Modification of Algerian Bentonite and Using It as Support in Gas Chromatography

Abstract

Two chromatographic supports were prepared from Algerian bentonite by thermal and chemical treatments. The first support was prepared by thermal treatment of bentonite at 650ºC to obtain firm granules, then washed with 6 N HCl to remove the soluble metallic oxides, especially iron oxide, till obtained white granules, with diameter range 125–150 μm. The second one was prepared by thermal treatment of the granules of the first support at 1100ºC, and chemically by 6 N HCl. The specific surface areas of support were measured and found 112 and 12 m²/g respectively. The two yield support granules were silanized with dimethylchlorosilan at 120ºC in the vapour phase, under slow flow of dry pure nitrogen, to obtain a new surface structure that possesses chromatographic properties. A suitable amount of bentonite granules (S = 12 m²/g) were coated with 3% of silicone SE-52 and heated under slow flow of dry pure nitrogen at 280ºC for 24 h, and then extracted with chloroform in soxhlet apparatus for 48 h. The grafting process changed the surface structure of bare treated bentonite. The packing obtained participated effectively in separating different mixtures of aromatic compounds and mixtures of normal hydrocarbon compounds with a good sharp chromatographic peak on columns (50 cm x 4 mm), packed with modified bentonite, with good precision and reproducibility.