Mihailova I.Vassileva P.Mehandjiev D.2024-07-162024-07-162024-07-162024-07-162019-01-011314-79781314-7471SCOPUS_ID:85069781691https://rlib.uctm.edu/handle/123456789/1248The purpose of this study was to investigate the prospective use of calcareous clay in its natural state and after thermal treatment for removal of heavy metals from aquatic environment. The study included 6 natural products from clay deposits in Bulgaria, five of which were calcareous clays and the sixth one was an iron-rich clay. The structural characterization of the samples was carried out using inductively coupled plasma optic emission spectrometry, X-ray powder diffraction analysis, Fourier-transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The clay minerals contained in the samples were identified as illite, chlorite, kaolinite and smectite. Quartz, calcite and feldspar were identified in the samples too. The thermal treatment has led to changes in the phase composition of clays as a result of partial dehydration and decomposition of minerals. There was an increase in the adsorption capacity of the calcareous clays relative to the metal ions of Cu(II) and Zn(II) after thermal treatment, regardless of the reduction of their specific surface area, which is determined by the increase of the adsorption centers upon thermal treatment.enArticle