Application of nanoscale probes for the evaluation of the integrity of ultrafiltration membranes

Gitis, Vitaly; Haught, Roy C.; Clark, Robert M.; Gun, Jenny; Lev, Ovadia

doi:10.1016/j.memsci.2005.09.055

Cited by 56 publications

(28 citation statements)

References 22 publications

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“…7). We have previously reported, partial disintegration of CA membranes treated with hypochlorite, as shown by ATR-FTIR spectra, SEM micrographs, and the increased pore size of the active layer of the membrane [24]. These microscopic observations can be correlated with changes in macroscopic parameters, such as ultimate tensile strength and Young's modulus.…”

Section: Resultsmentioning

confidence: 76%

“…The ATR-FTIR spectrum of a pristine CA membrane, depicted on Fig. 6, exhibited the following characteristic intense bands: 1,760 cm À1 for O-C-O vibrations, 1,630 cm À1 for O-H vibrations, 1,440 cm À1 for CH 2 symmetric vibrations, 1,340 cm À1 for C-H vibrations, 1,230 cm À1 for C-O vibrations, and 1,050 cm À1 for C-C vibrations [24]. The intensities of the peak at 1,760 cm À1 decreased with hypochlorite dosage from 1.2 for the pristine membrane, through 0.2 for the membrane treated with 5 g h/L NaOCl, to 0 for the membrane treated with 18 g h/ L hypochlorite.…”

Section: Resultsmentioning

confidence: 99%

“…Similar trends were observed for the peaks at 1,440 cm À1 (0.1, 0.05, 0) and at 1,230 cm À1 (1.3, 0.2, 0.05). Since these three bands were attributed to O-C-O, C-O and CH degradation vibrations, it is reasonable to assume that possible pathways of cellulose oxidation include formation of various end groups, such as carboxyl COOH, aldehyde -CHO, and ketone C=O groups, respectively [24].…”

Section: Resultsmentioning

confidence: 99%

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Hypochlorite Cleaning Causes Degradation of Polymer Membranes

Arkhangelsky

Kuzmenko

Gitis³

et al. 2007

Tribol Lett

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Polymer membranes are often used in water treatment industry, as a reliable economic solution for purification of surface water streams. Among a variety of membrane processes the ultrafiltration (UF) membranes combine high pathogen removal ability with minimal energy consumption. Since the membranes are considered to be chemically and mechanically stable, in-place cleaning is routinely performed with strong oxidizing agents, such as hypochlorite. The results of the current study, however, clearly indicate that the mechanical strength of UF membranes deteriorates upon hypochlorite cleaning. Values of ultimate tensile strength, ultimate elongation and Young's modulus decreased as the dose (concentration · contact time) of hypochlorite was increased, with the decreases being more marked for cellulose acetate membranes than for polyethersulfone membranes. Scanning probe microscopy showed membrane aging in response to hypochlorite treatment. The aging was related to gradual chain breaking in membrane skin layer, as reflected by the disappearance of O-C-O and C-S absorbance peaks in ATR-FTIR spectra of treated cellulose acetate and polyethersulfone membranes, respectively. Since the degree of scission was linearly related to the deterioration in ultimate tensile strength, we here propose that ultimate tensile strength measurements can be used as a simple macroscopic test for periodic inspection of the degree of degradation of UF membranes exposed to in-place chemical cleaning.

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Hypochlorite Cleaning Causes Degradation of Polymer Membranes

Arkhangelsky

Kuzmenko

Gitis³

et al. 2007

Tribol Lett

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show abstract

“…Some preliminary data on the chlorine-unstable polymers such as cellulose acetate [21,22] cannot be extended to polymers such as PES and PVDF [7]. In latter the changes in the membrane characteristics can be attributed to the membrane preservatives that are washed out gradually after the chemical cleaning.…”

Section: Discussionmentioning

confidence: 99%

“…The boosting protein fouling [17] of intensively cleaned membranes is governed by hydrophilic nature of proteins. On the operational level, the NaOCl cleaning with aggregate free chlorine doses of 5 g/(l h) and higher increases surface charge [21,22] and affects the membrane hydrophilicity. An increase in the permeate flux over the initial values can be viewed as a worrying sign that points on changes in membrane structure and increased fouling potential.…”

Section: Introductionmentioning

confidence: 99%