Využití bentonitů a jejich modifikací pro adsorpci a desorpci vybraných těžkých kovů z modelových roztoků.

Abstract

Sorption properties change after modification of the structure of phylosilicates, which in practice increases their utilization. The subject of this thesis is a study of the adsorption of Pb2+ and Cu2+ from model solutions and desorption of Pb2+. Bentonites from the Braňany – Černý vrch locality, in natrified and intercalated forms were used as adsorbents. The advantage of this material is its natural origin and easy availability. Firstly, bentonites from three different locations (the Braňany – Černý vrch deposit, the Rokle deposit near Kadaň and the southern slopes of the Bílina mine area) were evaluated by X-ray diffraction, X-ray fluorescence and by the determination of their sorption properties. The most suitable sample was chosen. This bentonite was divided into two grain fractions (<0.1 mm and 0.1–0.5 mm). The material was subsequently chemically modified to improve its sorption properties. The fine-grained fraction was natrified by a NaCl solution and both fractions were intercalated by octadecylamine (ODA) in different weight ratios. All the materials were tested on the model solutions prepared from the salts of the chosen metals (Pb2+ and Cu2+). During adsorption of lead and cupric cations, the adsorption equilibrium was established faster for modified samples than for unmodified samples. Langmuir and Freundlich adsorption isotherms were applied for the formulation of maximal adsorption capacity related to equilibrium concentration. Diluted acetic acid was used for the desorption process of Pb2+ with a pH value of 3.53. For this purpose three samples of bentonites from the Braňany – Černý vrch locality and three modified samples (natrified and intercalated by ODA in two different weight ratios) with a graininess of <0.1 mm were used. The sample modified by ODA in the same weight ratio as the bentonite was shown as a very suitable adsorbent of lead cations because after desorption the value of retained cations was relatively high. A coarse-grained sample modified by ODA in a higher weight ratio was more effective for adsorption of Cu2+.