Assessment of adsorption properties of inorganic–organic hybrid cyclomatrix type polyphosphazene microspheres for the removal of Pb(II) ions from aqueous solutions

Inorganic-organic hybrid cyclomatrix type polyphosphazene microspheres (poly[cyclotriphosphazene-co-(4,4 '-diaminodiphenylmethane)]) (HDMS) and poly[cyclotetraphosphazene-co-4,4 '-diaminodiphenylmethane)] (ODMS) were prepared to investigate their possible use as alternative adsorbents for the comparative study on Pb(II) ions removal from aqueous solutions. The structures of the microspheres were elucidated by Fourier Transform Infrared (FTIR) spectroscopy and Dynamic Light Scattering (DLS) measurements, and the surface morphologies were also observed by Scanning Electron Microscopy (SEM). The adsorption of Pb(II) ions onto HDMS and ODMS from aqueous solutions was examined by means of pH, temperature, contact time and concentration. Furthermore, adsorption kinetics and isotherm models were applied and the experimental data fitted well with Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacities of HDMS and ODMS for Pb(II) ions were obtained as 157.8 and 308.0 mg g(-1) at 20 degrees C and pH 5.5, respectively.