Proceedings paper

Scand J Work Environ Health 1995;21 suppl 2:9-14    pdf

Physicochemical properties of crystalline silica dusts and their possible implication in various biological responses

by Fubini B, Bolis V, Cavenago A, Volante M

The effect of grinding, heating, and etching was investigated on polymorphs of silicon dioxide, and samples of diatomaceous earths were converted into cristobalite at 1000°C. Dusts obtained by grinding crystalline minerals exhibited different micromorphology and a propensity to originate surface radicals which decrease in the sequence cristobalite quartz coesite stishovite. The production of surface radicals was suppressed by grinding in the presence of water. Thermal treatments selectively quenched the radicals and decreased surface hydrophilicity. Quartz treated with aluminum lactate exhibited higher surface acidity when compared with pure quartz, with a reduction in fibrogenicity. Etching by hydrofluoric acid smoothed the particles with loss of specific surface. Adsorption of water on three cristobalite dusts produced a loss in hydrophilicity after heating above 1300°C and may have been related to a corresponding reduction in fibrogenicity.