Highly efficient adsorbents of poly( o-phenylenediamine) solid and hollow sub-microspheres towards lead ions: A comparative study

Abstract

Two kinds of different-shaped poly( o-phenylenediamine) (P oPD) polymers: solid and hollow sub-microspheres with both size of about 700 nm synthesized by a solution route without any additional directing agents, were employed as efficient adsorbents for removal of Pb(ІІ) ions from water. Firstly, chemical structures of P oPD sub-microspheres were performed by Fourier-transform infrared (FT-IR), UV–vis, 1H NMR spectra, X-ray diffraction (XRD) and GPC analysis. When used as adsorbents, both P oPD hollow and solid sub-microspheres showed high adsorptivity and adsorption capacity towards Pb(ІІ) ions in water, and mechanisms of adsorption behaviors were revealed by XRD and X-ray photoelectron spectra (XPS). It was found that the pH and concentration of Pb(ІІ) ion solution, as well as contact time and adsorbent dosage affect the degree of adsorption. Adsorption isotherms and kinetics of Pb(ІІ) ions onto P oPD sub-microspheres were also investigated according to experimental data. Comparative investigations of adsorption behaviors revealed that hollow sub-microspheres showed enhanced adsorptivity adsorption capacity towards Pb(ІІ) ions as compared with solid sub-microspheres typical at low adsorbent dosage. P oPD hollow sub-microspheres also showed good adsorptivity for other heavy-metal ions, such as Hg(ІІ), Cd(ІІ) and Cu(ІІ), which implied their potential applications as effective adsorbents for heavy-metal ions in water.