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Developing polyamide (PA) reverse osmosis (RO) membrane with chlorine resistance is of great significance for simplifying pretreatment processes and saving operating costs. Herein, we constructed an active layer capable of highly chlorine stability and regenerative chlorine resistance by introducing p-amino diphenylamine (p-ADA) with redox activity via a facile secondary interfacial reaction (s-IR) on PA membrane surface. The calculation of resistance-in-series model indicated that the introduction of p-ADA facilitated the increase of NaCl transmembrane resistance without sacrificing membrane permeance. Chlorination experiments under acid conditions proved the protection effect of p-ADA grafted layer due to its oxidation resistance, avoiding the direct attack by free chlorine to amide bonds of polyamide membrane. By virtue of the convertible modality of the p-ADA molecule between the quinone and benzene structures during redox process, modified membranes presented the capability of regenerative chlorine resistance. After the "chlorination-reduction" cycle experiments, the normalized flux of modified membranes remained 0.522 while contrasted PA membranes showed a flux of 0.278; and the corresponding normalized NaCl rejection of modified membranes maintained at 0.998 significantly higher than that of PA membranes (0.963). This study presents a straightforward and efficient approach to enhance the chlorine resistance of PA RO membranes. [Display omitted] • p-ADA was adopted to modify the PA RO membrane by a secondary interfacial reaction. • The grafted p-ADA could cover and heal the defects of the PA membrane. • The modified membranes showed improved chlorine resistance with a higher salt rejection. • The redox feature of p-ADA molecules endowed the modified membranes with regenerative chlorine resistance. [ABSTRACT FROM AUTHOR]

Diversified ion-selective separation applications have dramatically incentivized the exploitation and performance modulation of highly ion-selective nanofiltration (NF) membranes. However, the ion selectivity of NF membranes is synergistically governed by multi-scale factors of membrane structural parameters and operational parameters, with the intrinsic ion-selective mechanism still ambiguous. Herein, we proposed an ensemble machine learning (ML) method to decouple key factors affecting the ionic selectivity of polyamide NF membranes. Membrane structural parameters and operational parameters were typically extracted as input variables and linked to mono−/divalent ion selectivity by model training based on Random Forest and XGBoost algorithms. The feature importance assessment indicated the critical role of membrane structure parameters on ion selectivity, wherein pore radius dominated the mono−/divalent anionic selectivity while zeta potential for mono−/divalent cationic selectivity. Partial dependence analyses further depicted intensive insights regarding the influence of membrane structural parameters on ion selectivity. Moreover, stochastic dataset splitting measurements demonstrated the accurate predictive capability of the model simultaneously possessing excellent stability and reliability. We anticipated that the implementation of ensemble ML in explicating the intricate ion-selective mechanism created platforms for understanding the structure-membrane performance correlation and orientally manufacturing highly ion-selective NF membranes. [Display omitted] • Ensemble machine learning was implemented to decouple the key features affecting ion selectivities of polyamide membranes. • RF and XGBoost algorithms were adopted to learn from relevant variables and evaluate permutation features importance. • Mono-/divalent anionic selectivity was dominated by pore size while zeta potential for mono-/divalent cationic selectivity. [ABSTRACT FROM AUTHOR]

• Polyesteramide-based membrane was successfully prepared via interfacial polymerization. • The polyesteramide membrane with high free volume showed high water flux. • Acid and alkali stabilities of polyesteramide membranes were obtained. A novel aromatic polyesteramide-based membrane with high free volume for water desalination was prepared by adding a rigid cardo-contorted biphenol monomer to the aqueous phase solution of m-phenylenediamine (MPD) and then carrying out the interfacial polymerization. Compared with the polyamide (PA) membrane, the polyesteramide membrane with high free volume and ultrathin separating layer exhibited 250% increase in flux and 1.2% loss in salt rejection. Moreover, acid and alkali stabilities of polyesteramide membranes were studied by immersing the polyesteramide membranes into acid, aid/ethyl alcohol (EA), alkali and alkali/EA aqueous solutions. After acid/alkali treatments, the surface contact angles of acid/alkali-treated PA/9,9-bis(4-hydroxyphenyl)fluorine (PA/BHPF) membranes were much smaller than the pristine PA/BHPF membrane. With EA, both the acid/EA-treated and alkali/EA-treated polyesteramide membranes exhibited a significant increase in water flux; moreover, the acid/EA-treated membranes showed a simultaneous increase in water flux and salt rejection within a treatment time of 24 h, due to the increase in hydrophilicity and the partial dissolution of small polymer fragments on membrane surface. [ABSTRACT FROM AUTHOR]