Mechanistic evaluation of the sorption properties of endocrine disrupting chemicals in sewage sludge biomass

ABSTRACT

This study investigated the sorption behaviour of two endocrine disrupting chemicals; 17b-estradiol [E2] and 17b-ethinylestradiol and their thermodynamic properties in an activated sludge biomass. The partition coefficient values measured for E2 and EE2 at varying temperatures range from 245 - 604 L/kg [log Kd 2.39 -2.78] and 267 - 631 L/kg [Log Kd 2.43 - 2.80], respectively. The Kd values were inversely related to temperature. The average percentages of E2 and EE2 adsorbed to the solid phase at 4.3% dry solid were 87.2% and 92.5%, respectively. Sorption of E2 and EE2 to the activated sludge biomass was found to be spontaneous and entropy retarded with DG values in the range of -13 to -16 KJ/mol and DS value of -105.2J/mol/K and 96.7 J/mol/k for E2 and EE2, respectively. The enthalpy changes for E2 and EE2 were - 45.7KJ/mol and - 43.4KJ/mol respectively, demonstrating that the sorption process is exothermic. The values of the enthalpy changes also show that the mechanism of sorption is physisorption with some element of chemisorption