The experimental methodology achieved in the present study signified that
the adsorption and precipitation were mainly mechanisms occurred together in the
removal of nickel from aqueous solutions by sorption using cement kiln dust (CKD)
byproduct as sorbent. Finding the contribution of each mechanism in the removal
process and derivation an analytical model for finding the portion of precipitation
were the focal points of this work. Results proved that the pure precipitation was
increased with the increase of CKD dosage and metal concentration where total
removal (adsorption-precipitation) ranged from 45 to 100%. The SEM micrographs of
the CKD sorbent before and after sorption process certified that there was a crystal
precipitates on the surface of the CKD. Also, these graphs in combination with FT-IR
tests proved that [Ni(OH2)n]+2 (n=4-6) species were bonded with CKD and insoluble
hydroxide species may be precipitated onto the CaO surfaces by co-precipitation,
while K-O, Si-O and Ca-O groups enhanced the adsorption mechanism