Functionalization of Biopolymers for the Treatment of Heavy Metals from Aqueous Medium
Date
2014
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Department of Chemistry
Abstract
The industrial discharge of heavy metals into waters' course is one of the major
pollution problems affecting water quality and human health. Therefore, they
must be removed prior to their discharge into waste streams. For this novel cause
several types of treatment methods are in use. Among them use of biowaste is
emerging as the best method. Therefore different types of agricultural by-products
have been explored for their efficiency in removing heavy metal ions from
aqueous solution. In this regard a biomass of Desmostachya bipinnata (DB) was
investigated as the potential bio-adsorbent for the removal of Cd(II), Pb(II),
Cu(II) and Zn(II) from wastewater. DB is a sacrificial herb in the south Asian
region particular to Hindu religion with medicinal value. It is found to be very
effective in the phyto-accumulation of heavy metals from soil as well as from
polluted water. This is the first adsorption studies ever performed with DB as the
novel bio-sorbent in the removal of heavy metal ions.
Nitrogen functional groups were grafted onto the polymeric backbone of DB with
hydrazine monohydrate, dimethylamine and ethylenediamine respectively, for the
better adsorption. The characterization of biopolymer was done using SEM,
DRFTIR, elemental analysis, zeta potential, XRD and TG/DTA. The
characterization results of biopolymer revealed to indicate proper
functionalization with nitrogen groups.
The effect of pH, initial concentration and contact time of the metal solution
were monitored by batch method. The maximum adsorption capacities determined
for Cd(II), Pb(II) Cu(II) and Zn(II) were 76.8 mg/g, 130.4 mg/g, 72.1 mg/g and
58.16 mg/g, respectively, at their optimum pH. The equilibrium data were
analyzed using Langmuir and Freundlich isotherm models. Langmuir isotherm
model fitted well and the rate of adsorption followed the pseudo second order
kinetic. The experiments on regeneration and reuse of biopolymers were
conducted with batch method. The results indicated that more than 90% of heavy
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metals were regenerated and the biopolymers were used for six successive cycles
with 90% efficiency.
Thus, the adsorbents derived from DB can be used as an effective, efficient, low
cost and environment friendly material for the removal of Cd(II), Pb(II), Cu(II)
and Zn(II) from the aqueous medium.
Keywords: Desmostachya bipinnata, Biosorption, Heavy metals, Batch
experiment, Pseudo- second order kinetic model, Functionalization, Low cost,
Pollution, Biosorbent.
Description
Keywords
Desmostachya bipinnata, Biosorption, Heavy metals, Batch experiment, Functionalization, Low cost