Research Of Nanofiltration Membrane Based On Dendrimer Molecule

Nanofiltration（NF）is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration.It is generally believed that NF membrane has a pore size of about 1nm,and can be used for effective separation of salt and small molecule organic matter.The composite NF membrane prepared by interfacial polymerization method is the mainstream product of the current market.Due to the complexity of the feed solution,the permeation flux,selectivity and pollution resistance of the membrane remain to be improved.In this paper,we first synthesized a dendrimer trimesoyl amide amine（TMAAM）.Then it was combined with piperazine（PIP）in the aqueous solution to react with trimesoyl chloride（TMC）via interfacial polymerization to obtain a semi-aromatic polyamide TFC NF membrane,and the effect of doping-content of TMAAM on the NF membrane performance was investigated.Moreover,the resultant NF membranes were characterized by using ATR-FTIR、XPS、FESEM、AFM,surface water contact angle and surface zeta potential.The main conclusions were as following:（1）With increasing TMAAM content in TMAAM/PIP mixtures,the water flux continually increased while the rejection rate decreased.When the content of TMAAM was 50%,the water flux of membrane（NF-2）increased up to be 72.3L/m²·h,which is about 60%higher than the pristine NF membrane（NF-0）.Meanwhile,the salt rejection of the NF-2 membrane changed slightly,and the membrane surface was smoother and more hydrophilicity.（2）The separation performance of the nanofiltration membrane（NF-2）for methyl blue,semixylenol orange,safranine T and neutral red were measured,respectively.The results showed that the NF-2 membrane had excellent rejection to the dyes with molecular weight above 200.（3）The antifouling and stability property of the membrane were analyzed by BSA solution（500 ppm）and Na₂SO₄（1000 ppm）at 25°C and 6 bar.The results showed that the NF-2 exhibited better antifouling and stability properties than the traditional aromatic polyamide nanofiltration membrane.In this study,the dendrimer TMAAM was used to fabricate a new semi-aromatic polyamide composite nanofiltration membrane through a simple and convenient interfacial polymerization method,and the resultant NF membrane has favourable hydrophilicity,stability and better antifouling property.