Exfoliated polypyrrole/montmorillonite nanocomposite with flake-like structure for Cr(VI) removal from aqueous solution

Abstract

Exfoliated polypyrrole/montmorillonite (PPy/MMT) nanocomposites with flake-like structure were prepared by in situ chemical oxidation polymerization. Amphoteric polymer, (2-methacryloyloxyethyl) trimethyl ammonium chloride and methacrylate acid copolymer, was used to modify montmorillonite and a large amount of carboxyl acid was introduced on the surface of clay platelets which can play a ‘bridge’ role to combine PPy with clay. The adsorption of Cr(VI) on the PPy/MMT was highly pH-dependent and the adsorption kinetics followed the pseudo-second-order model. The Langmuir isothermal model well described the adsorption isotherm data, whiler the maximum adsorption capacity increased with the increase of temperature. Thermodynamic investigation indicated that the adsorption process is spontaneous, endothermic and marked with an increase in randomness at the adsorbent–liquid interface. The maximum adsorption capacity of the PPy/MMT composites for Cr(VI) was 166.7 mg/g. A desorption experiment showed PPy/MMT composites can be regenerated and reused for two consecutive cycles with no loss of their removal efficiency.