Removal of fluoride by carbohydrate-based material embedded with hydrous zirconium oxide nanoparticles

Herein, we fabricated a novel carbohydrate-based adsorbent by using the pomelo peel (PP) as the biocarrier. The virgin PP was embedded with hydrous zirconium oxide (HZO) nanoparticle, forming the HZO-PP composites for highly efficient fluoride adsorption. Characteristics of HZO-PP were determined by TEM, SEM, XPS, XRD, BET surface area, and FTIR. The result showed that HZO nanoparticles have been successfully anchored onto the inner pore of PPs, which play a significant role in defluorination. It is favorable for fluoride uptake with more acidic solution, which greatly enhanced the interfacial reaction between the fluoride ions and protonated HZO through electrostatic interaction or electro-dipole interaction. No significant Zr leaching and organic dissolution were observed within pH 3.0-11.0; this indicated the strong interfacial reaction between the biocarrier and HZO, which illustrated the high stability of the HZO-PP for use. Competing tests indicated that fluoride uptake by HZO-PP still retained about 76-88% as the concentrations of coexisting NO₃^- or SO₄^2- was 25 times higher than that of F^-. The HZO-PP in column after six adsorption-regeneration cycles still retained 94% of adsorption capacity (15.4 mg/g). All these results implied that biomaterials anchored with multivalent metal oxides represented the potential nanocomposites for fluoride removal.