Electrochemical Extraction Research Articles

Mass Transfer Coefficients in Electrochemical Membrane Process of Iron, Magnesium and Manganese Ions Extraction from Technological Solutions Complicated by Concentration Polarization

The article presents the results of a study of mass transfer in the process of electrochemical extraction of iron, magnesium and manganese ions from technological solutions. Mathematical expressions are obtained, and numerical values of empirical coefficients are determined for theoretical calculation of specific outflow, retention coefficient, and average mass transfer coefficients of the electrochemical membrane process of separation of technological solutions. The dependence of concentration polarization on solution flow rate, pressure gradient, and concentration is analyzed.

A multi-phase mesoscopic simulation model for the long-term chloride ingress and electrochemical chloride extraction

Electrochemical chloride extraction (ECE) is one of the effective methods to remove chloride and prolong the service life of reinforced concrete (RC) structures. To fully understand the mechanisms of the long-term chloride ingress and subsequent ECE treatment of RC structure, a multi-phase mesoscopic numerical model is proposed. Unlike most of existing models, the long-term chloride ingress and the effect of chloride binding are considered in the proposed model, and the transport of chloride is simulated through a novel diffusion-migration-reaction process. The numerical simulation results show that the adsorption capacity of concrete to chloride decreases with the increase of chloride ingress time. Interestingly, the free chloride concentration on the surface of concrete decreases dramatically, and the maximum value appears in the concrete protective cover after ECE treatment. Furthermore, ECE treatment time, current density and concrete protective cover have significant influences on ECE treatment efficiency. Besides, the quantitative relationship models between these factors and ECE treatment efficiency have been developed. Moreover, the use of stirrup can improve the efficiency of ECE treatment. The research outcomes reveal previously ignored fundamental aspects of the ECE treatment and provide insights for the durability prediction of RC structures.

Selective electrochemical extraction of copper from multi-metal e-waste leaching solution and its enhanced recovery mechanism

Recycling activity for waste electrical and electronic equipment is always accompanied with leaching solution containing copper. Its selective extraction is of environmental and economic significance, and is beneficial for subsequent resource purification procedure. Compared with techniques such as chemical precipitation and solvent extraction, potentiostatic electrodeposition is outstanding with the advantage of high selectivity, electron as clean reagent, and minimal chemical usage. However, key factors affecting copper electrodeposition behavior as well as its kinetic process remain unclear, which blocks its further application. In this study, selective copper electrochemical extraction from multi-metal leaching solution of waste liquid crystal display panels is explored. Copper electrodeposition is analyzed from electrochemical and mass transport point of view, and the main results are summarized: (i) copper can be first electrodeposited due to its higher reduction potential compared with indium; (ii) applied potential and agitation are the most influential factors towards space-time yield and current efficiency; (iii) a semi-empirical kinetic model could quantitatively describe the influence of agitation and the time-current-concentration relationship. The model-predicted extraction rate agreed well with experimental data throughout electrodeposition; (iv) electrodeposition experiments show over 95% of copper can be selectively extracted as ultrafine copper powder (~150 nm) at 0.05 V (vs. SHE).

A comparison of high voltage outgassing of LiCoO2, LiNiO2, and Li2MnO3 layered Li-ion cathode materials

One method of increasing the energy density of Li-ion batteries is to access reversible Li intercalation in conventional layered transition metal oxide cathode materials at high potentials (4.3–5 V vs. Li/Li+), and thus allow more electrochemical capacity per volume of active material. This comes at the cost of increased interfacial reactivity and often results in capacity fade over many cycles. Tracing gas evolution during electrochemical lithium extraction and insertion provides a useful strategy to understand this high voltage reactivity. In this study, we examine outgassing during Li extraction in well-known layered oxides (LiCoO2, LCO; LiNiO2, LNO; and Li2MnO3, LMO). We highlight key differences in the outgassing of each material. Whereas negligible O2 release is found in LCO and LNO, even with voltage holds at 5 V vs. Li/Li+, O2 release is found to account for a large portion of the electrochemical capacity and persists over many cycles in LMO. CO2 outgassing is observed to varying extents, following the trend of LMO ≈ LNO > LCO, and is due to a combination of residual solid carbonate oxidation and electrolyte degradation. Taken together, these results show the importance of quantitative analysis in understanding the role of transition metal composition on the chemistry of conventional Li-ion battery materials.

Development of electrochemical lithium extraction based on a rocking chair system of LiMn2O4/Li1-xMn2O4: Self-driven plus external voltage driven

Selective electrosorption based on a rocking-chair system of LiMn2O4/Li1-xMn2O4 is a promising lithium extraction technology, which has the high efficiency of the lithium extraction process and the low cost of the electrode equipment. However, the energy consumption of the lithium extraction process and the selectivity of the electrode to Li+ need to be further optimized. In this work, the potential difference between the electrodes with different compositions of Li+ cubic sub-lattice was concerned and tried to be used. The lithium extraction process with single external voltage driven was transformed into a coupling process of “self-driven” plus “external voltage driven”. In the self-driven process, the Li+ extraction capacity reached more than 50% of the whole lithium extraction process. The coupling process reduced the specific energy consumption by more than 50% and improved the Li+ selectivity. With the optimized “self-driven” time of 1.0 h and applied voltage of 0.6 V, the lithium extraction process with “self-driven” process can achieve a lithium extraction capacity higher than 37 mg·g−1 within 2 h, a specific energy consumption lower than 7.63 Wh·mol−1. The molar ratio of Mg2+/Li+ reduced more than 1000 times (from 20 to 0.018). The coupling process shows great development potential in the lithium extraction with low energy consumption, highly Li+ selectivity and environment-friendly.

Production and extraction of medium chain carboxylic acids at a semi-pilot scale

Abstract Microbial chain elongation enables the conversion of organic wastes and agroindustrial sidestreams into medium chain carboxylic acids (MCCAs), with application in the production of plasticizers, personal care products, functional feed additives, and fuels. This work describes the up-scaling of the production of MCCAs from thin stillage, and their separation into an oil at kilogram scale with a MCCA content of more than 72%. The chain elongation occurred at a maximum rate of 1.7 ± 0.6 g MCCA L−1 d−1 without the use of ethanol as electron donor, even when it was supplied. Two in-line extraction trains are compared: (1) solvent extraction based on pertraction followed by electrochemical phase separation of the acids through a 2-compartment membrane electrolysis (ME) cell, and (2) direct electrochemical extraction from the fermentation broth using a 3-compartment ME cell. Using the first treatment train, n-caproic acid was extracted at an efficiency of 73%. The decrease in the fermentation pH from 5.5 to 5.0 enabled doubling the MCCA and oil production rate without a concomitant increase in NaOH dosage for pH stabilization. The selectivity brought about by pertraction and its capacity to up-concentrate MCCAs in an alkaline-pH extract enabled a more efficient use of the electricity for ME (as low as 6.2 kWh kg−1 oil) when compared to a period when ME was applied directly to the filtered fermentation broth (160 kWh kg−1 oil). The 3-compartment ME cell was able to phase separate oil extracting directly from the fermentation broth but it was not selective for longer-chain carboxylic acids due to co-extraction of short chain carboxylic acids and inorganic anions.

(Invited) Electrochemical Extraction and Conversion of CO2 from Seawater

Capture and conversion of CO2 from anthropogenic emission is becoming an increasingly important social responsibility as the concentration of atmospheric CO2 continues to rise above record high levels. To achieve carbon negative conditions in the long term, capture and extraction of CO2 directly from air and seawater will likely play a much bigger role. The concentration of the present CO2 in the atmosphere is ~400 ppm, or 0.00079 kg m−3. As a result, a large volume of air needs to be processed in direct air capture processes. In contrast, world ocean constitutes the largest carbon sink, absorbing about 40% of anthropogenic CO2 since the beginning of industrial era with an effective CO2 concentration of 2.1 mmol kg−1, or 0.095 kg m−3 in seawater, which is a factor of 120 times larger than in the atmosphere. Thus, extraction of CO2 from seawater provides an alternative and unique approach in the global carbon removal technological landscape.Herein, a new bipolar membrane electrodialysis (BPMED) cell design, in which the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the electrodes were replaced with reversible redox couple reactions with minimal thermodynamic and kinetic voltage losses, was designed, constructed and evaluated. At an operating current density of 3.3 mA cm−2, and a seawater flow rate of 37 ml min−1, a record low electrochemical energy consumption of 155.4 kJ mol−1 or 0.98 kWh kg−1 of CO2 was achieved. The demonstrated BPMED cell also exhibited a high CO2 extraction efficiency of 71% of total dissolved inorganic carbon (DIC). We also demonstrated, for the first time, the direct coupling between the CO2 extraction from seawater via BPMED and electrochemical CO2 reduction (CO2R) into fuels and chemicals. The outlet CO2 stream from the BPMED was fed into tandem custom-built vapor-fed GDE cells to first perform the oxygen reduction reaction (ORR) using a nanoparticle Ag-based catalyst followed by CO2R using Cu or Ag as the electrocatalyst. This configuration allowed us to convert CO2 from seawater to fuels and valuable chemicals such as carbon monoxide, ethylene, ethanol, and propanol with total Faradaic efficiency (FE) of up to 73% at current densities of 58 mA cm−2 using CO2R Cu electrocatalyst and to carbon monoxide with selectivity of up to 95% at current densities of 11.15 mA cm−2 using CO2R Ag electrocatalyst. Figure 1

(Invited) Study of Mechanical Behaviour of Si Anode upon Electrochemical Lithium Insertion

A battery is one of the representative electrochemical systems studied widely for energy storage applications. In particular, Li-ion batteries are becoming an essential component in mobile electronic devices and electric vehicles, as smaller, lighter, and longer energy storage is required. Silicon is considered as one of the most promising anode materials for Li-ion batteries because of its exceptional specific capacity, which is about ten times that of commercial graphite anodes. However, conventional Si anodes typically suffer from rapid capacity decay due to mechanical fracture caused by large volume changes (300%) during repeated electrochemical lithium insertion and extraction. It this talk, I will present the mechanical behaviour of various structure of single crystalline Si nanopillar upon electrochemical lithiation. Single crystalline Si nanopillar array fabricated by top-down process provides well defined dimension and crystalline orientation. The study of lithiated Si nanopillar exhibited interesting phenomena such as anisotropic expansion, size dependency of mechanical fracture, and temperature dependency [1-4]. Single crystalline Si plate various bending behaviour for the crystalline orientation and its large fracture resistance [5]. These studies will provide better understanding of mechanical behaviour of lithited Si anode for design of robust Si anode electrode. Acknowledgement The contents in this paper were published in references [1-5].

(Invited) Oxygen Defects in Oxide-Based Lithium Ion Battery Cathodes: Formation and Influences on Electrochemical Properties

IntroductionDemands on high energy density batteries increase to exploit renewable energies efficiently and develop zero-emission vehicles [1]. Among technological issues for next-generation batteries, we focus on the development of cathode active materials. So far, oxide-based cathode materials have been used in lithium ion batteries because of their excellent electrochemical properties. However, the formation of oxygen defects like oxygen vacancy is inevitable in oxides. There are two important motivations for the study of oxygen defect formation in oxide-based cathodes, one is the safety of batteries and the other is the battery performance. For the safety, it was reported that the reaction between organic liquid electrolytes and released oxygen from oxide-based cathodes is exothermic and cause abnormal heat generation [2]. To prevent catastrophic thermal runaway of battery systems, understanding oxygen release mechanism is important. For the influence on battery performance, it was reported that preliminary reduction treatments for Li-rich cathodes improved capacity, rate capability and capacity retention [3]. To establish the guideline for the oxygen defect engineering for advanced battery materials, it is necessary to understand influences of oxygen defects on electrochemical properties. In the presentation, oxygen vacancy formation behavior in oxide-based cathodes and influences of oxygen vacancy on battery performances are discussed.ExperimentalLi1.2Mn0.6Ni0.2O2 and Li1.2Ni0.13Co0.13Mn0.54O2 were synthesized by solid state reaction of carbonate precursors and LiOH·H2O. The oxygen vacancy formation was evaluated by thermogravimetry and the coulometric titration using yttria stabilized zirconia. The absolute oxygen content of the sample was determined by iodometric titration. Samples with different oxygen vacancy concentration were also prepared by the coulometric titration method. Influences of oxygen vacancy on crystal and electronic structures were evaluated by X-ray diffraction (XRD) and soft X-ray absorption spectroscopy (XAS). Charge/discharge measurements were performed on the pristine and the oxygen-deficient cathodes.Results and discussionFigure 1 shows the variation of the oxygen content in Li1.2Mn0.6Ni0.2O2 and Li1.2Ni0.13Co0.13Mn0.54O2. In the figure, the vertical axis, O/M, represents the molar ratio of oxygen in and metal components (Li, Ni, Co and Mn) in the target material, meaning that O/M = 1 represents the oxygen stoichiometric composition for Li1.2Mn0.6Ni0.2O2 and Li1.2Ni0.13Co0.13Mn0.54O2, and the horizontal axis represents the equilibrium P(O2) for each oxygen content. With decreasing O/M, P(O2) decreased and reached a constant value regardless of the relative oxygen content. The oxygen nonstoichiometric data in Figure 1 can be roughly classified into two regions depending on the slope of the curve. In the higher P(O2) region where the O/M vs. log P(O2) curve showed a certain slope, meaning both oxygen content and P(O2) changes simultaneously. In the lower P(O2) region, on the other hand, P(O2) is almost invariant regardless of O/M. The high P(O2) region is the oxygen deficient nonstoichiometry region where the oxygen vacancies were randomly distributed in the oxide-based cathodes. On the contrary, the low P(O2) region is the multiphase co-existing region where the sample is decomposed by the electrochemical oxygen extraction and co-exist with the decomposition phases. In this case, the equilibrium P(O2) is fixed with that of the multiphase co-existing state regardless of apparent O/M. The reduction stability of Li1.2Mn0.6Ni0.2O2 and Li1.2Ni0.13Co0.13Mn0.54O2 were also confirmed by XRD. The reduction stability limit of Li1.2Mn0.6Ni0.2O2 and Li1.2Ni0.13Co0.13Mn0.54O2 were log(P(O2)/bar) = -17.7 and -20.7, respectively. From these evaluations, it can be concluded that Li1.2Mn0.6Ni0.2O2 and Li1.2Ni0.13Co0.13Mn0.54O2 can accept oxygen vacancy up to about 2 mol% and about 3 mol%, respectively. The results of XRD, XAS and battery tests will be shown in the presentation, and influences of oxygen defects on crystal and electronic structures and electrochemical performance will be discussed.

A Technical Proton Pump for Industrial Biotechnology: Electrochemical pH-Swing Extraction of Succinic Acid

Industrial biotechnology established new routes for sustainable production of platform chemicals.[1] Succinic acid is a versatile building block for bio-based polymers and solvents.[2] Despite the progress made in up-stream development separation and product purification still account for up to 40% of total production costs.[3] The high separation costs originate from a mismatch between the optimal pH for fermentation and product recovery. While most bio-catalysts work best at neutral pH, acidic pH is advantageous for product recovery.[4] However, pH control by inorganic bases and acids comes with the drawback of producing large amounts of inorganic salt waste like gypsum.[5] Electrochemical separation methods have the potential to overcome the unsustainable production of salt waste and are thus regarded a more environmentally benign separation technology.[6] The integration of electrochemical separation methods showed great potential for overcoming the mismatch between fermentation pH and pH required for separation. With promising results reported for electrochemical unit operations applied for waste free product recovery from fermentation [7] integration of electrochemical unit operations into a complete downstream process sequence should be the next objective. [8]We recently proposed an electrochemical downstream concept applying electrochemical pH-swing extraction for the recovery of succinic acid from pH-neutral aqueous solutions followed by another pH-swing step for product stripping from the extractant and eventual product recovery by direct electrochemical pH-shift crystallization.[9,10] Thereby, generation of spatially separated regions of acidic and alkaline pH by water electrolysis is utilized to generate the pH-dependent driving force for reactive extraction of succinic acid by tri-n-octylamine. The acidic pH shifts the aqueous acid-base equilibrium towards the protonated succinic acid, which is then available for extraction.[4] Hydroxide ions simultaneously produced at the cathode create an alkaline catholyte, which can be used for pH control in succinic acid fermentation. The water electrolysis coupled to liquid-liquid extraction creates an integrated buffer-recycle between fermentation and product separation and overcomes the need for adding inorganic acids and bases for pH-control. In a second electrochemical pH-swing cell the alkaline solution produced by the cathodic reaction of a water electrolysis cell is used to strip the acid from the loaded extractant producing an aqueous solution with high succinic acid concentration. The anodic reaction of this second cell is eventually used to crystallize succinic acid from this mother liquor by the electrochemical pH-shift.[9] Recovery of solid succinic acid was achieved by a downstream process constituted of four electrochemical processing steps synergistically integrated into two electrochemical cells which did not require energy intensive evaporation of water.This contribution gives insights into experimental examples for succinic acid recovery via the proposed separation process and discusses opportunities for the design of membrane free cells, as separation selectivity is solely determined by liquid-liquid extraction. In extension to previous work [11] the dynamic modeling approach for electrochemical pH-swing electrolysis was extended to account for concentration dependent increase of ohmic losses and pH-dependent proton cross-over. The new model is used to identify good operational conditions with high current efficiencies. The model results are compared to experimental data recorded in a 100cm² electrolysis cell coupled to a lab-scale extraction column.

(Invited) Lessons Learnt and Challenges Ahead the Development of Ca-Based Batteries

The aim to develop batteries based in multivalent metal anodes has recently reemerged as part of the worldwide quest for new energy storage technologies with high energy density. Indeed, figures of merit attainable at the cell level computed using simple models indicate that the theoretical energy densities could easily top the state-of-the-art Li-ion, with costs being potentially much lower.The viability of a rechargeable technology based on calcium has only been considered recently, after reversible plating/stripping in organic electrolytes was achieved. In the quest for suitable positive electrode materials for multivalent ions, both traditional intercalation hosts, such as TiS2 or V2O5, and alternative materials have been investigated. While V2O5 has so far attracted most attention, the interpretation of results is controversial, as changes in the diffraction pattern upon reduction might be related to the presence of water/protons in the electrolyte. Electrochemical extraction of calcium in Ca3Co2O6 is feasible but the only compound for which reversible electrochemical calcium insertion/extraction has reliably been shown to date is TiS2, despite the process being complex and non-practically viable as a result of solvent co-intercalation and high cell overpotential.Overall, there is a long and winding road to follow before reliable proof-of-concept can be achieved and technological prospects evaluated. Development of reliable experimental setups, including reference and counter electrodes, coupled to complementary characterization techniques, as well as computational tools, is mandatory if steady progress is to be achieved. Figure 1

The efficiency of chloride extraction using un-galvanized steel anode

Electro-chemical Chloride Extraction (ECE) is considered one of the most effective techniques used to extract chloride ions from reinforced concrete structures. The effectiveness of using ECE depends on some important factors such as anode type, current intensity, extraction duration, type of rebar, and chemical properties of concrete. On the other hand, ECE may cause some detrimental effects on some mechanical properties of concrete and steel such as a reduction in bond and compressive strengths of concrete, and embrittlement (i.e. reduction in ductility) ductility of reinforcing steel. The major aim of this research work was to investigate the effectiveness of ECE using locally available un-galvanized steel mesh with conductive cement paste anode as a new type of anode on a reinforced concrete slab as a structural element. The slab behavior before and after ECE was studied by determining compressive strength, water absorption rate, concrete chloride content, and steel corrosion potential. The slab behavior was studied taking into consideration the established steel arrangement with spacing 20 cm between re-bars. The effect of initial chloride content on chloride extraction efficiency was investigated. Effectiveness of ECE with small initial chloride content 0.4% and 0.8% was compared with that of high initial chloride content 2.5% to know whether the initial chloride content is an important factor in ECE effectiveness or not.

Progress in electrochemical lithium ion pumping for lithium recovery

This review provides a systematic summary of electrochemical lithium ion pumping (ELIP) for lithium recovery, aiming at helping to understand the working mechanism of ELIP and guiding the design of advanced electrochemical Li recovery devices. Accelerating the development of lithium resources has attracted a great deal of attention with the explosive growth of new energy vehicles. As a new technology, electrochemical lithium ion pumping (ELIP) is featured by environment–friendly, low energy consumption and high efficiency. This review summarizes the research progress in ELIP, and focuses on the evaluation methods, electrode materials and electrochemical systems of ELIP. It can be concluded that ELIP is expected to achieve an industrial application and has a promising prospect. In addition, challenges and perspective of electrochemical lithium extraction are also highlighted.

Liquid Al assisted electrochemical extraction of lanthanum by formation of Al11La3 in chloride melts

In this work, different electrochemical measurements were employed to investigate the electrochemical behavior of La(III) on W and liquid aluminum electrodes, respectively. In LiCl–KCl melts, the diffusion coefficients of La(III) on W electrode at different experimental temperatures were determined by chronopotentiometry. The cyclic voltammetry results obtained on liquid aluminum electrode revealed only one pair of redox signal corresponding to the formation of Al–La intermetallic compound in LiCl–KCl–LaCl3 melts. The diffusion coefficient of La atom on the liquid Al–La alloy electrode was evaluated by anodic chronopotentiometry at 973 K. The electrochemical extraction of La was realized by galvanostatic electrolysis on a liquid aluminum electrode in LiCl–KCl–LaCl3 melts at 973 K, and the phases of Al11La3 and Al were identified by XRD. The SEM images disclosed needlelike precipitates in alloy, and the element La mainly distribute in the needlelike precipitates. After electrolysis, the extraction efficiency of element La was evaluated to be 99.4%, indicates that the electrochemical extraction of lanthanum with the help of liquid aluminum cathode is feasible in practice.

Electrolytic alloy-type anodes for metal-ion batteries

Alloy-type metals/alloys hold the promise of increasing the energy density of metal-ion batteries (MIBs) because of their theoretical high gravimetrical capacities. Semimetals and semimetal-analogs are typical alloy-type anodes. Currently, the large-scale extraction of semimetals (Si, Ge) and semimetal-analogs (Sb, Bi, Sn) by traditional metallurgical routes highly relies on using reducing agents (e.g., carbon, hydrogen, reactive metals), which consumes a large number of fossil fuels and produces greenhouse gas emissions. In addition, the common metallurgical methods for extracting semimetals involve relatively high operating temperatures and therefore produce bulk metal ingots solidified from the liquid metals. However, the commonly used electrode materials in batteries are fine powders. Thus, directly producing semimetal powders would be more energy efficient. In addition, semimetals are good candidates to host alkali/alkaline-earth ions through the alloying process because the electronegativity of semimetals is high. Therefore, preparing semimetal powders via an environment-sound manner is of great interest to provide sustainable anode materials for MIBs while reducing the ecological footprint. Low-cost and high-output capacity anode powder materials, as well as straightforward and environmental-benign synthetic methods, play key roles in enabling the energy conversion and storage technologies for real applications of MIBs. Electrochemical technologies offer new strategies to extract semimetals using electrons as the reducing agent that comes from renewable energies. Besides, the morphologies and structures of the electrolytic products can be rationally tailored by tuning the electrode potentials, electrolytes, and operating temperatures. In this regard, using the one-step green electrochemical method to prepare high-capacity and cheaper alloy-type metalloids for MIB anodes can fulfill the requirements for developing MIBs. This review critically overviews recent developments and advances in the electrochemical extraction of semimetals (Si, Ge) and semimetal-analogs (Sb, Bi, Sn) for MIBs, including basic electrochemical principles, thermodynamic analysis, manufacture strategies and applications in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), potassium-ion batteries (PIBs), magnesium-ion batteries (Mg-ion batteries), and liquid metal batteries (LMBs). It also presents challenges and prospects of employing electrochemical approaches for preparing alloy-type anode materials directly from inexpensive ore-originated feedstocks.

Electrochemical extraction of palladium from spent heterogeneous catalysts of a petrochemical unit using the leaching and flat plate graphite electrodes

In this study, electrometallurgy recovery of Pd from the spent petrochemical unit Pd/Al2O3 catalyst has been reported. The electrochemical deposition of Pd from the acid solution (HCl/H2O2) was developed using flat plate graphite electrodes. The effect of the operating variables was assessed and optimized by employing the central composite design of the response surface methodology. The recovery efficiency of Pd was obtained 99.07% at the optimum condition of, reaction temperature of 67.0 °C, electrolysis time of 3.4 h, liquid/solid ratio of 24.7 ml/g, a current density of 196 A/m2 and stirring speed of 572 rpm. The results of the statistical analysis indicated that the anticipated data were in good suitable with the observed ones (R2 = 0.9762), in which the average deviation from experimental data was 0.32% for optimum condition. It indicates that the deposited Pd has spherical nanoparticles shape with a purity of 94.02%. The present study can provide a reliable process for extraction of Pd from the solid waste by the high efficiency and purity.

Effect of silica fume and fly ash on the stability of bound chlorides in cement mortar during electrochemical chloride extraction

This study investigated the stability of bound chloride ions in the cement mortars incorporating supplementary cementitious materials (SCM) during the electrochemical chloride extraction (ECE) process. The effect of the replacing ratio of fly ash (FA) and silica fume (SF) and sulfate concentration on the chloride binding and distribution after ECE treatment was studied using water and acid-soluble methods, X-ray diffraction (XRD) analysis and thermogravimetric analysis (TGA). The results showed that the concentration of the bound chlorides in the SCM incorporated cement mortars depended heavily on the content of Al2O3 and the pH of the pore solution. Without ECE treatment, an increase in the FA content increased the concentration of bound chlorides while the addition of SF significantly decreased the chloride binding capacity. During ECE treatment, however, the stability of bound chlorides declined with increasing the FA content but increased with increasing the SF content under an electric field. It was also found that the presence of sulfate ions reduced the content of the chemically bound chlorides residing in Friedel’s salts (FS) but had a negligible influence on the physically bound chlorides absorbed by calcium silicate hydrate (C-S-H gel).

Fundamental Analysis for Electrochemical Extraction and Monitoring of Impurities from Lead Lithium and Lithium with Chloride Molten Salt

Liquid Li-Pb eutectic alloy and lithium, assumed to be used in a liquid blanket system for fusion reactors, can easily contain light element impurities. It is thought that these impurities have bad influences on compatibility with structural materials. However, an effective reducing method for impurities has not yet been established. In this work, an electrochemical method is focused on this application. The experimental results of our work suggest the transfer of hydrogen and nitrogen impurities. From the results, a possible way to remove the impurities by electrochemical method is shown.

Efficiency of ECE Applied on RC Slab using Locally Available Un-Galvanized Steel with Conductive Cement Paste Anode

Electro-chemical Chloride Extraction (ECE) is considered one of the most effective technique used to extract chloride ions from reinforced concrete structures. Effectiveness of using ECE depends on some important factors such as anode type, current intensity, extraction duration, type of rebar and chemical properties of concrete. On the other hand, ECE may cause some detrimental effects on some mechanical properties of concrete and steel such as a reduction in bond and compressive strengths of concrete, and embrittlement (i.e. reduction in ductility) ductility of reinforcing steel. The major aim of this research work was to investigate the effectiveness of ECE using locally available un-galvanized steel mesh with conductive cement paste anode as a new type of anode on a reinforced concrete slab as a structural element. The slab behavior before and after ECE was studied by determining compressive strength, water absorption rate, concrete chloride content and steel corrosion potential. The slab behavior was studied taken into consideration the established steel arrangement with spacing 20 cm between re-bars. Another aim of this research work was to investigate the effect of initial chloride content on chloride extraction efficiency by applying optimum current intensity and duration (3 A/m2 and 6 weeks) on cylinders with pure chloride content 0.4% and 0.8% (by weight of cement). Effectiveness of ECE with small initial chloride content 0.4% and 0.8% was compared with that of high initial chloride content (2.5%) in order to know if the initial chloride content is an important factor on ECE effectiveness or not.

Coupling electrochemical ammonia extraction and cultivation of methane oxidizing bacteria for production of microbial protein

Conventional treatment of residual resources relies on nutrient removal to limit pollution. Recently, nutrient recovery technologies have been proposed as more environmentally and energetically efficient strategies. Nevertheless, the upcycling of recovered resources is typically limited by their quality or purity. Specifically, nitrogen extracted from residual streams, such as anaerobic digestion (AD) effluents and wastewaters, could support microbial protein production. In this context, this study was performed as a proof-of-concept to combine nitrogen recovery via electrochemical reactors with the production of high quality microbial protein via cultivation of methanotrophs. Two types of AD effluents, i.e., cattle manure and organic fraction of municipal solid waste, and urine were tested to investigate the nitrogen extraction efficiency. The results showed that 31–51% of the nitrogen could be recovered free of trace chemicals from residual streams depending on the substrate and voltage used. Based on the results achieved, higher nitrogen concentration in the residual streams resulted in higher nitrogen flux between anodic and cathodic chambers. Results showed that the extraction process has an energy demand of 9.97 (±0.7) - 14.44 (±1.19) kWh/kg-N, depending on the substrate and operating conditions. Furthermore, a mixed-culture of methanotrophic bacteria could grow well with the extracted nitrogen producing a total dry weight of 0.49 ± 0.01 g/L. Produced biomass contained a wide range of essential amino acids making it comparable with conventional protein sources.