Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized ...(-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic–hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm–2 maximum power density (in comparison with commercial Nafion 117 membrane, 62.40 mW·cm–2) under 2 M methanol fuel at 70 °C.
In Switzerland, the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling ...properties. During the operational phase of the repository, the host rock will be exposed to pH values as high as 13.5 due to concrete degradation, which will certainly affect its hydraulic properties. This study investigates the effect of pH increase on the water retention properties of Opalinus Clay. A series of samples from the lower sandy facies of the Mont Terri site in Switzerland, at initial dry state, were exposed to a hyperalkaline solution of pH=13.5 and to the synthetic water of pH=7.5 at different water contents. After equilibrium, the total suction was measured with a dew point potentiometer and microstructural analyses were conducted via mercury intrusion porosimetry (MIP) and nitrogen adsorption-desorption technique. It was found that the total suction decreased with hydration and pH increase. Since the two investigated solutions have the same osmotic suction, the decrease in total suction was attributed to the decrease in matric suction. Indeed, the total porosity increased with saturation and pH increase. This was confirmed by MIP data that evidenced an increase in the proportion of macropores, and by Barret–Joyner–Halenda (BJH) data that showed mesopore generation. The specific surface area (SSA) also increased. The previous results were due to mineral hydration and, exclusively in the case of alkaline solution, to (1) the dissolution of quartz and calcite and (2) the acid-base reactions, which were concentrated at the edges of the clay particles, leading to an increase in negatively charged groups and thus to a face-to-face association of the clay particles (dispersion), causing an increase in the repulsive forces between the clay particles. In addition, the weakening of covalent bonds led to the primary dissolution of clay minerals, i.e. silicon and aluminum detachment.
Water is becoming a scarce commodity. Therefore, proper water management in precision irrigation is crucial to increase productivity and reduce the cost of crop production. Precision irrigation is ...based on measuring the soil water content, which is often measured with dielectric sensors that measure the apparent permittivity of the soil. Although the sensors are already equipped with a factory calibration function that converts the measured permittivity into volumetric water content, the function does not work properly for all soil types. It is therefore recommended to check whether a soil-specific calibration is required for accurate soil water content measurements. Precise irrigation also requires adequate determination of soil water retention properties, which can be determined using various procedures and methods. In this paper, we presented the results of applying different approaches to determine soil-specific calibration functions using two types of dielectric sensors (SM150T, Delta-T Devices and MVZ 100, Eltratec) in different soil samples obtained from locations in Slovenia where precision irrigation is performed. In addition, the results of determining the water retention properties of the soil using different methods were also compared.
•Cover crop residue water retention properties changes during decomposition.•Cover crop residue lignin concentrations can be used as a proxy for water retention properties.•Cover crop surface ...residues experience extreme diurnal fluctuations in moisture and temperature compared to underlying soils.•Diurnal variations in decomposition tracked variations in cover crop residue moisture content.•Cover crop decomposition in no-till systems is strongly moisture-limited.
The effect of cover crop (CC) surface residues on water, carbon, and nitrogen cycling in no-till systems depends in part on the water retention properties of decomposing residues and the extent of decomposition. This study (1) examined the effect of decomposition on residue water retention properties; (2) characterized diurnal variations in residue decomposition rates in response to changes in soil-residue-air environmental conditions; and (3) examined the diurnal relationships between cover crop surface residue decomposition and residue environment (moisture and temperature). Maximum gravimetric water content (θg) and characteristic water release curves were determined for red clover (Trifolium pratense L.) and cereal rye (Secale cereale L.) residues collected at 0, 4, 10, and 16 weeks after termination for red clover, and at 2, 5, and 18 weeks for cereal rye. In addition, residue carbon dioxide (CO2-C) flux, along with soil-residue-air environmental conditions, were measured diurnally for red clover at 4, 10, and 16 weeks after termination, and for cereal rye at 5 weeks after termination. Maximum residue θg decreased as decomposition progressed. Cover crop residue decomposition also influenced water release curves such that the water retained at any given water potential (ψresidue) declined with increasing decomposition. These decomposition-associated changes in residue water retention properties were strongly related to residue lignin concentrations. Cover crop surface residue CO2-C flux showed distinct diurnal patterns that were strongly related to ψresidue or residue θg. At a diurnal scale, residue CO2-C flux increased during the nighttime from 18:00 to 06:00 h when residues gain moisture from the atmosphere and soil, and decreased during the daytime from 06:00 to 18:00 h when residues lost moisture via evaporation. Increase in temperature decreased residue CO2-C flux due to moisture limitations. Therefore, CC surface residue decomposition models must address both diurnal changes in ψresidue and the changes in water retention properties as residues decompose.
Sulphonated imidized graphene oxide (SIGO) (graphene oxide (GO) tethered sulphonated polyimide) has been successfully synthesized by polycondensation reaction using dianhydride and sulphonated ...diamine. Polymer electrolyte membranes (PEMs) are prepared by using SIGO (different wt%) and sulphonated poly(imide) (SPI). Resultant SPI/SIGO composite PEMs exhibit improved stabilities (thermal, mechanical and oxidative) and good water-retention properties (high bound water content responsible for proton conduction at high temperature by internal self-humidification). Incorporation of covalent bonded SIGO into SPI matrix results hydrophobic−hydrophilic phase separation and facile architecture of proton conducting path. Well optimized sulphonated poly(imide)/sulphonated imidized graphene oxide (15 wt%) (SPI/SIGO-15) composite membrane shows 2.24 meq g−1 ion-exchange capacity (IEC); 11.38 × 10−2 S cm−1 proton conductivity; 5.12% bound water content; and 10.52 × 10−7 cm2 s−1 methanol permeability.
Maximum power density for pristine SPI membrane (57.12 mW cm−2) improves to 78.53 mW cm−2 for SPI/SIGO-15 membrane, in single-cell direct methanol fuel cell (DMFC) test at 70 °C using 2 M methanol fuel. Under similar experimental conditions, Nafion 117 membrane exhibits 62.40 mW cm−2 maximum power density. Reported strategy for the preparation of PEMs, offers a useful protocol for grafting of functionalized inorganic materials with in organic polymer chain by imidization.
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•Sulphonated imidized graphene oxide was synthesized by polycondensation reaction.•Sulphonated polyimide based PEM shows nucleophilic attack-resistant nature.•Improved water-retention properties are responsible for high proton conduction.•PEMs with internal self-humidification for DMFC applications are architected.
The relationships between the factors that influence the water retention properties of soils (bulk density, sand, silt, clay, organic matter and CaCO3 contents), and their gravimetric moisture at ...field capacity (FC), permanent wilting point (PWP), and their available water capacity (AWC), were studied in 104 surface horizons and 95 subsurface horizons of vineyard soils in the Castilla-La Mancha region of Spain. Taking all soil types together, the depth of the horizon was found to influence PWP and AWC, while the factors with the most significant linear relationship with AWC, both for surface and subsurface horizons, were sand content (r = − 0.47 and − 0.63, respectively) and silt content (r = 0.37 and 0.62, respectively). However, when each FAO Reference Soil Group was studied independently, only Calcisols, Luvisols and Regosols showed significant differences between these horizons in terms of AWC. Greater clay contents were associated with greater FC, PWP and AWC only in Luvisol surface horizons (r = 0.44, 0.40 and 0.33, respectively), and with FC and PWP in subsurface horizons (r = 0.64 and 0.64). A greater CaCO3 content was associated with a greater AWC only in Calcisols, both in surface and subsurface horizons (r = 0.49 for both). Finally, the organic matter content and bulk density of the different soil types showed no clear trend with respect to any soil water retention property; a certain positive effect of organic matter on water retention properties was observed only in the surface horizon and not in the subsurface horizon. A map of the spatial distribution of AWC in surface and subsurface horizons is proposed as a soil management instrument.
•The moisture retention properties of soils are necessary for irrigation management.•FC, PWP and AWC of 104 surface horizons and 95 subsurface horizons were determined.•We established some relationships between FC, PWP and AWRC and other soil properties.•Each Reference Soil Group moisture behaviour was studied separately•Spatial distribution maps are proposed as a soil management instrument.
In view of the problems of hydration cracking and powdering, uncontrollable gelation time and poor compressive strength of sodium silicate gel, poor fluidity, small penetration range and high cost of ...organic gel, combined with the characteristics of strong plasticity and non-cracking of bentonite and fly ash gel, by introducing fly ash and sodium silicate gel, the composite gel was prepared by one step mixing method with sodium bentonite as the main raw material. The optimum ratio of the composite gel was studied by gelation time, compressive strength and viscosity test. The gelation time of the composite gel is controllable between 30 s and 15 min, and the solid/water ratio is suitable from 1∶8 to 1∶16, which has the characteristics of wide solid/water ratio, and the maximum compressive strength is 25 MPa. On this basis, the surface morphology of composite gel fire prevention materials was characterized by scanning electron microscopy, and the microstructure of gel was analyzed. The results showed that Al-O-
AbstractNew ways to apply sustainable materials, such as biomass components, are essential for reducing dependence on fossil fuels. This work investigated the engineering properties of unsaturated ...expansive subgrade soils stabilized by bio-based energy coproducts containing lignin. Lignin is a waste by-product of the paper and pulp industry that is frequently burned. Highway subgrade could consume lignin as an environmentally benign, low-cost, and energy-efficient chemical substance for soil stabilization. Swell and shrink behavior of expansive subgrade soils complicates highway construction and causes damage to existing highways. However, research on the hydromechanical properties and volume change behavior of lignin-stabilized expansive soil is limited, and better insight is required into its unsaturated behavior for safe and economical pavement design practices. In this research, a series of geotechnical laboratory tests were conducted to characterize expansive subgrade soils treated with lignin by determining the Atterberg limits, compaction and consolidation behaviors, swelling characteristics, and water retention properties. The mechanisms influencing the changes in engineering properties of lignin-treated expansive soils were further investigated using soil pH, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis. The study shows that the optimal lignin content contributed to an acceptable degree of soil stabilization. The lignin-based cementing material effectively bonds soil particles together and fills pores, thereby preventing water infiltration into the soil and reducing the swell–shrink potential of stabilized soils.
