预涂动态膜强化超滤去除海水中有机物及其对膜污染的影响

以粉末活性炭和硅藻土为涂膜材料,在聚醚砜超滤膜表面形成预涂动态膜,考察了预涂动态膜对海水中有机物的去除效果和作用机制,通过比较分析直接超滤和预涂动态膜过滤海水前后膜表面亲疏水性、形貌结构、粗糙度及膜阻力分布的变化,探讨了活性炭和硅藻土预涂覆对超滤膜污染的影响.结果表明,预涂动态膜可提高超滤膜对海水中溶解有机碳(DOC)和UV_(254)的去除率,活性炭预涂动态膜对海水中DOC和UV_(254)的去除率较直接超滤分别提高11.2%和11.3%.硅藻土预涂膜主要利用超滤膜表面形成的硅藻土滤饼层强化海水中蛋白质类有机物的截留,活性炭对海水中小分子有机物的额外吸附导致海水过滤过程中活性炭预涂膜对有机物的去除效果优于硅藻土预涂膜.与直接超滤相比,预涂动态膜过滤海水后膜表面亲水性更好,膜表面粗糙度更低,膜过滤阻力也更小,活性炭预涂动态膜净化海水时膜过滤总阻力较直接超滤降低50.3%.利用涂膜材料在超滤膜表面形成的滤饼层将超滤膜与有机物进行了"隔离",避免了超滤膜与有机污染物直接接触,降低了小分子有机物在膜孔内的吸附堵塞,能够有效减缓超滤膜的不可逆污染.

Enhanced ultrafiltration for organic matter removal from seawater by precoated dynamic membrane and its effects on membrane fouling

Precoated dynamic membrane were prepared on the polyethersulfone (PES) ultrafiltration (UF) membrane, using powdered activated carbon (PAC) and diatomite as precoating materials, respectively. Removal efficiency and mechanism of organic matter in seawater by precoated dynamic membrane was investigated. A comparison of the surface hydrophilicity, morphology, roughness and fouling resistance between bare (un-precoated) and precoated membrane were made to analyze the effects of PAC and diatomite precoating on membrane fouling. Organic matter removal performance of the precoated membrane was better than that of the bare PES membrane. Removal rate of DOC and UV₂₅₄ was increased by 11.2% and 11.3%, respectively, when PAC was precoated on the membrane surface. The protein-like organic matter retention could be enhanced by diatomite precoated membrane, mainly because of the formation of diatomite layer on membrane surface. Greater organic matter removal efficiency was achieved using PAC precoated membrane than that of diatomite precoated membrane, due to the additional adsorption of low molecular weight organic matter by PAC. Because of higher hydrophilicity, lower roughness, and expressed smaller fouling resistance than bare membrane, the total fouling resistance (Rt) was reduced by 50.3% by precoating PAC on bare PES membrane in seawater pretreatment. Membrane and organic matter were divided by cake layer formed on the membrane surface of precoating material, leading to avoid organic contaminants direct contacting with ultrafiltration membrane. As a result, precoated dynamic membrane can mitigate the blockage of membrane pores by low molecular weight organic matter, which is of significance to irreversible membrane fouling control.