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The presented article deals with the thermodynamic study of copper converter flue dust (CCFD) treatment by hydrometallurgical process. The investigated sample of CCFD contains 38.31 wt.% Zn, 11.35 wt.% Pb, and 2.92 wt.% Sn in the form of oxides (PbO, ZnO, and SnO2). The leaching of CCFD in sulphuric acid, acetic acid, nitric acid, and sodium hydroxide was thermodynamically studied. Using Pourbaix diagrams for individual metal–S/C/N/Na/–H2O systems, the possibility of leaching oxides in selected leaching agents was confirmed. A sustainable and environmentally friendly method of processing the sample of CCFD using a hydrometallurgical method is proposed. A suitable selective leaching agent is the acetic acid solution. When leaching in an acetic acid solution, zinc and lead are chemically dissolved to form acetates Zn(CH3COO)2(aq) in the form of Zn2+(aq) at a temperature of 20 °C with a pH range of 0–3.5 and at a temperature of 80 °C with a pH range of 0–2.95, as well as Pb(CH3COO)2(aq) as Pb2+(aq) at a temperature of 20 °C with a pH range of 0–1.95 and at a temperature of 80 °C with a pH range of 0–2, respectively, while tin remains as a solid residue in the form of SnO2(s) at the temperatures of 20 °C and 80 °C throughout the whole acidic pH range. Various analytical techniques, such as SEM, EDX, XRD, and AAS, were used to analyse samples before a thermodynamic study of the leaching of CCFD was conducted by applying Pourbaix Eh–pH diagrams. [ABSTRACT FROM AUTHOR]

In Slovakia, around 200 environmental burdens that contain a significant amount of usable raw materials were created by the extraction of ores or the dumping of industrial waste. In this research, the hydrometallurgical metal recovery method from a metal-bearing environmental landfill in Sereď was investigated. The analysis of a representative sample of waste obtained from this landfill proved the presence of significant amounts of metals (43.45% Fe; 1.3% Cr; 0.09% Co, and 0.23% Ni). A thermodynamic study of the metals' (Fe, Cr, Ni, and Co) leaching probability confirmed the possibility of metal extraction in an acidic environment. Subsequently, the effect of the most important factors on the leaching process (stirring intensity, temperature, liquid-to-solid phase ratio, and acid concentration) was experimentally tested. The analysis of the results determined the optimal leaching conditions. The extraction of 90.35% Fe and 59.62% Cr was ensured at a stirring intensity of 400 rpm, a leaching temperature of 80 °C, a liquid-to-solid phase ratio of 40, and a H2SO4 concentration of 3 mol/dm3. Various techniques, including SEM, EDX, XRD, Eh-pH diagrams, and AAS analysis, were used to analyze samples and products after leaching. The possibility of precipitating metals/compounds from the leachate to obtain a marketable product was theoretically proposed and proven. [ABSTRACT FROM AUTHOR]

This article will focus on the alkaline leaching of gold-bearing tetrahedrite concentrate in a solution containing sodium sulfide and sodium hydroxide. This selective leaching is followed by the leaching of heavy and waste metals into the solution, which may influence the physical properties and quality of the desired product, possibly causing environmental toxicity. At the same time, the amount of gold was observed during the leaching process to increase its content in the solid phase for the possibility of recovery and subsequent extraction of the precious metal. Sodium sulfide works very effectively on sulfide minerals which include tetrahedrite, and sodium hydroxide eliminates the hydrolysis of sulfur which slows leaching. The leaching kinetics were carried out with a duration of five hours, and based on volume sampling at certain time intervals from three samples, with the characteristic NaOH concentration, the leaching efficiency was observed from the results with atomic absorption spectrometry. The solid residue containing the tetrahedrite concentrate was analyzed through X-ray photoelectron analysis spectrometry, from which the % solids content was determined, and it is also known to deduce the leached amount of metals for each sample. [ABSTRACT FROM AUTHOR]

The utilization of fly ashes in Slovakia is lower than in other countries and dumping of fly ashes prevails. The dumping changeschemical and phase composition of fly ashes and so it decreases possibilities for their utilization. Fly ashes are mainly used in buildingindustry, where the content of loss on ignition (LOI) is limited due to standards. Black coal fly ashes produced in Slovakia have a highcontent of loss on ignition – more than 20 % - so they straight utilization in building industry is not possible. The current possibility fortheir utilization is in geopolymer synthesis. Products with 28-day compression strength of 35.7 MPa and 180-day compression strengthof 55.0 MPa were obtained by alkali activation of fly ashes with 23.25 % LOI with 8 wt% Na2O and their next hardening in temperatureof 80 °C during 6 hours. Products have a great frost-resistance and aggressive environments resistance (NaCl a H2SO4 solutions).

Flotation of plastics becomes a very prospective method of their separation as a reflection of the industrial quality of purity requirements. The problem is however that most of the plastics have relatively similar hydrophobic surfaces preventing them to be selectively sorted by the flotation method. That is why various ways have been proposed in order to stimulate the wetting of the plastics´ surfaces selectively (gamma flotation, selective adsorption of wettting substances or depressants, physical treatment, and chemical treatment). Unfortunately, the application of traditional use of depressants is questionable since there are different or even contrast theoretical explanations of their adsorption mechanism on the plastics´ surfaces. In this article, a brief theoretical overview is presented summarizing the possible mechanisms of the selective adsorption of organic depressants from the standpoint of modern surface thermodynamics approaches. On the other hand, the method of chemical treatment of the plastics´ surfaces known as the selective hydrophobic modification is better studied and so understood. Therefore, the influence of NaOH solutions as well as of two plasticizers (diisodecyl phtalate and diethylen glycol dibenzoate) on the surface wettability of PVC and PET plastics has been studied experimentally.

The coagulation rate of colloidal silica (synthetic SiO2) spheres in aqueous solution of hexadecyltrimety-amonium bromide (CTAB) was investigated at the concentration scale of 10-5 - 5×10-4 M and pH of 4.7 8.1. The computer-controlled spectrophotometer was used to detect absorbance of the colloidal system as a function of time. From the absorbance-vs.-time dependence, the coagulation rate constant, stability ratio and critical concentration of coagulation (c.c.c.) have been determined by using a linearization and approximation method. Both methods provided c.c.c. values of the initially hydrophilic silica spheres to be ca. 2×10-4 M CTAB (pH 6.8), suggesting an adsorption-induced hydrophobization of their surface by CTAB cations. A slight influence of pH was also observed, probably related to the ionization degree of the CTAB cations.

Throughout human history, gold has been the most sought-after and well-known precious metal in the world. It is synonymous with wealth in the financial market and jewellery. However, its use has a wide range of applicability in biomedicine, electronic engineering and other industries. Primary gold resources are limited and have been significantly depleted in recent decades. To cover the current demand, it is necessary to process secondary sources containing gold such as heaps, tailings, lean ores or electrical waste. New and especially more efficient technological procedures are needed for the processing of these secondary sources. From an environmental point of view, a hydrometallurgical process is considered to be more appropriate than a pyrometallurgical process, in which very toxic fumes enter the air. This work investigates the leaching of gold from flotation wastes using thiourea. It is flotation waste that is the target group of materials that are a source of precious metals. An interesting gold content is present in our waste sample (Hodruša Hámre tailings pond), but its evaluation depends on the setting of suitable technological conditions. In this work, thiourea is used as an alternative leaching agent to toxic cyanide, which is banned in Slovakia and many countries around the world due to its high environmental risk. The results of the study are described with respect to the gold recovery under optimized thiourea leaching conditions. [ABSTRACT FROM AUTHOR]

Copyright of Inzynieria Mineralna is the property of Polskie Towarzystwo Przerobki Kopalin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Slag is one of the by-products of energy industry which is suitable for secondary industrial processing. Although slag has been successfully used in industrial production for several decades, its use does not achieve the level of its potential. Slag can be used as alkaliactivated materials and utilised in the synthesis of geopolymers. Geopolymers are inorganic polymeric materials with three-dimensional SiOAl frameworks synthesised from aluminosilicates which dissolved in the alkaline medium. This work describes the improvement of mechanical properties of alkali-activated binders - geopolymers made of slag. The effect of mechanical activation on mechanical properties of geopolymers was examined. Mechanical activation was made with a ball mill and different time of milling. Synthesis of geopolymers was carried out in drier at 80°C. Samples were made before and after mechanical activation. The differences in strengths of samples were examined. Mechanical properties such as compressive and flexural strength that was measured were the most significant attributes. Samples were tested after 7, 28 and 90 days. Results show that the mechanical activation is an important factor in the synthesis of slag based geopolymers, which has better properties after mechanical activation. [ABSTRACT FROM AUTHOR]

Copyright of Inzynieria Mineralna is the property of Polskie Towarzystwo Przerobki Kopalin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Inzynieria Mineralna is the property of Polskie Towarzystwo Przerobki Kopalin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Waste Forum is the property of Czech Environment Management Center (CEMC) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Flotation is s physico-chemical process used traditionally to separate various solid materials, including plastics, basing on a difference in their surface wettability. The surface of most plastics is hydrophobic which fact makes the selective flotation separation of target types of plastics from their mixtures with other types of plastic difficult or even impossible. To render the selectivity of the process itself, the surface of some plastics has to be selectively hydrophilized and so flotationally depressed. To make the surface of plastic selectively hydrophilic and thus nonfloatable, various methods have been testing such as adsorption of wetting agents or a physical treatment (flame, ozonization, plasma, photocatalytic, etc.). However, a potential of selective chemical treatment by incipient alkaline hydrolysis is recently emphasized, as exemplified by analyzing the surface hydrophilization of polyethylene terephthalate (PET) submerged with polyvinylchloride (PVC) in NaOH solutions even at ambient temperature and for a very short period of time. Indeed, the NaOH-pretreatment surface of PET foils was found to become hydrophilic (nonfloatable) to such an extent that flotation recovery and selectivity of PVC foils, whose surface was left almost untouched (and so entirely floatable) increased appreciably. [ABSTRACT FROM AUTHOR]