Biochars from wood chips (WC) and corn cobs (CC) were prepared by slow pyrolysis and used for sorption separation of erythrosine B (EB) and thioflavin T (TT) in batch experiments. Biochar-based adsorbents were extensively characterized using FTIR, XRD, SEM-EDX, and XPS techniques. The kinetics studies revealed that adsorption on external surfaces was the rate-limiting step for the removal of TT on both WC and CC biochar, while intraparticle diffusion was the rate-limiting step for the adsorption of EB. Maximal experimental adsorption capacities Q_maxexp of TT reached 182 ± 5 (WC) and 45 ± 2 mg g⁻¹ (CC), and EB 12.7 ± 0.9 (WC) and 1.5 ± 0.4 mg g⁻¹ (CC), respectively, thereby indicating a higher affinity of biochars for TT. The adsorption mechanism was found to be associated with π-π interaction, hydrogen bonding, and pore filling. Application of the innovative dynamic approach based on fast-field-cycling NMR relaxometry indicates that variations in the retention of water-soluble dyes could be explained by distinct water dynamics in the porous structures of WC and CC. The obtained results suggest that studied biochars will be more effective in adsorbing of cationic than anionic dyes from contaminated effluents.

Thermochemical conversion of garden waste to biochar was carried out to prepare a green adsorbent for the removal of Cs, Cu, Ni, and Pb, which was characterized by XPS, SEM–EDX, and FT-IR analyses. The biocharˊs adsorption capacity was 20.5(Cs), 25.2(Cu), 12.4(Ni), and 45.9(Pb) mg g⁻¹ and demonstrated satisfactory performance for different pH values. The kinetics data evaluation revealed that besides chemisorption, intraparticle diffusion contributes to metal removal. Moreover, the physical and structural properties of biochar play an important role in adsorption. Results indicate the suitability of using GW biochar as an alternative sorbent for both radionuclides and metal extraction.

Microwave synthesized iron oxide nanoparticles and microparticles were used to prepare a magnetically responsive biosorbent from Rhytidiadelphus squarrosus moss for the rapid and efficient removal of Co²⁺ ions and thioflavin T (TT). The biocomposite was extensively characterized using Fourier transformed infrared (FTIR), XRD, SEM, and EDX techniques. The magnetic biocomposite showed very good adsorption properties toward Co²⁺ ions and TT e.g., rapid kinetics, high adsorption capacity (218 μmol g⁻¹ for Co and 483 μmol g⁻¹ for TT), fast magnetic separation, and good reusability in four successive adsorption–desorption cycles. Besides the electrostatic attraction between the oxygen functional moieties of the biomass surface and both Co²⁺ and TT ions, synergistic interaction with the –FeOH groups of iron oxides also participates in adsorption. The obtained results indicate that the magnetically responsive biocomposite can be a suitable, easily separable, and recyclable biosorbent for water purification.