Optimization of Reverse Cationic Flotation of Low-Grade Iron Oxide from Fluorspar Tails Using Taguchi Method

Abstract

Due to gradual depletion of high-grade iron ores, there is a need to investigate the treatment of low-grade iron ores. Current procedures are time and cost intensive. Batch laboratory scale reverse cationic flotation was employed to concentrate low-grade Fe ore, found in fluorspar tails in the form of hematite. This study used two types of depressants (soluble starch and dextrin) and two types of amines (primary mono-amine and tertiary mono-amine). Optimisation of the process investigated parameters such as pH, collector type and dosage, depressant type and dosage, conditioning time, solids content, agitation speed and air flow rate. Owing to the high number of experiments when all possible combinations are investigated, Taguchi design of experiment method was utilised to streamline the number of experiments and optimize parameters using orthogonal array and signal–noise ratio (SN). The SN was used to determine the optimum conditions and analyse the relative significance of parameters studied. The results showed that both depressants were efficient for hematite depression; however, soluble starch produced better results when compared to Betachem 30D. Both Betacol 373 and Dodecylamine collectors were efficient as quartz collectors; however, Dodecylamine produced better results when compared to Betacol 373. Ranking of parameter using SN ratio showed that pH was the most critical parameter in obtaining higher Fe grade concentrate and the optimum pH is 10. De-slimming leads to low recoveries during reverse flotation of iron ores. The main conclusion is that Taguchi method can be used to optimise a reverse cationic flotation process of a low-grade iron ore.