Adsorption Studies of Cr (VI) ions onto Hematite, Activated Carbon and their Composite

Abstract

Water pollution by heavy metals has become a major environmental issue. The present work
investigated the adsorptive removal of hexavalent chromium from aqueous solution on the three
adsorbents, Hematite (HEM), Moringa oleifera pod activated carbon (MAC) and their composite
(HEMAC). The adsorption of Cr (VI) ions was conducted using batch experimental method. The
effect of initial metal ions concentration (25-250 mg/L), adsorbent dosage (0.01 to 0.05 g), contact
time (30-180 min), pH (2-8) and temperature (303-343 K) on the adsorption capacity of these
adsorbents were evaluated and optimized. The Cr (VI) ions at an initial concentration of 200 mg/L
gave the maximum adsorption capacity of 7.27 mg/g, 7.33 mg/g and 12.02 for HEM, MAC and
HEMAC respectively. The equilibrium data obtained from the adsorption studies was fitted using
the Langmuir, Freundlich and Temkin isotherm models, the adsorption process was best described
by the Temkin isotherm model. The kinetic and thermodynamic studies revealed that the prepared
Hematite and activated carbon are efficient adsorbents and the Moringa oleifera pod activated
carbon gave a more favourable adsorbent for the removal of heavy metal in waste water.