Cristian Tunsu

Studies on the Solvent Extraction of Rare Earth Metals from Fluorescent Lamp Waste Using Cyanex 923

The growing need for materials such as rare earth metals (REMs) has focused attention towards their recovery from various end-of-life products. Fluorescent lamps are considered a viable target, and can be a source of up to six REMs: lanthanum, cerium, europium, gadolinium, terbium, and yttrium. In this study a commercial mix of trialkylphosphine oxides (Cyanex 923) was investigated for the extraction of REMs from fluorescent lamp waste leachates. The kinetics of the extraction is addressed, together with the co-extraction of undesired elements (iron and mercury), the influence of temperature, nitric acid concentration in the aqueous phase and ligand concentration in the organic phase. The extraction of REMs was found to be enthalpically driven, with good separation factors between the light and heavier elements. Selective stripping of REMs was possible in a single step using 4 M hydrochloric acid solution. Further recovery of iron and mercury was carried out using nitric and oxalic acid solutions.

Investigations regarding the wet decontamination of fluorescent lamp waste using iodine in potassium iodide solutions

With the rising popularity of fluorescent lighting, simple and efficient methods for the decontamination of discarded lamps are needed. Due to their mercury content end-of-life fluorescent lamps are classified as hazardous waste, requiring special treatment for disposal. A simple wet-based decontamination process is required, especially for streams where thermal desorption, a commonly used but energy demanding method, cannot be applied. In this study the potential of a wet-based process using iodine in potassium iodide solution was studied for the recovery of mercury from fluorescent lamp waste. The influence of the leaching agents concentration and solid/liquid ratio on the decontamination efficiency was investigated. The leaching behaviour of mercury was studied over time, as well as its recovery from the obtained leachates by means of anion exchange, reduction, and solvent extraction. Dissolution of more than 90% of the contained mercury was achieved using 0.025/0.05 M I2/KI solution at 21 °C for two hours. The efficiency of the process increased with an increase in leachant concentration. 97.3 ± 0.6% of the mercury contained was dissolved at 21 °C, in two hours, using a 0.25/0.5M I2/KI solution and a solid to liquid ratio of 10% w/v. Iodine and mercury can be efficiently removed from the leachates using Dowex 1X8 anion exchange resin or reducing agents such as sodium hydrosulphite, allowing the disposal of the obtained solution as non-hazardous industrial wastewater. The extractant CyMe4BTBP showed good removal of mercury, with an extraction efficiency of 97.5 ± 0.7% being achieved in a single stage. Better removal of mercury was achieved in a single stage using the extractants Cyanex 302 and Cyanex 923 in kerosene, respectively.

Hydrometallurgical Processes for the Recovery of Metals from WEEE

Pyrometallurgy and hydrometallurgy are two routes usually implemented to recover valuable metals from primary and secondary resources. In recent years, the metallurgical industry has been searching for hydrometallurgical processes as an alternative to pyrometallurgical treatments due to some inherent advantages associated with hydrometallurgy, such as the possibility of treating low-grade resources, easier control of wastes, and lower energy consumption. This chapter will give an overview of the hydrometallurgical processes developed to recover metals from waste electrical and electronic equipment (WEEE), including leaching, precipitation, solvent extraction, and resin ion exchange.

Targeting fluorescent lamp waste for the recovery of cerium, lanthanum, europium, gadolinium, terbium and yttrium

Owing to the ever-growing demand and supply problems, rare earth elements (REEs) are now considered to be some of the most critical elements. This has focused attention towards their recovery from end-of-life products and industrial waste streams. A hydrometallurgical approach was carried out to assess the recycling potential of REEs from fluorescent lamp waste. In comparison to other efforts in this field, these investigations were carried out using real waste samples originating from a discarded lamp processing facility. Leaching of metals from the waste was studied using nitric, hydrochloric, sulphuric and methane sulphonic acid solutions. Separation of REEs from nitric acid media was investigated using solvent extraction. Batch extraction experiments were carried out using Cyanex 923, a commercial mix of trialkylphosphine oxides. Separation of heavier REEs (terbium, europium and gadolinium) and yttrium from lighter REEs (cerium and lanthanum) is possible due to larger separation factors. Selective stripping of REEs from the co-extractable species (iron and mercury ions) was easily achieved using 4 M hydrochloric acid. Further recovery of the extracted iron and mercury, with either oxalic acid or nitric acid solutions, allows for the subsequent re-use of the organic phase in the process.

Hydrometallurgy in the recycling of spent NdFeB permanent magnets

Abstract Neodymium–iron–boron (NdFeB) magnets are used in many applications, from small consumer electronics to future sustainable technologies, e.g., electric transportation and wind power. Rare earth elements (REEs) amount to about a third of the composition of NdFeB magnets. Given that REEs are presently considered critical and have very high supply risk, their recycling from end-of-life products has received increased attention. Magnet-containing streams are valuable secondary sources of REEs, e.g., neodymium, praseodymium, dysprosium, and terbium. This chapter discusses the hydrometallurgical options available for processing NdFeB magnets, whether from end-of-life applications or production residues. The need for recovering REEs from NdFeB materials and the challenges associated with this are addressed. Leaching of magnets and precipitation and solvent extraction of metal ions in the obtained leachates are discussed at length, highlighting the potential and limitations of these methods. Several steps required prior to hydrometallurgical treatment are also described, e.g., dismantling of products and hydrogen decrepitation. A literature review of the available hydrometallurgical processes to treat magnets is presented, focusing on selective and nonselective leaching, selective precipitation, solvent extraction with conventional extractants and ionic liquids, and further refining of products in solution.