Removal of Chromium (VI) from Aqueous Solution Using Exfoliated Graphite/Polyaniline Composite

Abstract

Exfoliated graphite/polyaniline (EG/PANI) composites were successfully prepared via in situ polymerization of aniline monomer in the presence of exfoliated graphite. The PANI precipitated into the interlayer space of the graphite flake significantly improving physiochemical properties of EG. The particle morphology and interaction of the EG and PANI was determined using the scanning electron microscopy (SEM). The SEM images clearly showed the formation of PANI and EG/PANI composite with PANI greatly covering the EG flake. The presence of polyaniline and its major functional groups were confirmed using Fourier Transform Infrared Spectroscopy (FTIR) between 3,500 – 3,000 cm^-1 and 1,500 - 500 cm^-1. A 68 % change in Brunauer- Emmett-Teller (BET) surface area was observed in the 0.35 g PANI/g EG after the in situ polymerization of the PANI. The effectiveness of the composite adsorbent on the removal of Cr (VI) from aqueous solutions was evaluated by evaluating the effects of parameters such as EG to PANI ratio and initial concentration. The optimum composite loading was found to be 0.35 g PANI/g EG and removed more than 99 % of Cr (VI) from an initial concentration of 100 ppm was removed at 20 g/L loading within 4 h. The Freundlich adsorption isotherm model best described the adsorption of Cr (VI) with a regression coefficient, r² of 0.99 showing the heterogeneous adsorption at the surface of the composite. The maximum capacity of the composite was 38.20 mg/g.