ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Sludge of wastewater treatment plants as Co²⁺ ions sorbent

Vladimír Frišták, Martin Pipiška, Miroslav Horník, Jozef Augustín, and Juraj Lesný

Department of Ecochemistry and Radioecology, University of Ss. Cyril and Methodius in Trnava, Nám. J. Herdu 2, 917 01, Trnava, Slovakia

E-mail: fristak.vladimir.jr@gmail.com

Abstract: Sludges produced in huge amounts by wastewater treatment plants (WWTP) display high fertility properties; however, the presence of heavy metals restricts their use for agricultural purposes. Sorption capacity of sludge is generally much higher and it can also be considered as a cheap sorbent of heavy metals. The paper describes cobalt sorption by dried activated sludge (DAS) obtained from the aerobic phase of a WWTP. DAS was characterized by FT-IR spectroscopy, cation exchange capacity (CEC), and atomic absorption spectrometry (AAS) analysis. Sorption capacity of DAS (Q _eq) increased with the initial concentration (C ₀) of Co²⁺ (CoCl₂) within the range from 100 μmol g⁻¹ to 4000 μmol g⁻¹, reaching 15 μmol g⁻¹ and 200 μmol g⁻¹, respectively. The maximum uptake capacity (Q _max) at pH 6.0 calculated from the Langmuir isotherm model was (256 ± 9) μmol g⁻¹ for Co²⁺ ions. Obtained Q values were dependent on pH within the range from 3.0 to 7.0. Competitive effect of other bivalent cations such as Ni²⁺ in Co²⁺ sorption equilibrium was confirmed; which is in agreement with the hypothesis of the decisive role of ion-exchange mechanism in metal sorption. The obtained data are discussed from the point of view of potential utilization of sludges as sorbents, i.e. in non-agricultural application.

Keywords: activated sludge – sorption – cobalt – chemical modification – cation exchange capacity

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-012-0244-1

Chemical Papers 67 (3) 265–273 (2013)