Papers by Keyword: Chelating Agent

Abstract: Ceramics powders based on cerate-zirconate such as yttrium-doped barium cerate-zirconate, BaCe_0.54Zr_0.36Y_0.1O₃ (BCZY) have been used as electrolyte materials for proton-conducting fuel cell (PCFC) application. High purity of the ceramics powders are traditionally prepared by solid state reaction (SSR) method at a high processing temperature (> 1400 °C). Alternatively, sol-gel (SG) technique and high pressure – high temperature (HP-HT) batch wise reactor system using supercritical fluids (SCFs) method are introduced to synthesis the powders at a lower temperature. To achieve the goals in producing the ceramics powders with better properties than SSR method, few critical parameters for both SG and SG assisted SCFs methods are determined. This study reports the effects of different chemical agents (chelating agent and surfactant) in SG method and the effects of pressure and temperature of HP-HT batch wise reactor system using ethanol as solvent on the phase purity and microstructure of the BCZY powders. Chelating agent (triethylenetetramine, TETA) and surfactant (Brij-97) aided to produce a single perovskite phase of BCZY at calcination temperatures of 1100 °C and 950 °C, respectively. On the other hand, a single perovskite phase of BCZY was obtained via SCFs assisted with sol-gel (SG-SCFs) method. The optimum characteristics of BCZY powder was found in the one prepared at P = 2 MPa and T = 150 °C and 200 °C. Particles of the powders produced by SG and SG-SCFs methods are spherical in-shape. As proven, SG method is able to produce better phase purity and homogenize BCZY powder at lower processing temperature that meets criteria to be used as an electrolyte material.

Abstract: In the present study we explore the idea of biotechnologically produced metallophore mixtures as selective chelating compounds for economically valuable metals from various sources. A complex soil matrix with natural levels of metal mineralization was employed as a potential source of metals. We focused on gallium-chelating metallophore preparations of two soil bacteria (Gordonia rubripertincta CWB2 and Paracoccus denitrificans PD1222) which were compared to the commercially available desferrioxamine B (DFOB). As a reference, the binding of iron was analyzed. The herein described successful mobilization of metals such as gallium from soil provides first hints towards alternative strategies, such as phytomining, sensor development, or solvent extraction based on metallophores. The metallophore mixture produced by the strains showed best results at pH 8 and allowed to mobilize gallium about three times better as the pure commercially available DFOB.

Abstract: Gordonia rubripertincta CWB2 produces hydroxamate-type siderophores. Therefore it was cultivated under iron limitation. Analytical reversed-phase HPLC allowed determining a single peak of ferric iron chelating compounds from culture broth. The elution profile and its absorbance spectrum were similar to those of desferrioxamine B. The latter is a commercial available metal chelating agent which is of interest for industries. We successfully developed an HPLC protocol to separate metal-free and metal-loaded desferrioxamines. Further, we aimed to increase the re-usability of desferrioxamines as metal chelators by immobilization on silica based carriers. The siderophores of strain CWB2 have been covalently linked to the carrier with a high yield (up to 95%). Metal binding studies demonstrated that metals can be bound to non-immobilized as well as to the covalently linked desferrioxamines.

Abstract: The serious quality problem in the magnetic substrate during polishing process by using conventional lapping machine had generate the idea to develop a doubled-sided lapping machine of polishing stone manufactured of an abrasive and resin. After certain parameter of polishing process, the polishing stone starts to clog because of debris agglomeration from the polishing substrate, thus lead to the scratches on the magnetic substrate which will affect its performance. Three difference type of acid were used as to dissolve the debris agglomeration in the polishing stone. The influence of oxalic, phosphoric and citric acid at three different times were examined. It was found that oxalic acid is the best chelating agent in dissolving the debris in the polishing stone.

Abstract: Lime used to treat flue gas from incinerators and organic chelating agents used to remove heavy metals from fly ash create a highly saline and alkaline environment at landfill sites, causing nitrification inhibition that hampers nitrogen treatment and generating refractory COD in the processes of organic stabilization by microbes and leachate treatment. The authors analyzed organic chelating agents and fly ash treated with the chelating agents, and monitored leachate from lysimeters, or simulated landfills. The results showed that organic chelating agents acted as nitrification inhibitors, and that higher water levels in landfill layers resulted in higher concentrations of thiourea and refractory COD, which are chelating compounds, hindering leachate treatment.

Abstract: This study aims to describe the preparation and characterization of SiO₂/TiO₂ core-shell particles. In order to prepare the homogenous SiO₂/TiO₂ inorganic compounds by sol-gel process, SiO₂ particles were used as the core, AcAc served as a chelating agent to chelate with TTIP (which was used as the precursor to TiO₂), and PEG was added to stabilize the hydrolysis/condensation process. In addition, the ionic surfactant (SDS) and the nonionic surfactant (PVP) dispersed the core-shell particles. In order to improve the crystal structure, a high temperature was used to calcine the core-shell particles. The influence of various reaction parameters on the size, morphology and composition of the particles was also investigated. The properties of the particles were analyzed by electron microscopy, fourier transform infrared analysis, thermogravimetric analysis and powder X-ray diffraction.

Abstract: Sr₄Al₁₄O₂₅:Eu²⁺, Dy³⁺ luminescent phosphor was synthesized for the first time from using cyclodextrin as chelating agent by sol-gel method. The structural characterization, surface morphology and properties of the phosphor were studied. The results revealed that the target phosphor with relatively regular morphology, smaller grain size, pure phase and high crystallinity can be achieved at 1200°C for 4 h in a reducing atmosphere. The average grain size of the Sr₄Al₁₄O₂₅:Eu²⁺, Dy³⁺ phosphor nanoparticles ranges from 50 to 100 nm . And the phosphorescence in blue-green (483 nm) by Eu²⁺.

Abstract: As a cooking additive, the impact of Diethylene Triamine Penta Methylene Phosphonic Acid (DTPMPA) on bamboo kraft pulping was studied. The effect of DTPMPA dosage at different maximum cooking temperature was discussed. The results showed that the cooking aids DTPMPA added in bamboo kraft pulping was able to reduce K value of pulp, improve the screened stock yield and brightness and reduce the alkali charge. The optimized bamboo kraft pulping conditions are: DTPMPA dosage 0.3%, alkali charge 17%, when sulfidity was 20%, maximum cooking temperature was 160°C and time at maximum temperature was 90min. Under the conditions of cooking, the screened yield is 41.53%, the K value is 15.4 and the bamboo pulp brightness is 26.8%.

Abstract: The impurities removed from the vein quartz sands were investigated with six complexing agents (citric, oxalic, acetic, humic acid, EDTA and thiourea). So as to optimized the leaching reaction parameters and to reach a high rate of impurities removal, the kinds and concentration of complexing agents, reaction temperature and time were also discussed. The results shown that the impurities can be dissolved very effectively by both oxalic acid and acetic acid, and then, the citric, humic acid, EDTA and thiourea can also be increased partly rate of impurities removal. At the same time, the interior impurities of the vein quartz sands has been dissolved out that primary depended on the mixed acids which were 2.0M HCl, 0.5M HF, and 0.8M oxalic acid complexing agent at 80°Cfor 8h. The removal rate of elements Fe, Al, K, Na, Ca, and Mg were respectively 93.31, 47.06, 17.28, 28.82, 12.58 and 62.44 percent.

Abstract: The application of chelating agents DTPMPA (Diethylene Triamine Penta Methylene Phosphonic Acid) as cooking aids in kraft pulping of bamboo was researched. The effect of DTPMPA dosage at different alkali charge was discussed. The results showed that the cooking aids DTPMPA added in bamboo kraft pulping was able to reduce K value of pulp, improve the screened stock yield and brightness and reduce the alkali charge. The optimized bamboo kraft pulping conditions are: DTPMPA dosage 0.4%, alkali charge 19%, when sulfidity was 20%, maximum cooking temperature was 165°C and time at maximum temperature was 90min. Under optimized conditions of cooking, the screened bamboo pulp yield is higher, the K value is lower and the bamboo pulp brightness is higher.