Chromogenic polyaniline picrate- A novel sorbent for selectivity of anions in potassium and sodium salts

Abstract

A novel chromogenic, polymeric sorbent material Polyaniline picrate (PANIPI) has been synthesized by chemical oxidative polymerization and characterized using various spectral techniques. Cyclic voltammetry and four probe conductivity measurements have revealed that the polymer is highly electroactive. Surface morphology is analyzed using SEM and TEM micrographs. Potassium halides, potassium sulphate and potassium thiocyanate are used as sorbate materials for ion exchange on PANIPI. Five types of sorption isotherms namely Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Redlich-Peterson are applied to the sorption process. Among these isotherms Langmuir, Freundlich and Temkin models fitted well for the sorption of potassium salts on PANIPI. The maximum adsorption capacity (q_m) follows the size order of anions. The intensity of FT-IR stretching vibration for SCN^- at 2066 cm^-1 varies linearly with concentration, making PANIPI an effective sensor material for the quantitative determination of SCN^-. The potassium to sodium selectivity of 2:1 is observed at both low and high sorbate concentrations.