| dc.description.abstract | Two different samples of a micaceous mineral, herein referred to as MicaMA
and MicaMB obtained from two separate sources here in Kenya, were utilized as
inexpensive and effective adsorbents for the removal of heavy metal ions (Cu2+,
Cr3+, Cd2+ and Pb21from aqueous solutions.
The effects of contact time, pH, temperature, adsorbate and adsorbent
concentration, acid- washing of mineral were investigated. Maximum removal of the
metal ions took place over the pH range of 4.0 to 7.0. The adsorption of the metal
ions increased with increase in the ratio of dose of mineral to concentration of metal
ion and decreased with increasing adsorbent particle size. Temperature was found to
have negligible effect on adsorption from 25°C to 60°C. Acid washing of the mineral
samples showed drastic reduction in % adsorption for both Micalvl., and MicaMB. 20
minutes equilibration time was found to be adequate, yielding almost 100%
adsorption at low concentration of metal ions (less than 100 ppm). Sonication was
generally found to improve % adsorption and this was attributed to the possible deaggregation
of the mineral particles, thereby exposing more adsorption sites.
Isotherm studies showed that uptake of metal ions occurred by monolayer
sorption with the eventual formation of a plateau at saturation. Freundlich adsorption
isotherms showed higher adsorption capacity by micaMA than micaMB for all the
metal ions investigated, with all adsorption isotherms yielding values for adsorption
intensity, n, higher than 1.This indicated favourable adsorption. | en |
