XDLVO理论解析有机物和钙离子对纳滤膜生物污染的影响

为了揭示有机物和Ca2+浓度对纳滤膜生物污染的影响机制,选用铜绿假单胞菌(PA)为模式菌株,海藻酸钠(SA)、牛血清白蛋白(BSA)和腐殖酸(HA)为典型废水有机物,采用extended derjaguin–landau–verwey–overbeek(XDLVO)理论定量解析了不同进水条件下膜预处理和生物污染过程的界面相互作用.结果表明,Ca2+浓度为5mmol/L时,SA预处理后膜面亲水性最强,粘聚自由能高达42.96mJ/m2,与PA、SA的界面自由能最高,分别为45.85和39.64mJ/m2,抑制膜的生物污染.而Ca2+浓度为2mmol/L时,BSA预处理后膜面疏水性最强,粘聚自由能低至–40.32mJ/m2,与PA、BSA的界面自由能最低,分别为3.49和–26.36mJ/m2,促进膜的生物污染.所有污染过程中,范德华作用能差异较小,而静电作用能绝对值极小,贡献微弱,有机物和Ca2+浓度对膜生物污染的影响主要体现在对疏水作用能的影响.

Impact of organic matter and calcium on nanofiltration membrane biofouling: XDLVO approach

The extended derjaguin-laudau-verwey-overbeek (XDLVO) theory was utilized to quantitatively evaluate the interfacial interactions in organic conditioning and biofouling of nanofiltration membrane under various organic matter and Ca2+ concentrations. Pseudomonas aeruginosa (PA) was selected as the model bacterium, and sodium alginate (SA), bovine serum albumin (BSA), and humic acid (HA) were selected as model organics in wastewater. Results showed that SA conditioned membranes have the strongest hydrophilicity and the biggest interfacial free energies with PA and SA at 5mmol/L Ca2+, with a DGcoh of 42.96mJ/m2 and DGadh of 45.85and 39.64mJ/m2, respectively. This condition inhibited the biofouling of membranes. However, BSA conditioned membranes have the strongest hydrophobicity and the lowest interfacial free energies with PA and BSA at 2mmol/L Ca2+, with a DGcoh of –40.32mJ/m2and DGadh of 3.49 and –26.36mJ/m2, respectively. This condition accelerated the biofouling of membranes. In all membrane fouling processes, vander Waals interactions changed slightly, whereas electrostatic double layer interactions contributed minimally to fouling with a low absolute value. Organic matter and Ca2+ affected the membrane biofouling mainly through the alteration of hydrophobic interactions.