Recovery of Critical Metals from Leach Solution of Electronic Waste using Magnetite Electrospun Carbon Nanofibers Composite

Scarcity in mining and geo-political direction diverts attention toward critical metals recycling. Gallium (Ga), Indium (In) and Germanium (Ge) are among the critical metals consume approximately 80 percent of its world mining in innovative production of electrical and electronic equipment. The fast obsolescing rate generate large amount of electronic waste, which is now seen as secondary reservoir for critical metals. These metal resources need to be dealt with effective recycling capabilities. Based on solid phase extraction, magnetic nano-hydrometallurgy is opening a new area of metallic contents recovery in conventional hydrometallurgy. In the present work, polyacrylonitrile (PAN) based electrospun nanofibers were synthesized and carbonized at 800°C in the inert environment. After surface oxidation, carbon nanofibers were decorated with magnetite particles through co-precipitation. The saturation magnetization value (Ms = 23.6emu/g) confirm high loading of magnetite particles. The selected critical metal ions are freely present in aqueous solution at pH 1 to 3, thus highest removal efficiency was observed at pH 2. Pseudo second order kinetics confirm the chemical/charges interaction between sorbent and sorbate ions. Maximum sorption capacity calculated through Langmuir isotherm was 226, 191, 171 mg/g for Ge(IV), Ga(III) and In(III) metal ions, respectively. The R L value (0 1) indicate favourable sorption process. The sorbed target metal ions were collectively eluted using 1mol/L hydrochloric acid. The preconcentration factor was calculated 1080 for Ge(IV) and In(III) while 1260 for Ga(III). The method was validated with 5µg/mL spiked multi-element standards and applied to multiple acid leached electronic waste samples like PCBs, waste LCD panels and solar panels etc. Recoveries in the range of 96.2% for Ga(III), 95.6% for In(III) and 97.4% for Ge(IV) in the presence of diverse ions indicate the suitability of the proposed method for target metal ions even in complex matrix.