Natural sorbents modified by divalent Cu2+- and Zn2+- ions and their corresponding antimicrobial activity

• Published in: New biotechnology Vol. 39; pp. 150 - 159
• Main Authors: Đolić, Maja B., Rajaković-Ognjanović, Vladana N., Štrbac, Svetlana B., Dimitrijević, Suzana I., Mitrić, Miodrag N., Onjia, Antonije E., Rajaković, Ljubinka V.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.10.2017
• Subjects: Activated sorbent; Antimicrobial activity; C. albicans; E. coli; S. aureus; Activated sorbent; Antimicrobial activity; S. aureus; C. albicans; E. coli
• ISSN: 1871-6784; 1876-4347
• DOI: 10.1016/j.nbt.2017.03.001

•Granulated activated carbon (GAC) and natural clinoptilolite (CLI) were activated by Cu2+- and Zn2+-ions and tested against E. coli, S. aureus and C. albicans.•The most successful bacteria removal was obtained using Cu/CLI and Cu/GAC against E. coli, while S. aureus and yeast cell inactivation yielded unsatisfactory results for all activated sorbents.•XRD and XPS analysis showed that the antimicrobial efficacy of metal-activated sorbents relates to the surface characteristics of the material.•The disinfection property of sorbents modified by metal ions is determined by their influence on an activated surface (the metal ions immobilized on the surface of the material). The objective of this study was to investigate the modification of materials used in wastewater treatment for possible antimicrobial application(s). Granulated activated carbon (GAC) and natural clinoptilolite (CLI) were activated using Cu2+- and Zn2+- ions and the disinfection ability of the resulting materials was tested. Studies of the sorption and desorption kinetics were performed in order to determine and clarify the antimicrobial activity of the metal-activated sorbents. The exact sorption capacities of the selected sorbents, GAC and CLI, activated through use of Cu2+- ions, were 15.90 and 3.60mg/g, respectively, while for the materials activated by Zn2+- ions, the corresponding capacities were 14.00 and 4.72mg/g,. The desorption rates were 2 and 3 orders of magnitude lower than their sorption efficacy for the Cu2+-, and Zn2+-activated sorbents, respectively. The intermediate sorption capacity and low desorption rate indicated that the overall antimicrobial activity of the metal-modified sorbents was a result of metal ions immobilized onto surface sites. The effect of antimicrobial activity of free ions desorbed from the metal-activated surface may thus be disregarded. The antimicrobial activities of Cu/GAC, Zn/GAC, Cu/CLI and Zn/CLI were also tested against Escherichia coli, Staphylococcus aureus, and Candida albicans. After 15min exposure, the highest levels of cell inactivation were obtained through the Cu/CLI and the Cu/GAC against E. coli, 100.0 and 98.24%, respectively. However, for S. aureus and yeast cell inactivation, all Cu2+- and Zn2+-activated sorbents proved to be unsatisfactory. A characterization of the sorbents was performed by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM). A concentration of the adsorbed and released ions was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS). The results showed that the antimicrobial performance of the activated sorbents depended on the surface characteristics of the material, which itself designates the distribution and the bioavailability of the activating agent.