Facile synthesis of a polythiophene/TiO2 particle composite in aqueous medium and its adsorption performance for Pb(II)

A polythiophene/TiO2 (PTh/TiO2) particle composite was synthesized by a facile and green method via (NH4)(2)S2O8-catalyzed oxidative polymerization of thiophene in acidic aqueous medium to adsorb Pb2+ ions from aqueous solution, and the synthesis mechanism was proposed. The particle composite was carefully characterized by Fourier transform infrared spectroscopy (FTIR), Xray diffraction (XRD), thermogravimetric (TG) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and zeta potential analysis, and it showed that the composite prepared had a high specific surface area of 229.66 m(2) g(-1). Various factors such as adsorbent dosage and solution pH influencing the adsorption were investigated. The isotherm results indicated that the adsorption performance of Pb2+ on the composite fitted the Langmuir model, and the maximum adsorption capacity reached 151.52 mg g(-1) at 25 degrees C, 170.36 mg g(-1) at 35 degrees C and 173.61 mg g(-1) at 45 degrees C. The present adsorption system can be described most favorably by a pseudosecondorder model, confirming that chemisorption such as chelation may be the adsorption rate-limiting step. Meanwhile, adsorption was a spontaneous and endothermic process with increased entropy. In addition, regeneration by HCl-elution and NaOH-activation was possible, and the composite could be used repeatedly without any significant reduction in its adsorption capacity after 6 adsorption-desorption cycles. Furthermore, the adsorption mechanisms were investigated.