Terbium is a rare-earth element with critical importance for industry. Two adsorbents of different origin, In₂O₃ nanoparticles and the biological sorbent Arthrospira platensis, were applied for terbium removal from aqueous solutions. Several analytical techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy, were employed to characterize the adsorbents. The effect of time, pH, and terbium concentration on the adsorption efficiency was evaluated. For both adsorbents, adsorption efficiency was shown to be dependent on the time of interaction and the pH of the solution. Maximum removal of terbium by Arthrospira platensis was attained at pH 3.0 and by In₂O₃ at pH 4.0–7.0, both after 3 min of interaction. Several equilibrium (Langmuir, Freundlich, and Temkin) and kinetics (pseudo-first order, pseudo-second order, and Elovich) models were applied to describe the adsorption. The maximum adsorption capacity was calculated from the Langmuir model as 212 mg/g for Arthrospira platensis and 94.7 mg/g for the In₂O₃ nanoadsorbent. The studied adsorbents can be regarded as potential candidates for terbium recovery from wastewater.

Semiempirical PM6 quantum mechanical method was used to investigate the changes in the electronic and physical parameters of graphene before and after interaction with calcium oxide (CaO). Calculations were conducted the optimized structures with graphene interacting with two CaO molecules forming G/CaO nanocomposite once through the O atom then through the Ca atom, in the form of adsorb and complex states. Results indicated the deformation of graphene structure upon interaction with CaO but the resulting G/CaO is more thermally stable than graphene itself. The studied G/CaO composites were also found to be more reactive than graphene in regard to their higher calculated total dipole moments. The calculated thermal parameters further confirmed the thermal stability of G/CaO composites.