scholarly journals Thermodynamic calculation of the effect of polymorphism and pH value on the solubility of aluminium oxide and its hydrates in aqueous media

2020 ◽  
Author(s):  
Е.В. Школьников ◽  
Д.П. Еловиков
Keyword(s):  
Ph Value ◽  
Solid Phase ◽  
Pure Water ◽  
Aqueous Media ◽  
Molar Fraction ◽  
Equilibrium Solubility ◽  
Aluminum Oxides ◽  
Aluminum Hydroxides ◽  
Naoh Solution ◽  
Α Al2o3

Экспериментальное определение истинной равновесной растворимости гидроксидов и оксидов алюминия затруднено характерной склонностью их к образованию золей, а также из-за медленного установления гетерогенного химического равновесия и низкой величины растворимости в водных средах [Школьников, 2008, 2009]. В статье на основе результатов тщательного медленного кондуктометрического и потенциометрического титрования 0,0010 М раствора Al(NO3)3(pH0 = 3,00) раствором 0,050 (0,100) М NaOH при 20 °С определен cостав устойчивых гидроксокомплексов Al(ОН)n где n = 1, 2, 3, 4. Выполнен критический анализ информации о термодинамических свойствах оксидов, гидроксидов и гидроксокомплексов алюминия. Теоретически рассчитано влияние pH в интервале 3–14 на равновесные молярные доли катиона Al3+ и его моноядерных гидроксокомплексов и на равновесную растворимость различных модификаций оксида алюминия и его гидратов при 25 °С. Для большинства модификаций Al2O3 расчет проведен впервые. Экспериментально определенная растворимость твердой фазы Al(OH)3 [Gayer, Thompson, Zajice,1958] близка в слабокислой среде к рассчитанной авторами растворимости нордстрандита β-Al(OH)3, а в щелочной среде – байерита α-Al(OH)3. Растворимость оксидов и гидроксидов алюминия в чистой воде определяется содержанием растворенных нейтральных комплексов Al(OH)3 (молярная доля ~ 0,93) и зависит от структуры, уменьшаясь на три порядка при переходе от аморфных к термодинамически стабильным модификациям α–Al2O3, α–AlO(OH) и γ – Al(OH)3. Рассчитаны минимальная молярная растворимость (от 2·10–8 для α-AlO(OH) до 4·10–3 моль/л для аморфного Al2O3) и оптимальная величина pH (7,15) наиболее полного осаждения оксидов и гидроксидов алюминия в водных средах при 25 °С. Experimental determination of the true equilibrium solubility of aluminum hydroxides and oxides is complicated by their characteristic tendency to form sols, as well as due to the slow establishment of heterogeneous chemical equilibrium and low solubility in aqueous media [Shkol`nikov, 2008 and 2009]. In the article, based on the results of careful slow conductometric and potentiometric titration of 0.0010 M Al(NO3)3 solution (pH0 = 3.00) with solution 0.050 (0.100)M NaOH solution at 20 °C, the composition of stable hydroxocomplexes Al(OH)n where n = 1,2,3,4 is determined. The critical analysis of information about the thermodynamic properties of aluminum oxides, hydroxides, and hydroxocomplexes is performed. The effect of pH in the range 3-14 on the equilibrium molar fractions of the Al3+ cation and its mononuclear hydroxocomplexes and on the equilibrium solubility of various modifications of aluminum oxide and its hydrates at 25 °C was theoretically calculated. For most Al2O3 modifications the calculation was performed for the first time. The experimentally determined solubility of the solid phase Al(OH)3 [Gayer, Thompson, Zajice, 1958] is close in a slightly acidic medium to the calculated solubility of nordstrandite β-Al(OH)3, and in an alkaline medium – bayerite α-Al(OH)3. The solubility of aluminum oxides and hydroxides in pure water is determined by the content of dissolved neutral Al(OH)3 complexes (molar fraction ~ 0.93) and depends on the structure, decreasing by three orders of magnitude during the transition from amorphous to thermodynamically stable modifications of α-Al2O3, α-AlO(OH) and γ-Al(OH)3. The minimum molar solubility (from 2·10–8 for α-AlO(OH) to 4·10–3 mol/l for amorphous Al2O3) and the optimal pH(7.15) for the most complete deposition of aluminum oxides and hydroxides were calculated in aqueous media at 25 °C.

scholarly journals Struvite as a Non-Equilibrium Solid Phase in Electrolytic Systems (Aqueous Media)

2020 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Computer Program ◽  
Solid Phase ◽  
Pure Water ◽  
Aqueous Media ◽  
Renal Calculi ◽  
Dissolution Process ◽  
Solid Phases ◽  
Equilibrium Solid Phase ◽  
Non Equilibrium

Struvite (MgNH4 PO4 •6H2 O) is not the equilibrium solid phase when introduced into pure water or into an aqueous CO2 solution, with or without KOH added as the pH-modifying component. In some instances, the dissolution process consists of several steps where different solid phases are formed. It results from a simulating procedure, where the entire physicochemical knowledge on the system in question is involved in the iterative computer program. The results of calculations are put in context with formation of struvite renal calculi in urinary tracts.

scholarly journals CHEMICAL CLEANING OF MICROFILTRATION CERAMIC MEMBRANE FOULED BY NOM

2018 ◽  
Vol 80 (6) ◽  
Author(s):  
Maisarah Mohamed Bazin ◽  
Yuzo Nakamura ◽  
Norhayati Ahmad
Keyword(s):  
Ceramic Membrane ◽  
Sintering Temperature ◽  
Ph Value ◽  
Pure Water ◽  
Water Flux ◽  
Chemical Cleaning ◽  
Naoh Solution ◽  
Membrane Porosity ◽  
Pure Water Flux ◽  
Ball Clay

Microfiltration membrane made from Sayong ball clay by using uniaxial dry compaction method was used to treat natural organic matter (NOM) source water. A sintering temperature of 900 °C to 1000 °C were applied. The effect of sintering temperature on membrane porosity, strength and water flux were identified. The porosity of the membrane decreased with increasing sintering temperature and the strength and flux increased with temperature. The membrane was subjected to NOM filtration experiments. The results showed an improvement to the quality of permeate water, where there is a reduction in COD, TSS, BOD5, turbidity, hardness and salinity; and an increased pH value. The effect of chemical cleaning on the fouled membrane also was studied. After cleaning with NaOH solution, a high flux recovery was achieved (up to 50% from the initial pure water flux). The degree of cleanliness of fouled membranes after chemical cleaning was further observed with SEM and EDX analysis.

scholarly journals Separation of Radionuclides from a Rare Earth-Containing Solution by Zeolite Adsorption

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 20
Author(s):  
Deniz Talan ◽  
Qingqing Huang
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Contact Time ◽  
Separation Efficiency ◽  
Ph Value ◽  
Solid Phase ◽  
Separation Performance ◽  
Solution Ph ◽  
Zeolite Sample ◽  
Alternative Sources

The increasing industrial demand for rare earths requires new or alternative sources to be found. Within this context, there have been studies validating the technical feasibility of coal and coal byproducts as alternative sources for rare earth elements. Nonetheless, radioactive materials, such as thorium and uranium, are frequently seen in the rare earths’ mineralization, and causes environmental and health concerns. Consequently, there exists an urgent need to remove these radionuclides in order to produce high purity rare earths to diversify the supply chain, as well as maintain an environmentally-favorable extraction process for the surroundings. In this study, an experimental design was generated to examine the effect of zeolite particle size, feed solution pH, zeolite amount, and contact time of solid and aqueous phases on the removal of thorium and uranium from the solution. The best separation performance was achieved using 2.50 g of 12-µm zeolite sample at a pH value of 3 with a contact time of 2 h. Under these conditions, the adsorption recovery of rare earths, thorium, and uranium into the solid phase was found to be 20.43 wt%, 99.20 wt%, and 89.60 wt%, respectively. The Freundlich adsorption isotherm was determined to be the best-fit model, and the adsorption mechanism of rare earths and thorium was identified as multilayer physisorption. Further, the separation efficiency was assessed using the response surface methodology based on the development of a statistically significant model.

Experimental and Numerical Study of Methanol-Water Mixture Single-Phase Heat Transfer in a Micro-Channel Heat Sink

2012 ◽  
Author(s):  
Chun K. Kwok ◽  
Matthew M. Asada ◽  
Jonathan R. Mita ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Single Phase ◽  
Numerical Study ◽  
Pure Water ◽  
Molar Fraction ◽  
Water Mixture ◽  
Micro Channel ◽  
Numerical Predictions

This paper presents an experimental study of single-phase heat transfer characteristics of binary methanol-water mixtures in a micro-channel heat sink containing an array of 22 microchannels with 240μm × 630μm cross-section. Pure water, pure methanol, and five methanol-water mixtures with methanol molar fraction of 16%, 36%, 50%, 63% and 82% were tested. Key parametric trends were identified and discussed. The experimental study was complemented by a three-dimensional numerical simulation. Numerical predictions and experimental data are in good agreement with a mean absolute error (MAE) of 0.87%.

TPPS supported on core–shell PMMA nanoparticles: the development of continuous-flow membrane-mediated electrocoagulation as a photocatalyst processing method in aqueous media

2015 ◽  
Vol 17 (3) ◽  
pp. 1907-1917 ◽  
Author(s):  
Paolo Dambruoso ◽  
Marco Ballestri ◽  
Claudia Ferroni ◽  
Andrea Guerrini ◽  
Giovanna Sotgiu ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Pure Water ◽  
Aqueous Media ◽  
Processing Method ◽  
Core Shell

Photons and electrons cooperate for effective, clean sulfoxidations in pure water.

Preparation and Applications of Hydrophilic Nano-Carbon Particles

2013 ◽  
Vol 832 ◽  
pp. 767-772 ◽  
Author(s):  
Shoichiro Ikeda ◽  
Shinji Kawasaki ◽  
Akinari Nobumoto ◽  
Hideo Ono ◽  
Shinji Ono ◽  
...  
Keyword(s):  
Carbon Nanoparticles ◽  
Room Temperature ◽  
Ph Value ◽  
Pure Water ◽  
Solid Lubricants ◽  
Cutting Fluids ◽  
Carbon Particles ◽  
Synthetic Graphite ◽  
Nano Carbon

We have produced nanocarbon suspension in pure water, which is named as Nanocaloid®, by a simple DC electrolysis from a synthetic graphite plates as anodes and SUS plates as cathodes in purified water at room temperature. The amount of carbon nanoparticles was monitored by the conductivity and pH value of the electrolyte solution, and also by a simple gravimetric way after drying the solution. If the current density increases, the diameter of the carbon particles becomes larger and the amount of precipitates becomes also large. It takes about six weeks to obtain about 0.4 wt% carbon suspension solution under the normal electrolysis conditions. Characterization of Nanocaloid®has been conducted to show unique properties and promising epoch-making applications such as solid lubricants for non-oily cutting fluids and conductive agents for reuse of deteriorated Pb-acid batteries. The performance of nanocarbon particles in oil lubricants in addition to the preparation will be reported.

scholarly journals Analysis of the Chloroacetanilide Herbicides in Water Using SPME with CAR/PDMS and GC/ECD

2005 ◽  
Vol 88 (4) ◽  
pp. 1236-1241 ◽  
Author(s):  
Ying-Ming Hwang ◽  
Yih-Gang Wong ◽  
Wu-Hsiung Ho
Keyword(s):  
Humic Acid ◽  
Ph Value ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Standard Addition ◽  
Electron Capture Detection ◽  
Detection Analysis ◽  
Salt Addition ◽  
Chloroacetanilide Herbicides ◽  
Relative Standard

Abstract The solid-phase microextraction (SPME) technique using a 75 mm film of carboxen/polydimethylsiloxane was applied to the analysis of chloroacetanilide herbicides (acetochlor, alachlor, butachlor, metolachlor, and propachlor) residues. The feasibility of SPME with gas chromatography electron capture detection analysis has been evaluated. The effects of experimental parameters such as magnetic stirring, salt addition, humic acid addition, pH value, and extraction time, as well as desorption temperature and time, were investigated. Analytical parameters such as linearity, repeatability and limit of detection were also evaluated. The inhibition of humic acid to the extraction of chloroacetanilide herbicides was observed. A standard addition method for calibration was recommended to reduce deviations caused by matrix interferences. The proposed method provided a simple and rapid analytical procedure for chloroacetanilide herbicides in water with limits of detection 0.002–0.065 μg/L for deionized water, and 0.005–0.22 μg/L for farm water. The relative standard deviations (n = 5) for analyses of farm water were 7–20% for 0.5 μg/L chloroacetanilide herbicides. This application was illustrated by the analysis of sample collected from farm water in the Chung-hwa area, Taiwan.

An Improved Method for the Quantification of Thiamine (Vitamin B1) in Cocoa-Containing Beverage Powders

2017 ◽  
Vol 100 (5) ◽  
pp. 1511-1515
Author(s):  
Frédéric Martin ◽  
Liliane Meyer ◽  
Konstantinos Zelianos ◽  
Esther Campos Gimenez
Keyword(s):  
Ph Value ◽  
Solid Phase ◽  
Vitamin B1 ◽  
Water Soluble ◽  
Local Market ◽  
Improved Method ◽  
Test Portion ◽  
Beverage Samples ◽  
Water Soluble Vitamin ◽  
Thiamine Content

Abstract The purpose of this work was to understand low recoveries of thiamine (vitamin B1) when extracted from cocoa-containing beverage powders fortified with water-soluble vitamin B1, and to develop and validate a new procedure to improve these results. Based on the literature, previous trials have focused on two main factors: pH value prior to paper filtration and the need for solid-phase extraction (SPE) clean up. We demonstrate that by following European Standard EN 14122, recovery of thiaminein cocoa-containing beverage powders is low and dependent on the test portion (86 and 72% for 0.5 and 1.5 g test portions, respectively). Our improved method resolved this problem by keeping the pH low (around 1) prior to paper filtration, leading to a 96.3% recovery and high precision (RSDr of 3.5%). The use of strong cation-exchange SPE cartridges for cleanup prior to the thiamine oxidation reaction proved to be essential. A comparison between our improved method and EN 14122 on nine cocoa-containing beverage samples available on local market from different manufacturers showed a systematic increase in thiamine content (up to 70%) when the improved methodwas applied. The highest difference was observed forthe sample that contained the highest amount of cocoa. However, for beverage powders that contained bothcocoa and milk, no difference was observed.

scholarly journals Micellization Behavior of Cetyltrimethylammonium bromide in Presence and Absence of Na2SO4 and MgSO4 in Aqueous media

BIBECHANA ◽  
2016 ◽  
Vol 14 ◽  
pp. 77-85 ◽  
Author(s):  
Chom Nath Adhikari ◽  
G S Shrivastav ◽  
Ajaya Bhattarai
Keyword(s):  
Surface Tension ◽  
Critical Micelle Concentration ◽  
Cetyltrimethylammonium Bromide ◽  
Pure Water ◽  
Aqueous Media ◽  
Presence And Absence ◽  
Micellization Behavior

Viscosity and surface tension measurements of cetyltrimethylammonium bromide (CTAB) in presence and absence of Na2SO4 and MgSO4 in aqueous media are reported. The results showed an increase in viscosity with increase in concentration of cetyltrimethylammonium bromide in presence and absence of salts where as the decrease in surface tension with increase in concentration of cetyltrimethylammonium bromide in presence and absence of salts. The viscosity of CTAB was observed lowest in pure water and increases in presence of MgSO4 and then more increases in presence of Na2SO4 where as the surface tension of CTAB was observed highest in pure water and decreases in presence of Na2SO4 and then more decreases in presence of MgSO4.The critical micelle concentration (cmc) of CTAB decreases in presence of salts in both viscosity and surface tension measurements. The decreasing cmc of CTAB are found to be more in the presence of Na2SO4 in comparison with the presence of MgSO4 for both measurements. The graphs of viscosity versus log[C] and the surface tension versus log[C] are used in determining the critical micelle concentration (cmc).        BIBECHANA 14 (2017) 77-85

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