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

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.