Chen Jian-hua, Huang Xia
ESPC State Key Joint Laboratory, Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China.
Huan Jing Ke Xue. 2008 Sep;29(9):2481-7.
In order to investigate the fouling reasons and cleaning methods of nanofiltration membrane fouled with the effluent of membrane bioreactor (MBR), FEG-SEM-EDS, FTIR, AFM and contact angle system, were applied to analyze the membrane fouling layer. The results showed that, the foulants included both organic and inorganic substances, which contained phosphorous (P) and magnesium (Mg). After investigations of membrane surfaces through different cleaning steps, it was showed that critic acid cleaning could remove Mg and most of P, which were inorganic; and subsequent sodium hydroxide cleaning could remove the residual P, which probably came from organic acid, organic phosphorous or protein. The roughness increased from 79.5 nm to 111.2 nm with fouling, but the hydrophilicity didn't change obviously according to the contact angle from 55.6 degrees to 62.1 degrees. But after acid cleaning, the roughness decreased to 51.9 nm and the contact angle changed to be 96.0 degrees, which showed the organic foulants were exposed and the surface changed to be hydrophobic. And after subsequent alkali cleaning, the roughness and the hydrophilicity were both close to those of the new membrane. These results concluded that acid cleaning followed by alkali cleaning could remove most of the foulants. It was also suggested that organic matters fouled the membrane in the initial stage, and inorganic matters aggravated the membrane fouling subsequently.
为了探究膜生物反应器（MBR）出水导致纳滤膜污染的原因及清洗方法，采用场发射枪扫描电子显微镜-能谱仪（FEG-SEM-EDS）、傅里叶变换红外光谱仪（FTIR）、原子力显微镜（AFM）和接触角测量系统对膜污染层进行分析。结果表明，污染物包括有机和无机物质，其中含有磷（P）和镁（Mg）。通过不同清洗步骤对膜表面进行研究后发现，柠檬酸清洗可去除Mg和大部分无机的P；随后的氢氧化钠清洗可去除残留的P，这些P可能来自有机酸、有机磷或蛋白质。膜污染后粗糙度从79.5 nm增加到111.2 nm，但根据接触角从55.6°变为62.1°可知，亲水性没有明显变化。但酸洗后，粗糙度降至51.9 nm，接触角变为96.0°，这表明有机污染物暴露，表面变为疏水性。随后碱洗后，粗糙度和亲水性均接近新膜。这些结果表明，先酸洗后碱洗可去除大部分污染物。研究还表明，有机物在初始阶段污染膜，随后无机物加剧膜污染。
