Removal of Chromium(VI) from Aqueous Solutions Using Polyaniline Doped with Sulfuric Acid

A type of polyaniline was synthesized and its Cr (VI) removal potential was investigated in this work. The kinetics study, adsorption isotherm, pH effect, and thermodynamic study were examined in batch experiments. Adsorption data for Cr (VI) uptake by polyaniline were analyzed according to Langmuir and Freundlich adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K, and 313 K (ΔH° = 23.87 kJ mol−1; ΔG° = −10.76 to −13.13 kJ mol−1 and ΔS° = 118.20 J K−1 mol−1). The positive values of both ΔH° and ΔS° suggest an endothermic reaction, increasing in randomness at the solid−liquid interface during the adsorption process. ΔG° values obtained were negative, indicated that the adsorption of the Cr (VI) ion on the surface of polyaniline was a spontaneous adsorption process. The kinetics process can be described by a pseudosecond-order rate equation very well. The Cr (VI) adsorption capacity tended to increase with a decrease of pH. The maximum uptake of Cr (VI) was 95.79 mg g−1. These results show that the polyaniline doped with sulfuric acid could be considered as a potential adsorbent for chromium hexavalent ions in aqueous solutions.