Control of Residual Sulfides in Flotation Tailings of Cu-Ni Duluth Complex via Grinding Media Selection

Abstract

The effects of grinding media chemistries on ball wear and flotation were compared by grinding a Cu-Ni bearing Duluth Complex sample using forged steel and 27% Cr cast iron balls under nitrogen, air and oxygen atmospheres. Both types of balls increased their wear in air and oxygen atmospheres, but Cr balls wore only one-third as much as forged steel balls. The wear increased roughly in proportion to the oxygen content of the mill atmosphere. Flotation recoveries of sulfide minerals were adversely affected when the sample was ground in a nitrogen atmosphere. Residual sulfur in flotation tailings ground using both types of grinding balls under an air or oxygen atmosphere was lowered to about 0.15%, with Cr balls producing somewhat lower sulfur values. Davis magnetic tube tests on flotation tailings lowered the residual sulfur to 0. 1 % or less by recovering mainly pyrrhotite. PGM recoveries paralleled the recoveries of sulfur, although Pd recoveries remained somewhat lower, implying that a part of Pd might be associated with pyrrhotite. Pd, not recovered in flotation, appeared to be recovered by magnetic separation of flotation tailings.