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Pseudoboehmite was impregnated with cobalt using a incipient wetness impregnation method. Two different concentrations of cobalt were used for impregnation: 3 mas% and 6 mas% of Co2+ relative to the mass of pseudoboehmite. The obtained materials were calcined at 500 ºC. The synthesized catalysts were tested in the process of oxidative degradation of tartrazine dye in the presence of Oxon as a source of sulfate anion radicals. The influence of temperature on the dye degradation efficiency was investigated. It was observed that the degradation rate increases with the increasing of temperature. The experimentally obtained results were tested using the most common kinetic models and it was found that the reaction follows a pseudo-first order rate in all cases. It was also observed that with an increase in the cobalt content, the efficiency of the catalyst increases. In order to determine which reactive oxidative species is dominant in the investigated process, tertiary buthalnol and ethanol was added to the reaction system. According to the experimental results sulfate anion radicals were found to be the dominant reactive species.

Montmorillonite originated from Wyoming was modified by acid activation and aluminum pillaring process. The samples of clay obtained in this manner, as well as starting clay, were applied at the surface of a glassy carbon electrode by the means of Nafion. The activity of these electrodes was investigated on the redox couple quinone/hydroquinone (Q/QH2) in buffered and unbuffered solutions. The type of clay modification influenced the activity of the electrodes and the mechanism of the redox reaction.

A thorough discussion on the Comments on the article “Adsorption of strontium on different sodium-enriched bentonites”, by Sanja R. Marinović, Marija J. Ajduković, Nataša P. Jović-Jovičić, Tihana M. Mudrinić, Bojana N. Nedić-Vasiljević, Predrag T. Banković and Aleksandra D. Milutinović-Nikolić published in the Journal of the Serbian Chemical Society, Volume 82, Issue 4, Pages: 449-463 (2017), given as Letter to the Editor by S. K. Milonjić, is provided in this letter. The authors of the commented paper have considered all the comments, and responded to each of them, point by point.

Bentonites from three different deposits (Wyoming, TX, USA and Bogovina, Serbia) with similar cation exchange capacities were sodium enriched and tested as adsorbents for Sr2+ in aqueous solutions. X-Ray diffraction analysis confirmed successful Na-exchange. The textural properties of the bentonite samples were determined using low-temperature the nitrogen physisorption method. Significant differences in the textural properties between the different sodium enriched bentonites were found. Adsorption was investigated with respect to adsorbent dosage, pH, contact time and the initial concentration of Sr2+. The adsorption capacity increased with pH. In the pH range from 4.0–8.5, the amount of adsorbed Sr2+ was almost constant but 2–3 times smaller than at pH ≈11. Further experiments were performed at the unadjusted pH since extreme alkaline conditions are environmentally hostile and inapplicable in real systems. The adsorption capacity of all the investigated adsorbents toward Sr2+ was similar under the investigated conditions, regardless of significant differences in the specific surface areas. It was shown and confirmed by the Dubinin–Radushkevich model that the cation exchange mechanism was the dominant mechanism of Sr2+ adsorption. Their developed microporous structures contributed to the Sr2+ adsorption process. The adsorption kinetics obeyed the pseudo-second-order model. The isotherm data were best fitted with the Langmuir isotherm model. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001]

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