scholarly journals HYPOCHLORITE GOLD LEACHING AN ALTERNATIVE TO CYANIDE TECHNOLOGY

2021 ◽  
Author(s):  
Vitaly Prokopenko ◽  
◽  
Volodymyr Chernenko ◽  
Pavlo Vorotytsky ◽  
Igor Volobaiev ◽  
...  
Keyword(s):  
Sodium Hypochlorite ◽  
Large Scale ◽  
Gold Mining ◽  
Native Gold ◽  
Sea Water ◽  
Surface Film ◽  
Energy Dispersive Spectrometer ◽  
Alternative Methods ◽  
Gold Dissolution ◽  
Gold Leaching

Traditional technologies of gold mining are exhausted due to the depletion of stocks of conditioned raw materials at functioning gold mining enterprises, in addition, the preservation or disposal of large-scale waste of these technologies requires significant financial costs for environmental protection measures. Recently, the search for alternative methods of gold leaching, which involve the use of non-toxic factors, but which in their physicochemical properties can compete with traditional levels, and especially with cyanides. The authors of this work investigated the mechanism and kinetics of the process of dissolving metallic gold in chloride-hypochlorite solutions and believe that alkali metal hypochlorites (first of all, sodium hypochlorite NaOCl, which is easily obtained by electrolysis from a solution of food’s salt NaCl, or from sea water) are a very promising replacement for cyanide-containing leachates. Two series of experiments were carried out to study sodium hypochlorite as a gold leaching agent using a traditional gold disk and finely dispersed native gold as dissolution objects. Found fundamental differences in methodological techniques when working with a traditional model object and native gold. The dependences of the dissolution rate on the solution pH, sodium hypochlorite concentration, and temperature are determined. Conditions of the gold surface passivation during its dissolution are discussed. The first-order rate constant of the gold dissolution 1 0,079 - 0,4030  ki  h at temperatures from 277 K to 304 K and others are calculated. The activation energy from the temperature dependence of the rate constants (40,3 kJ/mol) evidences a diffusion-kinetic control of the gold dissolution. Electron microscopy (using electron probe scanning on an energy dispersive spectrometer) of native gold particles revealed foreign inclusions - adsorbed mineral particles of calcite (CaCO3) and, presumably, a surface film consisting of aluminum oxide (Al2O3), which create a significant obstacle to the contact of leaching agents with the surface of the target gold grains. Quantitative data on the composition of surface adsorption films, formed by model gold electrode dissolution products, are obtained using atomic adsorption spectroscopy.

Microbiological Investigations of Surface Film Oil Across a Sea Water Discontinuity

1986 ◽  
Vol 18 (4-5) ◽  
pp. 343-343
Author(s):  
M G. J. Route ◽  
G. D. Floodgate
Keyword(s):  
Sea Water ◽  
Surface Film

Concrete Strength and Deformation Property under Sea Water Erosion Environment

2012 ◽  
Vol 446-449 ◽  
pp. 2554-2559 ◽  
Author(s):  
Jian Jun Cai ◽  
Feng Zhang ◽  
Wei Cui ◽  
Shou Shan Chen ◽  
Pu Lun Liu
Keyword(s):  
Large Scale ◽  
Failure Modes ◽  
Deformation Property ◽  
Sea Water ◽  
Dynamic Stiffness ◽  
Concrete Strength ◽  
Strain Curve ◽  
Water Erosion ◽  
Strength And Deformation ◽  
Erosion Environment

In order to effectively assess the concrete strength and deformation property under sea water erosion environment, concrete stress and strain curve was researched with the number of wet and dry cycle of 0 times, 10 times , 20 times, 30 times, 40 times, 50 times and 60 times based on the large-scale static and dynamic stiffness servo test set. The stress - strain curves of concrete was tested for the lateral pressure 10.8MPa, 14.4MPa, and 18.8MPa at different dry-wet cycles, The failure modes and superficial cracking characteristics of specimens are reported at different dry-wet cycles. Concrete elastic modulus and compressive strength were researched. Based on concrete mechanical theory , the classic Kufer-Gerstle strength criteria of concrete was used, a large number of test samples of multivariate data were nonlinear regressed, a biaxial concrete strength criterion was established taking into account the stress ratio and the number of dry-wet cycles.

scholarly journals Large scale extraction of poly(3-hydroxybutyrate) from Ralstonia eutropha H16 using sodium hypochlorite

AMB Express ◽  
2012 ◽  
Vol 2 (1) ◽  
pp. 59 ◽  
Author(s):  
Daniel Heinrich ◽  
Mohamed H Madkour ◽  
Mansour A Al-Ghamdi ◽  
Ibraheem I Shabbaj ◽  
Alexander Steinbüchel
Keyword(s):  
Sodium Hypochlorite ◽  
Large Scale ◽  
Ralstonia Eutropha ◽  
Ralstonia Eutropha H16

scholarly journals Retrieving Forest Canopy Elements Clumping Index Using ICESat GLAS Lidar Data

2021 ◽  
Vol 13 (5) ◽  
pp. 948
Author(s):  
Lei Cui ◽  
Ziti Jiao ◽  
Kaiguang Zhao ◽  
Mei Sun ◽  
Yadong Dong ◽  
...  
Keyword(s):  
Large Scale ◽  
Forest Canopy ◽  
Remote Sensing Data ◽  
Alternative Methods ◽  
High Signal ◽  
Laser Altimeter ◽  
Waveform Data ◽  
Forest Park ◽  
Clumping Index ◽  
The Impact

Clumping index (CI) is a canopy structural variable important for modeling the terrestrial biosphere, but its retrieval from remote sensing data remains one of the least reliable. The majority of regional or global CI products available so far were generated from multiangle optical reflectance data. However, these reflectance-based estimates have well-known limitations, such as the mere use of a linear relationship between the normalized difference hotspot and darkspot (NDHD) and CI, uncertainties in bidirectional reflectance distribution function (BRDF) models used to calculate the NDHD, and coarse spatial resolutions (e.g., hundreds of meters to several kilometers). To remedy these limitations and develop alternative methods for large-scale CI mapping, here we explored the use of spaceborne lidar—the Geoscience Laser Altimeter System (GLAS)—and proposed a semi-physical algorithm to estimate CI at the footprint level. Our algorithm was formulated to leverage the full vertical canopy profile information of the GLAS full-waveform data; it converted raw waveforms to forest canopy gap distributions and gap fractions of random canopies, which was used to estimate CI based on the radiative transfer theory and a revised Beer–Lambert model. We tested our algorithm over two areas in China—the Saihanba National Forest Park and Heilongjiang Province—and assessed its relative accuracies against field-measured CI and MODIS CI products. We found that reliable estimation of CI was possible only for GLAS waveforms with high signal-to-noise ratios (e.g., >65) and at gentle slopes (e.g., <12°). Our GLAS-based CI estimates for high-quality waveforms compared well to field-based CI (i.e., R2 = 0.72, RMSE = 0.07, and bias = 0.02), but they showed less correlation to MODIS CI (e.g., R2 = 0.26, RMSE = 0.12, and bias = 0.04). The difference highlights the impact of the scale effect in conducting comparisons of products with huge differences resolution. Overall, our analyses represent the first attempt to use spaceborne lidar to retrieve high-resolution forest CI and our algorithm holds promise for mapping CI globally.

Evaluation of the corrosion behavior of AZ31 magnesium alloy with different protein concentrations

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yucong Ma ◽  
Mohd Talha ◽  
Qi Wang ◽  
Zhonghui Li ◽  
Yuanhua Lin
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Surface Film ◽  
Energy Dispersive Spectrometer ◽  
Inhibitory Effect ◽  
Corrosion Process ◽  
High Concentration ◽  
Content Type ◽  
Atomic Force

Purpose The purpose of this paper is to study systematically the corrosion behavior of AZ31 magnesium (Mg) alloy with different concentrations of bovine serum albumin (BSA) (0, 0.5, 1.0, 1.5, 2.0 and 5.0 g/L). Design/methodology/approach Electrochemical impedance spectroscopy and potential dynamic polarization tests were performed to obtain corrosion parameters. Scanning electrochemical microscopy (SECM) was used to analyze the local electrochemical activity of the surface film. Atomic force microscope (AFM), Scanning electron microscope-Energy dispersive spectrometer and Fourier transform infrared spectroscopy were used to determine the surface morphology and chemical composition of the surface film. Findings Experimental results showed the presence of BSA in a certain concentration range (0 to 2.0 g/L) has a greater inhibitory effect on the corrosion of AZ31, however, the presence of high-concentration BSA (5.0 g/L) would sharply reduce the corrosion resistance. Originality/value When the concentration of BSA is less than 2.0 g/L, the corrosion resistance of AZ31 enhances with the concentration. The adsorption BSA layer will come into being a physical barrier to inhibit the corrosion process. However, high-concentration BSA (5.0 g/L) will chelate with dissolved metal ions (such as Mg and Ni) to form soluble complexes, which increases the roughness of the surface and accelerates the corrosion process.

Comparative Assessment of Resistance of Hardwearing Anodes, Ternary Coated with Iridium, Ruthenium and Titanium

2017 ◽  
Vol 265 ◽  
pp. 580-586 ◽  
Author(s):  
L.N. Fesenko ◽  
I.V. Pchelnikov ◽  
R.V. Fedotov
Keyword(s):  
Black Sea ◽  
Sodium Hypochlorite ◽  
Sodium Salt ◽  
Sea Water ◽  
Comparative Assessment ◽  
The Black Sea ◽  
Current Voltage ◽  
Iridium Oxides ◽  
Corrosive Resistance ◽  
Selection Of

A selection of anode coatings has been studied to get sodium hypochlorite in low concentrationduring the electrolysis of 3% solution of sodium salt and the Black Sea water. The corrosive resistance of anodes has been determined, with different batches of ruthenium and iridium oxides, as well as their characteristics: chlorine outlet while passing throughthe current, voltage on the cell, the dynamics of concentration growth of available chlorine in solution.

scholarly journals Maintaining Mutual Benefits between Investor and Local Community: Mechanisms to Reopen Lega Dambi Gold Mining, Ethiopia

2021 ◽  
Vol 2 (1) ◽  
pp. 55-81
Author(s):  
Abdisa Olkeba Jima
Keyword(s):  
Corporate Social Responsibility ◽  
Social Responsibility ◽  
Large Scale ◽  
Gold Mining ◽  
Local Community ◽  
Local Communities ◽  
Mining Operations ◽  
Mining Company ◽  
Social License ◽  
Corporate Social

Mining, specifically, large-scale gold mining has become one of the primary economic activities that play a pivotal role in the socio-economic development of one country. But there is no consensus among scholars whether gold mining companies maintain mutual benefits with local communities. The main objective of this research is to scrutinize the mechanism to be employed in reopening Lega Dambi large-scale gold mining by maintaining mutual benefits between the company and the local community. The researcher employed a qualitative method and a case study research design. Focus group discussions and semi-structured interviews were used to collect data from the local community, elders, religious leaders, Abbaa Gadaas, Guji Zone, and Odo Shakiso Woreda investment office, land management office, social and labor affair, mineral, and energy office administrators, and Odo Shakiso Woreda health station and Adola hospital. Secondary sources and regulatory frameworks such as FDRE Constitution and Mining Operations Proclamation No. 678/2010 were used to triangulate with primary data. The finding shows that Lega Dambi's large-scale gold mining company failed to maintain mutual benefits between itself and the local community. Basic tenets such as national and regional corporate social responsibility, community development agreement, impact and benefit agreements, social and labor plan, and social license were not implemented properly to balance the mutual benefit between the company and the local community. The researcher concluded that Lega Dambi large-scale gold mining company disregarded the role of the local community during commencement time albeit it had a strong relationship with the central government. Consequently, the company was terminated because of a bad relationship it had with the local community. It is recommended that national and regional corporate social responsibility that shows the company’s specific joint administration of the central and Oromia region governments should be designed and implemented fully. It is also recommended that discussions should be held with local communities and arrived at a consensus concerning the reopening of the company.

scholarly journals Multisite Research Ethics Review: Problems and Potential Solutions

2018 ◽  
Vol 5 ◽  
Author(s):  
Aidan Ferguson ◽  
Zubin Master
Keyword(s):  
Literature Review ◽  
Large Scale ◽  
Review Process ◽  
Alternative Methods ◽  
Ethics Review ◽  
Research Ethics Review ◽  
Institutional Review ◽  
Proposed Modification ◽  
Clinical Research Trials ◽  
Individual Ethics

Large scale, multisite clinical research trials have been increasing in frequency. As it stands currently, a research project performed at multiple institutions requires ethics review at each institution. While local (institutional) review may be necessary in some instances, repetitive reviews may require unnecessary changes and not serve to further protect participants. Multiple ethics reviews of a single study have been shown to delay research and require, in some cases, significant resources in order to fulfill the requests of individual ethics boards. This literature review discusses the conceptual issues and outlines empirical research surrounding multisite ethics review from different jurisdictions, as well as alternative methods to streamline the ethics review process including reciprocal review, centralized review, and a proposed modification to the centralized review process.

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