Abstract Dissolved silica and organic matter are major membrane foulants in desalination of brackish water and wastewater by reverse osmosis. However, the interaction between inorganic silica species and dissolved organic molecules and their combined impact on membrane fouling are poorly understood. In this study, we have used sodium silicate and sodium alginate as model inorganic and organic foulants, respectively. Membrane fouling experiments showed a cooperative effect between the dissolved silica and alginate macromolecules, which aggravated membrane fouling. The molecular interactions between sodium alginate and sodium silicate and the properties of the formed complexes were determined by X-ray diffraction and X-ray photoelectron spectroscopy. Results show that the crystallinity of the formed complexes decreased as we increased the ratio of silica in the silica-alginate mixture, indicating the formation of amorphous complexes. Full reflection Fourier transform infrared spectroscopy also confirms new functional groups following the interaction between silica and alginate. Isothermal titration calorimetry was also employed to quantitatively determine the binding parameters by measuring the heat change during the reaction. When binding occurs between silica and alginate, the measured adsorbed or released heat is used to determine the binding constants as well as the enthalpy and entropy changes. Our results suggest that the interaction between silica and alginate is spontaneously exothermic and dominated by noncovalent bonding. Our findings provide fundamental insights into the complexation between silica and alginate in reverse osmosis membrane fouling and highlight the binding mechanism between silica and alginate molecules.

中文翻译：

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溶解二氧化硅和藻酸盐分子之间的络合：对反渗透膜污染的影响

摘要 溶解性二氧化硅和有机物是反渗透淡化苦咸水和废水的主要膜污染物。然而，人们对无机二氧化硅物质与溶解的有机分子之间的相互作用及其对膜污染的综合影响知之甚少。在本研究中，我们分别使用硅酸钠和海藻酸钠作为模型无机和有机污染物。膜污染实验表明溶解的二氧化硅和藻酸盐大分子之间存在协同作用，这加剧了膜污染。海藻酸钠和硅酸钠之间的分子相互作用和形成的配合物的性质是通过 X 射线衍射和 X 射线光电子能谱确定的。结果表明，随着我们增加二氧化硅-藻酸盐混合物中二氧化硅的比例，形成的复合物的结晶度降低，表明形成了无定形复合物。全反射傅里叶变换红外光谱也证实了二氧化硅和藻酸盐相互作用后的新官能团。等温滴定量热法也用于通过测量反应过程中的热变化来定量确定结合参数。当二氧化硅和藻酸盐之间发生结合时，测量的吸附或释放的热量用于确定结合常数以及焓和熵的变化。我们的结果表明，二氧化硅和藻酸盐之间的相互作用是自发放热的，并以非共价键为主。