Sludge from a Water Treatment Plant as an Adsorbent of Endocrine Disruptors

Abstract

Water Treatment Sludge (WTS) is a solid residue generated in large volumes. The use of WTS in adsorption processes is still little addressed, but it has shown promising results. This material (in raw or modified form) was never evaluated for endocrine disruptors removal. Thus, the novel of this work is to evaluate the removal of E2 and EE2 using adsorbents manufactured from WTS. The WTS underwent heat treatment and was chemically activated with phosphoric acid or potassium hydroxide - giving rise to PMS, PAS, and PHS adsorbent material, respectively. The solids were characterized by TGA, ASAP, SEM, FTIR, XRD, XRF, and pH-PZC. The adsorption process was evaluated regarding the dosage, kinetic, and isotherms. The modifications imposed to WTS were effective, increasing 1.6 times the surface area and pore volume; the adsorbents presented silica, quartz, and kaolinite on their compositions; and a pH-PZC around 6. Using only 0.5 g of adsorbent it was possible to reach an adsorption capacity of 6.14 μg.g -1 for E2 and 7.15 μg.g -1 for EE2. The equilibrium time and fits to kinetic models varied in function of the adsorbate concentration. Similar fits to Langmuir and Freundlich isotherm models were obtained. With the results obtained it was shown the effective adsorption of E2 and EE2 on PMS, PAS, and PHS. Thus, it gives a possible application for WTS residues and an alternative for E2 and EE2 removal from aqueous solution.

Keywords: Adsorption, Emerging contaminants, Wastewater Treatment, hormones