No abstract

In this work, an eco-friendly and hydrometallurgical process for the recovery of cobalt and lithium from spent lithium-ion batteries has been proposed, which includes pretreatment, citric acid leaching, selective chemical precipitation and circulatory leaching. After pretreatment (manual dismantling, N-methyl pyrrolidone immersion and calcination), Cu and Al foils are recycled directly and the cathode active materials are separated from the cathode efficiently. Then, the obtained cathode active materials (waste LiCoO2) was firstly leached with 1.25 mol l(-1) citric acid and 1 vol.% H2O2 solution. Then cobalt was precipitated using oxalic acid (H2C2O4) under a molar ratio of 1:1.05 (H2C2O4: Co(2+)). After filtration, the filtrate (containing Li(+)) and H2O2 was employed as a leaching agent and the optimum conditions are studied in detail. The leaching efficiencies can reach as high as 98% for Li and 90.2% for Co, respectively, using filter liquor as leaching reagent under conditions of leaching temperature of 90°C, 0.9 vol.% H2O2 and a solid-to-liquid ratio of 60 ml g(-1) for 35 min. After three bouts of circulatory leaching, more than 90% Li and 80% Co can be leached under the same leaching conditions. In this way, Li and Co can be recovered efficiently and waste liquor re-utilization is achievable with this hydrometallurgical process, which may promise both economic and environmental benefits.

The bioleaching behaviors of chalcopyrite with two different metallogenic types by iron- and sulfur-oxidizing Sulfobacillus thermosulfidooxidans were investigated. It was found that the skarn-type chalcopyrite (STC) exhibited much faster leaching rate and the copper extraction was 33.34% after 21 days of biooxidation, while that of the porphyry-type chalcopyrite (PTC) was only 23.53%. The reasons were explained from the perspective of mineralogy. The analysis of XRD indicated that STC had slightly larger cell parameters than PTC. More stepped and bulgy structures were observed on the STC surface, as displayed in SEM images. The XPS spectra showed that copper on the surfaces of the two types of chalcopyrite mainly existed in the form of Cu(I), and STC had much higher copper content and lower Cu 2p3/2 binding energy than PTC. These differences in mineralogy resulted in the more excellent bioleaching kinetics of STC. This study is pretty useful in understanding the relation between the bioleaching behaviors of chalcopyrite and the mineralogical properties.