超支化聚酯低压纳滤膜的制备与表征

PREPARATION AND CHARACTERIZATION OF LOW-PRESSURE NANOFILTRATION MEMBRANES BASEDON CROSSLINKED HYPERBRANCHED POLYESTER

通过超支化聚酯(HPE)末端的羟基与戊二醛(GA)之间的羟醛缩合反应,采用简单的浸涂-交联方法,制备了一种以聚砜超滤膜为支撑层,交联的HPE为活性分离层的复合纳滤膜.采用衰减全反射红外光谱(ATR-FTIR)、接触角测定、扫描电子显微镜(SEM)对纳滤膜的表面化学组成、亲水性和膜形貌进行了表征.考察了HPE溶液浓度、GA溶液浓度对膜分离和渗透性能的影响,优化的HPE和GA溶液浓度分别为9.8 g/L和7.4 g/L,此时在0.4 MPa下膜的水通量达69.6 L/(m2.h),对Na2SO4脱除率为93.2%,表现出低操作压力、高通量、高脱盐率的优异性能.纳滤膜对无机盐的截留顺序为Na2SO4>NaCl>MgSO4>MgCl2,呈现明显的荷负电特征.

Thin-film composite nanofiltration membranes were prepared by a simple dipping and crosslinking process. A polysulfone （PSF） ultrafihration membrane was used as the support and a crosslinked hyperbranched polyester （HPE） as the active separation layer. The separation layer was immobilized onto the support via the aldol condensation of HPE with glutaraldehyde （GA）. The prepared membranes were characterized by attenuated total reflection Fourier transform infrared spectroscopy （ATR-FTIR）, water contact angle measurements and scanning electron microscopy （SEM）. The results of FTIR examination confirmed the existence of crosslinked HPE layer on membrane surface. The results of SEM observation indicated that a thin dense layer of crosslinked HPE was deposited on the support membrane. Water contact angle measurements showed that the membrane hydrophilieity was significantly improved. The effects of HPE concentration and GA concentration during membrane preparation on the separation and permeation properties were investigated. The optimized HPE and GA concentrations were 9.8 g/L and 7.4 g/L,respectively, and the water flux for the resultant membrane reached 69.6 L/（m^2·h）, and the Na2SO4 rejection ratio was 93.2 %. The sequence of rejection ratio to various salts was Na2 SO4 〉 NaCl 〉 MgSO4 〉 MgCl2 , which was characteristic of eleetronegative nanofihration membranes. These results showed that a high performance nanofihration membrane with low operation pressure, high permeability and high rejection could be obtained by the present process.