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In this study, zirconium(IV)-chitosan (Zr-CTS) hydrogel beads were synthesized for boron(III) removal. Zr-CTS was characterized by a series of experimental techniques, including SEM, XRD and FTIR. Kinetic, isotherm, and thermodynamic investigations were employed to understand the adsorption behavior. It was found that boron removal is a pH-dependent process, having the highest performance at pH 6–7. It was also shown that the process of boron adsorption follows the pseudo-second-order kinetic model and is dependent on Zr(IV) content in hydrogel beads, achieving the maximum adsorption capacity of 24.5 mg/g. Thermodynamic constants demonstrated a feasible, spontaneous, and endothermic adsorption. Boron removal by Zr-CTS was found to occur through the adsorption of boron species on the surface of amorphous zirconium hydroxide via complexation mechanism. The results indicated that due to its efficiency in removing boron, good regeneration capacity and convenient form, Zr-CTS might be considered as a promising adsorbent for water purification. [ABSTRACT FROM AUTHOR]

Various metal-oxide nanoparticles and chitosan were blended to form new adsorbents (M-Oxide-CTS) for removing boron from aqueous solutions in a batch system. The maximum boron adsorption capacity (q= 7.8 mg/g) was reached at pH = 4 within 5 min. Calculations based on Langmuir, Freundlich, and Dubinin–Radushkevich models showed the heterogeneous and physical nature of boron adsorption on M-Oxide-CTS. Modeling of the thermodynamic date indicated the nonspontaneous and exothermic process. The pseudo-second-order model adequately described the boron adsorption on M-Oxide-CTS. Desorption by means of alkaline solution at pH = 12 was carried out successfully. [ABSTRACT FROM AUTHOR]

Boron is an essential element for plants and living organisms; however, it can be harmful if its concentration in the environment is too high. In this paper, lanthanum(III) ions were introduced to the structure of chitosan via an encapsulation technique and the obtained hydrogel (La-CTS) was used for the elimination of the excess of B(III) from modelling solutions. The reaction between boric acid and hydroxyl groups bound to the lanthanum coordinated by chitosan active centres was the preponderant mechanism of the bio-adsorption removal process. The results demonstrated that La-CTS removed boric acid from the aqueous solution more efficiently than either lanthanum hydroxide or native chitosan hydrogel, respectively. When the initial boron concentration was 100 mg/dm3, the maximum adsorption capacity of 11.1 ± 0.3 mg/g was achieved at pH 5 and the adsorption time of 24 h. The successful introduction of La(III) ions to the chitosan backbone was confirmed by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy, Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Due to its high-performance boron adsorption-desorption cycle and convenient form, La-CTS seems to be a promising bio-adsorbent for water treatment. [ABSTRACT FROM AUTHOR]