Molar Ratio Of Mg Research Articles

Pinning properties of Ag/MgB 2 bulk system

Bulk MgB 2 containing nano-particles of Ag–Mg alloys were sintered from the mixtures of Mg-, B- and Ag 2O-powder with the mole ratio of Mg:B:Ag 2O = 1.6 (1− x):2(1− x): x/2, where x was the nominal concentration of Ag from 0 to 0.1. The solid reaction of the powder mixture was performed in the electric furnace at 900 °C for 30 min under Ar-atmosphere with 10% H 2 gas. The X-ray diffraction patterns and images of transmission electron microscope showed the production of Ag–Mg nano-particles in bulk MgB 2, except for MgO impurity. For x = 0.01 and 0.02 samples, the enhancement of J c was observed without T c reduction, which means the efficiency of the nano-particles of Ag–Mg as the pinning centers in MgB 2.

Mg(OH)Cl/KI as a Highly Active Heterogeneous Catalyst for the Synthesis of Cyclic Carbonates from CO2 and Epoxides under Solvent‐Free Conditions

AbstractThe combination of magnesium hydroxyl chloride [Mg(OH)Cl] with KI could efficiently catalyze the coupling reaction of carbon dioxide with epoxides to give the corresponding cyclic carbonates in good to excellent yields (75.0% –98.3%) and high selectivity (99.6%) in the absence of organic solvents. The heterogeneous catalyst Mg(OH)Cl/KI could be reused at least six times almost without loss of the catalytic activity. The influence of some key factors (such as molar ratio of Mg(OH)Cl to KI, temperature, reaction time and CO2 pressure) on the reaction was also discussed.

Waste elimination processes of iron oxide red

AbstractA new process of mixing acid iron oxide red was studied. The process uses an inoculating seed of sulfuric acid method after purification and enrichment, followed by addition of ferrous nitrate in a two‐step oxidization. The benefits of the new process were good quality, safe operation, and less pollution. The wastewater treatment of the highly concentrated ammonium‐nitrogen of iron oxide red production was also studied. The method of chemical precipitation, which uses MgSO4 and Na2HPO4 to form guano, was applied. It was defined that the optimal conditions are as follows: the pH was about 10, and the mole ratio of Mg:N:P was 1.1:1.0:1.3. In the wastewater of iron oxide red production, the concentrated ammonium‐nitrogen was reduced from 417.5 to 1.9 mg/L, and the removal efficiency was up to 99.5%. At the same time, MgNH4PO4·6H2O can be used as compound‐fertilizer. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

Mg-C 系合金の創製とその水素親和性

Magnesium based alloys possess light-weight and high hydrogen absorption capacity so that they have been investigated extensively for several decades. Great attention also has recently been paid to graphite as a hydrogen absorber. In this study Mg-C alloys were prepared by ball milling and their hydrogenation properties were investigated. Powders were first mixed with a 1 : 1 molar ratio of Mg to graphite. Milling balls and a pot were made of SUS304. This process was performed with a vibration ball mill at the speed of 11.8 Hz under an Ar gas atmosphere for 60 hours. The prepared powders were handled in a glove box filled with an Ar gas. After ball milling, samples showed a new X-ray diffraction peak, which was either not a peak from Mg and/or graphite. An affinity for the powders with hydrogen was confirmed at 453 K and the 1.8 MPa hydrogen pressure. The total amount of absorbed hydrogen was estimated to be 2.0 wt% from the thermal desorption spectroscopy (TDS) spectrum.

Urea hydrolysis and recovery of nitrogen and phosphorous as MAP from stale human urine

Laboratory-scale tests for magnesium ammonium phosphate (MAP) precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design. The effects of initial pH, temperature and the volumetric ratios of stale urine to fresh urine, on urea hydrolysis in urine were studied to determine the final hydrolysis time to recover most nitrogen from separated human urine by MAP. With a volumetric ratio of stale to fresh urine > 10% and at temperature > or = 20 degrees C, urea hydrolysis could be completed in two days. Alkaline pH inhibited urea hydrolysis progress. The final pH values were all around 9.0 following urine hydrolysis, while the suspension pH might act as an indicator to detect the start and extent of urea hydrolysis. Over 95% of ammonium nitrogen and over 85% of phosphorus from hydrolyzed urine as MAP precipitate were obtained using MgCl2.6H2O and Na2HPO4 x 12H2O as precipitation agents at pH 8.5, molar ratio of Mg2+:NH4(+)-N:PO4(3-)-P at (1.2-1.3):1:1, mixing speed of 120 r/min, and precipitation time and reaction time of 3 h and 15 min, respectively. The precipitate has a structure resembling pure MAP crystal.

Recovery of ammonia nitrogen from industrial wastewater treatment as struvite slow releasing fertilizer

Struvite, magnesium ammonium phosphate hexahydrated (MAP) (Mg NH 4 PO 4.6H 2O) is a white inorganic crystalline mineral that can be used as a slow releasing fertilizer. The present study evaluated the feasibility of using bittern as a by-product of salt manufacture, as a low-cost source of magnesium ions, to recover the ammonia from industrial wastewater. A lab-scale study was performed to investigate the efficiency of (MAP) precipitation using bittern at different pH s from 7–11 at two different molar ratios of Mg:NH 4:PO 4 (1:1:1) and (1.6:0.6:1) on synthetic struvite in distilled water. The optimum pH, settling time and solid/liquid ratio have been studied. Application of liquid bittern to industrial wastewater treatment for ammonia removal was confirmed by XRD-spectra difractograms of precipitate collected after bittern addition with final pH = 9.6 was compared to synthetic standard struvite.

Synthesis and phosphate uptake behavior of Zr 4+ incorporated MgAl-layered double hydroxides

We synthesized Zr 4+ incorporated MgAl-layered double hydroxides, Mg(AlZr)-LDH(A) (where A denotes a counteranion in the interlayer space and is expressed as CO 3 for carbonate and Cl for chloride ions), with different molar ratios of Mg/(Al + Zr). Then we characterized their uptake behavior toward phosphate ions. CO 3-type tertiary LDH materials synthesized at room temperature show low crystallinity, whereas the highly crystalline Cl-type tertiary LDH, [Mg 0.68Al 0.17Zr 0.14(OH) 2][Cl 0.26⋅(CO 3) 0.04⋅1.24H 2O], was synthesized for the first time using a hydrothermal treatment at 120 °C. The distribution coefficients ( K d ) of oxo-anions were measured with a mixed solution containing trace amounts of the anions. The selectivity sequences were Cl −, NO − 3 < SO 2− 4 ≪ HPO 2− 4 for CO 3-type materials and SO 2− 4 < HPO 2− 4 <NO − 3 for the crystalline Cl-type material. The uptake of phosphate ions from model wastewater (2.0 mg-P/dm 3) and phosphate-enriched natural seawater (0.33 mg-P/dm 3) was investigated in detail. The CO 3-type materials have higher phosphate uptakes than the Cl-type materials. The maximum phosphate uptake of the CO 3-type material with a molar ratio of Mg/(Al + Zr) of 3 is 30 mg-P/g at pH 8.7 with the wastewater, and 16 mg-P/g at pH 8.1 with the seawater, in contrast to the case of the usual binary MgAl-LDH(CO 3): 10 mg-P/g with the wastewater and less than 1 mg-P/g with the seawater. The large uptake and high selectivity of the CO 3-type tertiary LDH materials is well explained by complex formation of phosphate ions directly with Zr(IV) centers in the layers.

Improvement of the hydrogen-storage performances of Li–Mg–N–H system

Li2MgN2H2 can reversibly store more than 5.5 wt% hydrogen. However, the high activation energy of hydrogen desorption poses a kinetic barrier for low-temperature operation. In this work, the composition of the Li–Mg–N–H system has been modified by the partial substitution of Mg or Li by Na. The changes in structure and hydrogen absorption/desorption kinetics have been investigated. It was found that the peak temperature for hydrogen desorption was decreased by ∼10 °C, and that the hydrogen absorption/desorption isotherms were also significantly changed. Furthermore, the activation energy calculated by the Kissinger’s approach was reduced after the substitution of Mg or Li by Na. In addition, the different dehydrogenation structures were detected at different molar ratios of Mg, Li, and Na.

Phase Behavior of Aqueous Suspensions of Mg2Al Layered Double Hydroxide: The Competition among Nematic Ordering, Sedimentation, and Gelation

Birefringence observations and rheological measurements were used to monitor the phase behavior of Mg/Al (the molar ratio of Mg(2+) to Al(3+) being 2:1) layered double hydroxide (LDH) suspensions. The suspensions of concentration lower than 16% (w/w) appear isotropic (I) between crossed polarizers. In contrast, the suspensions of concentration between 16% and 30% (w/w) showed an isotropic (I)-nematic (N) biphasic coexistence. Detailed observations led us to divide the suspensions in the gap into three groups according to their behaviors: the suspensions with concentration between 16% and 25% (w/w) experienced an I-N phase transition and particle sedimentation simultaneously, while the suspensions of 25% to 27% (w/w) showed I-N transition after particle sedimentation, and in the suspension of 30% (w/w), a critical sol-gel transition appeared with an I-N transition. Above 33% (w/w), the gel network hindered a complete I-N separation in the suspensions. Upon raising the NaCl concentration, the liquid crystalline phase transition and the sol-gel transition shifted to higher particle concentrations. The facts demonstrate that the phase behavior of aqueous LDH suspensions is controlled by the competition among liquid crystal phase transition, sedimentation, and gelation.

Comparison between Biological Treatment and Chemical Precipitation for Nitrogen Removal from Old Landfill Leachate

The study reports the results of a laboratory scale investigation aimed at evaluating the effectiveness of mature municipal landfill leachate treatment by a biological stage (used SBBR as a biological treatment) and Chemical precipitation (Used MAP precipitation (magnesium ammonium phosphate)) to study the nitrogen removal capabilities for treatment of sanitary landfill leachate containing high ammonia concentration, and the comparison between them. The monitored sample taken from the Chang Sheng bridge landfill site in Chongqing city-China, has its concentrations of COD, BOD5, and NH3-N about 1650, 75 and 1100 mg/l respectively. The results from SBBR showed that after two months long period of domestication and one month period of stability, the ammonia nitrogen removal efficiency reached to 99% in the SBBR reactor, at nitrogen loading rate 0.51 kg TN/m3 per day and HRT was 9 hours, met to Chinese standards for discharge. The results of the MAP precipitation was technically effective to remove the high NH3-N strength of over 1100 mg/l from the raw leachate at molar ratio of Mg2+: NH4+: PO4-3 of 1:1:1, they demonstrated a very satisfactory removal of ammonia; an initial NH3+-N concentration of 1100 mg/l contained in the raw leachate was quickly reduced to 28 mg/l within 15 min, while the pH producing a maximum removal of ammonia was 9.0. The percent removal of ammonia after treatment by MAP was 97.5%.

Boron Removal via Formation of Magnesium Silicate Solids during Precipitative Softening

Precipitative softening is an option to remove silicon and boron from natural waters. Silicon was removed from hard waters by precipitative softening when the molar ratio of Mg:Si was less than 6:1 by the formation of an amorphous magnesium silicate. This solid had an apparent solubility product constant of 10 -25.66 and was stoichiometrically similar to the mineral forsterite, Mg 2 SiO 4 . Boron removal was consistent with sorption to this amorphous magnesium silicate and could be roughly described by a Freundlich isotherm: B sorb /Mg 2 SiO 4(s) =21×B 0.51 sol .

Mg-C 複合材料の創製とその水素吸蔵特性

Mg-based alloys possess light-weight and high hydrogen absorption capacity, so they have been investigated extensively for several decades. Also, attention has recently been paid to graphite as a hydrogen absorber. In this study Mg-C composites were prepared by ball milling and their hydrogenation properties were investigated. Powders were first mixed with a 1:1 molar ratio of Mg (99.9% purity) to graphite (99.9% purity), and then milled using ZrO2 balls in a ZrO2 pot for 60 hours. This process was performed in a vibration ball mill at the speed of 345 rpm under an Ar gas atmosphere. The powders prepared in this way were handled in a glove box filled with an Ar gas. From the XRD patterns, it was found that the peak corresponding to the Mg phase shifted slightly to lower diffraction angles, indicating that the lattice spacing of the Mg phase was expanded by alloying partially with C in the powders. On the other hand, graphite peaks were rather broadened. An affinity for the powders with hydrogen was confirmed from the absorption experiment at the temperature of 453 K and the hydrogen pressure of 1.8 MPa. The total amount of absorbed hydrogen was estimated to be 3.5 mass% from the TDS measurement.

The role of Mg 2+ and Mg 2+/amino acid in controlling polymorph and morphology of calcium carbonate crystal

Mg 2+ and the mixture of Mg 2+/ dl-aspartic or l-tyrosine were used as effective crystal nucleation and growth modifiers to control the crystallization of CaCO 3. The polymorph and morphology of crystals were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The results demonstrated that various morphologies such as rod-shaped particles, spinose sphere particles, cauliflower-like crystals, and the spindly particles produced in above aqueous solutions. When the molar ratio of Mg 2+ to Ca 2+ was less than 8, the products were all the mixtures of calcite and aragonite. The ability of Mg 2+ to induce the formation of aragonite was enhanced as the molar ratio of Mg 2+ to Ca 2+ increased. When the molar ratio reached 8, the crystals obtained were all aragonite. In the mixed systems of Mg 2+/amino acids, the presence of amino acids was helpful for the formation of aragonite. The possible formation mechanisms of CaCO 3 in different systems were discussed in the paper.

La-doping effects on pinning properties of MgB 2

The La-doped MgB 2 samples were sintered from the mixture of Mg, B and La powder with the mole ratio of Mg:B:La=1.2:2(1+3 x): x, where x was 0, 0.01 and 0.02. The solid reaction of the powder mixture was performed in the microreactor at 1023 K under Ar-atmosphere of 40 MPa. For the prepared samples, the X-ray diffraction results showed the production of impurity phase of LaB 6 nano-particles within the bulk MgB 2 except for small amount of MgO. The slight reduction of T c's and the decreasing of decay rates of J c against the magnetic field could be characterized for x=0.01 sample.

High Pressure Synthesis of Novel Compounds in Mg-TM Systems (TM = Ti&amp;sim;Zn)

High pressure synthesis under 6 GPa using a cubic-anvil-type apparatus were applied to investigation of new compounds in Mg-TM systems. The crystal structure, thermal stability and reactivity with hydrogen for the newly synthesized compounds were studied. The Mg4Ni compound belonging to space group Fm with a lattice parameter of a ¼ 1:9987ð1Þ nm was synthesized as a new compound at 1173 K for 8 h under 6 GPa. It decomposed to Mg and Mg2Ni phase at 545 K as exothermic reaction. In Mg-Cu systems, two unreported phases were synthesized at 1073 K for 8 h under 6 GPa. The one is the MgCu compound which has CsCl-type structure with a lattice parameter of a ¼ 0:31616ð7Þ nm and the other is Mg51Cu20 belonging to space group Immm with a lattice parameter of a ¼ 1:3929ð7Þ nm, b ¼ 1:428ð1Þ nm and c ¼ 1:392ð1Þ nm. The MgCu compound decomposed to Mg2Cu and MgCu2 phases at 500 K and the Mg51Cu20 compound did to Mg and Mg2Cu phase at 430 K. Raw materials such as Mg (purity 99.9 mass%), Ti (purity 99 mass%), V (purity 99.5 mass%), Cr (purity 99.9 mass%), Mn (purity 99.9 mass%), Fe (purity 99 mass%), Co (purity 99 mass%), Ni (purity 99.8 mass%), Cu (purity 99.9 mass%), Zn (purity 99.9 mass%) powders are mixed with a molar ratio of Mg:TM = 1:1. They were pressed into pellets in a glove box filled with pure Ar. Especially, in the Mg-Ni and Mg-Cu systems, the Mg-20 at%Ni and Mg-20 at%Cu samples were also prepared since the Mg2Ni and Mg2Cu phases exist in Mg-rich composition in these systems, respectively. The pellets of samples were put into BN containers. Then, the container was set into a graphite tube heater, and placed into a pressure media made from pyrophyllite shown in Fig. 1. The high-pressure synthesis was carried out in a cubic- anvil-type apparatus. Samples were prepared at 673-1223 K

Optimization of phosphorus precipitation from swine manure slurries to enhance recovery

Laboratory experiments were conducted using magnesium chloride (MgCl2 x 6H2O, 64% solution) to force the precipitation of phosphorus and reduce the concentration of soluble phosphorus (PO4(3-)) in two swine wastes. One of the swine wastes tested contained a high concentration of PO4(3-) (initially approximately 1,000 mg/L), and the other swine waste tested contained a low concentration of PO4(3-) (initially approximately 230 mg/L). The precipitation reactions were performed to determine the required reaction time, pH, magnesium addition rate and seed material for future precipitate recovery work. For the high and low concentration waste, a 10-minute reaction time at a pH of 8.6 was sufficient to remove 98 and 96% of the PO4(3-) from solution. A molar ratio of Mg2+:PO4(3-) of 1.6:1 was determined to be effective for PO4(3-) removal from both the low and high strength wastes. At a molar ratio of 1.6:1, the PO3- in the high concentration waste was reduced from 590 to 12 mg/L. In the low concentration waste, the PO4(3-) concentration was reduced from 157 to 15 mg/L. Seeding the reaction did not significantly enhance the recovery process.

Recovery of ammonium-nitrogen from landfill leachate as a multi-nutrient fertilizer

Leachates generated in Hong Kong landfill sites contain high strength of ammonium-nitrogen (NH 4 +-N) in the range of 2000–5000 mg l −1, which could be used to produce nitrogen-fertilizer. To recover the NH 4 +-N from the leachate, a lab-scale study was performed to investigate the efficiency of magnesium ammonium phosphate (MAP) precipitation using three combinations of chemicals: MgCl 2·6H 2O+Na 2HPO 4·12H 2O, MgO+85% H 3PO 4 and MgSO 4·7H 2O+Ca(H 2PO 4)·H 2O. The results indicated that the NH 4 +-N was recovered by 92, 36 and 70%, respectively, using the selected chemicals at pH 9.0 and a molar ratio of Mg:N:P=1:1:1. The MAP precipitate (MgNH 4PO 4·6H 2O) as struvite was examined by scanning electron microscopy and the results showed that the MAP precipitate had a typical morphology of elongated tubular and short prismatic crystals. The MAP precipitate was also analyzed by energy dispersive spectroscopy and the analytical results indicated its composition of 4.9% N, 8.6% Mg and 16% P, which was similar to the standard struvite composition of 5.7% N, 9.9% Mg and 12.6% P. To investigate the fertility of the MAP precipitate, a set of pot trial tests was conducted. Four quick-growth vegetables, Chinese flowering cabbage ( Brassica parachinensis), Chinese chard ( Brassica rapa var. chinensis), water spinach ( Ipomoea aquatica) and water convolvulus ( Ipomea aquatica, I. reptans), were planted in sandy clay (Red Earth) and the MAP precipitate was applied as a fertilizer. The germination and growth of the selected vegetables in the pots with MAP showed significantly greater rates than those in the pots without MAP as control tests. The experiment also demonstrated that over-dosing of about 2–8 times of MAP in the soil did not cause any problems with water spinach ( Ipomoea aquatica) growth, due to its limited solubility in water. MAP application as a fertilizer did not result in more heavy metals in the vegetables than those from soil and model fertilizer, whereas the higher levels of P and Mg in the vegetables would stimulate vegetables’ growth. This study confirmed the feasibility of recovering NH 4 +-N from landfill leachate effectively by chemical precipitation, and also the feasibility of applying the MAP precipitate as a multi-nutrient fertilizer for vegetable growth.

New method of treating dilute mineral acids using magnesium–aluminum oxide

Mineral acids, such as H 3PO 4, H 2SO 4, HCl, and HNO 3, were treated with magnesium–aluminum oxide (Mg–Al oxide), which behaved as a neutralizer and fixative of anions. Anion removal increased with increasing Mg–Al oxide quantity, time, Mg/Al molar ratio, and initial acid concentration. Up to 95% removal of anions was achieved in 0.5 N acids using a stoichiometric quantity of Mg 0.80Al 0.20O 1.10 for H 3PO 4, 1.75 stoichiometric quantities for H 2SO 4, or 2.5 stoichiometric quantities for HCl or HNO 3 at 20°C over a period of 6 h. The final solutions were found to have a pH in the range of 8–12. Selectivity of acid removal was found to follow the following order: H 3PO 4>H 2SO 4>HCl>HNO 3. The equivalent of acid removal per 1 g of Mg–Al oxide decreased as the Mg/Al molar ratio of Mg–Al oxide increased.

MAP Precipitation from Landfill Leachate and Seawater Bittern Waste

The leachates generated at Hong Kong landfill sites contain high strength of ammonium-nitrogen (NH4 +-N) over 3,000 mg l−1 and are generally inhibitive to most biological treatment processes. To remove the NH4 +-N from the landfill leachates and also recover the nitrogen as a struvite fertilizer, a lab-scale study was performed to investigate the feasibility of NH4 +-N removal and struvite crystallization using different magnesium sources. Three combinations of chemicals, MgCl2·6H2O+Na2HPO4·12H2O, MgO+H3PO4 and MgSO4·7H2O+Ca(H2PO4)·H2O, were first used at different molar ratios to precipitate NH4 +-N from the leachate. The experimental results indicated that NH4 +-N was removed by 92%, 36% and 70% respectively at pH 9.0 and a molar ratio of Mg:N:P−=1:1:1. Two synthetic seawater bittern wastes containing Mg2+ at 9,220 mg l−1 and 24,900 mg l−1 respectively were then used as a magnesium source, while 85% H3PO4 chemical was used as a phosphorus source. The results revealed that NH4 +-N was removed by 80% and 72% respectively, while a molar ratio of Mg:N:P=1:1:1 was applied. In the final stage of experiments, the magnesium-ammonium-phosphate (MAP) precipitates were examined by SEM, EDS and XRD. The SEM micrographs of the MAP precipitates showed a typical morphology of elongated tubular and short prismatic crystals. The EDS and XRD results indicated that the chemical composition of the MAP precipitates depended on the chemicals used and experimental conditions. The study confirmed that the recovery of NH4 +-N from landfill leachate and seawater bittern wastes could be effectively achieved by MAP precipitation to obtain struvite crystals with a composition of 5.1%N, 10.3%Mg and 16.5%P.

Synthesis of Star-Shaped Poly(ε-caprolactone)-b-poly(dl-lactic acid-alt-glycolic acid) with Multifunctional Initiator and Stannous Octoate Catalyst

Two types of three-arm or four-arm star-shaped hydroxy-terminated poly(ε-caprolactone) (PCL) were successfully synthesized via the ring-opening polymerization of ε-caprolactone (CL) with multifunctional initiator, such as trimethylolpropane (TMP) or pentaerythritol (PTOL), and stannous octoate (SnOct2) catalyst in bulk at 110 °C. The number-average molecular weight of PCL is proportional to the molar ratio of monomer to initiator. 1H NMR spectroscopy of the resulting PCL indicates that it contains a primary hydroxy end group in each arm. The star-shaped PCL with hydroxy end groups can be used as a macroinitiator for block copolymerization with dl-3-methylglycolide (MG) using SnOct2 catalyst in bulk at 115 °C. 1H NMR spectra of the resulting block copolymers show that the molecular weights and the unit compositions of the block copolymers were controlled by the molar ratios of MG monomer to hydroxy groups of PCL and MG to CL in feed, respectively. Moreover, the molecular weights of the resulting block copolymers linearly increased with the increase of the molar ratios of MG to CL in feed. The molecular weight distributions of the block copolymers were rather narrow (Mw/Mn = 1.09−1.26). 13C NMR spectra of the resulting block copolymers clearly show their diblock structures, that is, PCL as the first block and poly(dl-lactic acid-alt-glycolic acid) (dl-PLGA50) with alternating structures of lactyl and glycolyl units as the second block. Therefore, two types of three-arm or four-arm star-shaped diblock copolyesters comprising the first block PCL and the second block dl-PLGA50 were successfully synthesized via the sequential ring-opening polymerization of CL with multifunctional initiator and SnOct2 catalyst and then followed by copolymerization with MG.