Conducting polyaniline nanotubes with silver nanoparticles in the separation of thiocyanate from aqueous media

Thiocyanate anions represent serious environmental hazards and the ways for their extraction from ecosystem are sought. In the testing of new adsorbents, polyaniline nanotubes have been utilized as a host polymer in which silver nanoparticles were distributed to produce polyaniline nanotubes/silver nanocomposite. The interaction of thiocyanate anions in aqueous medium with the nanocomposite deposited on the quartz-crystal microbalance was studied. The results indicated that polyaniline nanotubes adsorb thiocyanate anions, and silver nanoparticles are suspected in addition to catalyze the transformation of thiocyanate. The extraction of thiocyanate anions using nanocomposites from the aqueous solution was then monitored with the UV–visible spectroscopy. The effect of different parameters including concentration, adsorbent dose, and pH has been mentioned. The pH effect demonstrated that ion exchange and electrostatic interaction as well as chemisorption mechanisms are involved in the adsorption. The results were fitted into various kinetic models. It was concluded that pseudo-second-order kinetic model best matched the adsorption and the extraction capacity of thiocyanate anions, 112 mg g−1, exceeds the results reported so far in the literature. In addition, the results showed that the separation of SCN− depends on a synergetic effect of interaction and reduction of SCN− with polyaniline nanotubes/silver nanocomposite.