Application of cupric or ferric ions as environmentally benign oxidants to the chloride leaching of platinum from spent reforming catalysts. (1st July 2023)

• Record Type: Journal Article
• Authors: Kazemi, Mahsa; Hosseini, Mohammad Raouf; Zamaniyan, Akbar; Ahmadi, Ali
• Is Part Of: Journal of environmental management. Volume 337(2023)
• Publication Date: 2023-07-01
• Subjects: Catalyst -- Chloride leaching -- Cupric -- Ferric -- Platinum -- Metal recovery; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2023.117768
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Recovery of precious metals has been considered due to their limited availability and resources, and the reduction of environmental hazards. In this study, the environmentally friendly chloride leaching method was used to recover platinum (Pt) from a spent reforming catalyst. Hydrochloric acid and sodium chloride were applied as the complexing agent and ferric or cupric chloride (FeCl3, CuCl2 ) was used as oxidants. Response surface methodology was implemented to investigate the influences of acid concentration (1–3 M), oxidant concentration (0.5–1.3 M), and temperature (70–90 °C) on the Pt extraction at a fixed duration of 3 h using two separate Box-Behnken experimental designs. Increasing temperature and acid concentration improved the Pt recovery from ∼52% to ∼89% in the presence of 1 M FeCl3, and from ∼29% to 94% in the presence of 0.75 M CuCl2 . Generally, at low acid concentrations, ferric chloride was more efficient in Pt dissolution, while, at high acid concentrations, cupric chloride performed better. Finally, the platinum content of the pregnant leach solution was precipitated by adding a saturated ammonium chloride solution. According to the results of the X-ray diffraction analysis, the obtained precipitate was mainly composed of ammonium hexachloroplatinate, sodium chloride, and ammonium chloride. Also, the Pt assay of the powder was determined as 21%. Highlights: Platinum was recovered from a petroleum refining catalyst through chloride leaching. HCl and NaCl were used as complexing agent and ferric or cupric chloride as oxidants. Fe 3+ and Cu 2+ ions performed better at low and high acid concentration, respectively. Increasing the temperature and acid concentration improved the platinum recovery. (NH₄)₂[PtCl₆] was precipitated from the PLS by adding ammonium chloride.