Jana Ficeriová

Thiosulfate leaching of gold from a mechanically activated CuPbZn concentrate

Abstract The hydrometallurgical processing of complex concentrates represents an ecologically attractive alternative with respect to classical pyrometallurgical technologies. The leaching of gold from a mechanochemically pretreated CuPbZn complex sulfide concentrate of Slovak origin using ammonium thiosulfate was studied. Physicochemical transformations in the concentrate due to mechanical activation have an influence on the rate of extraction and the recovery of gold. It was possible to achieve 99% gold recovery within 45 min for a sample mechanically activated at an energy input of 403 kWh t −1 . Only 54% of gold were recovered from the as-received concentrate in 120 min. Mechanical activation proved to be an appropriate pretreatment for this CuPbZn concentrate before extraction of gold into thiosulfate leaching solution.

Thiourea leaching of silver from mechanically activated tetrahedrite

Abstract The thiourea leaching of silver from a tetrahedrite concentrate mechanically activated in a planetary mill or an attritor was studied. It was found that the two types of equipment gave rise to different rates of new surface formation and of crystal structure disordering. The rate of thiourea leaching of silver from tetrahedrite (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13 is a structure-sensitive quantity, while the dependence of the rate constant of leaching on the empirical coefficient S A (1 − R) (SA = specific surface, R = disordering of tetrahedrite structure) exhibits a linear character with equal slope for both types of mills. The results are also of prognostic character because they enable us to propose suitable equipment for intensive grinding depending on the demand for fineness or reactivity of the solid substances.

Leaching of antimony and mercury from mechanically activated tetrahedrite Cu12Sb4S13

Abstract In this study the physico-chemical transformations and leachability of antimony and mercury from tetrahedrite concentrate mechanically activated by intensive grinding in a planetary mill were investigated. It has appeared that the leaching of antimony and mercury from tetrahedrite in alkaline solution of sulphide solution is a structure-sensitive reaction. The temperature dependence of both reactions investigated in the temperature interval 298–363 K has shown that these reactions do not involve any change in mechanism. The experimental activation energies found in this connection were E = 7 kJ mol −1 for the leaching of mercury and E = 33 kJ mol −1 for the leaching of antimony.

Silver leaching from a mechanochemically pretreated complex sulfide concentrate

Abstract The intensification of thiourea leaching of silver from a silver-bearing complex sulfide concentrate (Casapalca, Peru) using mechanochemical alkaline leaching as the pretreatment step was investigated. The leaching of “as-received” concentrate in an acid thiourea solution resulted in 5% Ag dissolution. After pretreatment, 90% of the silver was leached within 10 min. The mechanochemical pretreatment resulted in up to 78% of tetrahedrite degrading and an increase in the specific surface area of the concentrate from 0.3 to a maximum of 15.7 m 2 g −1 . The pretreatment was performed in an attritor using variable milling times and sample weights. The physicochemical changes in the concentrate as a consequence of mechanochemical pretreatment had a pronounced influence on the subsequent silver extraction.

Leaching of Gold and Silver from Crushed Au-Ag Wastes

Au-Ag noble metal wastes represent a wide range of waste types and forms with various ballast elements and components. The thiourea process of gold and silver extraction from ores, concentrates or secondary raw materials con- sists of gold and silver leaching into the thiourea solution and the consequent precipitation of these metals from the solu- tion. Due to the non-toxic character of thiourea it is the perspective alternative to the up to now most frequently used cya- nide method. The thiourea leaching of gold and silver from electronic waste, goldsmiths waste and ceramic waste using crushing as the pretreatment step was investigated. For electronic waste, it was possible to achieve 97 % gold and 94 % silver recovery within 120 minutes of thiourea leaching. Up to 98 % of gold and 96 % of silver were recovered from gold- smiths waste after 60 minutes of leaching. In the case of ceramic waste, we achieved up to 98 % gold and 97 % silver ex- traction efficiency after only 45 minutes of leaching. In comparison with the classical cyanide leaching, thiourea leaching acts faster and without a harmful environmental impact.

Effect of mechanical activation on thiosulfate leaching of gold from complex sulfide concentrate

Abstract The use of mechanical activation to enhance gold recovery from a CuPbZn complex sulfide concentrate was investigated. The effects of milling time, ball size, sample to ball ratio and milling speed on thiosulfate leaching were studied. Under optimum conditions of milling time 1 h, ball size 20 mm, sample to ball ratio 1/15 and mill speed 600 r/min, nearly 78% of sample is amorphized, particle size decreases from d 100 =30 μm to d 100 =8 μm, specific surface area increases from 1.3 m 2 /g to 4.6 m 2 /g and gold recovery enhances from 17.4 % in non-activated sample to 73.26 %.

Mechanochemically Synthesised ZnxCd1-xS Nanoparticles for Solar Energy Applications

The mechanochemical solid-state synthesis of ZnxCd1-xS nanoparticles from zinc acetate, cadmium acetate and sodium sulphide in a planetary laboratory mill is described. Through changing the molar ratio of the Zn and Cd precursors, ZnxCd1-xS nanoparticles of different composition were prepared. Structural, surface and morphological properties were investigated by XRD, XPS, SEM and UV-VIS. Diffusion structural diagnostics was characterised by the emanation thermal analysis (ETA) results measured on heating of the samples. The cubic phase was found to be stable under mechanochemical treatment, as determined by XRD. The mixed phases were found to have ideal solution behaviours. In addition, microstructural characterisation indicated that mechanochemical treatment resulted in a structural refinement with a surface weighted crystallite size about 2 nm. The additional information of microstructure development and transport properties of the samples on heating was obtained by ETA. The calculated lattice parameters of mixed crystals linearly depend on the composition of ZnxCd1-xS nanoparticles. The S(2p), Zn(2p) and Cd(3d) core levels of the ZnxCd1-xS nanocrystallites reveal two different types of sulphur, zinc and cadmium unlike bulk CdS and ZnS. The calculated results indicate that the quantum-size effect in the nanoparticles is not negligible. The differences in the absorption edge and the emission peak position of the nanoparticles depend not only composition. Applied high-energy milling is a facile, efficient, and scalable process that does not require a solvent and can be performed under ambient conditions. Therefore, it is a promising candidate for the production of nanocrystalline materials.

Influence of milling on the adsorption ability of eggshell waste

Eggshell waste was successfully used for the removal of heavy metal ions from model solutions. The effect of ball milling on the structure and adsorption ability of eggshell (ES) and its membrane (ESM) was investigated, with the conclusion that milling is benefitial only for the ES. The adsorption experiments showed that the ESM is a selective adsorbent, as the adsorption ability toward different ions decreased in the following order: Ag(I) > Cd(II) > Zn(II). The obtained Qm values for Ag(I) adsorption on the ESM and ES were 52.9 and 55.7 mg g(-1), respectively. The potential industrial application of ES was also demonstrated by successful removal of Ag(I) from the technological waste.