High efficient removal of chromium(VI) using glycine doped polypyrrole adsorbent from aqueous solution

Glycine doped polypyrrole (PPy-gly) adsorbent was prepared via in situ polymerization of pyrrole (Py) monomer in the presence of glycine (gly) for the removal of Cr(VI). Formation of PPy homopolymer and inclusion of gly in the PPy matrix were confirmed by ATR-FTIR and XRD, respectively. Field emission scanning electron microscopic imaging of PPy-gly revealed the formation of nearly spherical agglomerated particles. The adsorption of Cr(VI) onto the PPy-gly adsorbent was highly pH dependent and removal efficiency by PPy-gly was much higher compared to PPy homopolymer. The kinetic process followed pseudo-second-order rate model with equilibrium reached within 30–150 min. Intra-particle diffusion model was also applied for better understanding of kinetic mechanism. Isotherm data fitted well with the Langmuir isotherm model with maximum adsorption capacity of 217.39–232.55 mg/g at 25–45 °C. Desorption experiment showed PPy-gly can be regenerated and reused for three consecutive cycles without loss of its removal efficiency. The adsorption process for the removal of Cr(VI) was governed by the ionic interaction between protonated amine groups of gly and HCrO4- ions.

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► High efficient adsorbents, PPy-gly were synthesized as an effective adsorbent for Cr(VI).
► Doping of glycine in the polypyrrole matrix was confirmed by ATR-FTIR and XRD studies.
► The maximum adsorption capacity was found to be 217 mg/g at 25 °C.
► The adsorption kinetics is rapid and fitted well with pseudo-second order model.
► The adsorption is an endothermic in nature.