Air Water Research Articles

Metal-Organic Framework Templated Z-Scheme ZnIn2S4/Bi2S3 Hierarchical Heterojunction for Photocatalytic H2O2 Production from Wastewater.

Metal-organic framework derived materials received a lot of attention due to their significant benefits in photocatalytic reactions. In this work, a Z-scheme ZnIn2S4/Bi2S3 hierarchical heterojunction is first developed by a one-pot method using CAU-17 as a template. The specific preparation method endows an intimate interface contact between these two monomers, and CAU-17-derived Bi2S3 possesses a high surface area and porosity, resulting in an efficient charge separation and O2 capture. Thus, for photocatalytic H2O2 production from the O2 reduction reaction, the ZnIn2S4/Bi2S3 heterojunction can achieve an H2O2 yield of 995µmolL-1 in pure water and ambient air under visible light, 4.5 and 4 times that of ZnIn2S4 and Bi2S3, respectively. In addition, in tetracycline solution, ZnIn2S4/Bi2S3 can degrade tetracycline with a degradation rate of 95% by photocatalysis, and at the same time, a final H2O2 production yield of 1223µmolL-1 is reached. Similarly, high yields of H2O2 are also obtained from wastewater containing o-nitrophenol, acid golden yellow, or acid red, and these pollutants are effectively degraded. This work reveals the potential of metal-organic framework-derived materials in photocatalysis, as well as provides insights into H2O2 green synthesis and wastewater treatment.

A Study on the Dilational Modulus Measurement of Polyacrylic Acid Films at Air–Water Interface by Pendant Bubble Tensiometry

The dilational modulus (E) of polymer films has been commonly measured using the oscillating ring/bubble/drop methods with an external force, and often without specifying the state of the adsorbed film. This study explores an approach where E was determined from the relaxations of surface tension (ST) and surface area (SA) of natural perturbations, in which ST and SA were monitored using a pendant bubble tensiometer. The E of the adsorbed film of PAA (polyacrylic acid) was evaluated for aqueous solutions at CPAA = 5 × 10−4 g/cm3, [MW = 5, 25, and 250 (kDa)]. The E (=dγ/dlnA) was estimated from the surface dilational rate (dlnA/dt) and the rate of ST change (dγ/dt) of the bubble surface from the natural perturbation caused by minute variations in ambient temperature. The data revealed that (i) a considerable time is required to reach the equilibrium-ST (γeq) and to attain the saturated dilational modulus (Esat) of the adsorbed PAA film, (ii) both γeq and Esat of PAA solutions increase with MW of PAA, (iii) a lower MW solution requires a longer time to reach its γeq and Esat, and (iv) this approach is workable for evaluating the E of adsorbed polymer films.

Construction of biodegradable superhydrophilic/underwater superoleophobic materials with CNF (cellulose nanofiber) fence-like attached on the surface for efficient oil/water emulsion separation

Superhydrophilic/underwater superoleophobic materials for the separation of oil-water emulsions by filtration have received much attention in order to solve the pollution problem of oil-water emulsion. In this paper, a fence-like structure on the surface of CNF/KGM (Konjac Glucomannan) materials by a simple method using CNF instead of metal nanowires was successfully developed based on the hydrogen bonding of KGM and CNF. The resulted organic CNF/KGM materials surface has outstanding superhydrophilic (WCA = 0°) in air and superoleophobicity (OCA≥151°) in water, which could separate oil-water mixtures with high separation efficiency above 99.14 % under the pressure of the emulsion itself. The material shows good mechanical properties because of the addition of CNF and has outstanding anti-fouling property and reusability. More importantly, the material can be completely biodegraded after buried in soil for 4 weeks since both of KGM and CNF are organic substances. Therefore, it may have a broad application prospect in the separation of oil-water emulsion because of its outstanding separation properties, simply preparation method and biodegradability.

Self-assembly of nanocrystal checkerboard patterns via non-specific interactions

Checkerboard lattices—where the resulting structure is open, porous, and highly symmetric—are difficult to create by self-assembly. Synthetic systems that adopt such structures typically rely on shape complementarity and site-specific chemical interactions that are only available to biomolecular systems (e.g., protein, DNA). Here we show the assembly of checkerboard lattices from colloidal nanocrystals that harness the effects of multiple, coupled physical forces at disparate length scales (interfacial, interparticle, and intermolecular) and that do not rely on chemical binding. Colloidal Ag nanocubes were bi-functionalized with mixtures of hydrophilic and hydrophobic surface ligands and subsequently assembled at an air–water interface. Using feedback between molecular dynamics simulations and interfacial assembly experiments, we achieve a periodic checkerboard mesostructure that represents a tiny fraction of the phase space associated with the polymer-grafted nanocrystals used in these experiments. In a broader context, this work expands our knowledge of non-specific nanocrystal interactions and presents a computation-guided strategy for designing self-assembling materials.

Hyporheic exchange flows in a mountainous river catchment identified by distributed temperature sensing

AbstractElevated stream temperatures under low‐flows, exacerbated by global warming, are a stressor that affects aquatic species directly or in combination with other stressors. Stream temperatures are influenced by energy fluxes across the air–water interface as well as by hydrological exchange processes occurring at the water–riverbed interface. Small‐scale stream temperature dynamics influenced by exchange flows are still underrepresented in stream temperature research. To investigate high‐resolution temperature dynamics and hydrological exchange processes at the sediment–water interface we applied fiber‐optic distributed temperature sensing (FO‐DTS) at two sites in the mountainous Kinzig catchment combined with mapping and measurement of additional environmental conditions. Two types of temperature anomalies could be observed at one site under conditions of low flow and high air temperature. Dampening effects coincided with riverine features such as pools, vegetation roots, fine sediment, and signs of streambank seepage which indicated hyporheic exchange flows. Increased heating of the substrate during the day was identified in shallow sections where sediment was exposed to the air and shading from riparian vegetation was patchy. At another site, at which the cable could not be buried because of the sediment composition, temperature anomalies in the overlying water indicated diffuse groundwater exfiltration. The results show that small‐scale processes in the hyporheic zone, low water tables, and riparian shading influence stream temperature in mountainous streams and can be identified with FO‐DTS under suitable conditions. The results improve our understanding of stream temperatures (in the hyporheic zone) and provide important information on how to improve hydrological modeling.

Characteristics and Application Analysis of a Novel Full Fresh Air System Using Only Geothermal Energy for Space Cooling and Dehumidification

To effectively reduce building energy consumption, a novel full fresh air system with a heat source tower (HST) and a borehole heat exchanger (BHE) was proposed for space cooling and dehumidification in this paper. The cooling system only adopts geothermal energy to produce dry and cold fresh air for space cooling and dehumidification through the BHE and HST, which has the advantage of non-condensate water compared to BHE systems integrated with a fan coil or chilled beam. Based on the established mathematical model of the cooling system, this paper analyzed the system characteristics, feasibility, operation strategy, energy performance, and cost-effectiveness of the proposed model in detail. The results show that the mathematical model has less than 10% error in estimating the system performance compared to the practical HST–BHE experimental set up. Under the specific boundary conditions, the cooling and dehumidification capacity of this system increases with the decrease in the air temperature, air moisture content, and inlet water temperature of the HST. The optimal cooling capacity and the system COP can be achieved when the air–water flow ratio is at 4:3. A case study was conducted in a residential building in Shenyang with an area of about 1800 m2. It was found that this system can fully meet the cooling and dehumidification demand in such a residential building. The operation strategy of the cooling system can be optimized by adjusting the air–water flow ratio from 4:3 to 3:2 during the early cooling season (7 June–1 July) and end cooling season (3 August–1 September). As a result, the average COP of the cooling system during the whole cooling season can be improved from 6.1 to 8.7. Compared with the air source heat pump (ASHP) and the ground source heat pump (GSHP) for space cooling, the proposed cooling system can achieve an energy saving rate of 123% and 26%, respectively. Considering that the BHE of the GSHP can be part of the proposed HST–BHE cooling system, the integration of the HST and GHSP for space cooling (and heating) is strongly recommended in actual applications.

Microplastics in remote region of the world: Insights from the glacier of Geladandong, China

Although microplastics have been detected in different remote areas, people are still short of knowledge for environmental background of microplastics in remote area. In this work, we collected air, snow, river and lake water samples from Geladandong region (the origin of the Yangtze River) of the Tibetan Plateau, along with microscopy and Micro-FTIR analyses. Microplastics abundance (0.13–19.8 items/L) was the low as compared with other remote areas worldwide, and the morphology of fiber and film, material of PP and PET, and size of <300 μm were the main microplastics features. Due to natural aging during the transport processes, microplastics were degrading to smaller particle in Geladandong. Air mass trajectory analysis shows microplastics in Geladandong is transferred by repeated atmospheric transport from no human activity place. All these results suggested that Geladandong is an ideal research area for environmental background value and characteristic of microplastics. In conjunction with data from other remote regions, we established the background values for microplastics in remote areas. This work provides quantitative evidence for establishing environmental quality standards, and monitoring environmental changes.

Hydrophobins: multitask proteins

Hydrophobins are small amphiphilic extracellular proteins produced by filamentous fungi; they are surface-active proteins, and their functions are mainly related to their ability to self-assemble into amphipathic monolayers at hydrophobic–hydrophilic interfaces. Depending on their hydropathy patterns and purification requirements, they are classified into class I and class II; both present eight conserved cysteines throughout their sequence, forming four disulfide bridges, which generate four loops that give stability to the protein in its monomeric and folded forms. Class I hydrophobin loops are more extended than class II hydrophobin loops, resulting in differences in assembly on divergent surfaces, additionally accompanied by conformational changes in the protein structure. In the monomer hydrophobin glycosylated form, hydrophobins are rich in β-sheet structure, while being assembled at the water–air interface increases the content of the β-sheet in their structure and is at the interface with water, and a hydrophobic solid such as Teflon also induces the formation of an α-helix structure. The monolayers generated by class I are stable structures called fibrils or rodlets, and class II only produces aggregates. Class I presents a glycosylated chain in its sequence; this causes the formation of the α-helix structure, promoting ordered assemblies, which entails their stability and high insolubility. Fibrils could be dissociated with trifluoroacetic acid and formic acid, which unfolds the protein, while 60% ethanol and 2% sodium dodecyl sulfate solutions dissociate class II aggregates.

Bilateral Production Shield Enabling Highly Efficient Perovskite Photovoltaics.

Enhancing the intrinsic stability of perovskite and through encapsulation to isolate water, oxygen, and UV-induced decomposition are currently common and most effective strategies in perovskite solar cells. Here, the atomic layer deposition process is employed to deposit a nanoscale (≈100nm), uniform, and dense Al2O3 film on the front side of perovskite devices, effectively isolating them from the erosion caused by water and oxygen in the humid air. Simultaneously, nanoscale (≈100nm) TiO2 films are also deposited on the glass surface to efficiently filter out the ultraviolet (UV) light in the light source, which induces degradation in perovskite. Ultimately, throughthe collaborative effects of both aspects, the stability of the devices is significantly improved under conditions of humid air and illumination. As a result, after storing the devices in ambient air for 1000h, the efficiency only declines to 95%, and even after 662h of UV exposure, the efficiency remains at 88%, far surpassing the performance of comparison devices. These results strongly indicate that the adopted Al2O3 and TiO2 thin films play a significant role in enhancing the stability of perovskite solar cells, demonstrating substantial potential for widespread industrial applications.

A macroscopic model for predicating stepwise crystalline swelling of montmorillonite

Bentonite, as an optimal buffer material in high-level radioactive waste (HLRW) repository, is usually unsaturated and sensitive to relative humidity (RH) conditions. Accurately modelling unsaturated crystalline swelling of bentonite is crucial for estimating the performance of a geological repository. In this study, we attempt to extend Laird model, a classical model for crystalline swelling, from saturated to unsaturated. For this purpose, a binary system that comprising air phase and water phase is introduced into Laird model, then the concept of effective diabattivity for atmosphere with a certain RH is proposed. On the basis, the net hydration repulsions under various RHs conditions can be determined. To calibrate the effective diavattivity, the oriented montmorillonite (Mt) tactoids is prepared and the RH controlled X-ray diffraction test is carried out. Moreover, a coupling approach of molecular dynamics (MD) simulation and fluctuation–dissipation dielectric theorem is employed to gain interlayer dielectric from dipolar fluctuations, which further improves the model accuracy. The novel model is validated by the experimental results for 3 typical buffer materials, including MX-80, Kunipia and FEBEX bentonites. Comparisons between the predicted and measured basal spacings indicate the proposed model can effectively capture the stepwise nature of crystalline swelling. Besides, the model also provides a quantitative approach to track the evolution of interaction energy during hydration process.

TiO2 modified basalt fiber cloth with superhydrophilicity and underwater superoleophobicity for oil-water separation

Titanium mesh, stainless steel mesh and other substrate materials for oil-water separation membranes have excellent acid and alkali resistance. However, the preparation process pollutes the environment and is costly. Therefore there is an urgent need for an economical and eco-friendly new material to replace them. Here, this research found that eco-friendly basalt fibers can replace them. In this work, superhydrophilic/underwater superoleophobic TiO2/basalt fiber cloths were prepared by solvothermal method. It has a contact angle of 0° for water in air and maximum 161° for n-hexadecane underwater. The oil-water separation efficiency was up to 99.75%, which indicated its efficient oil-water separation capability. The underwater n-hexadecane contact angle was 154° after immersing it in 6mol of HCl and NaOH for 2h respectively. This indicates that it has excellent acid and alkali resistance. And with titanium mesh, stainless steel mesh separation membrane acid and alkali resistance is not much different. However, the price is only one percent of titanium mesh. In addition, the softness of basalt fiber can be folded to enhance the pressure-bearing capacity. Therefore, this work provides a green, acid and alkali resistant, inexpensive new material for oil-water separation membranes, which has great potential in the field of oil-water separation.

Experimental investigation of storm sewer geyser using a large-scale setup

The storm sewer geyser is a process where an air–water mixture violently erupts from a manhole. Despite the low hydrostatic pressure, violent eruptions can achieve a height of tens of meters above the ground. This current study experimentally investigates large-scale violent geysers using a large air pocket inserted from a pressurized air tank. The total length of the pipe system is approximately 88 m with a 0.1572 m diameter pipe. This large-scale experiment facilitates the investigation of spontaneous geyser eruptions. This study identifies the role of air–water volume ratio and coefficient of pressure (ratio of absolute initial static pressure to initial dynamic pressure) on the geyser intensity using eruption images and pressure plots. A total of 116 cases are tested, in which the volume ratio is parametrically increased from 0 to 1.1 under various operating conditions. A geyser score is defined to quantify the geyser eruption nature based on visual observations. The key findings are as follows: first, a sharp transition in geyser intensity is observed at the critical volume ratio of 0.5, and pre-transition and post-transition intensity exhibit a linear relationship with the volume ratio; and second, the critical volume ratio linearly varies with the coefficient of pressure.

A robust and low-cost blended-fiber-based evaporator with high efficiency for solar desalination

The solar-driven interfacial evaporation (SDIE) is a clean and efficient technology to mitigate freshwater shortages. A robust and low-cost evaporator is essential for the practical implementation of SDIE systems. Herein, we design a fantastic blended-fiber-based evaporator using weaving techniques. This mixture fabric is crafted using polyethylene terephthalate fibers and linen threads. It makes full use of the excellent light absorption, tensile strength, and corrosion resistance of polyethylene terephthalate fibers. Meanwhile, the mixture fabric reserves exceptional air permeability and water supply capability of linen thread. We optimize the density of the mixture fabric by adjusting the reed count and the weft count. It is found that the combination of the 40 reed and a single weft yarn produces the most effective and stable evaporator. The optimized mixture fabric makes a good trade-off between the water supply to the evaporator and solar-thermal evaporation. As a result, the evaporator achieves a high evaporation rate and efficiency (∼1.53kg/m2/h, ~90 %) under 1 sun illumination, which surpasses most of the existing two-dimensional evaporators based on metal nanomaterials, polymers, carbon-based materials, and fabrics. Our work opens a new horizon for the development of efficient, scalable, flexible, low-cost, corrosion-resistant, and stable evaporators.

Antiadhesive, antibacterial, and anti-inflammatory sandwich-structured ZIF8-containing gauze for enhanced wound healing

Medical gauze is commonly used in clinical practice due to its low irritation, flexibility, and permeability. However, conventional gauze frequently lacks adequate antibacterial and anti-adhesion properties, and gauze that is only superhydrophobic or antibacterial seldom meets the full requirements of infected wound treatment. In this work, we report optimal air permeability, water and blood absorption, and biocompatibility, and effective antibacterial properties of a sandwich-structured gauze composed of a superhydrophobic outer layer, a zeolite imidazolate framework-8 (ZIF8) interlayer, and a superhydrophobic inner layer containing blood-drainage channels (denoted SZS gauze). Three ZIF8 interlayers, ZIF8-1, ZIF8-2, and ZIF8-3, were prepared by soaking medical gauze samples in a mixed solution of 50 mL methanol, 50 mL ethanol, and 0.25, 0.50, or 1.00 g zinc acetate before flat drying, and had Zn content of 0.28, 0.34, and 0.46at.%, respectively, and their corresponding SZS gauze samples are denoted SZS-1, SZS-2, and SZS-3, respectively. Among all gauze samples, the SZS-2 showed the highest cytocompatibility toward L929 cells and effective in vitro antibacterial ability against E.coli and S.aureus. In a rat subcutaneous inflammation model, the SZS-2 showed complete biosafety and the best antibacterial and anti-inflammatory effects against E.coli and S.aureus mixed bacteria among all gauze samples including standard medical gauze and a sandwich-structured gauze with a blank interlayer between two superhydrophobic layers. These findings indicate that the SZS-2 gauze is a promising candidate for advanced wound care, particularly in the management of infected wounds.

Physics-based modeling of the effective gas transport properties of single jersey knitted fabrics based on images

In many processes and applications, the performance of textiles relies heavily on fluid transport; for example, the in-plane distribution of water and the through-plane permeation of water vapor and air. Prediction of knitted fabrics’ effective transport characteristics can enhance development workflows and bring them to new applications. Effective transport parameters that are particularly important are the permeability and diffusive mass transfer. Usually, experiments are used to determine these parameters. It is desirable to conduct a thorough investigation into how yarn structure and knitting gauge influence these properties to tailor knitted fabrics for a particular application. Our contribution in this context describes a consistent workflow to forecast the effective mass transfer characteristics of single jersey fabrics. Single jersey fabrics have been chosen for they are the simplest patterning, and are widely used in body-near worn garments. The proposed approach involves visualizing fabric samples with a light microscope, and subsequently determining relevant geometric parameters through automated image processing algorithms. With these parameters in hand, a representative elementary volume of the fabric is constructed. The yarn is modeled as an effective medium to reduce calculation time. The representative elementary volume is then used for numerical predictions of air permeability and the diffusive water vapor transport. The predicted through-plane gas transport properties are compared with experimental data to validate the approach. Six different single jersey polyester fabrics were analyzed, with different yarn structures and machine gauges. The comparison shows a good agreement between simulated and measured transport properties.

Issue Information: Clean Soil Air Water. 5/2024

Issue Information: Clean Soil Air Water. 5/2024

High-concentration hydrogen peroxide production by solar interfacial catalysis

Solar-driven catalytic synthesis of H2O2 is an ideal alternative to the anthraquinone method, but current photocatalysts still suffer from low activity and inefficient solar energy utilization. Here we presented an economic and efficient solar interfacial catalysis system (SICS) that incorporated photothermal–photocatalytic materials into commercial sponge to simultaneously generate the required heat and carriers for H2O2 production. We demonstrated its superiority over conventional particulate photocatalysis (PC) in photocatalytic H2O2 production. The SICS, located at the air–water interface, remarkably improve the activities of photocatalysts by efficient utilization of solar-converted heat. The produced H2O2 from SICS was reserved in the sponge and resulted in an ultrahigh concentration of 46 mM for per gram catalyst after 1 h solar irradiation. As thus, our application experiments confirmed that the SICS presented great advantages in organic pollutant (e.g. phenol and tetracycline) degradation compared with conventional PC. This work paves a new way for the industrialization of solar-driven catalysis.

A multistage assembled laminar membrane for solar thermal conversion and nighttime electricity production

A multistage assembled laminar membrane for solar thermal conversion and nighttime electricity production

Striving for Sustainable Solutions: Optimizing Utility Properties of Recycled Paper with the Addition of Wet Strength Resin

Paper producers are increasingly challenged to meet customer demands for high-quality sanitary papers amidst rising price pressures and diminishing quality of recycled fibers. One promising avenue for enhancing paper quality involves augmenting wet strength. For this purpose, synthetic wet strength resins are used, among other things. This study explores the efficacy of utilizing a polyamide-epichlorohydrin resin-based agent for the internal sizing of white wastepaper. Such chemicals, when added to cellulosic fibers in proper amounts before the paper is made, can not only improve water resistance and air permeability of the finished product but also significantly affect both the dry and wet strength paper, which is a crucial aspect for sanitary papers. This study shows that the appropriate addition of resin allows the wetted recycled paper to retain even more than 30% of its dry strength, while in the dry state, the breaking strength of the paper is improved by approximately 46%. As the demand for more sustainable and resistant paper products continues to grow, the use of wet strength agents is expected to increase in the coming years, as well as the need for research in this field. This research therefore undoubtedly contributes to advancing sustainable practices within the paper industry, aligning with the principles of circular economy by optimizing the utility of recycled fibers while maintaining product quality.

ENVIRONMENT DOCTOR SYSTEM

The degradation of water resources , soil and air pollution has become a common problem. It is necessary to monitor air quality and water quality and keep it under control for a better future and healthy living for all. System uses air sensors to sense presence of harmful gases/compounds in the air and constantly transmit this data to microcontroller. System keeps measuring the parameters of water, such as temperature PH value, turbidity, flow and reports it to the online server over IOT. Also, System also measures the parameters like Soil Moisture , pH, Temperature and Humidity . This system collects data about the air , water and soil quality and determines its purity. It will send us the data about quality from a wireless network. This data will be received by a machine and it will send this data to the server. Next, the data on the server can be displayed to various clients.