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Synthesis of Polypyrrole-Modified Layered Double Hydroxides for Efficient Removal of Cr(VI)
journal contribution
posted on 2019-09-11, 14:44 authored by Sumanta Sahu, Padmaja Kar, Nisarani Bishoyi, Laxmi Mallik, Raj Kishore PatelDesigning a stable, selective, and
efficient adsorbent for the removal of pollutants like chromium poses
serious concern. Herein, an organic–inorganic hybrid material,
polypyrrole (PPY)-modified Mg–Al layer double hydroxide, has
been reported as an adsorbent for Cr(VI) removal. The inorganic framework
Mg–Al layer double hydroxides (LDHs) are synthesized via coprecipitation
followed by hydrothermal treatment. The synthesized LDHs are enriched
with polypyrrole coating via in situ oxidative polymerization followed
by microwave irradiation. The structure of the as-synthesized composite
was delineated using various characterization techniques like field
emission scanning electron microscopy, transmission electron microscopy,
X-ray powder diffraction, Fourier-transform infrared spectroscopy,
Raman, Brunauer–Emmett–Teller, thermogravimetric analysis–differential
thermal analysis, and X-ray photoelectron spectroscopy. The PPY-LDHs
are applied toward the abatement for Cr(VI) from aqueous solutions
at varying temperatures. The maximum Langmuir adsorption capacity
of PPY-LDHs is 76.21 mg g–1. The high distribution
coefficient (Kd) value (>104 mL g–1) reveals the great affinity of the PPY-LDHs
for Cr(VI). The PPY-LDHs showed poor regeneration efficiency. The
adsorption mechanism is proposed, which asserts that the removal of
Cr(VI) onto the adsorbent was a combined effect of reduction of Cr(VI)
to Cr(III) and chemical sorption that takes place through ion exchange
in the interlayer regions on the surface through electrostatic attractions
and hydrogen bonding. Hence, PPY-LDHs is an ideal adsorbent for the
treatment of Cr(VI).
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Keywords
characterization techniquesremovaladsorption mechanismmicrowave irradiationion exchangeLDHregeneration efficiencydistribution coefficientX-ray powder diffractionfield emission scanning electron microscopyPPY-LDHhydrothermal treatmentPolypyrrole-Modified Layered Double Hydroxidestransmission electron microscopyEfficient RemovalLangmuir adsorption capacityCrinterlayer regionschemical sorptionpolypyrrole coatingoxidative polymerizationPPYadsorbentX-ray photoelectron spectroscopy
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