Recycling of GaN, a Refractory eWaste Material: Understanding the Chemical Thermodynamics

Abstract

South Korea is a major producer of light‐emitting diode (LED) material, contributing 31% of total LED demand worldwide, and also a major consumer of electronic devices. During manufacturing and after end of life (EOL) of the consumer electronics, significant amount of GaN‐bearing waste is being generated. As the Republic of Korea depends upon the import of all mineral commodities, under the national policy of securing a stable supply, much attention has been paid to the notion of “urban mining.” The stringent international environmental directive for recycling of waste electrical and electronic equipment (WEEE), United Nations Environment Programme (UNEP) E‐Waste Management goal, restriction of the use of hazardous substances in EEE (RoHS), and extended producer responsibility (EPR) have made recycling an important responsibility. Recovery of the gallium from GaN‐bearing waste can be a promising feasible option; simultaneously from the waste, the wealth can be generated. As GaN is a refractory material, which is hard to leach in the recovery process, hence, needs a chemical pretreatment. In this study, thermodynamics of GaN oxidation and oxidative roasting using Na2CO3 has been studied. Thermodynamic feasibility for leaching of oxidized GaN either through acidic leaching or through alkali leaching has been explored.

Recycling of Gallium from End-of-Life Light Emitting Diodes

“…It was thermodynamically established by Ellingham and Pourbaix diagrams that the GaN can be transformed into soluble NaGaO 2 by oxidative roasting in presence of Na 2 CO 3 [14]. Our own thermodynamic calculations using HSC Chemistry 5.0 Software fully proved that.…”

Recovery technologies for indium, gallium, and germanium from end-of-life products (electronic waste) – A review

“…One such method is the chemicalthermal treatment with mechanochemical activation, which involves the use of the alkaline salt Na2CO3. This treatment can convert GaN into soluble NaGaO2 in the presence of Na2CO3 with annealing, as reported by Swain et al (2016b). Nagy et al (2017) have also proposed a chemical-thermal treatment with Na2CO3 that can improve the gallium leaching efficiency.…”

Solution Growth of Screw Dislocation Driven α-GaOOH Nanorod Arrays and Their Conversion to Porous ZnGa2O4 Nanotubes

“…Therefore, the observed disparity in morphology of the converted ZnGa 2 O 4 products has to be due to the different structures and properties of the α-GaOOH and α-Ga 2 O 3 precursors. The α-GaOOH is amphoteric and could dissolve in alkaline solutions to form soluble [Ga­(OH) 4 ] − (for reference, see the Pourbaix diagram of the Ga–O–H 2 O system), which would subsequently react with Zn 2+ ions to form ZnGa 2 O 4 nanocubes. Thus, the reaction between α-GaOOH and Zn­(CH 3 COOH) 2 could proceed as follows: …”