Electrochemical spectral induced polarization modeling of artificial sulfide-sand mixtures

Geophysics ◽  
2014 ◽  
Vol 79 (6) ◽  
pp. EN91-EN106 ◽  
Author(s):  
Edmundo Placencia-Gómez ◽  
Lee D. Slater
Keyword(s):  
Mine Drainage ◽  
Mine Waste ◽  
Induced Polarization ◽  
Phase Response ◽  
Silica Sand ◽  
Model Parameters ◽  
Oxidation Degree ◽  
Spectral Induced Polarization ◽  
Current Densities ◽  
The Stability

We examined the sensitivity of the electrochemical spectral induced polarization (SIP) model developed by Wong to the oxidation extent of pyrite and pyrrhotite minerals disseminated in silica sand. The sensitivity of this model to the oxidation of sulfide minerals was mainly related to the model parameters defining the ratio of the active to the inactive passive ions [Formula: see text] dissolved in the pore water, and the variation of the current reaction parameters [Formula: see text] and [Formula: see text]. The increase in these parameters as well as in the associated exchange current densities, [Formula: see text] and [Formula: see text] was consistent with an increase in the activation of the charge transfer at the metal-electrolyte interface, resulting in the decrease in polarization of such an interface, which was reflected by a decrease in the SIP phase response as previously argued by Wong. Under this premise, the model described fairly well measurements below 500 Hz from a laboratory experiment, being consistent with the depletion of the SIP phase response associated with the oxidation degree promoted on the disseminate sulfides analyzed here. This suggested that electrochemical modeling of SIP measurements can provide information to assess the oxidation state of sulfides and also to infer the formation of passivating layers coating the metal minerals during oxidation-dissolution processes. Our results suggested a possible alternative for the monitoring of mine waste deposits producing acid mine drainage and the stability of sequestered harmful metals during remedial treatments by means of the SIP method.

scholarly journals Laboratory study of spectral induced polarization responses of magnetite — Fe2+ redox reactions in porous media

Geophysics ◽  
2014 ◽  
Vol 79 (1) ◽  
pp. D21-D30 ◽  
Author(s):  
Christopher G. Hubbard ◽  
L. Jared West ◽  
Juan Diego Rodriguez-Blanco ◽  
Samuel Shaw
Keyword(s):  
Redox Reactions ◽  
Induced Polarization ◽  
Phase Response ◽  
Field Surveys ◽  
Spectral Induced Polarization ◽  
Reducing Conditions ◽  
Redox Active ◽  
Large Phase ◽  
Ph Range

Spectral induced polarization (SIP) phase anomalies in field surveys at contaminated sites have previously been shown to correlate with the occurrence of chemically reducing conditions and/or semiconductive minerals, but the reasons for this are not fully understood. We report a systematic laboratory investigation of the role of the semiconductive mineral magnetite and its interaction with redox-active versus redox-inactive ions in producing such phase anomalies. The SIP responses of quartz sand with 5% magnetite in solutions containing redox-inactive [Formula: see text] and [Formula: see text] versus redox-active [Formula: see text] were measured across the pH ranges corresponding to adsorption of these metals to magnetite. With redox inactive ions [Formula: see text] and [Formula: see text], SIP phase response showed no changes across the pH range 4–10, corresponding to their adsorption, showing [Formula: see text] anomalies peaking at [Formula: see text]–74 Hz. These large phase anomalies are probably caused by polarization of the magnetite-solution interfaces. With the redox-active ion [Formula: see text], frequency of peak phase response decreased progressively from [Formula: see text] to [Formula: see text] as effluent pH increased from four to seven, corresponding to progressive adsorption of [Formula: see text] to the magnetite surface. The latter frequency (3 Hz) corresponds approximately with those of phase anomalies detected in field surveys reported elsewhere. We conclude that pH sensitivity arises from redox reactions between [Formula: see text] and magnetite surfaces, with transfer of electrical charge through the bulk mineral, as reported in other laboratory investigations. Our results confirm that SIP measurements are sensitive to redox reactions involving charge transfers between adsorbed ions and semiconductive minerals. Phase anomalies seen in field surveys of groundwater contamination and biostimulation may therefore be indicative of iron-reducing conditions, when semiconductive iron minerals such as magnetite are present.

scholarly journals On the use of the Cole–Cole equations in spectral induced polarization

2013 ◽  
Vol 195 (1) ◽  
pp. 352-356 ◽  
Author(s):  
Andrey Tarasov ◽  
Konstantin Titov
Keyword(s):  
Time Constant ◽  
Angular Frequency ◽  
Induced Polarization ◽  
Model Parameters ◽  
Data Sets ◽  
Polarization Data ◽  
Spectral Induced Polarization ◽  
The Difference ◽  
Fitting Model ◽  
Fitting Parameters

Abstract Two different equations, both of which are often called ‘the Cole–Cole equation’, are widely used to fit experimental Spectral Induced Polarization data. The data are compared on the basis of fitting model parameters: the chargeability, the time constant and the exponent. The difference between the above two equations (the Cole–Cole equation proposed by the Cole brothers and Pelton's equation) is manifested in one of the fitting parameters, the time constant. The Cole–Cole time constant is an inverse of the peak angular frequency of the imaginary conductivity, while Pelton's time constant depends on the chargeability and exponent values. The difference between the time constant values corresponding to the above two equations grows with the increase of the chargeability value, and with the decrease of the Cole–Cole exponent value. This issue must be taken into consideration when comparing the experimental data sets for high polarizability media presented in terms of the Cole–Cole parameters.

scholarly journals Spectral Induced Polarization Survey with Distributed Array System for Mineral Exploration: Case Study in Saudi Arabia

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 769 ◽  
Author(s):  
Fouzan A. Alfouzan ◽  
Abdulrahman M. Alotaibi ◽  
Leif H. Cox ◽  
Michael S. Zhdanov
Keyword(s):  
Effective Medium Theory ◽  
Coupling Effect ◽  
Pilot Project ◽  
Drill Hole ◽  
Induced Polarization ◽  
Effective Medium ◽  
Inductive Coupling ◽  
Geothermal Resources ◽  
Spectral Induced Polarization ◽  
Distributed Array

The Saudi Arabian Glass Earth Pilot Project is a geophysical exploration program to explore the upper crust of the Kingdom for minerals, groundwater, and geothermal resources as well as strictly academic investigations. The project began with over 8000 km2 of green-field area. Airborne geophysics including electromagnetic (EM), magnetics, and gravity were used to develop several high priority targets for ground follow-up. Based on the results of airborne survey, a spectral induced polarization (SIP) survey was completed over one of the prospective targets. The field data were collected with a distributed array system, which has the potential for strong inductive coupling. This was examined in a synthetic study, and it was determined that with the geometries and conductivities in the field survey, the inductive coupling effect may be visible in the data. In this study, we also confirmed that time domain is vastly superior to frequency domain for avoiding inductive coupling, that measuring decays from 50 ms to 2 s allow discrimination of time constants from 1 ms to 5 s, and the relaxation parameter C is strongly coupled to intrinsic chargeability. We developed a method to fully include all 3D EM effects in the inversion of induced polarization (IP) data. The field SIP data were inverted using the generalized effective-medium theory of induced polarization (GEMTIP) in conjunction with an integral equation-based modeling and inversion methods. These methods can replicate all inductive coupling and EM effects, which removes one significant barrier to inversion of large bandwidth spectral IP data. The results of this inversion were interpreted and compared with results of drill hole set up in the survey area. The drill hole intersected significant mineralization which is currently being further investigated. The project can be considered a technical success, validating the methods and effective-medium inversion technique used for the project.

scholarly journals Bioleaching of Pyrrhotite with Bacterial Adaptation and Biological Oxidation for Iron Recovery

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 295
Author(s):  
Bong-Ju Kim ◽  
Yong-Kwon Koh ◽  
Jang-Soon Kwon
Keyword(s):  
Mine Drainage ◽  
Mine Waste ◽  
Point Of Zero Charge ◽  
Biological Oxidation ◽  
Indigenous Bacteria ◽  
Bacterial Adaptation ◽  
Valuable Metals ◽  
Initial Ph ◽  
Dominant Member ◽  
Corrosion Pits

The microbially mediated recovery of valuable metals contained in mining waste presents an economical alternative to conventional hydrometallurgical processes. In order to investigate the effect of bacterial adaptation and biological oxidation on bioleaching, the microbially mediated bioleaching of a pyrrhotite sample from mine waste, with indigenous bacteria existing in acid mine drainage, was studied. The indigenous bacteria were sub-cultured repeatedly for iron adaptation, and Acidithiobacillus ferrooxidans was identified as the dominant member of the microbial consortium. The point of zero charge (PZC) of pyrrhotite sampled from mine waste was determined as 3.0. The performance of bioleaching by contact and non-contact biological oxidation was compared by conducting bioleaching under different initial pH (pHini) conditions (2.8 and 3.2). Negatively charged bacteria could be attached onto the pyrrhotite, which has a positive surface charge at lower pHini (2.8) than the PZC (3.0). Bacteria attachment and corrosion pits on the surface of the pyrrhotite residues were observed at pHini of 2.8. Under bacteria-adapted conditions, the leaching concentration of Fe (44.2 mg/L) at pHini of 2.8 was 2.1 times greater than that (21.3 mg/L) at pHini of 3.2. Under non-adapted bacteria conditions, the extent of Fe leaching was not significantly different between the pHini of 2.8 and 3.2. This could be attributed to the fact that the adapted bacteria could more easily attach onto the pyrrhotite surfaces at pHini 2.8, allowing contact biological oxidation during the bioleaching experiments. We demonstrate here that the bioleaching of pyrrhotite could increase Fe recovery through bacterial adaptation and contact biological oxidation.

scholarly journals Dynamics of the rumor-spreading model with hesitation mechanism in heterogenous networks and bilingual environment

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Shuai Yang ◽  
Haijun Jiang ◽  
Cheng Hu ◽  
Juan Yu ◽  
Jiarong Li
Keyword(s):  
Lyapunov Method ◽  
Reproduction Number ◽  
Model Parameters ◽  
Rumor Spreading ◽  
Spreading Model ◽  
Reductio Ad Absurdum ◽  
The Stability ◽  
The Impact ◽  
Theoretical Results ◽  
The Basic Reproduction Number

Abstract In this paper, a novel rumor-spreading model is proposed under bilingual environment and heterogenous networks, which considers that exposures may be converted to spreaders or stiflers at a set rate. Firstly, the nonnegativity and boundedness of the solution for rumor-spreading model are proved by reductio ad absurdum. Secondly, both the basic reproduction number and the stability of the rumor-free equilibrium are systematically discussed. Whereafter, the global stability of rumor-prevailing equilibrium is explored by utilizing Lyapunov method and LaSalle’s invariance principle. Finally, the sensitivity analysis and the numerical simulation are respectively presented to analyze the impact of model parameters and illustrate the validity of theoretical results.

scholarly journals A Test of Two Methods for Waste Rock Drainage Quality Prediction: Aqua Regia Extraction and Single-addition Net-acid Generation Test Leachate Analysis

2021 ◽  
Author(s):  
Teemu Karlsson ◽  
Lena Alakangas ◽  
Päivi Kauppila ◽  
Marja Liisa Räisänen
Keyword(s):  
Mine Drainage ◽  
Mine Waste ◽  
Extraction Methods ◽  
Drainage Water ◽  
Waste Rock ◽  
Quality Prediction ◽  
Aqua Regia ◽  
Acid Generation ◽  
Leachate Analysis ◽  
Single Addition

AbstractThe mobility of contaminants from mine waste can be assessed using different extraction methods. Aqua regia (AR) extraction is the most commonly used method in Finland. Another method is the analysis of leachate from net acid generation (NAG) tests, which is primarily designed for acid production potential assessment. We investigated the performance of single-addition NAG test leachate analysis and AR extraction in drainage quality prediction, using waste rock and drainage water samples from several Finnish waste rock sites. Our objective was to improve interpretation of the AR and single-addition NAG test leachate analysis results in drainage quality prediction. The AR extraction effectively reflected elements that occurred in elevated concentrations in drainage water, though it over-predicted Al, As, Cd, Co, Cu, and Ni in some circumneutral drainages, and Cr in general. The single-addition NAG test leachate analysis also performed well in assessing the mobility of contaminants including Al and Cr at acid mine drainage sites. As the contaminants tend to precipitate in neutral NAG test solution, the usability of the method in neutral mine drainage cases should be further investigated. Furthermore, the conclusions presented in this study are limited to waste rock samples collected from the surface of piles; future work will examine waste rock history, dump cores, drainage quality changes, etc. in more detail.

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