Initial Water Research Articles

Experimental study on frost heave characteristics and micro-mechanism of fine-grained soil under dynamic load for heavy-haul railway subgrades in seasonally frozen regions

In seasonally frozen regions, there is frequent uneven frost heave of heavy haul railway subgrades, which reduces the smoothness of the track and affects the operational safety of trains. To clarify the frost heave characteristics and micro-mechanism of subgrade filling under the action of unidirectional freezing and dynamic loading, unidirectional freezing tests were performed on a fine-grained subgrade filling under open conditions, and the frost heave characteristics under different initial water contents and dynamic loads were analyzed. The particle image velocimetry (PIV) technique was applied to analyze the development of local deformation at different locations in the samples. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were performed on the samples before and after freezing to reveal the development mechanism of the microstructure. The test results showed that with the increase in the initial water content and load amplitude, the frost heave increased, while the water replenishment and frost depth decreased. Combined with the PIV results, it was found that the soil in the frozen and unfrozen areas exhibited frost heave and compressive deformation, respectively, during the freezing process, further revealing the local deformation law of the soil. The samples mainly contained small pores and micropores before freezing and small pores and medium pores after freezing, indicating that the effect of freezing and swelling had the greatest influence on the small and medium pores inside the soil. The higher the initial water content, the higher the porosity of the sample after freezing; with the increase in the load amplitude, the porosity of the frozen samples decreased. The negative temperature effect of the change in phase from water to ice drove the particle movement, thereby increasing the inter-particle pore space, leading to a macroscopic frost heave deformation of the soil samples. Our results can serve as a basis in the maintenance and safety of railway subgrades in cold regions.

Experimental study about solidification processes of sessile deformed water droplets on the biaxial inclined cold plate surface under natural convection

Deformed droplet solidification on inclined surfaces exists widely in engineering fields. In reality, the droplet deformation tends to occur multiple times due to many force factors, like gravity, centrifugal force etc. And the solidification characteristics would be significantly influenced by the deformations. Thus, the sessile deformed water droplet solidification on the biaxial inclined surface is experimentally investigated in this study. By tilting the surface around different axes separately, the deformations of water droplet along different directions would be caused. Then the different solidification characteristics of deformed water droplets are experimentally analyzed, including contact area, height and vertex offset, etc. As found, the effect of inclination angle becomes greater with the increase of droplet volume. When the horizontal surface is tilted to φ1 = 5° and φ2 = 40°, the contact areas increase by 18.85 % and 64.2 % for 5 μL and 20 μL water droplets, respectively. The frozen heights decrease by 17.90 % and 19.85 %. In addition, the initial sessile water droplet the position of vertex varies only in height during the solidification process, not in the horizontal direction along the surface. This study could provide the fundamental data for the model about predicting the solidification process of deformed water droplet.

Synergistic Remediation of Organic Dye by Titanium Dioxide/Reduced Graphene Oxide Nanocomposite.

In this work, nanocomposites based on titanium dioxide and reduced graphene oxide (TiO2@rGO) with different weight percentages of rGO (4, 8, and 16 wt%) were prepared by the hydrothermal/solvothermal synthesis method and thermally treated at 300 °C. The prepared nanocomposites were explored for the removal of methylene blue dye (MB) in the presence of simulated solar illumination as well as natural sunlight. The structural, morphological, chemical, and optical properties of the as-synthesized TiO2@rGO nanocomposites were characterized. The obtained results of the graphene-based nanocomposite materials indicated the existence of interactions between TiO2 and rGO, i.e., the Ti-O-C bond, which confirmed the successful integration of both components to form the TiO2@rGO nanocomposites. The addition of rGO increased the specific surface area, decreased the band gap energy, and increased the photocatalytic degradation efficiency of MB from water compared to TiO2 nanoparticles. The results of photocatalytic activity indicated that the amount of rGO in the prepared TiO2@rGO nanocomposites played a significant role in the application of different photocatalytic parameters, including the initial dye concentration, catalyst concentration, water environment, and illumination source. Our studies show that the reinforcement of the nanocomposite with 8 wt% of rGO allowed us to obtain the maximum photocatalytic decomposition performance of MB (10 mg·L-1) with a removal percentage of 99.20 after 2 h. Additionally, the obtained results show that the prepared TiO2@rGO_8 wt% nanocomposite can be used in three consecutive cycles while maintaining photocatalytic activity over 90%.

The importance of the microstructure on hydro-mechanical behaviour of compacted granular bentonite

Granular bentonite (GB) with extended grain size distribution, a candidate material to construct engineered barriers, has low water permeability, high swelling potential and self-sealing capacity and is desirable in portability and workability. However, few systematic data combining microstructural descriptions and hydro-mechanical (HM) behavioural features are available. The present work investigates the HM performance of Wyoming (MX80)-type GB samples compacted at different initial water contents and at a fixed dry density of 1550 kg/m3. The samples' microstructure and its evolution along stress paths were studied using X-ray micro-computed tomography and mercury intrusion porosimetry. The results highlighted that the compacted GB presented local density heterogeneity and a multi-porosity network. Compaction at low initial water content increased the proportion of macropores and contributed to the enhancement of the compressibility and collapse on wetting under high stresses. During isochoric saturation, two stages of swelling development were identified. First, the flooding of macropores and matric suction reduction was related to the initial increase in swelling pressure. The secondary swelling was due to the water absorption of clay sheets in micropores and the expansion of micropores within granules and aggregates, during which the density of pore water increased. A decrease in the compaction water content can result in a higher pore water density after isochoric saturation and a lower water permeability. Finally, the water retention behaviour of the compacted sample within drying/wetting cycles was less sensitive to the initial pore size distribution. The current outcomes underline the critical role of the microstructure on the HM behaviour of compacted GB.

Shear strength degradation of gas hydrate-bearing sediment due to partial hydrate dissociation

Extraction of methane hydrate from subseafloor reservoir may potentially trigger seabed slides and induce subsidence. To address the problems, it is crucial to properly characterize the phase equilibrium condition of pore hydrate and the shear strength of the soil. As one of the key constitutive components, the phase equilibrium condition enforces a constraint over pore gas pressure, temperature and unhydrated water content. Such a constraint, however, has been traditionally ignored in analyzing the mechanical behavior of hydrate-bearing soil. In this paper, a series of stepwise hydrate dissociation tests was performed, and the phase equilibrium condition of pore hydrate was determined, providing an effective way to evaluate the unhydrated water content during hydrate dissociation. Meanwhile, a series of direct shear tests was also conducted to explore the shear strength characteristics of the soil. It is shown that the shear strength of the hydrate-bearing soil can be significantly influenced by pore gas pressure, unhydrated water content, hydrate saturation and several other factors. In particular, the measured shear strength depends upon the initial water content of the sample, pointing to a potential problem that the shear strength could be wrongly determined if not properly interpreted. A shear strength criterion, which enforces the equilibrium condition of pore hydrate, is developed for hydrate-bearing soil, establishing a link between the equilibrium condition and the shear strength. The proposed equation describes well the shear strength characteristics of hydrate-bearing soils, remarkably unifying the effects of pore pressure, temperature, water content and hydrate saturation.

Recyclable oil resistant paper with enhanced water resistance based on alkyl ketene dimer modified sodium alginate

Abstract Sustainable coatings exhibit potential in enhancing oil resistance of packaging paper. Alkyl ketone dimer (AKD) was used to esterify sodium alginate (SA) to prepare water and oil resistant agent SAD. As SAD was coated on paper, it reduced the surface energy and blocked the fiber pores of paper, thus improving the barrier performance of paper. The oil resistance grade can reach grade 6 at coating amount of 2.13 ± 0.26 g/m2, which is qualified for food packaging. The coated paper also showed good barrier to hot castor oil. Resistance to organic solvent and water were also enhanced with initial water contact angle (WCA) increased to 69.2°. Compared with base paper, SAD coated paper had better mechanical properties and more importantly, coated paper can be effectively recycled to achieve green recycling.

Stabilization of Fluidic Silty Sands with Cement and Steel Slag

Fluidic silty sand is often difficult to use directly in engineering construction because of its low strength and plasticity index. This study employed steel slag to replace part of the cement in silty sand stabilization to broaden the feasibility of resource recycling and to reduce the construction cost and carbon emissions in engineering practices. A series of indoor tests investigated the influences of the cement/steel slag ratio, initial water content, curing age, and temperature on the compressive strength of cement- and steel slag-stabilized fluidic silty sands (CSFSSs). Their stabilization mechanism was discussed via microstructural observation and spectral analysis. The results showed that the most economical cement/steel slag ratio could be 9:6, saving 40% of cement and not changing with the initial water content. The compressive strength of the CSFSSs decreased with the initial water content and increased rapidly and then slowly over the curing age. The curing temperature had a positive impact on their strength growth. The microstructure characteristics and spectral analysis showed that adding steel slag indeed affected the formation of gels in the cement-stabilized fluidic silty sands. This study could reference the application of CSFSSs in engineering practices.

Investigation of the Water-Invasion Gas Efficiency in the Kela-2 Gas Field Using Multiple Experiments

Although improving the recovery of water-invaded gas reservoirs has been extensively studied in the natural gas industry, the nature of the efficiency of water-invaded gas recovery remains uncertain. Low-field nuclear magnetic resonance (NMR) can be used to clearly identify changes in water saturation in the core during high-pressure water-invasion gas. Here, we provide four types of water-invasion gas experiments (spontaneous imbibition, atmospheric pressure, high-pressure approximate equilibrium, and depletion development water-invasion gas) to reveal the impact of the water-invasion gas efficiency on the recovery of water-invasion gas reservoirs. NMR suggested that imbibition mainly occurs in medium to large pores and that residual gas remains mainly in large pores. The amount of gas driven out from the large pores by imbibition was much greater than that driven out from the small pores. Our findings indicate that the initial gas saturation, contact surface, and permeability are the main factors controlling the residual gas saturation, suggesting that a reasonable initial water saturation should be established before the water-invasion gas experiments. Additionally, the water-invasion gas efficiency at high pressures can be more reliably obtained than that at normal pressures. After the high-pressure approximate equilibrium water invasion for gas displacement, a large amount of residual gas remains in the relatively larger pores of the core, with a residual gas saturation of 42%. In contrast to conventional experiments, the residual gas saturation and water displacement efficiency of the high-pressure approximate equilibrium water invasion for gas displacement did not exhibit a favorable linear relationship with the permeability. The residual gas saturation ranged from 34 to 43% (avg. 38%), while the water displacement efficiency ranged from 32 to 45% (avg. 40%) in the high-pressure approximate equilibrium water invasion for gas displacement. The residual gas saturation in the depletion development water-invasion gas experiment was 26–40% (average: 33%), with an efficiency ranging from 45 to 50% (average: 48%), indicating that the depletion development experiment is closer to the actual development process of gas reservoirs. Our findings provide novel insights into water-invasion gas efficiency, providing robust estimates of the recovery of water-invasion gas reservoirs.

Evaluating soil water movement and soil water content uniformity under sprinkler irrigation with different soil texture and irrigation uniformity using numerical simulation

Water movement and its distribution uniformity in the soil are essential for the design of sprinkler irrigation systems. They are both crucial factors influencing nutrient migration and the productivity of crops. In this study, a new numerical simulation method was proposed to investigate the soil water movement in sprinkler irrigation under nonuniform infiltration boundary conditions using COMSOL software. Besides, two soil tank experiments were conducted to test the reliability of the simulation model. Finally, the model was applied to evaluate the effects of sprinkler irrigation uniformity, soil texture, and initial soil water content on soil wetting patterns and soil water content uniformity. The results showed that the COMSOL-2D predictions of the vertical wetting fronts were in good agreement with the experimental data. The soil texture and initial soil water content influenced the soil wetting pattern and the risks of surface runoff and deep percolation in sprinkler irrigation systems. When the water application rate was 11.35 mm h−1 with an irrigation duration of 10 h, it was easy to cause surface runoff in silty clay loam while deep percolation in loamy sand. Additionally, when the initial soil water content is high, it should be better to avoid irrigation or cut down the irrigation duration to prevent percolation. The water within the soil was more uniformly distributed than that applied through a sprinkler irrigation system. The uniformity coefficient of soil water content distribution (CUs) increased from 87.75 % to 95.56 %, as the uniformity coefficient of sprinkler irrigation (CU) increased from 40.74 % to 82.41 %. Although a higher initial soil water content brought a higher soil CUs value, it also led to a higher risk of percolation. The experimental and simulation results indicated that the COMSOL-2D model could be used to accurately simulate soil water movement in sprinkler irrigation and determine the suitable operation mode of low-pressure sprinklers.

Experimental Investigation of the Water Droplet Evaporation on Inclined Surfaces by Taguchi and ANOVA Optimization Analysis

Abstract We experimentally investigated the evaporation characteristics of a sessile water droplet on a glass substrate with different surface roughness levels. The influence of five parameters is evaluated for the evaporation process: substrate temperature (30 °C, 45 °C, and 60 °C), surface roughness (P0, P600, and P60), droplet volume (3, 5, and 8 µL), water droplets initial temperature (30 °C, 40 °C, and 60 °C), and inclination angle (0 deg, 45 deg, and 75 deg) of the glass substrate. The Taguchi orthogonal array design of L27 is utilized to establish minimal candidate trial points for experimental works, and more trials have been conducted to quantify the effects accurately. Then, analysis of variance (ANOVA) has been used to evaluate the evaporation times for the sessile droplets. The results indicate that evaporation times decrease with rising substrate temperatures, increasing substrate inclination angle, and increasing initial water droplet temperatures. In contrast, evaporation times rise with increasing surface roughness and droplet volumes. After evaluation of the ANOVA analysis, surface roughness levels and droplet volumes are considered the most influential parameters after substrate temperatures, which is the most effective parameter on the evaporation times. On the other hand, initial water droplet temperatures and substrate inclination angle are less effective considering droplet evaporation times. A linear regression fit was derived via ANOVA analysis for the evaporation time, and the best mean deviation was found to be 10% from the experiments. The experimental outcomes were compared to previous research, and correlations were derived. The proposed correlation has given good results considering experimental and literature data.

Role of reactive oxygen species and antioxidative enzymes in the loss and re-establishment of desiccation tolerance in germinated pea seeds

This study highlights the regulatory function of ROS and its detoxifying enzymes during the loss and re-establishment of desiccation tolerance (DT) in PEG pretreated and untreated germinated pea (Pisum sativum L.) seeds with 2 mm long radicles. Dehydration of untreated pea seedlings to initial water content (IWC; 0.11 gH2O g−1 DM) and below IWC (0.06 gH2O g−1 DM) reduced the DT to 60 and 20 %, respectively. Significant amelioration in DT was observed in PEG pretreated seedlings by ∼100 % and 70 % following dehydration at IWC and below IWC, respectively. Rendering DT in the PEG pretreated seedlings was negatively associated with an extensive reduction in superoxide (∼2.3 folds) and H2O2 (∼1.8 folds) levels compared to the untreated seedlings. Enhanced expression, levels (quantitative) and number (isoenzyme) of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in the PEG pretreated seedlings negatively correlated with the lowering ROS levels and its associated oxidative damage. It is concluded that the re-induction of increased antioxidative capacity is a key factor in the re-establishment of DT in PEG-pretreated pea seedlings. Additionally, PEG pretreatment resulted in 50 % disappearance of superoxide in the sub-apical zone (SZ) of the radicle compared to the radicle of untreated seedlings dehydrated below IWC. Further, in situ detection of superoxide accumulation in the apical zone (AZ) was NADPH-oxidase dependent but in the SZ it was independent of NADPH-oxidase. Our results showed that the osmotic stress induced the expression of antioxidative enzymes in germinated pea seeds and made them desiccation tolerant against oxidative stress caused by desiccation/drought.

Green composite sponge of natural rubber reinforced with cellulose filler using alginate as a dispersing agent

Composite sponges of natural rubber and cellulose fiber (NR-C) using sodium alginate (SA) as a dispersing agent were successfully fabricated by the Dunlop process. The aim of this work was to develop a green composite NR-C sponge with high mechanical properties and efficient water absorption capacity (WAC). The addition of SA could promote cellulose fiber dispersion in NR matrix and NR-cellulose interactions; accordingly, it resulted in highly macro-porous sponges with improved mechanical properties and higher hydrophilicity. NR-C sponge supplemented with cellulose at 45 parts per hundred rubbers (phr) and SA at 1 phr revealed significantly higher compressive stress and higher modulus of elasticity of about 5 times those of NR sponge. The maximum WAC at around 400 % was obtained from NR-C sponge supplemented with 30–45 phr cellulose and 1 phr SA. The initial water absorption rate and WAC of NR-C sponges were increased up to 5.6 and 1.8 times those of NR sponges, respectively. In addition, NR-C reinforced with high content of cellulose and SA could be sufficiently biodegraded in soil for about 21–27 % in120 days, which was considerably higher than that of NR sponges. According to their improved properties, NR-C composite sponges could be used an adsorbent or supporting material in many applications, including agriculture applications, such as a seed germination sponge or a hydroponic planting material and could also be further developed for biomedical applications as wound dressing.

Evaluation of total infiltration and storage capacities for different soil types in Sarawak using SWMM

Climate change and irresponsible urbanization practices are anticipated to further exacerbate flood risk. The different soil types’ physical, chemical, and biological characteristics significantly impact surface water movement, porosity, permeability, and infiltration potential. Therefore, soil infiltration is perhaps the most challenging and crucial process to characterize on a field scale. Various methods have been developed to measure the infiltration rate empirically and theoretically. However, the relationship between different soil types and infiltration rates in Sarawak remains unknown as no previous study has been conducted. This study uses the Storm Water Management Model (SWMM) to evaluate the infiltration rates for five different soil types: clay, clay loam, loam, sandy loam, and sand. 30 samples of various types and soil depths were examined at intervals of 0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m, and 3 m. The study was carried out using a standardized slope of 0.7% and an impervious land of 25% with a catchment size of 2 acres. Extreme rainfall data on the 5th and 6th of December 2021 was input into the infiltration model. Results showed that the difference between initial and final water storage of all the investigated soil depths for clay, clay loam, loam, sandy loam, and sand was found to be 48.42 mm, 51.20 mm, 58.01 mm, 66.96 mm, and 115.54 mm, respectively. The findings demonstrated that clay has the lowest water storage capability, followed by clay loam, loam, and sandy loam. Sand could store a comparatively large amount of rainwater. In contrast, sand has the highest infiltration rate with 2.541 mm/h, followed by sandy loam with 1.835 mm/h, loam with 1.432 mm/h, clay loam with 1.039 mm/h. Clay has the lowest infiltration rate, with 0.852 mm/h. This research concluded that sandy soil could significantly reduce surface runoff and help reduce flood risk in urban regions.

Ecological and photosynthetic characteristics of Carex schmidtii with respect to hydrological fluctuations

Hydrological fluctuations are key abiotic stresses that influence plant growth and photosynthetic processes of wetland plants. However, the response mechanism of the plant characteristics and photosynthesis of Carex schmidtii, with respect to hydrological fluctuations, are still unclear. Comparative studies of plant size parameters, biomass parameters, and photosynthesis parameters of C. schmidtii under the interactive influence of initial water depth (WD), water-level amplitude (WA), and duration time, were performed. The coupling relationship between any two factors of the plant characteristics of C. schmidtii was also examined. Generally, the results showed that the WD and WA treatments, and the duration time, significantly affected plant size, biomass, and photosynthesis of C. schmidtii. The exception was the effect by the WA on the biomass and the NPQ. Furthermore, the biomass and photosynthesis of C. schmidtii were significantly affected by the interactive effects by WD and WA. The plant size, biomass, and photosynthesis parameters of C. schmidtii first increased and then decreased over time. Larger values of plant size, biomass, and photosynthesis parameters (except for qL and NPQ) were found for the treatment with an initial water depth of 0 cm. As was the situation with WD, the largest values of plant height, chlorophyll content, Fv/Fm, and ΔFv/Fm’ were obtained for a water-level amplitude of 0 cm. Furthermore, the chlorophyll content was positively related to the plant size parameters, Fv/Fm, ΔFv/Fm’, and qL. Except for qL, ΔFv/Fm’ had a significant relationship with all plant factors. Lower water levels and smaller water level changes are more conducive to the growth and photosynthese of C. schmidtii. Plant size, biomass accumulation and photosynthesis of C. schmidtii collectively coped with hydrological fluctuations. The findings have improved understanding of the response of C. schmidtii to hydrological fluctuations. They have thereby provided invaluable information for the restoration, management and conservation of tussock wetlands.

Effect of initial water content on the dewatering performance of freeze-thaw preconditioned landfill sludge

Freeze-thawing (F/T) is an effective method of sludge dewatering preconditioning and has been studied in many studies. However, previous studies have taken landfill sludge from different regions, filled for different length of time or at different depth, resulting in large differences in initial water content and different treatment effects. Therefore, the effect of initial water content on the dewatering characteristics of F/T preconditioned landfill sludge has been investigated. The sludge with different initial water contents was firstly preconditioned by one F/T cycle. Then the F/T sludge was vacuum filtered and compared with the dewatering performance of FeCl3 preconditioned sludge with the same water content. Finally, the mechanism of the initial water content on the effect of F/T preconditioning was analyzed by the change of sludge internal composition. The results show that the higher the initial water content of the sludge, the greater the improvement of its dewatering performance after F/T preconditioning. The specific resistance and water content after filtration of sludge after F/T conditioning decreased greatly with the increase of the initial water content, reaching their respective minimum values of 13.3 × 1012 m/kg and 58.3% at 85% and 87.5%. These values are lower than the optimal values observed for the sludge conditioned by FeCl3. With the rise in initial water content, the driving force at the ice-water interface gains strength. Small particles aggregate into larger flocs, forming stable drainage channels that enhance the dewatering performance of sludge. Once the initial water content surpasses 85%, the squeezing force exerted by ice crystals amplifies the degree of cracking in sludge particles, releasing bound water and further decreasing the water content of sludge.

Influence of biochar and recycled gypsum on the strength and microstructure of conventional and sustainable cementitious composites

The need for sustainable waste management practices to mitigate climate change emphasized discovering alternatives for environmentally unfriendly materials with high carbon footprints such as ordinary Portland cement (OPC). This study examined the effect of biochar and its presoaking on the compressive strength, porosity, and microstructure of sustainable mortars containing fly ash, recycled gypsum drywall, and OPC by manufacturing and testing 270 cubic specimens, 30 mix designs, at 7, 28, and 90 days. The main roles of biochar in the matrix were to provide water and an additional surface for internal hydration, boost nucleation, and increase interlock in the cement paste. The water retention potential of biochar particles, however, could contribute to an artificial increase in the early-age compressive strength of cementitious composites (CCs) containing biochar. This strength was lessened over time as the retained water was utilized by cementitious reactions. The low strength of the biochar particles and its effect on the porosity of CCs were the primary sources of strength reduction of specimens containing biochar. The influence of biochar presoaking relied on the initial reactivity of binders. Lower initial reactivity lessened the initial water demand, increasing free water in the mixture, retained by non-soaked biochar. The highly reactive binders, however, needed extra water, which was supplied by presoaked biochar. The data also indicated the good compatibility and bond between biochar particles and the cement paste. The effect of adding biochar on the properties of CCs strongly depended on the particle size distributions of the composite constituents and biochar particles.

Research on Transformation of Connate Water to Movable Water in Water-Bearing Tight Gas Reservoirs

The Dongsheng gas field is a water-bearing tight gas reservoir characterized by high connate water saturation. During gas production, the transformation of connate water into movable water introduces a unique water production mode, significantly impacting gas reservoir recovery. Current experimental and theoretical methods for assessing formation water mobility are static and do not address the transformation mechanism from connate into movable water. In this study, we considered dynamic changes in formation stress and proposed the mechanism for the transformation of connate water into movable water during depressurization, involving the expansion of connate water films and the reduction of pore volume. We developed a novel methodology to calculate the dynamic changes in movable and connate water saturation in tight reservoirs due to reservoir pressure reduction. Furthermore, we quantitatively evaluated the transformation of connate water into movable water in the Dongsheng gas field through laboratory experiments (including formation water expansion tests, connate water tests, and porosity stress sensitivity tests) and theoretical calculations. Results show that under original stress, the initial connate water saturation in the Dongsheng gas field ranges from 50.09% to 58.5%. As reservoir pressure decreases, the maximum increase in movable water saturation ranges from 6.1% to 8.4% due to the transformation of connate water into movable water. This explains why formation water is produced in large quantities during gas production. Therefore, considering the transition of connate water to movable water is crucial when evaluating water production risk. These findings offer valuable guidance for selecting optimal well locations and development layers to reduce reservoir water production risks.

Graphene coating reduces the heat transfer performance of water vapor condensation on copper surfaces: A molecular simulation study

Water vapor condensation is a key process for many applications. Existing studies in water vapor heterogeneous condensation have used different methods to modify the hydrophobicity of the water vapor condensation surface. One way to modify the surface properties is to use graphene coating. On a macroscale, surface modification using graphene coating can improve water vapor condensation heat transfer of various substrates. However, on the molecular scale, its effect is poorly understood. This work investigated the effect of graphene coating on water vapor condensation using molecular dynamics simulations (MDS). We examined the water vapor condensation on bare copper surfaces considering the effects of initial temperature difference, water model, and surface size, parameters that have not been investigated by previous studies employing MDS for the same water-surface configuration. One water model was then used to simulate the condensation on a copper surface with and without graphene coating. We then investigated the effect of graphene defect, the energy and vibration of graphene atoms, and the interaction between graphene and copper layers. The surface size notably influenced the condensation rate and heat transfer performance. The condensation rate and heat transfer performance were significantly reduced when the copper surface was coated by graphene. The number of water molecules condensed was 1253 molecules/ns on the bare copper surface, compared to 587 molecules/ns on the graphene-coated copper surface. Moreover, the water molecules condensed on the graphene-coated copper surface tended to return to the bulk vapor phase. Other important results are also provided. This study gives an insight into the water vapor condensation on graphene-coated copper surfaces, useful to pursuit the design and optimization of graphene-coated copper surfaces for applications that need efficient water vapor condensation, such as for industrial applications, like thermal, chemical, and nuclear.

Construction of CuMoO4/MnO2/tourmaline composite for efficient organic wastewater decontamination via photo-Fenton-like processes

A CuMoO4/MnO2/tourmaline (CMT) heterogeneous photocatalyst was successfully constructed by hydrothermal method followed by calcination and applied to activate peroxymonosulfate (PMS) for organic contaminant degradation over a wide pH range under visible light illumination. The CMT catalyst exhibited impressive degradation efficiencies of tetracycline hydrochloride (TC, 93.48%), safranine T (SaT, 100%), acridine orange (AO, 99.46%), methyl orange (MO, 97.47%), neutral red (NR, 94.10%), trypan blue (TB, 93.67%), methylene blue (MB, 90.36%) and rhodamine B (RhB, 89.85%) within 50 min. The influence of related parameters including catalyst dosage, PMS concentration, initial pH value, TC concentration, coexisting ions, humic acid (HA) and different water matrices on TC degradation were systematically investigated. According to quenching experiments and electron paramagnetic resonance (EPR) tests, e−, SO4•−, •OH, •O2− and 1O2 all contributed to TC degradation, and •O2− played a predominant role in the photo-Fenton-like process. The reusability of CMT was evaluated by consecutive experiments, and comparable removal efficiencies could be maintained after five cycles. The degradation pathways of TC were deduced and the toxicity of degradation intermediates based on HPLC−MS detection was estimated by Toxicity Estimation Software (T.E.S.T.). Moreover, the catalytic degradation mechanisms of TC in CMT/PMS/Vis system were further proposed and the role of tourmaline was illustrated. This work opens an avenue for the construction of heterogeneous catalysts based on natural minerals in PMS/Vis coupling system for wastewater decontamination.

A sensorless, Big Data based approach for phenology and meteorological drought forecasting in vineyards

A web-based app was developed and tested to provide predictions of phenological stages of budburst, flowering and veraison, as well as warnings for meteorological drought. Such predictions are especially urgent under a climate change scenario where earlier phenology and water scarcity are increasingly frequent. By utilizing a calibration data set provided by 25 vineyards observed in the Emilia Romagna Region for two years (2021–2022), the above stages were predicted as per the binary event classification paradigm and selection of the best fitting algorithm based on the comparison between several metrics. The seasonal vineyard water balance was calculated by subtracting daily bare or grassed soil evapotranspiration (ETs) and canopy transpiration (Tc) from the initial water soil reservoir. The daily canopy water use was estimated through a multiple, non-linear (quadratic) regression model employing three independent variables defined as total direct light, vapor pressure deficit and total canopy light interception, whereas ETS was entered as direct readings taken with a closed-type chamber system. Regardless of the phenological stage, the eXtreme Gradient Boosting (XGBoost) model minimized the prediction error, which was determined as the root mean square error (RMSE) and found to be 5.6, 2.3 and 8.3 days for budburst, flowering and veraison, respectively. The accuracy of the drought warnings, which were categorized as mild (yellow code) or severe (red code), was assessed by comparing them to in situ readings of leaf gas exchange and water status, which were found to be correct in 9 out of a total of 14 case studies. Regardless of the geolocation of a vineyard and starting from basic in situ or online weather data and elementary vineyard and soil characteristics, the tool can provide phenology forecasts and early warnings of meteorological drought with no need for fixed, bulky and expensive sensors to measure soil or plant water status.