Interference of Strontium and Yttrium Cations and Surfactants in Competitive Adsorption onto Activated Carbon: A Radioatracer Study

The interference of Sr(II) and Y(III) cations with cationic, anionic, and nonionic surfactants during competitive adsorption on lignin-produced activated carbon was studied. Dodecyltrimethylammonium bromide, sodium dodecylsulfate, and decaethylene glycol monododecyl ether (Brij-35) were used as surfactants. The radiotracers Sr/Y and tritium were used to trace the equilibrium concentration of metal cations and the surface concentrations of the surfactants, respectively. Tritium-labeled surfactants were obtained using the tritium thermal activation technique. Liquid scintillation spectrometry was used to determine the concentration of all substances. The SpectraDec software was used for joint measurement of Sr/Y and tritium radioactivity. It was shown that the presence of a surfactant affects the adsorption of strontium and yttrium onto activated carbon produced by thermochemical activation with orthophosphoric acid. The formation of a low-solubility precipitate with an anionic surfactant increased the adsorption of both cations, reduced their desorption, and promoted the sorption of the anionic surfactant itself. The nonionic surfactant (containing oxyethyl groups) did not affect the adsorption of strontium and yttrium cations but helped retain them on the carbon surface, preventing desorption. The cationic surfactant competed with strontium and yttrium cations for active sites on the activated carbon surface: adsorption of all components decreased, while desorption of cations increased.