Abstract
Lithium resources face risks of shortages owing to the rapid development of the lithium industry. This makes the efficient production and recycling of lithium an issue that should be addressed immediately. Lithium bromide is widely used as a water-absorbent material, a humidity regulator, and an absorption refrigerant in the industry. However, there are few studies on the recovery of lithium from lithium bromide after disposal. In this paper, a bipolar membrane electrodialysis (BMED) process is proposed to convert waste lithium bromide into lithium hydroxide, with the generation of valuable hydrobromic acid as a by-product. The effects of the current density, the feed salt concentration, and the initial salt chamber volume on the performance of the BMED process were studied. When the reaction conditions were optimized, it was concluded that an initial salt chamber volume of 200 mL and a salt concentration of 0.3 mol/L provided the maximum benefit. A high current density leads to high energy consumption but with high current efficiency; therefore, the optimum current density was identified as 30 mA/cm2. Under the optimized conditions, the total economic cost of the BMED process was calculated as 2.243 USD·kg−1LiOH. As well as solving the problem of recycling waste lithium bromide, the process also represents a novel production methodology for lithium hydroxide. Given the prices of lithium hydroxide and hydrobromic acid, the process is both environmentally friendly and economical.
Highlights
Lithium is the lightest alkali metal and shows excellent performance and wide applicability in batteries, ceramics, glass, and lithium-based lubricating oils, among other things [1,2]
The current density is the most important factor affecting the energy consumption and the efficiency of bipolar membrane electrodialysis (BMED) processes, so a current density in the range of 10–50 mA/cm2, commonly used in BMED processes, was selected for use in the research [28,30], and the initial concentration of the salt chamber was fixed at 0.3 mol/L according to the pretreatment
Bipolar membrane electrodialysis technology was used to treat waste lithium bromide. It allowed the conversion of lithium bromide into lithium hydroxide and hydrobromic acid without the need for other reagents
Summary
Lithium is the lightest alkali metal and shows excellent performance and wide applicability in batteries, ceramics, glass, and lithium-based lubricating oils, among other things [1,2]. The main method adopted for the industrial production of lithium hydroxide involves roasting spodumene with sulfuric acid, adding sodium hydroxide and soda ash to neutralize the excess sulfuric acid and remove impurities. This is converted into lithium hydroxide [11,12]. The limitations of this method are that it consumes large amounts of raw materials and generates low-purity sodium sulfate, which needs to be processed further. The development of an efficient and eco-friendly method for the conversion of waste lithium bromide into lithium hydroxide could solve the problem of the environmental hazards of the waste lithium bromide and establish a novel economic production process for lithium hydroxide by converting the downstream waste lithium bromide back into the upstream lithium hydroxide
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