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In the present study, new adsorbent beads of alginate (A)/maghemite nanoparticles (γ-Fe2O3)/functionalized multiwalled carbon nanotubes (f-CNT) were prepared and characterized by several techniques, e.g., N2 adsorption-desorption isotherms, Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM) and further tested for the adsorption of the dye methylene blue (MB) from water. The beads (A/γ-Fe2O3/f-CNT) presented a relatively low BET specific surface area value of 59 m2g−1. The magnetization saturation values of A/γ-Fe2O3/f-CNT beads determined at 295 K was equal to 27.16 emu g−1, indicating a magnetic character. The time needed to attain the equilibrium of MB adsorption onto the beads was estimated within 48 h. Thus, several kinetic and isotherm equation models were used to fit the kinetic and equilibrium experimental results. The number of adsorbed MB molecules per active site, the anchorage number, the receptor sites density, the adsorbed quantity at saturation, the concentration at half saturation and the molar adsorption energy were quantified using the monolayer model. The calculated negative ΔG0 and positive ΔH0 values suggested the spontaneous and endothermic nature of the adsorption process. In addition, A/γ-Fe2O3/f-CNT composites can be used at least for six times maintaining their significant adsorptive performance and could be easily separated by using a magnet from water after treatment.

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Multicomponent sepiolite/magnetite/Prussian blue (PB) were prepared following the nanoarchitectonics approach by incorporating PB pigment to sepiolite fibers previously assembled with magnetite, being later encapsulated within in situ formed calcium alginate beads. These composites were characterized by diverse physicochemical techniques, showing homogeneous dispersion of the assembled nanoparticles (NP) on the surface of sepiolite fibers, the formed Ca-alginate beads exhibiting stability and superparamagnetic response. Based on the affinity of PB toward cesium ions, these beads were tested as selective adsorbent to remove Cs+ from water under different experimental conditions. The maximum adsorption capacity of the beads for Cs+ ions determined by Langmuir equation was around 130 mg/g. The resulting beads maintain a constant adsorption capacity over a large domain of pH, i.e. from 4 to 11. The mechanism of Cs+ removal could be mainly ascribed to the complexing ability of PB, although in minor extent also to cation-exchange properties of sepiolite as well as to interactions with residual carboxylic groups from the alginate biopolymer matrix. The resulting multicomponent composite can be considered as an efficient, economic, ecologic and easily recoverable adsorbent for the removal of Cs+ ions from solution, including radioactive 137Cs, and therefore contributing to environmental remediation of pollution caused in nuclear plants.