Boron Removal from Aqueous Solutions by Using a Novel Alginate-Based Sorbent: Comparison with Al₂O₃ Particles

Boron removal was evaluated in the present work by using calcium alginate beads (CA) and a novel composite based on alginate-alumina (CAAl) as sorbents in a batch system. The effects of different parameters such as pH, temperature, contact time, and composition of alginate (at different concentrations of guluronic and mannuronic acids) on boron sorption were investigated. The results confirm that calcium alginate beads (CA) exhibited a better adsorption capacity in a slightly basic medium, and the composite alginate-alumina (CAAl) exhibited improved boron removal at neutral pH. Sorption isotherm studies were performed and the Langmuir isotherm model was found to fit the experimental data. The maximum sorption capacities were 4.5 mmol g^-1 and 5.2 mmol g^-1, using CA and CAAl, respectively. Thermodynamic parameters such as change in free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) were also determined. The pseudo-first-order and pseudo-second-order rate equations (PFORE and PSORE, respectively) were tested to fit the kinetic data; the experimental results can be better described with PSORE. The regeneration of the loaded sorbents was demonstrated by using dilute HCl solution (distilled water at pH 3) as eluent for metal recovery.