The
traditional acid leaching process for releasing valuable metals
from spent lithium-ion batteries (LIBs) is inefficient and inevitably
consumes large amounts of reductants. In this study, a novel process,
based on a reduction thermal treatment and reductant-free acid leaching,
for recycling valuable metals from spent LIBs has been developed.
First, a thermodynamics calculation was performed to judge whether
the reducing reaction between LiCoO2 and graphite can occur
or not. Then, reduction thermal treatment experiments were conducted.
The process was tested by a thermogravimetry/differential thermal
analysis method, and reaction products were measured by X-ray powder
diffraction and X-ray photoelectron spectroscopy. The experimental
results agree well with thermodynamics analysis, and the desired CoO
and Li2CO3 were obtained under the optimum processing
conditions of 600 °C, 120 min, and molar ratio of LiCoO2 to graphite of 2:1. Finally, almost 100% Li and Co were easily leached
from the reaction product under the conditions of 2.25 M H2SO4, 80 °C, 30 min, and S/L = 100 g·L–1, and Co and Li in the leaching liquor were further separated with
35% PC88 at the ratio of aqueous to organic (A:O) equaling 0.5, 25
°C, and pH = 5.5. The proposed approach can not only make full
utilization of waste anode graphite, but also benefit leaching valuable
metals in the absence of reductant, which significantly improves the
economy and recovery performance of recycling spent LIBs.
During smelting, arsenic in copper concentrates affects the product quality and causes environmental pollution. Removing arsenic minerals from copper concentrates requires environmental-friendly and cost-effective depressants for flotation separation. Ca(ClO)2 was combined with sodium humate (SH) to improve the flotation separation of chalcopyrite from arsenopyrite. Results of single-mineral flotation indicated that combined Ca(ClO)2 and SH significantly inhibited arsenopyrite and exerted a negligible effect on chalcopyrite. The arsenic content in copper concentrates significantly decreased from 63% to 11% in the absence of a depressant and in the presence of Ca(ClO)2 and SH, as proven by the mixed-mineral flotation results. SH can adsorb on both mineral surfaces as indicated by the zeta potential measurements and Fourier transform infrared spectroscopy. However, the presence of Ca(ClO)2 increased the adsorption of arsenopyrite compared with chalcopyrite. The arsenopyrite floatability depressed with the Ca(ClO)2 oxidation and subsequent SH adsorption, as verified by X-ray photoelectron spectroscopy. Results of flotation tests confirmed that the chalcopyrite surface was slightly oxidized, but it remained hydrophobic. The combination of depressants has the potential for industrial application.
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