Papers by Keyword: Arsenic

Abstract: Archaeometallurgical copper-artefacts contain a wide variety of metal admixtures (e.g. Pb, Bi, As, Sb, Sn) which either originate from the ores or were intentionally added. When the melt solidifies, these elements can accumulate in different structural areas and form special phases. The different alloying elements also interact with each other. In order to be able to examine these interactions, model alloys with different elements (Pb, Bi, As, Sb, Sn) and concentrations (5 or 10 wt.% each) were produced. More simple alloys show a dendritic microstructure and the added elements accumulate in the interdendritic areas. This is clearly visible for Pb and Bi additions, as both metals are not soluble in copper. As and Sb form compounds with Cu which precipitate mainly in the interdendritic regions. Sn is soluble in Cu at lower concentrations and Cu-Sn phases are formed only at higher concentrations. The resulting microstructures become very complex if more elements are involved. Finally, they enable us to have a better understanding for microstructures of ancient copper alloys.

Abstract: The former regional municipal solid waste landfill owned by the Local Government of Dunaújváros; Hungary located next to village Kisapostag. The first part of the recultivation of this territory was begun in 2010 and was finished in 2012. In this case study, ten-year changes in concentrations of some groundwater pollutants such as ammonia, nitrate, nitrite and some heavy metals such as arsenic and nickel are presented. The recultivated municipal solid waste landfill is covered with a temporary top closing layer, on the top are plants, mainly grass according to 20/2006. (IV. 5.) KvVM decree on landfill and certain rules and conditions related to landfill [4]. The environmental protection authority obliged the municipality to build the final waterproofing top layer at the landfill by June 30, 2025. In our opinion, this is completely unnecessary, as the temporary barrier layer fully fulfils its function. The landfill is far from populated areas and has not caused any environmental pollution or damage. The construction of the final upper waterproofing layer would cause extremely high costs for the local government.

Abstract: Magnetic biochar derived from various residual agricultural wastes have been widely studied due to their abundance, low cost, and minimal environmental impact. Pecan nutshell (Carya illinoinensis) residuals were incorporated with γ-Fe₂O₃, transforming them into magnetic adsorbents. The effect of particle size (granular: 0.38-0.7 mm; powder: 0.15-0.38 mm) and pyrolysis temperature (500 °C and 650 °C) were investigated for their influence on adsorption capacity of arsenic and fluoride in aqueous solutions. Our findings showed that finely powdered magnetic biochar produced at 650 °C (PMPH-650) exhibited the highest removal efficiency (99.09%) and adsorption capacity (4.925 mg/g) for arsenic compared to other materials. The arsenic adsorption isotherm followed both Langmuir and Freundlich models well. The kinetics of fluoride adsorption fit the Elovich equation, suggesting chemisorption and chemical bond formation. XRD and FTIR analyses confirmed the presence of the γ-Fe₂O₃ phase. SEM/EDX and FTIR analyses confirmed the presence of arsenic on the biochar surface after the adsorption. This research paves the way for using magnetic biochar derived from pecan nutshell as a cost-effective and eco-friendly approach for arsenic and fluoride remediation in water.

Abstract: The extraction and processing of silver minerals produce significant amounts of waste, which poses environmental challenges due to their low metal content and the potential release of toxic elements. The study investigates the application of Acidithiobacillus ferrooxidans (AF) bacteria to the bioleaching of these waste materials, with the aim of maximizing the recovery of iron, copper and arsenic. The objectives of the study include characterizing waste materials, optimizing the bioleaching process parameters and evaluating metal extraction efficiency. The samples were leached with additives (CuSO₄ 5H₂O and AgNO₃) to accelerate the kinetics of metal dissolution in solution and reduce the bacterial leaching time. The results showed that samples 1-2 and 2-2 containing additives had higher values of dissolved iron and copper in the leachate compared to samples 1-1 and 2-1 without additive application.

Abstract: Here we provide a description of arsenic (As) adsorption on the cellulose biopolymer using first-principles density functional theory. In all studied configurations, the process of As adsorption on the cellulose is an exothermic process indicated by the negative binding energy. The cellulose's hydroxyl and hydroxymethyl groups significantly interact with As atom, characterized by the binding energy. In all optimized configurations, the interactions are mainly described as chemical bonding. This claim is supported by the overlap of the electron localization function (ELF) in the interface of As and cellulose in all studied adsorption sites. The adsorption of As on the cellulose introduces new states in the vicinity of the Fermi energy, leading to the lower bandgap of the cellulose-As systems. Overall, these results imply that the As atom can be trapped and detected using cellulose-based material. These findings offer an explanation of earlier research works on cellulose-As systems. This work will also serve as a reference for fabricating cellulose-based material for sensing and removing As.

Abstract: As_xSe_1-x glasses with x from 0,05 to 0,55 were prepared at two melting temperatures, 700 and 850 °C. Batch materials from several suppliers were used for glass synthesis. Density and IR transmittance of glasses were measured. It was found that data for density of glasses prepared at 700 °C have sufficient scatter, so dependence of molar volume on composition is not smooth. Data for glasses synthesized at 850 °C are in good agreement with reference ones. According to data of IR spectroscopy the main impurity in glasses is oxygen in several molecular forms. Oxygen gets in glass together with arsenic. Its content can be noticeably decreased by the heat treatment of As at from 300 to 350 °C and Se at 310 °C before weighting and by the heat treatment of batch at 200 °C before the sealing of silica ampoule. Optical quality of glass samples is good enough for the use them as IR transparent material for lens manufacturing.

Abstract: This article describes thermodynamic study of hydrometallurgical method for processing of copper arsenious gold-containing raw material. Chemical and phase composition of the material were researched. Calculations of the Gibbs energy change were conducted for possible reactions of the main minerals, present in the raw material, with nitric acid. Eh-pH diagrams and solid/liquid equilibrium distribution diagrams, which were constructed in order to confirm the possibility of obtaining the required reaction products through nitric acid leaching of the studied raw material.

Abstract: Diatomite or diatomaceous earth (DE) is one of materials which can be used as an adsorbent to treat heavy metal ions from waste water, even there are many factories used it to clean the water for drinking. However, natural DE (raw DE) has very low adsorption capacity because of low specific surface area. In this work, natural DE from Lam Dong province, Viet Nam was demagnetized to remove iron and activated by HCl solution for 90 minutes with concentration of 10% at room condition. Adsorbent capacity was evaluated using As solution and the results show that the activated diatomite has adsorption capacity three times higher than that of raw DE, and the specific surface area of activated diatomite was increased 47.5% with the main chemical composition of 90.8% SiO₂ and high porosity

Abstract: Currently, the share of gold extracted from technologically simple gold ores is steadily decreasing, which determines the involvement in the processing of refractory gold ores containing finely disseminated gold and silver in sulfides, mainly in pyrites and arsenopyrites. Autoclave oxidation is a promising method of pretreatment of the refractory sulfide-arsenic gold-bearing raw materials before cyanidation. A serious problem of auriferous ores autoclave-hydrometallurgical processing is the removal of contained arsenic into relatively harmless and capable of being kept forms. This article shows the results of behavior of arsenic during the neutralization of solid after autoclave oxidative leaching of refractory gold-containing materials.

Abstract: Tank bioleaching of substandard arsenic-bearing sulfide copper–zinc concentrate, containing 1.70, 6.22, and 7.30% of arsenic, copper, and zinc, was performed. The concentrate contained pyrite, chalcopyrite, tennantite, and sphalerite. Bioleaching was performed at 40°C using a mixed culture of acidophilic microorganisms in two modes. In the first mode, pulp density was 10%, while in the second it comprised 15%. Bioleaching made it possible to extract 17 and 70% of copper and zinc in the first mode, and 15 and 72% of copper and zinc in the second mode. The results obtained that bioleaching can be an effective approach to remove zinc from substandard copper-zinc concentrates. At the same time, copper minerals, including arsenic-bearing mineral tennantite, may be comparatively resistant to bioleaching, so requires the development of novel hydrometallurgical approaches for effective processing.