Potential For Water Purification Research Articles

Boosting oxygen storage capacity of Fe-Cu bimetallic catalysts through sulfide modification for efficient and selective molecular oxygen activation

Molecular oxygen (O2), a reactive oxygen species precursor, has great potential for water purification, but its spin-forbidden resistance hinders its direct involvement in the redox reactions of organic compounds under mild ambient conditions. In this study, a facile strategy was employed to synthesize sulfide-modified Fe-Cu bimetallic catalysts (FeCu-S) to enhance the activation efficiency of O2. The results showed that the FeCu-S material exhibited a tenfold increase in O2 activation compared to that of the control group, primarily attributed to the increased specific surface area of the catalysts with an optimized Fe/Cu site distribution and promoted generation of Cu-containing crystalline phases (e. g., CuFeS2 and CuO) to significantly enhanced the oxygen storage capacity. Moreover, such Cu-containing crystalline phases strengthened surface electron transfer, thus remarkably promoting the selective generation of singlet oxygen (1O2) for sulfamethoxazole (SMX) degradation. The FeCu-S/O2 system maintained high activity after the fifth recycle with stable reaction pH and negligible leaching of Cu and Fe ions, also exhibited great performance in the advanced treatment of the real biological effluent and ultrafiltration effluent from landfill leachate, confirming its great potential for practical water purification applications.

Support work-function dependent Fenton-like catalytic activity of Co single atoms for selective cobalt(IV)=O generation

In Fenton-like reactions, high-valent cobalt-oxo (CoIV=O) has attracted increasing interests due to high redox potential, long lifetime, and anti-interference properties, but its generation is hindered by the electron repulsion between the electron rich oxo- and cobalt centers. Here, we demonstrate CoIV=O generation from peroxymonosulfate (PMS) activation over cobalt single-atom catalysts (Co-SACs) using in-situ Co K-edge X-ray absorption spectra, and discern that CoIV=O generation is dependent on the support work-function (WF) due to the strong electronic metal-support interaction (EMSI). Supports with a high WF value like anatase-TiO2 facilitate the binding of PMS-terminal oxo-ligand to Co sites by extracting Co-d electrons, thus decreasing the generation barrier for the critical intermediate (Co-OOSO32−). The Co atoms anchored on anatase-TiO2 (Co-TiO2) exhibited enhanced CoIV=O generation and superior activity for sulfamethoxazole (SMX) degradation during PMS activation. The normalized steady-state concentration of CoIV=O in Co-TiO2/PMS system was three orders of magnitude higher than that of free radicals, and 1.3- to 11-fold higher than that generated in other Co-SACs/PMS systems. Co-TiO2/PMS sustained efficient removal of SMX with minimal Co2+ leaching under continuous flow operation, suggesting its attractive water purification potential. Overall, these results underscore the significance of support selection for enhanced generation of high-valent metal-oxo species and efficient PMS activation in supported metal SACs.

Nature-inspired ultrathin wood-based interfacial solar steam generators for high-efficiency water purification

Here, inspired from butterfly wing, novel hierarchical biomimetic structures composed of tunable nano-structured surfaces, rich micro/nanopores and aligned grooves from polythiophene decorated fir wood veneer have been developed to solve it. Nanowire-shaped and button-like nanostructured polythiophenes as light absorption enhanced materials were in situ grown on wood surface by adjustable vapor deposition process (PFW and CPFW). Meanwhile, wood veneer with reversed-tree structure has a unique aligned grooves surface from split tracheids, serving as the substrate for the nanostructured polythiophenes. These ultrathin wood-based solar steam generators (0.6 mm) stand as one of the thinnest reported self-floating photothermal materials based on wood. Meanwhile, high evaporation flux (1.42 and 1.48 kg·m−2·h−1) and solar-to-vapor efficiencies (88.5 % and 92.4 %) for PFW and CPFW are acquired under 1 sun irradiation. Their structure superiority boosting photothermal conversion performance has been further verified by COMSOL simulated results. The synthesized solar steam generator exhibits exceptional capabilities in seawater desalination and wastewater treatment, demonstrating fantastic application potential in water purification.

Preparation of polyethylene based composite nanofiltration membrane and its application in removal of heavy metals for water purification

The commercial polyethylene (PE) battery separator is well-suited as support for nanofiltration owing to its thickness of 7 um, high porosity, and strong mechanical properties. A new polyethylene based thin-film composite membrane was fabricated on the catechol/polyethyleneimine (CCh/PEI) modified PE support by pre-diffusion interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). By regulating the properties of the CCh/PEI layer and the PIP to influence the diffusion of PIP, a distinct worm-like structure in the polyamide (PA) layer was found, which provides more water penetration sites. After grafting melamine on the surface of PA layer, the TFC membrane exhibited outstanding chlorine resistance and the permeability of 12.5 L·m−2·h−1·bar−1 with the Mg2+ rejection of 94.5 %. Due to its small pore size, strong positively charged, and high adsorption capacity, the TFC membrane showed high rejection of heavy metal ions through pore size sieving, Donnan effect and adsorption. Therefore, it has great potential for water purification from heavy metal ions.

Sol-gel transition effect based on konjac glucomannan thermosensitive hydrogel for photo-assisted uranium extraction

Exploiting the intelligent photocatalysts capable of phase separation provides a promising solution to the removal of uranium, which is expected to solve the difficulty in separation and the poor selectivity of traditional photocatalysts in carbonate-containing uranium wastewater. In this paper, the γ-FeOOH/konjac glucomannan grafted with phenolic hydroxyl groups/poly-N-isopropylacrylamide (γ-FeOOH/KGM(Ga)/PNIPAM) thermosensitive hydrogel is proposed as the photocatalysts for extracting uranium from carbonate-containing uranium wastewater. The dynamic phase transformation is demonstrated to confirm the arbitrary transition of γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel from a dispersed state with a high specific surface area at low temperatures to a stable aggregated state at high temperatures. Notably, the γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel achieves a remarkably high rate of 92.3% in the removal of uranium from the wastewater containing carbonates and maintains the efficiency of uranium removal from uranium mine wastewater at over 90%. Relying on electron spin resonance and free radical capture experiment, we reveal the adsorption-reduction-nucleation-crystallization mechanism of uranium on γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel. Overall, this strategy provides a promising solution to treating uranium-contaminated wastewater, showing a massive potential in water purification.

Synergistic photocatalytic-photothermal contribution induced by Pd-TiO2/PEDOT immobilized in PVDF membrane for enhanced water purification

The photocatalytic membrane systems show great potential for water purification and wastewater treatment with efficient energy utilization. Herein, we develop a synergistic photocatalytic-photothermal route, based on Pd-TiO2/PEDOT composite immobilized in PVDF membrane, for effective water permeability and reutilization property. Novel Pd-TiO2/PEDOT/PVDF ultrafiltration membrane is prepared by the phase inversion method with immobilizing Pd-TiO2/PEDOT obtained by ultrasonic irradiation. During the removal of HA under light irradiation, Pd-TiO2/PEDOT/PVDF membrane presents an unexpected increasing in water flux, when compared to pristine PVDF, Pd-TiO2/PVDF and PEDOT/PVDF membranes, with the highest normalized flux reaches up to 2.1 and remains as 1.3 even after 300 min of irradiation. This significantly enhances the water transport, along with the achieved high rejection and anti-fouling performance. It can be attributed to synergistic photocatalytic-photothermal effect of Pd-TiO2/PEDOT, which is realized by their strong interaction and uniform distribution. The addition of PEDOT promotes photocatalytic effect of Pd-TiO2 by enhancing separation of photo-induced charges. High photothermal conversion efficiency of Pd-TiO2/PEDOT and low temperature difference in Pd-TiO2/PEDOT/PVDF membrane facilitate effective thermal storage, beneficial for water transport. Meanwhile, thermal energy promotes generation of more ∙OH and ∙O2– radicals to remove pollutants. Synergistic photocatalytic-photothermal contribution in Pd-TiO2/PEDOT/PVDF membrane shows significant potential for practical application.

Rod-shaped cellulose nanocrystal/Cu9S5 antibacterial nanocomposites for microfiltration

The development of high-performance antibacterial agents is crucial for controlling bacterial contamination and water purification, while the easy aggregation of the nanomaterials significantly limits their antibacterial activities. Inspired by the palygorskite nanorods' immobilization effect for nanoparticles and rod-shaped structure and surface-rich groups of cellulose nanocrystals (CNC), we in-situ grew the Cu9S5 nanoparticles on the renewable CNCs of different length/diameter ratios to fabricate cellulose nanocrystal/Cu9S5 (CNC/Cu9S5) antibacterial nanocomposites. The size of Cu9S5 nanoparticles shrank from 44 nm before compounding with CNCs to around 4 nm after in-situ growing on CNCs surface, and the obtained CNC/Cu9S5 nanocomposites with good water dispersibility showed excellent antibacterial properties (CNC-M/Cu9S5: 4.6 log reduction rate of S. aureus) by combining the physical puncture effect of CNC-M and copper ions releasing. Afterward, the antibacterial glass fiber/CNC-M/Cu9S5 microfiltration membrane was constructed by depositing the CNC-M/Cu9S5 on glass fiber microfiltration membrane, which showed high filtration flux, high retention capacity for bacteria and good bactericidal performance (>99.9% sterilization rate for S. aureus), suggesting its great potential for water purification.

A novel photocatalytic activity of Bi2S3 nanoparticles for pharmaceutical and organic pollution removal in water remediation

In recent times, there has been a surge of interest in the unique characteristics and possible applications of nanoparticles in various fields, including environmental clean-up. The contamination of water sources with pharmaceutical and organic substances has emerged as a significant environmental concern. Semiconductor nanoparticles, particularly Bi2S3 nanoparticles, have garnered considerable attention due to their efficacy and environmentally friendly nature in advanced oxidation processes (AOPs). These nanoparticles have shown remarkable photocatalytic abilities in the destruction of pollutants when exposed to UV–visible light. This study covers the production, characterization, and degradation of Bi2S3 nanoparticles in relation to organic and pharmaceutical contaminants. By utilizing co-precipitate methods, it becomes possible to precisely manipulate the size, shape, and composition of the nanoparticles, which are crucial factors in determining their catalytic effectiveness. The created nanoparticles are then examined using various analytical techniques, such as Powder X-ray Diffraction (P-XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible spectroscopy, Photoluminescence study (PL), colour chromaticity coordinates (CIE), and Dynamic light scattering study (DLS). The catalytic capability of the synthesised compounds was compared to the degradation of Picric acid and paracetamol as model pollutants. The observed photocatalytic activity of these nanoparticles indicates their potential in water purification and environmental clean-up. The findings suggest that incorporating these nanoparticles into practical systems for pollutant degradation is feasible and can be applied in diverse scenarios. The results shed light on the efficient utilization of Bi2S3 nanoparticles as photocatalysts for the oxidation of drugs and organic contaminants. By utilizing Bi2S3 nanoparticles, the elimination of pharmaceutical and organic pollutants from water sources becomes achievable, thereby contributing to the preservation and safeguarding of the environment and public health.

Selective and ultrafast oxidation of multiple pollutants by biomorphic diatomite-based catalyst and stable catalytic Fenton-like membrane: Degradation behavior and mechanism analysis

Carbon-driven advanced oxidations show great potential in water purification, but regulating structures and properties of carbon-based catalysts to achieve ultrafast Fenton-like reactions remains challenging. Herein, a biomorphic diatomite-based catalyst (BD-C) with Si–O doping was prepared using natural diatomite as silicon source and porous template. The results showed that the metal-free BD-C catalyst exhibited ultrafast oxidation performances (0.95–2.58 min−1) towards a variety of pollutants in PMS-based Fenton-like reaction, with the Fenton-like activity of metal-free catalyst comparable to metal-based catalysts or even single-atom catalysts. Pollutants (e.g., CP, BPA, TC, and PCM) with electron-donating groups exhibited extremely low PMS decomposition with overwhelmed electron transfer process (ETP), while high PMS consumption was induced by the addition of electron-withdrawing pollutants (e.g., MNZ and ATZ), which was dominated by radical oxidation. The BD-C/PMS system also showed a high ability to resist the environmental interference. In-depth theoretical investigations demonstrated that the coordination of Si–O can lower the potential barrier of PMS activation for accelerating the generation of radicals, and also promote the electron transfer from pollutants to the BD-C/PMS complexes. In addition, BD-C was deposited onto a polytetrafluoroethylene membrane (PTFEM) with 100% of pollutants removal over 10 h, thereby revealing the promising prospects of utilizing BD-C for practical applications.

Date Palm Leaflet-Derived Carbon Microspheres Activated Using Phosphoric Acid for Efficient Lead (II) Adsorption

The removal of lead metals from wastewater was carried out with carbon microspheres (CMs) prepared from date palm leaflets using a hydrothermal carbonization process (HTC). The prepared CMs were subsequently activated with phosphoric acid using the incipient wetness impregnation method. The prepared sample had a low Brunauer–Emmet–Teller (BET) surface area of 2.21 m2·g−1, which increased substantially to 808 m2·g−1 after the activation process. Various characterization techniques, such as scanning electron microscopy, BET analysis, Fourier transform infrared, and elemental analysis (CHNS), were used to evaluate the morphological structure and physico-chemical properties of the CMs before and after activation. The increase in surface area is an indicator of the activation process, which enhances the absorption properties of the material. The results demonstrated that the activated CMs had a notable adsorption capacity, with a maximum adsorption capacity of 136 mg·g−1 for lead (II) ions. This finding suggests that the activated CMs are highly effective in removing lead pollutants from water. This research underscores the promise of utilizing activated carbon materials extracted from palm leaflets as an eco-friendly method with high potential for water purification, specifically in eliminating heavy metal pollutants, particularly lead (II), contributing to sustainability through biomass reuse.

Bioinspired structural hydrogels with highly ordered hierarchical orientations by flow-induced alignment of nanofibrils

Natural structural materials often possess unique combinations of strength and toughness resulting from their complex hierarchical assembly across multiple length scales. However, engineering such well-ordered structures in synthetic materials via a universal and scalable manner still poses a grand challenge. Herein, a simple yet versatile approach is proposed to design hierarchically structured hydrogels by flow-induced alignment of nanofibrils, without high time/energy consumption or cumbersome postprocessing. Highly aligned fibrous configuration and structural densification are successfully achieved in anisotropic hydrogels under ambient conditions, resulting in desired mechanical properties and damage-tolerant architectures, for example, strength of 14 ± 1 MPa, toughness of 154 ± 13 MJ m−3, and fracture energy of 153 ± 8 kJ m−2. Moreover, a hydrogel mesoporous framework can deliver ultra-fast and unidirectional water transport (maximum speed at 65.75 mm s−1), highlighting its potential for water purification. This scalable fabrication explores a promising strategy for developing bioinspired structural hydrogels, facilitating their practical applications in biomedical and engineering fields.

Filter prepared from Janus-like graphene oxide nanosheets with heterogeneous nanochannels for highly efficient dye removal

A Janus graphene oxide filter with heterogeneous nanochannels exhibits a high interception rate and water flux towards dye removal.

Understanding the swelling behavior of Ti3C2Tx MXene membranes in aqueous media

Two-dimensional (2D) lamellar MXene membranes have demonstrated ultrafast water permeance and outstanding ion rejection performance, thus showing great potential for water purification.

Potable Water Purification Costs of Urban People: A Cross-Income Group Analysis in Greater Mirpur, Dhaka

This research examines the economic implications of water purification in urban areas of Dhaka, where foul odors and potential pathogens, have led many residents to use various water purification methods. The study aims to investigate the additional costs incurred by households for water purification and how these costs vary across income groups. Data was collected from households of different thanas in the Greater Mirpur area through structured and semi-structured questionnaires. The findings show that although 89% of households rely on water delivered by the Water Supply and Sewerage Authority (WASA), only 28% have access to clean water. Water purifiers, especially manual ones, are popular choices for water purification. The average monthly cost of water purification was found to be 331 BDT, with considerable variation based on income. Unilever was the most popular brand of water purifier, although a significant proportion of respondents selected their purifier randomly. The study highlights the urgent need for improved water quality management and treatment, particularly for low-income residents, and the importance of raising awareness about different water purification brands and their efficacy. While the research gives helpful information into the water purification practices of city’s households, certain limitations, such as its limited geographic scope and sample size, should be considered. Nevertheless, this research provides a foundation for understanding the economic challenges of water purification and encourages further research into these pressing issues.

Membranes based on Covalent Organic Frameworks through Green and Scalable Interfacial Polymerization using Ionic Liquids for Antibiotic Desalination

AbstractCovalent organic framework (COF) membranes featuring uniform topological structures and devisable functions, show huge potential in water purification and molecular separation. Nevertheless, the inability of uniform COF membranes to be produced on an industrial scale and their nonenvironmentally friendly fabrication method are the bottleneck preventing their industrial applications. Herein, we report a new green and industrially adaptable scraping‐assisted interfacial polymerization (SAIP) technique to fabricate scalable and uniform TpPa COF membranes. The process used non‐toxic and low‐volatility ionic liquids (ILs) as organic phase instead of conventional organic solvents for interfacial synthesis of TpPa COF layer on a support membrane, which can simultaneously achieve the purposes of (i) improving the greenness of membrane‐forming process and (ii) fabricating a robust membrane that can function beyond the conventional membranes. This approach yields a large‐area, continuous COF membrane (19×25 cm2) with a thickness of 78 nm within a brief period of 2 minutes. The resulting membrane exhibited an unprecedented combination of high permeance (48.09 L m−2 h−1 bar−1) and antibiotic desalination efficiency (e.g., NaCl/adriamycin separation factor of 41.8), which is superior to the commercial benchmarking membranes.

Membranes based on Covalent Organic Frameworks through Green and Scalable Interfacial Polymerization using Ionic Liquids for Antibiotic Desalination.

Covalent organic framework (COF) membranes featuring uniform topological structures and devisable functions, show huge potential in water purification and molecular separation. Nevertheless, the inability of uniform COF membranes to be produced on an industrial scale and their nonenvironmentally friendly fabrication method are the bottleneck preventing their industrial applications. Herein, we report a new green and industrially adaptable scraping-assisted interfacial polymerization (SAIP) technique to fabricate scalable and uniform TpPa COF membranes. The process used non-toxic and low-volatility ionic liquids (ILs) as organic phase instead of conventional organic solvents for interfacial synthesis of TpPa COF layer on a support membrane, which can simultaneously achieve the purposes of (i) improving the greenness of membrane-forming process and (ii) fabricating a robust membrane that can function beyond the conventional membranes. This approach yields a large-area, continuous COF membrane (19×25 cm2 ) with a thickness of 78 nm within a brief period of 2 minutes. The resulting membrane exhibited an unprecedented combination of high permeance (48.09 L m-2 h-1 bar-1 ) and antibiotic desalination efficiency (e.g., NaCl/adriamycin separation factor of 41.8), which is superior to the commercial benchmarking membranes.

Montmorillonite Membranes with Tunable Ion Transport by Controlling Interlayer Spacing.

Membranes incorporating two-dimensional (2D) materials have shown great potential for water purification and energy storage and conversion applications. Their ordered interlayer galleries can be modified for their tunable chemical and structural properties. Montmorillonite (MMT) is an earth-abundant phyllosilicate mineral that can be exfoliated into 2D flakes and reassembled into membranes. However, the poor water stability and random interlayer spacing of MMT caused by weak interlamellar interactions pose challenges for practical membrane applications. Herein, we demonstrate a facile approach to fabricating 2D MMT membranes with alkanediamines as cross-linkers. The incorporation of diamine molecules of different lengths enables controllable interlayer spacing and strengthens interlamellar connections, leading to tunable ion transport properties and boosted membrane stability in aqueous environments.

Activation of periodate by ABTS as an electron shuttle for degradation of aqueous organic pollutants and enhancement effect of phosphate

Periodate (PI) based advanced oxidation processes (AOPs) have recently attracted much attention due to their high application potential in water purification through production of reactive species. In the study, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was used as a representative electron shuttle, and its reaction with PI was investigated in detail. It was found that PI can be activated by ABTS via one-electron transfer to produce ABTS•+ and IO3•, cooperatively promoting oxidation of organic contaminants such as bisphenol A (BPA). Their contribution in BPA oxidation at pH 7 was estimated as 81.9% and 18.1%, respectively. With phosphate, BPA oxidation rate in the PI/ABTS process increased linearly with raised phosphate concentrations from 0 to 10 mM. The enhancement effect of phosphate is attributed to formation of PI-phosphate complexes, which facilitate PI activation by ABTS, and production of more ABTS•+ and IO3•, and additional phosphate radicals. Accordingly, the contribution of IO3• and phosphate radicals in BPA oxidation raised to 57.7% in the process with 4 mM phosphate, while that of ABTS•+ decreased to 42.3%. The reaction stoichiometry ratio of ABTS to PI was measured as 1.1 at pH 7, suggesting the little involvement of IO3• and phosphate radicals in production of ABTS•+ due to their high self-quenching. The PI/ABTS process exhibited excellent anti-interference capacity towards water matrix components (e.g. Cl−, HCO3− and natural organic matters). Moreover, an immobilized ABTS (ABTS/ZnAl-LDH) was successfully developed as a heterogeneous electron shuttle for PI oxidation, which resultantly exhibited the good catalytic activity and stability in degradation of BPA, further improving feasibility of the process in treatment of actual water. This work advances understanding on reaction of PI with ABTS from stoichiometric and kinetic aspects, and provides a high performance AOP for selective oxidation of trace organic contaminants.

Removal of propranolol by membranes fabricated with nanocellulose/proanthocyanidin/modified tannic acid: The influence of chemical and morphologic features and mechanism study

Polymer-based membranes containing nanocellulose and natural macromolecules have potential to treat water, however few works have associated the changes in chemical and morphological membrane's features with their performance as adsorbent. Herein, a new green composite based on nanocellulose (NC) and alkylated tannic acid (ATA) and cross-linked with proanthocyanidin was produced and incorporated into polyacrylonitrile (PAN) membranes to eliminate propranolol (PRO) from water. Characterizations revealed that the increasing of NC-ATA content reduced the pore size of the membrane's upper surface and made the finger like structure of the sublayer disappear, due to the formation of hydrophilic domains of NC/ATA which speeds up the external solidification step. The presence of NC-ATA reduced the hydrophilicity, from a water contact angle of 3.65° to 16.51°, the membrane roughness, from 223.5 to 52.0 nm, and the zeta potential from −25.35 to −55.20 mV, improving its features to be a suitable adsorbent of organic molecules. The membranes proved to be excellent green adsorbent, tridimensional, and easy to remove after use, and qmax for PRO was 303 mg·g−1. The adsorption mechanism indicates that H-bonds, ion exchange, and π-π play important role in adsorption. NC-ATA@PAN kept high removal efficiencies after four cycles, evidencing the potential for water purification.

PH-responsive BNNS/PAA nanofiltration membrane for tunable water permeance and efficient dye separation

Two-dimensional lamellar nanofiltration membranes have great application potential for water purification. Here, in order to achieve tunable water permeance and efficient dye separation, we reported a pH-responsive boron nitride nanosheets (BNNS)-based nanofiltration membrane by introducing polyacrylic acid (PAA). The strong hydrophilicity and electronegativity of PAA endow BNNS/PAA membrane with a fast water flux of 228 L·m−2·h−1 and a high methylene blue (MLB) rejection of 98%, increased by 235% and 4% compared to the neat BNNS membrane, respectively. Owing to the size sieving effect, the BNNS/PAA membrane possesses the better selectivity for the different types of dyes and dye/salt mixture from the potential pollutants in the water. Meanwhile, it exhibits diverse and tunable nanofiltration performances at different pH, implying excellent pH-responsive ability of BNNS/PAA membrane. In addition, the BNNS/PAA membranes also display the exceptional separation and long-term stability at different environments. This work provides a novel and simple strategy for designing the BNNS-based nanofiltration membrane with the pH-responsive ability, the tunable water permeance and selectively.