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

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

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

Leaching of gold from a mechanically and mechanochemically activated waste

The intensification of leaching of gold from a waste using mechanical activation (milling in water) and mechanochemical activation(milling in thiourea solution) were studied as the pretreatment steps. The leaching of “as-received“ sample in an acid thiourea solutionresulted in 78 % Au dissolution, after mechanical activation 98 % and mechanochemical activation up to 99 % of the gold was leachedduring 120 min. The mechanochemical activation resulted in an increase of the specific surface area of the waste from 0.6 m2g-1to a maximum value of 20.5 m2g-1. The activation was performed in an attritor using variable milling times. The physico-chemical changesin the waste as a consequence of mechanochemical activation had a pronounced influence on the subsequent gold extraction

Influence of mechanical activation on the leaching of non-ferrous metals from a CuPbZn complex concentrate

The aim of study was to research the procedures of copper, lead and zinc leaching from CuPbZn complex sulphide concentrate during the intervention of mechanical activation.Mechanical activation belongs to innovative procedures, which intensifies technological processes by means of creation of new surfaces and making defective structure of solid phase. Mechanical impact on the solid phase is a suitable procedure to ensure the mobility of its structure elements and to accumulate the mechanical energy that is later used in following processes of leaching.This paper deals with the intensification of the chloride and thiourea leaching of copper, lead and zinc from a CuPbZn complex concentrate of Hodrua-Hámre (Slovak deposit) by using the mechanical activation in an attritor. Ferric chloride and thiourea were used as leaching reagents. The leaching of the concentrate with ferric chloride solution afforded 23 % recovery of Cu, 99 % of Pb and 28 % of Zn. 9 % recovery of Cu, 17 % of Pb and 3 % of Zn were achieved by the leaching with thiourea. Thus results showed that the extraction of Cu, Zn and also Pb in the case of thiourea leaching was low. The use of milling in the attritor as an innovation method of pretreatment leads to the structural degradation and increasing the surface area of the investigated concentrate from the original value of 0.18 m2g-1 to the maximum value of 4.67 m2g-1. This fact manifested itself in the subsequent process of extraction of Cu, Pb and Zn into the chloride and thiourea solutions. Our results indicate more effective leaching of pretreated concentrate in the chloride medium with recoveries of 84 % Zn and 100 % Pb. In thiourea, the recoveries for Zn and Pb were low, however 99 % Cu can be recovered. In regard to the economy, the extraction of Cu, Pb and Zn was studied in this work with the aspect of minimal energy consumption during milling. The maximum recoveries of non-ferrous metals in the solutions of ferric chloride and thiourea were found with the minimal grinding energy of 403 kWht-1. A favourable kinetics of the process was observed for Pb in the case of chloride leaching. The results show that the mechanical activation essentially influences the copper, lead and zinc leaching kinetics, which is a favourable effect for the economy of the leaching process.The application of mechanical activation has grown in the framework of laboratory research. The Institute of Geotechnics of SAV has also achieved significant theoretical results in the study of mechanical activation of sulphides and their reactivity in different solid-phase reactions with the effect on industrial applications. The Institute has developed a technology of mechanochemical leaching (process MELT) which was successfuly tested in a pilot plant unit

Mechanochemical pretreatment and thiosulphate leaching of silver from complex sulphide concentrate

The refractory character of complex ores and concentrates is at present one of the main problems of their metallurgical processing. The research activity in this sphere is aimed at the methods of improving the process of metal extraction from the sulphidic minerals representing the major components of these ores and concentrates.One of the sulphidics components of complex ores is tetrahedrite. It represents a compound of complicated structure containing several metals among which copper, antimony and arsenic prevail. Some deposits are aspecially rich in silver. The Peruvian complex sulphidic concentrate of provenience Casapalca is each from these rich deposits.In this study the physico-chemical transformations and leachability of silver from Peruvian sulphide concentrate mechanochemically activated by ultrafine alkaline milling in the attritor were investigated. The experiments with alkaline leaching of using samples have shown that this hydrometallurgical process represents an effective method to prepare of treated concentrate with physico-chemical means for further leaching process. Ammonium thiosulphate were used as agent for obtain of silver to leaching solution.The leaching of as-received concentrate with the alkaline thiosulphate solution afforded only 6 % Ag into leach. The use of milling in attritor as an innovation method of pretreatment brought about 57% of structure degradation of tetrahedrite as silver-bearing mineral in concentrate as well as to the increase in specific surface area from the original value 0.26 m2g-1 to the maximum value of 16 m2g-1. This pretreatment has been performed in an attritor using the method of experiment design. The physico-chemical changes had influence on the two step process of thiosulphate leaching of silver.The optimum results obtained by mechanochemical pretreatment and subsequent leaching of the concentrate with ammonium thiosulphate were achieved by using milling time 30 min and weight of sample 30 g. Maximum 99 % recovery of Ag was reached already after 3 min of leaching

Mechanochemically synthesized nanocrystalline ternary CuInSe2 chalcogenide semiconductor

The synthesis of nanocrystalline ternary CuInSe particles prepared by high-energy milling in a planetary mill in an argon atmosphere from copper, indium and selenium was reported. CuInSe particles crystallize in the tetragonal structure with the crystallite size of about 30.5 nm. The Raman spectrum of CuInSe nanoparticles shows a strong peak at 176 cm corresponds to the A phonon mode of tetragonal CuInSe chalcopyrite. HRTEM measurements also revealed the presence of nanocrystals with the size of 10-20 nm with the tendency to form agglomerates. The optical absorption study shows that nanoparticles have direct optical band gap energy of 1.8 eV. The quantum size effect of the particles was confirmed also by PL measurement.This work was promoted by the Slovak Research and Development Agency under the contract No. APVV-14-0103. The support through the Slovak Grant Agency VEGA (projects 2/0027/14, 1/0739/16, 2/0051/14) is also thankfully acknowledged. The authors also appreciate the help of the European Regional Development Fund- project NANOCEXMAT 2 (ITMS 26220120035) and European Union through the CT-2011-1-REGPOT285895 AL-NANOFUN project (Advanced Laboratory for the Nano-Analysis of novel Functional materials), for the microscopy facilities sited in Seville