Recovery of Gallium from Smartphones—Part II: Oxidative Alkaline Pressure Leaching of Gallium from Pyrolysis Residue

Abstract

In this article, we examine the selective hydrometallurgical extraction of gallium from pyrolyzed smartphones. Gallium-enriched pyrolysis residue originating from pyrolyzed smartphones was leached using NaOH and gaseous oxygen at elevated temperatures and pressures. The high content of organic carbon in the material strongly influenced the leaching performance. Oxygen, which is indispensable for the dissolution of gallium, also oxidized the organic carbon in the feed so that CO2 was released, which had a neutralizing effect on the alkaline solution. As a result, the CO2 formation complicated the accurate process control as the leaching temperature increased. The highest gallium yield of 82% was obtained at 180 °C, 5 g/L NaOH and 5 bar oxygen pressure. Decreased temperatures, NaOH concentrations and oxygen pressures resulted in lower leaching yields but with a higher selectivity for Ga. Temperatures higher than 180 °C resulted in extensive carbon oxidation, NaOH consumption and the coextraction of Cu and Ag. We propose that those conditions also facilitated the formation of water-soluble organic compounds, which would also influence the metal dissolution.

The Extraction and Separation of Scarce Critical Metals: A Review of Gallium, Indium and Germanium Extraction and Separation from Solid Wastes

“…After the pretreatment of the waste fiber optic cable, 98.3% of Ge could be leached using H 2 SO 4 and HF as leaching agents [90].CH 3 COOH was used to treat waste semiconductor diodes, and more than 70% of Ge was extracted [91]. The reaction of the leaching process is shown in Equations ( 23)- (26).…”

Extraction of Gallium from the Brown Corundum Dust with a One-Step Alkaline Leaching Process

“…The majority of gallium coexists with various minerals, the most important of which are bauxite, zinc ore and coal. Because it is uneconomical to extract gallium minerals alone, gallium is currently recovered primarily from secondary resources, such as solid or liquid waste from the Bayer process [6][7][8][9], coal fly ash [10,11], phosphorus dust [12], E-waste [13][14][15] and various tailings [16][17][18]. With the growth in global industries such as power electronics [19][20][21], semiconductors [22][23][24], medicine [25][26][27], aerospace [28,29], and so on, the use of gallium is becoming more and more widespread, and thus the market demand for gallium is expanding.…”

Particle Image Velocimetry Method for Prediction Hydrodynamic Conditions during Leaching Process on the Basis of Sn–NaOH System

“…Continuous technological progress requires deliveries of metals, of which the natural resources in the Earth’s crust are being successively depleted. Hence, a very important element of metallurgy consists in the effective recovery of metals from products withdrawn from use or from the process waste [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Metallic scrap most frequently comprises a few precious metals; therefore, methods for their recovery are of a many-stage and selective nature.…”