Abstract
Two kinds of typical “acid clay”, treated with 3 parts of boiling 5-45% sulfuric acid for 4 hours, were examined by X-ray powder analysis, chemical analysis, cation exchange capacity, exchangeable hydrogen ion by treatment of 1 N NaCl solution, specific surface area and solid acidity.
One of the samples is of montmorillonite and another is of halloysite. By the acid treatment octahedral layer of the “acid clay” is attacked and cation is leached. Specific surface area of the acid-treated clay increases with increasing concentration of sulfuric acid. It is concluded that the collapse of octahedral layer of the clay enhances the amount of free amorphous silica. The acid-treated clay of montmorillonite is characterized by the solid acidity which is stronger and higher than that of the acid-treated clay of halloysite. This solid acidity varies with the concentration of sulfuric acid and shows maximum value at 15-25% sulfuric acid. The montmorillonite structure left in the residue after acid treatment is assumed to be responsible for this result. It is concluded that the character of the solid acid of acid-treated clay plays an important role in the refinment of aromatic hydrocarbons and the color formation of pressure-sensitive recording paper.
