Abstract
LED lamps are becoming widespread across multiple industries owing to their power efficiency, flexible design and versatile applications. The LED market is increasing at a rapid pace globally in an attempt to reduce carbon emissions of lighting industry. At the same time, the volume of end-of-life LED lamps is increasing while still there is no viable technology for proper recycling of critical metals in these lamps. Characterization studies have shown that LED lamps are a rich source of gallium, with ten times higher Ga content than primary source. On the other hand, recycling gallium stands at less than 1 percent owing to difficulties in designing an economically feasible technology to extract gallium from secondary resource. So far, various metallurgical methods based on high temperature have been analyzed for Ga extraction from LED waste. However, there is still limited knowledge about hydrometallurgical methods of Ga extraction from GaN bearing waste such as LED lamps. In our study, we analyzed the efficiency of several leaching systems for Ga extraction from tube lamp strips. Leaching at both acidic and alkaline conditions with common reagents such as sulfuric acid, sodium hydroxide along with reductant and oxidant have been investigated to explore the extraction of deleterious elements (such as copper, aluminum and calcium) along with gallium. Moreover, performance of common acidophilic bacteria such as Acidithiobacillus ferrooxidans was assessed for Ga leaching. Organic materials of tube lamp strips were characterized using FTIR and crystalline phase and amorphous content of LED powder were identified by XRD technique. The results indicated promising performance of a sodium hydroxide pretreatment for Al removal which can potentially enhance Ga leaching in a subsequent step.