Tang Chuyang Y, Kwon Young-Nam, Leckie James O
Environmental Engineering and Science, Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305-4020, USA.
Environ Sci Technol. 2007 Feb 1;41(3):942-9. doi: 10.1021/es061322r.
Reverse osmosis and nanofiltration membranes fouled by humic acid were systematically characterized by transmission electron microscopy. All fouled membranes, except those with very low initial flux, were completely covered by a layer of humic acid whose thickness and density were greatly affected by the feedwater composition ([H+] and [Ca2+]) and initial flux. A low-density humic layer (about 0.1 g of purified Aldrich humic acid (PAHA)/cm3) was formed at low initial flux (2 m/day or less) at pH 7 without calcium. It was several times denser at a higher initial flux, pH 4.5, or 1 mM Ca2+. Corresponding to the denser foulant layers under these conditions, PAHA accumulation was greatly increased. The denser foulant layers together with the greater PAHA accumulations were responsible for the severe flux reductions. Both virgin and fouled membranes were characterized by streaming potential measurements. While considerable differences existed for virgin membranes, humic acid fouled membranes exhibited identical surface charge properties. The zeta potential of the fouled membranes was controlled by the humic acid layer due to its complete coverage of the membrane surfaces.
采用透射电子显微镜对被腐殖酸污染的反渗透膜和纳滤膜进行了系统表征。除初始通量极低的膜外，所有被污染的膜均被一层腐殖酸完全覆盖，腐殖酸层的厚度和密度受进水组成（[H⁺]和[Ca²⁺]）及初始通量的影响很大。在pH值为7且无钙的情况下，低初始通量（2米/天或更低）时会形成低密度的腐殖层（约0.1克纯化的Aldrich腐殖酸（PAHA）/立方厘米）。在较高初始通量、pH值为4.5或1毫摩尔/升Ca²⁺的条件下，其密度会增加数倍。在这些条件下，与更致密的污垢层相对应，PAHA的积累量大幅增加。更致密的污垢层以及更多的PAHA积累导致了通量的严重降低。通过流动电位测量对原始膜和被污染膜进行了表征。虽然原始膜存在相当大的差异，但被腐殖酸污染的膜表现出相同的表面电荷特性。由于腐殖酸层完全覆盖膜表面，被污染膜的ζ电位由腐殖酸层控制。
