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.

scholarly journals Effect of FE (II) Concentration on Bioleaching of Zinc from Sphalerite using Leptospirillum Ferriphilum: Kinetic Aspects

2019 ◽  
Vol 9 (1) ◽  
pp. 1492-1498
Keyword(s):  
Inoculum Size ◽  
Molecular Techniques ◽  
Leaching Rate ◽  
Experimental Conditions ◽  
Leptospirillum Ferriphilum ◽  
Ash Layer ◽  
Initial Ph ◽  
System Temperature ◽  
Shrinking Core ◽  
Kinetics Of

The objective of this study was to isolate an acidophilic iron-oxidizing bacterium, Leptospirillum ferriphilum, and explore the impacts of initial Fe(II) concentration on the bioleaching kinetics of zinc retrieval from sphalerite concentrate. L. ferriphilum strain was successfully isolated from Chitradurga mine, Karnataka, India, and molecular techniques for DNA sequencing were applied. The obtained nucleotide sequence was deposited to GenBank and accession number KF743135 was granted. The effect of Fe(II) on the iron-based bioleaching kinetics of zinc leaching using the L. ferriphilum isolate was ascertained under the following experimental conditions: inoculum size, 10% (v/v); bioleaching period, 20 days; system temperature, 301±2 K; initial pH, 3; pulp density 5% (w/v); and Fe(II) concentration in the medium, 1–9 g/L. The results demonstrated that efficiency of bioleaching was highly influenced by concentration of Fe(II) and maximized yield of 87.85% zinc was obtained at 7 g/L. The kinetic study specify that the rate constant estimations of zinc biosolubilization were moderately high at 7 g/L Fe(II), and the kinetic analysis using shrinking core model showed that the leaching rate is constrained by ash layer diffusion step

Biooxidation of Refractory Gold Ores by Mixed Moderate Thermophiles in Airlift Bioreactor

2009 ◽  
Vol 71-73 ◽  
pp. 469-472 ◽  
Author(s):  
Xue Hui Xie ◽  
Sheng Mu Xiao ◽  
Hua Tai Wang ◽  
Jian She Liu
Keyword(s):  
Particle Size ◽  
Aeration Rate ◽  
Pulp Density ◽  
Airlift Bioreactor ◽  
Leaching Rate ◽  
Gold Ore ◽  
Refractory Gold ◽  
Initial Ph ◽  
Moderate Thermophiles ◽  
Arsenic Leaching

Bacterial preoxidation of refractory gold ore has showed many advantages, such as lower operation cost and environmental friendly. In this paper, biooxidation of refractory gold ore by mixed moderate thermophiles culture in airlift bioreactor has been well studied. Firstly, a laboratory scale airlift bioreactor unit has been designed for bacterial preoxidation of refractory gold ore, a mixed moderate thermophilic culture was incubated. The orthogonal experiment was performed to investigate the effects of particle size, pulp density, aeration rate and initial pH. The results showed that when particle size 37micrometer，pulp density 5%，aeration rate 4 dm3•s-1 and initial pH 1.2, the arsenic leaching rate achieved to 93.5%. On the base of the airlift bioreactor unit, a continuous airlift bioreactor was designed. The preoxidation of refractory gold ore by a mixed culture of moderately thermophilic bacteria also was investigated in this equipment. The results showed that, under the conditions of pulp density 8% and stay time 60h, it can deal with 0.256 kg refractory gold ore per day, and the arsenic leaching rate can reach to 95.25%. During the experiment, some leaching liquor has been sampled from the second sect the fourth column of the continuous airlift bioreactor. The composition of microbial communities in this sample has been investigated using culture-independent 16S rDNA based cloning approach- restriction fragment length polymorphism. The phylogenetic analysis revealed that Leptospirillum ferriphilum and Acidithiobacillus caldus are the main organisms in this system. Both of them are moderate thermphilic bacteria and can resist relatively high concentration of arsenic ion.

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.

Study on leaching kinetics of hexavalent chromium from aged calcium-free chromium slag

2021 ◽  
pp. 1-13
Author(s):  
Quan Qi ◽  
Liang Li ◽  
Liangyu Wei ◽  
Baoming Hu ◽  
Zheng Liu ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Resource Utilization ◽  
Scientific Basis ◽  
Diffusion Reaction ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Chromium Slag ◽  
Leaching Solution ◽  
Main Components ◽  
Kinetics Of

To provide a scientific basis for the resource utilization of chromium slag, this article studies the release law of hexavalent chromium in the aged calcium-free chromium slag. XRD (X-ray diffractometer) and MLA (Mineral Liberation Analyzer) were used to analyze the composition of the chromium slag; using sulfuric acid-nitric acid as the leaching solution, the release law of hexavalent chromium in chromium slag and the leaching kinetics were studied. The results show that main components of the chromium slag are magnesioferrite, chromite, hematite, hydrargillite, and spinel; chromium is mainly present in chromite and magnesioferrite; the leaching rate of hexavalent chromium increases with the increase of temperature or the decrease of pH. The analysis of leaching kinetics shows the leaching rate is controlled by the internal diffusion reaction, and the apparent activation energy is 11.93 kJ·mol–1. The chromium slag is aged in high temperature seasons, which is conducive to the precipitation of hexavalent chromium in the chromium slag, can increase the yield of chromate in the roasting kiln, and is conducive to resource utilization; chromium slag should be stored in order to prevent acid rain erosion which leads to environmental pollution risk (e.g. drinking water).

scholarly journals Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1176
Author(s):  
Fuqiang Zheng ◽  
Yufeng Guo ◽  
Feng Chen ◽  
Shuai Wang ◽  
Jinlai Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electric Furnace ◽  
Kinetic Equations ◽  
Surface Chemical ◽  
Leaching Rate ◽  
Surface Chemical Reaction ◽  
Mechanism And Kinetics ◽  
Semi Empirical ◽  
Kinetics Of ◽  
Furnace Slag

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

scholarly journals Silica Removal from a Paper Mill Effluent by Adsorption on Pseudoboehmite and γ-Al2O3

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2031
Author(s):  
Ruben Miranda ◽  
Isabel Latour ◽  
Angeles Blanco
Keyword(s):  
Paper Mill ◽  
Ph Adjustment ◽  
Paper Mill Effluent ◽  
Kinetics Studies ◽  
Silica Removal ◽  
Industrial Water Use ◽  
Optimum Ph ◽  
Initial Ph ◽  
Equilibrium And Kinetics ◽  
Kinetics Of

Effluent reuse is a common practice for sustainable industrial water use. Salt removal is usually carried out by a combination of membrane processes with a final reverse osmosis (RO). However, the presence of silica limits the RO efficiency due to its high scaling potential and the difficulty of cleaning the fouled membranes. Silica adsorption has many advantages compared to coagulation and precipitation at high pHs: pH adjustment is not necessary, the conductivity of treated waters is not increased, and there is no sludge generation. Therefore, this study investigates the feasibility of using pseudoboehmite and its calcination product (γ-Al2O3) for silica adsorption from a paper mill effluent. The effect of sorbent dosage, pH, and temperature, including both equilibrium and kinetics studies, were studied. γ-Al2O3 was clearly more efficient than pseudoboehmite, with optimal dosages around 2.5–5 g/L vs. 7.5–15 g/L. The optimum pH is around 8.5–10, which fits well with the initial pH of the effluent. The kinetics of silica adsorption is fast, especially at high dosages and temperatures: 80–90% of the removable silica is removed in 1 h. At these conditions, silica removal is around 75–85% (<50 mg/L SiO2 in the treated water).

The chronopotentiometric method for measuring the kinetics of metal dissolution and cementation reactions

1996 ◽  
Vol 26 (5) ◽  
pp. 509-514 ◽  
Author(s):  
J. Zheng ◽  
M. Khan ◽  
S. R. La Brooy ◽  
I. M. Ritchie ◽  
P. Singh
Keyword(s):  
Metal Dissolution ◽  
Kinetics Of

Oxidation of Copper Sulfides in Aqueous Ammonia. III. Kinetic Characteristics

1979 ◽  
Vol 32 (12) ◽  
pp. 2597 ◽  
Author(s):  
AO Filmer ◽  
AJ Parker ◽  
BW Clare ◽  
LGB Wadley
Keyword(s):  
Aqueous Ammonia ◽  
Sulfide Oxidation ◽  
Metal Sulfide ◽  
Diffusion Control ◽  
Sulfate Ions ◽  
Kinetics Of Oxidation ◽  
Copper Sulfides ◽  
Shrinking Core ◽  
Kinetics Of ◽  
And Diffusion

The kinetics of oxidation with oxygen of chalcocite, Cu2S, to CuS in buffered aqueous ammonia at pH 10.5 at 30� can be modeled approximately by a shrinking core of Cu2S within a thickening shell of CuxS (x ≥ 1). The Cu2S core offers partial cathodic protection to the CuxS and diffusion of Cu+ through CuxS controls the rate of reaction. The kinetics of oxidation of covellite, CuS, to Cu2+, sulfur and sulfate ions in the same solvent can be modeled by a shrinking core of CuS surrounded by a shrinking sphere of CuyS (y < 1) which is much less effectively protected cathodically by the CuS core. Oxidation of CuS is subject to mixed chemical and diffusion control. Rates of oxidation of NiS and of CuS, in the presence and absence of tetrachloroethene and ammonium sulfate, show that, whether sulfur is a major oxidation product or not, the presence of sulfur has very little, if any, influence on the rate or mechanism of oxidation. This is contrary to current ideas on metal sulfide oxidation.

scholarly journals Study on indium leaching from mechanically activated hard zinc residue

2011 ◽  
Vol 47 (1) ◽  
pp. 63-72 ◽  
Author(s):  
J.H. Yao ◽  
X.H. Li ◽  
Y.W. Li
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Planetary Mill ◽  
Leaching Rate ◽  
Obvious Effect ◽  
Diffusion Controlled ◽  
Leaching Reaction ◽  
Kinetics Of ◽  
Positive Effect ◽  
Solution Kinetics

In this study, changes in physicochemical properties and leachability of indium from mechanically activated hard zinc residue by planetary mill were investigated. The results showed that mechanical activation increased specific surface area, reaction activity of hard zinc residue, and decreased its particle size, which had a positive effect on indium extraction from hard zinc residue in hydrochloric acid solution. Kinetics of indium leaching from unmilled and activated hard zinc residue were also investigated, respectively. It was found that temperature had an obvious effect on indium leaching rate. Two different kinetic models corresponding to reactions which are diffusion controlled, [1-(1- x)1/3]2=kt and (1-2x/3)-(1-x)2/3=kt were used to describe the kinetics of indium leaching from unmilled sample and activated sample, respectively. Their activation energies were determined to be 17.89 kJ/mol (umilled) and 11.65 kJ/mol (activated) within the temperature range of 30?C to 90?C, which is characteristic for a diffusion controlled process. The values of activation energy demonstrated that the leaching reaction of indium became less sensitive to temperature after hard zinc residue mechanically activated by planetary mill.

scholarly journals Leaching of Silver Contained in Mining Wastes Using the Thiosemicarbazide – Oxygen System

2018 ◽  
Author(s):  
Eleazar-Rodríguez Salinas ◽  
Juan Hernández-Ávila ◽  
Ma. Isabel Reyes-Valderrama ◽  
Eduardo Cerecedo-Sáenz ◽  
Demetrio Mendoza-Anaya ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Effect Of Temperature ◽  
Mining Wastes ◽  
Leaching Rate ◽  
Partial Pressure Of Oxygen ◽  
Silver Recovery ◽  
Oxygen System ◽  
Stirring Rate ◽  
Kinetics Of ◽  
Representative Samples

The mining wastes generated during the last decades in the mining region of Pachuca-Real del Monte in Mexico, still contains silver values of interest. For this reason, the present work is a preliminary study of the leaching kinetics of silver contained in these residues, using as a leaching reagent the thiosemicarbazide-oxygen system, with the aim of proposing this leaching system as a less toxic alternative than cyaniding process. Previous the leaching process, representative samples were wholly characterized, finding 56 g of Ag and 0.6 g of Au per ton. For the kinetic study in the mentioned system, were evaluated the reagent concentration, temperature, partial pressure of oxygen, pH and stirring rate. According the experimental results found, it was observed that [CH5N3S] concentration showed a significant effect on the leaching rate, obtaining a reaction order of n = 0.93, in the range of 20 - 40 mol CH5N3S &sdot; m-3, getting so a silver recovery up to 76.9%. The effect of temperature gave an activation energy of Ea = 45.55 KJ mol-1, which was indicative of a chemical reaction control. Finally, partial pressure of oxygen has a notable effect on leaching rate, but pH and stirring rate have not apparent effect.

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