysulfonamide reverse osmosis membrane for different salt solutions.The experimental results show that the optimal film formation parameters are:triethylenetetramine（TETA）=0.07w/v%,triethylamine（TEA）=2 w/v%,l,3,6-Naphthalene trisulfonyl chloride（NTSC）=0.05 w/v%,reaction time=30 s,number of layers=5,heat treatment temperature=80°C,heat treatment time=2 min.The polysulfonamide reverse osmosis membrane prepared under this condition achieved the best separation performance,the order of retention performance for different inorganic salts is:RNa2SO4<RNa Cl<RMg SO₄<RCa Cl2.Moreover,experiments have found that there is a certain linear relationship between the film thickness and the number of interfacial polymerization layers.For each additional layer,the film thickness increases by about 9 nm.Secondly,the study also investigated the effect of the structure of the amine monomer on the separation performance of the polysulfonamide reverse osmosis membrane,and selected1,4-bis（aminopropyl）piperazine and tris-（2-aminoethyl）amine.Different structures of quaternary amines act as aqueous phase monomers.The results show that three different structures of triethylene tetramine（TETA）,tris-（2-aminoethyl）amine（TAEA）and 1,4-bis（3-aminopropyl）amine（DAPP）,the interfacial polymerization of amine and NTSC can produce a smooth and ultra-thin polysulfonamide composite membrane,and can achieve a high separation level by increasing the number of interfacial polymerization layers.Finally,the subject tested the resistance of polysulfonamide reverse osmosis membrane to high concentration sulfuric acid by high temperature immersion test,and studied the effect of polysulfonamide membrane on the treatment of actual acidic materials.Experiments show that the separation performance of polysulfonamide membrane has not decreased significantly after immersion in 20 w/w%sulfuric acid solution at 90°C for 24 h,and the surface chemistry and morphology have not changed significantly.Moreover,polysulfonamide membrane has excellent removal effect on heavy metal ions in titanium dioxide wastewater.