title: Recovery of platinum from spent catalysts by liquid-liquid extraction in chloride medium.
abstract: This work examines a hydrometallurgical route for processing spent commercial catalysts (Pt and PtSnIn/A(2)O(3)) used in Brazilian refineries for recovery of the noble metal with less final wastes generation. Samples were initially pre-oxidized (500 degrees C, 5 h) in order to eliminate coke. The basis of the present route is the partial dissolution of the pre-oxidized catalyst in aqua-regia. Temperature and time necessary to dissolve all platinum were optimized in order to reduce the operation severity and aluminum solubilization. All platinum and 16-18 wt.% of aluminum were dissolved at 75 degrees C in 20-25 min. Separation of platinum from the acidic solution was accomplished by solvent extraction. The best extractant (> 99 wt.%) was Aliquat 336 (a quaternary ammonium salt) in one stage (A/O phase ratio = 1, v/v). Platinum was stripped (> 99.9 wt.%) in one stage (A/O phase ratio = 1, v/v) with aqueous sodium thiosulfate (> or = 0.75 mol L(-1)). Black platinum was obtained from this solution via reduction with magnesium or ascorbic acid.
authors.affiliation: Analytical Chemistry Department, Institute of Chemistry, Federal University of Rio de Janeiro. Av. Athos da Silveira Ramos, 149, room A509, 21941-909, Ilha do Fundão, Rio de Janeiro, Brazil.
authors.forename: Roberta Santos
authors.initials: RS
authors.lastname: Marinho
authors.forename: Julio Carlos
authors.initials: JC
authors.lastname: Afonso
authors.forename: José Waldemar Silva Dias
authors.initials: JW
authors.lastname: da Cunha
mesh_terms: D000535:Aluminum / Q000737:chemistry; D002384:Catalysis; D002712:Chlorides / Q000737:chemistry*; D006851:Hydrochloric Acid; D007202:Indicators and Reagents; D007700:Kinetics; D008670:Metals / Q000737:chemistry; D017942:Nitric Acid; D010084:Oxidation-Reduction; D010984:Platinum / Q000737:chemistry* / Q000302:isolation & purification; D012995:Solubility; D012996:Solutions; D013696:Temperature; D014867:Water / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D002712:Chlorides; D007202:Indicators and Reagents; D008670:Metals; D012996:Solutions; D014867:Water; D017942:Nitric Acid; D010984:Platinum; D000535:Aluminum; D006851:Hydrochloric Acid; C022102:aqua regia