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Bioaugmentation of Municipal Waste
Published in Inamuddin, Charles Oluwaseun Adetunji, Mohd Imran Ahamed, Tariq Altalhi, Bioaugmentation Techniques and Applications in Remediation, 2022
Deviany Deviany, Siti Khodijah Chaerun
Commonly, the next step of treatment for WEEE is based on pyrometallurgy, hydrometallurgy, and electrometallurgy process. WEEE is heated at a high temperature in pyrometallurgy, sometimes above 1,000°C, separating into different phases to extract the precious metals from impurities. High energy consumption and toxic gas production are linked to this process. Hydrometallurgy utilized strong acids and bases as leaching agents combined with complexing agents in an aqueous solution to recover metals. These agents include sulfuric acid, acetic acid, carbonic acid, oxalic acid, thiosulfate, thiourea, and halide. Compared with pyrometallurgy, hydrometallurgy requires lower energy and operational cost for the plant with relatively low capacity. Electrometallurgy uses electrical power to recover metal from its compounds/ores, for example, electrowinning/electroextraction and electrorefining of copper, zinc, and other elements. This process can also be considered energy-consuming. Rocchetti et al. (2013) suggested a combination of treatment with a chemical approach that is usually more efficient and a biological approach that is relatively safe for the environment taking advantage of both leaching applications. To summarize, until today, the management of WEEE treatment is done to recover and recycle resources by pyrometallurgy and hydrometallurgy, regeneration of spent catalyst, and landfill disposal.
Recovery of Rare Earth Elements from e-Wastes (Nd-Fe-B Spent Magnets) Using Magnesium Chloride Salts
Published in Sheila Devasahayam, Kim Dowling, Manoj K. Mahapatra, Sustainability in the Mineral and Energy Sectors, 2016
Komal Babu Addagatla, Sheila Devasahayam, M. Akbar Rhamdhani
There are several processing methods which can be carried out to extract the REE metals present in the material obtained from the preprocessed step. The methods used in processing are as follows (Schluep et al., 2009; ICF International., 2011; Meyer and Bras, 2011; Walton and Williams, 2011): Electrometallurgy process, such as electrowinning where current is passed from an inert anode through a liquid leach containing the required metal; the metal is extracted by an electroplating process where the material gets deposited on the cathode.Hydrometallurgy process, where strong acids or basic solutions are used to dissolve and precipitate metal of interest from a powder form. Processes such as selective leaching, solvent extraction, and selective precipitation are followed for recovering the metals. Hydrometallurgy process has been developed for the recovery of cobalt, nickel, and rare earth metals from Ni-MH batteries (Kuzuya et al., 2003). Rare earths are dissolved using sulfuric acid followed by precipitation using sodium hydroxide (Bertuol et al., 2009). Higher recovery rates are expected for the hydrometallurgy process, compared with the other processes, that is, 90%–95% of rare earth elements (RREs) can be recovered, but with considerable impact on the environment (Ellis et al., 1994). This process generates large volumes of hazardous substances that do not decompose under normal environment.Dry process which is still under investigation uses hydrogen gas at atmospheric pressure to turn the Nd-containing magnets to a powder that can be reformed into new magnets under heat and pressure. This research is being conducted at the University of Birmingham in the United Kingdom, where the newly produced magnets do not have the same quality as the originals, but they can be used in monitors (Davies, 2011).Pyrometallurgy process, which uses high temperature to convert the feed materials chemically and separate them so that required metals can be recovered. During this process REEs form rare earth oxides which make the recovery difficult. During this process some of the volatile organic compounds and other dioxins are generated and particular care is needed to manage these products.Tailing recycling is a process where reprocessing of the tailings are carried out to extract the remaining amounts of REEs they contain. This generally occurs at the mining stage using the same equipment that are used to process the original ore. This process is economically beneficial (University of Leeds, 2009; Xiaozhi, 2011), having good power savings, and significant environmental benefits.
Opportunities for an en-route to polymer inclusion membrane approach from conventional hydrometallurgical recycling of WPCBs: a mini-review
Published in Canadian Metallurgical Quarterly, 2022
Rohit Jha, Gautam Mishra, Munmun Agrawal, Mudila Dhanunjaya Rao, Arunabh Meshram, Kamalesh K. Singh
Reutilisation and remanufacturing of old equipment are not possible without thorough research on recycling techniques. In the initial attempts to recycle WPCBs, incineration was adopted, resulting in the generation of harmful gases like dioxins owing to the presence of copper and brominated flame retardants (BFRs). On the other hand, pyrometallurgy is a sequence of several processes such as pyrolysis, smelting in blast furnaces plasma treatment, melting and chemical reactions in gas phases at very huge temperatures. Eventually, the pyrometallurgy route was followed for the recovery of metals from WPCBs [10]. However, limitations like high capital cost, compromised purity in partially recovered metal, hazardous gas formation and high slag generation owing to the presence of ceramics in WPCBs lead the researchers to focus on hydrometallurgy coupled with electrometallurgy [11,12].
Factorial design for process optimization and generation of kinetic data for yttrium and europium leaching
Published in Mineral Processing and Extractive Metallurgy, 2021
Amit Anand, Randhir Singh, Malay Kumar Ghosh, Kali Sanjay
The chemical forms in which REMs are present in phosphors limit the application of pyro or electrometallurgy and make hydrometallurgy the most suitable route for extracting these metals (Tunsu et al. 2015). In hydrometallurgy, leaching is the first step which involves selective dissolution of targeted metals into aqueous phase. Several researchers have carried out leaching studies of Y and Eu from phosphor. Optimum leaching conditions suggested by some of these studies are listed in Table 2.
Sustainability of rare earth elements chain: from production to food – a review
Published in International Journal of Environmental Health Research, 2018
The second step, REO of individual elements are extracted from concentrates. This operation known as extraction is undertaken by hydrometallurgy (e.g. ion exchange, solvent extraction, fractional crystallization), electrometallurgy or pyrometallurgy. The first one is the most widely used by the industry. The recovered oxides are usable and marketable as such, they are generally further refined in order to produce pure REM.