Synthesis and characterization of mesoporous gamma-alumina by glucose as soft-template for molybdenum-99 adsorption: high and low molar ratio of water to aluminium isopropoxide effect

The mesoporous gamma-alumina is a good material for metal adsorption. Its textural properties are excellent, mainly for molybdenum-99 radioisotopes adsorption as part of 99Mo/99mTc generator in nuclear medicine. In this work, we have prepared mesoporous gamma-alumina by sol-gel treatment in the presence of glucose as a soft template. The molar ratio of reactant (water: aluminium isopropoxide(AIP)) was applied in the high and low ratios (150:1 and 25:1). The resulted mesoporous gamma-alumina was investigated using characterization analysis of X-ray diffraction, Nitrogen adsorption-desorption, and FTIR. The results indicate that the mesoporous gamma-alumina in the high molar ratio of water to AIP had a higher surface area and better crystallinity than the low molar ratio of reactants. Furthermore, in the Mo adsorption test, the mesoporous gamma-alumina with the high molar ratio posed a higher Mo adsorption capacity up to 55.69 mg Mo g−1 adsorbent. In the future, the molar ratio of reactants should be tuned in the range of around 150:1 to obtain the optimal Mo adsorption capacities of the resulted mesoporous gamma-alumina using the glucose template.

Mercury and selenium concentrations in the oysters Saccostrea palmula and Crassostrea corteziensis from four coastal lagoons of NW Mexico: health risk assessment

Mercury (Hg) and selenium (Se) concentrations in the soft tissue of the oysters Saccostrea palmula and Crassostrea corteziensis from four coastal lagoons (Altata, Macapule, Navachiste, El Colorado) of Northwest Mexico were determined. A total of 2520 specimens of S. palmula and 3780 of C. corteziensis (72.15 ± 4.95 and 73.57 ± 5.31 mm, respectively) were sampled seasonally from summer 2019 to spring 2020. The higher Hg concentration (wet weight) for S. palmula (0.13 ± 0.03–0.11 ± 0.02 µg g−1) and C. corteziensis (0.12 ± 0.02–0.11 ± 0.03 µg g−1) were obtained in summer−autumn 2019; Hg level was similar among the coastal lagoons and did not exceed the limit established by Mexican legislation and by the Food and Drug Agency. The higher Se concentration occurred in spring 2020 for both oyster species in El Colorado lagoon (4.55 ± 0.02 and 4.08 ± 0.05 µg g−1, respectively). The Se/Hg molar ratio of S. palmula and C. corteziensis ranged from 48.76–149.59 and 31.72–155.37, respectively; while the Se health benefit value was 19.23–42.28 and 17.82–35.30, respectively. The hazard quotient for Hg -estimated as methylmercury- and Se in both species of oyster was below 1. The high molar ratio obtained (Se/Hg > 1) indicates that the concentration of Se was sufficient to neutralize the possible toxicity of the Hg, therefore, the consumption of S. palmula and C. corteziensis from the four coastal lagoons studied does not represent a risk.

Thermal Behavior Analysis of Melamine Modified Urea-Formaldehyde Resin with Different Molar Ratios

In this study, Thermogravimetry (TG) were used to analyze thermal degradation properties of two kinds of low-molar ratio of the melamine-modified urea-formaldehyde resin (MUF). The MUF was calculated using Kissinger equation and Flynn-Wall-Ozawa equation Resin pyrolysis activation energy. The results showed that the curing time of low mole was longer than that of MUF resin (muf-b), the content of free formaldehyde was lower, and the formaldehyde emission and wet bonding strength of plywood were reduced by 65.79% and 21.90%, respectively. TG test showed that the pyrolysis process of MUF resins with different molar ratios can be divided into three stages: dehydration, rapid pyrolysis and carbonization. At the same heating rate, the weight loss rate, peak conversion rate and carbon residue of the high molar ratio MUF resin (MUF-a) in the fast pyrolysis stage are larger than those of the MUF-b resin. The MUF-a resin pyrolysis activation energy is 166.76 kJ/mol, and the MUF-b resin pyrolysis activation energy is 95.30 kJ/mol. High molar ratio resin has higher pyrolysis activation energy and better thermal stability.

Enabling electrochemical compatibility of non-flammable phosphate electrolytes for lithium-ion batteries by tuning their molar ratios of salt to solvent

A stable phosphate electrolyte with a high molar ratio (1 : 2) but a low molar concentration (1.35 M) is developed.

Modification of Pea Starch and Dextrin Polymers with Isocyanate Functional Groups

Pea starch and dextrin polymers were modified through the unequal reactivity of isocyanate groups in isophorone diisocyanate (IPDI) monomer. The presence of both urethane and isocyanate functionalities in starch and dextrin after modification were confirmed by Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (13C NMR). The degree of substitution (DS) was calculated using elemental analysis data and showed higher DS values in modified dextrin than modified starch. The onsets of thermal degradation and temperatures at maximum mass losses were improved after modification of both starch and dextrin polymers compared to unmodified ones. Glass transition temperatures (Tg) of modified starch and dextrin were lower than unmodified control ones, and this was more pronounced in modified dextrin at a high molar ratio. Dynamic water vapor sorption of starch and dextrin polymers indicated a slight reduction in moisture sorption of modified starch, but considerably lower moisture sorption in modified dextrin as compared to that of unmodified ones.

Hydrothermal synthesis of lithium-enriched β-Li2TiO3 with an ion-sieve application: excellent lithium adsorption

Lithium-enriched monoclinic lithium metatitanate (β-Li2TiO3) with a high molar ratio of Li to Ti (2.11) was synthesized by a hydrothermal method.

Systematic Precipitation of Magnesium Hydroxide Using NH4OH to Preparing MgO-PSZ Precursor Powder

The wide range of applications of zirconia based ceramics is due to stabilization of its tetragonal and cubic structures at room temperature, by controlled adding of dopants such as yttria, magnesia, calcia, ceria and some rare earth oxides. The advantage of the use of magnesia as dopant is not only due to its low cost, but fact that by controlling its ceramic processing, it is possible to control a specific microstructure for the specific application. The precipitation of magnesium hydroxides, using NH4OH as a precipitant, presents some difficulties due to the formation of a variety of soluble complexes of ammonia with magnesium, which inhibits the total precipitation of magnesium. In the present work, the influence of precipitant and metals concentrations and pH on the magnesium hydroxide precipitation was investigated. Magnesium chloride, zirconium oxychloride and NH4OH were used as starting materials. The precipitation of magnesium hydroxide depends on concentrations of OH-, Cl- and Mg2+. To achieve specific precipitation yield, lower the concentration of Mg2+ high molar ratio of [OH-]/[Cl-] is required. The pH measure is not enough to control Mg (OH)2 precipitation. The use of molar ratio of [OH-]/[Cl-] = 4.4, resulted in 95 % of Mg (OH)2 precipitation. The co-precipitation of Zr and Mg hydroxides, using the optimized molar ratio of [OH-]/[Cl-], the precipitation of Mg (OH)2 achieved in range of 97.6 to 98.3 %.

One-Step Nonaqueous Synthesis of Pure Phase TiO2Nanocrystals from TiCl4in Butanol and Their Photocatalytic Properties

Pure phase TiO2nanomaterials were synthesized by an autoclaving treatment of TiCl4with butanol as a single alcohol source. It was found that the control of molar ratio of TiCl4to butanol played an important role in determining the TiO2crystal phase and morphology. A high molar ratio of TiCl4to butanol favored the formation of anatase nanoparticles, whereas rutile nanorods were selectively obtained at a low molar ratio of TiCl4to butanol. Evaluation of the photocatalytic activity of the synthesized TiO2was performed in terms of decomposition of organic dye rhodamine B under ultraviolet irradiation. It turned out that the as-synthesized TiO2crystallites possessed higher photocatalytic activities toward bleaching rhodamine B than Degussa P25, benefiting from theirhigh surface area, small crystal size as well as high crystallinity.

Preparation and Properties of Low Formaldehyde Emission Plywood with Flame Resistance

In order to improve the flame resistance and reduce the formaldehyde emission of plywood, a multifunctional formaldehyde scavenger with flame resistance (FSFR) was prepared and used to treat plywoods bonded with high molar ratio urea-formaldehyde (UF) resin. The weight percent gain (WPG), formaldehyde emission, oxygen index (OI), and bonding strength of plywoods after FSFR treated were measured to evaluated properties of FSFR. The results showed that the formaldehyde emission of the treated plywood was 0.1-0.32 mg/L, which could meet the E0 grade requirement (<0.5 mg/L ). The flame resistance of treated plywood increased significantly and the bonding strength changed little. The formaldehyde emission decreased 96.8 % and OI increased 47.2 % and the bonding strength kept unchanged when FSFR reached 8.87 % compared with that of untreated plywood.