Electrical properties and heavy ions removal ability of graphitic carbon nitride/polypyrrole composite

Abstract

A composite of graphitic carbon nitride (g-C3N4) and polypyrrole (PPy) is synthesized in a ratio of 1:1 by in situ oxidation polymerization technique as a novel heavy-ions removal composite. The structure of the prepared material compared with g-C3N4 pure is characterized using FTIR and XRD. Investigation of electric and dielectric properties of the composite using Broadband dielectric spectroscopy technique is carried out to explore the conductivity change and charge carriers' density of the composite. The results showed that the electrical conductivity of the composite is unexpectedly nearly the same as that of pure PPy despite having such a high ratio of g-C3N4. Moreover, a significant increase in the density of charge carriers is realized and considered the origin of conductivity enhancement. Adsorption of Pb (II) and Cd (II) from their solution is performed under different conditions of pH, time, ions concentration, and temperature. The results confirmed increasing in ions uptake in case of using composite compared with pure (g-C3N4) owing to the increase in the density of charge carriers. Determination of the kinetics of g-C3N4 and g-C3N4/PPy to understand their adsorption property is carried out using various kinetic models namely, Pseudo-first order (PFORE), pseudo-second order (PSORE) and Elovich, to fit the experimental data. The obtained data showed that pseudo-second-order kinetic model is the best model for the adsorption process and chemisorption might be the rate-determining step. Regeneration efficiencies of g-C3N4 and g-C3N4/PPy were found to be 95% and 98% respectively. The results demonstrated that presence of PPy not only increased ions uptake from wastewater but also enhanced the workability and efficiency for three repeated cycles of sorption–desorption.