University of Botswana, Department of Chemistry, Private Bag UB 00704, Gaborone, Botswana.
Langmuir. 2010 Mar 16;26(6):3902-10. doi: 10.1021/la9031046.
An extract from the seeds of the Moringa oleifera tree that is principally a low molecular mass protein is known to be efficient as a coagulating agent for water treatment. The present paper investigates the adsorption of the purified protein to silica interfaces in order to elucidate the mechanism of its function as a flocculent. Neutron reflection permits the determination of the structure and composition of interfacial layers at the solid/solution interface. Dense layers of protein with about 5.5 mg m(-2) were found at concentrations above 0.025% wt. The overall thickness with a dense layer in excess of 60 A at 0.05 wt % suggests strong co-operative binding rather than single isolated molecules. An ionic surfactant, sodium dodecyl sulfate, was also seen to coadsorb. This strong adsorption of protein in combination with the tendency for the protein to associate suggests a mechanism for destabilizing particulate dispersions to provide filterable water. This can occur even for the protein that has previously been identified as being of low mass (about 7 kDaltons) and thus is unlikely to be efficient in bridging or depletion flocculation.
从辣木树种子中提取的一种主要是低分子量蛋白质的物质，已知对水处理具有有效的凝结作用。本文研究了纯化蛋白质在硅胶界面上的吸附，以阐明其作为絮凝剂的作用机制。中子反射允许在固/液界面处确定界面层的结构和组成。在浓度高于 0.025%wt 时，发现了浓度超过 5.5mg m(-2)的蛋白质的致密层。在 0.05wt%时，整体厚度超过 60Å的致密层表明，强协同结合而不是单个孤立的分子。还观察到离子表面活性剂十二烷基硫酸钠共同吸附。这种蛋白质的强烈吸附以及蛋白质聚集的趋势表明了一种使颗粒分散体失稳以提供可过滤水的机制。即使对于先前被确定为低质量（约 7kDa）的蛋白质也是如此，因此不太可能有效地桥接或耗尽絮凝。
