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Mahmoud A.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Cezac P.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Hoadley A.F.A.,Monash University | Contamine F.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | D'Hugues P.,Bureau de Recherches Géologiques et Minières
International Biodeterioration and Biodegradation | Year: 2016

Compared to conventional extractive techniques, bacterial assisted leaching, also called "biomining" is an eco-friendly technology that provides improved metal/solid separations. These separations are enhanced by the synergistic activities of astonishingly diverse groups of microorganisms, which lead to an extraction process with low energy consumption, low capital investment and low impact on the environment. Recently, biomining has received great attention in a variety of niche areas, especially in the mineral industries and solid industrial waste materials (e.g. galvanic sludge, sewage sludge, fly ash, electronic waste, spent petrochemical catalysts, medical waste, spent batteries, waste slag) where the metals values are low, or where the presence of certain elements would lead to smelter damage, or where environmental considerations favor biological treatments options. It allows the recovery of metal from low-grade sulfide ores and concentrates that cannot be processed economically by conventional techniques, as well as the production of concentrated metal salt solutions, which could be recycled. Bacterial assisted leaching processes are based on the ability of certain microorganisms to solubilize/or expose the metals contained in the ores and concentrates by direct oxidation, or through indirect chemical oxidation instigated by the corrosive metabolic by-products generated by an electrochemical option, or a combination of both of these. The valuable metals in solution can be recovered using conventional hydrometallurgical techniques. If the material of interest constitutes part of or is in the pre-treated residue then it can be further processed for metal recovery.The majority of microorganisms involved in bacterial assisted leaching processes are chemolithotrophs. Carbon dioxide (CO2) and oxygen (O2) are essential nutrients that are used by microorganisms for their growth, maintenance, metabolite production, and survival.This literature review aims to provide a fundamental understanding of the various mechanisms involved in microbial leaching of sulfide minerals and provide a brief look at the various factors affecting this process. Special attention is focused on the mass transfer rates in the gas phase and how they exert a pivotal role in microbially assisted leaching of sulfide minerals. Also reviewed are the major parameters that can affect gas phase mass transfer, with particular emphasis on how it is related to the efficiency of bacterial assisted leaching. © 2016 Elsevier Ltd.


Mahmoud A.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Olivier J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Vaxelaire J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Hoadley A.F.A.,Monash University
Water Research | Year: 2011

Electric field-assisted dewatering, also called electro-dewatering (EDW), is a technology in which a conventional dewatering mechanism such a pressure dewatering is combined with electrokinetic effects to realize an improved liquid/solids separation, to increase the final dry solids content and to accelerate the dewatering process with low energy consumption compared to thermal drying. The application of these additional fields can be applied to either or both dewatering stages (filtration and/or compression), or as a pre-or post-treatment of the dewatering process. In this study, the performance of the EDW on wastewater sludge was investigated. Experiments were carried out on a laboratory filtration/compression cell, provided with electrodes, in order to apply an electrical field. The chosen operating conditions pressure (200-1200 kPa) and voltage (10-50 V) are sufficient to remove a significant proportion of the water that cannot be removed using mechanical dewatering technologies alone. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of EDW on (i) the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of EDW and (ii) the energy consumption calculated for each additional mass of water removed. A two-factor central composite design was used to establish the optimum conditions for the EDW of wastewater sludge. Experiments showed that the use of an electric field combined with mechanical compression requires less than 10 and 25% of the theoretical thermal drying energy for the low and moderate voltages cases, respectively. © 2011.


Mahmoud A.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Hoadley A.F.A.,Monash University | Conrardy J.-B.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Olivier J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Vaxelaire J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Water Research | Year: 2016

Electrically assisted mechanical dewatering, known as electro-dewatering (EDW), is an alternative emerging technology for energy-efficient liquid/solids separation in the dewatering of wastewater sludge. In this study, the performance of the electro-dewatering (EDW) process for activated wastewater sludge was investigated. The influence of the operating modes; being the timing of voltage (U-EDW) or current (I-EDW) application to either or both the filtration and compression stages, and the influence of the applied pressure (in successive 30 min pressure steps) were studied. The results showed that by delaying the application of the electric field to the filter cake compression stage, there was a potential saving in power consumption of around 10–12% in the case of U-EDW and about 30–46% in the case of I-EDW. The increase of the applied pressure from 0.5 to 12 bar during the filter cake compression stage leads to an increase in electro-dewatering kinetics. The results also reveal that at a low electric field level the increase of the processing pressure has a relatively pronounced effect on the dewatering process. At high levels of the electric field, a minimum processing pressure (4–6 bar) is required to improve the electrical contact between the electrode and the sludge and thus lower the energy consumption. © 2016 Elsevier Ltd


Mahmoud A.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Hoadley A.F.A.,Monash University
Water Research | Year: 2012

Hybrid ion exchange electrodialysis, also called electrodeionization (IXED), is a technology in which a conventional ion exchange (IX) is combined with electrodialysis (ED) to intensify mass transfer and to increase the limiting current density and therefore to carry out the treatment process more effectively. It allows the purification of metal-containing waters, as well as the production of concentrated metal salt solutions, which could be recycled. The objective of this paper was to investigate the ability of the IXED technique for the treatment of acidified copper sulphate solutions simulating rinsing water of copper plating lines. A single-stage IXED process at lab-scale with a small bed of ion exchanger resin with a uniform composition was evaluated, and the treatment performance of the process was thoroughly investigated. The IXED stack was assembled as a bed layered with the ion exchanger resin (strong acid cation-exchange Dowex™) and inert materials. The stack configuration was designed to prevent a non-uniform distribution of the current in the bed and to allow faster establishment of steady-state in the cell for IXED operation. The influence of operating conditions (e.g. ion exchanger resin with a cross-linking degree from 2 to 8% DVB, and current density) on IXED performance was examined. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of IXED on (i) the abatement yield of the metal cation, which is a fundamental purification parameter and an excellent indicator of the extent of IXED, (ii) the current yield or the efficiency of copper transport induced by the electrical field and (iii) the energy consumption. The experimental results showed that the performance at steady-state of the IXED operation with a layered bed remained modest, because of the small dimension of the bed and notably the current efficiency varied from 25 to 47% depending on the conditions applied. The feasibility of using the IXED in operations for removal of heavy metals from moderately dilute rinsing waters was successfully demonstrated. © 2012 Elsevier Ltd.


Conrardy J.-B.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Vaxelaire J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Olivier J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Water Research | Year: 2016

The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake + filter cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%. The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the filter cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive filter, such as metallic cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction). © 2016 Elsevier Ltd.


PubMed | Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Type: Journal Article | Journal: Water research | Year: 2011

Electric field-assisted dewatering, also called electro-dewatering (EDW), is a technology in which a conventional dewatering mechanism such a pressure dewatering is combined with electrokinetic effects to realize an improved liquid/solids separation, to increase the final dry solids content and to accelerate the dewatering process with low energy consumption compared to thermal drying. The application of these additional fields can be applied to either or both dewatering stages (filtration and/or compression), or as a pre-or post-treatment of the dewatering process. In this study, the performance of the EDW on wastewater sludge was investigated. Experiments were carried out on a laboratory filtration/compression cell, provided with electrodes, in order to apply an electrical field. The chosen operating conditions pressure (200-1200 kPa) and voltage (10-50 V) are sufficient to remove a significant proportion of the water that cannot be removed using mechanical dewatering technologies alone. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of EDW on (i) the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of EDW and (ii) the energy consumption calculated for each additional mass of water removed. A two-factor central composite design was used to establish the optimum conditions for the EDW of wastewater sludge. Experiments showed that the use of an electric field combined with mechanical compression requires less than 10 and 25% of the theoretical thermal drying energy for the low and moderate voltages cases, respectively.


Olivier J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Conrardy J.-B.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Mahmoud A.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932 | Vaxelaire J.,Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Water Research | Year: 2015

Compared to conventional dewatering techniques, electrical assisted mechanical dewatering, also called electro-dewatering (EDW) is an alternative and an effective technology for the dewatering of sewage sludge with low energy consumption. The objectives of this study were to evaluate the dewatering performance and to determine the influence of the process parameters (e.g. applied electric current, applied voltage, and the initial amount of dry solids) on the kinetics of EDW-process for activated urban sludge. Also significant efforts have been devoted herein to provide comprehensive information about the EDW mechanisms and to understand the relationship between these operating conditions with regards to develop a qualitative and quantitative understanding model of the electro-dewatering process and then produce a robust design methodology. The results showed a very strong correlation between the applied electric current and the filtrate flow rate and consequently the electro-dewatering kinetics. A higher applied electric current leads to faster EDW kinetics and a higher final dry solids content. In contrast, the results of this work showed a significant enhancement of the dewatering kinetics by decreasing the mass of the dry solids introduced into the cell (commonly known as the sludge loading). © 2015 Elsevier Ltd.


PubMed | Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Type: Evaluation Studies | Journal: Water research | Year: 2012

Hybrid ion exchange electrodialysis, also called electrodeionization (IXED), is a technology in which a conventional ion exchange (IX) is combined with electrodialysis (ED) to intensify mass transfer and to increase the limiting current density and therefore to carry out the treatment process more effectively. It allows the purification of metal-containing waters, as well as the production of concentrated metal salt solutions, which could be recycled. The objective of this paper was to investigate the ability of the IXED technique for the treatment of acidified copper sulphate solutions simulating rinsing water of copper plating lines. A single-stage IXED process at lab-scale with a small bed of ion exchanger resin with a uniform composition was evaluated, and the treatment performance of the process was thoroughly investigated. The IXED stack was assembled as a bed layered with the ion exchanger resin (strong acid cation-exchange Dowex) and inert materials. The stack configuration was designed to prevent a non-uniform distribution of the current in the bed and to allow faster establishment of steady-state in the cell for IXED operation. The influence of operating conditions (e.g. ion exchanger resin with a cross-linking degree from 2 to 8% DVB, and current density) on IXED performance was examined. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of IXED on (i) the abatement yield of the metal cation, which is a fundamental purification parameter and an excellent indicator of the extent of IXED, (ii) the current yield or the efficiency of copper transport induced by the electrical field and (iii) the energy consumption. The experimental results showed that the performance at steady-state of the IXED operation with a layered bed remained modest, because of the small dimension of the bed and notably the current efficiency varied from 25 to 47% depending on the conditions applied. The feasibility of using the IXED in operations for removal of heavy metals from moderately dilute rinsing waters was successfully demonstrated.


PubMed | Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Type: | Journal: Water research | Year: 2016

The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake+filter cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%.The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the filter cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive filter, such as metallic cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction).


PubMed | Laboratoire Of Thermique Energetique Et Procedes Ead 1932
Type: | Journal: Water research | Year: 2015

Compared to conventional dewatering techniques, electrical assisted mechanical dewatering, also called electro-dewatering (EDW) is an alternative and an effective technology for the dewatering of sewage sludge with low energy consumption. The objectives of this study were to evaluate the dewatering performance and to determine the influence of the process parameters (e.g. applied electric current, applied voltage, and the initial amount of dry solids) on the kinetics of EDW-process for activated urban sludge. Also significant efforts have been devoted herein to provide comprehensive information about the EDW mechanisms and to understand the relationship between these operating conditions with regards to develop a qualitative and quantitative understanding model of the electro-dewatering process and then produce a robust design methodology. The results showed a very strong correlation between the applied electric current and the filtrate flow rate and consequently the electro-dewatering kinetics. A higher applied electric current leads to faster EDW kinetics and a higher final dry solids content. In contrast, the results of this work showed a significant enhancement of the dewatering kinetics by decreasing the mass of the dry solids introduced into the cell (commonly known as the sludge loading).

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