Investigating the selective flotation of auriferous arsenian pyrite from refractory ores using thionocarbamate

Abstract

Thionocarbamate, specifically modified Isopropyl Ethyl Thionocarbamate (IPETC) is selective in the separation of pyrite from arsenopyrite, following copper activation. In this work, the flotation response of a refractory gold (Au) ore containing arsenic (As) mainly in the form of arsenian pyrite is investigated to reject gold-barren sulphidic phases. The recovery of Au increased with an increase in CuSO4 concentration to 0.3 kg/t, beyond which further increase in concentration yielded no significant recovery. Variations of IPETC concentration between 0.2 and 1.5 kg /t of ore influenced both gold and arsenic recovery. It was surmised that the high collector dosage may have resulted from competitive adsorption between arsenian pyrite and other gangue minerals in the ore. 0.3 kg/t CuSO4 and 1.2 kg/t IPETC concentration at pH 11 gave the best results of 86% Au and 83% As recovery at an Au and As grade of 8.14 g/t and 2436 ppm respectively. LA-ICP-MS analysis of the concentrate showed a positive correlation between gold and arsenic. The technique also revealed arsenic-rich zones in pyrite which was further confirmed by SEM/BSD imaging to be rims of arsenian pyrite encapsulating Au-barren pyrite. MLA mineral maps of concentrates obtained at different times also showed that there is no relationship between the arsenic content of pyrite and the flotation rate. The deportment of arsenic in the rims of pyrite presents a complex mineralogical association which results in a decrease in concentrate grade.