The Effect of High Intensity Conditioning on Surface Oxidation with Processed Sudbury Nickel Ore

• Author / Creator

  Malainey, Jonathan D.

• In the Sudbury Basin, froth flotation is commonly used to recover Pentlandite (Pn), and Chalcopyrite (Cp), while rejecting Pyrrhotite (Po), and other gangue minerals typically found in the region. However, as the sulfide minerals flow through the plant the surfaces continually oxidize, allowing hydrophilic species to form on the surface. Thus, the selectivity of Pn, Cp and Po during flotation separation in a plant is reduced. To create new pentlandite surfaces, the slurry is reground, and a final flotation is performed to recover as much pentlandite as possible before the tails. The challenge is that pentlandite floats poorly in the fine particle size range so grinding creates additional fines and renders pentlandite less floatable. Additionally, pentlandite fines oxidize faster, resulting in a hydrophilic surface and poor dixanthogen formation. Finding a means of surface cleaning without the use of chemicals would be a helpful tool in improving nickel recovery in a sulfide processing mill.

  High intensity conditioning (HIC) is a technique that has been successfully used in removing slimes from minerals that would otherwise be difficult to separate. The shear force generated from HIC can overcome the force of adhesion from both slimes and oxides, cleaning the mineral surface. In addition, a mechanism known as shear flocculation can occur under certain conditions, that agglomerates fine hydrophobic particles into larger, more floatable particles. The simultaneous dixanthogen formation during surface cleaning and aggregation of fines is responsible for the increased recovery of the minerals tested in the few studies available. The main purpose of this paper is to illuminate the benefits of High Intensity Conditioning (HIC) on oxidized slurries and clarify the challenges that hinder the implementation of HIC into plants. With the use of a Rushton impeller, the high shear fields can clean the mineral surface of slimes and oxides while still allowing for xanthate adsorption on Cp and Pn. Due to the lack of studies combining HIC and sulfide minerals, fundamental tests were performed to determine each mineral’s response to HIC. Oxide layers formed on concentrates and tails were removed and analyzed to determine metal oxidation levels.

  The effect of high intensity conditioning on the oxidized sulfide ore is dramatic. When 10 or 20 g/ton of xanthate were used, chalcopyrite recovery with HIC was 4.5% higher than with no HIC while pentlandite recovery was 12% and 8.5% higher with HIC, respectively. However, pyrrhotite recovery with HIC was shown to increase by 22% and 14% for 10 and 20 g/ton of xanthate respectively. Solution analysis of the dissolved oxide layers from the concentrates showed that the immediately floatable minerals had high levels of oxidized copper and nickel. Ion activation is believed to be the cause. Based on the metal levels, with copper activation being more prevalent in the first few minutes of flotation and nickel activation playing a lesser role initially but becomes more rampant as time progresses. The HIC, while able to remove oxide surfaces, did nothing to hinder the oxidation of the sulfide surfaces. The combination of the oxidation and subsequent removal by HIC likely increases the copper and nickel ion concentration in the solution, allowing for pyrrhotite to activate and become floatable. If steps to reduce oxidation can be made, it is likely that pyrrhotite activation could be diminished but not entirely removed. Additionally, results may improve if chalcopyrite is not present in the slurry and therefore only nickel activation was the primary catalyst for activation.

  The parameters used for HIC reflected the state of the minerals when used. The initial flotation responses showed the mineral was much less floatable despite being a concentrate. Given this, it is quite likely that if the slurry was testing shortly after plant sampling, the parameters for HIC, including xanthate addition and duration of HIC, can be reduced. More minute changes would allow for greater control and analysis of which mechanisms complete faster.

  High intensity conditioning can reinvigorate pentlandite surfaces and flocculate fines. The sparse use of this technique means more work is needed before a complete process can be implemented. If more interest could be garnered and the experimental design improved, HIC could eventually be a means to slurry treatment to maximize recovery of valuable minerals, which will become scarcer over time.
  

• Subjects / Keywords

  • Pyrrhotite
  • Rushton
  • Pentlandite
  • Sulfide
  • Hydrofoil
  • Chalcopyrite
  • High Intensity Conditioning

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-06qs-w023

• License

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