Fe(III) and Zr(IV) surface functionalized 1-D hydrogen titanate nanotubes for remediating fluoride from water at neutral pH

Abstract

The current study deals with Fe(III) and Zr(IV) incorporated Titanate Nanotubes (FZTNT) for efficient removal of fluoride from potable water. The surface modification of hydrogen titanate nanotubes (HTNT) with Fe and Zr ions, not only transformed the adsorbent surface suitable for fluoride adsorption at neutral pH, but also enhanced its fluoride adsorption capacity. The surface charge of the adsorbent was estimated by zeta potential measurements. The other physical and chemical properties of the FZTNT were examined using BET, FTIR and XPS. FZTNT had specific surface area of 245 m2/g. The crystal structure, morphology and chemical characterizations were carried out using the XRD, TEM, and SEM-EDX respectively. The fluoride adsorption data followed the Langmuir isotherm and the Langmuir adsorption capacity was estimated to be 229.3 mg/g at neutral pH, contact time of 2 h and adsorbent dosage of 1 g/L. FZTNT exhibited superior adsorption properties, compared to HTNT which had negligible adsorption at pH 7 (±0.01). Adsorption of fluoride followed ion exchange mechanism. In addition, FZTNT possessed good adsorption kinetics and could be reused for three cycles without significant drop in its adsorption capacity which allowed FZTNT to be used for defluoridating groundwater to WHO limits (≤1.5 mg/L).