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Abstract 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.
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Received: 11 May 2015
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