Publications Repository - Gdańsk University of Technology

Metal extraction has proven to be an effective solution for recovering metal resources and addressing heavy metal pollution. Deep eutectic solvents (DESs) are receiving great attention for metal recovery because of their high selectivity, environmentally friendly character, low melting point, good stability, and low corrosive properties. Particularly, natural deep eutectic solvents (NADESs) and hydrophobic DESs (HDES) have been extensively studied for many applications. This paper reviews the recent progress in the application of DESs in the extraction of metals, the mechanisms of metal extraction, and the separation of metals from DES. DES extraction of metals was effective for minerals, solid wastes, and other sources such as waste lithium-ion batteries, waste circuit boards, waste permanent magnets, industrial wastes (blast furnace dust, copper converter slag, spent hydrogenation catalysts). DESs are capable of extracting metals also from contaminated wastewater and soil, solving the metal pollution issue. Effective applications were developed for recovery of boron, cobalt, copper, gold, iron, indium, lithium, lead, nickel, neodymium, palladium, samarium, and zinc. The optimum pH for extracting metals by DES is generally the highest pH at which hydroxides are not formed. Typically, DES-based processes provide above 90% (often above 97%) recovery of metals from the primary resource. Improvement of performance can be obtained by microwaves or ultrasound assisted processes. This review also summarizes and analyzes the mechanisms of metal extraction by DESs, methods for metal recovery from DESs, and the regeneration and reuse of DESs. The DES extraction mechanisms of metals include protonation, reduction, metal complexation and coordination. The methods for separating metals from DES mainly include anti-extraction, electrodeposition, displacement, and co-precipitation. The strengths and challenges in this field are also systematically analyzed.

Authors

• Chongqing Wang,
• Zhenxing Zhou,
• Xiuxiu Zhang,
• Hui Guo,
• dr hab. inż. Grzegorz Boczkaj link open in new tab