Rezumat
A selective sorbent based on local diatomite modified with aluminum compounds is investigated by means of X-ray, differential thermal, adsorption-structural (BET) FTIR and chemical analysis. Surface modification of diatomite was carried out by heating it in NaOH solution, followed by treatment with a solution of aluminum salt and ammonia. When processing NaOH partially dissolves the surface amorphous silica, which at the stage of making aluminum salt forms an aluminosilicate compound. The resulting material is deposited on the surface of diatomite, and the inner surface of the macro-and large mesopores, which leads to the development of specific surface area of 81.8 m2/g, which is 2 and a half times more than the initial diatomite (37.5 m2/g). Precipitated aluminosilicate compound containing 0.34 gAl/g aluminosilicate contributes to the development of porous structure of the processed diatomite – mesopore volume increased from 0.029 to 0.079 cm3/g, while the micropores from 0.012 to 0.027 cm3/g. Qualitative changes in the composition of the sorbent obtained confirmed the emergence of new lines in the diffraction patterns characteristic of aluminosilicate and peaks in the infrared spectra responsible for the stretching vibration of Si-O-Al. The selectivity of the adsorbent obtained in relation to the fluoride ions increased significantly: at the initial fluorine concentration 0.15 mol/L its adsorption capacity increased from 8.9 to 57.6 mg F/g.