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2 Physicochemical Problems of Mineral Processing

2 2018

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Quantifying the spreading factor to compare the wetting properties of minerals at molecular level – case study: sphalerite surface

Mohseni M., Abdollahy M., Poursalehi R., Khalesi M. R.

Physicochemical Problems of Mineral Processing

2018

Vol. 54, iss. 3

646--656

Spreading of water droplet on sphalerite surface was quantified at molecular level and was utilized for comparison of the wetting properties of sphalerite protonated and hydroxylated surfaces. Molecular dynamic simulations were used to characterize the wetting of sphalerite (110) plane. Experimental contact angles of water droplet on sphalerite surfaces were measured and the results were compared with simulated contact angles to ensure that the simulations are accurate enough for calculation of spreading factors. Shape descriptors such as perimeter, area, Feret’s diameters and circularity were used to characterize the shape of droplet-sphalerite interface at molecular level. Using the shape descriptors, different spreading factors were defined and calculated spreading factors were correlated with simulated contact angle. It was shown that spreading factors which were defined as the volume of water droplet divided by the area and Feret’s diameters, with correlation coefficient of 0.98 and 0.97, can be used as accurate tools for wetting comparison of functionalized sphalerite surface at molecular scale. Proposed approach also can be used for investigations on the effect of surface chemical and physical anisotropies on preferred wetting in specific direction at molecular scales.

Bubble loading profiles in a flotation column

Eskanlou A., Khalesi M. R., Abdollahy M.

Physicochemical Problems of Mineral Processing

2018

Vol. 54, iss. 2

355--362

Bubble loading is the mass of hydrophobic particles attached per unit surface area of air. This measure can be used in the design and analysis of flotation columns as a sign of true flotation. To date, however, this measurement has been limited to the pulp-froth interface, which only indicates the maximum bubble loading and does not reflect the progress of the loading process. This paper introduces the concept of bubble loading profile that summarizes measures of bubble loading at different heights of the collection zone in a flotation column. The effects of bubble size, particle size and collector dosage on the introduced profiles are also investigated. These operational variables changed the bubble loading profile from a linear to a curved trend. The curvatures in the profiles were near the place of the feeding port and therefore the collection zone was divided into two separate zones in terms of bubble loading characteristics. The zone below the feeding port often did not contribute much to the loading of particles on the bubbles and the loading phenomenon mostly took place above the feeding port. Behaviors of the profiles in these two zones were analyzed to reveal that a change in the feeding port placement or column height can, under some conditions, increase the overall bubble loading and thus, ultimately, the true flotation.