This paper describes the purification of diatomaceous earth mined in the Ankara region of Turkey. The diatomaceous earth was found to be essentially amorphous, but a small amount of crystalline illite, K_(0.7)Al_2(Si,Al)_4O_(10)(OH)_2, was present in it. The complete chemical composition of the material was 74.4 percent SiO_2, 14.55 percent Al_2O_3, 3.62 percent Fe_2O_3, 1.55 percent CaO, 1.37 percent MgO, 2.44 percent K_2O and 0.72 percent Na_2O. In connection with the purification of the diatomite, two different processing routes were planned: (i) leaching of the diatomaceous earth directly in cold acidic solutions of HCl; (ii) leaching of the diatomaceous earth directly by using hot 1 and 2N HCl. It was found that all of the undesirable elements in the composition of the diatomaceous earth were dissolved when treated at about 100 deg C with acidic solutions prepared using 1 and 2 N HCl for various leaching times. Under several cold acid concentrations, varying from 1 N to 5N HCl, however, only a small amount of silica is dissolved, while significantly reducing the contribution of undesirable aluminium, calcium, magnesium, iron and alkaline elements.
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