Sorption of dissolved inorganic and organic phosphorus compounds onto iron-doped ceramic sand

Abstract

Sorption-based processes are widely used in the wastewater treatment. We present results of a study contrasting the sorption behavior of several dissolved organic phosphorus (DOP) compounds and phosphate onto three ceramic sands with different physicochemical properties. The synthesized sorbent materials were characterized by nitrogen adsorption analyses, X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The DOP compounds were chosen to represent different molecular weights and structures. The effects of solution pH, P concentration and contact time on sorption capacity was investigated by kinetic and equilibrium sorption isotherm studies. The order of maximum sorption capacity observed for the three P compounds onto iron-doped ceramic sand samples, on a per gram dry weight basis, is phosphate (DIP)>β-glycerophosphate disodium salt hydrate (β-GP)>adenosine 5′-triphosphate disodium salt hydrate (ATP-P). Langmuir isotherm sorption equation well describes the experimental sorption isotherms. Kinetic studies revealed that the sorption process followed both pseudo-first order and pseudo-second order kinetic models. The iron-doped ceramic sand samples had a higher phosphorus removal capacity than the raw, which could be attributed to its better intra-particle diffusion and higher binding energy. P compound size and structure, and the nature of the sorbents all appear to play a role dictating relative sorption capacity. The sorption process was complex; both surface sorption and intra-particle diffusion were simultaneously occurring and contribute to the sorption mechanism.