The Removal of Cr3+ And Pb2+ from Aqueous Solution using Modified Starches from Forest Anchomanes (Anchomanes difformis)

Abstract

Water contamination by heavy metals is a global challenge requiring eco-friendly
remediation. Progressive discharge of heavy metals in large water bodies has
necessitated the need to look for cheap and readily available adsorbents for
removal of dissolved metals ions in waters. The potential of modified forest
Anchomanes starches as adsorbent for the removal of Cr3+ and Pb2+ are presented
in this study. Starch from forest Anchomanes tubers was isolated, chemically
modified by carboxylation and acetylation processes and characterized with FTIR.
On the adsorption of the metal ions, the effects of pH, contact time, starting
concentration, and adsorbent dosage were examined. Batch adsorption kinetic and
isotherm studies were also done for the uptake. The optimum condition for
adsorption were 150 mins, pH 6 and 1.2 g/L adsorbent dosage. The adsorption
isotherm studies indicated that the Langmuir model was suitable and appropriate
for the adsorption of Cr3+ onto acetylated (ACS) adsorbent while Freundlich
isotherm model was suitable for the uptake of Cr3+ onto carboxymethylated (CMS)
adsorbent and Pb2+ uptake on both adsorbents. Pseudo-second order kinetics best
describe adsorption of Cr3+ and Pb2+ to ACS whereas, Elovich and Pseudo-firstorder
kinetic models best describe adsorption of Cr3+ and Pb2+ on CMS
respectively. The results indicate that modified Anchomanes difformis starches are
effective and efficient in the removal of Cr3+ and Pb2 in wastewater.