Transformer oil vs. kerosene: Selective collectors for C-matter flotation from a double refractory gold ore

Abstract

A study was performed to evaluate the effect of collector type on the flotation of carbonaceous matter (C-matter) from a refractory gold ore, with the objective of improving gold recovery through separate treatment of the flotation concentrate and tailings. Transformer oil and kerosene were investigated as C-matter collectors in a single rougher flotation stage. Both collectors were tested at varying dosages, with emulsification (‘emulsion’) and without emulsification (‘normal’) using a 2-level full factorial Design of Experiments (DOE). The kerosene emulsion at 500 g t-1 resulted in the highest C-matter recovery (66%) with a C-matter grade of 4.38% (∼2.4 times upgrade), showing improved flotation performance compared with normal kerosene. Normal transformer oil at 500 g t-1 resulted in a C-matter grade of 4.65% with 61% C-matter recovery, and emulsion of transformer oil had little effect on flotation performance. The finer droplet size in the kerosene emulsion resulted in a faster flotation rate, leading to higher C-matter recovery than both transformer and normal kerosene. However, FT-IR analysis demonstrated that the interaction of transformer oil with C-matter was different than kerosene, forming a stronger attachment to C-matter surfaces. The flotation concentrate obtained under the most promising conditions (kerosene emulsion 500 g t-1) contained 51 % of gold, while 49 % of the gold reported to the flotation tailings. The gold recovery models predicted that gold recovery from (1) roasting/cyanidation of the flotation concentrate and, (2) pressure oxidation/thiosulfate leaching of the flotation tailings, has the potential to improve the overall gold recovery from 44% to 60% (compared with pressure oxidation/thiosulfate leaching only). In its first application as a collector in C-matter flotation, transformer oil showed great potential despite the highly disseminated, complex nature of the ore. The results suggest that transformer oil may be applicable in other flotation systems, beyond the gold industry, including agglomerate flotation and the flotation of carbonaceous battery materials, such as graphite, from both primary and secondary resources.