Detection of reverse osmosis membrane fouling with silica, bovine serum albumin and their mixture using in-situ electrical impedance spectroscopy

• Published in: Journal of membrane science Vol. 443; pp. 45 - 53
• Main Authors: Sim, L.N., Wang, Z.J., Gu, J., Coster, H.G.L., Fane, A.G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-09-2013; Elsevier
• Subjects: artificial membranes; bovine serum albumin; BSA; Chemistry; Colloidal state and disperse state; dielectric spectroscopy; Electrical impedance spectroscopy; electrodes; Exact sciences and technology; filtration; Fouling; General and physical chemistry; impedance; industry; Membranes; monitoring; reverse osmosis; RO membrane; Silica; BSA; Fouling; Electrical impedance spectroscopy; Silica; RO membrane; Binary compound; Bovine; In situ; Serum albumin; Membrane separation; Vertebrata; Mammalia; Membrane; Reverse osmosis; Artiodactyla; Ungulata; Electrical impedance
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2013.04.047

Monitoring the ‘state of the process’ is particularly useful in fouling control in the reverse osmosis (RO) industry. In this paper, a novel non-invasive method to monitor the fouling process of single and binary foulants on the RO membrane has been studied; that of electrical impedance spectroscopy (EIS). A typical RO crossflow cell was equipped with electrodes to allow in-situ EIS measurement of the fouling process during RO filtration. The EIS signals were converted to Nyquist plots of the negative imaginary impedance versus the real impedance, and used as a convenient means for characterization of fouling. Different forms of the Nyquist plot were obtained for different types of foulant. Also a significant shift in the Nyquist plots for silica, BSA and their mixtures occurred corresponding to the buildup of a foulant layer on the membrane surface. During the early stages of fouling, the Nyquist plots shifted noticeably while the transmembrane pressure (TMP) showed negligible increase. If EIS could perform on-line in plant operation, it could be a sensitive monitoring tool to detect early fouling in RO membrane filtration.
•Electrical impedance spectroscopy (EIS) demonstrates in-situ fouling in RO.•Foulants, silica, BSA and their mixtures, display characteristic features when EIS data presented in Nyquist plots.•Nyquist plots shift during fouling and reveal CEOP effects.•Changes in the EIS occur ahead of changes in pressure or rejection.