Choline-Chloride-Based Deep Eutectic Solvents in Sulfide Metallurgy: A Systematic Review of Mineral-Specific Dissolution, Selectivity, Metal Recovery, and Reported Process Sustainability

Deep eutectic solvents (DES) have been investigated for processing sulfide minerals, concentrates, mattes, and model sulfides through chemical, oxidative, and electrochemical routes, but the evidence is dispersed across mineralogies, formulations, and non-comparable metrics. This systematic review examined how mineral species, DES composition, and operating conditions influence dissolution, selectivity, metal recovery, and reported sustainability indicators; the available evidence concerns choline-chloride-based systems. Scopus and Web of Science Core Collection were searched on 7 September 2026, with a supplementary search adding mineral names on 8 October 2026, for articles published from 2010 to 7 September 2026. Two reviewers independently screened records, reconciled by consensus, and classified study outcomes blind to each other; one reviewer extracted data. Reporting followed PRISMA 2020; the review was not registered. Evidence was synthesized descriptively without pooling. Of 694 unique records, 40 reports were assessed, and 34 studies were included; all tested at least one choline chloride formulation. Endpoints were not comparable: Cu extraction from chalcopyrite concentrate reached 73.6% and 83.9% under different conditions, whereas 96.58% for Cu2S conversion was a current efficiency, not an extraction yield. Selectivity was quantified in 14 studies. Quantitative water content was reported in six studies and deliberately varied in three. No risk-of-bias assessment was performed, and three reports were not retrieved. Dissolution alone established neither selectivity nor sustainability, and conclusions apply to choline-chloride-based systems rather than to DES generally.