Pristine Ca Research Articles

Utilization of MOF‐enhanced hydrophilic nanocomposite reverse osmosis membrane for desalination with antifouling capabilities

AbstractCellulose acetate (CA) membranes used in reverse osmosis (RO) desalination techniques often face fouling challenges. In this experimental study, the phase inversion method was employed to investigate the incorporation of graphene oxide nanoparticles (GONP) metal–organic frameworks (MOF), into the casting solution for composite CA‐RO membranes. The effects of varying GONP concentrations on fouling resistance and hydrophilicity were evaluated using scanning electron microscopy (SEM), contact angle measurements, and water content analysis. The results demonstrated that the modified CA membrane with 0.05 wt% GONP exhibited improved water permeability (10.3 L/m2 h) and salt rejection (95.8%) compared with the pristine CA membrane. These improvements stem from increased hydrophilicity and reduced fouling. This study's findings suggest that incorporating GONP into the polymeric doped solution can effectively mitigate fouling issues and enhance the performance of RO membranes in desalination applications.Highlights GONP enhances hydrophilicity, reducing fouling in desalination. Effects of varying GONP concentrations were studied. GONP‐CA membrane shows better permeability and salt rejection than pristine. Nanocomposite membranes promise in overcoming fouling in RO membranes.

Artificial Hybrid Solid Electrolyte‐Mediated Ca Metal for Ultradurable Room Temperature 5 V Calcium Batteries

The anodic stability and reversibility of Ca metal electrodeposition/dissolution have always been hampered by surface passivation and anion corrosion, especially in F‐based carbonate ester electrolytes at high device voltages. To avoid direct Ca metal/electrolyte reactions, an artificial hybrid solid electrolyte layer (AHSEL), which is characteristic of sodium/calcium carbonate and calcium hydride nitride nanocrystals of size <10 nm encapsulated by amorphous C, N species, is constructed on calcium with good ion conductivity (≈0.01 mS cm−1) and uniform coating of thickness ≈20 μm. After cycling in the KPF6 electrolyte, AHSEL is transformed into Na/K/Ca hybrid solid electrolyte interphases (SEIs), which is a compact layer composed of monodisperse nanocrystals (mostly Ca2NH) and small amorphous zones, thus greatly suppressing the fluoridation of the Ca deposit. Consequently, the plating/stripping performance of AHSEL‐modified Ca (AHSEL‐Ca) is markedly improved compared with that of pristine Ca, lasting for >1400 h at a polarization shift of <0.4 mV/h. The AHSEL‐Ca anode also endows Ca batteries with superior anodic stability with a ceiling voltage of up to 5.0 V, a high discharge voltage (>3.3 V), a large capacity of ≈80 mAh g−1 at 200 mA g−1, and an ultralong lifespan ≈5000 cycles.

Carbyne Ring Activated Using ZnCl2 for Hydrogen Adsorption: DFT Study.

We have studied the feasibility of activated carbyne as a good hydrogen storage material. Density functional theory (DFT) simulations through van der Waals interactions have been applied to investigate calcium sorption on activating carbyne with zinc dichloride (ZnCl2) and also interactions of molecular hydrogen with pristine carbyne and Ca functionalized on an activated carbyne C12-ring. The obtained results showed that (i) the chemical activation of the C12-ring with ZnCl2 increases its area by 5.17% with respect to pristine carbyne. (ii) Ca atoms at small concentrations tend to get atomically sparse on carbyne, donating +0.94e and +1.05e to the ring, according to Mulliken population analysis and the electrostatic potential fitting charges, respectively. Furthermore, in the presence of calcium, hydrogen sorption increases by 21.8% in comparison with Ca-decorated pure carbyne. (iii) Seven hydrogen molecules per Ca atom have adsorption energy close to the range of ∼0.3–0.5 eV per H2, which is necessary for effective charge/discharge cycles. (iv) Theoretical uptake (7.11 wt %) with a single Ca atom is higher than the U.S. Department of Energy target (5.5 wt %). Therefore, an activated C12-ring can bind three Ca atoms with its seven H2 molecules reaching 13.8 wt %. (v) Equilibrium pressure for CaC12–7H2 and Ca3C12–21H2 systems (5–15 MPa) by means of adsorption isotherm calculations. The calculated van’t Hoff desorption temperatures exceed considerably the boiling point of liquid nitrogen. In addition, we also performed DFT-based molecular dynamics simulations for the C12, CaC12, CaC12–7H2, and Ca3C12–21H2 systems to study thermal stability. Our results confirm the potential of Ca-decorated carbyne for hydrogen storage.

Remarkable adsorption for hazardous organic and inorganic contaminants by multifunctional amorphous core–shell structures of metal–organic framework-alginate composites

• CA-MIL-53-AC were synthesized via a one-pot method for removing DDT, As(V), and F. • Composite beads showed superior textural properties and abundant reactive functional groups. • CA-MIL-53-AC had higher adsorptive capacity than the other beads for DDT, As(V), and F. • Plausible mechanisms were identified to provide insights in the contaminants removal. Novel metal–organic framework-alginate composite beads (CA-MIL-53-AC) were synthesized using sodium alginate (gelling agent) and calcium chloride (complexing agent) via a one-pot and dropping method to selectively remove the dichlorodiphenyltrichloroethane (DDT), arsenate (As(V)), and fluoride in an aqueous solution. To evaluate the characteristics of the synthesized composite beads, scanning electron microscopy, X-ray diffraction, Fourier-transform infrared, X-ray photoelectron spectroscopy, thermal gravimetric analysis, zeta potential, and porosimetry techniques were used in this study. The adsorption kinetics showed that DDT, As(V), and fluoride removal could be described by the pseudo-first-order model. Also, the adsorption isotherms indicated that DDT and As(V)/fluoride removal followed the Langmuir and Freundlich models, respectively. Compared with granular AC and pristine CA, CA-AC, and CA-MIL-53, the CA-MIL-53-AC showed superior adsorption performance for all target contaminants (5.29, 4.89, and 3.18 mg/g for DDT, As(V), and fluoride, respectively). The adsorptive behavior for DDT was spontaneous, exothermic, and highly favorable based on thermodynamics calculations. Furthermore, the regenerated composite beads showed high removal capacity for DDT after the third recycle. The continuous DDT adsorption in the fixed-bed column at different flow rates were well fitted using Thomas, Adams–Bohart, and Yoon–Nelson models. The plausible mechanisms for the DDT, As(V), and fluoride removal by CA-MIL-53-AC were identified as hydrophobic and π–π interactions, ion exchange, surface complexation, and hydrogen bonding. These findings provide significant insight to remove DDT, As(V), and fluoride from water for practical applications.

Study on Sensitivity and Drug Loading Characteristics of Graphene‐like BN Nanosheets to Indomethacin Based on DFT

AbstractThe sensitivity and the drug loading characteristics of the doped BN nanosheet (BNNS) to indomethacin (INDO), a analgesic, anti‐inflammatory and antipyretic drug, were studied by using density functional theory. The adsorption energy calculated results show that the pristine BNNS can't be used to detect INDO, so that it can't be used as a potential efficient sensing materials to INDO. C, Si, Al, Ga doping enhances the absolute value of adsorption energy, and the recovery time is acceptable in practical application. All the elements studied (C, Si, Al, Ga, P, Cl) narrow the effective band gap, resulting in an increase of the electrical conductivity of INDO/BNNS complexes. These findings indicate the suitable doping improves the sensitivity of BNNS as sensing material to INDO, Si is the most efficient element. The INDO load on BNNS can be increased by the C, Si, Al, Ga doping. The sustained or controlled release of the INDO may be achieved by adjusting the doping of BNNS. Analysis of global reactivity descriptors show that the C, Si doping leads to the most reactive complexes. The solubility of INDO/doped BNNS complex can be modulated by the doping, and therefore BNNS can be as the carriers for poorly water‐soluble drugs. Comprehensive consideration of the adsorption energy, global reactivity descriptors and solubility, it is concluded that Si doped BNNS is most suitable as an INDO carrier.These results encourage a further investigation of BN nanosheet as a drug nanocarrier.

Surface Characteristics of Electrospun p-Sulphonated Calix[4]Arene Functionalized Cellulose Acetate Nanofiber and Its Behaviour towards Methylene Blue Adsorption

p-sulphonated calix[4]arene ( p-SOCX) functionalized cellulose acetate/graphene oxide (CA/GO) nanofibers were successfully prepared via the electrospinning technique. The presence of p-SOCX within the fiber matrix was ascertained using Fourier Transform Infrared spectroscopy and Carbon-Hydrogen-Nitrogen-Sulphur elemental analyses. Apparent changes in morphology of the samples were observed under scanning electron microscope where fiber diameters increased with increasing p-SOCX content. Preliminary dye removal test at different pH, dosage, and temperature of functionalized CA/GO nanofiber demonstrates enhanced adsorption capacity of methylene blue in presence of p-SOCX compared to pristine CA nanofiber and CA/GO nanofiber at an optimum pH 8. The highest removal efficiency obtained was 88.84% with initial methylene blue dye concentration of 10 mg/L, adsorbent dosage of 20 mg/10 mL, contact time of 30 min at room temperature ca. 293 K.

Visible Light-Driven GO/TiO2-CA Nano-Photocatalytic Membranes: Assessment of Photocatalytic Response, Antifouling Character and Self-Cleaning Ability.

Photocatalysis and membrane technology in a single unit is an ideal strategy for the development of wastewater treatment systems. In this work, novel GO (x wt%)/TiO2-CA hybrid membranes have been synthesized via a facile non-solvent induced phase inversion technique. The strategy aimed to address the following dilemmas: (1) Effective utilization of visible light and minimize e−/h+ recombination; (2) Enhanced separation capability and superior anti-fouling and self-cleaning ability. The experimental results reveal that the integration of nano-composite (GO/TiO2) boosts the membrane properties when compared to pristine CA and single photocatalyst employed membrane (GO-CA and TiO2-CA). The effect of GO content on the properties of the photocatalytic membrane has been determined by utilizing three different ratios of GO, viz. 0.5 wt%, 1 wt%, and 2 wt% designated as NC(1)-CA, NC(2)-CA, and NC(3)-CA, respectively. Amongst them, NC(3)-CA membrane showed state-of-the-art performance with an elevated photocatalytic response (four times higher than pristine CA membrane) toward methyl orange. Moreover, the water flux of NC(3)-CA membrane is 613 L/m2h, approximately three times higher than bare CA membrane (297 L/m2h), while keeping the MO rejection high (96.6%). Besides, fouling experiments presented the lowest total and fouling resistance ratios and a higher flux recovery ratio (91.78%) for the NC(3)-CA membrane, which endows the membrane with higher anti-fouling and self-cleaning properties. Thus, NC(3)-CA membrane outperforms the other as synthesized membranes in terms of separation efficiency, visible light photo-degradation of pollutant, anti-fouling and self-cleaning ability. Therefore, NC(3)-CA membrane is considered as the next generation membrane for exhibiting great potential for the wastewater treatment applications.

Development of highly ionic conductive cellulose acetate-g-poly (2-acrylamido-2-methylpropane sulfonic acid-co-methyl methacrylate) graft copolymer membranes

A novel cellulose acetate-g-poly (2-acrylamido-2-methylpropane sulfonic acid-co- methyl methacrylate) copolymer was prepared via free radical polymerization for the first time. The chemical structure of the graft copolymer was confirmed using FT-IR, 1H NMR and EDX. The TGA and DSC investigated the thermal changes. Factors affecting the grafting process were studied and various grafting characteristic parameters such as grafting efficiency (%), grafting yield (%) and add-on value (%) were determined. Flexible membranes based on different graft copolymer compositions were fabricated by simple solution casting. Physicochemical properties including ion exchange capability (IEC), water uptake (WU) and proton conductivity (σ) were evaluated. These membranes demonstrated higher IEC, WU and conductivity than the pristine CA. The maximum proton conductivity of the CA-g-poly (2-acrylamido-2-methylpropane sulfonic acid-co- methyl methacrylate) copolymer membrane (68%; Add-on %) was found to be 6.44 × 10−3 S/cm compared with 0.035 × 10−3 S/cm of the pristine CA. Thus, the appropriate graft copolymer composition will allow fine-tuning of the physical characteristics and led to several potential applications, such as polyelectrolyte fuel cells membranes or biodiesel production.

Investigating the Antibacterial Activity of Polymeric Membranes Fabricated with Aminated Graphene Oxide.

A novel, functionalized graphene oxide–based cellulose acetate membrane was fabricated using the phase inversion method to improve the membrane characteristics and performance. We studied the effect of aminated graphene oxide (NH2–GO) composite on the CA membrane characteristics and performance in terms of membrane chemistry, hydrophilicity, thermal and mechanical stability, permeation flux, and antibacterial activity. The results of contact angle and water flux indicate the improved hydrophilic behavior of composite membranes in comparison to that of the pure CA membrane. The AGO-3 membrane showed the highest water flux of about 153 Lm−2h−1. The addition of hydrophilic AGO additive in CA membranes enhanced the antibacterial activity of AGO–CA membranes, and the thermal stability of the resulting membrane also improved since it increases the Tg value in comparison to that of a pristine CA membrane. The aminated graphene oxide (NH2–GO) was, therefore, found to be a promising additive for the fabrication of composite membranes with potent applications in wastewater treatment.

Role of intercalated water in calcium hydroxide interlayers for carbonation reaction

Carbonation of calcium hydroxide (Ca(OH)2) is an indispensable process with applications in the stable storage of CO2, geological disposal of radioactive waste, and cement manufacture for the construction industry. In the carbonation reaction of Ca(OH)2, water plays an important role in the conversion of CO2 and increases the thermodynamic stability of calcium carbonate. Therefore, understanding the interaction between water and Ca(OH)2 is essential for controlling the kinetics and thermodynamics of the carbonation reaction of Ca(OH)2. In this study, changes in the physical and chemical properties of Ca(OH)2 that appear before the carbonation of hydrated Ca(OH)2 were observed through XRD and NMR analyses. Through XRD analysis, the interplanar distance of hydrated Ca(OH)2 increased by approximately 0.39% compared to that of the pristine Ca(OH)2. Furthermore, we quantified the intercalated water through NMR analysis based on water signal appearing around 0.9 ppm, which was approximately 3.0–7.0 wt% of Ca(OH)2. Through theoretical calculations, the hydrated Ca(OH)2 formed a stable structure with intercalated water molecules, resulting in lower reaction barrier and heat of reaction of the Ca(OH)2 carbonation. For the first time, the intercalation of water between the Ca(OH)2 interlayers is observed, and its importance in the carbonation reaction is established.

Synthesis and Characterization of Novel Integral Asymmetric Monophasic Cellulose-Acetate/Silica/Titania and Cellulose-Acetate/Titania Membranes.

Two series of novel integral asymmetric monophasic hybrid membranes, cellulose acetate/silica/titania (CA/SiO2/TiO2—series 1) and cellulose acetate/titania (CA/TiO2—series 2), were developed by the coupling of sol-gel technology and a modified version of the phase inversion technique. SEM micrographs confirmed the integral asymmetric structure of all membranes. ATR-FTIR and ICP-OES results showed that, for the membranes in series 1, TiO2 is covalently bound to SiO2, which, in turn, is covalently bound to CA, while for the membranes in series 2, TiO2 is directly and covalently bound to the CA matrix. Permeation experiments revealed that the permeation performance of the membranes in series 1 is unaffected by the introduction of TiO2. In contrast, the introduction of TiO2 in the series 2 membranes increased the hydraulic permeability by a factor of at least 2 when compared to the pristine CA membrane and that incremental additions of TiO2 further increased the Lp.

Tuning the synthetic conditions of graphene oxide/magnetite/ hydroxyapatite/cellulose acetate nanofibrous membranes for removing Cr(VI), Se(IV) and methylene blue from aqueous solutions

The discharge of high toxic contaminations of heavy metals and dyes to water resources has posed severe problems for the eco-system and human health. In this work, electrospun nanofibrous membranes of cellulose acetate containing fillers of graphene oxide (GO), magnetite nanoparticles (MNPs) or hydroxyapatite (HAP) were fabricated. It was shown that the membranes were configured in randomly oriented fibers with diameters around 0.11−0.35 μm and 0.66–1.23 μm, 0.14−0.33 μm and 0.6−0.89 μm, 0.17−0.37 μm and 0.91–4.57 μm 0.18−0.53 μm and 1.18–2.1 μm and 0.11−0.29 μm for CA, GO@CA, MNPs@CA, HAP@CA and GO/MNPs/HAP@CA, respectively. The observed surface roughness tends to be promoted upon supplementations, as the roughness average (Ra) increased from 31.3 nm to 52 nm for CA and GO/MNPs/HAP@CA, respectively. The estimated toughness indicated that values increased from pristine CA reaching to its highest one at MNPs@CA as 2.5 ± 0.2 MJ/m3 to 8.2 ± 0.5 MJ/m3, respectively. The Se(IV) and Cr(VI) removal from aqueous solutions using the nanofibrous membranes was examined upon the time and pH value of the media. The removal efficiency for Se(IV) has improved from 89.3 % at pH 4–96 % for GO/MNPs/HAP@CA. Moreover, Cr(VI) removal progressed from 86.7, 86.3, 89.9, 90.6 and 92.9 % at pH 4–89.8, 90.5, 94.1, 94.7 and 97.3 % at pH 8 for CA, GO@CA, MNPs@CA, HAP@CA and GO/MNPs/HAP@CA, respectively. The degradation of methylene blue (MB) was investigated and reached its highest value of 95.1 % for GO/MNPs/HAP@CA after 35 min of continuous irradiation under visible light.

Fabrication of amino-modified electrospun nanofibrous cellulose membrane and adsorption for typical organoarsenic contaminants: Behavior and mechanism

Herein, an amino-modified electrospun nanofibrous cellulose membrane (CA-PVAm) was prepared and employed to adsorb the typical organoarsenic contaminants (roxarsone (ROX), p-arsanilic acid (p-ASA), and phenylarsonic acid (PAA)). The SEM, FT-IR, and XPS results showed that the CA-PVAm composed of abundant nanofibres and owned ample functional groups such as NH2, OH, and CO groups. The batch experiments demonstrated that the CA-PVAm exhibited excellent adsorption performance on ROX (186.22 mg g−1), p-ASA (69.15 mg g−1), and PAA (62.77 mg g−1), which were 15.98, 6.83, and 6.25 folds larger than those of the pristine CA. In addition, the adsorption process of ROX, p-ASA, and PAA on CA-PVAm accorded with the Langmuir model and obeyed the pseudo-second-order model with intraparticle diffusion. Meanwhile, the adsorption of ROX and PAA was endothermic process, but the exothermic process was observed during the p-ASA adsorption. Furthermore, the main adsorption mechanisms involved electrostatic interactions and hydrogen-bonding interactions. The formed stable six-membered structure between NH2 and NO2 groups could significantly enhance the hydrogen-bonding interactions between CA-PVAm and ROX molecule, resulting in evident improvement in ROX adsorption. Importantly, the CA-PVAm displayed outstanding reusability (4 cycles) and rapid desorption rate. This study probably provides an important theoretical and experimental basis for the remediation of the emerging organic pollutants.

Optical, photocatalytic properties of novel pyro- stannate A2Sn2O7 (A=Ce, Ca, Sr), and Pt deposited (SrCe)2Sn2O7 for the removal of organic pollutants under direct solar light irradiation

The pyrochlore phase structured pristine Ce2Sn2O7, Ca and Sr cationic ions substituted Ce2Sn2O7 and Pt deposited (SrCe)2Sn2O7 photocatalysts have been prepared successfully by hydrothermal methods for environmental applications. The various physicochemical properties were characterized by several techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), photoluminescence (PL) and UV–Vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS). Substituting the alkaline earth elements such as Ca, Sr to lattice cerium in the Ce2Sn2O7 could lead to changes in the optical as well as the photocatalytic properties. The Pt deposited (SrCe)2Sn2O7 pyrochlore resulting the highly separated photogenerated carriers through the transfer of electrons, which is helpful to the photocatalytic performance. The Pt supported pyrochlore showed increased photocatalytic degradation of 4-Nitrophenol, RhB, MB and ciprofloxacin. The cyclic stability of the prepared materials was inspected; it was observed that the photo-catalyst is active for several cycles. The stimulated photocatalytic efficacy can be attributed to the extended response to the visible light, highly improved charge separation due to cationic substitution. Furthermore, super-oxide and hydroxyl are noticed to be the most important reactive species during the photo-degradation process. Our work provides a new path way to develop high performance stannate photocatalysts with the help of surface Plasmon resonance effect of Nobel metal nanoparticles, thus could widening the family of photocatalysts available for water treatment.

Capric acid/intercalated diatomite as form-stable composite phase change material for thermal energy storage

Leakage issue and low thermal conductivity largely restrict feasibility of fatty acid in real application of thermal energy storage (TES). In this paper, a novel form-stable phase change material (FSPCM) capric acid/diatomite (CA/DT) for TES was prepared using direct impregnation method by using CA as PCM and diatomite as supporting material. The fabricated composites were investigated in detail via the leakage test to determine the optimization proportion, and the real mechanism of preventing leakage by diatomite was analyzed. The characterization techniques such as thermogravimetric analysis, differential scanning calorimetry, intelligent paperless recorder technology, Fourier transform infrared spectrometer and scanning electron microscopy were applied to systematically investigate the thermal properties, microstructure and thermal compatibility of the prepared composites. The results showed that the maximum mass ratio of CA adsorbed into DT without leakage is as high as 50 mass%, which is mainly ascribed to the porous structure of DT. The selected FSPCM has a melting point of 34.9 °C and latent heat of 89.2 J g−1. What is more, the CA/DT FSPCM exhibits a distinctly enhanced thermal stability by TG analyses. The heat transfer efficiency of the CA/DT FSPCM is higher than that of pristine CA. Due to the high adsorption capacity, high latent heat, good thermal stability as well as low cost, the CA/DT FSPCM can be considered as potential materials for thermal energy storage.

Nano-biopolymer effect on forward osmosis performance of cellulosic membrane: High water flux and low reverse salt

Chitosan nano-biopolymers (CS-NPs) were synthesized, and nanocomposite membranes were prepared via phase inversion method. The synthesized CS-NPs and fabricated membranes were characterized using TEM, SEM, AFM, hydrophilicity analysis and porosity measurement techniques. Surface hydrophilicity and porosity of nanocomposite membranes considerably increased compared with pristine CA membrane, and structural parameter significantly decreased to 0.30–1.3 mm. Nanocomposite membranes presented superior forward osmosis (FO) performance by offering a high water flux and low reverse solute flux compared with CA so that optimum osmotic water flux reached 31.2 LMH, about four times higher than that of unmodified membrane. In this regard, reverse salt flux remarkably reduced from 2.33 gMH for pristine membrane to 0.09 gMH for nanocomposite membrane demonstrating efficacy of employed modification method in simultaneous improvement of both water and reverse salt flux. Nanocomposite membrane applicability was also investigated in desalination of seawater proving the satisfactory performance of membranes in FO.

Synthesis, structure and the dehydrogenation mechanism of calcium amidoborane hydrazinates.

The calcium amidoborane hydrazinates, Ca(NH2BH3)2·nN2H4, were firstly synthesized by reacting different molar ratios of Ca(NH2BH3)2 and N2H4. In particular, Ca(NH2BH3)2 and N2H4 with a molar ratio of 1 : 2 crystallizes into the orthorhombic symmetry P212121 space group with the lattice parameters of a = 6.6239(4) Å, b = 13.7932(6) Å, c = 4.7909(2) Å. The dehydrogenations of calcium amidoborane hydrazinates are two-step reactions, exhibiting superior dehydrogenation properties compared with those of pristine Ca(NH2BH3)2. For Ca(NH2BH3)2-1/2N2H4, approximately 4.6 equiv. hydrogen (or 7.9 wt% hydrogen) can be released at 150 °C. Kinetic analysis shows that the activation energies for the two steps of hydrogen desorption from Ca(NH2BH3)2·2N2H4 are much lower than those of pristine Ca(NH2BH3)2, suggesting an improvement in the dehydrogenation kinetics of Ca(NH2BH3)2 after coordinating with N2H4. Isotopic labeling results show that the driving force for the dehydrogenation of calcium amidoborane hydrazinates is the combination mechanism of protonic hydrogen and hydridic hydrogen (H(δ+) and H(δ-)). In addition, initial H2 release from calcium amidoborane hydrazinates originates from the interaction of [-BH3] and N2H4, rather than [-BH3] and [-NH2] (in [-NH2BH3]).

Improved hydrogen storage properties of combined Ca(BH4)2 and LiBH4 system motivated by addition of LaMg3 assisted with ball milling in H2

A combined Ca(BH4)2+LiBH4 system with improved hydrogen storage properties is obtained by the addition of a particulate LaMg3 alloy assisted with ball milling in a H2 atmosphere. It is found that LaMg3 is mostly hydrogenated to symbiotic low crystalline MgH2 and amorphous La-containing hydride of fine particles after the milling, which are homogenously embedded in the Ca(BH4)2+LiBH4 matrix. The multi-hydride system shows significant improvements in both hydrogen storage thermodynamics and kinetics. Particularly, the system with LaMg3 addition in a molar ratio of 0.3 shows an overall superior hydrogen storage property. The main dehydrogenation starts from ca. 200 °C, which is 100 °C lower than the main dehydrogenation temperature of the pristine Ca(BH4)2+LiBH4 system. Re-hydrogenation initiates at a low temperature of ca. 150 °C, and the system maintains 70% of its first hydrogen desorption capacity after 5 cycles. The mechanism of the improved hydrogen storage properties of the combined system is discussed.

Improvement on Hydrogen Desorption Performance of Calcium Borohydride Diammoniate Doped with Transition Metal Chlorides

Calcium borohydride diammoniate with a molecular formula of Ca(BH4)(2).2NH(3) is a novel complex hydride for hydrogen storage. However, it suffers from high temperature and sluggish kinetics for hydrogen desorption. In this work, the temperature and kinetics for hydrogen desorption of calcium borohydride diammoniate were effectively improved through doping transition metal chlorides (such as CoCl2, NiCl2, and FeCl3) in a closed vessel. Three additives could effectively decrease the temperature for hydrogen desorption of Ca(BH4)(2).2NH3. Among them, CoCl2-doped Ca(BH4)(2).2NH3 could desorb hydrogen even at a low temperature of 170 degrees C, and at 200 degrees C, 7.6 wt % hydrogen with high purity is released, which shows superior performance for hydrogen desorption than that of pristine Ca(BH4)(2).2NH(3.) For CoCl2-doped Ca(BH4)(2).2NH(3), X-ray absorption fine structure (XAFS) revealed that the improvements could be ascribed to the catalytic function of well-dispersed cobalt particles, which results in a much lower activation energy (86.1 kJ/mol) for hydrogen desorption of calcium borohydride diammoniate.

Mechanochemically assisted synthesis of pristine Ca(II)Sn(IV)-layered double hydroxides and their amino acid intercalated nanocomposites

Syntheses of Ca(II)Sn(IV)-layered double hydroxides (LDHs) are attempted by the traditional co-precipitation as well as mechanochemical methods. Both the co-precipitation method and the one-step milling operation proved to be unsuccessful; these methods only produced physical mixtures of hydroxides and carbonates of the two metal ions. However, a two-step milling operation (dry milling followed by milling in the presence of minute amount of water) led to successful synthesis, verified by a range of characterisation methods. Surprisingly, it was found that ball-milling was not even necessary; the reaction proceeded on manual grinding of the components in an agate mortar with a pestle. The preparation of nanocomposites through intercalation of the anions of cystine or valine into Ca(II)Sn(IV)-LDH could also be achieved by the two-step milling method verified again by a range of instrumental methods.