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Thin-film composite (TFC) nanofiltration (NF) and reverse osmosis (RO) membranes have been widely used to remove pharmaceutically active compounds (PhACs) from water and wastewater. However, limited information is available to present the rejection of neutral PhACs under complex water matrices. In this study, we used acetaminophen (AAP) as a representative neutral pollutant to study the effects of feedwater matrices on the rejection of neutral PhACs by NF and RO membranes. The results showed that the permeation of solutes and water through NF and RO membranes followed the classical solution-diffusion model. The corresponding permeability coefficients of AAP for the RO membrane showed good consistency, with average values ranging between (6.19-7.56) × 10 -6  μm s -1 in fresh and brackish feedwater. Meanwhile, the NF membrane exhibited stable AAP and NaCl fluxes as the applied pressure increased from 4.8 to 7.6 bar, suggesting an insignificant influence of convection on solute transport. In addition, a 10-fold increase in NaCl concentration reduced the average AAP permeability coefficient of the NF membrane by 57% (i.e. from 2.8 × 10 -5  m s -1 to 1.2 × 10 -5  m s -1 ), highlighting the relevance of co-existing ions to AAP transport. Furthermore, organic fouling resulted in enhanced AAP rejection by both NF and RO membranes at neutral pH level and medium applied pressure (i.e. 5.8 bar). Overall, this study provided important insights into the separation mechanism of TFC membranes for neutral PhACs, as well as the complex effects of the water matrix on the solute permeation processes., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Ferric hydrate has been extensively applied for the removal of various types of pollutants from wastewater because of its low cost and high efficiency. However, its wide-scale application has been greatly restricted by high-dose and low-adsorption capacity. Therefore, a novel Ca-doped ferrihydrite adsorbent has been synthesized and used for the enhanced removal of fluoride from wastewater in the presence of other co-existing ions. At 5 mg/L initial fluoride concentration and pH 5, the removal efficiency of fluoride approached to 97.5% and remained stable. Similarly, with the increase of dose from 100 to 300 mg/L, the fluoride removal linearly increased to 98% and remained plateau at neutral pH. Also, the presence of co-existing ions such as NO 3 - , SO 4 2- , Cl - , and natural organic matter has not significantly influenced the removal performance of the adsorbent. Fluoride removal best fit the pseudo-second-order reaction kinetics and Langmuir isotherm model. The prepared adsorbent exhibited a maximum adsorption capacity of 53.21 mg/g for fluoride uptake from water. The SEM-EDX confirmed the doping of Ca onto the ferrihydrite where the elemental peaks of Ca and Fe emerged at the energy value of about 3.6 Kev and 7.1 Kev respectively in EDX analysis. In addition, SEM results of Ca-doped ferrihydrite adsorbent illustrated that a large microplates type of products was acquired after synthesis. The regeneration results confirmed that adsorbent could retain their original adsorption capacity after five regeneration cycles. The current study suggested that Ca-doped ferrihydrite has the application potential for the enhanced adsorption of fluoride from the water phase., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

[Display omitted] • GO-based membranes have attracted substantial attention in separation processes. • The dye rejection performance of the GO membranes is critically evaluated. • The membrane stability performance and mechanisms of dye rejection are described in detail. • Technological hurdles are underscored while proposing avenues for future research. In the realm of water treatment, the utilization of two-dimensional (2D) graphene and its derivative, graphene oxide (GO), has emerged as a pioneering avenue for the development of nanoporous membranes. These membranes hold immense promise due to the remarkable attributes inherent to GO, notably its expansive specific surface area and the profusion of oxygen-containing surface functional groups. This comprehensive review elucidates the recent advances in the fabrication and utilization of GO-based membranes, specifically tailored for the efficacious removal of dyes from aqueous environments. A detailed analysis of the key physicochemical characteristics, which distinctly influence the synthesis and performance of GO-based membranes, is performed. Furthermore, a profound explication of the intricate mechanisms underpinning the rejection of dyes by these membranes is presented, accompanied by a thorough investigation into the stability performance of the deployed GO-based membranes. A quick comparison of GO membranes with other 2D materials and the application potential of these membranes in treating real textile effluents is also provided. In the end, salient research gaps are pinpointed, leading to clear suggestions for overcoming the mentioned hurdles. This article aimed to help the research community understand GO-based membranes deeply, and also provide valuable ideas about their growing effectiveness in cleaning dyes from various wastewater sources. [ABSTRACT FROM AUTHOR]

The graphene oxide (GO)-based membranes have demonstrated exceptional potential in effectively rejecting and separating various contaminants from aqueous solutions. The abundant availability of oxygenated functional groups and the high surface area of GO make it an ideal choice for synthesizing composite membranes used in water purification. This review critically examines recent advancements in the synthesis of GO-based membranes and their applications in water treatment, specifically focusing on the removal of hazardous dyes, pharmaceuticals and personal care products (PPCPs), toxic heavy metal ions, as well as the separation of oil/water (O/W) emulsions. The rejection and separation mechanisms of these contaminants and pollutants are also discussed. The desalination potential, stability performance and applications of GO membranes in treating real wastewater are meticulously assessed. Furthermore, the review highlights the potential toxic environmental impacts of GO-based materials. The key technological challenges are identified and the roadmap, comprising prospects and recommendations for future research is provided. This review article will be beneficial for researchers and professionals in the field of water treatment and material science and engineering. [Display omitted] • The potential of GO membranes in water purification has been notably showcased. • The synthesis and utilization of GO membranes in water treatment are critically assessed. • Research concerning the actual treatment of wastewater using GO membranes remains limited. • Key technological challenges are identified, and recommendations for future research are provided. [ABSTRACT FROM AUTHOR]

• The selective removal of Sr2+ and Cs+ by P-MWCNT membranes were studied. • The P-MWCNT membrane showed superb selectivity to Sr2+ over other metal ions. • The selectivity of Cs+ was depressed by the presence of coexisted metal ions. • The selectivity of divalent cations resulted from inner-sphere complexation. • While the selectivity of monovalent cations resulted from electrostatic interactions. The need for high-performance and novel technologies for selective treatment of radionuclides in water has recently stimulated broad research. In this study, we examined the ability of carbon nanotube (CNT) membranes in selective removal of strontium (Sr2+) and cesium (Cs+) from water and wastewater. In single-metal systems that contained only Sr2+, Cs+ or their competitive metal ions, the distribution coefficients (K d) of functionalized CNT membranes for divalent cations, i.e., Sr2+, Ca2+, and Mg2+, were measured as 4.41 mmol g−1, 2.14 mmol g−1, and 1.30 mmol g−1, respectively, and those for monovalent cations, i.e., Cs+, K+ and Na+, were 0.81 mmol g−1, 0.79 mmol g−1, and 0.81 mmol g−1, respectively. When Cs+ or Sr2+ co-existed with a competing cation, both pristine and functionalized CNT membranes showed excellent selectivity to Sr2+ over Mg2+ and Ca2+ while their selectivity to Cs+ over K+ and Na+ diminished. Moreover, the CNT membranes remained their selectivity for Sr2+ in a wastewater effluent despite the complex water composition. Overall, the selectivity sequence of the CNT membranes for divalent cations support the occurrence of inner-sphere complexation on CNT surfaces, while that for the monovalent cations was probably determined by electrostatic interactions. This study demonstrates that Ar/O 2 plasma treatment is a greener technology for the production of CNT functionalized membranes for selective removal of contaminants from water to achieve "fit-for-purpose" treatment. [ABSTRACT FROM AUTHOR]