In this study, the rheological characteristics of asphaltite−water slurries (AWSs) were investigated with
respect to some of the most important parameters in the preparation of slurries. The effects of pulp density,
chemical addition, pulp pH, and particle size on the rheological behavior and viscosity of AWSs were studied.
The role of demineralization of asphaltite was also investigated, and rheological properties of raw and relatively
demineralized asphaltites were compared. Results showed that viscosity of the AWSs was negatively influenced
by increases in the pulp density and as the mean particle size decreased from 104.81 to 15.39 μm. Increases
in pH provided reduced viscosity values. The effects of dispersing and stabilizing agents were studied with a
chemical mixture including 90% polystyrene sulfonate (PSS) as the dispersant and 10% Na-carboxylmethylcellulose (Na-CMC) as the stabilizer. The change in the viscosity was also investigated as a function of the
dosage of the chemical mixture used. Minimum viscosity was achieved with a 1.1% chemical mixture addition,
while excess dosages resulted in adverse effects and thickening of the slurry. Studies with raw and demineralized
samples showed that mineral matter and hydrophobic aggregation of particles are critical factors, significantly
affecting the rheological characteristics of AWSs.
The
structure of the xanthates’ hydrocarbon (C–H)
chain is one of the major factors which affect flotation recovery.
The effectiveness and the collecting power of xanthates increase with
increasing chain length and vary depending on the chain structure:
branched and straight chains. In this regard, the influences of length
(2–5 carbon) and structure (straight: normal and branched:
iso) of xanthate’s hydrocarbon chain on flotation recovery
of galena were investigated under different experimental conditions:
xanthate concentration, conditioning time, air flow rate (AFR), and
air bubble size. Because of the steric effects of the chain structure,
the branched chain xanthates gave lower flotation recoveries with
shorter conditioning times compared to those with straight chain xanthates.
Over-conditioning with straight chain xanthates resulted in hydrophobic
aggregation of galena particles which resulted in the detachment of
galena particles from air bubbles due to increasing weight, leading
to lower flotation recoveries. In the case of flotation with different
AFRs, the flotation recoveries increased with increasing AFR to 7
lph and further increase in AFR (10 lph) negatively affected the flotation
recoveries when particles had insufficient hydrophobic surfaces. The
maximum flotation recoveries were obtained with the addition of MIBC
(methyl isobutyl carbinol) as a frother; the size of the air bubbles
deceased with increasing MIBC concentration which increased higher
encounter/collision probability of air bubbles with galena particles,
resulting in higher flotation recoveries.
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