Electrolysis of Gold from Filtration Waste by Means of Mechanical Activation

The intensification of the gold thiourea leaching from a filtration waste (Košice, Slovakia) using mechanical activationas the pretreatment step has been studied. The leaching of “as-received“ sample in an acid thiourea solution resulted in 65 % Audissolution. However, after mechanical activation in a planetary mill 99 % of the gold was leached. The optimum redox potential forelectrolysis is in the range 500-523 mV for the gold extraction 99.79 % from the mechanically activated sample. The mechanicalactivation resulted in an increase of the specific surface area of the waste from 0.7 m2g-1 to a maximum value of 13.5 m2g-1. The physicochemicalchanges in the filtration waste as a consequence of mechanical activation had a pronounced influence on the subsequent goldextraction

A possible way to storage carbon dioxide on mechanically activated olivine (Mg,Fe)2SiO4

This paper deals with mechanical carbonation of olivine by dry and wet modes. Mechanical activation and carbonation of the olivine samples have been performed using a planetary mill, Pulverisette 6 (Fritsch, Germany). A series of experiments were produced where the activated products were exposed to carbon dioxide during activation in presence of water and by dry mode of milling. To identify mechanically induced changes in surface of the mineral, specific surface area measurements have been used. To identify carbon dioxide sequestration, infrared spectroscopy and determination of total carbon have been used. Infrared spectroscopy seemed to be a suitable method for characterization of CO2 absorption on mechanically modified olivine

Applied mechanochemistry of solids (a review)

This review paper deals with the application of broad possibilities of mechanochemistry in mineral processing, extractive metallurgy, chemical engineering, building industry, coal industry, materials engineering, agriculture, pharmacy and waste treatment. In several applications pilot plants units or full commercial units were successfully applied. The environmental aspects of these processes are particularly attractive. The main advantages in comparison with traditional technological procedures are decrease in number of technological stages, exclusion of operations that involve the use of solvents and gases and last but not the least the possibility obtaining a product in the metastable state which is difficult to obtain using traditional technological methods. There is a great potential of mechanochemistry in technology and several examples with a possibility for industrial applications are given

A processing method of the goldsmith’s and electronic Au-Ag-containing wastes

Veľké množstvá odpadov z elektrických a elektronických zariadení sa hromadia v celej Európe. Každý spotrebiteľ vyprodukuje priemerne 16 kg tohto odpadu za rok, čo v Európe predstavuje celkovo šesť miliónov ton za rok. Ide o obrovské plytvanie zdrojmi. Znamená to taktiež veľké ekologické nebezpečenstvo, keďže elektrické spotrebiče a elektronické zariadenia obsahujú vysoko toxické ťažké kovy a organické znečisťujúce látky. Podľa nových predpisov EÚ budú musieť výrobcovia odteraz platiť za zber a likvidáciu týchto výrobkov. Odpady ušľachtilých kovov Au-Ag predstavujú širokú škálu typov a foriem odpadov s rôznymi balastnými prvkami aj zložkami. Problematika spracovania odpadov s obsahom Au a Ag je vysoko aktuálnou v celosvetovom meradle z hľadiska hodnoty a špecifických vlastností týchto kovov ako aj ich nenahraditeľnosti v oblasti bankovníctva, zdravotníctva, priemyslu a v neposlednom rade aj v samotnej výrobe a predaji zlatníckych výrobkov. Predkladaný návrh možnosti spracovania Au-Ag zlatníckych a elektronických odpadov si kladie za cieľ získať zlato a striebro v kovovej forme. Aplikácia navrhovaného procesu spracovania uvedených Au-Ag odpadov predstavuje pre spoločnosť praktický, ekonomický a zároveň ekologický význam pri ich spracovávaní. Získavanie zlata, resp. striebra z Au-Ag odpadov je mimoriadne dôležité v podmienkach inflačného vývoja, kedy tieto ušľachtilé kovy sú stabilným zdrojom pokrývania potrieb spoločnosti

An influence of mechanical activation on the selectivity of tetrahedrite acid leaching

Sulphidic mineral - tetrahedrite Cu12Sb4S13 was subjected to leaching in a H2SO4 medium. Physico-chemical changes of a mechanically activated mineral were investigated before and after leaching using the infrared spectroscopy and the scanning electron microscopy. The mechanical activation of the mineral resulted in the mechanochemical surface oxidation and the formation of sulphates and iron carbonate. Further, the specific surface area and the crystal structure disordering of the mineral increased. These aspects influence the kinetics and the selectivity of acid leaching of tetrahedrite. The effect of the reaction surface decreases due to the agglomeration during the milling and the formation of iron hydroxyoxides or iron hydroxysulphates from admixed pyrite and adversely affects the extraction rate of metals from tetrahedrite

Mechanochemical Synthesis of Nanocrystalline CdS in a Laboratory and Industrial Mill

Nanocrystalline materials have been of interest of more than 20 years and this interest is still increasing. The preparation and characterization of different chalcogenides have attracted a considerable attention due to their important nonlinear properties, luminiscent properties and other important physical and chemical properties. The main cause is in their unusual properties based on the high concentration of atoms in interfacial structures and the relatively simple ways of their preparation. Nanoparticles of semiconductors have many potential applications in the area of advanced materials. These materials can be synthesized via solid state reactions where the recovery degree can be strongly enhanced by the intervention of mechanical activation. Mechanochemical synthesis belongs among the synthesis route which can effectively control and regulate the course of solid state reactions.This paper describes structural and surface properties of cadmium sulphide nanoparticles synthesized in a planetary mill and in an eccentric vibratory mill. The main aim of this paper was to illustrate the potential of this technique for the large-scale production of CdS nanopowder.CdS nanoparticles were successfully synthesized by the mechanochemical route from the cadmium acetate and natrium sulphide. Structure properties of the as-prepared products were characterized by X-ray powder diffraction. X-ray diffraction patterns reveal the crystalline nature of CdS nanoparticles. Hexagonal ¿-CdS greenockite together with cubic hawleyite À-CdS are present among the products of mechanochemical synthesis. The methods of SEM, particle size analysis and low temperature nitrogen sorption were used to analyze the surface composition. The SEM measurements show the aggregates of small nanocrystals in which particle sizes of 5-9 nm were estimated by ScherrerLs formula.The cadmium sulphide nanoparticles are obtained in the simple step, making the process attractive for industrial applications. Industrial ball mills capable of processing large quantities are readily available, consequently the scaling up of the mechanochemical process is possible. The presented solid-state reaction opens its application also for the engineering area of advanced materials synthesi

Arsenic Sorption on Mechanically Activated Magnetite and Olivine

Arsenic sorption on mechanically activated minerals such as magnetite Fe3O4 (Kiruna, Sweden) and olivine (Mg,Fe)2SiO4 (Ǻheim,Norway) has been studied and compared in this work. Experiments were carried out with non-activated and mechanically activatedsamples. The activation of both minerals was performed in a planetary mill at different milling conditions. The specific surface areaand consequent sorption activity were enhanced by mechanical activation. The using of olivine seems to be better than magnetite fromthe point of view of milling time, which is necessary for achievement of the same sorption effect

Leaching of gold, silver and accompanying metals from circuit boards (PCBs) waste

Au-Ag noble metal wastes represent a wide range of waste types and forms, with various accompanying metallic elements.The presented leaching strategy for Au-Ag contained in circuit boards (PCBs) aims at gaining gold and silver in the metallic form.Application of the proposed ammonium thiosulphate leaching process for the treatment of the above mentioned Au-Ag containing wastesrepresents a practical, economic and at the same time an ecological solution. The ammonium thiosulphate based leaching of gold and silverfrom PCBs waste, using crushing as a pretreatment, was investigated. It was possible to achieve 98 % gold and 93 % silver recovery within48 hours of ammonium thiosulphate leaching. This type of leaching is a better leaching procedure for recovery of gold and silver from PCBwaste than the classical toxic cyanide leaching. 84 % Cu, 82 % Fe, 77 % Al, 76 % Zn, 70 % Ni, 90 % Pd, 88 % Pb and 83 % Sn recovery ofthe accompanying metals was achieved, using sulphuric acid with hydrogen peroxide, sodium chloride and aqua regia. A four steps leachingprocess gave a very satisfactory yield and a more rapid kinetics for all observed metals solubilization than other technologies

Study of the silver ions cementation after mechanical activation of cementator

Thiosulphate leaching of silver is a proposed alternative to cyanide or thiourea leaching for certain types of refractory silver ores and secondary resources. Traditional method for the recovery of rare metals from various sources by hydrometallurgy is leaching followed by cementation onto zinc powder and electrowinning. Silver cementation is an inexpensive and simple way to deposit thin metal films. Cementation of silver onto zinc powder, treated by mechanical activation, from thiosulphate solutions was studied by measuring Ag+ ions concentration in the solution. The high energy attrition and planetary ball milling in methanol was applied for the mechanical activation of zinc powder. The changes in the particle size distribution and surface area of cementator, occurring during mechanical treatment have been registered. The observed changes in the physicochemical properties illustrate the possibility of applying activation to modify the surface and/or volume properties of zinc powder and its further application in well-known hydrometallurgical process of cementation. The study was also focused on the changes in the concentration of zinc and pH as a function of reaction time. The morphology of cementation products on zinc powder was also investigated