荷负电超滤膜同时去除水中天然有机物和铅离子

Simultaneous removal of natural organic matter(NOM) and lead ion(Ⅱ)in water using charged ultrafiltration membranes

通过特定的化学反应对截留分子量为30 k D的再生纤维素(RC)超滤膜进行改性,得到荷负电超滤膜,并研究了其表面荷电性能。选用腐殖酸作为天然有机物的代表物质,研究荷负电改性膜同时去除溶液中腐殖酸和铅离子,主要考察了p H值和腐殖酸铅离子络合作用对两者截留率的影响,并对比了荷负电膜和未改性膜去除天然有机物和铅离子的研究结果。得到如下结论:(1)在酸性及中性溶液环境下,随着p H值的升高,荷负电超滤膜对腐殖酸和铅离子的截留率都提高。(2)铅离子与腐殖酸共存时,腐殖酸铅离子络合体的荷负电性相比于原腐殖酸分子降低,荷负电超滤膜对混合溶液中腐殖酸的截留率有一定程度降低,络合在腐殖酸表面的铅离子随着腐殖酸的截留而被截留,铅离子截留率得到一定程度提升。(3)由于腐殖酸与铅离子络合体带负电,其与荷负电膜之间存在静电作用,所以荷负电改性膜对腐殖酸和铅离子的截留率比未改性中性膜高。

Charged ultrafiltration membranes were generated by covalent attachment of negatively charged groups to commercially available regenerated cellulose membranes with molecular weight cut-off（ MWCO） of30 k Da. Humic acid was chosen as a representative for NOM. Simultaneous rejections of humic acid and lead ion（ Ⅱ） from water were investigated using negatively charged UF membranes and the effect of p H value and complexation between HA and Pb2 ＋were studied. In addition,the results of simultaneous removal rejections of HA and Pb2 ＋using charged membranes and unmodified membranes were compared. The following results were obtained：（ 1） In acidic or neutral solution environment,with the increase of p H value,the rejection rates of both humic acid and lead ion increased for charged membranes.（ 2） When the lead ion coexisted with humic acid,the rejections of HA decreased due to the smaller negative charge of HA- Pb2 ＋complex compared with HA molecule.While the rejections of Pb2 ＋ions increased because they were rejected more by negatively charged modified UF membranes when they complexed with HA.（ 3） Because of the electrostatic repulsion between humic acid and the charged membrane,the rejections of both NOM and Pb2 ＋were higher for negatively charged membranes than those for unmodified membranes.