Recovery of platinum from spent catalysts by liquid-liquid extraction in chloride medium.
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.
Marinho
Roberta Santos
RS
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.
Afonso
Julio Carlos
JC
da Cunha
José Waldemar Silva Dias
JW
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
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