Recycling process for recovery of gallium from GaN an e-waste of LED industry through ball milling, annealing and leaching

Basudev Swain, Chinmayee Mishra, Leeseung Kang, Kyung-Soo Park, Chan Gi Lee, Hyun Seon Hong
  • Environmental Research, April 2015, Elsevier
  • DOI: 10.1016/j.envres.2015.02.027

What is it about?

Waste dust generated during manufacturing of LED contains significant amounts of gallium and indium, needs suitable treatment and can be an important resource for recovery. The LED industry waste dust contains primarily gallium as GaN. Leaching followed by purification technology is the green and clean technology. To develop treatment and recycling technology of these GaN bearing e-waste, leaching is the primary stage. In our current investigation possible process for treatment and quantitative leaching of gallium and indium from the GaN bearing e-waste or waste of LED industry dust has been developed. To recycle the waste and quantitative leaching of gallium, two different process flow sheets have been proposed. In one, process first the GaN of the waste the LED industry dust was leached at the optimum condition. Subsequently, the leach residue was mixed with Na2CO3, ball milled followed by annealing, again leached to recover gallium. In the second process, the waste LED industry dust was mixed with Na2CO3, after ball milling and annealing, followed acidic leaching. Without pretreatment, the gallium leaching was only 4.91 w/w % using 4 M HCl, 100 oC and pulp density of 20 g/L. After mechano-chemical processing, both these processes achieved 73.68 w/w % of gallium leaching at their optimum condition. The developed process can treat and recycle any e-waste containing GaN through ball milling, annealing and leaching.

Why is it important?

For treatment and total recycling of the GaN waste of LED industry and e-waste containing GaN, the quantitative leaching goal can be achieved through pretreatment (mixed with Na2CO3 and ball milling) followed by oxidation through annealing. Based on pretreatment, annealing and leaching two different processes scheme have been proposed. In one process, scheme 1, first of all the indium of the waste LED industry dust was leached at the optimum condition. Subsequently, the leach residue was mixed with Na2CO3, ball milled followed by annealing, then again leached using the leach liquor to recover gallium and indium. In the second process, scheme 2, the waste LED industry dust was mixed with Na2CO3, after ball milling and annealing, followed the acidic leaching. Both the processes could achieve quantitative leaching. The proposed process in scheme 1 can be interesting environment friendly, techno economical process for quantitative leaching of the waste GaN of LED industry or e-waste containing GaN, Both the processes are competitive with each other, have the potential to be used in the industrial leaching process. The developed mechano-chemical process can treat and recycle any e-waste containing GaN through ball milling, annealing and leaching. After mechano-chemical processing, both these processes achieved 73.68 w/w % of gallium leaching at their optimum condition.

Perspectives

Dr Basudev Swain (Author)
Institute for Advanced Engineering (IAE)

 Simplest process for treatment of GaN an LED industry waste developed  The process developed recovers gallium from waste LED waste dust.  Thermal analysis and phase properties of GaN to Ga2O3 and GaN to NaGaO2 reveled.  Solid-state chemistry involved in this process reported.  Quantitative leaching of the GaN was achieved.

The following have contributed to this page: Dr Basudev Swain