scholarly journals Leaching of Manganese from Marine Nodules at Room Temperature with the Use of Sulfuric Acid and the Addition of Tailings

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 289 ◽  
Author(s):  
Norman Toro ◽  
Manuel Saldaña ◽  
Jonathan Castillo ◽  
Freddy Higuera ◽  
Roxana Acosta
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Room Temperature ◽  
Sulfuric Acid Concentration ◽  
Future Research ◽  
Independent Variables ◽  
Series Of Experiments ◽  
Optimization Methodology ◽  
Cost Efficient

Based on the results obtained from a previous study investigating the dissolution of Mn from marine nodules with the use of sulfuric acid and foundry slag, a second series of experiments was carried out using tailings produced from slag flotation. The proposed approach takes advantage of the Fe present in magnetite contained in these tailings and is believed to be cost-efficient. The surface optimization methodology was used to evaluate the independent variables of time, particle size, and sulfuric acid concentration in the Mn solution. Other tests evaluated the effect of agitation speed and the MnO2/Fe2O3 ratio in an acid medium. The highest Mn extraction rate of 77% was obtained with an MnO2/Fe2O3 ratio of 1/2 concentration of 1 mol/L of H2SO4, particle size of −47 + 38 μm, and 40 min of leaching. It is concluded that higher rates of Mn extraction were obtained when tailings instead of slag were used, while future research needs to focus on determination of the optimum Fe2O3/MnO2 ratio to improve dissolution of Mn from marine nodules.

scholarly journals Initial Investigation into the Leaching of Manganese from Nodules at Room Temperature with the Use of Sulfuric Acid and the Addition of Foundry Slag—Part I

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 565 ◽  
Author(s):  
Norman Toro ◽  
Nelson Herrera ◽  
Jonathan Castillo ◽  
Cynthia Torres ◽  
Rossana Sepúlveda
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Acid Concentration ◽  
Room Temperature ◽  
Sulfuric Acid Concentration ◽  
Extraction Rate ◽  
Molar Ratio ◽  
Independent Variables ◽  
Initial Investigation ◽  
Optimization Methodology

In this study, the surface optimization methodology was used to assess the effect of three independent variables—time, particle size and sulfuric acid concentration—on Mn extraction from marine nodules during leaching with H2SO4 in the presence of foundry slag. The effect of the MnO2/Fe ratio and particle size (MnO2) was also investigated. The maximum Mn extraction rate was obtained when a MnO2 to Fe molar ratio of 0.5, 1 M of H2SO4, −320 + 400 Tyler mesh (−47 + 38 μm) nodule particle size and a leaching time of 30 min were used.

scholarly journals An Alternative Process for Leaching Chalcopyrite Concentrate in Nitrate-Acid-Seawater Media with Oxidant Recovery

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 518 ◽  
Author(s):  
César I. Castellón ◽  
Pía C. Hernández ◽  
Lilian Velásquez-Yévenes ◽  
María E. Taboada
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Alkaline Solution ◽  
Sodium Nitrite ◽  
Sodium Nitrate ◽  
Room Temperature ◽  
Leaching Test ◽  
Copper Concentrate ◽  
Leaching Process ◽  
Chalcopyrite Concentrate

An alternative copper concentrate leaching process using sodium nitrate and sulfuric acid diluted in seawater followed by gas scrubbing to recover the sodium nitrate has been evaluated. The work involved leaching test carried out under various condition by varying temperature, leaching time, particle size, and concentrations of NaNO3 and H2SO4. The amount of copper extracted from the chalcopyrite concentrate leached with seawater, 0.5 M of H2SO4 and 0.5 M of NaNO3 increased from 78% at room temperature to 91% at 45 °C in 96 h and 46 h of leaching, respectively. Gas scrubbing with the alkaline solution of NaOH was explored to recover part of the sodium nitrate. The dissolved salts were recovered by evaporation as sodium nitrate and sodium nitrite crystals.

Determination of Mercury in Biological Materials

1970 ◽  
Vol 53 (6) ◽  
pp. 1172-1175 ◽  
Author(s):  
M T Jeffus ◽  
J S Elkins ◽  
C T Kenner
Keyword(s):  
Sulfuric Acid ◽  
Standard Deviation ◽  
Nitric Acid ◽  
Biological Samples ◽  
Room Temperature ◽  
Gold Foil ◽  
Average Recovery ◽  
Average Value ◽  
The Difference

Abstract Mercury in biological samples is determined by digestion in nitric acid, sulfuric acid, and permanganate, followed by reduction and aeration for measurement by atomic absorption at room temperature. The average recovery is 95.8% with a standard deviation of 13.3%. The standard deviation, calculated from the difference between duplicates of 23 samples, is 0.063 μg mercury, which represents 9.4% of the average value of the samples. The method is simple and requires approximately 4 hr for completion. Mercury can be confirmed by adsorption on gold foil after maximum absorbance has been obtained during aeration.

scholarly journals Hygroscopicity of nanoparticles produced from homogeneous nucleation in the CLOUD experiments

2016 ◽  
Vol 16 (1) ◽  
pp. 293-304 ◽  
Author(s):  
J. Kim ◽  
L. Ahlm ◽  
T. Yli-Juuti ◽  
M. Lawler ◽  
H. Keskinen ◽  
...  
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Chemical Composition ◽  
Water Uptake ◽  
Sulfuric Acid Concentration ◽  
Particle Growth ◽  
Small Mass ◽  
Initial Growth ◽  
Formation Processes ◽  
The Difference

Abstract. Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation and initial growth of atmospheric particles. Because of the challenges involved in determining the chemical composition of objects with very small mass, however, the properties of the freshly nucleated particles and the detailed pathways of their formation processes are still not clear. In this study, we focus on a challenging size range, i.e., particles that have grown to diameters of 10 and 15 nm following nucleation, and measure their water uptake. Water uptake is useful information for indirectly obtaining chemical composition of aerosol particles. We use a nanometer-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) at subsaturated conditions (ca. 90 % relative humidity at 293 K) to measure the hygroscopicity of particles during the seventh Cosmics Leaving OUtdoor Droplets (CLOUD7) campaign performed at CERN in 2012. In CLOUD7, the hygroscopicity of nucleated nanoparticles was measured in the presence of sulfuric acid, sulfuric acid–dimethylamine, and sulfuric acid–organics derived from α-pinene oxidation. The hygroscopicity parameter κ decreased with increasing particle size, indicating decreasing acidity of particles. No clear effect of the sulfuric acid concentration on the hygroscopicity of 10 nm particles produced from sulfuric acid and dimethylamine was observed, whereas the hygroscopicity of 15 nm particles sharply decreased with decreasing sulfuric acid concentrations. In particular, when the concentration of sulfuric acid was 5.1 × 106 molecules cm−3 in the gas phase, and the dimethylamine mixing ratio was 11.8 ppt, the measured κ of 15 nm particles was 0.31 ± 0.01: close to the value reported for dimethylaminium sulfate (DMAS) (κDMAS ∼ 0.28). Furthermore, the difference in κ between sulfuric acid and sulfuric acid–imethylamine experiments increased with increasing particle size. The κ values of particles in the presence of sulfuric acid and organics were much smaller than those of particles in the presence of sulfuric acid and dimethylamine. This suggests that the organics produced from α-pinene ozonolysis play a significant role in particle growth even at 10 nm sizes.

scholarly journals Study of The Biomass, Sand, and Biochar Fluidization in A Typical Bed of Fast Pyrolysis

2021 ◽  
Author(s):  
David Vasconcelos ◽  
José Ferreira Júnior ◽  
George Simonelli ◽  
Luiz Carlos Santos ◽  
Carlos Augusto de Moraes Pires
Keyword(s):  
Particle Size ◽  
Room Temperature ◽  
Fast Pyrolysis ◽  
Ternary Mixtures ◽  
Biomass Pyrolysis ◽  
Particle Segregation ◽  
New Correlation ◽  
Large Particles ◽  
Series Of Experiments ◽  
Biomass Transformation

Abstract Biomass pyrolysis usually occurs in a fluidized bed reactor formed by sand, biomass, and biochar. Dynamics this fluidization differs from that of literature because the biomass is converted continually in biochar. In this study, a series of experiments have been carried out for ternary mixtures of sand, sisal residue, and biochar, varying the compositions and particle size. The tests were based on two simplification hypotheses (steady state and room temperature) due to fast biomass transformation in bed and low Van der Waals force to large particles. The dynamic characteristics determined included the bed pressure drop and bed fluctuation. The single and combined effects of particle size and composition on the final fluidization velocity (Uff) and particle segregation (S) have been analyzed using response surface (RSM). The Uff and S minimum values were found when the variables were in the smallest particle size and composition levels. New correlations were developed for predicting the values of Uff. The error from measured values when using the new correlation was 7.6%, while the literature equation was 9.7%. The present correlations predicted reasonably well predicted the Uff of ternary mixtures in the fast pyrolysis bed.

scholarly journals PEMANFAATAN LIMBAH BATANG JAGUNG SEBAGAI ADSORBEN ALTERNATIF PADA PENGURANGAN KADAR KLORIN DALAM AIR OLAHAN (TREATED WATER)

2013 ◽  
Vol 2 (2) ◽  
pp. 1-5
Author(s):  
Fatimah Rahmayani ◽  
Siswarni MZ
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Environmental Pollution ◽  
Acid Concentration ◽  
Iodine Value ◽  
Agricultural Waste ◽  
Sulfuric Acid Concentration ◽  
Value Added ◽  
Treated Water ◽  
High Cellulose

Various result of agricultural waste that contain high cellulose can be used as an alternative adsorbent. One of them was derived from dried corn stalks which traditionally burnt after harvest that lead to environmental pollution. It is necessary to produce the value-added materials from corn stalks waste as an alternative adsorbent to reduce the level of chlorine in treated water. This process was performed by using various level of sulfuric acid concentration 1%, 3% and 5%, particles size 50 and 70 mesh in 105 oC with adsorbtion time 30, 60 and 90 minutes. The most favorable activation result was obtained at 5% concentration, with particle size 70 mesh, adsorbtion time 90 minutes and the iodine value was 482 mg/l with level of adsorbed chlorine was 96,08%. Based on this findings, we concluded that the corn stalks waste can be used as an alternative adsorbent in reducing the level of chlorine in treated water.

The hydrolyses of benzamides, methylbenzimidatium ions, and lactams in aqueous sulfuric acid. The excess acidity method in the determination of reaction mechanisms

1981 ◽  
Vol 59 (19) ◽  
pp. 2853-2863 ◽  
Author(s):  
Robin A. Cox ◽  
Keith Yates
Keyword(s):  
Sulfuric Acid ◽  
Water Molecule ◽  
Reaction Pathway ◽  
Sulfuric Acid Concentration ◽  
Strong Acid ◽  
Hydrolysis Rate ◽  
Reaction Conditions ◽  
Acid Media ◽  
Hydrolysis Of

The excess acidity method has been applied to hydrolysis rate data for a number of benzamides, methylbenzimidatium ions, and lactams, obtained as a function of sulfuric acid concentration and temperature. All of the substrates studied except β-propiolactam (8) and methyl-2,6-dimethylbenzimidatium ion (7) were found to follow the AOT2 mechanism at all acidities. The excess acidity method provided considerable mechanistic detail; in dilute acid the transition state contains O-protonated (or methylated) substrate and three water molecules (large negative ΔS≠), but in more concentrated solutions a one-water-molecule mechanism takes over (smaller negative ΔS≠). In strong acid bisulfate ion acts as the nucleophile (positive ΔS≠). N-protonated intermediates are not involved for "normal" substrates, being observed in this work only for 8, which follows the AND1 pathway. Observed differences between benzamide and methylbenzimidatium ion (4) hydrolyses are due to their differing activity coefficient behaviour, the mechanism being the same for both. The hydrolysis of 7 involves a one-water-molecule SN2 displacement at the O-methyl group. Comparison with 7 shows that this displacement is not likely to occur under the reaction conditions for 4; however, for the N-methyl and N,N-dimethyl derivatives studied it is probably an important reaction pathway. A comprehensive mechanistic framework for amide hydrolyses in strong acid media is given.

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