Efficiency Of Water Purification Research Articles

New insights into antifouling property and interfacial mechanism in photo-Fenton membrane distillation

Membrane distillation (MD), boasting high interception efficiency and low operational pressures, emerges as an innovative membrane technology. However, the occurrence of membrane fouling due to interaction between natural organic matter (NOM) and inorganic ions during the MD process curtails water purification efficiency, thereby constraining its potential applications. To address this quandary, this study integrates sulfate radical-based advanced oxidation processes (SR-AOPs) into MD technology to bolster membrane fouling control. A straightforward hydrothermal method coupled with vacuum filtration was employed to synthesize a Co3O4/Nitrogen-modified carbon quantum dots (NCDs)/PVDF (CN-PVDF) membrane for the first time, which was utilized in the MD treatment of simulated humic acid (HA) wastewater. Under visible light irradiation (1.9 kW/m2), CN-PVDF membrane activation of peroxymonosulfate (PMS) effectively altered the chemical attributes of the MD feed solution and reduced organic matter concentration. Moreover, it dismantled the carboxyl sites on HA that interact with Ca2+, consequently attenuating the formation of organic–inorganic complex pollutants. The XDLVO analysis showcased that photo-Fenton oxidation led to a diminishment in pollutant hydrophobicity, correlating with a 17.59 kT reduction in pollutant-membrane adsorption and a 7.47 kT amplification in adhesion barriers. This strategy transformed the initial two-stage fouling mode into a singular one, which significantly decreased the flux decline and the fouling layer thickness. Furthermore, the CN-PVDF membrane demonstrated self-cleaning capabilities via photo-Fenton. This study advances an innovative approach to bolster the fouling resistance of MD membranes and provides substantial theoretical support for the integration of SR-AOPs and MD technologies.

Underwater light source changes microecosystem constructed by Vallisneria spinulosa Yan for water restoration: Efficiency of water purification, characteristics of growth, and rhizosphere

Submerged macrophytes are effective in ecological restoration of water bodies polluted by nitrogen and phosphorus, and its restoration capacity depends on underwater illumination condition. This study explored the influencing mechanism of illumination on Vallisneria spinulosa Yan (V. spinulosa Yan) for water restoration. Addition of underwater light source increased the total nitrogen, ammonia nitrogen, total phosphorus, and phosphate removal loads of the V. spinulosa Yan growth system by 61.5, 39.2, 8.5, and 5.0 mg m−2 d-1, respectively. Meanwhile, the growth of V. spinulosa Yan was obviously promoted, even with high water turbidity. Although the biological nitrogen removal processes were inhibited by adding underwater light source, the growth of V. spinulosa Yan can be significantly improved, thus enhancing the efficiency of water purification via the absorption of nitrogen and phosphorus by V. spinulosa Yan. This study provides a theoretical foundation and technical support for application of submerged macrophytes in ecological water restoration.

Preparation of complex titanium-containing coagulants from large-scale mineral concentrates and their use in wastewater treatment

Relevance. Development of new, highly effective reagents for treatment of wastewater of various origins is a complex and extremely important task. An equally pressing issue remains the development of technologies for processing large-scale mineral products, which currently have not found an economically feasible technology for their processing and have received the status of “waste”. The development of a technology for producing reagents using waste as a raw material will not only have an economic effect but will also significantly minimize the level of negative impact on the environment and take a step towards the implementation of the Zero Waste concept. Aim. Development of technology for processing large-scale titanium-containing raw materials to obtain complex titanium-containing reagents and study of their effectiveness in wastewater treatment from various industries. Methods. To study the phase composition of the samples, the X-ray diffraction method was used, and the determination of metal content in acidic solutions and wastewater was carried out by atomic emission spectroscopy. Results and conclusions. The authors have proposed the technology for production of complex titanium-containing coagulants, which includes hydrometallurgical technology for sulfuric acid processing of large-capacity mineral raw materials – titanite. Aluminum hydroxide was introduced into the resulting solutions to adjust the chemical composition and neutralize free sulfuric acid. The resulting aluminum sulfate transforms into the most stable form of 18-aqueous crystalline hydrate, absorbing moisture from the solution, realizing chemical dehydration. The study of the composition of solid samples of coagulants showed that the predominant phase in the composition of the complex coagulant is aluminum sulfate, and the content of titanium compounds ranges from 1 to 14 wt %. It was established that by varying the ratio of mineral raw materials:sulfuric acid it is possible to vary the amount of modifying additive titanium compounds in the complex reagent. It was proven that the use of complex titanium-containing coagulants in wastewater treatment allows reducing the consumption of coagulants by 25–35%, increasing the efficiency of water purification, minimizing residual concentrations of pollutants, and also significantly increasing the rate of sedimentation of coagulation sludge in comparison with traditional sulfate aluminum.

Application of coagulation-microfiltration for membrane fouling mitigation in highly saline dyeing wastewater: Anti-fouling modification of membrane and novel insight of salt into regulation of cake layer formation

Cake layer formation is the dominant microfiltration (MF) membrane fouling mechanism after long-term operation. The regulation of cake layer characteristics is less clarified in the coagulation-microfiltration (CMF) technique due to an incomplete understanding of flocculation mechanism; however, gaining such insight will contribute to improving MF efficiency for water purification. Herein, an antifouling MF membrane for high saline textile wastewater was constructed using polydopamine (pDA) co-deposition with sodium p-styrenesulfonate (SS), and methoxypolyethylene glycols (mPEG). Thereafter, the cake layer formation in the CMF technique could be precisely regulated by adjusting salt concentration (NaCl or Na2SO4). Results indicated that the inorganic salt-induced transformation of flocculation mechanism endows a desired regulation of cake layer characteristics, consequently leading an increase in membrane flux. Various properties and formation of flocs were caused via different flocculation mechanisms (from predominant charge neutralization to integrated interaction) in response to a salt variation, giving rise to a directed transition behavior of cake layer formation from compact to porous structure. Particularly, the coagulation mechanism was validated by the experimental analysis and molecular dynamics simulations. Furthermore, the high salt permeation (>90%) and acceptable dye rejection (>98%) of two commercial reactive dyes could be obtained by the proposed CMF technique, exhibiting a satisfactory fractionation behavior of dyes/inorganic salt. A beneficial contribution is the direct reuse dyeing of NaCl from the spent dyeing bath in new dyeing operations. These results could provide a further understanding of the underlying mechanisms of coagulation-enhancing MF behavior and inspire the precise regulation of cake layer characteristics to achieve efficient MF.

Comparison and Management of Water Purification Efficiency of Artificial Wetland according to Inflow Water Conditions: Focusing on the Gyeongancheon Basin

Comparison and Management of Water Purification Efficiency of Artificial Wetland according to Inflow Water Conditions: Focusing on the Gyeongancheon Basin

Enhancing Uptake Capability of Green Carbon Black Recycled from Scrap Tires for Water Purification

This study reports on the highly simple fabrication of green carbon black (GCB) generated from scrap tires with acetic acid to improve the adsorption efficiency for water purification, which is thoroughly compared with conventional carbon black (CB) obtained from petrochemicals. Unlike traditional modification processes with strong acids or bases, the introduction of a relatively mild acid readily allowed for the effective modification of GCB to increase the uptake capability of metal ions and toxic organic dyes to serve as effective adsorbents. The morphological features and thermal decomposition patterns were examined by electron microscopy and thermogravimetric analysis (TGA). The surface functional groups were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The structural information (ratio of D-defects/G band-graphitic domains) obtained by Raman spectroscopy clearly suggested the successful fabrication of GCB (ID/IG ratio of 0.74), which was distinctively different from typical CB (ID/IG ratio of 0.91). In the modified GCB, the specific surface area (SBET) gradually increased with the reduction of pore size as a function of acetic acid content (52.97 m2/g for CB, 86.64 m2/g for GCB, 102.10-119.50 m2/g for acid-treated GCB). The uptake capability of the modified GCB (312.5 mg/g) for metal ions and organic dyes was greater than that of the unmodified GCB (161.3 mg/g) and typical CB (181.8 mg/g), presumably due to the presence of adsorbed acid. Upon testing them as adsorbents in an aqueous solution, all these carbon materials followed the Langmuir isotherm over the Freundlich model. In addition, the removal rates of cationic species (>70% removal of Cu2+ and crystal violet in 30 min) were much faster and far greater than those of anionic metanil yellow (<40% removal in 3 h), given the strong electrostatic interactions. Thus, this work demonstrates the possibility of recycling waste tires in the powder form of GCB as a cost-effective and green adsorbent that can potentially substitute traditional CB, and the modification strategy provides a proof of concept for developing simple fabrication guidelines of other carbonaceous materials.

Comprehensive effects of microplastics on algae-laden surface water treatment by coagulation-ultrafiltration combined process: Algae cultivation, coagulation performance and membrane fouling development

In coastal areas, the surface water has been simultaneously exposed to the algae blooms caused by eutrophication and the microplastics (MPs) pollution originating from active human activities. As a practical alternative to address these issues in drinking water plant, coagulation-ultrafiltration combined process is still confronted with the limited understanding about the comprehensive effects of MPs on algae-laden surface water (ASW) treatment. Considering the migration of MPs in nature environment and drinking water treatment process, this study first aims to systematically investigate the influence of MPs on algae cultivation, coagulation performance and membrane fouling development. The results of algae cultivation indicate that MPs stimulated the algae activity by 58 % and then constantly suppressed the secretion of protein-like, humic-like and polysaccharide-like metabolites. The variation of particle size distribution and zeta potential confirm that MPs acted as nuclei to facilitate the development of large coagulation flocs with an increasing average size from 82.6 μm to 107.6 μm, during which the negatively charged pollutants were neutralized and removed from ASW. According to the SEM images, MPs could destroy the structure of fouling layer on 50 kDa membranes during the filtration of ASW coagulation effluent. Its synergistic effect with the enhanced coagulation performance and the suppressed EOM secretion contributed to the alleviation of membrane fouling caused by overlapped large-sized foulants. However, the interaction between the enriched organic foulants by MPs and the deposited coagulants on 300 kDa membranes facilitated the development of cake layer, leading to the deterioration of membrane permeability. This study emphasizes the importance in concerning the existence of MPs during the treatment of ASW by coagulation-ultrafiltration combined process and their exact influence in water purification efficiency.

EXPRESS CALCULATION OF OXYGEN REGIME IN WASTEWATER FACILITIES

Problem statement. The efficiency of biological water purification depends significantly on the concentration of dissolved oxygen in the volume of the bioreactor. But during the operation of bioreactors, the oxygen regime changes, so it is important to predict the oxygen concentration for different modes of operation of treatment plants. Simplified mathematical models are used to calculate the oxygen regime, but these models are designed for typical bioreactors. An important task is the development of effective multivariate numerical models for evaluating the oxygen regime in reactors of different geometric shapes, which differ from “classical” reactors. The purpose of the article. Development of a CFD model for operational evaluation of the oxygen regime in bioreactors. Methodology. For mathematical modeling of the oxygen regime in the bioreactor, a two-dimensional mass transfer equation is used, which takes into account the place of oxygen supply from the aerator located in the building, the hydrodynamics of the flow in the bioreactor, and the diffusion process. The potential motion model was used to solve the hydrodynamic problem. Numerical integration of modeling equations is carried out by using finite-difference splitting schemes. At each splitting step, the difference equations are solved using explicit schemes. This allows a simple computer implementation of the numerical model. Scientific novelty. A multifactor two-dimensional CFD model was developed, which allows for a quick assessment of the oxygen regime in a bioreactor used for wastewater treatment. Practical significance. The developed CFD model and computer code can be used at the stage of designing or re-engineering bioreactors in order to find the optimal location of aerators in the structure. Conclusions. The software implementation of the developed numerical model was carried out. The results of a computational experiment on the study of the wastewater treatment process in a sedimentation tank are presented.

A cationic radical metal–organic framework enabling low water evaporation enthalpy and high photothermal conversion efficiency for solar-driven water purification

An innovative solar evaporator, combining Cu foam with a cationic radical MOF (PFC-771) as the photothermal absorber, demonstrates rapid and efficient solar energy-driven water evaporation.

Research on the performance and kinetics of nitrogen and phosphorus removal in composite ecological floating beds

The water purification efficiency of the traditional ecological floating beds (EFB) is unstable, and their ability to remove nitrogen and phosphorus is easily influenced by factors such as environmental temperature and microbial quantity. This study introduces inorganic electron donors and biofilm carrier materials into the EFB system, constructing Iron-Carbon Composite EFB (ICEFB), Sponge Iron Composite EFB (SIEFB), Zeolite Composite EFB (ZEFB), and Bio-ball Composite EFB (BEFB). The experiment investigates the water purification performance of each EFB at different temperatures and examines the water purification capabilities of the sponge iron-zeolite composite system through column experiments. Additionally, the nitrogen and phosphorus removal kinetics of the EFB system and the nitrogen and phosphorus removal processes of the filler system (Sponge iron-Clinoptilolite filling system) under column experiments are analyzed. The results indicate that the nitrogen and phosphorus removal performance of SIEFB and ICEFB, which are coupled with inorganic electron donors and biofilm carrier fillers, surpasses that of ZEFB and BEFB. Under the conditions of 20–30 °C, SIEFB and ICEFB achieve maximum removal rates of 99.33% and 99.27% for NH4+-N, and 64.42% and 52.22% for TN, respectively. The maximum removal rates and removal loads for TP reach 89.35%, 80.92%, and 10.73 g/(m3∙d), 9.54 g/(m3∙d), respectively. Additionally, column experiments demonstrate that the addition of sponge iron enhances the phosphorus removal rate of the zeolite filling system. The nitrogen and phosphorus removal processes of the four EFB systems can be well-fitted by utilizing a first-order kinetic model based on the Arrhenius equation and the Monod kinetic model. Anticipating that this research could further perfect the application of ecological floating bed technology in water treatment, and contribute to the restoration efforts of water environments.

(Invited) Non-Uniformly Polarized Reactive Electrochemical Membrane (REM) for Water Purification

A novel flow-through electrochemical technology (or termed reactive electrochemical membrane, REM) developed from porous electrode materials has recently attracted increasing attention globally in water purification and environment remediation. REM systems compress the boundary diffusion layer on the surface of the electrode via a combination of the convection of the solution and the constraint effect of the micro-pore structure, thus overcoming the mass transfer limitation in traditional flow-by systems. As a result, the kinetics of contaminant separation and conversion in a REM system increases by several to tens of times as compared with the flow-by systems. However, most existing studies are focused on the development of novel electrode materials, the evaluation of the removal efficiency and mechanism for contaminants, and the optimization of the treatment process of a REM system. In comparison, there is a gap in understanding the working principles of the REM electrodes. In contrast to the traditional flow-by system, the convective transport of the solution in the REM system drives the contaminants to the inside of the REM electrode, which activates the inner catalytic zone thereby. Because the electrode features the characteristics of non-uniform polarization, the given potential decays continuously along the depth of the REM electrode, thus causing a non-uniform distribution of the potential inside the REM electrode. As such, the zero-dimensional reaction theory of the electrode in traditional flow-by system (that is, the reaction mainly occurs on the surface of the electrode and is controlled by the potential) is no longer applicable to REM electrodes. It is therefore vital to revisit the reaction mechanism of the REM electrode. This Presentation therefore discusses the non-uniform polarization characteristics of the REM electrodes that are developed by loading catalytic layer on porous substrates. The main contents include: (1) REM electrode d emonstrates non-uniform oxidation characteristics: The key influencing factors ( i.e. , the pore structure of the REM electrode and the concentration of the electrolyte) and their principles of action to determine the reaction depth of a REM electrode have been identified, by employing (1) a developed mathematical model that could describe the spatial overpotential distribution as a function of depth in the REM electrode and (2) a visualization method to characterize the reactive depth of a REM electrode. (2) There is a structure-function relationship between the REM electrode pore structure and water purification efficiency : A series of SnO2-Sb-REMs with pore diameters in a range of 4.7 to 49.4 μm have been prepared to study the influence of the key factor ( i.e. , pore structure) on the transport-oxidation process of typical antibiotics. The REM electrode performance that could not constantly increase with a decrease in the pore diameter relates to the decreasing reactive depth of the electrode at a smaller pore diameter, which would lead to the compromise of the intrinsic kinetics of a REM electrode. (3) Direct electron transfer (DET) dominates the oxidation of antibiotics by using REM developed from porous substrates with a catalytic layer: The mechanism of typical antibiotics removal by employing SnO2-Sb-REM, β -PbO2-Sb-REM and Ti4O7-REM has been systematically investigated. The non-uniform oxidation characteristics of the REM electrode resulted in the DET rate being much higher than the yield of the hydroxyl radical (•OH), which was insignificantly affected by the electrode materials. The strong DET ability enabled the REM system to quickly and efficiently degrade antibiotics, which also imparted the REM system a stronger resistance to the background matrix (such as Cl–, HCO3 – and natural soluble organic matter).

Analysis of the spatial association network structure of water-intensive utilization efficiency and its driving factors in the Yellow River Basin

Achieving the efficient, synergistic and sustainable utilization of water resources is a necessary precondition and an important means through which to protect the ecological environment of the Yellow River Basin (YRB) and promote the high-quality development of the basin's economy. This paper innovatively defines water-intensive utilization efficiency (WIUE) and constructs an appropriate evaluation index system. A superefficiency network slacks-based measure (SBM) model is introduced for measurement. The gravity model is improved, and the spatial clustering and spatial association network characteristics of water use efficiency (WUE) and water conservation and purification efficiency (WCPE) are analysed using exploratory spatial data analysis (ESDA) and social network analysis (SNA). Finally, the formation mechanism of the spatial network of WCPE is explored by using quadratic assignment procedure (QAP) regression. The following conclusions are obtained. (1) The WIUE of the YRB shows a divergent trend over time, with fluctuations in the water conservation and purification stage being the main factors influencing WIUE changes in each province. (2) Currently, the spatial association network structures of WUE and WCPE are sparse. However, with the government's basin-wide water conservation policy, the spatial relationships within the basin have gradually become more closely linked. The local clustering effect of WUE in space and the communication of technical elements in the WCPE stage in the basin are the main reasons for this network formation. Focusing on the WCPE stage, this study not only proposes policy suggestions to improve the efficiency of water resource intensification in the YRB by promoting the exchange of factors but can also be used as a reference for other basins with great regional differences.

The Effect of High-Energy Ball Milling of Montmorillonite for Adsorptive Removal of Cesium, Strontium, and Uranium Ions from Aqueous Solution

Clay minerals are widely used to treat groundwater and surface water containing radionuclides. In our study, the method of mechanochemical activation for increasing the sorption capacity of the natural clay mineral montmorillonite was used. By adjusting the grinding time, the increasing sorption parameters of mechanochemically activated montmorillonite were determined. X-ray diffraction method, scanning electron microscopy, and the determination of the specific surface by low-temperature adsorption–desorption of nitrogen to characterize the natural and mechanochemical-activated montmorillonites were used. It was established that the maximal sorption of uranium, strontium, and cesium is found for montmorillonite after mechanochemical treatment for 2 h. It is shown that the filling of the surface of montmorillonite with ions of different natures occurs in various ways during different times of mechanochemical treatment. The appropriateness of the Langmuir and Freundlich models for the sorption parameters of uranium, strontium, and cesium ions on montmorillonite after its mechanochemical activation was established. The effect of natural organic substances—humic acids—on the efficiency of water purification from uranium on mechanoactivated montmorillonite was studied. The obtained sorbents can be effectively used for the removal of trace amounts of radionuclides of different chemical natures (uranium, cesium, and strontium) from polluted surface and ground waters.

Evaluation of the electroflotation efficiency for the oil-containing shipping waters treatment

The article describes the problems of formation and purification of ship oil-containing waters. The effectiveness of electroflotation using aluminum and iron anodes for the extraction of oil from water-oil emulsions with different mineralization was assessed.
 Electroflotation treatment of water-oil solutions provides 98.6–99.9 % oil removal using aluminum or iron electrodes at an anodic current density of 1.65–7.39 A/dm2 for highly mineralized waters and 0.07–0.50 A/dm2 for fresh water.
 Water treatment during the first 15 minutes provides a sharp decrease in oil content from 100 mg/dm3 to 1.31–2.52 mg/dm3, almost regardless of the type of anode metal. The efficiency of oil extraction from water mainly depends on its mineralization. In mineralized (salty) water, the treatment process is more efficient. In fresh waters, aluminum anode provides higher water purification efficiency compared to iron anode. However, in the case of pre-treatment of the iron anode with an alkali solution with the formation of a magnetite layer on it, this anode is characterized by the highest purification efficiency for low-salt waters, providing a degree of water purification at the level of 99.9 %.

Superior solar water purification achieved by the excellent photothermal conversion and thermal management of porous plasmonic TiN nanoparticles

Solar photothermal steam generation promises decentralized water purification, but the lack of materials that have strong sunlight absorption in wide spectral range, superior thermal management, large specific surface area as well as good water wettability limits the overall solar water purification efficiency. Herein, porous TiN nanospheres are prepared for solar water purification. The monodispersed porous TiN nanospheres are prepared through the wet-chemistry synthesis of TiO2 and followed nitridation. The prepared porous TiN nanospheres have relatively large specific surface area and very good hydrophilicity. In comparison with solid TiN nanospheres, the porous counterparts have stronger light absorption and better thermal management. The optimum solar evaporation film prepared with the porous TiN nanospheres and filter membrane (TiN/FM) exhibits a reflectance smaller than ∼ 19% in the entire solar spectrum. All these merits of the porous TiN nanospheres give rise to a water evaporation rate of 1.68 kg m-2 h−1 and a solar-steam conversion efficiency of 93.4% under AM 1.5 irradiation. Both seawater and polluted water can be purified to potable water with TiN/FM. Our work not only provides a preparation approach for monodispersed porous TiN nanospheres but also demonstrates the great potential of porous plasmonic nanoparticles for the future development of solar water purification.

Graphitic carbon nitride membranes intercalated with nano-sized Fe-MOF for enhanced water purification via synergistic separation and Fenton-like processes

Versatile two-dimensional nanomaterials have offered a promising prospect to enhance the water purification efficiency and overcome the fouling obstacle in membrane technology. In this work, a graphitic carbon nitride (g-C3N4) nanosheet membrane intercalated with the nano-sized Fe-based metal-organic framework (MIL-100(Fe)) is developed for the enhanced removal of aqueous organic contaminants by synergically promoting separation and Fenton-like processes. The g-C3N4/MIL-100(Fe) membrane is constructed through a self-assembly route in which the nano-MIL-100(Fe) is anchored into g-C3N4 layers by the coordination bonds between Fe nodes and pyridinic N. The MIL-100(Fe) intercalation not only enlarges the interlayer spacing to raise the membrane permeability, but also expedites the electron transfer between Fe2+ and Fe3+ to improve the Fenton-like activity. With a stable water flux of 98.2 L m2·h−1·bar−1 under wide-range pH and pressures, the g-C3N4/MIL-100(Fe) membrane shows high dye removal efficiency (≥99%) and prominent self-cleaning ability. Mechanism insight proposes a combination of size exclusion, electrostatic interaction and steady radical generation. The intercalation of nano-MIL-100(Fe) into g-C3N4 membranes can realize the mutual promotion between separation and Fenton-like processes, the synergistic effect of which provides an effective and feasible strategy for aqueous pollution abatement.

Optimizing coupling effect of confined FeNi nanoalloys within graphitic carbon nanofibers to improve photothermal energy conversion efficiency for solar water purification

Sustainable and energy-efficient water purification by harnessing solar energy is critical to tackling the challenges of water scarcity and the on-going water pollution crisis. Nevertheless, the biggest challenge to the practical deployment of solar-driven water purification, however, continues to be the poor solar evaporation efficiency of materials. Herein, FeNi nanoalloys encapsulated in graphitic carbon nanofibers (FeNi3/CNF) using Prussian blue analogue (PBAs) derivatives were fabricated using electrospinning and carbonization. The PBAs metal precursors play a critical role in encapsulating and safeguarding the FeNi alloy nanostructures from oxidation and agglomeration challenges. Furthermore, the synergistic effects between the non-noble hybrid plasmonic nanoalloys and graphitic CNFs can be constructed and optimized from the mass loading of PBAs precursor. Benefiting from the broad solar absorption band, high specific surface area, abundant micro-mesopores, and well-organized interlayer channel, the resultant 2D FeNi3/CNF solar evaporator demonstrates an efficient water evaporation rate of 1.51 kg m-2h−1 with an outstanding solar evaporation efficiency of 93.3 % under one sun irradiation, among the best values reported thus far. Impressively, the resultant 2D FeNi3/CNF solar evaporator can be constructed using only 0.02 kg m−2 loading of photothermal materials without compromising evaporation performance, which highlights its cost-efficiency in the practical application. Furthermore, the desalinated water meets the drinking standards of the World Health Organization (WHO) with an efficient 99 % separation of multiple organic industrial dye pollutants. Hence, this work demonstrates an efficient cost-effective approach to novel non-noble plasmonic alloy-based metal–carbon composites for enhanced solar-driven interfacial evaporation and wastewater purification.

Purification of Industrial Effluent by Gas Hydrate-based (HyPurif) Process

This study presents a sustainable HyPurif process for managing and recycling industrial water effluent, utilizing gas hydrate-based technology to purify complex effluent. This work purifies two effluents: one from a wastewater treatment plant (WWTP) and the other from a spent caustic treatment plant (SCTP). Various hydrate formers, including propane, HFC134a, and cyclopentane (6 mol %), were selected, as they typically form hydrates closer to ambient conditions. Hydrate formation experiments with effluent water were performed at 278.30 K using pure propane and HFC134a gas. Based on the kinetics of hydrate growth, the study was extended to a mixture (50:50%) of propane and HFC134a, operating at a pressure of 0.6 MPa. The mixture of propane and HFC134a has shown the desired result of forming the hydrate in the gas phase and having high separation efficiency. The results showed that the formation and dissociation of hydrates resulted in a separation efficiency of 80–95%. For instance, in the purified water, the biological oxygen demand (BOD) decreased from 2097 mg/L in the effluent sample to 220 mg/L in purified water (purification efficiency of 90.5%). The chemical oxygen demand (COD) decreased from 3100 mg/L in the effluent sample to 503 mg/L in purified water (purification efficiency of 84%). Total dissolved solids (TDS) were reduced from 89,632 mg/L in the effluent water to 14,698 mg/L in purified water (purification efficiency of 84%). Total suspended solids (TSS) were reduced from 35 mg/L in the effluent water to 3.5 mg/L in purified water (purification efficiency of 90%). However, the purification efficiency for free ammonia and residual chlorine was lower. The concentration of free ammonia decreased from 7 mg/L in the effluent sample to 1.89 mg/L in the purified water (purification efficiency of 73%), and residual chlorine reduced from 0.8 mg/L in the effluent sample to 0.2 mg/L in the purified water (purification efficiency of 75%). Water recovery of ≥40% was achievable per pass, which could be increased, but at the expense of purification efficiency. To the best of our knowledge, this is the first study on the purification of such complex wastewater containing organic and inorganic compounds, heavy metals, and various minerals using the HyPurif process.

Influence of water quality factors on cake layer 3D structures and water channels during ultrafiltration process

The three-dimensional (3D) structure of the cake layer, which could be influenced by water quality factors, plays a significant role in the ultrafiltration (UF) efficiency of water purification. However, it remains challenging to precisely reveal the variation of cake layer 3D structures and water channel characteristics. Herein, we systematically report the variation in the cake layer 3D structure at the nanoscale induced by key water quality factors and reveal its influence on water transport, in particular the abundance of water channels within the cake layer. In comparison with pH and Na+, Ca2+ played more significant role in determining cake layer structures. The sandwich-like cake layer, which was induced by the asynchronous deposition of humic acids and sodium alginate (SA), shifted to an isotropic structure when Ca2+ was present due to the Ca2+ bridging. In comparison with the sandwich-like structure, the isotropic cake layer has higher fractions of free volume (voids) and more water channels, leading to a 147% improvement in the water transport coefficient, 60% reduction in the cake layer resistance, and 21% increase in the final membrane specific flux. Our work elucidates a structure-property relationship where improving the isotropy of the cake layer 3D structure is conducive to the optimization of water channels and water transport within cake layers. This could inspire tailored regulation strategies for cake layers to enhance the UF efficiency of water purification.

Novel BiVO4/SiC/Cu2O ternary composite photocatalyst coupled with carbonized wood for simultaneous water evaporation and purification driven by solar energy

This work reported a novel BiVO4/SiC/Cu2O photocatalyst (BSC), and investigated the microstructure, elemental composition and photoelectrochemical properties of the ternary composite photocatalyst. Compared with pure BiVO4, BSC exhibited enhanced levofloxacin hydrochloride (LEF) degradation. The degradation rate of LEF can reach 85.83% within 100 min under the conditions of 25 mg BSC addition, LEF concentration of 10 mg/L and pH of 6.3. Furthermore, a monolithic photocatalyst (BSC@C-wood) was developed by coating BSC on one side of carbonized wood (C-wood), enabling water evaporation and purification. We collected clean water vapor and found that the SiC on C-wood can significantly enhance water purification efficiency due to its excellent photothermal ability. BSC@C-wood provides an alternative approach for the low-cost and high-efficiency treatment of wastewater.