Electroflotation of fine hematite particles with Rhodococcus opacus as a biocollector in a modified Partridge–Smith cell

Abstract

In mineral recovery, the flotation of fine and ultrafine particles is poor, and the process is dependent on the bubble size and the hydrophobicity of the particles. This low recovery is mainly related to the low bubble/particle collision efficiency. However, this problem can be overcome by reducing the size of the bubbles. The electroflotation process is an attractive alternative for the concentration (recovery) of fine particles using hydrogen and oxygen bubbles smaller than 100 μm. In this context, the present work presents a study on the electroflotation of fine hematite particles in a modified Partridge–Smith cell using Rhodococcus opacus as a bioreagent and hydrogen or oxygen bubbles. The influence of the current density and system pH on bubble size of the hydrogen and oxygen was also evaluated with the aid of a bubble sizer equipment. The Sauter mean bubble diameter (d32) was found to range from 40 to 60 μm for the hydrogen bubbles and 50 to 70 μm for the oxygen bubbles. The hematite electroflotation tests were conducted in a modified Partridge–Smith electroflotation binary cell with 0.38 L usable volume. The process variables studied were the concentration of R. opacus, particle size, pH, and current density. The optimum pH value found for hematite flotation was around 6, and the higher hematite recovery values were about 80% and 65% with hydrogen and with oxygen bubbles, respectively.