Effective removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions using polyaniline recovered from non-recyclable pigment effluent via electro polymerization

Abstract

Electro conducting polymer - polyaniline is used as a pigment in the epoxy based coating system. These pigment developing industries releases unreactive monomers and dimers of aniline compound (byproducts of chemical polymerization) in the effluent which creates environmental issues. The present study focuses on the recovery of polyaniline from the pigment effluent by electrochemical polymerization method. The aniline monomers were polymerized on the graphite plate as emeraldine base form at an anode potential of 0.6 to 0.68 V with simultaneous decrease in its monomer concentration. The recovered polyaniline (PANI) exhibited smooth rod shape morphology and displayed (011), (020) and (200) crystal planes for the emeraldine base form in X-ray diffraction studies. The recovered PANI was subjected to carbonization and activation (PANI-AC) for its application in adsorptive removal of 2,4-dichlorophenoxyacetic acid (2,4-D) removal. The PANI-AC outperformed commercial activated carbon in removing 50 ppm of 2,4-D from water matrix. The 25 ppm of PANI-AC adsorbent was able to remove 100 %, 85 %, 57 % and 29 % of 100 μg L−1, 250 μg L−1, 500 μg L−1 and 1000 μg L−1 of 2,4-D respectively. The 2,4-D adsorptive removal followed a pseudo second order kinetic model and obeyed Langmuir and Freundlich isotherms. The maximum adsorption capacity of the PANI-AC is of 34.48 mg g−1 (Langmuir isotherm). These findings direct the possible recovery of polyaniline form pigment effluent of paint industries and its application as adsorbent in efficient removal of 2,4-D from aqueous matrix.