Application of polyaniline/activated carbon nanocomposites derived from different agriculture wastes for the removal of Pb(II) from aqueous media

Polyaniline/agricultural waste activated carbon (PANI/AC) composites were prepared by chemical oxidative polymerization of aniline monomer with activated carbon obtained from different sources of agricultural wastes present in the environment. The prepared PANI/AC composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller surface area for the removal of lead ions by polyaniline/activated carbon nanocomposites. The thermal stability of the different composites was determined by thermogravimetric analysis. As well as, the electrical conductivity was measured for the prepared composites. The effect of different pH and the adsorbent dose of the composites on the removal of the lead ion from aqueous solution was studied. Results showed that the adsorption maximum occurs at around pH 4.0; adsorption equilibrium was achieved in 90 min at 20 mg L-1 Pb(II) concentration and adsorbent dose 1 g/100 mL for each composite. Removal of Pb(II) ions increases with increasing solution pH and pH maximum value was at pH 4 for all the composites. By comparing the removal efficiency between polyaniline, polyaniline/orange peels activated carbon, polyaniline/peach stones activated carbon, polyaniline/banana peels activated carbon, polyaniline/apricot stones activated carbon and polyaniline/pomegranate peels activated carbon for the removal of lead ions, the removal efficiency of polyaniline/orange peels activated carbon nano-composite is higher than the other composites. The maximum adsorption capacity of PANI/OPAC nanocomposite was 6.81 mg g(-1). The thermal stability and the electrical conductivity of the composites were enhanced with different agricultural sources of activated carbon. The experimental equilibrium biosorption data were analyzed by Freundlich and Langmuir isotherm models. The Freundlich isotherm provided a better fit than Langmuir isotherm. The results indicated that the adsorption of Pb(II) by PANI/OPAC follows pseudo-second-order kinetic model. The thermodynamics indicated that the process is endothermic and spontaneous. Desorption experiments were carried out by different desorbing agents such as distilled water, EDTA and HCl. They found that the desorption using 0.1 M HCl is the most effective desorbing agent.