Determination of the Optimum NiS Fire Assay Parameters FOR Platinum in Catalytic Converters

Abstract

The nickel sulfide (NiS) fire assay has been used to quantify, platinum (Pt) in catalytic converters. The use of various flux materials and the effects of different parameters such as quantity of flux, flux mixture ratio (i.e. B2O3:Na2O ratio) and temperature were compared on Pt recovery. The fire assay buttons were characterized using different techniques such as Atomic absorption spectrometer (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). We found that the optimum condition to recover Pt was achieved with the use of 57.5 g flux (sodium tetraborate + sodium carbonate), 5 g Ni (as 6.36 g NiO), and 5 g S° per five gram of sample at 900°C. The recovery of Pt after an hour was, 95%. It is proposed that a method to isolate at least 95% of the Pt present in catalytic converters using NiS fire assay.