The flotation separation of pyrite from serpentine using lemon yellow as selective depressant

New insights into the aggregation and disaggregation between serpentine and pyrite in the xanthate flotation system

HYPOTHESIS

In xanthate flotation system, the aggregation of serpentine on sulfide minerals significantly weakened their floatability. And it was generally assumed that the electrostatic attraction was of the dominant driver for coating of serpentine slimes. In this paper, the hydrophobic interaction between the "talc-like" cleavage plane of serpentine and the xanthate-hydrophobized surface of sulfide minerals was proposed as the dominated driver.

EXPERIMENTS

To evaluate the aggregation of serpentine on pyrite surface, a novel experimental protocol was designed, and the aggregation behavior and mechanism in the absence and presence of sodium isobutyl xanthate (SIBX) were explored through in situ optical microscope, micro-flotation, contact angle, zeta potential and FT-IR. Afterwards, the disaggregation mechanism of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) to the aggregates of serpentine on pyrite surface was revealed.

FINDINGS

The electrostatic attraction facilitated the slight aggregation of serpentine slimes on bare pyrite surface. The hydrophobic interaction between the "talc-like" plane of serpentine and SIBX-covered pyrite significantly promoted the aggregation between them, which remarkably weakened the floatability of pyrite. The attendance of HEDP anions reversed the surface potential of the octahedral Mg-O layers of serpentine from the positive into the negative, thus to prevent the aggregation of the HEDP-anchored serpentine with the SIBX-covered pyrite via the strong electrostatic repulsion between them. As a result, the disaggregation as well as SIBX flotation separation of pyrite from serpentine was realized. This investigation also provided new insights into the aggregation and disaggregation between serpentine and sulfide minerals during froth flotation.

Enhancing flotation separation of chalcopyrite and magnesium silicate minerals by surface synergism between PAAS and GA

Separation effects of sodium polyacrylate (PAAS) and gum Arabic (GA) on flotation of chalcopyrite and magnesium silicate minerals using potassium butyl xanthate (PBX) as collector were investigated by micro-flotation experiments, zeta potential, Infrared spectral (IR), SEM-EDS, XPS analysis and copper sulphide ore beneficiation test. The micro-flotation experiments and zeta potential measurements showed that combined depressant consisting of PAAS and GA could efficiently reduce the recoveries of mixed minerals of serpentine and talc more than 25%, while that of chalcopyrite remained above 70% at pH 9.2. Infrared spectral (IR), SEM-EDS and XPS analysis showed that PAAS chemically reacted with Mg on the surface of serpentine, while GA adsorbed on talc surface mainly via physical interaction and hydrogen bond may also play a role. Surface synergism between PAAS and GA was investigated by turbidity test and its depression mechanism was proposed. The technology feasibility of using PAAS and GA to improve the copper sulphide ore flotation performance was verified through artificial mixed ore flotation and laboratory closed-flotation operation.