Graphene-Oxide-Coated, Polypyrrole-Supported, Nano Zerovalent Iron Nanocomposites for Adsorption of Hexavalent Chromium from Wastewater

The hexavalent chromium in water is extremely toxic to most living organisms and can cause many diseases. In this work, we developed Polypyrrole (PPy), Polypyrrole/graphene oxide (PPy/ GO) nanocomposite, and Polypyrrole/graphene oxide/zerova-lent iron nanoparticles (PPy/GO/n-ZVI) nanocomposite for adsorption of Cr (VI) from water. PPy/GO nanocomposite showed the highest Cr (VI) removal capacity for 10% (weight) loading of GO. PPy/GO/n-ZVI nanocomposite showed the highest Cr (VI) adsorption capacity for 50 % iron nanoparticle loading. Chemical kinetics data showed that Cr (VI) adsorption occurred with pseudo-second-order. The maximum adsorption capacity (q(max)) was found to be 64.29 mg/g, 129.09 mg/g, and 171.04 mg/g on PPy, PPy/GO nanocomposite, and PPy/GO/n-ZVI nanocomposite respectively. The thermodynamic study showed a positive value of delta S, and a negative value of delta G indicated rise in the disorder at the adsorbate-adsorbent interface and spontaneous nature of Cr (VI) adsorption. delta H was close to 21 kJ/mole indicating adsorption process occurred via physisorption. The recycling of the adsorbent was carried out by washing with sodium hydroxide and Cr (VI) removal efficiency decreased by around twenty % in the fifth cycle. The present study suggests that the PPy/GO/n-ZVI nanocomposite is an environment-friendly magnetic material and provides a simple, low-cost strategy for the adsorption of Cr (VI) from wastewater.