Efficient removal of organic dyes from aqueous solution by rapid adsorption onto polypyrrole–based composites

Abstract

In order to improve the adsorption capacity of polypyrrole, two inexpensive and renewable biological resources containing abundant functional groups were used to achieve novel polypyrrole-based composites. Three low-cost polypyrrole-based composites, polypyrrole-chitosan-lignosulfonate (PPY-CS-LS), polypyrrole-chitosan (PPY-CS) and polypyrrole-lignosulfonate (PPY-LS) were prepared via an in-situ polymerization of pyrrole monomers with chitosan (CS) and/or lignosulfonate (LS) as dispersants. PPY-CS-LS, PPY-CS and PPY-LS nanoparticles with average diameters of 50 nm, 73 nm and 213 nm, respectively, were obtained with pyrrole/oxidant molar ratio of 1:1, and the contents of CS and/or LS of 10 wt%. Selective adsorption properties of the three composites for six dyes were investigated. Results showed that PPY-CS-LS and PPY-CS composites possessed much higher selectivity for acid (anion) dyes, especially for Congo red (CR); the removal efficiencies of PPY-CS-LS and PPY-CS composites for CR were up to 99.3% and 95.4%, respectively, when the initial concentration of CR was 60 mg L−1 at the adsorption temperature of 30 °C. The adsorption equilibrium time for CR was 30 min, which was more rapid than those of other reported PPY-based adsorbents. The results suggested that the PPY-CS-LS composite exhibited a high adsorption performance for dyes because of the synergistic effects of amino/hydroxyl-containing functional groups from CS, sulfonic groups from LS, and nitrogen-containing functional groups from PPY chains. Furthermore, the adsorption processes were feasible and spontaneous. Therefore, a productive route to fabrication of low-cost PPY–based composite nanoparticles with controllable size and high dye adsorption ability was achieved.