Interface Behavior Of The Mechanical Milling Of Pyrite In The Non-aqueous Environment

The dispersity of pyrite catalyst in coal impacts the efficiency of coal direct liquefaction. At present, the improvement for the effect of catalyst which is fully dispersed in liquefacient coal, such as adding nano-particles into coal slurry, is too far from the practical process. The preparation of pyrite catalyst by mechanochemistry is of the characterics of low cost, high output and simple technique. The change of structure and properties of pyrite catalyst with the addition of dispersants in the preparation process can achieve better dispersity in coal direct liquefaction and enhancement of catalystic effect.In this paper, the surface properties and particle size of pyrite, the slurry viscosity, the dispersity and electric potential of pyrite in two organic liquid medium (alcohol and heptane) were studied. The results show that small grains and low crystal lattice distortion for milled pyrite are obtained. The oxidation of pyrite decreases with the addition of dispersants. The median size of pyrite decreases with the increase of grinding time and solid content. Stearic acid is prior to get pyrite catalyst of minimum particle size and well dispersity for coal direct liquefaction. The regulation of slurry viscosity and the ability of hardness decrease of pyrite by absorption play a dominant role in particle size distribution of pyrite. The ability of hardness decrease of pyrite by absorption is greater than the regulation of slurry viscosity at small slurry viscosity. And the ability of hardness decrease of pyrite drops in the sequence of carboxyl, hydroxyl and alkane. The viscosity of slurry increases with grinding time and the decrease of pyrite particle. The slurry of pyrite belongs to typical Bingham fluid at low solid content. At high solid content, the slurry displays pseudoplastic behavior with yield stress. And the slurry takes on shear thinning at low shear rate.The dispersity of pyrite in two organic liquids was investigated using spectral photometer. It was found that the disperse behavior of pyrite particles in alcohol remains almost the same with different dispersants. The dispersity of pyrite in heptane decreases in the sequence of Span80, Octadecanol, Stearic acid and blank solution without dispersants. The larger theζpotential is, the better the dispersity of pyrite particle is.The dispersion mechanism of pyrite particles in liquids was analyzed using Extend DLVO theory. It was indicated that there exists an energy barrier, which will prevent the particles from agglomeration. There is no steric interaction in the whole range. On the contrary, the potential energy of pyrite particle in heptane is negative. The interface interaction presents an attraction characteristic. The pyrite particles in heptane tend to agglomeration. The steric interaction is large enough and energy barrier exists when Span80 is absorbed on the surface of pyrite. However, the pyrite particles still show agglomeration behavior with the addition of stearic acid and octadecanol.