A sustainable process for selective recovery of metals from gallium-bearing waste generated from LED industry.

With the rapid development of the LED industry, gallium (Ga)-bearing waste generated is regarded as one of the most hazardous as it typically contains heavy metals and combustible organics. Traditional technologies are characterized by long processing routes, complex metal separation processes and significant secondary pollution emission. In this study, we proposed an innovative and green strategy to selectively recovery Ga from Ga-bearing waste by using a quantitative phase-controlling transition process. In the phase-controlling transition process, the gallium nitride (GaN) and indium (In) are converted to alkali-soluble gallium (III) oxide (Ga2O3) and alkali-insoluble indium oxides (In2O3) by oxidation calcination, while nitrogen is converted into diatomic nitrogen gas instead of ammonia/ammonium (NH3/NH4+). By selective leaching with NaOH solution, nearly 92.65% of Ga can be recycled with a leaching selectivity of 99.3%, while little emissions of NH3/NH4+. Ga2O3 with a purity of 99.97% was obtained from the leachate which is also economy promising by economic assessment. Therefore, the proposed methodology compared to the conventional acid and alkali leaching methods is potentially greener and more efficient process for extracting valuable metals from nitrogen-bearing solid waste.

Recycling Ag, As, Ga of waste light-emitting diodes via subcritical water treatment.

From environmental security and resource recovery viewpoint, hydrothermal technology was adopted to recycle Ag, As, and Ga from waste LEDs in present study. Waste LEDs packaging materials (Polyphthalamide (PPA), epoxy resin, and brominated flame retardant (BFR)), which are difficult to degrade under normal conditions, can be effectively decomposed through two steps of hydrothermal treatment. As and Ga were leached and silver was successfully recovered. Under the optimal process parameters (300 â„ƒ, 300r/min, 3% volume ratio of H2O2,400 min), the leaching rates of As and Ga are 98.4% and 80.5%, respectively. Ag and sapphire substrate were left and obtained together. Ag remains in the form of original metal, and almost no Ag ion was detected in the hydrothermal solution. In addition, As species in aqueous systems were simulated and inferred. The simulation results showed that As compounds that exist in the leaching solution is in liquid form and mainly exist as H2AsO4-. Under optimum processing conditions, almost 100% epoxy resin was decomposed. The degradation mechanism may be illuminated through the free radical reaction, and the possible decomposition pathways were speculated. The study proposed a process to recycle Ag, As, and Ga from scrapped LEDs and information could be useful for recycling other e-wastes.