Facile Fabrication of Biochar/Al2O3 Adsorbent and Its Application for Fluoride Removal from Aqueous Solution

In this research, pristine and boron-doped biochar/Al2O3 adsorbents for fluoride removal from aqueous solutions were prepared by employing chitosan (CS), poly(vinyl alcohol) (PVA), and AlCl3·6H2O as the raw materials. CS was dissolved in AlCl3·6H2O aqueous solution, and the CS/PVA aerogel was prepared by a freezing process. The biochar/Al2O3 was obtained by the carbonization process at high temperature. AlCl3·6H2O was used as both the solvent for CS and the source for Al2O3. The structure of biochar/Al2O3 was characterized by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The adsorption performance of biochar/Al2O3 for fluoride was evaluated by the batch adsorption experiment. Furthermore, the effect of HBO3 cross-linking on the adsorption property of biochar/Al2O3 was studied. The results showed that the HBO3 cross-linking process would promote the adsorption performance of biochar/Al2O3. The adsorption kinetics and equilibrium properties are well-described with a pseudo-second-order equation and Freundlich model, respectively. The Qe for biochar/Al2O3 could reach 196.1 mg/g. The high adsorption capacity would enable the biochar/Al2O3 to be useful for real contaminated water treatment. This paper provides a valuable and economic solution for the utilization of CS.