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Ultralow-pressurized ultrafiltration membrane process with low energy consumption is promising in surface water purification. However, membrane fouling and low selectivity are significant barriers for the wide application of this process. Herein, an ultrathin zwitterionic hydrogel nanolayer was in-situ grown on polysulfone ultrafiltration membrane surface through interfacially-initiated free radical polymerization. The hydrogel-modified membrane possessed improved biological fouling resistance during the dynamic filtration process (bovine serum albumin, Escherichia coli and Staphylococcus aureus), comparing with commercial polysulfone membrane. The enhanced biofouling resistance ability of zwitterionic hydrogel nanolayer was derived from the foulant repulsion of hydration shell and the bactericidal effect of quaternary ammonium, according to the results of foulant-membrane interaction energy analyses and antibacterial performances. In surface water treatment, the zwitterionic hydrogel layer inhibited biofouling and resulted in the formation of a loose and thin biofilm. In addition, the hydrogel-modified membrane possessed 22% improvement in dissolved organic carbon (DOC) removal and 134% increasement in stable water flux, compared to commercial polysulfone membrane. The in-situ grown zwitterionic hydrogel nanolayer on membrane surface offers a prospectively alternative for biofouling control in ultralow-pressurized membrane process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Understanding the influences of cations on membrane fouling was important to improve the performance of membrane filtration system, however, opposite conclusions were made in different studies. Meanwhile, although the influences of cation concentration have been studied extensively, few attentions have been paid to the cation valence. To clarify it, the effects of typical cations on membrane fouling and cleaning, as well as the related mechanisms were investigated systemically in this study. K + and Ca 2+ were chosen as the representative cations, and humic acid (HA) was chosen as the membrane foulants. The results demonstrated Ca 2+ promoted the formation of reversible fouling, meanwhile higher removal efficiency of HA could also be achieved with the assistance of filtration cake containing HA + Ca 2+ . However, K + led to the formation of more recalcitrant irreversible fouling. By comparing the concentration of cations in feed and permeate, analyzing the influence of cations on size of HA flocs, and the detailed SEM, AFM and TEM observation, it could be found that different mechanisms dominated the interaction between cations and HA. The bridging effect induced by Ca 2+ attributed to the extension of HA molecules, while the electrostatic shielding effect induced by K + led to the compression of them. Moreover, the different characteristics of hydrated Ca 2+ and K + also contributed to the different structures of foulant layers formed by HA + Ca 2+ and HA + K + . Given the abundance of K + and Ca 2+ in natural water, results of this study can provide valuable advice for practical membrane filtration process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Increasing attention has been focused on the removal of micropollutants from contaminated drinking source water. However, low rejection efficiency and membrane fouling still inhibit further application of nanofiltration membrane in this field. Interesting results were found that the residual hydrolyzed-aluminum nanoparticles from supernatant after coagulation and sedimentation strongly improved the nanofiltration performance for micropollutant removal. A simulated raw water containing humic acids, micropollutants and kaolinite clay was employed to investigate the factors of water matrix affecting the nanoparticle-enhanced nanofiltration for micropollutant removal. Results of experiments showed that these hydrolyzed-aluminum nanoparticles easily induced the aggregation of bisphenol-A (BPA) and humic acids in the supernatant. The enhancement of BPA removal was mainly attributed to the repelling interaction between the Al-BPA-DOC complexity and in situ-modified membrane surface during nanofiltration. 'This in situ surface modification by the hydrolyzed-aluminum nanoparticles improved membrane hydrophilicity, roughness and positively-charging capacity. For the treatment of River Songhua water spiked with micropollutant, the percentage removal of BPA was improved to be 88.5%, much more than the case of single nanofiltration without coagulation (60.7%). Meanwhile, the membrane fouling was reduced by 2.13 times than the case of single nanofiltration without the dynamically deposited-layer of nanoparticles. This in situ modification of nanofiltration membrane by hydrolyzed-aluminum nanoparticles achieved excellent removal efficiency for micropollutants from River Songhua water background., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The novel H 2 O 2 -MnO 2 system was developed to achieve highly efficient membrane cleaning for both fouled PVDF and PES membranes in this study. Compared with conventional chemical cleaning process in which the whole membrane module had to be soaked in highly concentrated solution of chemical reagent for long period of time, the H 2 O 2 -MnO 2 cleaning process conducting for only 5 min in 0.5 wt% H 2 O 2 solution could achieve more than 95% recovery of permeate flux and almost total removal of the irreversible foulants. More importantly, the permeate flux and filtration efficiency of the membrane could be still kept stable after 6 runs of consecutive fouling and cleaning. Based on the systematic microscopic analyses, Electron Spin Resonance (ESR), Fourier Transform Infrared Spectroscopy (FTIR), as well as the quenching experiments with different free radical scavengers, the outstanding performance of H 2 O 2 -MnO 2 system was attributed to the generation of both free radicals and abundant oxygen simultaneously, leading to the physico-chemical membrane cleaning. Conclusively, the newly developed H 2 O 2 -MnO 2 system demonstrated noteworthy advantages on efficient membrane cleaning, and exhibited highly potential for the wide application in practical water treatment process., (Copyright © 2019. Published by Elsevier Ltd.)

• PCA improved SMX removal in Fe(III)/PAA system under truly neutral pH conditions. • PCA enhanced the catalytic activity of Fe(III) on PAA under neutral pH conditions. • CH 3 C(O)OO-Fe(III)-PCA was proposed as the primary reactive specie for SMX removal. • PCA/Fe(III)/PAA system had strong anti-interference ability to water constituents. • PCA/Fe(III)/PAA system exhibited high SMX removal efficiency in nature waters. The practical application of the Fe-catalyzed peracetic acid (PAA) processes is seriously restricted due to the need for narrow pH working range and poor anti-interference capacity. This study demonstrates that protocatechuic acid (PCA), a natural and eco-environmental phenolic acid, significantly enhanced the removal of sulfonamide antibiotics in Fe(III)/PAA process under actually neutral pH conditions (6.0–8.0) by complexing Fe(III). With sulfamethoxazole (SMX) as the model contaminant, the pseudo-first-order rate constant of SMX elimination in PCA/Fe(III)/PAA process was 63.5 times higher than that in Fe(III)/PAA process at pH 7.0, surpassing most of the previously reported strategies-enhanced Fe-catalyzed PAA processes (i.e., picolinic acid and hydroxylamine etc.). Excluding the primary contribution of reactive species commonly found in Fe-catalyzed PAA processes (e.g., •OH, R-O•, Fe(IV)/Fe(V) and 1O 2) to SMX removal, the Fe(III)-peroxy complex intermediate (CH 3 C(O)OO-Fe(III)-PCA) was proposed as the primary reactive species in PCA/Fe(III)/PAA process. DFT theoretical calculations indicate that CH 3 C(O)OO-Fe(III)-PCA exhibited stronger oxidation potential than CH 3 C(O)OO-Fe(III), thereby enhancing SMX removal. Four potential removal pathways of SMX were proposed and the toxicity of reaction solution decreased with the removal of SMX. Furthermore, PCA/Fe(III)/PAA process exhibited strong anti-interference capacity to common natural anions (HCO 3 −, Cl−and NO 3 −) and humic acid. More importantly, the PCA/Fe(III)/PAA process demonstrated high efficiency for SMX elimination in actual samples, even at a trace Fe(III) dosage (i.e., 5 μM). Overall, this study provided a highly-efficient and eco-environmental strategy to remove sulfonamide antibiotics in Fe(III)/PAA process under actually neutral pH conditions and to strengthen its anti-interference capacity, underscoring its potential application in water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]