High-performance Water Purification Research Articles

Photocatalytically self-cleaning graphene oxide nanofiltration membranes reinforced with bismuth oxybromide for high-performance water purification

Graphene oxide (GO) membranes have emerged as promising candidates for water purification applications, owing to their unique physicochemical attributes. Nevertheless, the trade-off between permeability and selectivity, coupled with their vulnerability to membrane fouling, poses significant challenges to their widespread industrial deployment. In this study, we introduce an innovative in-situ growth and layer-by-layer assembly technique for fabricating multilayer GO membranes reinforced with bismuth oxybromide (BiOBr) on commonly employed Nylon substrates. This method allows for the creation of two-dimensional lamellar membranes capable of photocatalytic self-cleaning and tunable nanochannel dimensions. The synthesized GO/BiOBr composite membranes exhibit remarkable water permeance rates (approximately 493.9 LMH/bar) and high molecular rejection efficiency (>99 % for Victoria Blue B and Congo Red dyes). Notably, these membranes showcase an enhanced photocatalytic self-cleaning performance upon exposure to visible light. Our work provides a viable route for the fabrication of functionalized GO-based nanofiltration membranes with BiOBr inclusions, offering a synergistic combination of high water permeability, modifiable nanochannels, and effective self-cleaning capabilities through photocatalysis.

Bioinspired MXene Membranes with pH-Responsive Channels for High-Performance Water Purification

Bioinspired MXene Membranes with pH-Responsive Channels for High-Performance Water Purification

A homogeneous carbon nitride nanomodifier for promoting the water permeation of polyamide desalination membranes

Nanomaterial modification provides an effective way to enhance the separation performance of nanofiltration membranes, but the limited hydrophilicity of conventional nanostructures causes their poor solubility in solvents, affecting the quality of polyamide membranes for performance enhancement. Herein, we explored quasi-water soluble carbon nitride as a homogeneous modifier to improve the nanofiltration performance of polyamide membranes. With sufficient hydroxyl, amino, and cyano groups, the introduced quasi-water soluble carbon nitride significantly enhanced the surface hydrophilicity of the support membrane, resulting in the formation of an ultrathin functional layer for high-efficiency desalination. The high permeation flux of 108.64 L m-2h−1 (4 bar) was even twice and three times higher than those of the pristine polyamide membrane and commercial nanofiltration membranes, with a high Na2SO4 barrier rate of 98.84 % and a Cl-/SO42- selectivity of 76. This work provides an effective way to precisely regulate the structure of nanofiltration membranes for high-performance water purification.

Development of a vacuum double-slope solar still for enhanced freshwater productivity

In this study, a solar-energy-driven high performance water purification system is designed, fabricated, and examined, which may be useful for remote areas with limited access to grid electricity and underground freshwater. This research aims to enhance the performance of a conventional solar still (double-slope type) by creating vacuum inside the chamber and using paraffin wax (PCM) as energy storage material. The performance of the modified solar still (SS) is investigated and compared with the conventional solar still (CSS) in terms of productivity, distillation efficiency, and exergy efficiency. The performance analyses show that the hourly productivity and daily cumulative productivity are increased by 22.33 % and 63 % (from 5.46 L/m2 to 7.03 L/m2) respectively for the modified still compared to the conventional still. Nearly 28.72 % distillation efficiency and 22.43 % exergy efficiency enhancement are recorded for the modified system compared to the conventional system. This study also reveals that the thermal performance of the modified system is significantly improved under vacuum condition and using paraffin wax as heat storage material, which enables the still to operate at low solar intensities. The economic analysis shows that the cost of freshwater produced per liter in the modified SS is 41.4 % less than that of the conventional SS.

Multiscale Porous Carbon Materials by In Situ Growth of Metal-Organic Framework in the Micro-Channel of Delignified Wood for High-Performance Water Purification.

Porous carbon materials are suitable as highly efficient adsorbents for the treatment of organic pollutants in wastewater. In this study, we developed multiscale porous and heteroatom (O, N)-doped activated carbon aerogels (CAs) based on mesoporous zeolitic imidazolate framework-8 (ZIF-8) nanocrystals and wood using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation, in situ synthesis, and carbonization/activation. The surface carboxyl groups in a TEMPO-oxidized wood (TW) can provide considerably large nucleation sites for ZIF-8. Consequently, ZIF-8, with excellent porosity, was successfully loaded into the TW via in situ growth to enhance the specific surface area and enable heteroatom doping. Thereafter, the ZIF-8-loaded TW was subjected to a direct carbonization/activation process, and the obtained activated CA, denoted as ZIF-8/TW-CA, exhibited a highly interconnected porous structure containing multiscale (micro, meso, and macro) pores. Additionally, the resultant ZIF-8/TW-CA exhibited a low density, high specific surface area, and excellent organic dye adsorption capacity of 56.0 mg cm-3, 785.8 m2 g-1, and 169.4 mg g-1, respectively. Given its sustainable, scalable, and low-cost wood platform, the proposed high-performance CA is expected to enable the substantial expansion of strategies for environmental protection, energy storage, and catalysis.

Biomimetic vertically aligned aerogel with synergistic photothermal effect enables efficient solar-driven desalination

Taking sustainable solar energy for efficient rapid clean water production is eagerly desired to overcome the water shortage issue. However, great challenges remain in constructing short water transport channels and enhancing sunlight utilization efficiency. Herein, a biomimetic solar-driven interfacial evaporator with rapid water transport and high photothermal conversion efficiency inspired by natural-trees was successfully developed, via engineer vertically aligned hydrophilic sodium alginate (SA) aerogels while hierarchically assembled MXene interwoven carbon nanotube (CNT) networks as micro/nano light absorb layer. Due to the synergistic photothermal effect between 2D MXene nanosheets and 1D CNT with multiple reflective nanostructure and strong light-absorption over a broad spectrum, and super-hydrophilic SA with highly oriented water transport channels, which enables fast water/vapor transport while utilizing solar energy efficiently. Vertically aligned aerogel exhibits an excellent water evaporation performance which as high as 2.416 kg m−2 h−1 (deducting dark conditions) and remarkable solar energy utilizing efficiency of 90.56 %, which are extremely higher than that of most reported desalination devices. Furthermore, the solar-driven evaporator also exhibits strong antibacterial properties and long-term operation stability. The biomimetic vertically aligned aerogel with excellent water evaporation and light utilization efficiency holds great promise for high-performance water purification and desalination applications. Synopsis statementResearch on the rapid clean water production from wastewater/seawater with high solar energy utilization efficiency has become a hot topic, and solar-driven desalination offers a sustainable solution to meet water demands. This study reports a biomimetic solar-driven interfacial evaporator with oriented water transport nanochannel and multi-reflective solar absorber for efficient clean water production.

Potato-based microporous carbon cake: Solar radiation induced water treatment

The use of solar-driven interfacial water evaporation for water desalination is a very interesting research topic for its high-performance water purification. The rapid evaporation of water at the air-water interface has been enhanced by solar absorbers. This work described the fabrication of a porous carbon cake with interconnected pores and super-hydrophilic surfaces from a potato slice. The fabricated carbon cake exhibits a high steam generation rate of 3.18 kg m-2 h-1 under 1 sun illumination. We also fabricated a large area evaporator and demonstrated the collection of more than 2.8 lit of condensed water from 0.8 m2 area in 5.5 h with natural (∼0.5 Sun) solar illumination. High evaporation rate was obtained due to the super-hydrophilic and less thermal conductivity of the as-fabricated carbon cake. Moreover, the device providing a high mechanical stability, which could be necessary for long-term potential usage. The high salt rejection ability of the device were investigated in detail. The total cost to generate freshwater from CEPC STE for nearly 8 months is $ 36.54/m2. Therefore, this system can be used for evaporation-based high concentrated dye and brine water purification in a cost-effective and highly efficient way.

A Composite Fabric with Dual Functions for High-Performance Water Purification.

The dilemma of diminishing freshwater resources caused by water pollution has always impacted human life. Solar-driven interfacial evaporation technology has the potential for freshwater production via solar-driven distillation. However, in solar-driven interfacial evaporation technology, it is difficult to overcome the problem of wastewater containing various contaminants. In this work, we propose a bifunctional fabric created by depositing titanium dioxide@carbon black nanoparticles onto cotton fabric (TiO2@CB/CF). The TiO2@CB/CF has a coupling effect that includes the photothermal effect of CB and photocatalysis of TiO2, and it can not only generate clean water but can also purify contaminated water. The resulting bifunctional fabric can achieve an outstanding water evaporation rate of 1.42 kg m−2 h−1 and a conversion efficiency of 90.4% in methylene blue (MB) solution under one-sun irradiation. Simultaneously, the TiO2@CB/CF demonstrates a high photocatalytic degradation of 57% for MB solution after 2 h with light irradiation. It still shows a good photocatalysis effect, even when reused in an MB solution for eight cycles. Furthermore, the TiO2@CB/CF delivers excellent performance for actual industrial textile dyeing wastewater. This bifunctional fabric has a good application prospect and will provide a novel way to resolve the issue of freshwater scarcity.

Poly(ionic liquid)-Armored MXene Membrane: Interlayer Engineering for Facilitated Water Transport.

Two‐dimensional (2D) MXene‐based lamellar membranes bearing interlayers of tunable hydrophilicity are promising for high‐performance water purification. The current challenge lies in how to engineer the pore wall's surface properties in the subnano‐confinement environment while ensuring its high selectivity. Herein, poly(ionic liquid)s, equipped with readily exchangeable counter anions, succeeded as a hydrophilicity modifier in addressing this issue. Lamellar membranes bearing nanochannels of tailorable hydrophilicity are constructed via assembly of poly(ionic liquid)‐armored MXene nanosheets. By shifting the interlayer galleries from being hydrophilic to more hydrophobic via simple anion exchange, the MXene membrane performs drastically better for both the permeance (by two‐fold improvement) and rejection (≈99 %). This facile method opens up a new avenue for building 2D material‐based membranes of enhancing molecular transport and sieving effect.

Multifunctional Photocatalytic Filter Paper Based on Ultralong Nanowires of the Calcium-Alendronate Complex for High-Performance Water Purification.

Semiconductor photocatalysts and membrane separation technology have been widely used in the field of water treatment. Usually, the particles of traditional semiconductor photocatalysts are easy to aggregate, difficult to separate from the liquid phase after photocatalysis, and may even cause secondary pollution. On the other hand, the membrane separation technology is also facing the problem of sharp decreases in removal efficiency and water flux caused by the membrane fouling. However, it is an attractive and promising solution to combine two technologies of photocatalysis and membrane separation for high-performance water treatment. In this work, we have developed the calcium oleate precursor solvothermal method to synthesize ultralong nanowires (UNWs) of Ca-alendronate (Ca-ALN) complex for the first time. Experimental results and data analysis indicate that the as-prepared Ca-ALN ultralong nanowires are an n-type semiconductor with an energy band gap of 3.41 eV. A new type of multifunctional photocatalytic filter paper has been developed based on ultralong nanowires of Ca-ALN complex (Ca-ALN-UNWs) and cellulose fibers (CFs). The as-prepared Ca-ALN-UNW/CF photocatalytic filter paper exhibits multifunctions of photocatalysis, adsorption, and filtration, which can be used for high-performance treatment of the wastewater containing various pollutants such as heavy-metal ions, dyes, antibiotics, and bacteria. The active oxygen species produced by the Ca-ALN-UNW/CF photocatalytic filter paper under light illumination are determined by electron spin resonance, and the energy band gap and photoelectric properties of the material are tested by ultraviolet-visible diffuse reflectance spectroscopy and electrochemical workstation. The pure water flux of the Ca-ALN-UNW/CF photocatalytic filter paper is very high, which can reach 2230.5 L m-2 h-1 under a working pressure of 0.1 MPa. The Ca-ALN-UNW/CF photocatalytic filter paper is promising for various applications such as highly efficient water purification and in the biomedical field.

Mussel-inspired structure evolution customizing membrane interface hydrophilization

Advanced energy-water systems demand fabrication of high-performance water purification membranes. Polymeric membranes are typically hydrophobic, not amenable to conventional surface functionalization methods. Mussel adhesive proteins have inspired numerous adhesive polymer coatings via the structure-function simulation. Nonetheless, research about maximizing membrane interface hydrophilization and relevant concept guidance are still far from enough. Here, we put forward a “split-and-adjust” concept and proof it using a simplified catechol/silane biomimetic composite coating system for boosting interface hydrophilization. As a result, the hierarchically nanostructured silicified hydrophilic membranes were fabricated. The hydrophilicity could be tailored via tuning reagent dose recipes. The as-fabricated hydrophilic membrane presented benign fouling resistance in oil-in-water emulsion filtration tests. In addition, the rinsing examination indicates the coating is well stabilized. The as-developed “split-and-adjust” concept for the composite coating system provides promising guidance to broaden and optimize the customized biomimetic interface functionalization toolbox.

A nanocomposite paper comprising calcium silicate hydrate nanosheets and cellulose nanofibers for high-performance water purification.

Removal of soluble organic and inorganic contaminants from wastewater to produce clean water has received much attention recently. However, the simultaneous enhancement of water permeability and removal efficiency is still a challenge for filtration membranes. Here, we present a new kind of nanocomposite paper (CSH/CNF) consisting of calcium silicate hydrate (CSH) nanosheets and cellulose nanofibers (CNFs), and demonstrate the rapid water filtration and highly efficient contaminant (e.g., dyes, proteins, and metal ions) adsorption properties. The CNFs can serve as the bridging material to connect the CSH nanosheets to form a porous network structure and vital channels in the CSH/CNF paper for rapid water transportation. The weight ratio of CSH nanosheets in the paper is up to 75–85%. The weight ratio of CSH nanosheets has a significant effect on the water permeability and removal efficiency. The water permeability of the CSH/CNF paper with 82.5 wt% CSH nanosheets reaches as high as 312.7 L m−2 h−1 bar−1, which is about 14.7 times that of the CSH/CNF paper with 75 wt% CSH nanosheets. Because of the high specific surface area and abundant adsorption sites of CSH nanosheets, the CSH/CNF paper with 82.5 wt% CSH nanosheets exhibits high adsorption capacities and removal efficiencies for methyl blue (242.6 mg g−1, 97.3%), bovine serum albumin (289.2 mg g−1, 98.5%) and Pb2+ ions (366.2 mg g−1, 98.2%). The CSH/CNF nanocomposite paper holds great potential for application in environmental wastewater purification.

Mussel-/diatom-inspired silicified membrane for high-efficiency water remediation

Water purification polymeric membranes are critical for defending water safety and mitigating water crisis stress. They are hampered by membrane hydrophobicity for undesirable filtration performance and troublesome fouling issues. Membrane interface hydrophilization with good hydrophilicity and well-behaved adhesion are highly desired. Here, inspired by bio-protein adhesives and silicified diatom shells, a facile one-step biomimetic silicification method by tannic acid and 3-glycidyloxypropyltrimethoxysilane was explored at ambient conditions. The silicification method is green and cost-effective. The as-decorated membranes boosted hydrophilicity with outstanding rigid test tolerance. The silicification conditions could be regulated by resultant surface chemistry. The hydrophilized microfiltration membrane realized cyclable oily emulsion purification with flux over 2580 L m−2 h−1 and oil repulsion over 99.2%. It also demonstrates outstanding repulsion to crude oil. The as-decorated ultrafiltration membrane displayed an improved protein interception (BSA interception above 94.1%, water flux about 424 L m−2 h−1) and antifouling (73.2% enhancement) capacity. The as-presented biomimetic silicification hydrophilization strategy could potentially promote the development of high-performance water purification membranes and efficient energy-water nexus system.

Performance efficiency and kinetic studies of water purification using ZnO and MgO nanoparticles for potassium permanganate

Zinc oxide (ZnO) and Magnesium oxide (MgO) nanoparticles (NPs) have been synthesized by solid–solid reaction technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) were used to investigate the structural properties of ZnO and MgO NPs. XRD indicates that structural of ZnO NPs has a hexagonal structure with space group P63mc. On the other hand, MgO NPs is cubic structure with space group Fm $$\bar{3}$$ m. The photocatalytic efficiency of both ZnO and MgO NPs as a catalyst was illustrated by studying the extreme quantity of potassium permanganate (KMnO4) degradation rate in wastewater. KMnO4 achieved 17% and 25% degradation rate in 180 min for ZnO and MgO NPs, respectively. The experimental data were examined by the kinetic models of pseudo-first and second order as well as intra-particle diffusion. The obtained data is expressed well by the second-order kinetic model for both NPs. Moreover, according to the experimental results, MgO NPs has high-performance water purification as a comparison of ZnO NPs effect.

Self-floating aerogel composed of carbon nanotubes and ultralong hydroxyapatite nanowires for highly efficient solar energy-assisted water purification

Solar energy-driven water evaporation is a promising technique for clean water regeneration to tackle the world-wide water scarcity problem. Previous studies have revealed the important role of the bilayer structure in the solar energy-driven water evaporation, the top layer is the photothermal material, and the bottom porous material is used for water transportation and heat insulation. Herein, a new kind of the bilayer aerogel composed of hydrophilic ultralong hydroxyapatite (HAP) nanowire aergel and hydrophobic carbon nanotube (CNT) coating has been developed and demonstrated as a highly efficient self-floating evaporator for solar energy-driven photothermal water purification. The hydrophilic and highly porous HAP nanowire aerogel with a low thermal conductivity ensures excellent thermal management and high water evaporation rate, and the CNT coating layer enables highly efficient solar light absorption and energy conversion. With these structural merits, the as-prepared HAP/CNT bilayer aerogel has a high water evaporation rate of 1.34 kg m−2 h−1 and high water evaporation efficiency of 89.4% under solar light irradiation at a power density of 1 kW m−2. Additionally, the high-performance water purification function of the HAP/CNT bilayer aerogel is demonstrated by producing clean water from the actual seawater and simulated wastewater. The experimental results demonstrate the promising potential of the as-prepared HAP/CNT bilayer aerogel for high-performance solar energy-driven photothermal clean water regeneration.

Ultralong Hydroxyapatite Nanowire-Based Filter Paper for High-Performance Water Purification.

A new kind of environmentally friendly filter paper based on ultralong hydroxyapatite nanowires (HAPNWs) and cellulose fibers (CFs) with excellent filtration and adsorption properties has been developed for the application in high-performance water purification. The use of polyamidoamine-epichlorohydrin (PAE) resin increases the wet mechanical strength of the as-prepared HAPNW/CF filter paper. The addition of CFs enhances the mechanical strength of the HAPNW/CF filter paper. Owing to the porous structure and superhydrophilicity of the as-prepared HAPNW/CF filter paper, the pure water flux is as high as 287.28 L m-2 h-1 bar-1 under cross-flow conditions, which is about 3200 times higher than that of the cellulose fiber paper with addition of PAE. More importantly, the as-prepared HAPNW/CF filter paper shows superior performance in the removal of TiO2 nanoparticles (>98.61%) and bacteria (up to 100%) in water by the size exclusion and blocking effect. In addition, the HAPNW/CF filter paper also exhibits high adsorption capacities for methyl blue (273.97 mg g-1) and Pb2+ ions (508.16 mg g-1). The adsorption mechanism of the HAPNW/CF filter paper is investigated. The as-prepared environmentally friendly HAPNW/CF filter paper with both excellent filtration and adsorption properties has promising application in high-performance water purification to tackle the worldwide water scarcity problem.

Recent Advances in Nanoporous Membranes for Water Purification.

Nanoporous materials exhibit wide applications in the fields of electrocatalysis, nanodevice fabrication, energy, and environmental science, as well as analytical science. In this review, we present a summary of recent studies on nanoporous membranes for water purification application. The types and fabrication strategies of various nanoporous membranes are first introduced, and then the fabricated nanoporous membranes for removing various water pollutants, such as salt, metallic ions, anions, nanoparticles, organic chemicals, and biological substrates, are demonstrated and discussed. This work will be valuable for readers to understand the design and fabrication of various nanoporous membranes, and their potential purification mechanisms towards different water pollutants. In addition, it will be helpful for developing new nanoporous materials for quick, economic, and high-performance water purification.

Microfluidic photoelectrocatalytic reactors for water purification with an integrated visible-light source

This paper reports experimental studies using the photoelectrocatalytic effect to eliminate a fundamental limit of photocatalysis - the recombination of photo-excited electrons and holes. The fabricated reactor has a planar reaction chamber (10 × 10 × 0.1 mm(3)), formed by a blank indium tin oxide glass slide, an epoxy spacer and a BiVO(4)-coated indium tin oxide glass substrate. A blue light-emitting diode panel (emission area 10 × 10 mm(2)) is mounted on the cover for uniform illumination of the reaction chamber. In the experiment, positive and negative bias potentials were applied across the reaction chamber to suppress the electron/hole recombination and to select either the hole-driven or electron-driven oxidation pathway. The negative bias always exhibits higher performance. It is observed that under -1.8 V the degradation rate is independent of the residence time, showing that the accompanying electrolysis can solve the oxygen deficiency problem. The synergistic effect of photocatalysis and electrocatalysis is observed to reach its maximum under the bias potential of ± 1.5 V. The photoelectrocatalytic microreactor shows high stability and may be scaled up for high-performance water purification.

Ultrapure water produced efficiently

The Neptune Ultimate system was recently added to the Select Neptune range from Purite Limited, a UK-based manufacturer of high performance water purification equipment.