scholarly journals Improvement in Metal Dissolution from Spent Catalyst by Adapted Acidithiobacillus ferrooxidans

2020 ◽  
Vol 11 (1) ◽  
pp. 7794-7803
Keyword(s):  
Elemental Sulfur ◽  
Adaptation Process ◽  
Leaching Rate ◽  
Metal Dissolution ◽  
Alumina Matrix ◽  
Spent Catalyst ◽  
Catalyst Sample ◽  
Bacterial Adaptation ◽  
Leaching Parameters ◽  
Low Solubility

The improvement in the leaching rate of Ni, V, Mo, and Al present in a spent catalyst sample was evaluated by the bacterial adaptation technique. For this purpose, leaching of the metals from the spent catalyst sample was conducted using both adapted and unadapted bacteria cultures. The evaluation was done on the basis of the variation of different leaching parameters such as pH, temperature, particle size, pulp density, and initial Fe(II) concentration. The adaptation technique was found to be fruitful as the leaching equilibrium reduced from 240 to 40hr. Further, the leaching rate of Ni and V was improved by 10%(w/w) due to bacterial adaptation. The leaching rate of Mo was lower due to combining the action of different factors like the presence of impervious elemental sulfur, refractory nature, and low solubility. The lower leaching rate of Al observed due to the refractoriness of the alumina matrix present in the spent catalyst sample. The pseudo rate order with respect to all leaching parameters was determined and found to be significant for the adaptation process.

scholarly journals Bioleaching of Cu and Zn from Complex Sulfide using an Isolated Iron Oxidizing Bacteria

2020 ◽  
Vol 10 (1) ◽  
pp. 1825-1832
Keyword(s):  
Metal Sulfide ◽  
Pulp Density ◽  
Leaching Rate ◽  
Metal Dissolution ◽  
Iron Oxidizing Bacteria ◽  
Complex Sulfide ◽  
Initial Ph ◽  
Leaching Parameters ◽  
Kinetics Of ◽  
Sulfide Concentrate

Bioleaching kinetics of copper and zinc from a complex sulfide concentrate sample was evaluated in this manuscript. An acidophilic microorganism was used for the metal dissolution. The metal dissolution was evaluated based on the variation of leaching parameters like initial pH, pulp density, and initial ferrous concentration. The leaching rate of metals increased with the increase of initial ferrous concentration up to 20g/L, and it decreased on a further increase of the initial ferrous concentration. It decreased at the initial ferrous concentration above 20g/L due to the formation of an iron precipitate, which did not allow the contact of lixiviant with the metal sulfide matrix. The leaching rate increased with the increase of initial pH up to 2.0, and thereafter it decreased. Similarly, the leaching rate remained unchanged up to pulp density of 15%(w/v), and it decreased upon further increase of the pulp density due to the mutual completion of the complex sulfide particles towards the lixiviants.

Electrochemical Study on the Bioleaching of Marmatite

2013 ◽  
Vol 774-776 ◽  
pp. 512-518 ◽  
Author(s):  
Zhuo Yue Lan ◽  
Di Fei Li ◽  
Qi Fu Zhang
Keyword(s):  
Cyclic Voltammetry ◽  
Passive Film ◽  
Elemental Sulfur ◽  
Copper Ions ◽  
High Potential ◽  
Leaching Rate ◽  
Electrochemical Tests ◽  
Bacterial Action ◽  
Electrochemical Mechanism ◽  
Potential Conditions

Shaking-flask experiments and electrochemical tests were conducted to study the bioleaching of marmatite with mixed cultures of mesophilic bacteria. The effects of copper ions and the surfactant, o-phenylenediamines (OPD) on the bioleaching were investigated. The electrochemical mechanism of the bioleaching was researched through cyclic voltammetry and chronoamperometry. The results show that the decrease in leaching rate was associated with a passive film (elemental sulfur) formed on the surface of marmatite in the leaching course. It was found that, however, the passive film dissolved readily under high potential conditions or with the bacterial action. Especially, in the presence of bacteria, the decomposition of the passive film was accelerated by adding either copper ions or OPD, leading to a significant increase in the bioleaching rate of marmatite.

scholarly journals Modified Cyclodextrins Solubilize Elemental Sulfur in Water and Enable Biological Sulfane Sulfur Delivery

2020 ◽  
Author(s):  
Sarah Bolton ◽  
Michael Pluth
Keyword(s):  
Elemental Sulfur ◽  
Complex Environments ◽  
Solubility In Water ◽  
Sulfane Sulfur ◽  
New Strategy ◽  
Raw 264.7 Macrophage Cells ◽  
And Storage ◽  
Low Solubility ◽  
Important Form ◽  
Mediated Reduction

An important form of biological sulfur is sulfane sulfur, or S<sup>0</sup>, which is found in polysulfide and persulfide compounds as well as in elemental sulfur. Sulfane sulfur, often in the form of S<sub>8</sub>, functions as a key energy source in the metabolic processes of thermophilic Archaean organisms found in sulfur-rich environments and can be metabolized both aerobically and anaerobically by different archaeons. Despite this importance, S<sub>8</sub> has a low solubility in water (~19 nM), raising questions of how it can be solubilized and made chemically accessible in complex environments. Motivated by prior crystallographic data showing S<sub>8</sub> binding to hydrophobic motifs in filamentous glycoproteins from the sulfur reducing <i>Staphylothermus marinus</i> anaerobe, we demonstrate that simple hydrophobic motifs, such as 2-hydroxypropyl β-cyclodextrin (2HPβ), are sufficient solubilize S<sub>8</sub> at concentrations up to 2.0 ± 0.2 mM in aqueous solution. We demonstrate that the solubilized S<sub>8</sub> is chemically accessible, can be reduced with <i>tris</i>(2-carboxyethyl)phosphine (TCEP), and reacts with thiols to generate H<sub>2</sub>S. The thiol-mediated conversion of 2HPβ/S<sub>8</sub> to H<sub>2</sub>S ranges from 80% to quantitative efficiency for Cys and glutathione (GSH). Moreover, we demonstrate that 2HPβ can catalyze the reaction of Cys-mediated reduction of S<sub>8</sub> to H<sub>2</sub>S in water. Adding to the biological relevance of the developed systems, we demonstrate that treatment of Raw 264.7 macrophage cells with the 2HPβ/S<sub>8</sub> complex prior to LPS stimulation reduces NO<sub>2</sub><sup>–</sup> levels, which is consistent with known activities of bioavailable H<sub>2</sub>S and sulfane sulfur. Taken together, these investigations provide a new strategy for delivering H<sub>2</sub>S and sulfane sulfur in complex systems and more importantly provide new insights into the chemical accessibility and storage of S<sup>0</sup> and S<sub>8</sub> in biological environments.

scholarly journals Modified Cyclodextrins Solubilize Elemental Sulfur in Water and Enable Biological Sulfane Sulfur Delivery

2020 ◽  
Author(s):  
Sarah Bolton ◽  
Michael Pluth
Keyword(s):  
Elemental Sulfur ◽  
Complex Environments ◽  
Solubility In Water ◽  
Sulfane Sulfur ◽  
New Strategy ◽  
Raw 264.7 Macrophage Cells ◽  
And Storage ◽  
Low Solubility ◽  
Important Form ◽  
Mediated Reduction

An important form of biological sulfur is sulfane sulfur, or S<sup>0</sup>, which is found in polysulfide and persulfide compounds as well as in elemental sulfur. Sulfane sulfur, often in the form of S<sub>8</sub>, functions as a key energy source in the metabolic processes of thermophilic Archaean organisms found in sulfur-rich environments and can be metabolized both aerobically and anaerobically by different archaeons. Despite this importance, S<sub>8</sub> has a low solubility in water (~19 nM), raising questions of how it can be solubilized and made chemically accessible in complex environments. Motivated by prior crystallographic data showing S<sub>8</sub> binding to hydrophobic motifs in filamentous glycoproteins from the sulfur reducing <i>Staphylothermus marinus</i> anaerobe, we demonstrate that simple hydrophobic motifs, such as 2-hydroxypropyl β-cyclodextrin (2HPβ), are sufficient solubilize S<sub>8</sub> at concentrations up to 2.0 ± 0.2 mM in aqueous solution. We demonstrate that the solubilized S<sub>8</sub> is chemically accessible, can be reduced with <i>tris</i>(2-carboxyethyl)phosphine (TCEP), and reacts with thiols to generate H<sub>2</sub>S. The thiol-mediated conversion of 2HPβ/S<sub>8</sub> to H<sub>2</sub>S ranges from 80% to quantitative efficiency for Cys and glutathione (GSH). Moreover, we demonstrate that 2HPβ can catalyze the reaction of Cys-mediated reduction of S<sub>8</sub> to H<sub>2</sub>S in water. Adding to the biological relevance of the developed systems, we demonstrate that treatment of Raw 264.7 macrophage cells with the 2HPβ/S<sub>8</sub> complex prior to LPS stimulation reduces NO<sub>2</sub><sup>–</sup> levels, which is consistent with known activities of bioavailable H<sub>2</sub>S and sulfane sulfur. Taken together, these investigations provide a new strategy for delivering H<sub>2</sub>S and sulfane sulfur in complex systems and more importantly provide new insights into the chemical accessibility and storage of S<sup>0</sup> and S<sub>8</sub> in biological environments.

scholarly journals Synthesis Optimization and Characterization of Microencapsulated N-P-K Slow-Release Fertilizers

2015 ◽  
Vol 13 (1) ◽  
Author(s):  
Constantin Neamţu ◽  
Mariana Popescu ◽  
Florin Oancea ◽  
Ştefan-Ovidiu Dima
Keyword(s):  
Slow Release ◽  
Activity Index ◽  
Leaching Rate ◽  
K Fertilizer ◽  
Slow Release Fertilizers ◽  
Ft Ir ◽  
Council Regulation ◽  
Leaching Parameters ◽  
Differential Thermogravimetry

AbstractSlow-release microencapsulated N, P, and K fertilizer synthesis was optimized and the products exhaustively characterized. Four NPK formulations with nutrient mass ratios of 1:0:0, 1:1:0, 1:1:1, and 2:1:1 were characterized following European Council Regulation 2003/2003 for fertilizers as well as ICP-AES, 1H-NMR, FT-IR, HPLC, elemental analysis, XPS, SEM, dynamic light scattering, thermogravimetry, differential thermogravimetry, activity index, and leaching rate. These fertilizers have good slow-release properties and decrease waste and crop contaminants, improving environmental protection. Compared to classic granulated fertilizers, plant nutrient availability was improved allowing reduced application. Nutrient leaching parameters describing four different kinetic models were evaluated.

scholarly journals Studying the impact of alkaline sulfide leaching parameters upon the efficiency of arsenic recovery from copper skimmings of lead production

2020 ◽  
pp. 19-24
Author(s):  
A. A. Tymbayeva ◽  
S. V. Mamyachenkov ◽  
S. A. Bannikova ◽  
O. S. Anisimova
Keyword(s):  
Elemental Sulfur ◽  
Arsenic Removal ◽  
Waste Product ◽  
Precious Metals ◽  
Advantages And Disadvantages ◽  
Lead Production ◽  
Solids Content ◽  
Leaching Parameters ◽  
The Impact ◽  
Alkaline Sulfide

The article is concerned with the problem of arsenic circulation as copper skimmings of lead production — the product of the lead bullion decopperization process at a metallurgical complex, uniting copper and lead plants. A brief overview of the methods of processing arsenic-containing middling products for the purpose of arsenic removal is given; the main advantages and disadvantages are indicated. The possibility of processing copper skimmings by the method of alkaline sulfide leaching with separation into arseniccontaining solution and lead-copper precipitate is studied. The results of the researches into the influence of temperature, process duration, solids content in the pulp, particle size, and the ratio of sodium hydroxide to elemental sulfur in the alkaline sulfide reagent on the process of alkaline sulfide leaching of copper skimmings af lead production are provided. Within the studied range of varied factors, the highest indexes of arsenic extraction into solution (85.04%) were achieved under the following conditions: temperature — 85 °C, duration — 4 hours, solids content in the pulp — 350 g/dm3, fraction (–0.08 mm), NaOH/S ratio = 100 g/100 g in 1 dm3 of the solution. The proposed method for processing copper skimmings will allow one to selectively isolate arsenic into the dump waste product during subsequent precipitation and separate contaminant from lead-copper cake, into which precious metals also pass. Such an approach provides the reduction of arsenic circulation between the lead and copper manufacturing facilities.

scholarly journals Liquid Radioactive Solidification Technologies

2019 ◽  
pp. 68-74 ◽  
Author(s):  
V. Svidersky ◽  
V. Glukhovsky ◽  
I. Glukhovsky ◽  
T. Dashkova
Keyword(s):  
Radioactive Waste ◽  
Nuclear Power ◽  
Power Plants ◽  
Liquid Radioactive Waste ◽  
Cement Stone ◽  
Leaching Rate ◽  
Additional Water ◽  
Volumetric Characteristics ◽  
Leaching Parameters ◽  
The Cost

This review provides a brief analysis of familiar and tested technologies of liquid radioactive waste solidification. The technologies of bituminization, vitrification and incorporation of radioactive waste into the polymer matrix are considered. The paper presents the efficiency indices of the conventional cementation technology and sets forth the results of calculating the cost of components for cementing liquid radioactive waste of various concentrations. Besides, there are results of calculating the volumetric characteristics of cement stone for water-cement relations used for cementing liquid radioactive waste. The review includes the results based on the development and implementation of solidification technologies for liquid radioactive waste using contact-hardening binders that form a durable waterproof stone at the time of pressing and do not require additional water for curing. Generated compounds for immobilization of liquid radioactive waste from nuclear power plants are tested to identify their strength characteristics, resistance to irradiation and leaching parameters. The paper covers the calculation of the cost of components for the solidification of liquid radioactive waste of various concentrations. The developed technology of liquid radioactive waste solidification allows obtaining compounds with strength up to 40 MPa. The volume of the final product is increased by 1.8 times, and the leaching rate is in the range of 1.10×10–4…9.5×10–5 kg/m2 per day.

Extract Vanadium and Molybdenum from Spent Catalyst

2014 ◽  
Vol 926-930 ◽  
pp. 128-131
Author(s):  
Shuan Xu ◽  
Yan Hai Shao ◽  
Ming Ming Li
Keyword(s):  
Sodium Carbonate ◽  
Good Effect ◽  
Leaching Rate ◽  
Spent Catalyst ◽  
Alkaline Leaching ◽  
Roasting Temperature ◽  
Counter Current ◽  
Roasting Time

Based on the analysis of the properties of spent catalyst, extract vanadium and molybdenum from spent catalyst by roasting alkaline leaching. Sodium carbonate was leaching agent. The effects of roasting temperature, roasting time, the concentration of sodium carbonate and the number of leaching times on the leaching rate of vanadium and molybdenum were studied. Roasting temperature of 650°C, roasting time of 3h, the concentration of sodium carbonate of 50g/L and once counter-current leaching, under this condition, the leaching of vanadium is 83% and the leaching of molybdenum is 93%.Roasting alkaline leaching has good effect on extracting vanadium and molybdenum from spent catalyst.

Recovery of Valuable Metals from Spent Hydrogenation Catalysts

2013 ◽  
Vol 440 ◽  
pp. 97-103 ◽  
Author(s):  
Ao Yun Xu ◽  
Tao Ye ◽  
Shu Hui Zhao
Keyword(s):  
Technological Process ◽  
Low Cost ◽  
Economic Benefits ◽  
Environmental Benefits ◽  
Leaching Rate ◽  
Spent Catalyst ◽  
Hydrogenation Catalysts ◽  
Recovery Method ◽  
Valuable Metals ◽  
Comprehensive Recovery

The recovery method and process of tungsten, nickel and aluminum from spent catalyst was investigated, which had realized the comprehensive recovery of valuable metals about tungsten, nickel and aluminum. The results showed that leaching rate of WO3 was above 95% and the recovery was 90.85%, nickel and aluminum leaching rate were 98.27% and 90% respectively, the recovery were 91.83% and 92.78% respectively. It had got the conclusion that the technological process was developed, low-cost, high-extraction and process feasibility with good economic benefits and environmental benefits.

scholarly journals Influence of chalcopyrite structure on their leaching by sodium nitrate in sulphuric acid

2014 ◽  
Vol 20 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Miroslav Sokić ◽  
Slobodan Radosavljević ◽  
Branislav Marković ◽  
Vladislav Matković ◽  
Nada Štrbac ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Sodium Nitrate ◽  
Final Stage ◽  
Elemental Sulfur ◽  
Chalcopyrite Structure ◽  
Leaching Rate ◽  
Structural Assembly ◽  
Hydrometallurgical Treatment ◽  
Chalcopyrite Concentrate ◽  
Complex Forms

During the chalcopyrite leaching by sodium nitrate and sulfuric acid solution, leaching rate decreases with increasing the time and a part of chalcopyrite mineral grains remains in the leach residue. In chalcopyrite concentrate, 95.5 % of chalcopyrite mineral occurs as in liberated grains, and the rest is in association with gangue minerals, which is very favorably from the aspect of hydrometallurgical treatment. Complex forms, like impregnations and complex intergrowths, do not exist. After experiments carried out, leaching of copper achieved 84 % at temperature 80 o C and time 240 min. In the all leach residues, 97 % chalcopyrite mineral grains occur as liberated with highly corroded surfaces. Therefore, the structural assembly of chalcopyrite grains is favorable and no reason to reduce the leaching rate in the final stage of reaction. Reason for this is elemental sulfur, which was formed during the reaction, precipitated at the particle surfaces, and slowed down the leaching rate in the final stage of leaching process. 

Sign in / Sign up

Export Citation Format

Share Document