Recovery of critical and strategic metals from scrap marble-cutting tools by oxidative leaching and precipitation

• Published in: Separation and purification technology 2024-06, Vol.338, p.126424, Article 126424
• Main Authors: Celep, Oktay, Ahlatci, Firat, Yener Yazici, Ersin, Deveci, Haci
• Format: Article
• Language: English
• Subjects: Cobalt; Critical raw material; Cutting-tools; Leaching; Recycling
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2024.126424

•Scrap segments offer resource potential for base, precious and critical metals.•Oxidative acid leaching can be suitably used to extract Co, Cu, and Ag from scraps.•Temperature, H2O2 and H2SO4 are all significant parameters affecting the leaching.•Selective leaching of metal from scraps is possible under suitable conditions.•Metals can be selectively recovered from pregnant leach solutions. Scrap marble-cutting tool segments (SMCTSs) generated within marble-cutting applications can be regarded as an important secondary resource owing to their high content of base/precious/critical metals (i.e. Co, Cu and Ag) as well as synthetic diamonds. In this study, sulphuric acid-hydrogen peroxide leaching of copper cobalt and silver from SMCTSs was studied using the central composite design for experiments. Extractions of cobalt (≥73.8 %) and iron (≥86.6 %) were more extensive than copper (≤78.3 %) and silver (≤35.1 %), linked with their relative nobilities. Data analysis has confirmed that increasing the acid concentration or temperature enhances the leaching of metals. Copper and silver leaching improves with H2O2 concentration, while high cobalt and iron leaching can be readily achieved without H2O2. Silver was selectively precipitated (98.9 %) as AgCl with 8.8 % Cu and 0.7 % Co losses from the leach solution. Copper and cobalt were also recovered selectively by increasing the pH to 5.5 and 8.5 respectively after the removal of iron at pH 3.5. These findings have revealed that cobalt, copper, and silver could be selectively recovered by the proposed leaching and precipitation approaches from SMCTSs.