Abstract:
Millions of people across the globe suffer from
health issues related to excessive fluoride levels in
drinking water. The objective of this study was to test
natural and modified rock materials as adsorbents
for the cleanup of fluoride-laden waters. Fluoride
uptake onto natural pumice and zirconium–coated
pumice (Zr – Pu) packed fixed-bed adsorption
column was investigated. The extent of surface
modification with enhanced porosity of Zr – Pu was
evident from recorded SEM micrographs. A FTIR
study of pumice and Zr – Pu before and after
adsorption did not reveal any significant structural
changes. The pH drift method demonstrated that
pumice and Zr – Pu possesses positive charges at
Keywords: adsorption; defluoridation; fluoride;
pumice; zirconium – coated
pHPZC lower than 7.3 and 6.5, respectively. The
highest removal capacity of 225 mg/kg and 110
mg/kg were gained for Zr – Pu and pumice,
respectively at pH = 2 and QO = 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 (natural pumice), confirming
that the models are appropriate tools to design fixed
bed column systems using volcanic rock materials.
Overall, coating of pumice with zirconium improved
the defluoridation capacity of pumice, hence, Zr – Pu
packed fixed-bed could be applied for the
defluoridation of excess fluoride from groundwater.
However, additional investigations on, for instance,
competitive ions effects are advisable to draw
definite conclusions.
