Watermelon rind (WR) an agro waste was evaluated as an adsorbent for the removal of
Cr3+ ions from aqueous solution. Batch mode adsorption studies were performed by varying
parameters such as pH, contact time, adsorbent dose and initial metal ion concentration. Maximum
loading capacity of WR was found to be 172.6 mg g1 for Cr3+ ions at pH 3. Kinetic studies show
that removal of Cr3+ ions is rapid and follows a pseudosecond order model. Equilibrium data fit
better with the Langmuir isotherm than the Freundlich isotherm. Thermodynamic parameters such
as DG, DH and DS were derived for the current system. The negative values of DG show that the
nature of sorption process is spontaneous. FTIR studies reveal that hydroxyl and carboxyl groups
were responsible for uptake of metal ions. Successive desorption of Cr3+ ions reveals that WR can
be an economical sorbent for the removal of heavy metals from aqueous solution. The results conclude
that watermelon rind an agro waste can effectively be used for the removal of chromium ions
from aqueous solution.
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