Pr. Prakash Venkatesan

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Articles dans des revues avec comité de lecture

2026

Tweaking the electrodes of LiFePO4/FePO4-based electrochemical lithium-ion pumping system for lithium extraction

2025

Evaluation of early-stage dissolution of spent NdFeB permanent magnets in organic acids by in-situ quantitative reflected light microscopy

Reductive Leaching of Lithium-Ion Battery Cathode Active Material with Copper and Its Recovery by Cobalt Cementation

Recycling of lithium-ion batteries (LIBs) is crucial for strengthening environmental sustainability and advancing toward a circular economy. Although the separation of spent battery cathodes yields a substance known as cathode active material (CAM), its purity falls short of reuse. The present study employs hydrometallurgical processes to extract and refine the valuable elements within the CAM. This study proposes a more cost-effective solution, utilizing copper (Cu) extracted from spent batteries instead of costly reductants like hydrogen peroxide (H2O2) or organic alternatives like glucose and citric acid. Through investigating various parameters including temperature, sulfuric acid (H2SO4) concentration, Cu addition amount and it is found that Cu addition significantly enhances CAM dissolution allowing more than 98% dissolution under optimized conditions. In the following step, a cementation technique is used to efficiently retrieve dissolved Cu using metallic Co thereby circumventing impurities and boosting cobalt recovery during solvent extraction. This way, a 94% Cu recovery is obtained under optimized cementation conditions, highlighting this study's efficiency for sustainable LIB recycling.

An Acid Free Electrified Process for Recycling Rare-Earth Elements from NdFeB Magnet Waste

Recycling of rare-earth elements (REEs) from NdFeB magnets is an important strategy to mitigate the risks associated with the REE supply chain. In this article, we propose an electrochemical process to recover REEs wherein all the reagents required for both leaching of REEs as well as the precipitation are generated in situ electrochemically. A three compartment electrochemical reactor was used in which a rare-earth containing salt along with an additive salt, ammonium sulfamate, was fed into the middle compartment. Upon electrolysis, the salts were split into acid and rare-earth hydroxides. The acid generated in the anolyte compartment was used to leach the NdFeB magnet waste. The rare-earth hydroxides were collected in the catholyte compartment and calcined to obtain rare-earth oxides. More than 95% of REEs and cobalt were extracted into the solution, and more than 85% of iron was removed as Fe(OH)3precipitate in the same step. Subsequently, the leachate was oxidized and neutralized to remove more than 99% of iron. By using electrons as green reagents, this process combines leaching and precipitation in a single reactor enabling process intensification. The leachate produced at the end is rich in REEs and can be fed again into the middle compartment, forming a completely closed-loop process. Overall, the process consumes no acid, only electricity, ammonium hydroxide for neutralization, and an additive salt, ammonium sulfamate.

Reductive Leaching of Cathode Active Material from Li-Ion Batteries and Recovery of Copper Reductant

DecarbonizationReductive leachingofRecovery the transportation sector has led to an increase in the adoption of lithiumLithium-ionLithium-ion batterybatteriesBattery or LIBs. Efficient recyclingRecycling of Li-ion batteriesBattery is essential to conserve resources and address challenges related to sustainable extraction and supply of critical batteryBattery materials like Li, Ni, Mn, and Co. Hydrometallurgical processes often employ expensive reductants to dissolve transition metals with higher oxidation states in the cathode active mass. To address this issue, the current study proposes an alternative and cost-effective approach by utilizing copperCopper extracted from the spent batteriesBattery as a reducing agent, replacing costly options like H2O2, glucose, and citric acid. The dissolved copperCopper is subsequently recovered through electrowinningElectrowinning. The study investigates the effect of H2SO4 concentration, and Cu amount on the dissolution of cathode active material. During leachingLeaching, a dissolution rate of more than 98% can be achieved for the batteryBattery material, and the consumed copperCopper can be completely recovered through electrowinningElectrowinning in metallic form.

2024

Synergetic recycling of permanent magnet and Li-ion battery cathode material for metals recovery

Rare earth elements (REEs)-based (NdFeB) magnets and lithium−ion batteries (LIBs) are critical for a low−carbon economy. Their production depends on critical elements like REEs, Li, Co and Ni. Recycling of these products have been explored separately as a potential solution. Conventional methods for recycling NdFeB magnets and LIBs face challenges like high energy consumption, lengthy processing, excessive reagent usage, and waste generation. In this study, a novel synergetic recycling methodology is proposed to minimize these challenges. The idea is based on using waste ferrous sulfate solution generated during magnet leaching as a reducing and leaching reagent for battery recycling thereby eliminating the need for additional reagents for oxidation of iron in NdFeB and reduction of cathode material in LIBs. The magnet is leached in diluted H2SO4 at 70 °C followed by double sulfate precipitation for REEs with Na2SO4. The REE-depleted but acidic ferrous solution is then used for reductive leaching of cathode material at 90 °C. The overall recovery rates of REEs, Li, Co, Ni, and Mn in this process are >95%. The iron from magnet material is recovered as crystalline and easily-filterable iron compound that can be converted to goethite and used as a byproduct. This synergetic approach not only reduces reagent consumption and waste generation aligning with the principles of circular economy but also offers improved efficiency, resource conservation, and environmental sustainability.

Novel routes for synthesis of rare earth oxychlorides

Rare earth oxychlorides (REOCl) have received significant interest for their potential applications in chloride ion conductors, catalysts, luminescent materials due to their unique and special properties. Many synthesis methods were reported for their production including solid-state, flux-assisted, and sol-gel techniques. The present study introduces two straightforward solid state synthesis routes for synthesizing desired oxychlorides. In the first route, REOCl is prepared by roasting of a mixture of hydrous rare earth chloride (RECl3.xH2O) and rare earth oxide (RE2O3) powder. The second route involves, initial curing followed by roasting a portion of RE2O3 with hydrochloric acid (HCl) for production of the oxychlorides. For both routes, the optimal process conditions were first defined for LaOCl synthesis. Subsequently, the refined conditions of second method were successfully applied to the synthesis of NdOCl and SmOCl. The thorough mineralogical and morphological analysis of the obtained products under these conditions provides valuable insights into their characteristics and potential applications.

2023

The Effect of Mechanochemical Activation on Carbothermic Reduction of Pyrolusite Ore

A laboratory-scale investigation of the effect of milling operation and catalyst addition (K2CO3) on the partial reduction of low-grade pyrolusite ore pellets was carried out using coke as a reductant. Thermogravimetric analysis was used to understand the correlation between milling and catalyst addition parameters with the reduction temperatures. DTG analysis of pyrolusite pellet reduction showed three distinctive peaks associated with a three-step reduction mechanism (i.e., MnO2→Mn2O3→Mn3O4→MnO). The results showed that the grinding and addition of the catalyst have a significant effect on lowering the MnO2 reduction temperature independently. But maximum reduction temperature drop is obtained when combining grinding and catalyst addition in this work. By 3 h milling and 10 wt% catalyst addition, the reduction temperatures were reduced by more than 200 °C compared to the raw ore pellets. These results obtained from the DTG analysis were further supported by XRD analysis of the reduced samples.

2021

Hydrometallurgical Production of Electrolytic Manganese Dioxide (EMD) from Furnace Fines

The ferromanganese (FeMn) alloy is produced through the smelting-reduction of manganese ores in submerged arc furnaces. This process generates large amounts of furnace dust that is environmentally problematic for storage. Due to its fineness and high volatile content, this furnace dust cannot be recirculated through the process, either. Conventional MnO2 production requires the pre-reduction of low-grade ores at around 900 °C to convert the manganese oxides present in the ore into their respective acid-soluble forms; however, the furnace dust is a partly reduced by-product. In this study, a hydrometallurgical route is proposed to valorize the waste dust for the production of battery-grade MnO2. By using dextrin, a cheap organic reductant, the direct and complete dissolution of the manganese in the furnace dust is possible without any need for high-temperature pre-reduction. The leachate is then purified through pH adjustment followed by direct electrowinning for electrolytic manganese dioxide (EMD) production. An overall manganese recovery rate of >90% is achieved.

2019

Use of iron reactive anode in electrowinning of neodymium from neodymium oxide

2018

Selective electrochemical extraction of REEs from NdFeB magnet waste at room temperature

A closed loop room temperature electrochemical process for selective recovery of REEs from NdFeB magnet waste.

Selective Extraction of Rare-Earth Elements from NdFeB Magnets by a Room-Temperature Electrolysis Pretreatment Step

An environmentally friendly electro-oxidative approach to recover valuable elements from NdFeB magnet waste

2017

Identification and recovery of rare-earth permanent magnets from waste electrical and electronic equipment

Electrochemistry during efficient copper recovery from complex electronic waste using ammonia based solutions

Effective treatment for electronic waste - Selective recovery of copper by combining electrochemical dissolution and deposition