Long-term pilot plant study using direct chlorination for biofouling control of a chlorine-resistant polyamide reverse osmosis membrane

Manalo, Cervinia; Ohno, Masaki; Nishimoto, Sunao; Okuda, Tetsuji; Nakai, Satoshi; Nishijima, Wataru

doi:10.5004/dwt.2019.23319

Cited by 5 publications

(2 citation statements)

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“…Considering this concentration and contact time, the concentration–time of contact (CT) value for this tertiary polyamide membrane was calculated to be 9,600 ppm·h. In our previous study, the intermittent addition of NaOCl at C fc = 10 ppm for 10 min every 24 h prevented biofouling during the reverse osmosis membrane filtration of secondary treated sewage from Higashi-Hiroshima Wastewater Treatment Plant, Japan . Comparing the CT value and intermittent chlorination conditions, the tertiary polyamide membrane was expected to be useful for an operation period of 7.9 years.…”

Section: Resultsmentioning

confidence: 99%

“…In previous studies, the monomers used to synthesize conventional secondary amide membranes, such as trimesoyl chloride and m -phenylenediamine, were replaced by other monomers. , Kawaguchi and colleagues reported that tertiary amides were inert to free chlorine species according to their results using model compounds such as N -methylbenzanilide and N -phenylbenzanilide . Because of its chlorine resistance, N , N ′-dimethyl- m -phenylenediamine has been used in interfacial polymerization as an acidic chloride monomer; the resulting tertiary polyamide membrane showed excellent tolerance to free chlorine species compared to that of the conventional secondary polyamide , because of the physical protection of the chlorine-sensitive nitrogen. This tertiary polyamide membrane is ready to be produced at the commercial scale, and a recent paper reported the performance of tertiary polyamide membrane in the long-term pilot plant study using direct chlorination for biofouling control; however, its durability to deterioration by free chlorine and the related deterioration mechanisms should be studied to facilitate its practical application and further improvement.…”

Section: Introductionmentioning

confidence: 99%

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Deterioration Mechanism of a Tertiary Polyamide Reverse Osmosis Membrane by Hypochlorite

Hashiba

Nakai

Ohno

et al. 2019

Environ. Sci. Technol.

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A tertiary polyamide membrane was synthesized using N,N′-dimethyl-m-phenylenediamine. The durability of this membrane to chlorination by hypochlorite treatment followed by sodium hydroxide treatment was examined, and then deterioration mechanisms were proposed. The tertiary polyamide membrane demonstrated better durability to free chlorine than a conventional secondary polyamide one; however, the former was deteriorated by hypochlorite for 24 h at 2000 ppm of free chlorine below pH 7.5. The salt rejection and permeation performance of the membrane were almost unchanged, and the least chlorination of the active layer occurred during hypochlorite treatment at pH 10. These results indicated that hypochlorous acid rather than hypochlorite ion was the free chlorine species that induced membrane deterioration. The deterioration became severe as chlorination progressed, resulting in collapse of the active layer below pH 7.5. Chlorination and hydrolysis of the model tertiary amide N-methylbenzanilide and Fourier transfer infrared spectroscopy of a deteriorated membrane showed that chlorination of the tertiary polyamide occurred via direct chlorination of the benzene bound to the amidic nitrogen. Silver ion probing of the deteriorated membrane revealed that amide bond scission occurred in the active layer, which might be related to the electron deficiency of the amidic nitrogen caused by chlorination of its benzene ring.

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Section: Resultsmentioning

confidence: 99%