Pratima Meshram

Recovery of valuable metals from cathodic active material of spent lithium ion batteries: Leaching and kinetic aspects

This work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1M H2SO4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh-pH diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD phase identification and the SEM-EDS studies.

Process optimization and kinetics for leaching of rare earth metals from the spent Ni-metal hydride batteries.

Nickel-metal hydride batteries (Ni-MH) contain not only the base metals, but valuable rare earth metals (REMs) viz. La, Sm, Nd, Pr and Ce as well. In view of the importance of resource recycling and assured supply of the contained metals in such wastes, the present study has focussed on the leaching of the rare earth metals from the spent Ni-MH batteries. The conditions for the leaching of REMs from the spent batteries were optimized as: 2M H2SO4, 348K temperature and 120min of time at a pulp density (PD) of 100g/L. Under this condition, the leaching of 98.1% Nd, 98.4% Sm, 95.5% Pr and 89.4% Ce was achieved. Besides the rare earth metals, more than 90% of base metals (Ni, Co, Mn and Zn) were also leached out in this condition. Kinetic data for the dissolution of all the rare earth metals showed the best fit to the chemical control shrinking core model. The leaching of metals followed the mechanism involving the chemical reaction proceeding on the surface of particles by the lixiviant, which was corroborated by the XRD phase analysis and SEM-EDS studies. The activation energy of 7.6, 6.3, 11.3 and 13.5kJ/mol was acquired for the leaching of neodymium, samarium, praseodymium and cerium, respectively in the temperature range 305-348K. From the leach liquor, the mixed rare earth metals were precipitated at pH∼1.8 and the precipitated REMs was analyzed by XRD and SEM studies to determine the phases and the morphological features.

Overview On Extraction and Separation of Rare Earth Elements from Red Mud: Focus on Scandium

ABSTRACT The article provides an overview of the methods used for processing of red mud to extract rare earth elements (REEs). Red mud is a toxic and highly alkaline waste. Several methods have been adopted and been practiced all over the world for the processing of red mud. Complex processing of red mud is cost-effective since red mud contains elements such as iron, aluminum, titanium, calcium, and rare earth metals. It has been observed that the acid leaching of red mud can almost completely recover the rare earth elements in the solution with various individual techniques and also a combination of them. Therefore, the choice of extraction method depends on the form in which the element occurs in the solution. However, relatively low concentrations of rare earth in the solution and significant amounts of impurities increase the cost of getting the final commercial products. To ensure the cost-effectiveness of the process involving rare earth’s extraction from red mud, it is necessary to increase their content by several times. This article presents the various studies that have been carried out in these aspects and the possibility of making this resource a sustainable one for REE extraction with a special focus on scandium replenishment.

Advanced review on extraction of nickel from primary and secondary sources

ABSTRACT In this review, resources of nickel and status of different processes/technologies in vogue or being developed for extraction of nickel and associated metals from both primary and secondary resources are summarized. Nickel extraction from primary resources such as ores/minerals (sulfides, arsenides, silicates, and oxides) including the unconventional one viz., the polymetallic sea nodules, and various secondary resources has been examined. Though sulfide ores after concentration are generally treated by the pyro-metallurgical route, most processes for lateritic ores deal with either the acid leaching at ambient temperature and pressure, or high pressure, and a few based on the microbial treatment and owing to the extensive research on laterites, a special emphasis is put forth in this review. Prominent sources that are covered in some detail include the solid wastes like spent batteries viz., end-of-life nickel-cadmium (NiCd) and nickel metal hydride (NiMH), spent catalysts, and spent/scrap superalloys, and liquid wastes such as copper bleed stream and electroplating effluents. In particular pre-treatment of the spent nickel-based batteries, leaching of metals from the electrode materials in different lixiviants, besides separation/solvent extraction of nickel/other metals from the leach liquors, are highlighted.

Organic acid leaching of base metals from copper granulated slag and evaluation of mechanism

ABSTRACT A hydrometallurgical method is discussed to selectively extract base metals such as copper, cobalt, nickel and iron from the copper granulated slag (0.53% Cu) at atmospheric pressure. It involves first-stage leaching of slag with organic (citric acid) to selectively recover cobalt, nickel and iron. The residue containing high copper was subjected to second-stage leaching with inorganic (sulphuric) acid. Leaching parameters such as acid concentration, pulp density, temperature and time were optimised to extract metals from the granulated slag. A maximum recovery of 4.47% Cu, 88.3% Co, 95% Ni and 93.8% Fe were obtained in first-stage leaching with 2u2005N citric acid at room temperature using 10% pulp density (w/v) in 8–9u2005h. On subjecting the leach residue to the second-stage leaching with 2u2005M sulphuric acid, 66–72% Cu was recovered in 4u2005h. The kinetics of the metal leaching from the slag was established by the XRD and SEM–EDAX studies of the residues.

Extraction of vanadium and synthesis of vanadium pentaoxide from Bayer's sludge

Wastes generated from the Bayer’s process serve as valuable resources for aluminum, vanadium, gallium, etc. This work aims to develop a environmentally acceptable and low-cost chemical leaching-cumpurification method for the recovery of vanadium sludge of Indian alumina plant (10–12% V2O5) and synthesize vanadium pentaoxide. The efficiency of leaching was evaluated by various lixiviants like acidified water, H2SO4, soda and NaOH against variation in pulp density and temperature. Maximum extraction (96%) vanadium was achieved using acidified water leaching at above ambient temperature in 1 h with 200 g/L pulp density following diffusion control model. Finally, the vanadium rich leach liquor was purified by steps of adsorption/precipitation etc., to remove with iron and silica to get vanadium pentaoxide. A high purity product of 99% V2O5 was obtained by allowing the adsorption at acidic pH followed by desorption and precipitation at 90°C.

Arsenic Removal from Spent Liquor Generated during Processing of Vanadium Sludge

During production of ammonium meta-vanadate from vanadium sludge an arsenic containing (~2.2g/L) spent liquor is generated. Safe disposal of such liquor without arsenic contamination to the environment is essential. Therefore, various methods such as ion-exchange, adsorption, solvent extraction and precipitation were applied for recovery of arsenic from the spent liquor. Based on the Eh-pH diagram of As-H2O, the arsenic based species were delineated. For ion exchange Lewatit FO 36 and Amberlite IRA 400 Cl- resins were used to extract arsenic from the spent liquor. With Lewatit FO 36 a maximum of 20% arsenic was recovered at A/R ratio of 50. Amberlite IRA 400 Cl- on the other hand didnt extract arsenic at all. A two stage solvent extraction process using TBP as an extractant, with a recovery of 97% arsenic from the spent liquor was developed. From the loaded TBP almost complete stripping of arsenic was obtained with 0.1-0.5M NaOH solution. Precipitation of arsenic from the spent liquor as copper arsenate or iron arsenate was also examined. During the fixation of arsenic with iron, 70% arsenic was recovered in the precipitate. This process needs to be evaluated further with the aim of using the iron hydroxide containing arsenic for different applications.