Abstract:
Stem of Water Hyacinth (SWH), an aquatic plant in lake Awash was low cost raw material
which was used to prepare activated carbon. It was synthesized by chemical activation using
phosphoric acid followed by carbonization at 550 0C for 1:30 hours. The activated carbon Was
used to remove Cr(VI) from aqueous solutions. The concentration of Cr(VI) was determined by
Uv-visible spectroscopy instrument. For obtaining its maximum removal, batch experiments
were carried out at different parameters including initial Cr(VI) ion concentrations, mass of
adsorbent, contact time and pH of the solutions were studied. The FT-IR spectra of SWH
activated carbon before and uptake of Cr(VI) were recorded to explore the nature of the
functional groups responsible for its binding onto the adsorbent. FT-IR band results were
obtained at 3424, 2371, 1639, 1169 and 1007 cm-1 (O-H stretch, C-H stretch, C=O stretching,
and C=C bending vibrations respectively). The SWH activated carbon XRD result showed the
appearance of the one peak at 20o
in the XRD result meets some developed crystallity but fitted
with amorphous materials. The maximum removal of Cr(VI) ion (95.5%) was achieved at pH= 2,
adsorbent dosage=1.0 gram, time 60 min at Cr(VI) ion concentration 30 mg/L. The equilibrium
characteristics of Cr(VI) adsorption was described and The data fitted by Langumuir and
Freundlich isotherms equations. But Freundlich isotherm with higher R2
(0.995) was best fitted to
the experimental values. The R2
value for pseudo-first order(0.874) in the adsorption of Cr(VI)
ions were higher than that of pseudo-second order(0.226) for the Cromium metal ion. The
kinetics data was best fitted with the pseudo-first order type. Adsorbent present in this study was
prepared at laboratory scale and its efficient for Cr(VI) ion from aqueous solution and could be
an alternative promising weed plant based on adsorbent in field.
