GOLD RECOVERY BY FROTH FLOTATION PROCESS USING CONVENTIONAL AND LOCALLY-SOURCED FROTHERS AND COLLECTORS

Abstract

Sustainable mineral resources development encompasses techno-economic viability; value addition chain, health, safety and environment (HSE). Physicochemical processing of minerals by way of froth flotation is generally eco-friendly. When froth flotation reagents are eco-friendly but are scarce and expensive, locally-sourced and affordable flotation reagents is a worthwhile research effort. This is the basis for this research work which is aimed at ascertaining the possibility of replacing the conventional flotation reagents – methyl isobutyl ketone (MIBK) as frother and potassium ethyl xanthate (PEX) as collector with locally-sourced reagents – groundnut oil, palm kernel oil and shea butter as frothers and the respective metal soaps as collectors by characterizing the reagents and studying the recovery. The acid values, saponification values, iodine values and peroxide values of the locally sourced frothers were determined using standard methods. The locally-sourced collectors were prepared by reacting the locally-sourced oils with hydroxides of sodium, potassium, barium and aluminium. Foaming capacity and foaming stability tests were carried out on the oils, particle size analysis was carried out on Igun placer gold ore sample from Ilesha gold field in Southwest Nigeria and the ore sample was concentrated using a shaking table prior to the froth flotation. The froth flotation experiment was carried out on the ore using the conventional reagents varying particle size, pulp density, pH and collector concentration; and using the locally-sourced reagents. The results of this research show the physicochemical properties of groundnut oil, palm kernel oil and shea butter: Acid values are 0.26±0.07, 12.23±0.11 and 2.73±0.07 mgKOH/g; the saponification values are 239.73±5.18, 297.33±5.14 and 222.53±9.80 mgKOH/g; the iodine values are 8.77±0.68 mgKOH/g, 1.48±1.56 mgKOH/g and 5.08±1.00 mgKOH/g while the peroxide values for groundnut oil and shea butter are 7.6±3.39 mEq/kg and 5.67±3.44 mEq/kg respectively. The foaming capacity for the metal soaps range from 37.17 – 265.38% with the lowest value by the sodium soap of shea butter and the highest value by the potassium soap of groundnut oil. The foaming stability values for the metal soaps range from 41.67 – 95.75% with the lowest value by the sodium soap of palm kernel oil and the highest by the potassium soap of shea butter. This study provides information about the effect of particle size, pulp density, pH and collector concentration on the percentage gold concentrate recovery using conventional reagents. The highest percentage gold concentrate recovery for the conventional reagents was 95.51% while the highest recovery for the locally-sourced reagents was 38.76%. The results of foaming capacity and foaming stability tests show that groundnut oil, palm kernel oil and shea butter as frothers and their sodium and potassium metal soaps as collectors have the potential to be used in the froth flotation process but more work needs to be done in order to optimise the percentage gold concentrate recovery.