Low Desorption Research Articles

Compositionally complex doping for low-V Ti-Cr-V hydrogen storage alloys

Ti-V-based BCC solid solution alloys, represented by Ti-Cr-V alloys, are considered as promising hydrogen storage materials due to their high hydrogen storage capacity (over 4 wt%) at room temperature. However, the difficult activation, low effective hydrogen desorption capacities, poor P-C-T plateau characteristics, and high cost remain significant problems for their practical applications. Herein, we present a new compositionally complex (high-entropy) doping strategy which was used to successfully fabricate a low-cost “Laves phase related BCC solid solution”, TiCrV0.7(Nb0.2Fe0.2Co0.2Ni0.2Mn0.2)0.2, that exhibits excellent activation performance and high effective hydrogen desorption capacity (Ce1atm: 2.21 wt%). The main BCC phase ensures high hydrogen storage capacity, while the minor secondary C14 phase plays a catalytic role and thus improves the hydrogen absorption kinetics. Furthermore, we confirmed that there is a synergistic effect of Nb, Fe, Co, Ni, and Mn elements in improving hydrogen storage performance. The dehydrogenation enthalpy ΔH of the heat-treated TiCrV0.7(Nb0.2Fe0.2Co0.2Ni0.2Mn0.2)0.2 is 37.5 kJ mol−1, which is significantly lower than previously reported Ti-Cr-V based systems, revealing a significant tendency towards easier dehydrogenation with high-entropy doping. This work offers a new alloying method for improving the hydrogen storage performance of hydrogen storage alloys.

Highly efficient removal of radioactive iodine anions by nano silver modified activated carbon fiber

Radioactive iodine anion wastewater is generated during the operation of nuclear facilities. Efficiently adsorbing and removing radioactive iodine is crucial for the sustainable development of nuclear energy. A potential adsorbent, nano silver-loaded activated carbon fiber (Ag@ACF), was prepared through hydrothermal synthesis and high-temperature vacuum reduction for the efficient removal of iodide anions. The as-prepared Ag@ACF composite has been comprehensively characterized, with silver nanoparticles uniformly distributed on the surface and pore walls of the Ag@ACF, enhancing the adsorption sites for iodine anions. The adsorption performance of Ag@ACF towards iodine anions was evaluated through column and batch experiments, varying silver concentration, adsorbent dosage, pH, contact time, and competing anions. Ag@ACF demonstrated high water stability and a low desorption rate of iodine anions. At a pH of 2, Ag@ACF exhibited a maximum adsorption capacity for iodine anions of 372 mg/g, surpassing most other adsorbents and showing promise for engineering applications. Adsorption kinetics and isotherm analysis indicated that the adsorption process of Ag@ACF primarily involved monolayer homogeneous chemisorption, resulting in the formation of stable AgI. These results suggest that Ag@ACF could serve as a potential adsorbent for removing iodine from radioactive wastewater.

Modelling of hydrogen distribution at the fatigue crack tip of austenitic stainless steels in internal and external hydrogen tests

A hydrogen diffusion model was developed, which accounts realistically for the kinetics of hydrogen adsorption, absorption and their reverse processes at the gas-solid interface. Using the model, the hydrogen distribution at the fatigue crack tip of austenitic stainless steels (304, 316 L) in internal and external hydrogen tests were analyzed. Results indicate that for stable austenitic stainless steel, the hydrogen concentration at the fatigue crack tip is much higher in internal hydrogen test than that in external hydrogen test, which is attributed to the extremely low adsorption, desorption and diffusion rates of γ phase. For metastable austenitic stainless steel, hydrogen rapidly enters into strain-induced α′ martensite around the fatigue crack tip, forming an enrichment peak at the α′/γ interface in external hydrogen test. While significant hydrogen outgassing occurs in α′ phase in internal hydrogen test, leading to a much lower crack tip concentration compared with external hydrogen test.

Surface blistering and deuterium retention in chemical vapor deposition tungsten exposed to deuterium plasma

Chemical vapor deposition tungsten (CVD-W) is a promising material for plasma-facing materials. This work evaluated CVD-W samples with a large grain size (CVD-L) and a small grain size (CVD-S) together with rolled W (ND-W) and recrystallized (Rec-W) samples for their performance under deuterium (D) plasma exposure with a flux of 1021 D m−2 s−1 and fluences up to 2 × 1025 D m−2 at a surface temperature of 500 K. Both CVD-L and CVD-S samples featured a columnar grain structure with a preferred orientation close to 〈001〉 || Z, with a more preferred orientation in CVD-L samples. Both CVD-L and CVD-S samples show good resistance to blistering and only few micron-diameter blisters were observed at fluences. In ND-W and Rec-W samples, the number and size of blisters increased with fluence. The D desorption spectra show two desorption peaks in both CVD-W samples at 520 K and 570–604 K. Whereas in ND-W and Rec-W samples, two peaks were at 520 K and 607–700 K. The total D retention in both CVD-L and CVD-S samples was less than 30 % of that in ND-W and Rec-W samples. The low D retention in CVD-W samples was attributed to the low desorption intensities with the peak at 570–604 K. It is suggested that the microstructure of the columnar grain and the 〈001〉 texture in CVD-W samples helps suppressing plasma-induced blistering, therefore reducing D retention. In terms of the stability of the surface integrity and hydrogen isotopes retention, CVD-W demonstrates a significant potential as a wall material for future fusion reactors.

Influence of wettability alteration on water-blocking effect and gas desorption of coal

To resolve the water-blocking effect that reduces gas extraction after implementing hydraulic measures, alkyl polyglycoside (APG) and polyacrylamide (PAM) were used to treat coal samples to make wettability enhancement and medium wettability conversion, respectively. The contact angle, surface tension, solid surface energy, infrared spectroscopy, and high-pressure water injection desorption were performed to investigate the effects of reagents on the wettability alteration mechanism and desorption characteristics of coal. The results demonstrated that the surface energy, hydrogen bonds and oxygen-containing functional groups of coal alter wettability and gas desorption. The APG-treated coal samples exhibited increased surface energy, hydrogen bonds and oxygen-containing functional groups, whereas the PAM-treated coal samples demonstrated the opposite trend. The surface energy of coal reflects the state of APG and PAM molecules adsorbed on the coal surface, and the polar force of surface energy in coal follows a quadratic relationship with the volume of gas displacement desorption. Increasing the number of hydrogen bonds and oxygen-containing functional groups can improve wettability and decrease the interaction force between coal and methane molecules. This contributes to the lower atmospheric desorption of the APG-treated coal samples at high pressure. The total desorption volume of the APG-treated coal samples was 10–34% of that of the original coal at 0.737, 1.027, and 2.004 MPa gas pressures. The total desorption volume of PAM-treated samples at 2.004 MPa was 2.3474 cm3/g, which exceeded that of the original coal. Therefore, APG and PAM promoted gas desorption, and wettability enhancement yielded better results. This study provides an experimental approach for selecting the best reagent and excellent guidance for field applications.

Research on the main control factors of gas desorption in middle and low rank coals based on orthogonal testing

To study the factors influencing gas desorption by middle rank and low rank coal, gas adsorption and desorption experiments of middle rank and low rank coal samples were designed with the orthogonal test method by considering the particle sizes, adsorption equilibrium pressures, temperatures and water contents of the coal samples, and the main factors affecting gas desorption from the middle rank and low rank coal samples were investigated. The results showed that there were obvious differences in the desorption capacity of the middle rank and low rank coals in the designed experimental scheme, and the maximum cumulative amounts of gas desorbed were 6.11 ml/g for Xinjiang low rank coal and 6.50 ml/g for Hebi middle rank coal. The relative sensitivities to the factors affecting gas desorption by Xinjiang low rank coal decreased in the order adsorption equilibrium pressure > particle size > water content > temperature, which the effect of adsorption equilibrium pressure on gas desorption from Xinjiang low rank coal was the most obvious and main controlling factor for gas desorption from Xinjiang low rank coal. The relative sensitivities to the factors affecting gas desorption by Hebi middle rank coal decreased in the order particle size > adsorption equilibrium pressure > temperature > water content, which the effect of particle sizes on gas desorption from Hebi middle rank coal was the most obvious and main controlling factor for gas desorption from Hebi middle rank coal. The cumulative amounts of gas desorbed from Xinjiang low rank coal first increased and then decreased with increasing coal grain sizes, and the cumulative amounts of gas desorbed from the Hebi middle rank coal gradually decreased with increasing coal grain size. The cumulative amounts of gas desorbed from both Xinjiang low rank coal and Hebi middle rank coal gradually increased with increasing adsorption equilibrium pressure.

Bio-accessibility and mobilization dynamics of soil vanadium during a 48-year vegetation restoration in a vanadium titano-magnetite tailings reservoir

Bio-accessibility of vanadium (V) in soils determines the effectiveness of vegetation restoration in the vanadium titano-magnetite tailings reservoirs because of persistent V toxicity, yet the variations in the bio-accessibility and mobilization of V in the soils with vegetation restoration remain elusive. Here, the bio-accessibility and mobilization of V in the soil-water interface were investigated along a 48-year vegetation restoration chronosequence in the Majiatian tailings reservoir using the diffusive gradients in thin films technique (DGT) and DGT-induced flux model. We found a low concentration of DGT-extracted V along the vegetation restoration chronosequence and the V fraction was dominated by the residual form, indicating a low V bio-accessibility in the soils. The bio-accessibility of V increased along the chronosequence because of the increased V resupply from solid phase, especially from the organic V fraction and the clay bound V. Low supply coefficient (R = 0.25) revealed a limited release of V from solid phase to soil solution. The kinetic resupply processes of V and its key regulating parameters were stage-specific during the vegetation restoration. The pool size of labile V in the soils determined the rapid V supply at the early and late stages, while the low desorption rate of V from the solid to liquid phase regulated the slow supply regime at the middle stage. The results of the present study highlight the importance of the long-term monitoring of soil V mobilization in the tailings reservoir because of the increased bio-accessibility and the dynamic supply of V during the vegetation restoration.

In-situ precipitation of ultrafine Mg2Ni particles in Mg-Ni-Ag metal fibers and their hydrogen storage properties

The intermetallic compound Mg2Ni shows improved hydrogen de-/absorption kinetics and a lower desorption temperature compared to pure Mg. However, the coarse Mg2Ni phase and its limited hydrogenation capacity restrict the application of the Mg2Ni alloy. In this study, an attempt was made to prepare Mg-Ni alloy fibers with a higher Mg content and a well-distributed Mg2Ni catalytic phase using the melt extraction (ME) method, and a unique metallic glass fiber was formed. With pre-annealing at 350 °C in a vacuum, uniformly dispersed Mg2Ni nanoparticles are in-situ formed, the phase transition is revealed to be metallic glass → Mg6Ni → Mg2Ni + Mg. About 1.5 wt% of hydrogen can be absorbed by the Mg-Ni fibers at 50 °C, and it is completely released in 8.8 min at 225 °C. Both the JMA and Kissinger models were utilized to accurately characterize the dehydrogenation activation energy, and the values of 90.4 and 95.8 kJ/mol were obtained, respectively. The hydrogen desorption process involves two distinct processes, the decomposition of Mg2NiH4 nanoparticles and MgH2 hydride in sequence, with dehydrogenation enthalpy changes of 64.5 and 78.2 kJ/mol, respectively. After hydrogen absorption and desorption cycles, a loose structure forms around the Mg2Ni nanoparticles. This structure serves as an efficient nucleation site for hydrides and provides diffusion paths for H atoms.

Unraveling the role of polysaccharide-goethite associations on glyphosate’ adsorption–desorption dynamics and binding mechanisms

HypothesisGlyphosate retention at environmental interfaces is strongly governed by adsorption and desorption processes. In particular, glyphosate can react with organo-mineral associations (OMAs) in soils, sediments, and aquatic environments. We hypothesize mineral-adsorbed biomacromolecules modulate the extent and rate of glyphosate adsorption and desorption where electrostatic and noncovalent interactions with organo-mineral surfaces are favored. ExperimentsHere we use in-situ attenuated total reflectance Fourier-transform infrared, X-ray photoelectron spectroscopy, and batch experiments to characterize glyphosate’ adsorption and desorption mechanisms and kinetics at an organo-mineral interface. Model polysaccharide-goethite OMAs are prepared with a range of organic (polysaccharide, PS) surface loadings. Sequential adsorption–desorption studies are conducted by introducing glyphosate and background electrolyte solutions, respectively, to PS-goethite OMAs. FindingsWe find the extent of glyphosate adsorption at PS-goethite interfaces was reduced compared to that at the goethite interface. However, increased polysaccharide surface loading resulted in lower relative glyphosate desorption. At the same time, increased PS surface loading yielded slower glyphosate adsorption and desorption kinetics compared to corresponding processes at the goethite interface. We highlight that adsorbed PS promotes the formation of weak noncovalent interactions between glyphosate and PS-goethite OMAs, including the evolution of hydrogen bonds between (i) the amino group of glyphosate and PS and (ii) the phosphonate group of glyphosate and goethite. It is also observed that glyphosate’ phosphonate group preferentially forms inner-sphere monodentate complexes with goethite in PS-goethite whereas bidentate configurations are favored on goethite.

Enhanced Water Sorption Performance of Polyacrylamide & Glass Fiber Paper Composites: Investigation and Comparison of Application in Desiccant Wheels.

The water sorption and desorption properties of solid adsorbent materials are crucial in rotary dehumidification systems. Metal organic frameworks (MOFs) and hydrogels are mostly at the laboratory stage due to factors like the synthesis process and yield. In this study, we utilized an eco-friendly and large-scale synthesis method to prepare polyacrylamide (PAM) hydrogels (yielding approximately 500 mL from a single polymerization). Subsequently, PAM was then coated onto glass fiber paper (GFP), which serves as a commonly employed substrate in desiccant wheels. By incorporating the hygroscopic salt LiCl and optimizing the content of each component, the water sorption performance of the composite was notably improved. The water sorption and desorption performances, as well as cycling stability, were evaluated and compared with composites containing aluminum fumarate, LiCl, and GFP (AlFum-LiCl&GFP). The results revealed that PAM-LiCl&GFP outperformed AlFum-LiCl&GFP in terms of sorption capacity throughout various relative humidity (RH) levels. It achieved a water uptake of 1.06 g·g-1 at 25 °C and 30% RH, corresponding to a water sorption rate coefficient K of 15.32 × 10-4 s-1. Furthermore, the lower desorption temperature (60 °C) resulting in a desorption ratio of 82.6%, along with the excellent cycling stability and effective performance as a desiccant wheel module, provide evidence for the potential application of PAM-LiCl&GFP in desiccant wheels.

The Catalytic Effect of Vanadium on Sorption Properties of MgH2-Based Nanocomposites Obtained Using Low Milling Time.

The effects of catalysis using vanadium as an additive (2 and 5 wt.%) in a high-energy ball mill on composite desorption properties were examined. The influence of microstructure on the dehydration temperature and hydrogen desorption kinetics was monitored. Morphological and microstructural studies of the synthesized sample were performed by X-ray diffraction (XRD), laser particle size distribution (PSD), and scanning electron microscopy (SEM) methods, while differential scanning calorimetry (DSC) determined thermal properties. To further access amorph species in the milling blend, the absorption spectra were obtained by FTIR-ATR analysis (Fourier transform infrared spectroscopy attenuated total reflection). The results show lower apparent activation energy (Eapp) and H2 desorption temperature are obtained for milling bland with 5 wt.% added vanadium. The best explanation of hydrogen desorption reaction shows the Avrami-Erofeev model for parameter n = 4. Since the obtained value of apparent activation energy is close to the Mg-H bond-breaking energy, one can conclude that breaking this bond would be the rate-limiting step of the process.

Non-silicate iron in mineral-associated organic matter of agro-chernozems located on different positions on the slope

Data on total non-silicate iron (Fed) content in mineral-associated organic matter (MAOM) of agro-chernozems of different localization on the slope are presented. The distribution of total non-silicate iron in soil profile follows that of organic carbon (OC): the maximum values are confined to the surface horizons, and decrease down the profile. It has been revealed that the change in the content of non-silicate iron in the MAOM of the clay fraction in arable horizons of eroded agro-chernozems is a result of erosion processes, including their intensity, which also depends, among other things, on the slope steepness. A lower slope steepness (4°) contributes to an increase in the organic carbon loading on iron oxides, resulting in an increased in iron desorption capacity, while a higher slope steepness (6°) results in lower iron desorption capacity. The OC/Fed molar ratio is suggested as an additional indicator of the degree of soil erosion. In clay fractions, of both their position in the soil profile and their position on the slope, the predominant mechanism of organic matter stabilization was the formation of organic-iron complexes (OC/Fed > 10). In the Residue fraction of humus horizons, non-silicate iron seems to be presented mainly as iron carbonates (FeCO3), while the proportion of microaggregates (stable under the sonication), where OM is mainly humin, is relatively low against the background of the absolute dominance of primary minerals in this fraction (weight %). Most of the non-silicate iron of mineralassociated OM extracted by dithionite-citrate-hydrocarbonate is localized in the clay fraction – 2/3 or more.

Promoted hydrogen storage properties of MgH2 by Ti3+ self-doped defect-mediated TiO2

Magnesium hydride (MgH2) has been expected as a promising solid material for efficiently storing hydrogen, but its practical applications have been impeded by stable thermodynamics and slow hydrogen desorption kinetics. In this study, we synthesized Ti3+ self-doped 3D TiO2 hollow nano-boxes (Ti3+@TiO2) through a facile hydrothermal reaction and investigated their influence on the hydrogen storage properties of MgH2. The abundant oxygen vacancies of Ti3+@TiO2 and the in-situ formed multivalent state of Ti-containing species during the de/re-hydrogenation process resulted in an excellent catalytic effect on the hydrogen storage properties of MgH2. The BM-MgH2-Ti3+@TiO2-5 composite exhibited a low initial hydrogen desorption temperature of 205.4 °C, 49.2% reduction compared to pristine MgH2. The BM-MgH2-Ti3+@TiO2-5 composite could release 6.1 wt% of hydrogen at 325 °C within 20 min, and the activation energy (Ea) of dehydrogenation was decreased significantly to 57.2 ± 1.4 kJ/mol, achieving superior hydrogen desorption kinetics. In addition, this composite also demonstrated remarkable cycling stability, with hydrogen capacity retention of 93.7% after 10 consecutive de-/rehydrogenated cycles at 325 °C. Our findings provide a new horizon for designing highly active catalysts for promoting the hydrogen storage properties of Mg-based materials.

A one- and three-dimensional coupled model and simulation investigation for the large-scale oil-heating type Mg-based hydrogen storage tank

A large-scale oil-heating type Mg-based hydrogen storage tank is the key device for the high-efficiency and high-safety Mg-based solid hydrogen storage and transportation. However, the complicated heat and mass transfer in the Mg alloy bed and oil tube during the hydrogen desorption process impede the design of high-performance hydrogen storage tanks. In this work, a one- and three-dimensional coupled model considering the impact of oil velocity and temperature on the internal heat and mass transfer was developed to simulate the hydrogen desorption process of large-scale oil-heating type Mg-based hydrogen storage tanks. This model was then solved by the finite element method, and the simulation results agreed well with the experimental data obtained from an Mg-based hydrogen storage tank. Moreover, simulation results indicate that the oil velocity has a considerable impact on the hydrogen desorption performance of the Mg-based hydrogen storage tank, and a recommended oil velocity of 4 m s−1 was identified. In addition, high oil temperature and low hydrogen desorption pressure benefit the hydrogen desorption performance, thus should be determined by the application scenarios. Besides, the complete hydrogen desorption time was barely affected by the initial bed temperature, which is suggested as ≥ 573 K to meet the high rate requirement of hydrogen supply, otherwise as room temperature to reduce energy costs. The model and simulation results presented in this work provided a foundation for the design of high performance large-scale oil-heating type Mg-based hydrogen storage tanks that can be applied practically in the field of hydrogen energy.

Improved hydrogen storage properties of low-cost Ti–Cr–V alloys by minor alloying of Mn

V-based BCC solid-solution alloys have been considered as promising hydrogen storage materials due to their high hydrogen storage capacity; however, the low effective hydrogen desorption capacity and high cost of pure V have limited their practical application in fuel cell vehicles or devices. Herein, a low-V TiCr1.2(V–Fe0.203)0.6 hydrogen storage alloy with a hydrogen storage capacity of 3.35 wt% has been developed by using a low-cost FeV80 as raw material. To further increase the effective hydrogen desorption capacity, cheap Mn is first used to partially substitute for Cr in FeV80-based alloy. The Mn substitution alloy achieves an effective hydrogen desorption capacity of 2.07 wt% cutting-off at 0.1 MPa with good activation performance. It is ascribed that the minor alloying of Mn increases the dehydrogenation plateau pressure and reduces the hysteresis and the enthalpy change value. The dehydrogenation enthalpy decreases from 34.84 kJ/mol to 31.51 kJ/mol. The synergistic effect of Mn and Fe increases the abundance of the C14 Laves phase, which plays a catalytic role in hydrogen absorption and desorption. The cost of TiCr1.1Mn0.1(V–Fe0.203)0.6 alloy is much lower than that of using pure V, and even lower than some AB2 alloys based on cost estimation. The results of this study would provide a reference for the application of low-cost Ti–Cr-(FeV80) alloys for hydrogen storage.

Kinetic research on ion exchange regeneration of quaternary ammonium-based CO2 sorbent for direct air capture

To satisfy the Paris Agreement's 1.5 °C goals, direct air capture (DAC) has become an increasingly crucial technology. However, the ultralow partial pressure of CO2 in ambient air contributes to a low desorption rate and high regeneration energy consumption. In this study, we proposed a fast regeneration method for CO2 sorbents based on an ion exchange process. Utilizing an alkaline solution rich in hydroxide (OH–) ions, the quaternary ammonium (QA)-based ion exchange resin can be changed from carbonate (CO32–) to OH– form, which directly captures CO2 from ambient air. The results showed that the working capacity of the sorbents in the OH– form was 1.85 mmol⋅g−1, which was double that of the CO32– form (0.88 mmol⋅g−1). The kinetics showed that the ratio of OH–/HCO3– at inlet, concentration, and external diffusion influence the desorption rate of CO32– because of the ion exchange reaction. With a high ratio of OH–/HCO3– at inlet, 1 M alkaline solution, and 3 mL⋅s−1 cyclic flow rate, the desorption time of the sorbents was approximately 20 min. Finally, because the energy consumption of the entire process comprises mainly electric energy required to regenerate the alkaline solution after ion exchange, it is expected to establish an electrochemical DAC system to utilize renewable energy efficiently.

The Effect of Temperature and Calcium Cloride Extract on Zinc Desorption in Changed Calcareous Soils

Zinc desorption studied for ten soils was variance in calcium carbonate, clay percent, and organic matter from Duhok province in the north of Iraq involved (Bamarny, Zawita Assih, Semeel, Kanimasi-1& 2, Khanke, Zakho, Batofa, and Faydi, locations). Soil testers after air dried up ground and filtered through a 2-mm sieve was taken to know the properties of the soils, zinc forms and desorption. Results showed the soluble, available, exchangeable and zinc total alternated among (0.29 - 0.94), (0.88 - 1.64), (1.71 - 2.05), and (12.25 - 56.15) mg.kg−1 one-to-one, Zn desorption raise with the raising of Zn added to research soils, extraction concentration CaCl2 from 0.1 to 1 molarity and temperature. Higher quantity of Zn release at 298K, was found in the soil of Kanimassi-1 (31.40 - 264.81) μg. g−1 at 0.1M, 1M CaCl2 extraction respectively, it may be owing to the high value of available phosphorus, CEC and organic matter and lower quantity of available-Zn and CaCO3. But the lowest amount observed in Faydi soil (14.10-118.69) μg. g−1. The high desorption of Zn at 321K, noted in Faydi soil between (50.50 - 421.00) μg. g−1 and low amount in Semeel soil between (26.35 - 222.10) μg.g−1 at 0.1 to 1M CaCl2 extraction respectively, designated Zn released more with increasing temperature. In general low quantity of Zn releases as of all researched soils causes to the great amount of CaCO3, quality and amount of clay minerals dominant that cause raise Zn bonding also low desorption from all studied soils. The effect of CaCl2 extraction concentration to increase Zn desorption was more than the effect of temperature in all soils.

Comparative investigation on Ni(II) removal from electroplating wastewater by mineral adsorbent (CSAM) and ion-exchange resins

ABSTRACT The efficiency of Ni(II) removal from electroplating wastewater is highly correlated with different adsorption materials. A Ca-Si activated mineral adsorbent (CSAM) and two ion-exchange resins (732 and D152) were compared. The adsorption of Ni (II) by three materials is spontaneous and endothermic, and their adsorption capacities are similar (48.66–65.36 mg/g at 318K), but the dosage of CSAM is less (1.0 g/L for 50 mg/L Ni(II)), its adsorption is faster (<5 min) and pH range is wider (2–7). 10% NaCl, 1 mol/L HCl and 10% NaCl +1 mol/L HCl were used as desorbent agents, and CSAM exhibited an extremely low desorption rate (1.49–3.41%). The smaller separation factor (close to 0) and XPS analysis showed that the Ni(II) adsorption on CSAM was an irreversible chemical process, which was different from the three-stage adsorption of resins. The treatment of two kinds of electroplating wastewater with high and low concentration showed that CSAM not only had a higher Ni(II) removal rates (>98.4%), but also could efficiently remove Cu(II) (>98%), total-chromium (>79%) and COD (>66%). The treatment of Ni(II) containing electroplating wastewater with ion-exchange resins is greatly affected by the complexing agent. CSAM is more suitable for the treatment of electroplating wastewater containing various metals and organic matters.

Tailoring hydrogenation and anti-oxidation properties of titanium - iron - chromium alloys by regulating zirconium content at room temperature

The effects of Fe substitution by Zr on the microstructure, hydrogen storage properties and oxidation resistance of the TiFe0.85-xCr0.15Zrx (x = 0, 0.05, 0.10, 0.15) alloys are studied in this work. It is shown that all the alloys are consisted of TiFe phase, MgZn2-type phase and minor Ti phase. The introduction of Zr causes no change for the TiFe main phase. All the alloys absorb hydrogen directly under mild conditions without any activation process. As Zr content increases, the maximum hydrogen storage capacity of the first hydrogenation increases while the reversible hydrogen storage capacity decreases. The marked change of the first hydrogenation properties may be due to the formation of the bright phase (MgZn2-type phase). The decrease of the reversible hydrogen storage capacity is due to the formation of the stable hydrides Cr2ZrH3 and TiH2, which start to decompose at around 700 °C. During the air exposure test, the alloys with higher Zr content show good oxidation resistance. For the PCT measurement, the alloys with higher Zr show lower hydrogen absorption and desorption platform pressure, which means more stable hydrides are formed during the first hydrogenation. Moreover, the rate limiting step model of the first and fifth hydrogenation processes of all the alloys has also been investigated in detail.

Thermodynamic analysis of an efficient pressure-swing CO2 capture system based on ionic liquid with residual pressure energy recovery

In this work, an efficient pressure-swing ionic liquid-based CO2 capture system with residual pressure energy recovery is proposed. In this system, the N2–O2 mixture from flue gas which is not absorbed by the ionic liquid in the absorber flows into the turbine to recover the energy for the purpose of reducing energy consumption. 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) are selected as the capture solvent and a comprehensive thermodynamic analysis is performed. The total energy consumption of the new system is 1.770 GJ/tCO2 under design conditions which is 28.45% lower than the conventional system for [Bmim][BF4] and 1.737GJ/tCO2 which is 28.84% lower than the conventional system for [Bmim][PF6]. The effect of absorption pressure, desorption temperature, heat storage fluid flow rate, distribution ratio of heat storage fluid in the intercooler, flue gas composition and type of heat storage fluid on system thermodynamic performance were analyzed. The result shows that relatively lower capture pressure, the lower desorption temperature, the lower heat storage fluid flow rate, the more heat storage fluid distributed in the first intercooler and the higher CO2 fraction in flue gas can improve the thermodynamic performance of the system. Also, the exergy analysis represents that cold tank and the capture module are the two components with maximum exergy destruction. And the comparison results with the conventional system show that the new system has significantly lower energy consumption and capture cost.