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; 17β-estradiol (E2) and 17β-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 K d 2.39–2.78) and 267–631 L/kg (Log K d 2.43–2.80), respectively. The K d 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 ΔG values in the range of −13 to −16 KJ/mol and ΔS 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.