Flotation of coarse and fine pyrochlore using octyl hydroxamic acid and sodium oleate

Abstract

The flotation of pyrochlore using two common oxide collectors, octyl hydroxamic acid (OHA) and sodium oleate (NaOl), was studied by microflotation tests on high purity pyrochlore sample and batch flotation tests on a pyrochlore ore sample. The high purity pyrochlore sample was screened into different size fractions, −20 µm, −38 + 20 µm, −75 + 38 µm, −125 + 75 µm, and +125 µm and used in separate microflotation tests. The pyrochlore ore sample was floated as a whole in batch flotation but the flotation concentrate as well as the feed were screened into −20 µm, −38 + 20 µm, −75 + 38 µm, and −150 +75 µm to find the grade and recovery in each size fraction. The microflotation showed that under the same pH and collector concentration, OHA floated the −20 µm and −38 + 20 µm pyrochlore more strongly than NaOl. This phenomenon was also observed in batch flotation of the pyrochlore ore sample, where under the same pH and collector dosage either weight based (g/t) or molar based (mol/t), the OHA recovered pyrochlore from the −20 µm size fraction with higher enrichment ratio and higher mass pull than NaOl. The adsorption of NaOl and OHA on the pyrochlore surface was examined by Fourier transform infrared spectroscopy (FTIR), zeta potential and X-ray photoelectron spectroscopy (XPS) analyses. FTIR and zeta potential measurements indicated that both collectors adsorbed on pyrochlore through chemisorption followed by physisorption, and XPS electron binding energy and depth profile analyses showed that the OHA may have a stronger chemical affinity to pyrochlore than NaOl, contributing to the stronger chemisorption. The different adsorption mechanisms were linked to the flotation results, pointing to the role of chemisorption strength on fine particle flotation recovery.