Four modified bentonites (La(III), Y(III), Fe(III)) were prepared by ion exchange
process to remove arsenite (III) ions from water. The modified bentonites were examined
with X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The rare earth
(REE) and Fe(III) ion content in bentonite was higher than the CEC values obtained
by ammonium acetate method related to trivalent ions (2.7 x 10(-4) mol g(-1)). The
kinetics, equilibrium time, sorption isotherms and desorption experiments were examined.
Lanthanum, yttrium and cerium bentonite can bind similar amount of arsenite(III) ions.
Iron-bentonite cannot bind significant amounts of arsenite ions. The active sites
and the solubilities of the sorption complex were determined. Arsenite (III) ions
sorb in the interlayer space as REEAsO3. The solubility of the arsenite complex was
two orders of magnitude smaller than that of the phosphate complex. After desorption
the eluted amount of arsenite (III) was 55% related to the sorbed amount of arsenite.
The d(001) basal spacing of modified bentonites and that of after sorption and desorption
was measured. After the sorption of arsenite ion on lanthanum bentonite, the d(001)
basal spacing of montmorillonite was decreased and after desorption an increase in
d(001) basal spacing was observed again. Modified bentonites can be used for removing
arsenic ions from water.