Valuable metal recovery from waste tantalum capacitors via cryogenic crushing-alkaline calcination-leaching process
Longgong Xia, Xue Wei, Hongjun Wang, Fengchun Ye, Zhihong Liu
Abstract
The development of tantalum capacitor (TC) industry is associated with the production of one technology metal-tantalum (Ta). The recycling of waste tantalum capacitors (WTCs) is an important strategy for the sustainable development of tantalum related industries. A cryogenic crushing-alkaline calcination-leaching process has been proposed and experimentally studied in the present work, and main results showed: 1) after the refrigeration treatment with liquid nitrogen, WTCs got discharged and became brittle. Three groups of materials could be produced after the milling - magnetic separation - screening treatment, and portions of collected iron-nickel alloy, tantalum wire, and Ta bearing powder were 6.94%, 1.50%, and 91.56%, respectively; 2) organic components in Ta-bearing powder could be efficiently removed in the alkaline calcination process, and Si converted to Na2O·mSiO2 (m = 1, 2), which could be easily leached with water; 3) NaOH was selected to be the alkaline for calcination reactions, and the optimized temperature was 700 °C, the reacting time was 300 min, and the NaOH excess coefficient was 1.0; 4) water leaching residue was treated with nitric acid, and Ag, Fe and Ni could be enriched in the leaching liquor, and the overall recovery of Ta was 96.72% at optimized conditions.