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To increase the degree of cobalt (Co) extraction, the process of the cathode material leaching was performed in a sulfuric acid (H2SO4) solution containing sulfur dioxide (SO2) as a reducing agent. To provide a high resolution of the obtained results, frequent monitoring of Co concentrations in leached solution was conducted using an ultraviolet–visible spectrophotometer with several specific modifications related to the connection of the reaction vessel with the instrumental cuvette. The maximum degree of Co leaching (99.4%) was achieved with H2SO4 concentration of 3 mol/L, solid phase concentration of 33 g/L, temperature of 85 °C, SO2 volume flow of 2 L/min, and leaching time of 60 min. The results of the performed kinetic analyses indicated that the Avrami equation best describes the investigated leaching process, which later was supported by the results of X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy analyses. Also, the activation energy of 28 ± 3 kJ/mol is in favor of the fact that the process of Co leaching was controlled by the factors, such as diffusion and chemical reaction. The results of this study indicated that SO2 can be used as an effective reducing agent in the investigated process. [ABSTRACT FROM AUTHOR]

This study evaluates bioaccumulation and translocation potentials of trace elements (TEs) by Saponaria officinalis L. (soapwort) and Achillea millefolium L. (yarrow) in order to select and optimize phytoremediation methods for the polluted environment of the city of Bor, Serbia. According to the enrichment factor for soil (i.e., 57.9–128.8 for Cd and As), pollution index (i.e., 6.6–84.7 for Cu), pollution load index (2.9–98.8), individual potential risk factors (11.5–5163), and potential ecological risk index values (260–6379), urban and rural soils from the city of Bor were classified as very contaminated with the investigated TEs. The results from all the indices and statistical analysis showed significant ecological risks of Cu, As, and Cd at the investigated sites and urge the need for remediation. The enrichment factor of the plants for As (566.3) and Cd (306.2) indicated a high enrichment level of the herb organs at all the sites. Since there are small differences in metal accumulation index values between the herbs and their parts (root, shoot), soapwort and yarrow can be considered as potential bioindicators. Based on the biological concentration and translocation factors, soapwort can be recommended as a suitable herb for phytoextraction purposes of Pb, As, and Cd polluted areas. Yarrow shows good characteristics for phytoextraction of Cu, Pb, and As from the contaminated soil. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) results indicate their similar origin from atmospheric deposition. Therefore, these herbs can be utilized as a bioindicator and phytoremediator in polluted areas influenced by metallurgical activities to detect possible levels of TEs. [ABSTRACT FROM AUTHOR]

Periods with rainfall and rapid snow melting or their simultaneous occurrence are very important for good water quality. Such periods lead to a rapid increase in turbidity as well as the natural organic matter quantity in water. Chlorine as a disinfectant builds the toxic disinfection by-products with the natural organic matter that are harmful to human health. Data monitoring allows the prediction of deterioration of the water quality at the source depending on the climatic parameters. Water supply sources in the catchment area of the Beljevina River, operated by the Bor Water Utility, are an example of well-thought-out monitoring of water quality and quantity, which is a major contributor to the superior public water supply. Given the fundamental role played by turbidity and the lack of studies concerning its magnitude at karst groundwater, the current study has introduced an assessment of this parameter. Consequently, the system of turbidity control is necessary, especially if there is no system to remove turbidity from raw water. Data presented in this paper are a result of the monitoring of the Zlot water supply source used as the supply and distribution system in the City of Bor. The results indicate that the effect of air temperature had a dominant impact on snowmelt, turbidity and water level in the Beljevina River after 2 days. Also, the results showed a significant positive correlation between turbidity and potassium permanganate consumption. Monitoring data of these parameters over a long period will allow the establishment of a simulation model for short-term prediction of turbidity or any other water quality parameters. [ABSTRACT FROM AUTHOR]

This investigation aimed to study a “green” non-toxic biodegradable copper corrosion inhibitor in an acidic sodium sulphate solution. The methods used in the investigation of cysteine as a copper corrosion inhibitor in an acidic sodium sulphate solution were: potentiodynamic measurements, open circuit potential measurements, and chronoamperometric measurements. Optical microscopy was used in addition to electrochemical methods. Potentiodynamic measurements show that cysteine has good inhibitory properties in an acidic medium. Polarisation curves indicate that the presence of cysteine in a sulphate solution decreases the current density and that using various cysteine concentrations results in the formation of a protective film on the surface of the electrode due to the formation of the Cu(I)-cys complex. These results are confirmed by chronoamperometric measurements. Furthermore, it is clear from microphotographs that a protective film does form on copper electrode in the presence of cysteine. The Langmuir adsorption isotherm indicates that cysteine is chemisorbed on the surface of the electrode. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate electrochemical properties of brass in neutral and weakly alkaline solutions in the presence of cysteine as a nontoxic and ecological corrosion inhibitor. Potentiodynamic measurements, open circuit potential measurements, as well as chronoamperometric measurements were the methods used during investigation of the inhibitory effect of cysteine on the corrosion behaviour of brass. Potentiodynamic measurements showed that cysteine behaves as a mixed-type inhibitor in the investigated media. Based on polarization curves for brass in a weakly alkaline solution of sodium sulphate at varying cysteine concentrations, an interaction occurs between Cu ions and the inhibitor, resulting in the formation of a protective complex on the electrode surface. The results of chronoamperometric measurements confirm the results obtained by potentiodynamic measurements. Optical microphotography of the brass surface also confirms the formation of a protective film in the presence of a 1 × 10 mol/dm cysteine. Adsorption of cysteine on the brass surface proceeds according to the Langmuir adsorption isotherm. [ABSTRACT FROM AUTHOR]

The effect of purine (concentration range of 1.00 × 10-1.00 × 10 M) on the behavior of copper in a 0.5 M NaSO solution (pH 7 and pH 9) was studied using the open circuit potential measurement, potentiodynamic polarization, and chronoamperometry. Potentiodynamic polarization shows that purine acts as a copper corrosion inhibitor in both alkaline and neutral sulfate solutions. The efficiency of inhibition increases as the purine concentration increases. Chronoamperometric results follow the same trend as the results of potentiodynamic polarization. The inhibition effect can also be observed visually by microscopic examination of the electrode surface. Purine is adsorbed on copper surface according to the Langmuir adsorption isotherm. [ABSTRACT FROM AUTHOR]