ABSTRACT
The impact of different concentrations of three amino acids (cysteine, histidine and methionine) which are part of the amino acid sequence of rusticyanin on dissolution of pyrite is investigated by the application of electrochemical techniques. Cyclic voltammetric studies conducted in the anodic direction from corrosion potential have shown that in the vicinity of corrosion potential, histidine and methionine do not influence dissolution of pyrite independently on their concentrations. On the other hand, cysteine and solutions of these amino acids in the molar ratios Cys:His:Met/1:1:1 and Cys:His:Met/1:2:1 accelerate dissolution at concentrations 10-2â¯molâ¯L-1 and 10-3â¯molâ¯L-1. Potentiodynamic polarization measurements showed that methionine does not affect the anodic and cathodic dissolution at all concentrations, while histidine does not affect significantly on the anodic dissolution at all concentrations. Cysteine and solutions of three amino acids in the molar ratio Cys:His:Met/1:1:1 and Cys:His:Met/1:2:1 cause intensive cathodic inhibition and anodic activation at concentrations 10-2â¯molâ¯L-1 and 10-3â¯molâ¯L-1 respectively.
Subject(s)
Azurin/chemistry , Iron/chemistry , Sulfides/chemistry , Sulfuric Acids/chemistry , Cysteine/chemistry , Electrochemical Techniques , Electrodes , Histidine/chemistry , Methionine/chemistry , Models, Molecular , SolubilityABSTRACT
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.
