Sequestration of methylene blue (MB) dyes from aqueous solution using polyaniline and polyaniline–nitroprusside composite

Abstract

This paper reports polyaniline–nitroprusside (PANI–NP) composite prepared via in situ polymerization of polyaniline in the presence of sodium nitroprusside complex using ammonium persulphate oxidant. Comparison between the MB dye elimination from aqueous solution using polyaniline and polyaniline–nitroprusside composite is investigated with UV–visible spectroscopy. The maximum adsorption capacity for PANI and PANI–NP composite at 25 °C are 412.80 and 496.85 mg g−1, respectively. About 80% removal of MB occurs in 1 h using pure PANI from (50 mg MB/100 mL) aqueous solution and 99.37% removal is observed in just 5 min, when PANI–NP composite is used. Adsorption kinetics is in good agreement with pseudo-first order for polyaniline and pseudo-second order for polyaniline–nitroprusside composite. The adsorption data fits well with the Langmuir model for both PANI and PANI–NP composite. Langmuir and Tempkin model suggests chemisorption type of interactions between the MB and adsorbents. Thermodynamic study revealed that the adsorption of MB on PANI and PANI–NP composite is exothermic and spontaneous in nature. Moreover, regeneration and reuse of PANI–NP composite as adsorbent is possible only at higher temperature. FTIR studies further confirm the successful adsorption of MB on PANI and PANI–NP composite. On the basis of vey short equilibrium adsorption time and very high adsorption capacity for MB dye, PANI–NP composite could be used as a most efficient adsorbent for the removal of cationic dyes from any real sample.