Marek Pawlik

To support the transformation to clean low carbon technologies, there is a demand for critical metals such as nickel. Awaruite is a less common nickel-bearing mineral with unique properties and responses to mineral separation. This paper presents the findings of a flotation study to recover awaruite from the Baptiste ultramafic deposit, located in central British Columbia, Canada. Nickel recoveries of up to 65% at the rougher stage were obtained with xanthate as a collector at a pH level of 4.5. Awaruite flotation was shown to be highly dependent on the slurry pH. At weakly acidic conditions, the awaruite surface is activated through the dissolution of the passivation layer formed during grinding in alkaline conditions. Desliming was shown to reduce the acid consumption required to maintain the pH, probably by removing the highly reactive serpentine slimes generated during grinding. Rougher, followed by cleaner stages of flotation, showed that a high-grade concentrate can be produced with up to 45% nickel, 1.3% cobalt, 0.7% copper and negligible concentrations of penalty elements, such as arsenic, lead, and selenium, among others. A nickel flotation concentrate from an awaruite deposit is a promising feedstock for not only stainless-steel production but also for clean energy technologies.

The widely used technology for the selective flotation of copper and molybdenite using sodium hydrosulfide (NaSH) to depress copper sulfides creates environmental issues related to the potential emissions of toxic hydrosulfide gas (H₂S) and bad odors. Previous studies showed that molybdenite flotation can be depressed by the action of lignosulfonates, but no significant progress has been made in studying the effect that these reagents have on the foaming/frothing phenomena in flotation. The objective of this work was to investigate the foaming properties of three samples of lignosulfonates through measurements of surface tension, foamability, bubble size distributions, and water recovery. A sugared sodium lignosulfonate (NaLS), a calcium lignosulfonate (CaLS), and a sample prepared by sulphomethylation of kraft lignin (KLS) were tested. It was found that all lignosulfonates displayed surface activity that decreased with pH and was related to the degree of anionicity and molecular weight. The NaLS lignosulfonate showed the highest dynamic foamability index (DFI) value, compared to that of the CaLS and KLS samples. The lignosulfonates tested in this study strongly affected bubble size. Water recovery tests performed using flotation experiments in a two-phase system showed that the KLS and NaLS samples had the strongest effect, which correlated with the surface tension, foamability, and bubble size results.

Optical backscattering (OBS) signal values were used to evaluate the flocculation of kaolin slurries and seek the implications of using seawater. Two anionic flocculants were applied to kaolin suspensions at several dosages and in water of varying pH and electrolyte concentration. An OBS height scan method was used to estimate the degree of aggregation, supernatant quality, and solids concentration of the sediments. The residual solids of the supernatant depended of the extent of particle coagulation before flocculant was added, where the pH and salinity displayed a significant impact on flocculation. The OBS results were highly sensitive to the presence of fine particles, which was estimated in parallel from the focused beam reflectance measurements (FBRM.) In seawater, without flocculant added, the samples had increased root-mean-square scattering (F_rms) values and larger final sediment volume than samples prepared in water with lower electrolyte concentration. This indicates a higher initial state of aggregation of the particles in seawater. Then, the aggregation degree was best linked to the square-weighted chord length distribution of the FBRM data, which intensifies the sensitivity to coarse aggregates.

An in situ microscopy method was employed to study the sediment volumes that result from batch settling of polymer‐flocculated kaolin suspensions. Statistical methods were applied including chord length distributions, perimeter‐based fractal dimension of the void areas, white area image ratio, and gray level co‐occurrence (GLCM) features. Several GLCM features have a good linear relationship with aggregation state, and the parameters of aggregate and void chord distributions can be interpreted to help explain the flocculation results. The methods applied here are suggested for the measurement of the aggregation state or relative aggregate volume on bench or industrial scale when the settled suspension interface is not available, such as in a continuous process or reaction.

Yield stress measurements were carried out on slurries prepared from five different ore samples of varying contents of bitumen and fines in the sand fraction. The rheological measurements were performed using the vane, slump, and relaxation methods, as well as by extrapolation of equilibrium flow curves to zero shear rate. In the case of the vane tests, it was found that the yield stress values agreed better with the results obtained from the other techniques when the yield stresses were calculated using a torque value at the point of departure from linearity on the initial section of experimental torque‐time curves. It was found that the yield stress values of oil sand slurries increased with an increase in bitumen content in the ores. High‐bitumen ores tended to yield within a volume of the slurry extending well beyond the geometry of the vane. In contrast, low‐bitumen ores yielded much closer to the vane edges. As a result, the torque value at the point of departure from linearity on the torque‐time curve was recommended for calculating the yield stress of high‐bitumen ore slurries with the use of the vane technique. On the other hand, the maximum torque value on the torque‐time curve can be used for determining the yield stress of low bitumen ores.