The fouling characteristics of organic matters in salt lake brine on polyceramic membranes based on membrane dissection

In the process of membrane-based lithium extraction from salt lake brines, membrane fouling caused by dissolved organic matters in the brines has attracted widespread attention. To mitigate membrane fouling, an effective strategy is reducing organic content by pre-treating the salt lake brine. As a novel type of organic ultrafiltration membrane material, polyceramic membranes can effectively retain organic substances in salt lake brines without affecting their inorganic composition. This exhibits broad application prospects in the pretreatment of salt lake brines. However, there is a lack of in-depth understanding regarding the fouling characteristics of polyceramic membranes induced by dissolved organic matter in salt lake brines. In this work, two polyceramic membranes that had undergone two years of pretreatment with salt lake brine was dissected. The surface features and properties of the fouling layer on the membranes were characterized. By comparing the main components and characteristics of the surfaces and fouling layers between the new and used membranes, the fouling behavior of dissolved organic matter on polyceramic membranes was investigated. The findings revealed that prolonged pretreatment with brine led to the formation of an organic fouling layer composed of polysaccharides, proteins, fulvic acids, humic acids, etc., on the membrane surface. The specific composition and content varied depending on the membrane. Differences in functional groups on the membrane surface resulted in differentiated selective adsorption of organics. Interactions between the functional groups of dissolved organic matter and specific sites on the membrane surface occurred via hydrogen bonding and/or van der Waals forces. The organics were adsorbed onto the membrane surface or pore walls. The electrostatic repulsion among molecules like fulvic acid and humic acid through complexation was shielded by divalent cations such as calcium and magnesium in the brine, which promoting the aggregation and deposition of organic substances on the membrane surface. The degree of concentration polarization was influenced by altering hydrodynamic conditions through operational conditions and membrane module structures, which also affected the attachment process of organics on the membrane surface. Based on these observations, the formation process of the organic fouling layer was speculated. These findings provide a basis for understanding the fouling characteristics of dissolved organic matter on polyceramic membranes and for developing corresponding control strategies.