Sorption and hydraulic performance of cement-bentonite cutoffs in saline sulphatic solutions

The paper discusses the results of an experimental research on the short and long term hydraulic performance and sorption of cement-bentonite mixtures in saline sulphate solutions. Batch tests at different curing times and permeation tests were performed on three cement-bentonite mixtures with solutions of K₂SO₄. The results show that permeation can adversely affect the hydraulic performance of cement-bentonite mixtures depending on the sulphate concentration and mixture composition and that the choice of a very low permeable mixture is essential to limit adverse effects of interaction with SO₄^2- on the hydraulic performance.Sorption of K⁺ was found to be significant, well described by a linear isotherm in a wide range of concentration and nearly constant with curing. Sorption of SO₄² was found to decreases with mixture porosity. Since sorption of SO₄^2- means negative interaction, batch tests were found to be useful for a rapid estimation of possible negative effect of SO₄^2- on the hydraulic behaviour in the long term, when selecting a mixture in the design phase.All the results point out the importance of selecting a mixture to be used for cut-off walls with a low hydraulic conductivity already at brief curing and of carefully considering interaction with solute pollutants and sorption capacity.     

惰性粉的吸湿特性及防虫抑霉风险评估

在26.7℃的温度下和相对湿度12%至80%的条件下,采用静态平衡重量法测定了不同相对湿度下惰性粉的吸湿情况,利用二项式回归和模型拟合的方法研究了在不同相对湿度条件下绘制惰性粉吸湿动力学曲线,比较了GAB、GAB-VR和BET等3个水分吸着等温线模型的适用性,分析了惰性粉水分吸着等温线模型。研究了不同含水量的惰性粉拌入小麦中长角扁谷盗的生存分析、小麦的霉变风险,评估了应用惰性粉安全储粮的平衡含水量临界值。结果表明,在12%至72%的相对湿度下,惰性粉表现为失水过程；在75%至80%的相对湿度下,惰性粉表现为吸湿过程。在80%的相对湿度下,惰性粉的含水量由3.65%增加值17.58%,增加了3.8倍。惰性粉含水量越低长角扁谷盗的存活时间越短,在95%的置信区间,当含水量低于3.35%时惰性粉对长角扁谷盗的致死作用显著。应用惰性粉做谷物防护剂时应控制粮堆中惰性粉的含水量不得超过15.81%,否则粮堆则有可能出现霉变。环境相对湿度越高,惰性粉处理过的小麦粒表面出现霉变的数量越早,数量越多,随着时间的延长霉变率逐渐增大。     

Hybrid solar-driven hydrogen generation by sorption enhanced–chemical looping and hydrocarbon reforming coupled with carbon capture and Rankine cycle

Hydrogen ($H_2$) production from fossil fuels using Hydrocarbon Reforming Methods (HRM) accounts for nearly 95% of Global $H_2$ production. Unlike hybrid Chemical Looping Steam Reforming (CL-SR) systems, the Integrated Solar-Driven Sorption Enhanced–Chemical Looping of Hydrocarbon Reforming (SE-CL-HR) utilises solar thermal energy from the Concentrating Solar Power (CSP) system to drive the endothermic decomposition of feedstocks. Furthermore, the simulated hybrid systems utilise recovered heat to generate electricity, reuse of by-product ${CO}_2$ for more syngas production and finaly, ${CO}_2$ capture by reaction of $CaO$ to form ${CaCO}_3$. This work focused on simulating hybrid CSP systems and SE-CL-HR plants with Heat Transfer Fluid (HTF) output temperatures between 750 and 1050 °C. In this study, System Advisor Model (SAM) and MATLAB software are used to develop the CSP system. While the CSP result saved in the MATLAB workspace gets exported to Simulink to feed SE-CL-SMR, SE-CL-POX and SE-CL-ATR Aspen plus models. The integrated system was fed with ${CH}_4$ as the working fluid of the solar furnace. Stoichiometric and Gibbs free-energy minimisation were employed to investigate the effect of operating parameters. The output of the integrated system shows ≥9.5% exergy efficiency in comparison to conventional HRM. In addition, ${CO}_2$ capture by $CaO$ and high-pH water ($Ca$, $Mg$, $N{a}^{+}$, $O_2$, $O{H}^{-}$ and $C{l}^{-}$) to produce ${CaCO}_3$, ${MgCO}_3$ and other valuable products was also investigated in a process simulation. The research results revealed that for 8.1 $tons/hr$ of ${CH}_4$ and 277.1 $tons/hr$ $H_{2}O$ (steam) flowrates, 62 $tons/hr$ of $H_2$ can be generated and 338.5 $tons/hr$ of ${CO}_2$ emission can be reused and captured by the adoption of these new innovative technologies.     

Enhanced hydrogen storage capacity of NiAl-layered double hydroxide modified with Tb3Fe5O12 nanostructures

Under ultrasonic irradiation, the porous Tb₃Fe₅O₁₂ (TFO) and Nickel Aluminum layer double hydroxide (NiAl-LDH) were synthesized by investigation the effect of sonication time. Synthesis of TFO was conducted in the presence of tetradentate Schiff-base ligand H₂salophen, [N,N′-bis(salicylidene)-1,2-phenylenediamine] as complexing agent to size controlling and further growth prevention of crystals. The resultant nanocomposites of TFO/NiAl-LDH used as novel active compounds for applying in hydrogen storage strategies. Comprehensively, the hydrogen capacitance after 15 cycles was displayed on the pure NiAl-LDH and TFO materials about 115 and 334 mAhg⁻¹ respectively. It demanded the maximum capacitance for Tb₃Fe₅O₁₂/NiAl-LDH nanocomposites was 451 mAhg⁻¹, which was higher than the initial NiAl-LDH structure. It was exposed from the spillover effect that; the endorsed electrochemical hydrogen storage (EHS) performance is ascribed to the reaction of the redox pair of Fe³⁺/Fe²⁺ at the active sites throughout the EHS procedure. This work delivers a novel plan and potential sorption electrode materials to progress the intrinsic action of layered compounds.     

Experimental investigation on sorption performance of new high–efficiency,inexpensive H2 getters in high–vacuum,variable density–multilayer insulated hydrogen storage equipment

Hydrogen (H₂) is released by the manufactured materials, which results in the deterioration of the insulation performance of liquid hydrogen (LH₂) storage tanks. The getter is found in the vacuum annular space of equipment and helps maintain the high vacuum of LH₂ tanks. Palladium oxide (PdO), an effective H₂ getter, is expensive, resource–constrained and unsuitable for the LH₂ equipment. Therefore, suitable and inexpensive alternatives were examined using LH₂ storage tanks, to maintain the insulation property of the high–vacuum variable–density multilayer insulation (VDMLI) equipment better. Eight types of H₂ getters were designed using in the LH₂ tanks, and classified into three categories, namely, chemical, physical and physico–chemical getters (PCNHG). The sorption performance of new H₂ getters was compared with that of PdO. PdO could be replaced by in the 7:1, 5:1 and 4:1 ratio by PCNHG1, PCNHG2 and CNHG in the LH₂ tanks, respectively. The results demonstrated that the sorption capacity of PCNHG1 and PCNHG2 were 1.70 and 2.14 times that of the same type of getters in the market (16.35% and 20.62% higher than that of PdO, respectively). Their average H₂ sorption efficiency was 1.17 times and 1.05 times of that of PdO, respectively. The minimum thermal conductivity exhibited by CNHG was only 6.34% of that of PdO, and the sorption capacity of CNHG was 1.82 and 1.44 times that of PCNHG1 and PCNHG2, respectively. However, the sorption capacities of PCNHG1, PCNHG2 and CNHG were belows that of PdO. These results help facilitate reduction in the expense of H₂ getters and provide an important reference to enhance the sorption performance of getters.     

Production and characterization of oxidized cassava starch (Manihot esculenta Crantz) biodegradable films

Plastic is one of the most common pollutants in the environment. Therefore, the number of studies on the use of biodegradable packaging is increasing. Starch is the primary material used in the production of biodegradable plastics due to its natural abundance and high biodegradability. Yet, the strong hydrophilic character of starch presents a challenge. Therefore, the modification of its structure through oxidation may yield interesting results as the viscosity reduction. The objectives of this work were to obtain cassava (Manihot esculenta Crantz) starch oxidized with 0.8 and 2.0% active chlorine, to develop biodegradable films and characterize their mechanical properties, solubility in water, permeability to water vapor, degree of swelling, and sorption isotherms. Biodegradable films were produced with starch concentrations of 2, 3, 4, and 5% w/w and 25% glycerol (g/100 g starch) added as a plasticizer. Images of the films were obtained with an atomic force microscope and allow to observe a smooth surface and the absence of starch granules in the film produced with oxidized starches. The tensile strength of the biodegradable film produced with oxidized starch (0.8% active chlorine) was 80 MPa. The value of permeability to water vapor was 1.613 × 10⁻⁹ kg/day/m/Pa, and the average solubility was 41%. The sorption isotherms showed that biodegradable films made with oxidized starches cannot be used in environments with relative humidity below 35% or above 90%.     

A new method for predicting sorption isotherms at different temperatures: Extension to the GAB model

In this work, the new methodology for parameter estimation using less experimental data proposed in Staudt et al. (2013) is extended to be used with the GAB model. In addition, a modification in the Arrhenius form for temperature dependency of the energetic constant C is proposed in order to avoid numerical instabilities during parameter estimation. When compared to the original work, one additional parameter, k needs to be estimated but still only one isotherm and one value of net isosteric heat of sorption is required to build the whole set of sorption isotherms. Different food materials were successfully tested providing good fitting and prediction results attesting that the advantages of the methodology originally developed for the BET model are kept with the GAB model.     

A new method for predicting sorption isotherms at different temperatures using the BET model

A new methodology to predict sorption isotherms at different temperatures is proposed in this work. The classical BET model is used coupled with the Clausius–Clapeyron equation, and an Arrhenius temperature dependency is assumed for the BET energetic parameter C. When compared to the usual procedure based solely on the use of a model for the sorption isotherm, this methodology presents two main advantages: (i) a single set of parameters may be used to predict isotherms at different temperatures and (ii) fewer experimental data are required to estimate this set of parameters, using only one single sorption isotherm and one single value of differential enthalpy of sorption, at a specific and arbitrary humidity. The new methodology was tested with different food materials and the predicted results were in good agreement with experimental data, attesting the potential of this new approach.