Polymer composite for low-level detection of hazardous dyes: electrochemical sensing behavior

In the recent era, the growing demand for fresh water is increasing day by day due to the enhancement of colored effluents released from leather, drugs, and textiles industries altering all the aquatic and human life. Therefore, the treatment of wastewater is of prior importance so the aquatic and human life will not be affected anymore. Different approaches have been applied for the removal of pollutants from wastewater, among them, electrochemical sensing of hazardous dyes is an important electroanalytical method that can determine the pollutant concentration from ppm to ppb level. Therefore, a novel approach has been applied for sensing hazardous dyes from wastewater using a polymeric composite based on conducting polymer and carbon-based material, i.e., polyaniline and graphene oxide. Polymeric composite shows excellent sensitivity toward cationic dye, i.e., crystal violet as compared to anionic dye, i.e., alizarin red S. The equilibrium time achieved for both dyes is about 180 min. However, the maximum drop in peak current was found to be for crystal violet, i.e., 57 mu A from 108 mu A, whereas, in the case of alizarin red S, the drop was 71 mu A from 108 mu A. The sensing of both charged dyes follows pseudo-first-order kinetics and the Freundlich isotherm model. Besides cyclic voltammetry, the sensing was also tested using impedance spectroscopy. From the bode plot, it was inferred that impedance increases with an increase in concentration from 653-4133 omega and 653-6890 omega for alizarin red S and crystal violet, respectively, indicating high selectivity of polymeric composite toward crystal violet.