Polyaniline Coated Ethyl Cellulose with Improved Hexavalent Chromium Removal

The ethyl celluloses (ECs) modified with 5.0, 10.0, and 20.0 wt % polyaniline (PANI) (PANI/ECs) prepared by homogeneously mixing the EC and PANI formic acid solutions have demonstrated a superior hexavalent chromium (Cr(VI)) removal performance to that of pure EC. Having an increased Cr(VI) removal percentage with increased PANI loading, the PANI/ECs with 20.0% PANI loading were noticed to remove 2.0 mg/L Cr(VI) completely within 5 min, much faster than the pristine EC (>1 h). A chemical redox of Cr(VI) to Cr(III) by the active functional groups of PANI/ECs was revealed from the kinetic study. Meanwhile, isothermal study demonstrated a monolayer adsorption behavior following the Langmuir model with a calculated maximum absorption capacity of 19.49, 26.11, and 38.76 mg/g for the 5.0, 10.0, and 20.0 wt % PANI/ECs, much higher than that of EC (12.2 mg/g). The Cr(VI) removal mechanisms were interpreted considering the functional groups of both PANI and EC, the valence state fates of Cr(VI), and the variation of solution acidity.