M. Galamboš

Sorption of anthropogenic radionuclides on natural and synthetic inorganic sorbents

The history of sorption and ion-exchange processes starts with the use of natural materials which properties were discovered coincidentally and ends with the age of polymer and anorganic—or synthetic sorbents specifically made for a particular project. Its objectives are focused on sorption of anthropogenic radionuclides originating from nuclear power plant operations (fission, activation, corrosion products and transuranium elements) on bentonites, zeolites, hydroxyapatites, magnetic sorbent, ferrocyanides, and silica sorbent. Bentonites from Slovak deposits should be used as part of multi-barrier system in deep geological repository for spent nuclear fuel and high level radioactive waste. Zeolites are used as molecular sieves, catalysts, ion-exchangers, sorbents, water softeners, in wastewater treatment, in chemistry industry, buildings. Hydroxyapatite is a suitable sorbent for heavy metals and radionuclides due to its low water solubility, high stability under reducing and oxidizing conditions, high specific surface area and good buffering properties. The leaching wastes from the Sereď hydrometallurgical plant represent a large stock of inexpensive, ready-to-use magnetic sorbent for the decontamination of soil or sediments in their common suspensions, followed by the magnetic separation and sorbent recycling. Insoluble ferrocyanides of nickel are highly selective sorbents for heavy alkali metals ions, and therefore can be used to separate cesium from liquid radioactve waste. Silica sorbents modified with imidazole can be used for the separation of cobalt ions from aqueous solution.

Comparative study of strontium adsorption on dioctahedral and trioctahedral smectites

Slovak bentonites characterized by good rheological, mineralogical and chemical stability are considered as suitable sealing barriers for construction of Slovak deep geological repository for high-level radioactive waste and spent nuclear fuel. There is several Slovak bentonite deposits, bentonites of which have appropriate adsorption properties meeting the geotechnical requirements for this type of barriers. Study of adsorption properties of bentonites (mainly smectites) is an essential step for developing the migration model long-lived corrosion and activation products, and fission products of uranium. Nuclear wastes contain the most important nuclear fission products, β-emitter 90Sr with long half-life, biological half-life and high mobility. The present paper investigates and compares the strontium adsorption properties of bentonites of different mineral composition consisted mainly of dioctahedral and trioctahedral smectites.

Effect of competing anions on pertechnetate adsorption by activated carbon

Activated carbon (AC) has a relatively high efficiency for retaining TcO4− compared to other materials. AC is used on a vast scale in gas and water purification, metal extraction, medicine and many other applications. The TcO4− adsorption mechanism on AC is not fully known, however there are assumptions of ion-exchange reaction between AC surface and TcO4− anions. Adsorption and anion competitive investigation have shown that perchlorate anions have most influence on TcO4− adsorption. Adsorption properties depend on standard absolute molar enthalpies of hydration. Anion competitiveness was investigated with five samples that were prepared in different ways (this was already published in previous article), we used several anions Cl−, Br−, ClO4−, CH3COO−, NO3−, HCOO− and SO42− at different concentrations. In general, the adsorption of TcO4− is influenced mostly by ClO4−, what is explained by its similar structure with TcO4−; however the co-existence of Fe3+ cations in the AC structure decreases TcO4− adsorption.

Sorption and desorption of pertechnetate on biochar under static batch and dynamic conditions

The objective of this study was the utilization of three different biochars for pertechnetate removal from aqueous solutions. Biochars were prepared by slow pyrolysis from different feedstocks, characterized by BET, acid–base titration, SEM, XRD and FTIR and tested for their pertechnetate sorption using batch and dynamic techniques. Effect of various physico-chemical parameters such as contact time, pH and the presence of different ions in the solution on the sorption of pertechnetate onto biochars was investigated. Perrhenate as an analogue of pertechnetate was used for modeling of adsorption isotherms.

Column studies for the separation of 99m Tc using activated carbon

Activated carbon (AC) is an organic material with a high carbon content and is made from carbon-based material by its thermal decomposition in a furnace using a controlled atmosphere and heat. In this study, AC has been used for investigation, as a potential candidate, for laboratory separation process of technetium. The TcO4− has high mobility in environment, but mechanism for the TcO4− adsorption/desorption on AC is not exactly known. The main aim of this research was to investigate the separation of the 99Tc using five different samples of AC.

First shrinkage parameters of Slovak bentonites considered for engineered barriers in the deep geological repository of high-level radioactive waste and spent nuclear fuel

The high potential of bentonites to volume changes depending on the water content is considered as their advantage for the engineered barriers in the deep geological repository of high-level radioactive waste and spent nuclear fuel because of swelling and self-healing of cracks in contact with water. On the other hand, drying may lead to opening of cracks and spaces between the bentonite blocks. This would increase the permeability and contamination risk around the hot container with high-level radioactive waste and spent nuclear fuel, especially if the host rock mass is dry. First shrinkage tests on four Slovak bentonites studied for engineered barriers were carried out. The water content at the shrinkage limit and the relative linear shrinkage are the first available shrinkage parameters received for the bentonite paste. The shrinkage hazard is higher in the best bentonites with high swelling potential—from Kopernica and Jelšový potok. The results indicated the necessity of further shrinkage tests to determine the relative linear and volume shrinkage of bentonite elements pressed of the loose bentonite powder of low water content.

Sorption behaviour of pertechnetate on oxidized and reduced surface of activated carbon

Objectives of this research are preparation and characterization of oxidised and reduced activated carbon, and investigation of pertechnetate sorption on these activated carbons. Activated carbon could be an alternative interface in production of radionuclide generator with high Mo concentration, such as it is case for cyclotron or photoreaction producing 99mTc from 100Mo target. Sorption processes are investigated through radioisotope indication and strongly depend on pH and presence of competitive anions of the environment. Oxidative treatment leads to an increase in pertechnetate adsorption. Desorption of pertechnetate from the activated carbon surface is almost quantitative.

Adsorption of nickel on rhyolitic Slovak bentonites

Radioisotope of nickel 63Ni is an important product of the neutron activation in engineering materials of nuclear power plants. Adsorption of nickel on Slovak rhyolitic bentonites Jelšový potok, Kopernica and Lastove was studied using batch method. Radionuclide 63Ni was used as a tracer. In this paper, we focused on effects of contact time, pH, competitive cations and equilibrium study. This study showed that Slovak rhyolitic bentonites are a promising candidate for removal of radionickel from aqueous solutions.

Sorption of pertechnetate anions on chitosan

Chitosan is one of the natural materials of biological origin. It is able to adsorb of metal ions through its amino- and hydroxyl groups. This work was aimed to study influence of the contact time, effect of pH and effect of different ions on sorption of pertechnetate anions on chitosan. The sorption of pertechnetate anions from aqueous solutions on chitosan was studied in a batch system. The sorbent was characterized by BET-surface area and potentiometric titration.

Adsorption behavior of Zn(II) ions on synthetic hydroxyapatite

AbstractThe adsorption of Zn2+ on synthetic hydroxyapatite was investigated using a batch method and a radiotracer technique. The commercial hydroxyapatite and hydroxyapatite of high crystallinity with Ca/P ratio of 1.563:1.688 prepared by a wet precipitation process were used in this study. The adsorption of zinc on hydroxyapatite was pH independent ranging from 4.5 to 6.5 as a result of buffering properties of hydroxyapatite. The adsorption of zinc was rapid and the percentage of Zn adsorption on both samples of hydroxyapatite was >96% during the first 30 min of the contact time. The experimental data for adsorption of zinc have been interpreted in terms of Langmuir isotherm and the values of maximum adsorption capacity of zinc on a commercial hydroxyapatite and hydroxyapatite prepared by wet precipitation process were calculated to be 0.437 and 0.605 mmol g−1, respectively. The competition effect of Fe2+ towards Zn2+ adsorption was stronger than that of Ca2+, Mg2+, and Sr2+ ions. The ability of the biv...