Amount Of Dissolution Research Articles

Performance optimization and environmental assessment of novel alkali-activated binders containing carbonated recycled concrete powder

This study investigates the influence of carbonated recycled concrete powder (CRCP), alkali content (AC), and silicate modulus (SM) on the compressive strength, chemical composition, and environmental benefits of CRCP-blast furnace slag blended alkali-activated binders (AABs). The results show that increasing CRCP content reduces the compressive strength of AABs due to lower geopolymeric reactivity. Using response surface methodology, the optimal values for AC and SM in AABs containing 50 wt% CRCP were determined as 14.28% and 0.92, respectively, resulting in predicted and actual strengths of 49.9 MPa and 46.8 MPa. Chemical analyses reveal that calcite and vaterite are the predominant crystalline phases in AABs, while both Si-Al gels and calcite from CRCP participate in geopolymeric reactions. The effects of AC and SM on AAB strength are further elucidated through the combined analysis of precursor dissolution amount, geopolymeric gel formation amount, and calcium carbonate decomposition amount. Moreover, CRCP demonstrates negative carbon emissions, with a global warming potential of −0.16 kg CO2 eq/kg. The optimally proportioned AAB containing 50 wt% CRCP shows global warming potential and carbon intensity values significantly lower than those of Portland cement, at 54.4% and 50.8%, respectively. These findings emphasize that AABs containing 50 wt% CRCP not only meet the 43-grade strength classification but also offer notable environmental benefits. In summary, this study contributes to the development of a novel 43-graded low-carbon binder containing high-volume CRCP.

Locally Synthesized Zwitterionic Surfactants as EOR Chemicals in Sandstone and Carbonate.

Zwitterionic surfactants are found to be highly effective in reducing the IFT and changing the wettability. This work studied the solubility and wettability alteration performance of locally synthesized zwitterionic surfactants in Berea sandstone and Indiana limestone. Contact angle measurements were conducted to study the wettability under different conditions. SEM images and TGA results were combined to reflect on the wettability alteration mechanism. The zeta potential test was adopted to study the surface charge of the Indian limestone powder. Results showed that five of the six surfactants dissolved in deionized water to form 1.0 wt % solution, indicating efficient solubility for EOR purposes. Although its wettability alteration performance on oil-aged Berea sandstone is weak to moderate, the performance of ZW6 on Indiana limestone is excellent. ZW6 can change the strongly oil-wet (162°) rock back to water-wet (62.9°) conditions. Increasing its concentration from 0.01 to 0.5 wt % continuously enhanced the performance. The addition of NaCl to 150000 ppm did not affect the wettability alteration. However, the addition of CaCl2 largely suppressed the wettability alteration, while Na2SO4 and MgCl2 both enhanced the performance. With the same headgroup, a more hydrophobic tail group impairs the wettability alteration. The quite different wettability alteration performance of MgCl2 and CaCl2 cases (which had approximately the same amount of calcite dissolution), and the comparable wettability alteration performance of Na2SO4 and MgCl2 (which had very different calcite dissolution amounts) indicate that calcite dissolution is unrelated to wettability alteration.

Unveiling the dissolution mechanism of calcium ions from CSH substrates in Na2SO4 solution: Effects of Ca/Si ratio

The decalcification behavior of calcium silicate hydrate (CSH) under sulfate attack poses a critical challenge to the long-term durability of cement-based infrastructure, yet understanding its underlying microscopic mechanisms remains elusive. This study employs molecular dynamics to compare the differences in calcium ion dissolution capability of CSH substrates with varying Ca/Si ratios under sulfate solution exposure. The results show that the dissolution amount and dissolution efficiency of Ca are positively correlated with Ca/Si, and the root cause depends on the basic structure of CSH. With the increase of Ca/Si, the electronegativity of CSH decreases, and the adsorption capacity and stability of cations weaken. Meanwhile, Ca ions are less limited by the silicate chain coordination, water molecules are more likely to invade the substrate interior and replace the Ca ions. This research aims to provide a molecular basis for cement production and durability applications in marine engineering.

Ice Formation, Exsolution, and Multiphase Equilibria in the Methane–Ethane–Nitrogen System at Titan Surface Conditions

Titan is unique among the icy satellites in that it has a thick atmosphere, stable surficial bodies of liquid, and a precipitation system that promotes interactions between the two. Although Titan’s surface conditions are typically assumed to be above the freezing point temperatures of the major constituent species of the climate system (methane, ethane, and nitrogen), conditions may be sufficiently cool across parts of Titan to allow for ice formation alongside known liquid-vapor phases. In this study, we used Raman spectroscopy, visual inspection, and the CRYOCHEM 2.0 equation of state to map the appearance of first ice and to quantify the amount of nitrogen dissolution into liquid in the methane–ethane–nitrogen system along a 1.5 bar isobaric cooling path in the temperature range 80–95 K. This was with the intent of (1) determining the effects nitrogen has on the phase behaviors of the methane–ethane binary system, and (2) establishing the temperatures and ternary mixing ratios needed for ice formation on Titan’s surface. We found that ethane-rich mixtures enter a three-phase solid–liquid–vapor equilibrium and are characterized by nitrogen-rich exsolution upon freezing and ice that form at the bottom of the sample. With sufficient methane content, the mixtures cross a univariant four-phase solid–liquid–liquid–vapor boundary, which contributes to a distinct isothermal freezing point profile and ice that forms starting at the liquid–liquid interface. Our results generally agree with findings from previous studies of the methane–ethane–nitrogen system and are intended to add to our current understanding of Titan’s geochemical processes.

Optimizing Construction Spoil Reactivity for Cementitious Applications: Effects of Thermal Treatment and Alkaline Activation

Construction spoil (CS), a prevalent type of construction and demolition waste, is characterized by high production volumes and substantial stockpiles. It contaminates water, soil, and air, and it can also trigger natural disasters such as landslides and debris flows. With the advent of alkali activation technology, utilizing CS as a precursor for alkali-activated materials (AAMs) or supplementary cementitious materials (SCMs) presents a novel approach for managing this waste. Currently, the low reactivity of CS remains a significant constraint to its high-value-added resource utilization in the field of construction materials. Researchers have attempted various methods to enhance its reactivity, including grinding, calcination, and the addition of fluxing agents. However, there is no consensus on the optimal calcination temperature and alkali concentration, which significantly limits the large-scale application of CS. This study investigates the effects of the calcination temperature and alkali concentration on the mechanical properties of CS–cement mortar specimens and the ion dissolution performance of CS in alkali solutions. Mortar strength tests and ICP ion dissolution tests are conducted to quantitatively assess the reactivity of CS. The results indicate that, compared to uncalcined CS, the ion dissolution performance of calcined CS is significantly enhanced. The dissolution amounts of active aluminum, silicon, and calcium are increased by up to 420.06%, 195.81%, and 256.00%, respectively. The optimal calcination temperature for CS is determined to be 750 °C, and the most suitable alkali concentration is found to be 6 M. Furthermore, since the Al O bond is weaker and more easily broken than the Si O bond, the dissolution amount and release rate of active aluminum components in calcined CS are substantially higher than those of active silicon components. This finding indicates significant limitations in using CS solely as a precursor, emphasizing that an adequate supply of silicon and calcium sources is essential when preparing CS-dominated AAMs.

Dissolution process and mechanism of montmorillonite in oxalic acid and sulfuric acid media at various pH levels

The dissolution of silicate minerals plays a crucial role in many natural geological processes. In order to better comprehend the reaction mechanisms and dissolution characteristics of montmorillonite in different acidic systems, the effects of interfacial reactions of montmorillonite with oxalic and sulfuric acid solutions at various pH levels on the ionic dissolution, crystal structure, and micro-morphology were studied, and the morphology of aluminum and saturation index of secondary mineral were simulated. It was shown that the dissolution amounts of Mg2+, Al3+ and Si4+ in montmorillonite structure decreased with the increase of pH value, which reflected the dependence of montmorillonite dissolution on the pH value of solution. The dissolution percentages of Mg2+, Al3+ and Si4+ after the reaction of montmorillonite with oxalic acid solution were greater than those in sulfuric acid solution, and the highest dissolution rate of Al3+, indicated that both ligands and protons attacked the surface sites of montmorillonite and accelerated the dissolution of ions. Moreover, oxalate ligands exerted specific binding effects on Al3+ ions. While reacting with oxalate and sulfate, the tetrahedral, octahedral and interlayer cations of montmorillonite exhibited the non-stoichiometric and inconsistent dissolution. The oxalate ligands have a strong complexation effect on Al3+, so that Al3+ in oxalate solution exists in the form of aluminum oxalate complex, which reduces the effective concentration of Al3+ in solution and promotes the dissolution of Al3+ in montmorillonite structure. The Mg2+ ions settled at octahedral substitution sites possessed weak stability, while those from the interlayer featured strong interlayer interchangeability, demonstrating the dissolution percentage up to 10.85 % and 8.62 % even in oxalic and sulfuric acid solutions at pH of 6.5. All secondary mineral phases in the solution were undersaturated, making the montmorillonite dissolution difficult to balance. Montmorillonite has a high cation exchange capacity, which makes it have a strong buffer capacity to exogenous acids. This study helps to explain the dissolution process of montmorillonite in inorganic and organic acid solutions at different pH value.

Variations of silicon species, dissolution and crystallinity within sichars prepared under different heating rate

Silicon within Si-rich biochars (sichar) plays a crucial role in immobilizing heavy metals and providing slow-releasing bioavailable silicon for silicophilic plants. However, the impact of heating rate on the silicon properties and carbon‑silicon interactions in sichars remains unclear. In this study, rice husk was used as a silicon-rich biomass to prepare sichars at different heating rates (10, 30 and 60 °C per minute, and ultra-fast-pyrolysis), then experiments such as silicon concentration measurement, Raman and XRD characterization were conducted. The results showed that a faster heating rate reduced the carbon content during pyrolysis while promoted the formation of amorphous silica, resulting in a threefold increase in dissolved silicon in sichars prepared at 400 °C. Additionally, we observed the formation of a meta-stable SiO2 polymorph (tridymite) in rice husk-derived biochars under fast heating, differing from the previously observed quartz generated at slow heating rates. Regarding the CSi relationship, a faster heating rate facilitated the removal of the surface carbon layer, exposing the underlying silicon layer. This led to more soluble silicon species and less encapsulated silicon, resulting in a continuous release and cumulative silicon dissolution amount 1.2 times and 1.6–1.9 times higher, respectively, than those in slow heating rate-derived sichars. Consequently, this enhanced silicon uptake in rice seedlings. Our findings indicate that beyond pyrolysis temperature, the heating rate significantly affects the silicon species, silicon dissolution behavior, and carbon‑silicon relationships of biochar, ultimately determines the properties and applications of sichars.

Enhanced T5 age-hardening behavior of Al–Si–Mg casting alloy with prolonged melt holding and high quench temperature

The effects of the quench temperature (cooling rate) and melt-holding time at high temperatures on the precipitation kinetics and nanostructure of the Al–Si–Mg alloy were investigated by measuring the hardness and electrical conductivity, differential scanning calorimetry, transmission electron microscopy, and atom probe tomography. The results showed that a high quenching temperature (high cooling rate) and long melt holding simultaneously increased the hardness and electrical conductivity of the Al–Si–Mg alloy. They also accelerated the overall precipitation kinetics; however, the effect was more evident when the duration of high-temperature melt holding increased. Nanostructural analysis of the peak-aged conditions revealed that the accelerated precipitation kinetics of the alloy with a high quenching temperature were primarily related to the high amount of Si solutes, which prevented the formation of coarse Si precipitates. Conversely, the high precipitation kinetics caused by longer melt-holding treatments depend on the increased amount of solutes and dissolution of clusters and could disturb the formation of strengthening β″ precipitates. These results indicate that the mechanical properties of the T5-treated Al–Si–Mg alloy can be significantly enhanced by increasing the quenching temperature and providing sufficient melt holding at high temperatures.

PH Dependence of Noble Metals Dissolution: Gold

AbstractThe electrochemical applications of gold span the entire pH spectrum. Recently, gold dissolution in acidic and alkaline media has been studied, but less attention has been given to electrolytes at intermediate pH values. To address this gap, this work uses on‐line electrochemical dissolution inductively coupled plasma mass spectrometry (ICP‐MS) to examine gold dissolution across a pH range of 1 to 12.7 using phosphate buffer solutions. All experimental parameters, except pH, are kept constant, enabling a clear investigation of pH effects on anodic (gold oxidation) and cathodic (gold oxide reduction) dissolution processes. Results show that dissolution amounts are lowest at neutral pH values between 3 and 7, varying with the applied potential and exposure time. Anodic and cathodic dissolution dominate in acidic and alkaline electrolytes, respectively. Depending on the highest applied potentials and time exposure, the main dissolution mechanism shifts at pH=5, 7, and 9. The pH dependence of Au dissolution is proposed to be linked to the nature of gold oxides formed, the kinetics of oxide formation/reduction, gold ion redeposition, and the influence of the oxygen evolution reaction (OER) on dissolution. These results provide fundamental insights into gold dissolution under neutral pH conditions.

Analysis on Spatial Variability of Hydrochemical Characteristics and Control Factors of Jinan Baotu Spring Area

To understand the karst groundwater hydrochemical characteristics and ion sources of the Jinan Baotu Spring area, this study focused on the three functional zones as an indirect recharge area, direct recharge area, and discharge area. Through water sample collection and testing, the spatial variability of groundwater chemical characteristics in different functional zones and the formation mechanism were analyzed using hydrochemistry parameter statistics, multivariate statistics, self-organizing map, hydrochemistry graphical analysis, ion ratios, and other methods, guided by the theory of groundwater flow system and combined with regional physical geography and hydrogeological conditions. The results showed that： the groundwater of each functional zone was alkaline as is typical in the dissolution of carbonate minerals. Owing to the different groundwater runoff pathways, the variability of water chemistry parameters in different functional areas was obvious. The groundwater of the discharge area was recharged by both the direct recharge area and the indirect recharge area. The hydrochemistry type changed from HCO3-Ca type to HCO3·SO4-Ca type through the indirect recharge area to the discharge area. The presence of a small amount of gypsum dissolution within the aquifer generated Ca2+ and SO42-. The ions in groundwater mainly came from the dissolution and filtration of aquifer rock minerals, and at the same time, they were affected by cation exchange, mineral dissolution equilibrium, and the combined effects of human activities. The groundwater in the Baotu Spring area was greatly influenced by human activities, which to some extent affected the evolution of groundwater hydrochemistry in the spring area.

Impact of applied potential range on corrosion behavior of stainless steel oxygen evolution electrode under potential cycle loading

We investigated the corrosion behavior of 310S stainless steel anode for alkaline water electrolyzer under various triangle-wave potential cycle loadings by changing the lower (x) and higher (y) vertex potentials to simulate the power fluctuation characteristics of renewable energy sources. The anode was subjected to the loadings of x = 0.5–1.5 and y = 1.8–2.5 V in 7 M KOH solution. The dissolution of Fe and Cr into the electrolyte depended significantly on x. Notably, under conditions of x ≥ 1.35 V, the total dissolution amounts of Fe and Cr after the 20,000 potential cycles decreased to approximately 7 % of the condition where x = 0.5 V. Conversely, y had less influence on the total dissolution amounts. Interestingly, the molar ratios of the eluted Fe and Cr into the electrolyte depended on both x and y, suggesting distinct corrosion behaviors of the stainless steel induced by the potential cycles of x ≤ 1.35 and y = 1.8 V, compared to those at x ≥ 1.35 and y = 2.5 V. These findings suggest the importance of precise potential control of the stainless steel anode in alkaline water electrolysis for preventing potential fluctuation-induced corrosion.

Characteristics and Sources of CBM Well-Produced Water in the Shouyang Block, China

The Shouyang Block was selected as the research subject. Comprehensive analysis was conducted using coalbed methane (CBM) well production data, geochemical test data on water produced from the coalbed methane well, and fundamental geological information. The findings reveal the water dynamics in the Shouyang Block are characterized by weak groundwater runoff or retention in most areas. The groundwater head height exhibits a gradual decrease from the north to south, which is closely associated with the monoclinic structure of the Shouyang Block. Overall, water production is relatively high. As the average water production increases, the average gas production gradually decreases. A concentration of high water production wells is observed in the northern part of the Shouyang Block, which gradually increases towards the southeast direction. A comprehensive analysis was conducted on the factors influencing water production, including total water content of coal seams, coal seam porosity, groundwater stability index, groundwater sealing coefficient, D value of the fracture fractal dimension, fault fractal dimension, and sand–mud ratio. The correlation degree was calculated and ranked in order of magnitude through grey correlation analysis. The order of factors that influence water production, from strongest to weakest, is as follows: sand–mud ratio > porosity > fractal dimension of fault > fracture fractal dimension D value > groundwater sealing coefficient > groundwater stability index > total water content of coal seams. The dissolution amounts of carbonate and sulfate are both small, and the water source may mainly come from the sandstone aquifer. Attention should be paid to the distribution and lithological combination of sandstone aquifers in coal-bearing strata in the future exploration and development process of the Shouyang Block. This will help to avoid the potential influence of fault structures and enable the identification of favorable areas for low water and high gas production.

Microstructure and electrochemical corrosion behavior of TA2 with nano/micro TiC particle reinforcement

TA2 pure titanium (Titan Grade 2-EN) is commonly used in marine and biomedical applications due to its outstanding biocompatibility and resistance to corrosion. Nevertheless, the limited hardness of TA2 presently reduces the service life of the components. Directed energy deposition (DED) technology can improve the properties of conformal materials, opening up new possibilities. In this work, 8% micro-TiC/TA2, 8% nano-TiC/TA2, and 4% micro/4% nano-TiC/TA2 composites were fabricated by DED to investigate the effects of different scales of TiC reinforcement on the properties of TA2. The majority of micro-TiC remaining unmelted in the composite, exhibiting only a small amount of micro-TiC dissolution. In comparison, the nano-TiC/TA2 displays a conspicuous dendritic structure with well-developed dendritic growth, boasting up to three dendrites. In contrast, the 4%micro/4%nano-TiC/TA2 exhibits a mixed crystal morphology, characterized predominantly by dendritic growth along the unmelted TiC, with other TiC phases also present in the deposited layer. Performance tests demonstrated that TiC can increase the microhardness of titanium. The 4% micro/4% nano-TiC/TA2 composite achieved the highest average microhardness of 542 HV0.2, representing a 160.58% increase compared to TA2. Additionally, the composites demonstrated improved corrosion resistance relative to TA2, with the 8% micro-TiC/TA2 composite exhibiting the best corrosion resistance. This outcome can be attributed to the effective physical barrier properties of the micron-sized TiC.

PVP/aprepitant microcapsules produced by supercritical antisolvent process

The supercritical antisolvent (SAS) process was a green alternative to improve the low bioavailability of insoluble drugs. However, it is difficult for SAS process to industrialize with limited production capacity. A coaxial annular nozzle was used to prepare the microcapsules of aprepitant (APR) and polyvinylpyrrolidone (PVP) by SAS with N, N-Dimethylformamide (DMF) as solvent. Meanwhile, the effects of polymer/drug ratio, operating pressure, operating temperature and overall concentration on particles morphology, mean particle diameter and size distribution were analyzed. Microcapsules with mean diameters ranging from 2.04 μm and 9.84 μm were successfully produced. The morphology, particle size, thermal behavior, crystallinity, drug content, drug dissolution and residual amount of DMF of samples were analyzed. The results revealed that the APR drug dissolution of the microcapsules by SAS process was faster than the unprocessed APR. Furthermore, the drug powder collected every hour is in the kilogram level, verifying the possibility to scale up the production of pharmaceuticals employing the SAS process from an industrial point of view.

Reducing Calcium Dissolution in Tunnel Shotcrete: The Impact of Admixtures on Shotcrete Performance.

Groundwater infiltration into tunnels causes water to percolate through the fissure channels in the initial support shotcrete. This results in the dissolution and outflow of calcium hydroxide, a key product of cement hydration. This process significantly incurs the formation of crystallization blockages in the tunnel drainage systems. Optimizing the shotcrete mixing ratio is a feasible way to mitigate these blockages. Therefore, this study conducts calcium dissolution tests to investigate the impact of six admixtures, namely, antialkali agent, nanosilica, nanosilica carbonate, fly ash, sodium methyl silicate waterproofing agents, and silane waterproofing agents, on calcium dissolution resistance. Also, mechanical and microscopic tests are carried out to examine their impact on the strength and pore structure of the shotcrete. The objective of this study is to determine the optimal admixture for enhancing the calcium dissolution resistance of shotcrete. Results indicate that the antialkali agent significantly reduces the calcium leaching content of shotcrete. When the dosage is 14%, the calcium leaching amount is reduced by 68.4% in 28 days. Followed by nanosilica and silane waterproofing agents, with optimal dosages of 12 and 0.4%, respectively, the dissolution amount of calcium ions in shotcrete was reduced by 32.87 and 26.5%, respectively. Fly ash curing for 28 days can also reduce the calcium ion dissolution of shotcrete, while nanocalcium carbonate and sodium methyl silicate have little effect on the calcium dissolution of shotcrete. The antialkali agent with a strong calcium ion dissolution effect can improve the tensile strength of shotcrete under long-term curing conditions, which can be increased by 52%, but it compromises the growth of compressive strength. Nanosilica, fly ash, and silane waterproofing agents can improve both the compressive strength and tensile strength of shotcrete under long-term curing conditions. Specifically, at 28 days of curing, the compressive strength increased by 16.83, 28.8, and 20% and the tensile strength increased by 50.24, 60, and 64.5%. In addition, the microscopy results show that the antialkali agent, nanosilica, and silane waterproofing agents promote the hydration process of cement to form ettringite with a low and stable calcium-silicon ratio and reduce calcium hydroxide crystals. Nanosilica and silane waterproofing agents optimize the pore distribution in shotcrete by increasing beneficial pores, decreasing harmful pores, and reducing total porosity.

Microstructural evaluation of interfacial intermetallic compounds between Sn58Bi and ENEPIG

BackgroundLow carbonization and Restriction of Hazardous Substances (RoHS) regulations have promoted the development of low-temperature lead-free solder. The solder and substrate are critical entities of joint connections. MethodsSn58Bi has been considered a promising low-temperature solder. Electroless nickel/electroless palladium/immersion gold (ENEPIG) is a good surface finish that prevents solder joints from oxidizing and extends the shelf life of the substrates. In this study, the interfacial reactions between the Sn58Bi solder and ENEPIG surface finish were systematically analyzed. Findings(Au,Pd,Ni)(Sn,Bi)4 was observed after reflow at 160 °C. Au and Pd dissolved into solder rapidly in the beginning. NiSn4 and Ni3Sn4 with small amounts of Au and Pd dissolution formed at the interface after aging. The morphology of NiSn4 evolved from block-like to needle-shaped and finally to a layered configuration as the aging temperature and time increase. Ni3Sn4 was observed between NiSn4 and substrate above 100 °C. This study established the growth mechanism of intermetallic compounds (IMCs) in the reaction between Sn58Bi and ENEPIG for low-carbon emitting processes.

Experimental Study on Carbon Dioxide Displacement by Coal Seam Water Injection.

Using water to displace carbon dioxide adsorbed in coal can prevent coal and gas outbursts. However, the mechanism of continuous water injection replacing adsorbed gases in coal has not been well studied. An experiment with the same water injection pressure and different adsorption equilibrium pressures for displacing carbon dioxide was conducted. The variation patterns of the amount of displaced carbon dioxide, time, and water displacement rate, displacement ratio, and water action ratio were analyzed. The modes of water injection displacing carbon dioxide are discussed. The results show that the change in the amount of displaced carbon dioxide consists of three stages: rapid, slow, and stop growth stages. For the same displacement time, as the adsorption equilibrium pressure rises, more carbon dioxide is displaced. The time displacement rate and water displacement rate can be divided into three stages: rising, peak, and dropping stages. As the adsorption equilibrium pressure increases, the duration of the peak stage decreases, while the time and water displacement rates increase. At different adsorption equilibrium pressures, the carbon dioxide displacement ratio ranged from 45% to 54%, less than the natural desorption ratio. But the water action ratio containing the gas dissolution amount was close to or greater than the natural desorption ratio. Thus, the displacement effect of flowing water accelerated the desorption of carbon dioxide in coal. The modes of carbon dioxide displacement by water injection include water-displacement, gas-dissolution displacement, and gas-diffusion-dissolution displacement. The findings of this study provide novel suggestions for preventing and controlling coal and gas outbursts.

Wet peroxide oxidation process catalyzed by Cu/Al2O3: phenol degradation and Cu2+ dissolution behavior.

Catalytic wet peroxide oxidation (CWPO) has become an important deep oxidation technology for organics removal in wastewater treatments. Supported Cu-based catalysts belong to an important type of CWPO catalyst. In this paper, two Cu catalysts, namely, Cu/Al2O3-air and Cu/Al2O3-H2 were prepared and evaluated through catalytic degradation of phenol. It was found that Cu/Al2O3-H2 had an excellent catalytic performance (TOC removal rate reaching 96%) and less metal dissolution than the Cu/Al2O3-air case. Moreover, when the organic removal rate was promoted at a higher temperature, the metal dissolution amounts was decreased. Combined with hydroxyl radical quenching experiments, a catalytic oxidation mechanism was proposed to explain the above-mentioned interesting behaviors of the Cu/Al2O3-H2 catalyst for CWPO. The catalytic test results as well as the proposed mechanism can provide better guide for design and synthesis of good CWPO catalysts.

Constructing a map of potassium inputs to paddy fields from irrigation

Geographical and geological parameters, including land use, lithology, and water quality, and volume of irrigation were investigated to map K inputs into paddy fields from irrigation in the eastern part of Fukushima, Japan. This area has had one of the greatest needs for K maintenance worldwide due to the control of radiocesium uptake by plants after the Fukushima nuclear accident in 2011. The K+ concentration in irrigation water and its sources was in the range of 0.2–5.2 mg L−1, which was probably affected by both the natural conditions (e.g., amount of silicate mineral dissolution and presence of hot springs and coal seams) and human activities (e.g., agriculture and urbanization). Irrigation volume was estimated to range from 306 to 2300 mm in response to daily water requirement rates. K inputs were computed by multiplying the concentrations and volumes, giving estimated inputs of 2.5–133 kg K2O ha−1 crop−1. The inputs proved spatially variable and were high in the western and southeastern parts of the study area. Irrigation was estimated to supply more than half of the K application rate in the rice cultivation guidelines to 12% of the paddy field area. This map should provide useful information for devising K maintenance plans.

Tuning Mo cations dissolution and surface reconstruction of CoMoO4 for efficient oxygen evolution reaction

Structural distortion enables modulating surface reconstruction of transition metal oxides by manipulating cation dissolution for oxygen evolution reaction (OER), while revealing reconstruction mechanism is stuck by the demand to precisely regulate exact sites of these structural distortions and further make a robust correlation between surface reconstruction and OER performance. In this work, controllable Mo dissolution in CoMoO4 is adjusted by the structural distortion level of MoO4 tetrahedrons with different annealing temperatures. The structural distortion level of MoO4 tetrahedrons is positively correlated with annealing temperatures and spontaneous Mo cations dissolution in alkaline solution. The moderate amount of spontaneous Mo cations dissolution, in accompany with maximum dissolution amount of Mo cations derived from potential, could expose more Co sites to reconstruct into active species CoOOH at a lower potential, resulting in more catalytically active sites whose overpotential at 100 mA cm−2 with 346 mV and Tafel slope of 92.22 mV dec−1. This work indicates the importance of controlled cation dissolution in modulating the kinetics of surface reconstruction and OER performance of electrocatalysts.