Rapid leaching and recovery of valuable metals from spent Lithium Ion batteries (LIBs) via environmentally benign subcritical nickel-containing water over chlorinated polyvinyl chloride

This study presents the development of an effective and environmentally friendly method to leach and to recover valuable metals, such as lithium (Li) and cobalt (Co) from the spent lithium-ion batteries (LIBs) using subcritical water assisted by nickel catalyst and waste chlorinated polyvinyl chloride (CPVC). The effects of reaction parameters, such as Ni²⁺ concentration, temperature, time, and liquid-solid ratio on the leaching efficiencies of Li and Co were carefully investigated. The solid residues obtained thereof were characterized by XRD and SEM-EDS analyses, while the leachates were analyzed by ICP-OES. The ICP-OES results showed that about 99.05% of Li and 98.08% of Co were effectively leached from the spent LiCoO₂ powder under the following optimized reaction conditions: temperature of 240 °C, reaction time of 40 min, Ni²⁺ concentration of 0.04 M, and the liquid-solid ratio of 25:1 mL/g, respectively. Finally, based on the precipitation method, the Li and Co were recovered from the leachate as Li₂CO₃ and Co(OH)₂. The results and the method applied in this research suggest that the leaching and recovery of Li and Co from the spent LIBs using subcritical nickel-containing water is an inexpensive, efficient, sustainable and eco-friendly technology.

Sugars and char formation on subcritical water hydrolysis of sugarcane straw

Subcritical water has potential as an environmentally friendly solvent for applications including hydrolysis, liquefaction, extraction, and carbonization. Here, we report hydrolysis of sugarcane straw, an abundant byproduct of sugar production, in a semi-continuous reactor at reaction temperatures ranging from 190 to 260°C and at operating pressures of 9 and 16MPa. The target hydrolysis products were total reducing sugars. The main products of sugarcane straw hydrolysis were glucose, xylose, arabinose, and galactose in addition to 5- hydroxymethylfurfural and furfural as minor byproducts. Fourier transform infrared spectroscopy and thermogravimetric analysis provided additional information on the surface and bulk composition of the residual biomass. Char was present on samples treated at temperatures equal to and greater than 190°C. Samples treated at 260°C contained approximately 20wt% char, yet retained substantial hemicellulose and cellulose content. Hydrolysis temperature of 200°C provided the greatest TRS yield while minimizing char formation.