Kunming University of Science and Technology (KUST) has successfully developed, designed, fabricated and installed industrial microwave units for (i) removal of halides, (ii) activation of carbon, (iii) heating of dust laden air in electrostatic precipitators, (iv) drying of water based paints, and (v) heating of the HF pickling solution for cold rolled titanium alloy coils. This review article provides a summary of these process metallurgy applications. It is found that the use of microwave energy can increase the process efficiency, giving advantages, such as lower reaction temperature and shorter reaction time compared to traditional processes.可显著降低反应温度、缩短时间,具有强化作用
Among lithium minerals, spodumene contains the highest value of lithium, and therefore developing new or improving existing processes for extracting lithium from spodumene can have a significant effect in lowering the cost of lithium production. Spodumene can exist in three different polymorphs, namely α-, β-, and γ-spodumene. Studies to date confirm that α-spodumene, which is the naturally occurring form of spodumene, is refractory to leaching and has to be converted to a more reactive form in which lithium atoms are more accessible to the extraction reagent. So far, calcination at temperatures of around 1000°C prior to extraction is the most promising approach. The calcination produces β-spodumene as the primary polymorph and in some cases limited amounts of γ-spodumene. In addition to calcination, microwave-assisted heating and mechanical activation can also produce phases that are more reactive. Microwave-assisted production of β-spodumene can be achieved faster and using less energy than heating in a conventional oven. However, some challenges with this approach have been identified. Mechanical assisted processes too can lead to the formation of an amorphous phase, which is to some extent suitable for efficient lithium extraction. This article will provide details of spodumene mineralogy, an overview of current pretreatment technology, and a summary of alternative options for the activation stage of the extraction process.
The growing demand for eco-friendly activated carbon necessitates sustainable production methods. This study investigates the conversion of waste wood into activated carbon using goethite iron ore as an activating agent. A high-temperature rotary furnace was used to activate the carbon at 1373 K. The oxygen released from the iron oxide during the heat treatment reacted with the carbon in the wood, resulting in 49% of activated carbon with BET surface areas between 684 m2/g and 770 m2/g. The activated carbon and char showed type I isotherms with micropore areas between 600 m2/g and 668 m2/g, respectively. Additionally, 92% of the iron in the ore was reduced from ferric to ferrous. The findings demonstrate that goethite iron ore is an effective activating agent for producing wood-based activated carbon while also generating metallic iron as a byproduct. This alternative activation method enhances the sustainability and efficiency of activated carbon production.
Recovery of valuable metals from end-of-life cylindrical lithium-ion batteries (LiBs) by leaching using acetic acid in the presence of an organic reductant is a promising combination to overcome environmental concerns that arise from employing inorganic reagents. This study investigated the effect of using molasses as a reductant in acetic acid leaching of a mixture of cathode and anode materials (black mass) prepared using mechanical treatments from spent LiBs. The effects of temperature, solid/liquid ratio, stirring speed, and acid concentration on the leaching of target metals (Co, Ni, Mn, and Li), current collector metal foil elements (Al and Cu), and Fe from the battery casing, with and without reductant, were investigated to obtain the optimum leaching conditions. The effect of adding the molasses at the start of leaching and after 1 h of leaching was tested. Acid leaching without molasses extracted the target metals Li, Ni, Co, and Mn with an efficiency <35% for all leaching parameters. However, the Al and Fe extractions increased as the acid molarity increased. Molasses addition at the start of leaching increased the extraction of the target metals to >96% at temperatures >50 °C. This is likely due to oxidation of the reducing sugars in the molasses that reduced the insoluble Co(III), Ni(III), and Mn(IV) components to soluble Co(II), Ni(II), and Mn(II) species, respectively. The kinetics of Co extraction in the presence of molasses were analysed, which has indicated that the rate-determining step in the Co leaching process is the reduction of Co(III) on the surface of particles in the black mass. Excess molasses can precipitate out target metals, especially Co, due to the presence of oxalic acid in the molasses. The reducing effect precipitated Cu(II) to Cu2O, and could further reduce Co to metal, which suggests that leaching with the optimum dosage of acetic acid and molasses may selectively precipitate copper.
The aim of lithium-ion battery (LiB) recyclers is to create a closed-loop process to recover and reuse all the material as secondary sources of material to manufacture new batteries. Global LiB recycling companies apply pyrometallurgy, hydrometallurgy, or direct recycling to meet this goal. Pyrometallurgy is very energy intensive, but hydrometallurgy requires a pretreatment process and a new version of direct recycling that shows more promise for automation would also require pretreatment. Currently, recycling companies appear to favor hydrometallurgy. This review summarizes the current state of development of the pretreatment process involving battery discharging and mechanical treatment series from the literature and its application in the industry, with particular attention on Asia Pacific recyclers. The key pretreatment steps of battery discharging and mechanical treatment are the focus of this review, but pretreatment of the black mass containing cathode material prior to leaching is also included. Discharging is important to reduce the risk of fire during mechanical treatment. An interesting finding is that despite promising laboratory results, there has been no reported commercial application of battery discharging using the submersion method in an electrolyte solution. An efficient mechanical treatment of discharged batteries is essential to remove the impurities which could adversely impact the subsequent LiB processing. Research into mechanical treatment should also include a method to evaluate the liberation of material. This review has highlighted a new potential flowchart for recycling of various cathode types of LiBs.
Abstract This review addresses the detrimental effects of fluoride on the various steps which constitute any hydrometallurgical operation. It focuses on the specific examples of apatite flotation, copper bioleaching, zinc electrowinning, and the manufacture of phosphoric acid. The presence of fluoride modifies the surface characteristics of minerals altering their effective flotation. Toxicity of fluoride to bacteria directly affects the mechanisms of bioleaching. Fluoride can interfere with the adhesion of metals to cathodes and affect deposit morphology during electrodeposition. In phosphoric acid synthesis from phosphate ores, fluoride affects production efficiency by altering the crystal morphology of the gypsum by-product. Keywords: bioleachingelectrowinningflotationfluoridehydrometallurgy
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