Search

Abstract We demonstrated a dual-functionalization strategy of polymeric membrane with both "defensive" (adhesion resistance) and "offensive"(bacterial inactivation) efficacies via combining external-hydrophilic β-cyclodextrins (β-CDs) and bactericidal enrofloxacin (ENR) for combating biofouling. β-CDs were immobilized onto polydopamine (PDA) pre-modified membrane surface, followed by host-guest assembly of ENR. Both static adhesion tests and dynamic fouling experiments implied that the CD-modified membranes showed significantly reduced adsorption and lower water flux decline against organic foulant. The enhanced "defensive" (fouling resistance) capacity of CD-modified membrane was mainly attributed to hydrophilicity improvement. Next, antimicrobial tests demonstrated that the integration of ENR in the functional layer could improve the "offensive" (biocidal) activity of modified membrane. Conspicuous reduction in biomass and ATP content further illustrated that the PVDF/CD-ENR membranes could effectively suppress biofilm formation during dynamic cross-flow biofouling tests. Finally, flow cytometry (FCM) assessment was first combined with heterotrophic plate counts (HPC) method in the present study, implying that the antimicrobial mechanism of the dual-functional membrane lies in inhibition of bacterial breed without disrupting the cell membrane. Graphical abstract Schematic illustration of dual-functionalization on PDA-based polymeric membrane and mechanism of action. fx1 Highlights • Hydrophilic CD-modified membranes exhibited enhanced fouling resistance property. • ENR host-guest assembly in CD layer imparts outstanding antimicrobial efficacy. • PVDF/CD-ENR membranes suppress biofilm formation during cross-flow experiments. • Antimicrobial mechanism lies in bacterial inhibition without cell membrane damage. • This modification strategy is substrate-independent for organic/bio-fouling control. [ABSTRACT FROM AUTHOR]

A dual-charged composite membrane was engineered for efficient separation of both cationic and anionic molecules. Alternately charged functional layer with sandwich structure was assembled onto porous membrane via chemical-mediated polyphenol surface engineering. The surface morphology, element variation and surface charge properties of the functional layer were respectively analysed using SEM, FTIR and streaming zeta potential measurements. The as-prepared "sandwich"-type composite membrane showed preferable rejection to multiple charged dyes (99.6% Alcian blue, 99.3% Brilliant blue, 92.21% Methyl blue, 89.91% Rhodanile blue). Both Donnan repulsion by dual-charged functional layer and entrapment effect by micro electric fields contributed to the outstanding separation performance. Compared with generally needed high pressure of 4–8 bar for the current nanofiltration separation, the developed composite membrane achieved desirable rejection under a low operating pressure of 1.5 bar, as well as favorable recycling performance for long-term use. This study provides an energy-efficient membrane candidate for comprehensive separation of charged molecules in practical applications such as dye wastewater treatment. Image 1 • Polyphenol engineered membranes were designed and fabricated with dual-charged sandwich-structure. • The membrane exhibited desirable rejection towards both cationic dyes and anionic dyes. • Synergistic retention mechanism of Donnan effect and micro-electric-fields was proposed. • Energy-efficient retention of dye molecules was achieved at a low operating pressure of 1.5 bar. [ABSTRACT FROM AUTHOR]

Fabricating high-flux, low-fouling gravity-driven membranes (GDM) has proved to be an extremely challenging work. In this study, a novel tailored amphiphilic multi-arms polymer poly(propylene glycol)-silane-poly(ethylene glycol) (PPG-Si-PEG) was synthesized and blended into Polyvinylidene Fluoride (PVDF) matrix to fabricate GDM via nonsolvent induced phase separation method. The incorporation of multi-arms polymers affected phase separation and surface segregation behaviors, resulting in the formation of more porous structure, which were demonstrated by scanning electron microscopy (SEM). Moreover, the hydrophilic PEG arms in polymers were enriched onto membrane surface through surface segregation and utilized to improve the hydrophilicity of membranes, which were confirmed by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The separation and antifouling properties of the membranes were evaluated by using gravity as the driving force, employing bovine serum albumin (BSA) as the model foulant. The water flux of membranes increased from 4.6 L m−2 h−1 for the control membrane to 12.1 L m−2 h−1 for PVDF/PPG-Si-PEG∼5% membrane. The antifouling properties of modified membranes were effectively improved in comparison with that of control membrane. The flux recovery ratio, especially for PVDF/PPG-Si-PEG∼5% membrane, was up to 99.4%. This study provided a new method for antifouling modification of GDM. Image 1 • An amphiphilic multi-arms polymer PPG-Si-PEG was designed, and then synthesized. • The polymer PPG-Si-PEG contained multiple hydrophilic sites. • The polymer was blended into PVDF matrix to fabricate gravity-driven membranes. • The fabricated membrane exhibited more pores and larger cavities. • The separation and antifouling properties of membranes were markedly enhanced. [ABSTRACT FROM AUTHOR]

Abstract Cleaning effect and mechanism of peroxymonosulfate (PMS)-based oxidation technology were systematically studied in metal oxide-coated ceramic membrane (CM) cleaning process. Metal oxides (MnO 2 , Fe 2 O 3 , Co 3 O 4 , CuO and Mn 3 O 4) were evenly coated on CM surfaces via silane modification and dip-coating followed by calcination. The performance of prepared CMs was investigated by filtrating Alcian Blue 8GX dye. Flux decline extents of different metal oxide-coated CMs were greatly influenced by metal oxide hydrophilicity, and their rejection rates for dye increased by 10.2–47.6%, probably due to the enhanced adsorption or electrostatic repulsion of pollutants. PMS had better cleaning effects on metal oxide-coated CMs than virgin CM (64.0%) following the order: MnO 2 -coated CM (75.3%)> Co 3 O 4 -coated CM (73.8%)> Fe 2 O 3 -coated CM (71.2%)> Mn 3 O 4 -coated CM (70.5%)> CuO-coated CM (70.2%). This was well consistent with order of dye degradation efficiency oxidized by PMS activated with those metal oxides, indicating that degradation efficiency of foulant largely determined cleaning effect. The mechanisms were proposed and then verified that radical (O 2 •–), and non-radical (1O 2 and PMS direct oxidation) pathways simultaneously occurred, and metal oxides coated on CMs surfaces mainly promoted non-radical oxidation process. This study provides insight to better utilize metal oxides activated PMS oxidation technology for membrane cleaning and improve its cleaning efficiency for dye wastewater treatment. Graphical abstract fx1 Highlights • Metal oxide-coated CM was made via silane modification, dip-coating and calcination. • Membrane flux recovery ratios increased after cleaned with PMS. • Degradation efficiency of dye by PMS mainly determined membrane cleaning effect. • Radical and non-radical oxidation mainly accounted for membrane foulant degradation. [ABSTRACT FROM AUTHOR]

Abstract: PVDF/TiO2 hybrid microfiltration membranes with different nano-TiO2 dosage were prepared via thermally induced phase separation (TIPS) method, and dimethal-phthalate (DMP) was used as a diluent. The membranes prepared were characterized by scanning electron microscope, transmission electron microscope, X-ray diffractometer, Fourier-transform infrared spectroscopy and differential scanning calorimetry. Their properties such as pure water flux, contact angle, porosity and mechanical performances were also determined. Results showed that PVDF and PVDF/TiO2 hybrid membranes were formed by solid–liquid phase separation and had spherical crystallites structure with cells. The addition of nano-TiO2 particles to the PVDF/DMP mixtures had a strong effect on the crystallization temperature of hybrid membranes and crystallization formation in the TIPS process. The addition of the nano-TiO2 particles did not affect the type of PVDF crystal form (α phase). Nano-TiO2 particles were well distributed in PVDF matrix at the lower concentration and exist in a continuous phase and aggregated in PVDF matrix at the higher concentration. Pure water flux, contact angle, porosity, tensile strength and elongation at break first increased, then decreased with the increase of TiO2 dosage. [Copyright &y& Elsevier]