Sezyum, baryum ve fenolün yapısı değiştirilmiş hümik asit ve demir nanoparçacıkların üzerine tutunmasının incelenmesi

There is an increasing effort for removing highly solubleradiocontaminants from aqueous waste streams by fixing them onto solid wasteforms that can be disposed of in a repository. In this way, the high-volume aqueousstreams are transformed from a high-level radioactive waste into a low-levelradioactive waste that is much cheaper to treat. However, the removal of thisspecies may not only serve environmental initiatives, but it may also serve as ameans of producing useful materials for use in science and industry. It is known, for137example, that Cs is an excellent γ source for medical applications such as137instrument disinfection and radiotherapy. Similarly, Cs has also proven to be137useful as source for sterilization in the food industry. The radionuclide Cs isproduced in high yield during the fission process and due to its long half-life (T1/2 =30.17 y) and its high solubility in aqueous media, it is a principal radiocontaminantin radioactive wastes. Barium is an alkaline earth element (Z = 56), its radioactiveisotope 140Ba (T1/2 = 12.79 d) is a fission product with a high yield (6.21%).Wastewaters containing phenolic compounds present a seriousenvironmental problem. Phenolic compounds are present in the wastewatergenerated from paint, solvent, petroleum (petrochemical), coal conversion etc.industries. Phenolic substances are known carcinogenic substances, doses over 1 gcan be fatal for humans. Living organisms in aquatic environments are negativelyeffected by the uptake of phenolic subtances.Humic acid , which is the most important organic component of soil, is achemically and physically heterogeneous substance which is formed by chemicaland biological degradation of organic residues in natural environment. Humic acidhas many functions in soil chemistry such as adsorbing metal ions and organicsubstances, mineralization of plants and conversion of toxic substances biologically.Iron nanoparticle technology is increasingly being used in environmentalremediation and hazardous waste treatment. One important advantage of nano-sizedFe0 used in conventional permeable reactive barriers is that nanoparticles may bedelivered to deep contamination zones by injection.This study was conducted to find an alternative and efficient way forremoving radioactive and phenolic wastes from aquatic environments. Modifiedhumic acids (sodium form of insolubilized humic acid (INaA) and surfactantmodified insolubilized humic acid (SMIA) ) and iron nanoparticles were used assorbent materials.In this study, radioactive tracer method and UV-VIS spectroscopictechnique were used to examine the sorption behavior of Cs+, Ba2+ ions and phenolonto modified humic acids and iron nanoparticles. Characterization studies of13humic acid and its modified forms were carried out using FTIR, solid state CNMR spectroscopy techniques and adsorption sites (carboxylic and phenolicgroups) of humic acid were quantitatively determined by potantiometric titration.SEM and PXRD techniques were used to characterize iron nanoparticle samples.Sorption studies at different temperatures and kinetic studies were carriedout to examine the effects of time, concentration, and temperature on the sorption ofcations and phenol onto the various forms of humic acid and iron nanoparticles. Allcation sorption processes are well described by both Freundlich and Dubinin-Radushkevich type isotherms. Phenol sorption data was well fitted to Freundlichand Tempkin isotherms when surfactant modified humic acid was used as a sorbent.The sorption order with cation sorbent pair is barium-INaA > cesium-INaA >barium- iron nanoparticles. Kinetic studies indicated that adsorption behaviors ofboth cations and phenol obey pseudo second order rate law. The rate constantvalues of the three sorption cases studied have an inverse relationship with sorptionaffinity. The order for the rate of sorption with cation-sorbent pairs is as thefollowing; barium-iron nanoparticles > cesium-INaA > barium-INaA. Theequilibrium time for phenol sorption onto surfactant modified insolubilized humicacid was much longer than the equilibrium time for cations.Thermodynamic parameters such as enthalpy change, ΔHº , entropy change,ΔSº and free energy of adsorption, ΔGº, were calculated from the sorption data ofCs+ and Ba2+ ions at different temperatures. The values obtained for ΔHº and ΔSºwere -3.673 kJ/mol, 48.85 J/mol.K, 2.102 kJ/mol, 89.522 J/mol.K and -38.5 kJ/mol,-73.98 J/mol.K for cesium-INaA, barium-INaA and barium-iron nanoparticles ion-sorbent pairs, respectively. Temperature changes did not siginificanly affect thesorption affinity of Cs+ and Ba2+ ions onto INaA. Ba2+ ion sorption onto ironnanoparticles is an exothermic process which means that low temperatures arefavored.The calculated negative values of ΔGº obtained at different temperaturesindicate the spontaneity of all adsorption processes studied. All adsorption meanfree energy values are found to be within 8-16 kj/mol range which is the energyrange of ion-exchange type processes.Keywords: Adsorption, Isotherms, Modified Humic Acid, ThermodynamicConstants, Phenol, Kinetic Studies, Distribution Ratio, Radioactive Tracer Method,Cesium, Barium, Batch Method, Characterization, Iron Nanoparticles, UV-VISspectroscopy.