Abstract:
Millions of people across the globe suffer from health issues related to high fluoride levels
in drinking water. The purpose of this study was to test modified pumice as an adsorbent for the
purification of fluoride-containing waters. The adsorption of fluoride onto zirconium-coated pumice
(Zr–Pu) adsorbent was examined in fixed-bed adsorption columns. The coating of zirconium on
the surface of VPum was revealed by X-ray diffractometer (XRD), Inductively coupled plasma optical emission spectroscopy (ICP-EOS), and X-ray fluorescence (XRF) techniques. The degree of
surface modification with the enhanced porosity of Zr–Pu was evident from the recorded scanning
electron microscope (SEM) micrographs. The Brunauer-Emmett-Teller (BET) analysis confirmed the
enhancement of the specific surface area of VPum after modification. The Fourier transform infrared
(FTIR) examinations of VPum and Zr–Pu before and after adsorption did not reveal any significant
spectrum changes. The pH drift method showed that VPum and Zr–Pu have positive charges at
pHPZC lower than 7.3 and 6.5, respectively. Zr–Pu yielded a higher adsorption capacity of 225 mg/kg
(2.05 times the adsorption capacity of VPum: 110 mg/kg), at pH = 2 and volumetric flow rate (QO)
of 1.25 mL/min. Breakthrough time increases with decreasing pH and flow rate. The experimental
adsorption data was well-matched by the Thomas and Adams-Bohart models with correlation
coefficients (R2
) of ≥ 0.980 (Zr–Pu) and ≥ 0.897 (VPum), confirming that both models are suitable
tools to design fixed-bed column systems using volcanic rock materials. Overall, coating pumice with
zirconium improved the defluoridation capacity of pumice; hence, a Zr–Pu-packed fixed-bed can be
applied for defluoridation of excess fluoride from groundwater. However, additional investigations
on, for instance, the influences of competing ions are advisable to draw explicit conclusions.
