Presence of negative charge on the basal planes of New York talc.

Potentiometric titration measurements as well as rheological measurements of talc aqueous suspensions indicate that the behavior of the New York talc particles is consistent with the presence of a negative charge on their basal planes. The possibility of the presence of a negative electrical charge on the basal planes of talc particles is analyzed in this paper. Samples of New York talc were studied using electron microprobe analysis and dehydration techniques and the exact chemical formula of New York talc was determined. It was found that there exists a deficiency of protons in the tetrahedral layers of talc, resulting from substitution of Si(4+) ions with Al(3+) and Ti(3+) ions. The comparison of the level of substitution of Si(4+) ions with ions of a lower valency was found to be of a similar order of magnitude as that found in other talc deposits. This strongly points to the presence of a negative charge on the talc basal planes.

Effect of carboxymethyl cellulose and ionic strength on stability of mineral suspensions in potash ore flotation systems.

The adsorption of sodium carboxymethyl cellulose from aqueous solutions varying in ionic strength from that of distilled water to 50% NaCl/KCl brine (about 3.5 mol/dm(3)) onto illite and dolomite has been studied. The purpose of this work was to investigate the solvency effects in the phenomena underlying the potash flotation process that is carried out in saturated brine. Based on viscosity measurements, the adsorption results were analyzed in terms of a simple model of polymer macromolecules in solution. Suspension stability measurements carried out concomitantly with adsorption tests showed the ranges of carboxymethyl cellulose concentration over which the tested suspensions either were aggregated or were restabilized.

Mineral matter distribution on coal surface and its effect on coal wettability.

Coal is an organic sedimentary rock composed of organic macerals and mineral matter. As it is demonstrated in this paper the discrete mineralogical nature of coal largely influences the wetting of the coal surface by water. Both advancing and receding contact angles were measured using the captive-bubble technique with an automatic bubble shape analysis software. The distribution and amount of mineral inclusions on the coal surface were determined by scanning electron microscopy and examined using the image analysis system. To determine the amount and size distribution of mineral grains, the coal surface layer, on which the contact angles were measured, was separated from the larger piece used in the measurements by microslicing. The separated surface layer was subjected to a low-temperature ashing followed by particle size analysis. As expected, a significant scatter of contact angle values was obtained for the same coal samples. Increasing the amount of mineral matter on the coal surface reduced the value of both advancing and receding contact angles. Also, the scatter of contact angle values increased with the increasing mineral matter content from about 1 to 50 wt%. The results reveal that an important factor in analysis of contact angle variation on coal surfaces is the size of the hydrophilic mineral inclusions. Both the advancing and the receding contact angles decrease with increasing size of the mineral grains. Additionally, the scatter of contact angle values increase with increasing size of the mineral matter grains. Finally, the results of fractal dimension analysis of mineral matter grains distributed over the coal surface indicate that there is no significant effect from the shape of hydrophilic mineral inclusions on both advancing and receding contact angles.