Chemical cleaning effects on properties and separation efficiency of an RO membrane

Abstract

This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3 and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron and sodium rejections are irreversible in most cases. Abstract. This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3 and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron and sodium rejections are irreversible in most cases.

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Reaction Kinetics, Mechanisms, and the Role of Chloride

“…These synthetic solutions contained 7–12 μM of BA, N- CH 3 -BA, 2,4,6-Cl 3 -BA or 2,4,6-(CH 3 ) 3 -BA at pH 4.0–9.3 in 10 mM acetate (pH 3.9–4.1), phosphate (pH 6.0–8.1), or borate buffer (pH 8.6–9.3). The pH range (pH 4–9) was selected because (i) membrane cleaning procedures involve extended acidic and alkaline conditions, , (ii) membrane degradation mechanisms and membrane properties (e.g., surface charge) are strongly affected by pH, ,,, (iii) different chlorine species dominate in this pH range (p K a (HOCl/OCl – ) = 7.5; eqs and ), and (iv) the low pH condition (e.g., pH 4) also enabled us to determine second-order reaction rates between the monomer and various chlorinating agents (see later discussions). In certain cases, various amounts of Cl – or ClO 4 – (an ionic strength control) were added (0–540 mM).…”

Quantification and modelling of organic micropollutant removal by reverse osmosis (RO) drinking water treatment

“…The low-pressure ESPA3 RO membrane displayed a net negative charge at operating feed pH (isoelectric point at pH 4 and zeta potential of − 24.8 mV at pH 9) [67,68]. The repulsion between the negative charge of the membrane and negatively charged solutes decrease the absorption and increase the removal [23,32].…”

“…a Manufacturer data.b MWCO: molecular weight cut-off; Yangali-Quintanilla et al[13]; Dach[63].c Kosutic et al[80].d Tu et al[67].…”

Influence of Chemical Cleaning on Physicochemical Characteristics and Ion Rejection by Thin Film Composite Nanofiltration Membranes

“…Several studies have addressed the impacts of different cleaning chemicals on various types of foulants, with acidic and basic cleaning solutions being most common. − However, the effects of cleaning chemicals on membrane performance have only been addressed more recently. A need for extensive research on cleaning of NF membranes ,, led to studies on the effects of chemical cleaning on the performance of NF membranes. − Interestingly, a particular cleaning chemical can have different effects on the performance of different NF membranes. For instance, Fujioka et al reported a permeability increase of 54% for the NF270 membrane with caustic cleaning at pH 12, while Tu et al reported a permeability increase of 5% with caustic cleaning with the ESPA2 membrane.…”