Polyaniline Emeraldine Salt for Removal of Dyes from Wastwater

Water pollution is one of the recent concerns of the whole world. Because A large number of natural and unnatural pollutants have been released from human and industrial resources and have rapidly reduced the quality of water resources. These pollutants have many destructive effects that can be a major threat to human health. Therefore, the removal of water pollutants is very important [۱]. There are several common methods to minimize these pollutants, such as filtration, precipitation, coagulation and adsorption. Polymeric materials possesingthe active sites such as polyaniline have been investigated for the removal of aqueous contaminants [۲].In this study, nanofibers of polyaniline was synthesized in the emeraldine salt (ES) form and used as adsorbent to investigate the removal of several different cationic and anionic pollutants from aqueous media. Removal experiments were performed at room temperature and pH= ۴,with dye initial concentration of ۲۵ mg/L over ۱ hour. The concentrations of pollutants were calculated according the Beer-Lambert law and by UV-vis spectroscopy at λmax values of ۴۶۴, ۶۶۴, ۴۲۴ and ۵۹۱ nm for methyl orange (MO), methylene blue (MB), bromocresol green (BCG) and crystal violet (CV), respectively. The concentration of dye in the solution was monitored with time during the adsorption experiment. According to the results shown in the figure above, the emeraldine salt of polyaniline is not able to remove cationic dyes while it is an effective and selective adsorbent for the removal of anionic dyes. The removal of anionic dyes from water can be explained by electrostatic interaction between anionic concomitants and positively charged sites on the polyaniline emeraldine salt.