Flux Recovery Rate Research Articles

Multifunctional Bacterial Cellulose/Covalent Organic Framework Composite Membranes with Antifouling and Antibacterial Properties for Dye Separation.

Covalent organic frameworks (COFs) have a wide application prospect in wastewater treatment because of their unique structure and properties; however, the preparation of pure COF membranes remains a great challenge by reason of the insolubility and unprocessability of COF powders formed at high temperature and high pressure. In this study, a continuous and defect-free bacterial cellulose/covalent organic framework composite membrane was prepared by using bacterial cellulose (BC) and a porphyrin-based COF with their unique structures and hydrogen bonding forces. The dye rejection rate of this composite membrane toward methyl green and congo red was up to 99%, and the permeance was about 195 L m-2 h-1 bar-1. It showed excellent stability under different pH conditions, long-time filtration, and cyclic experimental conditions. In addition, the hydrophilicity and surface negativity of the BC/COF composite membrane made it have certain antifouling performance, and the flux recovery rate can reach 93.72%. More importantly, the composite membrane exhibited excellent antibacterial properties due to the doping of the porphyrin-based COF, and the survival rates of both Escherichia coli and Staphylococcus aureus were less than 1% after exposure to visible light. The self-supporting BC/COF composite membrane synthesized by this strategy also has outstanding antifouling and antibacterial properties, in addition to excellent dye separation effects, which greatly broaden the application of COF materials in water treatment.

The peroxidase-like cleaning strategy for organic fouling of water treatment membranes based on MoS2 functional layers

Efficient cleaning strategies play a key role in implementing sustainable and economic membrane operations during water treatments and purification. We proposed in this paper to construct the functional layers on the surface of PES substate using MoS2 nanosheets synthesized by a hydrothermal method, namely MoS2/PES membrane. The membrane structure and properties were characterized by SEM, XRD, EDS and FTIR. This is then followed by an evaluation of the membrane fouling of the functional layers, and in turn exploring the membrane cleaning strategy. The specific catalytic effects between MoS2 nanosheets with peroxidase-like activity, and the cleaning agent (H2O2) was subtly combined to endow MoS2 functional layers with specific catalysis. Humic acid (HA, as a representative organic foulant) having the filtration efficiency (~91 %) of MoS2/PES membrane was ~6 % higher than that of the pristine PES membrane. The flux recovery rate of MoS2/PES membrane (~75 %) was significantly larger than the PES membrane (~16 %) under optimized conditions. Results of 7 cycles of consecutive membrane fouling and cleaning demonstrated MoS2 functional layers not only relieved membrane fouling but also exhibited higher water flux. The outstanding performance of MoS2 functional layers could be explained by their stacked honeycomb pore-like structure and the catalytic characteristics of MoS2-like peroxidases. H2O2 was used to trigger the in-situ catalytic function of MoS2 layers, generating strong ROS and oxygen for the enhanced removal of organic foulants. This study provides new insights into devising a novel membrane cleaning strategy using advanced functional nanomaterials.

Improvement of persistent hydrophilicity and pore uniformity of polyvinyl chloride ultrafiltration membranes by in-situ crosslinking reaction assisted phase separation

A novel in-situ crosslinking reaction assisted phase separation strategy was proposed for persistent hydrophilization and pore size regulation of polyvinyl chloride (PVC) membranes. In-situ cross-linking between PVC molecular chains was achieved through grafting of 3-aminopropyltrimethoxysilane (APTMS) during the dissolution process and cross-linking reactions between siloxanes in APTMS molecules initiated by the coagulation bath (water). The effect of in-situ crosslinking reaction on the structure, separation and anti-fouling performance of the PVC membranes was studied. Through in-situ crosslinking reaction induced phase separation, the migration and curing of polymer molecular chains in the phase separation process were regulated, which endowed the modified membrane with improved hydrophilicity, higher porosity and narrow pore size distribution. The pure water flux of the obtained membrane increased 3.5 times as much as that of the pure PVC membrane. In addition, the flux recovery rate (FRR) of the obtained membrane was increased by 15.9% and the strength was also increased slightly at the same time. The stability of the membranes was also improved, without chemical agents leaching during filtration, avoiding secondary pollution to our environment.

Antifouling polymeric nanocomposite membrane based on interfacial polymerization of polyamide enhanced with green TiO2nanoparticles for water desalination

In the present investigation, the preparation and characterization of polyamide/TiO2as thin film nanocomposites (TFN) for brackish water desalination was investigated. TiO2nanoparticles (NPs) were synthesized by a green method using thyme plant extract as a reducing and capping agent. The TiO2NPs was successfully prepared in pure crystalline anatase phase with 15 nm size, and −33.1 mV zeta potential. The antimicrobial tests confirmed the antimicrobial activity of TiO2against gram-positive and gram-negative bacteria. In addition, TiO2NPs showed a good photocatalytic activity in degradation of methylene blue dye. TFN based on interfacial polymerization was enhanced by embedding 5% of the greenly synthesized TiO2NPs within the polyamide thin film active layer. The incorporation of TiO2NPs was confirmed by SEM, atomic force microscope (AFM), surface wettability, and FTIR. Membranes performance was investigated based on flux, salt rejection and fouling resistance. The antifouling was examined using bovine serum albumin (BSA) as protein fouling by dead-end cell filtration system at 2 bar. The results showed the TFN increased in water flux by 40.9% and a slight decrease in NaCl rejection (6.3%) was observed, with enhancement in antifouling properties. The flux recovery rate of the modified TFN membranes after fouling with BSA solution was enhanced by 21.5% (from 61.7% for TFC to 83.2% for TFN). Also, they demonstrated remarkable anti-biofouling behavior against both bacterial strains.

A solar-driven degradation-evaporation strategy for membrane self-cleaning in the efficient separation of viscous crude oil/water emulsions

Membrane separation techniques are promising methods for effectively treating hazardous emulsified oily wastewater, but membrane fouling remains a serious challenge because the high viscosity and complex composition of crude oil make it easy to adhere to membranes and difficult to be removed by conventional physical or chemical cleaning means. Herein, a two-stage solar-driven (photo-Fenton degradation/evaporation) strategy was proposed to realize the self-cleaning of membranes fouled by viscous crude oil (>60,000 mPa s), wherein the photo-Fenton process helped to degrade the heavy components into light components, and all light components removed during the solar-driven evaporation process. A 1D/2D heterostructure membrane with photo-Fenton activity and anti-crude-oil-fouling performance was prepared via a facile self-assembly vacuum-assist method. The addition of rod-like g-C3N4 (RCN) increased the interlayer distance of α-FeOOH/porous g-C3N4 (FPCN) nanosheets, resulting in a high permeation flux. The FPCN–RCN membrane exhibited both high permeation flux of 779 ± 19 L m–2h–1bar–1 and a separation efficiency of 99.4% for highly viscous crude oil-in-water emulsion. Importantly, the viscous crude oil fouled on the membrane was completely removed by the photo-Fenton degradation/solar-driven evaporation strategy, and the flux recovery rate of the membrane was ∼100%. Therefore, the FPCN–RCN membrane combined with the novel self-cleaning strategy exhibits great potential for practical emulsified oily wastewater treatment.

Self-protecting PVDF-PDA-TiO2 membranes towards highly efficient and prolonged dye wastewater treatment by photocatalytic membranes

The photocatalytic membranes have been reported to treat textile dye effluents; however, it is challenging to maintain their long-term functionality due to the poor binding stability of nanoparticles on the membrane surface and the low stability of the membrane to UV radiation. To address this, PVDF photocatalytic hollow fiber membranes were prepared by coating with polydopamine (PDA) for 1–4 h, then with titanium dioxide nanoparticles (TiO2) in the current study. SEM and EDX results showed that TiO2 adhered firmly to the PDA-pretreated membrane after ultrasonic treatment. The PDA layer protected the membranes from UV irradiation. The PVDF-TiO2 membrane without PDA pretreatment was destroyed after 24 h of UV irradiation, while after 9 days of continuous irradiation, the membranes treated with PDA for 2 h remained unchanged. Compared with the original membrane, applying PVDF membranes coated with PDA for 2 h and TiO2 for 1 h increased the Reactive Red 239 rejection and flux recovery rates by 13% and 40%, respectively, achieving 60% COD removal. The permeate flux and dye rejection rate were stable after 5 cycles (20 h of operation). This study demonstrates that the obtained membranes can perform prolonged membrane filtration with high-performance durability for dye wastewater treatment.

High-Flux lamellar MoSe2 membranes for efficient dye/salt separation

Membrane-based technology is emerging as an efficient technique for wastewater treatment in recent years. Membranes made up of two-dimensional materials provide high selectivity and water flux compared to conventional polymeric membranes. Herein, we report the synthesis and use of MoSe2 membrane for dye and drug separation in wastewater, mainly from textile and pharmaceutical industries. The as-prepared MoSe2 membrane shows ∼ 100% rejection for organic dyes and ciprofloxacin drug with a water flux reaching up to ∼ 900 Lm-2h-1bar-1. Further, the MoSe2 membrane shows lower NaCl rejection of ∼ 1.9% for the dye/salt mixture. The interlayer spacing in the MoSe2 membrane allows the water molecules and ions from the salt to pass through freely but restricts the movement of large contaminants. The membrane is stable against the bovine albumin serum fouling with a flux recovery rate of 96%. It also shows good performance even in harsh environments (pH 3–10). To the best of our knowledge, the MoSe2 membranes were fabricated for the first time for wastewater treatment application. The dye/salt separation performance of the MoSe2 membrane is significantly better than several other membranes. This work highlights the promising potential for using two-dimensional materials for textile and pharmaceutical wastewater treatment.

A facile strategy to develop highly stable antifouling NF membranes with chlorine resistance based on polyamide-sulfonamide active layer

In practical applications, Nanofiltration (NF) membranes are confronted with inevitable challenges, including the terrible fouling and the deterioration by chlorine, which hinders the wider application. In this study, 2-aminophenol-4-sulfonamide (APSA) was incorporated to form the polyamide-sulfonamide active layer, thus highly stable antifouling NF membranes with chlorine resistance were fabricated. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results showed APSA successfully grafted on the membrane surface. Scanning electron microscope (SEM) and atomic force microscope (AFM) images indicated a smooth membrane surface. Water contact angle of the PA-SA NF membranes declined to 19.7° compared with the PA NF membranes. Flux recovery rates (FRR) of bovine albumin (BSA), humic acid (HA), sodium alginate (SA) and oil/water emulsion were 96.4%, 96.8%, 96.0% and 94.6%, respectively. Besides, slight decline occurred to FRR value for BSA after three fouling cycles. No obvious decline of the rejection and water flux was observed on long-term stability. Notably, slight rejection rate decline and no obvious FRR value decline were observed after chlorination. Overall, the PA-SA NF membranes possessed highly stable antifouling property and chlorine resistance. It might be due to the fact that APSA including various hydrophilic groups grafted onto the active layer. N–H bonds of sulfonamide could act as a sacrificial unit against free chlorine. It is anticipated that this work could provide a facile strategy to develop NF membranes with highly stable antifouling property and chlorine resistance.

Mechanistic insight into developing a novel loose nanofiltration membrane for effective dye/salt separation by epigallocatechin gallate

Loose nanofiltration (LNF) membrane prepared by hydroxyl-based materials with excellent separation and antifouling properties has attracted great attention for treating textile wastewater. However, the construction and formation mechanism of the selective layer by using large polyphenol-based monomers was not well studied. Herein, a novel LNF membrane was fabricated by interfacial polymerization, in which a polyphenol named epigallocatechin gallate (EGCG) was employed as aqueous monomer to design the selective layer. The results illustrated that the formed polyester (PE) selective layer possessed a loose structure with smooth and hydrophilic surface. Notably, the EGCG with large molecular volume and polyphenol groups contributed to the larger molecular weight cut-off (MWCO) and hydrophilic PE layer with high permeability, whereas the small molecular trimesoyl chloride (TMC) accounted for the pore size reduction with low permeance. More importantly, the optimized EGCG-based LNF-4 membrane displayed a high water permeability of 41.7 LMH·bar−1, high rejection of dyes (98.5 % for Congo Red (CR), 93.4 % for Methyl Blue (MB), and 94.8 % for Evans Blue (EB), respectively) and low rejection of salt (7.4 % for NaCl). Besides, under 60 g/L salt content, a high retention of CR (93.0 %) and high permeation of NaCl (95.1 %) could be still maintained. Furthermore, the LNF-4 membrane had a superior fouling resistance towards CR and EB with flux recovery rate above 96.4 %. The excellent antibacterial property also made LNF-4 more competitive in practical applications. This work can provide a new strategy for fabrication of outstanding multifunctional LNF membranes by large molecular polyphenol monomers.

Base-activated persulfate strategy for ceramic membrane cleaning after treatment of natural surface water

The natural organic matters (NOM) have been proved to form the hydraulically irreversible membrane fouling, which limit the application of the membrane in water treatment processes. To solve the membrane fouling caused by NOM, a novel one-step chemical cleaning method for the ceramic membrane derived from the base-activated persulfate oxidation process was developed in this study. When the SiC ceramic membranes was used to filtrate practical river water, the permeate flux dropped 65% as ΔTMP reached 30 kPa. After 2 h immersion of the fouled membrane in the cleaning solution (2 mM PMS and 8 mM NaOH), the flux recovery rate nearly reached 100%. Direct backwash of the membrane by the above cleaning solution further reduced the cleaning time to 25 mins, while achieving similar cleaning effect. Then the cleaned membranes were immersed in NaClO solution to release all the residual foulants, but the fluorescence excitation-emission matrix spectra (EEM) and total organic carbon (TOC) of the solution were found insignificant, which demonstrated the base-activated persulfate strategy had effectively removed the irreversible membrane fouling. Free radical quenching experiments were carried out and·O2- was identified as the dominant ROS responsible for the removal of the membrane foulants. The permeate flux and filtration efficiency of the SiC membrane were stable after 5 consecutive fouling-cleaning cycles, and the membrane structure was not damaged. In summary, the base-activated persulfate strategy is an efficient and cleaner method for SiC membrane cleaning, which is potential to be applied in practical membrane water treatment process.

Antifouling nanofiltration membrane atop nanofibrous scaffold with periodical diagonal microprotrusion

Tuning the surface structure and roughness of selective layer is effective but a challenge to enhance the permeance and antifouling performance of nanofiltration membrane without sacrificing selectivity. In this work, we developed a novel method to engineer an aromatic polyamides (PA) selective layer atop nanofibrous scaffold with periodical diagonal microprotrusion, which inherits from the morphology of twill fabric. The hydrophilic nanofiber layer presents a compact feature (pore size: 100–300 nm) and high conformality towards the fabric support with twill morphology beneficial to the IP process. The generated PA nanofiltration membrane presented a hierarchical surface structure involving periodical diagonal microprotrusion (around 85 μm cell distance) and ridge-valley structure (∼100 nm). The resultant membrane exhibited not only a high permeance of 31.7 L m−2 h−1 bar−1 and a rejection rate of 97.5% to Na2SO4 solution, but also ameliorated antifouling performance with a high flux recovery rate larger than 96.5% in five filtration-washing tests. This is attributed to the synergistic effects between highly porous nanofiber scaffold and the eddy self-cleaning function derived from periodical diagonal microprotrusion of the fabric supported by the numerical simulation study. This work presents the superiority in designing high permeable membranes with excellent antifouling performance for advanced nanofiltration application.

Fabrication and characterization of dual-layer hollow fiber membranes incorporating poly(citric acid) grafted GO with enhanced antifouling property for water treatment

ABSTRACT Membrane fouling which occurs during filtration process is a perennial issue and could lead to reduced separation efficiency. In this work, poly(citric acid) grafted graphene oxide (PGO) was respectively incorporated into matrix of single-layer hollow fiber (SLHF) and duallayer hollow fiber (DLHF) membranes, aiming to improve membrane antifouling properties during water treatment. Different loading of PGO ranging from 0 to 1 wt% was first introduced into the SLHF in order to identify the best PGO loading for the DLHF preparation with its outer layer modified by nanomaterials. The findings showed that at the optimized PGO loading of 0.7 wt%, the resultant SLHF membrane could achieve both higher water permeability and bovine serum albumin rejection compared to the neat SLHF membrane. This is owing to the improved surface hydrophilicity and increased structural porosity upon the incorporation of optimized PGO loading. When 0.7 wt% PGO was introduced only to the outer layer of DLHF, the cross-sectional matrix of the membrane was altered, forming microvoids and spongy-like structure (more porous). Nevertheless, the BSA rejection of the membrane was improved to 97.7% owing to the presence of inner selectivity layer that was produced from different dope solution (without PGO addition). The DLHF membrane also demonstrated significantly higher antifouling properties compared to the neat SLHF membrane. Its flux recovery rate is 85%, i.e., 37% better than that of neat membrane. By incorporating hydrophilic PGO into the membrane, the interaction of the hydrophobic foulants with the membrane surface is greatly reduced.

The antifouling and separation performance of an ultrafiltration membrane derived from a novel amphiphilic copolymer containing a crown ether

Amphiphilic copolymers have attracted extensive attention for the preparation of ultrafiltration (UF) membranes processed with high separation and antifouling performances. Herein, hydrophilic crown ether (dibenzo-18-crown-6-ether, DE) units were introduced into poly(p-terphenyl, isatin) (PDTI) based on a polycondensation reaction via superacid-catalysis. The copolymers showed good thermal stability and membrane-forming properties, and the UF membranes fabricated by NIPS exhibited excellent separation performance. The content of the hydrophilic DE significantly influenced the morphology structure of the UF membranes. The cross-section structure of the membranes gradually converted from finger-like pores to loose sponge pores during delayed phase separation. The water flux of membranes ascended from 130.9 LMH bar−1 to 286.6 LMH bar−1 while the BSA rejection rate decreased from 99.4% to 90.8% as the DE content increased from 10% to 30%. These changes were associated with an enhanced surface porosity, larger surface pore diameter, and thinner top layer. Moreover, increasing the DE content in the copolymer greatly improved the antifouling performance due to greater hydrophilicity. Upon increasing the molar ratio of DE to p-terphenyl from 1: 9 to 3: 7, the flux recovery rate of the membranes surged from 58.5% to 91.5% and remained >80.2% after three fouling-cleaning cycles. In addition, the surface segregation of the hydrophilic DE segment in the copolymer was confirmed by the higher oxygen element content of the UF membrane on the top surface (18.62%) than that of the polymer (13.97%). Therefore, the amphiphilic copolymer containing a crown ether synthesized by a one-pot polycondensation reaction provides an effective way for the preparation and property adjustment of UF membranes.

Fabrication of Anatase TiO2/PVDF Composite Membrane for Oil-in-Water Emulsion Separation and Dye Photocatalytic Degradation

At present, the types of pollutants in wastewater are more and more complicated, however, the multifunctional membrane materials are in short supply. To prepare a membrane with both high efficient oil-in-water emulsion separation performance and photocatalytic degradation performance of organic dyes, the bifunctional separation membrane was successfully prepared by electrostatic spinning technology of PVDF/PEMA and in situ deposition of anatase TiO2 nanoparticles containing Ti3+ and oxygen vacancies (Ov). The prepared composite membrane has excellent hydrophilic properties (WCA = 15.65), underwater oleophobic properties (UOCA = 156.69), and photocatalytic performance. These composite membranes have high separation efficiency and outstanding anti-fouling performance, the oil removal efficiency reaches 98.95%, and the flux recovery rate (FRR) reaches 99.19% for soybean oil-in-water emulsion. In addition, the composite membrane has outstanding photocatalytic degradation performance, with 97% and 90.2% degradation of RhB and AG-25 under UV conditions, respectively. Several oil-in-water separation and dye degradation experiments show that the PVDF composite membrane has excellent reuse performance. Based on these results, this study opens new avenues for the preparation of multifunctional reusable membranes for the water treatment field.

The Fe3O4@UiO-66-NH2/PVDF-co-CTFE mixed matrix membrane with enhanced anti-fouling and self-cleaning performances for effectively removing dyes by Fenton reaction

It is a major obstacle to further development of membrane technology that membrane fouling occurs. In this study, a novel Fe3O4@UiO-66-NH2/PVDF-co-CTFE mixed matrix membrane was successfully developed by mixing Fe3O4@UiO-66-NH2 nanoparticles (NPs) into PVDF-co-CTFE membrane through a simple non-solvent-induced phase separation (NIPS) method, and was used for degradation of organic wastewater. The results of the incorporated Fe3O4@UiO-66-NH2 NPs content on the morphology, pore structure and physicochemical structure of samples were investigated systematically. The results indicated that the Fe3O4@UiO-66-NH2 NPs addition in membrane matrix improved the permeability and significantly enhanced the anti-fouling performance. When 2 wt% Fe3O4@UiO-66-NH2 NPs was added, the mixed matrix membrane had excellent comprehensive performance, maintaining a high pure water flux of 226.8 L m−2 h−1, the BSA rejection rate reached 95.9%, and the flux recovery rate was 71.38%. Importantly, the membrane possessed high catalytic performance based on the Fenton reaction mechanism, and the removal rate of 20 mg L−1 MB solution (400 mL) was up to 99.04%, and showed excellent self-cleaning characteristics and long-term stability. In conclusion, this study provided a new idea for the development of Fenton catalytic membranes with excellent anti-fouling performance for wastewater treatment in complex environments.

A TiO2 modified whisker mullite hollow fiber ceramic membrane for high-efficiency oil/water emulsions separation

Design and preparation of membranes with ultrahigh separation performance and antifouling property for oil-in-water (O/W) emulsions remains challenging. In this study, a high flux mullite/TiO2 ceramic composite membrane was prepared via multi-precipitation of TiO2 on a whisker mullite hollow fiber support synthesized by combining phase inversion and high-temperature sintering techniques. The results showed that the generated whisker mullite structure improved the permeation flux, and the micro-nano structured TiO2 functional layer endowed the membrane surface with superhydrophility and stability. The retention of the optimal composite membrane (M20T13) that was soaked in the titanium solution 20 times for 13 min each time for the O/W emulsions like n-hexane, toluene and engine oil maintained over 98 %, and the flux after 6 h filtration was 668.34 L·m−2·h−1, 487.25 L·m−2·h−1 and 258.66 L·m−2·h−1, respectively, much higher than that of the optimal substrate (F3A1, mass ratio of fly ash: Al2O3 = 3:1). Moreover, the flux recovery rate of M20T13 was much higher than that of F3A1 after chemical backwashing. This work manifests great potential in O/W treatment fields.

Polyethersulfone membrane modified by zwitterionic groups for improving anti-fouling and antibacterial properties

Ultrafiltration (UF) membranes are commonly confronted with threats from pollutants during long-term operation. The zwitterions with high hydrophilicity are expected to be the critical material to improve the anti-fouling and antibacterial abilities of membranes. Herein, a new zwitterionic polyethersulfone (PES) (zwitterionic PES - ZPES) was synthesized. The as-prepared ZPES was used to fabricate a zwitterionic UF membrane via the non-solvent induced phase inversion (NIPS) method. Zwitterionic polymer skeleton enhanced the hydrophilicity, permeability and anti-fouling properties of the material. As a result, the ZPES membrane exhibited doubled water flux growth (269.6 L·m−2·h−1) compared with that of the PES (125.3 L·m−2·h−1) and high protein rejection (98.6%). Besides, the ZPES membrane could maintain an excellent flux recovery rate (94.1%) and antibacterial effect (more than 95%). Therefore, the excellent anti-fouling and antibacterial abilities of the ZPES membrane broaden its application scope further.

Fabrication and characterization of cellulose acetate ultrafiltration membrane and its application for efficient bovine serum albumin separation

AbstractTo solve the easy contamination problem of ultrafiltration membranes during protein separation, a series of cellulose acetate (CA) ultrafiltration membranes with different pore morphology and structure were successfully prepared by combining solution casting, non‐solvent‐induced phase inversion, and pore‐forming agent leached out technologies. The effects of molecule weight and the content of porogen polyethylene glycol (PEG) on the pore morphology, chemical composition, and wettability of the CA ultrafiltration membrane were systematically studied. The feed permeability, bovine serum albumin rejection, and anti‐fouling ability were also investigated. The results showed that the CA10k membrane has the highest pure water flux of 877.5 L/m2h.bar, largest bovine serum albumin (BSA) rejection of 96.5% and flux recovery rate of 90.9% when the PEG molecule weight and content are 10 kDa and 10 wt%. Those results showed that the CA ultrafiltration membranes have great application prospects in the BSA separation area.

Nitrogen-doped carbon nanotube modified ultrafiltration membrane activating peroxymonosulfate for catalytic transformation of phosphonate and mitigation of membrane fouling

The nitrogen-doping carbon nanotube modified polyethersulfone membrane (NCNT@PES) was prepared by vacuum-assisted filtration. The catalytic activity and anti-fouling capacity of NCNT@PES/peroxymonosulfate (PMS) system were both systematically investigated. Selecting ethylenediamine tetra(methylene phosphonic acid) (EDTMP) as a target phosphonate, the NCNT@PES/PMS system degraded almost 100% of EDTMP, and about 60% of the total phosphorus (TP) in EDTMP could be transformed into orthophosphate (PO43−) within 1 min. Scavenger experiments and electron paramagnetic resonance (EPR) technique verified that the surface-bound radicals were mainly contributed the degradation and transformation of EDTMP in the NCNT@PES/PMS system. The presence of HCO3−, SO42− and NOM weakened the catalytic reactions, nevertheless, the NCNT@PES/PMS system still showed considerable effectiveness on the transformation of EDTMP in real sewage effluent. Moreover, the anti-fouling experiment proved that NCNT@PES/PMS system were superior on the removal of fluorescent components in the real sewage effluent, and their removal rates for the dissolved organic matter (DOC) and UV absorbance at 254 nm (UV254) were also improved. During the filtration cycles, the NCNT@PES/PMS system mitigated the membrane fouling significantly, which had been verified by the slower decline of normalized flux, less ultrapure water flux loss rates and higher ultrapure water flux recovery rates. This study provided a novel but simple way for effective EDTMP decontamination, at the same time, confirmed the potential of NCNT@PES membrane coupled with PMS activation on anti-fouling and water purification ability.

Plant-derived hybrid coatings as adsorption layers for uranium adsorption from seawater with high performance

It is critical for resource sustainability and environmental security to develop simple and dependable seawater uranium (VI) (U(VI)) enrichment technology. Membrane materials show excellent performance in the field of adsorption due to their pore structure and recyclability. In this study, a functional coating primarily composed of plant-derived tannic acid (TA) and polyethyleneimine was easily decorated on polyvinylidene fluoride (PVDF) microporous membranes for highly efficient uranium extraction via filtration. The synergistic effect of amino group from PEI and polyphenol structure plays an important role to achieve high adsorption capacity and rapid adsorption kinetics toward U(VI). Furthermore, the higher the molecular weight of PEI, the greater the modified membrane's adsorption capacity to U(VI). The membrane adorned with the optimized functional coating demonstrates outstanding removal rates (91%) and adsorption capacity (164.1 mg g−1 at C0 = 99.55 mg L−1) under extremely high permeate flux (11324.54 L m−2 h−1) due to its high adsorption capacity and quick adsorption kinetics. Moreover, the functional coating also possesses excellent reusability, antifouling performance, high flux recovery rate (FRR) (∼ 98%) and low flux decay rate (FDR) (<5%) after ten cycles. Particularly, the membrane's U(VI) adsorption capability in natural seawater can increase to 6.86 mg g−1. Considering the facile and mild modification process, as well as the green and low costing materials, the plant-derived hybrid coatings have a great application prospect in the field of seawater U(VI) extraction.