A study of selective flotation recovery of rare earth oxides from hematite and quartz using hydroxamic acid as a collector

Abstract

Monazite is a major rare earth elements (REE)-bearing phosphate mineral predominantly found in association with hematite and quartz in some Australian rare earth deposits. The flotation of rare earth oxides (REO) in monazite from mixtures containing monazite, hematite, and quartz with hydroxamic acid as a collector has been investigated using an IMN microflotation cell and a 1.2 L Denver flotation cell. Maximum flotation recovery of both monazite and hematite was attained at pH 7, whereas that of quartz, at pH 3. The flotation kinetics data indicated the need for depressants to achieve selective REO recovery from hematite and quartz mixtures. Sodium silicate and starch were thus tested as depressants of both hematite and quartz. The separation efficiency of REO in the absence of depressants was low and averaged 6.42% at 99% REO recovery, but could be increased to 44.78% with corresponding 93% REO recovery when 4000 g/t starch was used. However, the efficiencies of REO separation obtained with sodium silicate were generally lower (<18%), due to higher gangue minerals content in the flotation concentrates. A blend of sodium silicate and starch showed a good performance for REO recovery, with enhanced selectivity against hematite and quartz through a rougher-cleaner flotation test. This study presents the feasibility of upgrading REO from iron-oxide rich tailings using hydroxamic acid, in the presence of sodium silicate and starch as depressants.