Peter Baláz

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.

Arsenic Sulphide As4S4 Nanoparticles: Physico-Chemical Properties and Anticancer Effects

In this study, arsenic sulphide As4S4 nanoparticles have been prepared, by high-energy wet milling, in the presence of sodium dodecylsulphate, which acts a surfactant. Solid state properties of the nanoparticles were characterised by XRD, Raman scattering, specific surface area and particle size distribution. Changes in surface areas of the particles, in the 0.2 - 5.4 m2 g-1 range, and nanosize distributions, in the 100 - 250 nm range, characterise the surface and morphological properties of nanorealgar. Raman scattering revealed various species in the milled sample that indicate a disproportionate reaction (3As4S4 → 4As2S3 + 4As) occurring as a consequence of milling. Anticancer effects, of the milled species, were confirmed for the human multiple myeloma U266 and OPM1 cell lines. Dissolution experiments in simulated gastric fluid show a possibility for the application of the realgar nanoparticles as an oral dose in future arsenic drug cancer treatments.

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.

Preparation of Nanocrystalline Copper and Copper Silicon Sulphide by Mechanochemical Route

The composition and properties of powders prepared by high-energy milling of copper sulphides with silicon have been studied by methods of X-ray diffractometry and surface area measurement. The combination of several methods was utilized to develop a coherent picture of the process. The overall process of mechano-chemical transformations in copper sulphide-silicon system proceeds via complicated mechanism with several overlapping steps. Phase transformations in copper sulphide phases, the formation of elemetal nanocopper with X-ray determined particle size of 23 nm and creation of ternary sulphide Cu8SiS6 with anomalous surface area values are the main products of the mechanochemical reaction.

Mechanochemical preparation of metal/sulphide nanocomposite particles

The mechanochemical reduction of stibnite (Sb2S3), copper sulphide (Cu2S), galena (PbS) and auripigment (As2S3) with elemental Fe has been studied. Metallic Sb, Cu and Pb are obtained due to the reducing power of iron. The metal/sulphide nanocomposite particles have been characterised by XRD, SEM and TEM methods. The reduction processes are very straightforward and fast and can be carried out at ambient temperature.

Realgar nanoparticles versus ATO arsenic compounds induce in vitro and in vivo activity against multiple myeloma

Multiple myeloma (MM), a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow, remains incurable despite the use of novel and conventional therapies. In this study, we demonstrated MM cell cytotoxicity triggered by realgar (REA; As4S4) nanoparticles (NREA) versus Arsenic trioxide (ATO) against MM cell lines and patient cells. Both NREA and ATO showed in vivo anti‐MM activity, resulting in significantly decreased tumour burden. The anti‐MM activity of NREA and ATO is associated with apoptosis, evidenced by DNA fragmentation, depletion of mitochondrial membrane potential, cleavage of caspases and anti‐apoptotic proteins. NREA induced G2/M cell cycle arrest and modulation of cyclin B1, p53 (TP53), p21 (CDKN1A), Puma (BBC3) and Wee‐1 (WEE1). Moreover, NREA induced modulation of key regulatory molecules in MM pathogenesis including JNK activation, c‐Myc (MYC), BRD4, and histones. Importantly, NREA, but not ATO, significantly depleted the proportion and clonogenicity of the MM stem‐like side population, even in the context of the bone marrow stromal cells. Finally, our study showed that both NREA and ATO triggered synergistic anti‐MM activity when combined with lenalidomide or melphalan. Taken together, the anti‐MM activity of NREA was more potent compared to ATO, providing the preclinical framework for clinical trials to improve patient outcome in MM.