The modified polythiophene-Cu NPs composites for Pb(II) ions removal from aqueous solution

The present work describes the use of chemically modified polythiophene with copper nanoparticles and polyvinylpyrolidine-sulfonic acid (PTh-PVP-SA-Cu) as an adsorbent for the removal of Pb(II) ions from aqueous solution. The synthesized composite, PTh-PVP-SACu, was characterized by different techniques including Fourier-transform infrared spectrometer, scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy, X-ray powder diffraction, thermogravimetric analysis (TGA), and differential scanning calorimetry. This nanocomposite has good conductivity and thermal stability due to the presence of copper nanoparticles. The acidic doping agent, polyvinylpyrolidine-sulfonic acid, can act as the surfactant and improves the polymerization of thiophene in the aqueous medium. The conductivity of PTh was 0.54 S/cm, while the conductivities of PTh-Cu with 10 and 20 wt% of PVP-SA under the same reaction conditions were 2.3 and 2.7 S/cm, respectively. The influence of pH, adsorbent dosage, temperature, contact time, and concentration on the removal of Pb(II) ions was evaluated. The optimum conditions for the removal of Pb(II) ions were 25 degrees C with the adsorbent dosage of 3 g.L-1 at pH = 7. The adsorption capacity was obtained to be 111 mg. g(-1). The obtained equilibrium data for PTh-PVP-SA-Cu was fitted well by Langmuir isotherm model indicating that the adsorption process was monolayer adsorption and distribution of adsorption sites on the surface of PTh-PVP-SA-Cu was homogeneous. The maximum monolayer capacity obtained from the Langmuir isotherm was 121.9 mg. g(-1) for Pb(II) ions at 45 degrees C. The values of Gibbs free energy (Delta G), entropy change (Delta S) and enthalpy change (Delta H) indicated the feasibility, spontaneity and the endothermic nature of the adsorption process, respectively. The kinetic process followed the pseudo-second-order kinetic model. The recyclability studies revealed that PTh-PVP-SA-Cu could be reused for three consecutive cycles.

Automated summary

This study utilized PTh-PVP-SA-Cu composite adsorbent for successful removal of Pb(II) ions from aqueous solution. Characterization confirmed the nanocomposite's good conductivity, thermal stability, and homogeneous distribution of adsorption sites, fitting well with the Langmuir isotherm model. Kinetics followed the pseudo-second-order model, and recyclability was demonstrated through three consecutive cycles of reuse for PTh-PVP-SA-Cu.