Diatomite samples were obtained from the Caldiran region of Van/Turkey. The chem-ical analysis of the diatomite obtained by a XRF technique revealed a chemical com-position. The physical properties of the diatomite are given in Table 1. The natural diatomite sample, which was powdered by pounding in a porcelain mortar, was washed with distilled water and dried in an oven at 105 ºC. Rhodamine-B (Rh-B) as a dye was obtained from textile corporation (İstanbul/Turkey). The structural form of rhodamine-B is given in Fig. 1. A Rh-B has the maximum absorption wavelength at 553.7 nm. The maximum absorption wavelength of Rh-B was determined by finding out absorbance at the characteristic wavelength using a double beam UV-visible spec-trophotometer.