Effect of time delay after alkaline cleaning treatment on the properties of polyelectrolyte-coated end-of-life polyamide membranes

End-of-life (EoL) reverse osmosis (RO) membranes were regenerated by an extended alkaline cleaning treatment (ACT) followed by polyelectrolyte (PE) deposition (coating). The effect of time delay between the ACT and PE coating on the membranes’ stability and filtration properties was investigated. The permeance of the membranes increased more than twofold compared to the value exhibited by the EoL membrane before the ACT. Additionally, the surface charge decreased from −45 mV to −99 mV at pH 7.7, due to the ACT. However, the ACT-induced effects were predominantly time-dependent and were partially reversed over time. When the membrane was coated with one layer of polydiallyldimethylammonium chloride (PDADMAC) immediately after the ACT, the resulting membrane had approximately 800 g/mol molecular weight cut-off (MWCO) value and 30 L/(m² h bar) pressure-corrected flux (PCF). In comparison, if the membrane was stored in deionized (DI) water for five hours between the ACT and coating, the resulting membrane had again approximately 30 L/(m² h bar) PCF but a much higher 2,900 g/mol MWCO. Furthermore, the promptly coated membranes showcased better replicability and stability during storage, in comparison to the samples that were kept in water prior to coating.