Use Of Critical Raw Materials Research Articles

Identification of the environmental hotspots of a recycling process - Case study of a Pt PEMFC catalyst closed-loop recycling system evaluated via life cycle assessment methodology

Proton-exchange membrane fuel cell (PEMFC) technology using green H2 as a fuel to produce decarbonized electricity is considered as a promising substitute for fossil fuels. However, its development is impeded by the use of critical raw materials, such as platinum which catalyzes the hydrogen oxidation and oxygen reduction reactions. In this paper, a novel closed-loop system for the re-manufacturing of platinum-based catalyst electrode from recycled material is developed. Three different recycling alternatives are compared using the life cycle assessment (LCA) methodology. The most promising one, which combines the extraction step with an innovative synthesis of recycled Pt/C catalyst, leads to the manufacturing of an electrochemically active Pt/C catalyst with a high recovery efficiency of 96 %. Sensitivity analyses display that the recycling processes significantly relieve the environmental burdens associated with platinum mining and that their efficiencies directly relate to a decrease in environmental impacts.

Recycalyse – New Sustainable and Recyclable Catalytic Materials for Proton Exchange Membrane Electrolysers

AbstractWithin the Recycalyse project different research organization and industrial partners worked together to develop catalysts for the oxygen evolution reaction for proton exchange membrane electrolysis that reduce the use of critical raw materials. The catalysts are applied to polymer electrolyte membranes via a direct coating process and tested both in single cells and at stack level. In order to reduce the dependence on material imports in Europe in the long term, recycling is considered for the catalysts, electrodes and the entire system.

(Invited) SOEC Upscale; Material Challenges

To ensure the transition of the global energy system to a sustainable one, and to meet emission reduction targets of national climate policies we need in future to produce large amounts of “green” hydrogen. This will be necessary to sustain the world’s need for synthesis of “green” ammonia, “green” methanol and “green” jet fuels, but also for use in form of hydrogen as a transportation fuel and a reduction agent in steel making. Various electrolysis technologies for providing this hydrogen via an electrochemical splitting of water/steam are likely to become the backbone of this emerging sector.Among the different electrolysis technologies, available or under development, SOEC stands out with distinct advantages related to the high temperature of operation, most markedly; 1) there is no need for precious metals in the electrodes, and 2) the achievable efficiency is higher than for the other electrolysis technologies. The electrical efficiency may exceed 90 % as the technology can be run thermo-neutrally producing no waste heat, or may even utilize waste heat if such exist for instance from a down-stream upgrading of the hydrogen to methanol or ammonia.In view of these very significant advantages, SOEC is likely to become a key enabling technology for the above described transition. However, the SOEC technology is less mature than alkaline electrolysis and PEM-based electrolysis and is today deployed much less than the other two technologies. The largest SOEC units manufactured/operated today are in the range of ~1 MW. However, numerous scale up projects have recently been announced and the industrial stakeholders are these years investing massively to bring up production capacity and module sizes.In this paper we shall discuss some of the challenges in upscaling SOEC and some of the materials issues to be addressed, when considering large scale global deployment over the next decades.The inherent brittle nature of the ceramics used in the cells has so far limited the size of the cells of most stakeholders to be in the range with side-lengths from 10 to 15 cm. Ideally, in terms of upscaling module sizes, this should be much larger. This however requires great care in the manufacturing, and a tough and strong backbone material in the cell. Most stakeholders rely on stabilized zirconia to provide the structural support. Use of zirconia in the transformable (metastable) tetragonal version with 2 – 4 % Y2O3 substitution holds some advantages over the use of the fully stabilized cubic version with ~8 % Y2O3, as the former has much higher strength/toughness. We shall present our recent results on optimizing composition and processing routes to maximize toughness and strength, whilst preventing unintended spontaneous transformation to the monoclinic phase during use, and shall discuss the consequences in terms of upscaling cell foot-print.In SOEC one does not need any precious metals (PGM-materials). However, typically the state of the art cells relies on use of several critical raw materials. Several rare earth materials (HREE/LREE) are used (Ce, Gd, Y, La) and also some critical transition metals like Co/Mn and Ni. Ni is by EU not considered critical, but is on the list of strategic materials. For large-scale deployment, it is obviously an advantage if the use of Critical Raw Materials (CRM) can be minimized.Introducing performance improvement in terms of increased production capacity per m2 of cell or kg of material is a straightforward strategy to reduce the CRM-use of the technology and is likely a part of the strategy among all stakeholders. Endeavors to reduce the use of one particular material are also meaningful in such a materials resource perspective.We shall here present recent results on activities to increase the competitiveness of the SOEC technology by introducing a metal-support as the structural backbone and replace the Ni/YSZ-fuel electrode with one based on a mixed conducting Ti-based oxide (Ni and Fe-doped (La,Sr)TiO3). Recently, we have found that such a material combination can in fact sustain SOEC operation for extended periods (tested over 5000 hr) at technologically relevant hydrogen production rates corresponding to current densities of 0.5 A/cm2. The results shall be presented and the possibilities to improve the titanate backbone further by compositional changes shall be discussed with special view to eliminating use of HREE/LREE and critical raw materials in general.Finally, we shall present some recent results on how to eliminate the use of Co in the oxygen electrode. The achieved results shall be compared with other approaches adopted in literature on how to eliminate use of Co and even La in the oxygen electrode.

Tri-doped mesoporous carbon nanostructures prepared via template method for enhanced oxygen reduction reaction

Doped carbon structures have been developed as non-precious metal catalysts for oxygen reduction reactions (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Among doped carbon structures, Fe- and N-doped carbon (Fe/N/C) nanostructured catalysts have received attention due to their catalytic activity, comparable to that of Pt, avoiding the use of critical raw materials. However, obviously, its durability is not yet neither fully understood nor comparable to that of traditional catalysts. In this study, we synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Tri-doped carbon catalysts with different amounts (x) of F (Fx-Fe/N/C) were prepared using Fe-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine iron(III) chloride and NH4F as the Fe/N- and F- doping sources, respectively, and Santa Barbara amorphous-15 as the template. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic performance for ORRs i.e. a high half-wave potential of 809 mV in 0.1 M HClO4 solution, a maximum power density of 280 mW cm−2, and a high stability for 4000 min at 0.5 V, owing to the high proportion of FeNx and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces.

Practising future‐making: Anticipation and translocal politics of Tesla's Gigafactory in Shanghai as assemblage

AbstractHuman geographers are increasingly concerned with how ‘futures’ are imagined and rendered governable, yet mostly their methods lack the sensitivity to explore the functioning of complex relations between heterogeneous actors across places. The world's electric vehicle (EV) sector is booming, presaging a widely expected decarbonised future, associated with a restructuring of the automobile industry as anticipated by proactive players. This paper interrogates the spatiality and politics of the EV future‐making through disentangling the translocal practices involved in realising Tesla's Gigafactory in Shanghai (TGS) as assemblage. Informed by interviews with industrial insiders and opensource information in Chinese and English, the article finds that, first, TGS's imagined future embodies a multiplicity of interdependent but divergent expectations, the coherence of which underlies the formation and operation of the TGS assemblage by virtue of the concerted actions of its member‐actors. Second, such coherence is conditional as designed by TGS's central planners—namely, Tesla and Chinese government agencies at central and local levels—for their differentiated but overlapping interests. The TGS's imagined future is rendered actionable, enrolling other agents at certain moments, through anticipatory practices of regulatory changes, strategic arrangements interweaving land and financing, firm acquisition and intra‐firm reorganisation linking up places in and outside China, as well as the selection of key suppliers and technological use of critical raw materials. Concluding after a sketch on the TGS's ‘possible futures’ and broader implications, the paper contributes an assemblage‐informed approach to disentangle futuremaking practices and generates timely insights into the ‘future‐oriented’ restructuring of the automobile industry.

Multi-criteria and real-time control of continuous battery cell production steps using deep learning

Electric vehicles driven by batteries are a key part of a sustainable mobility sector. Unfortunately, battery cell production is still associated with various negative environmental impacts, the use of critical raw materials and high manufacturing costs. The rising battery demand forces automotive original equipment manufacturers to drastically increase their capabilities over the next decades while fulfilling economical and ecological requirements. Continuous production technologies bear the potential to meet future battery cell demands by enabling higher throughputs compared to established batch processes. The control and optimization of continuous battery cell production steps with respect to product quality, manufacturing costs and environmental impacts is challenging due to high parameter spaces as well as temporal dependencies of production processes. Therefore, this study develops a controller that performs real-time optimization by proposing set parameters leading to desired quality, minimal costs and impacts of manufacturing activity. The controller is implemented using a deep learning model incorporating sequential information of the production process. A continuous mixing process with data acquired from a battery cell pilot line is used to validate the outlined controller. As result, the implementation for this use case achieves a relative error of 7.63% across all controllable parameters.

Green hydrogen from anion exchange membrane water electrolysis

Current scientific opinion is that in order for H2 to be used for energy storage on a massive scale requires significant reduction or even complete elimination of the use of critical raw materials including rare PGM metals Pt, Ru and Ir. This has given a tremendous boost to interest in water electrolyzers that use anion exchange membranes. This quickly developing field has made significant advances in terms of performance in the last 24 months. This short review summarizes very recent efforts and the remarkable improvements in single-cell electrolysis activity. The combination of improved anion exchange materials, PGM-free catalysts, and MEA preparation methods each provide a piece to assembling the puzzle. This review finishes with recommendations for further research efforts, required to translate the performance of single laboratory cells to large systems for ramp-up to commercialization.

Energy Sustainability—Rebounds Revisited Using Axiomatic Design

Energy Sustainability has been addressed through advancing technology efficiency, which may increase the impact of the use of natural resources. However, the increase in efficiency makes services cheaper, which causes a rebound effect, direct or indirect, on energy consumption and materials. Moreover, the popular concept of recycling seems insufficient to reduce the use of critical raw materials to provide energy services. From the perspective of the Earth’s limited resources, the sustainability problem needs a design approach to tackle the rebound effect from efficiency. This work aims to create a theoretical holistic review regarding energy use linked to technology efficiency, to understand how rebound effects may be prevented. In this work, the Axiomatic Design (AD) theory creates the framework that defines the Energy Sustainability functions and identifies the couplings that create the rebounds. According to AD, cycles occur on coupled designs, classified as poor designs. Decoupling the design clarifies two possible and complementary policies to achieve sustainability goals regarding the use of resources. The first is the circular economy, with constraints on energy and raw materials. The second is the massive use of local renewable energies. Plausible solutions come from mandating efficiency and taxation, dematerializing the economy, and reducing, reusing, remanufacturing, and recycling materials from products and systems. These solutions impact economic, environmental, and societal behaviors. The novelty of this approach is the definition of a system model for Energy Sustainability in the frame of AD, while tackling the rebound effect from technological efficiency.

Efficient Use of Critical Raw Materials for Optimal Resource Management in EU Countries

The European Commission has established a Critical Raw Materials List (CRM) for the European Union (EU), which is subject to regular review and updating. CRMs are needed in many key industries such as automotive, steel, aerospace, renewable energy, etc. To address this issue, we studied publicly available data from databases developed by the EU for monitoring the progress of individual countries in key areas for the development of society. The paper analyzes indicators of import reliance, net additions to stock, domestic material consumption (DMC), resource productivity, and circular material use rate. Prospective products and technologies, in electromobility, digitalization, Industry 4.0, and energy transformation, are changing and increasing the demand for raw materials. The aim of this article is to look at the ways forward in order to use critical raw materials as efficiently as possible while at the same time ensuring the optimal economy of the countries. From the sources and databases of data available for the EU, we analyzed a number of variables and suggested options for future developments in the efficient use of critical raw materials. We defined what we believed to be the optimal management means in relation to critical raw materials and worked backwards to find a path to efficient use of critical raw materials.

A Battery-Free Sustainable Powertrain Solution for Hydrogen Fuel Cell City Transit Bus Application

The paper presents a sustainable electric powertrain for a transit city bus featuring an electrochemical battery-free power unit consisting of a hydrogen fuel cell stack and a kinetic energy storage system based on high-speed flywheels. A rare-earth free high-efficiency motor technology is adopted to pursue a more sustainable vehicle architecture by limiting the use of critical raw materials. A suitable dynamic energetic model of the full vehicle powertrain has been developed to investigate the feasibility of the traction system and the related energy management control strategy. The model includes losses characterisation, as a function of the load, of the main components of the powertrain by using experimental tests and literature data. The performance of the proposed solution is evaluated by simulating a vehicle mission on an urban path in real traffic conditions. Considerations about the effectiveness of the traction system are discussed.

Recent Highlights of Solid Oxide Fuel Cell and Electrolysis Research at DTU Energy

A successful Green Transition requires efficient, and cost competitive technologies for converting & storing energy from renewable sources and for providing energy to the stationary and the transport sector. Solid oxide fuel cells and electrolysis (SOFC, SOE - SOC) provide high efficiencies for electricity generation and production of storage media / fuels, respectively. In addition, they are flexible and versatile, which makes them attractive in many different application areas and energy scenarios.Research on solid oxide concepts has a long tradition at the Department of Energy Conversion and Storage (DTU Energy) of the Technical University of Denmark. It spans from fundamental topics such as materials & electrode development over methodology development for example in micro structural & electrochemical characterization, up to the applied level, where integration of SOC with up- and down-stream processes becomes important. Significant funding from National and European programs supported this research. The presentation will introduce highlights of recent achievements in the areas of (i) materials & electrode development to reach higher activity and better durability, (ii) cell & stack development for lowering costs and increasing robustness, (iii) power to X concepts with special emphasis on X= fuels, (iv) lifetime & diagnostics approaches for accelerating durability studies, and (v) modelling from materials to stack levels aiding lifetime evaluation and designing of stacks & systems.(i) Materials & electrode development: With the aim to reduce use of critical raw materials in SOCs, Co-free oxygen electrodes were developed based on lanthanum, strontium, and iron containing perovskite materials (LSF) applying a nano engineered hybrid catalyst coating via co-infiltration. The electrodes were integrated into cells and a high electro catalytic activity was achieved leading to power densities of ca. 1 W/cm2 in SOFC mode. Such cells with CGO infiltrated Ni/YSZ fuel electrode allowed for a stable electrolysis operation at 650 oC and -0.5 A/cm2 with a voltage close to 1.3 V.(ii) Cell & stack development: A novel, metal-based monolithic concept for SOFC stacks was developed. It is based on tape casting & lamination to build a monolithic structure thereby combining interconnect and gas distribution into one layer. Electro catalytic materials are infiltrated after sintering. This concept allows for an increase of the power density >5 kW/l, a decrease of materials costs by a factor of ca. 4-5 as compared to conventional stacks, and robustness for cycling operations.(iii) Power to X concepts: A novel and efficient route for producing green methanol was demonstrated by use of residue from the agriculture. A 6 kW SOEC stack unit produced hydrogen, which was combined with syngas from a thermal gasifier operating on straw in a down-stream methanol reactor. Methanol is considered a promising green fuel for the shipping sector. The same applies for ammonia. SOFC anodes catalyze the cracking of ammonia. This endothermal process can be integrated and tailored with the exothermal hydrogen oxidation in the electrode. The cracking of ammonia was studied on materials and stack level.(iv) Lifetime & diagnostics approaches: The long lifetimes –both required and achieved - of mature SOC generations make it necessary to develop new approaches for degradation studies and lifetime assessment. With the aim to harvest gained results from single cell durability testing over the last ca. 20 years at DTU Energy, a database was established allowing for a new evaluation of durability behavior. The database makes it possible to apply machine learning routines to reveal linear and non-linear correlations and single & combined effects of operating parameters on durability over a large range of data. The aim is to identify accelerating testing approaches and establish lifetime prediction.(v) Modelling: To further optimize the operation of an SOC and avoid degradation, a time dependent 3D stack model describing the degradation over the entire lifetime was developed. For this to be computational feasible, the model was built using the multi-scale, multi-physics homogenization concept, making it possible to simulate 40,000 hours of operation for a full 3D stack in one hour and 15 minutes. Same modelling concept was also utilized to describe local mechanical failures by use of a sub-model for the mechanical stress concentrations near assembly points inside the stack.

Complex Concentrated Alloys for Substitution of Critical Raw Materials in Applications for Extreme Conditions.

The paper is proposing a mini-review on the capability of the new complex concentrated alloys (CCAs) to substitute or reduce the use of critical raw materials in applications for extreme conditions. Aspects regarding the regulations and expectations formulated by the European Union in the most recent reports on the critical raw materials were presented concisely. A general evaluation was performed on the CCAs concept and the research directions. The advantages of using critical metals for particular applications were presented to acknowledge the difficulty in the substitution of such elements with other materials. In order to establish the level of involvement of CCAs in the reduction of critical metal in extreme environment applications, a presentation was made of the previous achievements in the field and the potential for the reduction of critical metal content through the use of multi-component compositions.

The waste management sector of Hungary

Nowadays, the waste management sector faces a number of challenges. Changes in consumer habits generate huge amounts of industrial and household waste. Today’s trends, which involve a higher use of critical raw materials, such as in the manufacture of batteries and solar cells, make it urgent to extract valuable raw materials from waste. The waste sector as a whole, taking into consideration all levels of the waste hierarchy (prevention, reuse, recycling, energy recovery, landfilling), is a significant branch of the national economy, both in terms of employment and income-generating capacity. In addition, the sector can be considered a major intermediary in industrial value chains as it contributes to the generation of secondary raw materials that can be sold to industries and thus help to achieve a circular economy through the collection, treatment and processing of waste.

Recycling of Critical Raw Materials from Hydrogen Chemical Storage Stacks (PEMWE), Membrane Electrode Assemblies (MEA) and Electrocatalysts

The increase in energy demands for the establishment of a modern digital era has resulted in the significant limitation of the energy sources. The depletion of energy reserves drew attention to alterative renewable energy sources that can satisfy the energy requirements in an environmentally friendly way. Hydrogen is an ideal chemical energy storage. Proton exchange membrane water electrolysis (PEMWE) is a promising technology as a green source of high-purity hydrogen. For that reason, PEMWE devices are already used in aerospace to produce oxygen for the crew on the Space Stations. The use of Critical Raw Materials (CRMs, especially Pt and Ir) and high cost materials in the PEMWE systems compromises their economic feasibility. It is necessary to implement End-of-Life (EoL) strategies that optimise the recovery of CRMs within feasible and environmentally friendly processes. In this paper an overview of the existing technologies for recycling of Membrane Electrode Assembles and electrocatalysts from PEMWE systems are revealed. MONOLITHOS has developed a novel optimized hydrometallurgical method for high PGMs recovery from spent automotive catalysts. This work aims to describe how this method can be applied to the EoL phase of PEMWE to improve techno-environmental and techno-economical performance of CRMs recovery.

Pre-concentration and recovery of silver and indium from crystalline silicon and copper indium selenide photovoltaic panels

The circular use of critical raw materials is regarded as a topic of contemporary interest stimulating continuous research and development to reduce primary resource use and waste production. However, due to the low mass share of such materials in waste streams, the industrial sector mainly focuses on the recovery of bulk components (e.g. base metals). Even in laboratory-scale studies, the fate of critical raw materials through the recycling chain, and the important role of pre-concentration prior to selective recovery have not been sufficiently addressed. To this scope, this study evaluates the mass flow of Ag and In during the treatment of waste polycrystalline silicon and monocrystalline silicon, as well as copper indium selenide photovoltaic panels in order to produce valuable pre-concentrates of these metals. The treatment routes, used in various combinations, are (a) thermal treatment and gravimetric separation, (a) mechanical crushing, sieving and thermal treatment, as well as (c) chemical and thermal treatment of the panels. The pre-concentration yield was investigated assessing the content of Ag or In (mg/kg) in the treated mass share (%) as compared to the initial content and photovoltaic mass used. Then, the selective recovery of Ag or In from the produced treated fractions, which are enriched in Ag or In, was studied through acid leaching and precipitation. Thermal treatment and gravimetric separation resulted in intact target-components and optimal pre-concentration yield of Ag and In (91.42 and 94.25% for crystalline panels, and 96.10% for copper indium selenide panel). A maximum leaching capacity of Ag and In was obtained using HNO3 and H2SO4 solution, respectively. Pure silver chloride (AgCl) was recovered using HCl as precipitating agent and pure indium hydroxide (In2O3) using NH4OH. Overall, the study pointed out that waste photovoltaic panels are new and complex products that can be considered as secondary sources to recover Ag and In, when a suitable combination of treatment processes is applied.

Suppressing the Use of Critical Raw Materials in Joining of AISI 304 Stainless Steel Using Activated Tungsten Inert Gas Welding

The aim of this study was to study the influence of TiO2 coating for its efficacy during the activated-tungsten inert gas (TIG) welding and to suppress the use of consumables that are rich in critical raw materials. Post-welding penetration depth, particle size distribution, microstructure, and microhardness of welded samples were assessed. Based on these results, it was found that there is no direct correlation between the weld metal surface area and the coating. The particle size in the coating, although, seemed to have played an important role, e.g., nanoparticles resulted in an increased penetration depth and depth/width (D/W) ratio as opposed to the submicron-sized particles. The most optimal welding condition resulted when a mixture of submicron-sized and nanometric-sized particles were used. It was demonstrated by the Zeta analyser results that the micron particles rub the nanoparticles due to mechanical friction resulting in smaller oxide particle formation in the coating. Finally, the presence of Marangoni convection in TIG and reversed Marangoni convection in the activated TIG (A-TIG) process were proven by means of the microstructure analysis and measurement, which were found to be positively correlated.

Rare-earth elements in the circular economy: The case of yttrium

This paper discusses the economic rationale of recycling exhaustible raw materials and assesses how a circular economy perspective can improve the sustainable use of critical raw materials (CRMs). We use the case study of yttrium, a rare-earth element (REE) on the EU list of CRMs, given its widespread use in the electronics industry and the geopolitical concentration of its supply. Even if recycling REEs from waste electric and electronic equipment is a valid alternative to extraction from mines, as proposed by the circular economy paradigm, less than 1% of REEs used today are recycled. Nevertheless, studies on the economic benefits of recovery REEs are very limited. In this paper, we present the business case of an Italian recycling company, Relight Ltd., and its HydroWEEE project, to recycle REEs such as yttrium, from spent lamps. In environmental terms, recycling REEs has a much lower impact than their extraction from virgin source. In economic terms, it is profitable to recycle yttrium if its market price is above 14€/kg, and above 9.54€/kg taking in consideration the external costs of mining. Therefore, in 2012 and 2013, recycling was profitable thanks to the high price of yttrium, while between 2014 and 2016 recycling was not cost effective. In these cases, policymakers must incentivize recovery and recycling solutions with appropriate policies.

EU use of critical raw materials needs improvement for circular economy

EU use of critical raw materials needs improvement for circular economy

Intermetallics as innovative CRM-free materials

Many of currently used technical materials cannot be imagined without the use of critical raw materials. They require chromium (e.g. in stainless and tool steels), tungsten and cobalt (tool materials, heat resistant alloys), niobium (steels and modern biomaterials). Therefore there is a need to find substitutes to help the European economy. A promising solution can be the application of intermetallics. These materials offer wide variety of interesting properties, such as high hardness and wear resistance or high chemical resistance. In this paper, the overview of possible substitute materials among intermetallics is presented. Intermetallics based on aluminides and silicides are shown as corrosion resistant materials, composites composed of ceramics in intermetallic matrix as possible tool materials. The manufacturing processes are being developed to minimize the disadvantages of these materials, mainly the room-temperature brittleness.

New preparation and recycling procedure to recover rare earth elements from magnets by using a closed loop treatment

The use of critical raw materials also increases due to the higher demand on electrical and electronic equipment (EEE). The high content of valuable substances in EEE in relation to primary ores secures a potential for its use as new raw materials sources, the so-called ‘urban mining’. Positive effects of urban mining are to save existing mineral resources as well as to relieve the primary production and get a new opportunity instead of landfilling. The subsequently described research work at the Chair of Nonferrous Metallurgy at the University of Leoben is concentrated on the preparation of hard disc drives (HDDs). Currently, the main problem to recover neodymium–iron–boron (NIB) magnets is the missing technology for preparation. A disassembling of HDD by hand is not economic and a treatment by a shredding machine destroys the NIB magnets, so that they cannot be separated and fed into a proper recycling process. Therefore, the investigation leads to a thermal treatment to obtain the components of a HDD in separated form. The investigation also focuses on a metallurgical way to recover the technological metals like neodymium, copper, gold as well as a reusable aluminium alloy. Therefore, a closed loop treatment was found to clean the leaching agent and reuse it to reduce the amount of waste streams.