High-efficiency Water Purification Research Articles

A tandem dual-pathway non-radical water purification simultaneously induced by single-molecule peroxymonosulfate with a catalyst of coexisting Cu single atoms and Fe3C nanoparticles

The non-radical pathways of persulfate (PMS/PS)-based heterogeneous advanced oxidation processes offer effective means for treating complex water matrices. However, the large-scale application is hindered by the increased input costs and substantial accumulation of SO42–. Therefore, it is crucial to develop novel pathways for efficient PMS/PS activation. Here, we construct a CuSA/Fe3C-NC catalyst with Cu single atoms (SAs) and Fe3C nanoparticles (NPs) co-anchored on a carbon support. The improved d-band centers of Cu and Fe elements optimize the PMS adsorption and activation. Unlike previous studies, the electron acceptor PMS in electron transfer process is not be converted to SO42– but rather to singlet oxygen (1O2) via superoxide radicals (O2•–). A tandem dual-pathway non-radical oxidation system induced by a single-molecule PMS leads to higher PMS utilization. Under extremely low catalyst and PMS dosage conditions (catalyst dosage = 0.04 g/L, PMS dosage = 0.2 mmol/L), CuSA/Fe3C-NC + PMS system can rapidly remove bisphenol A within 30 min and achieve a mineralization rate of 85 %. This work provides strong support for the rational design of catalyst structures to achieve low-input and high-efficiency water purification processes.

A high-flux, photocatalytic wood-derived filter for high-efficiency water purification

Wastewater purification has evolved into a global problem in the face of increasing scarcity of freshwater resources. Photocatalysis technology possesses prominent advantages in treating pollutants in water because of its low cost and mild reaction conditions, which provides an effective way to treat multiple pollutants and reduce membrane fouling. Herein, we combine photocatalysis technology with filtration technology via in situ reduction Bi0 with Bi2SiO5 strategy incorporating a carbonized wood filter to synthesize carbon/Bi2SiO5@Bi bi-functional composite. Thus, simultaneous filtration and photocatalytic degradation of Rhodamine B and tetracycline were achieved. After filtrating for 30 min, the degradation rate of RhB and TC were 94.23 % and 81.39 %, respectively. Especially, the flux of RhB and TC were up to 2162.16 L m−2 h−1 and 1811.32 L m−2 h−1. In addition, the composite filter also has good recyclability and reusability, after 5 cycles, the degradation efficiency of RhB remains at 91 %. This study utilized photocatalytic technology combined with membrane filtration technology to successfully solve the contradiction between catalytic efficiency and water flux, which realized rapid and dynamic removal of organic pollutants from water. Besides, the use of carbonized wood-based materials provides a potential biomass technology for the preparation of bifunctional photocatalytic filters.

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.

Electro-responsive OCNT/PPy membrane for efficient irreversible-fouling control through electroregulation of electrostatic and fluid interaction forces

Membrane-based separation process has been proven to be a powerful strategy for low-energy-consumption and high-efficiency water purification. However, the practical application is still subjected to serious membrane fouling. In this study, an impressive approach to alleviate membrane fouling is proposed using an electro-conductive oxygenated carbon nanotube/polypyrrole (OCNT/PPy) membrane combining electrically-regulated electrostatic and fluid forces. Benefiting from the negative potential (−1.18 V vs. SCE) applied on the membrane, the electric polarization effects significantly enhance the repulsive electrostatic force on contaminant. The transmembrane pressure increases at an ignorable rate during the filtration process. Meanwhile, for accumulated irreversible membrane fouling after multi-cycle filtrations, the positive potential (+1.19 V vs. SCE) exerted on OCNT/PPy membrane can decrease the fluid resistances of backwash flow. As a result, the electrically-regulated hydraulic backwash achieves a thorough recovery rate of permeance at 99.1 %. The numerical analysis of the antifouling mechanism reveals that the mitigation of irreversible membrane fouling is mainly attributed to rapid formation of a loose cake layer under electrical assistance. Moreover, the computational fluid dynamics verifies that the reduction of water-channel resistance enhances the elimination of foulants in membrane pores. This work motivates a new thought for membrane fouling control through electroregulation of electrostatic and fluid forces at the membrane-water interface.

A Janus membrane with electro-induced multi-affinity interfaces for high-efficiency water purification.

Drinking water with micropollutants is a notable environmental concern worldwide. Membrane separation is one of the few methods capable of removing micropollutants from water. However, existing membranes face challenges in the simultaneous and efficient treatment of small-molecular and ionic contaminants because of their limited permselectivity. Here, we propose a high-efficiency water purification method using a low-pressure Janus membrane with electro-induced multi-affinity. By virtue of hydrophobic and electrostatic interactions between the functional interfaces and contaminants, the Janus membrane achieves simultaneous separation of diverse types of organics and heavy metals from water via single-pass filtration, with an approximately 100% removal efficiency, high water flux (>680 liters m-2 hour-1), and 98% lower energy consumption compared with commercial nanofiltration membranes. The electro-induced switching of interfacial affinity enables 100% regeneration of membrane performance; thus, our work paves a sustainable avenue for drinking water purification by regulating the interfacial affinity of membranes.

Intrinsic electrical conductivity of monolithic biochar

While biochar is an effective and viable tool for alleviating climate change, monolithic biochar is emerging as a functional material for applications that enhance sustainability, such as renewable energy storage and low-cost, high-efficiency water purification. Its performance depends on its physical and chemical characteristics, including electrical conductivity. Monolithic biochar's bulk conductivity is expected to rely on the porosity and conductivity of its carbon matrix - intrinsic conductivity – a fundamental property that has not been systematically studied. The work discerns intrinsic conductivity and its dependence on biomass species and carbonization temperature. We carbonized four hardwoods, three softwoods, and bamboo following an ultra-slow pyrolysis procedure and characterized biochar's chemical and structural properties. We modified the two-probe method and measured bulk conductivity along the axial direction. The bulk conductivity and density followed the linear and the Reynolds-Hough relationships, allowing the determination of intrinsic conductivity. The intrinsic conductivity increased with pyrolysis temperatures and became independent of wood species at 1500 °C.According to the linear model, the highest value of wood biochar produced at 1500 °C was 14,600 S/m. Bamboo biochar had a higher intrinsic conductivity (21,000 S/m), attributed to bamboo's high cellulose content and large graphite nanocrystal size in its biochar. Moreover, the modified two-probe method minimized measurement uncertainty and enabled the quantification of natural variation in biochar conductivity, which was less than 10% for the same wood species. These findings will help strengthen monolithic biochar's potential as a low-cost, high-performance functional material.

Polymeric PDI-based photocatalytic nanoarchitectures promoting the performance of thin film composite membrane for forward osmosis water purification

Exploring versatile membrane with photodegradation capability provides a promising approach to overcome the fouling dilemma of membrane technologies, while the utilization of photocatalysts in the realm of forward osmosis encounters challenges, primarily due to the propensity of the potent oxidizing species produced during photocatalysis to cause substantial harm to the delicate nano-selective layer present within forward osmosis membrane. In this study, we demonstrate a multi-functional polymeric membrane with good stability for water purification via forward osmosis separation. Organic perylene diimide supermolecule was employed to construct a heterostructured catalytic layer for abating the attached pollutants under visible light irradiation. The interfacial polymerization of polyamide layer on the other side of polyethersulfone substrates allows the selective separation function. The synergistic effect of catalytic layer and selective layer simultaneously improved the separation performance and anti-fouling capability, endowing the Janus membrane with a reduced reverse NaCl flux, 83% lower, and a suppressed membrane fouling, 81% lower than the original membrane. This work provides a new strategy for the design of multi-functional composite membrane for high-efficiency water purification.

Distribution-according-to-work: Enhancing solar vapor generation of photothermal sponge by using cellulose-based water storage platform

Interfacial solar vapor generation (ISVG) has shown extraordinary promise in achieving high-efficiency water purification. However, the rapid water supply often leads to excessive water in the solar absorber, resulting in undesired heat loss and a decrease in evaporation rate. To tackle this issue, we developed a bio-based solar evaporator comprising cellulose-based water retention resin (CRR) and straw-derived photothermal sponge. CRR serves as an effective water storage platform with a high binding capacity for water molecules, preventing water from entering the absorber and reducing the water evaporation enthalpy. The water management of CRR confines the solar-to-vapor conversion to the interface between CRR and the photothermal sponge, thereby eliminating the adverse effects of excess water. Additionally, the ISVG process operates based on the principle of Distribution-according-to-work, meaning that the quantity of generated vapor depends on the evolution of the sponge structure. Optimal sponge configuration enables evaporation rates of 2.28 and 1.53 kg/m2/h under solar irradiation of 1.0 and 0.5 kW/m2, respectively. Additionally, the obtained evaporator is capable of producing 7.1 kg/m2/day of freshwater in outdoor experiment. This report proposes a novel approach to designing an ISVG device that incorporates effective water management strategy for achieving high-efficiency water purification in real-world scenarios.

Chitin nanocrystals scaffold by directional freezing for high-efficiency water purification

Rapid and energy-saving water purification is urgently needed to solve the increasingly severe water shortage problem. Herein, we prepared chitin nanocrystals (ChNCs) scaffolds with aligned channels by the liquid nitrogen-assisted directional freezing method. The aligned channel in the porous ChNCs scaffold can quickly adsorb water to a saturation state. Glutaraldehyde crosslinked ChNCs scaffold (XChNCs) had good mechanical and water stability, which could float on the water surface stably. The ink coated XChNCs scaffold achieved a high evaporation rate of 4.45 kg m-2 h−1 under 1 sun irradiation. Moreover, XChNCs scaffold showed excellent salt, acid, and alkali resistance in the oil–water separation experiment. The XChNCs scaffold showed excellent dye adsorption performance because of its high porosity, and the adsorption ratio of both methylene blue and Congo red dyes exceeded 95 %. This work prepared a renewable, biodegradable, high-performance scaffold derived from biomass, which shows promising application in water purification such as seawater desalination, oil–water separation, and dye adsorption.

Novel strategy of highly efficient solar-driven water evaporation using MWCNTs-ZrO2-Ni@CQDs composites as photothermal materials

Solar-driven water evaporation is a promising technology for high efficiency water purification by absorbing solar energy and converted into localized heat. Herein, we report a low-cost approach for developing a novel photothermal materials based on combination of ZrO2 nanoparticles (NPs) with Ni doped carbon quantum dots (Ni@CQDs) and multi-walled carbon nanotube (MWCNT) coated on melamine foam (MF) surface. The formation of Ni@CQDs was confirmed by red-shift absorbance and fluorescence. Moreover, the shift in XRD diffraction angle indicated the Ni@CQDs incorporated into the ZrO2 and carbon framework of MWCNT. The composite absorber demonstrates excellent solar-water evaporation rate of 1.95 kg m−2 h−1 and high evaporation efficiency of 89.5%, which is ten-fold improvement as compared to pure water (0.19 kg m−2 h−1) under 1-Sun irradiation. The enhancement in evaporation rate is mainly attributed to the strong light absorption of 94% and extremely low thermal conductivity of MWCNT/ZrO2/Ni@CQDs (0.038 W m−1 K−1). The composite absorber capable of continuous operation of 6 cycles under 1-Sun irradiation, indicates high durability and completely reduced organic dyes (99.8%). Accordingly, the novel design of MWCNT/ZrO2/Ni@CQDs as composite absorber as high performance solar-driven water evaporation and wastewater purification.

High-efficiency water purification for methyl orange and lead(II) by eco-friendly magnetic sulfur-doped graphene-like carbon-supported layered double oxide

Traditional disposal techniques for the spent layered adsorbents after capturing organics suffer from intractable obstacles, such as resource waste and secondary pollution. To address this diploma, we here developed the “resource-utilization” strategy, i.e., converting the organic layered double hydroxide (as representative) to magnetic sulfur (S)-doped graphene-like carbon-supported layered double oxide (MG/S-LDO) to be reutilized in water purification. The as-prepared MG/S-LDO exhibited outstanding remediation ability toward methyl orange (MO) and lead(II), with the adsorption capacity of 1456 and 656 mg g−1, respectively. Specifically, the residue concentration of Pb2+ was reduced to 0.15 mg L−1 within 1 h, which met the discharge limit of the secondary industrial wastewater. MG/S-LDO could also maintain the preeminent adsorption capability under various interferences (such as wide pH and co-existing ions), even in the authentic water matrices. The removal mechanisms were systematically investigated to unveil that MO removal was dominated by metal-complexation, “memory effect”, and π-π electron donor–acceptor (EDA). While for Pb2+ removal, besides the released OH- from LDO as precipitate agent, the vacancy defect resulting from the S doping played a crucial role in electron interaction between Pb2+ and S-doped graphene. Additionally, the MG/S-LDO was further confirmed as an eco-friendly adsorbent with excellent reusability via the acute toxicity tests using green algae and multiple cycle experiments. This work provides a novel resource-utilization strategy for organic layered wastes to construct the functional eco-friendly materials in wastewater purification realm.

Effect of hydrogenated iron oxide nanoparticles with regular spherical shape by underwater plasma discharge treatment for high-efficiency water purification

We have developed a template-free, easily controllable, and simple method for the mass production of hydrogenated iron oxide nanoparticles (NPs). These NPs were formed with a regular spherical shape by underwater plasma discharge treatment at room temperature and atmospheric pressure. The various phases of well-crystallized iron oxide NPs were carefully monitored by controlling the amount of hydrazine. Further, the obtained Brunauer–Emmett–Teller surface area of 67.86 m2/g was much larger than that of a commercial sample (32.40 m2/g), which was further increased to 85.07 m2/g by adjusting the amount of hydrazine. The removal efficiency for heavy metal and organic dyes was obtained to be ~100%, which was 10 times faster than that of the commercial sample. Furthermore, ~100% flocculation efficiency was obtained by using only 6 g/g microalgal cell of the prepared iron oxide, whereas no significant change was observed for commercial iron oxide irrespective of the amount of flocculant. These excellent efficiencies for the removal of pollutant from waste water can be originated in the high specific surface area, relatively positively charged surface, and good crystallinity of the synthesized samples. These indicate that the hydrogenated iron oxide NPs in this study are potentially useful for water purification by serving as an adsorbent, photocatalytic material, and flocculant.

Efficient Solar Evaporation by [Ni(Phen)3 ][V14 O34 Cl]Cl Hybrid Semiconductor Confined in Mesoporous Glass.

Efficient utilization of solar energy for water evaporation is an advanced and environmentally friendly technology to address the crisis of global drinking water shortages. This study concerns an efficient solar vapor generator comprised of a light-absorbing and photothermal hybrid compound [Ni(Phen)3 ][V14 O34 Cl]Cl (NiV14 ) confined in mesoporous and hydrophilic glass (meso-glass). The generator is floated in water by supporting it on a domestic melamine-formaldehyde (MF) foam to ensure evaporation at the water-air interface. The porous structures and poor thermal conductivities of the meso-glass and MF foam contribute to enabling a consistent water supply, strong solar thermal localization, and less heat dissipation and convection. Associated with the strong photothermal role of NiV14 , these synergistic effects lead to a water evaporation rate of 14.38 kg m-2 h-1 with total water evaporation efficiency of 111.4% under 6 suns and a daily solar water purification yield of 42.00 L m-2 under 1 sun irradiation. This solar evaporation system shows great promise for high-efficiency water purification application.

Hierarchically Assembled Graphene Oxide Composite Membrane with Self-Healing and High-Efficiency Water Purification Performance.

Graphene oxide (GO) with a two-dimensional lamellar structure and single-atom thickness has exhibited advantages in water purification by stacking to a continuous membrane. However, a proper method to further increase the separation property of the GO membrane is still urgently needed. Besides, damage to the membrane during the full-scale application processes and the resulted consequential loss are prevalent problems need to be solved. Here, a hierarchically assembled GO composite membrane was developed that can achieve high-efficiency water purification performance and self-healing property via the synergistic effect of the metal-organic framework (MOF) and the coated hydrophilic layer of chitosan. The intercalated MOF effectively expanded the channel space of GO and endowed the channels with molecular-sieving property. Meanwhile, the coated chitosan layer can selectively adsorb water and achieve self-healing through the cross-linking reaction. The prepared GO composite membrane shows largely improved water flux (14.62 L m-2 h-1 bar-1), increased 344% than the water flux of the GO membrane, high rejection ratio (>99% for dyes), and good antifouling performance. In addition, the damaged GO composite membrane can recover its water flux (95%) and rejection ratio (96%) through a facile self-healing process.

Construction of ternary Ag@ZnO/TiO2 fibrous membranes with hierarchical nanostructures and mechanical flexibility for water purification

Rational design of semiconductor membrane photocatalyst with good mechanical flexibility and excellent photocatalytic activity is of significance for environmental remediation. Herein, flexible Ag@ZnO/TiO2 fibrous membranes with hierarchical nanostructures were fabricated through combining a simple electrospinning method and subsequent hydrothermal reaction and photodeposition process. In the ternary nanocomposite, ZnO nanorods were firmly anchored onto TiO2 nanofibers, while Ag nanoparticles were evenly decorated on the surface of both ZnO and TiO2. Benefiting from the improved light absorption, large surface area, and effective charge separation, the resultant Ag@ZnO/TiO2 membranes displayed superior photocatalytic degradation efficiency of 91.6% toward tetracycline hydrochloride within 1 h, and also exhibited prominent antibacterial activity with a 6.5 log inactivation of E. coli after 1 h simulated solar light exposure. Significantly, the membrane photocatalyst still preserved structural integrity and mechanical flexibility after utilization. This study provides an alternative approach for designing and synthesizing flexible TiO2-based membrane photocatalysts toward high-efficiency water purification.

Plant leaves inspired sunlight-driven purifier for high-efficiency clean water production

Natural vascular plants leaves rely on differences in osmotic pressure, transpiration and guttation to produce tons of clean water, powered by sunlight. Inspired by this, we report a sunlight-driven purifier for high-efficiency water purification and production. This sunlight-driven purifier is characterized by a negative temperature response poly(N-isopropylacrylamide) hydrogel (PN) anchored onto a superhydrophilic melamine foam skeleton, and a layer of PNIPAm modified graphene (PG) filter membrane coated outside. Molecular dynamics simulation and experimental results show that the superhydrophilicity of the relatively rigid melamine skeleton significantly accelerates the swelling/deswelling rate of the PNPG-F purifier. Under one sun, this rational engineered structure offers a collection of 4.2 kg m−2 h−1 and an ionic rejection of > 99% for a single PNPG-F from brine feed via the cooperation of transpiration and guttation. We envision that such a high-efficiency sunlight driven system could have great potential applications in diverse water treatments.

Covalently cross-linked graphene oxide aerogel with stable structure for high-efficiency water purification

Porous graphene-based aerogels (GAs) hold great promise for water purification due to their fascinating properties. However, weak connections between the graphene oxide nanosheets cause instability and incompressibility in GAs during practical applications. Herein, the small organic molecule of cysteamine was selected as a covalent cross-linker to fabricate GAs through a facile one-step synthesis method. The porosity and mechanical stability of GAs were simultaneously improved due to strong covalent cross-linking between the graphene oxide nanosheets via cysteamine as the linkage. The resultant graphene/cysteamine aerogels (GCAs) were compressible with excellent structural stability under different acid, base, and organic solution conditions. The maximum oil absorption capacity of the GCAs reached as high as 251 g/g and did not obviously decrease even after regeneration by squeezing. In addition, the GCAs exhibited a high adsorption capacity for common dyes, such as methylene blue (207.8 mg/g) and methyl orange (70.2 mg/g). As expected, the as-prepared aerogels with high adsorption capacities, structural stability and excellent compressibility, have great potential as recyclable and durable materials for water purification.

A novel Fe(OH)3/g-C3N4 composite membrane for high efficiency water purification

Membranes assembled from nanomaterials are widely studied in separation field. Herein, a novel 0D/2D composite membrane was fabricated for water purification. The 0D nanomaterial is Fe(OH)3 nanoparticles and the 2D nanomaterial is g-C3N4 nanosheets. For the Fe(OH)3/g-C3N4 composite membrane, the g-C3N4 layer acts as support for the deposition of Fe(OH)3 nanoparticles, while the Fe(OH)3 nanoparticles layer serves as separation layer. The Fe(OH)3 nanoparticles bond with the g-C3N4 layer through electrostatic interaction. The composite membrane demonstrates a pure water permeance of 48 L m−2 h−1 bar−1 and has a molecular weight cut-off (MWCO) of 800 Da. The excellent separation performance is attributed to that the g-C3N4 layer shows little water transport resistance and pores formed between Fe(OH)3 nanoparticles are uniform. Benefitting from the electrostatic interaction, the composite membrane demonstrates a good stability in aqueous environment during 40 h operation. In addition, the morphologies, surface hydrophilicity, separation performance and stability of the composite membrane were investigated in detail.

Graphene oxide as filter media to remove levofloxacin and lead from aqueous solution

There is an increasing need to develop novel and high-efficiency water purification technologies. This work systematically evaluated the potential of using graphene oxide (GO) directly as filter media for the removal of levofloxacin (LEV), an emerging contaminate, and lead (Pb), a heavy metal, from aqueous solution. Batch and fixed-bed experiments were conducted to determine the sorption behaviors of LEV and Pb onto the GO. In the batch system, GO showed strong sorption of the two contaminants with Langmuir maximum adsorption capacities of 256.6 and 227.2 mg g−1, respectively. The removal of LEV and Pb by GO in fixed-bed columns was high under all tested conditions in both single and mixed solution systems. The removal efficiency of the two contaminants in the GO-sand columns increased with increasing GO content, but decreased with increasing injection flow rate. In the mixed solution system, although LEV and Pb competed for sorption, the GO media still had high removal efficiencies for them. The column experimental data were well described by the Bed Depth Service Time (BDST) model, suggesting the model can be used for the design of GO-sand filters in large-scale applications. Findings from this work demonstrated that GO is a promising nano-adsorbent that can be used as a high-efficiency filter media in water treatment to remove hazardous metal elements and emerging contaminants.

The Technology of High Efficiency Water Purification

A new promising water purification technology, soft fiber wadding filter, was introduced in this article. The technology has the advantages of energy saving and emission reduction efficiency greatly, is currently the most advanced water purification. This paper explains the structure of the technical equipment, tell the filtration principle, provides the filter parameters of practical efficiency, comparison. The technology is mainly used in power plants, metallurgy, chemical industry, oil field water treatment engineering, and achieved satisfactory results. Significance of the research on the model of water filtration equipment development and filtration theory is grearly.