This paper presents an experimentally-proved hydrometallurgical process for selective metals recovery from the waste-printed circuit boards (WPCBs) using a combination of conventional and time-saving methods: leaching, cementation, precipitation, reduction and electrowinning. According to the results obtained in the laboratory tests, 92.4% Cu, 98.5% Pb, 96.8% Ag and over 99% Au could be selectively leached and recovered using mineral acids: sulfuric, nitric and aqua regia. Problematic tin recovery was addressed with comprehensive theoretical and experimental work, so 55.4% of Sn could be recovered through the novel physical method, which consists of two-step phase separation. Based on the results, an integral hydrometallurgical route for selective base and precious metals recovery though consecutive steps, (i) Cu, (ii) Sn, (iii) Pb and Ag, and (iv) Au, was developed. The route was tested at scaled-up laboratory level, confirming feasibility of the process and efficiencies of metals recovery. According to the obtained results, the proposed hydrometallurgical route represents an innovative and promising method for selective metals recovery from WPCBs, particularly applicable in small scale hydrometallurgical environments, focused on medium and high grade WPCBs recycling.

This paper describes the synthesis of tungsten disulfide (WS₂) powder by the sulfurization of tungsten trioxide (WO₃) particles in the presence of additive potassium carbonate (K₂CO₃) in nitrogen (N₂) atmosphere, first at lower temperature (200 °C) and followed by reduction at higher temperature (900 °C). In addition, the ultrasonic spray pyrolysis of ammonium meta-tungstate hydrate (AMT) was used for the production of WO₃ particles at 650 °C in air. The HSC Chemistry^® software package 9.0 was used for the analysis of chemistry and thermodynamic parameters of the processes for WS₂ powder synthesis. The crystalline structure and phase composition of all synthesized powders were analyzed by X-ray diffraction (XRD) measurements. The morphology and chemical composition of these samples were examined by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX).

This paper presents the synthesis of nano-composite Cu-Al2O3 powder by a thermochemical method and sintering, with a comparative analysis of the mechanical and electrical properties of the obtained solid samples. Nano-crystalline Cu-Al2O3 powders were produced by a thermochemical method through the following stages: spray-drying, oxidation of the precursor powder, reduction by hydrogen and homogenization. Characterization of powders included analytical electron microscopy (AEM) coupled with energy dispersive spectroscopy (EDS), differential thermal and thermogravimetric (DTA-TGA) analysis and X-ray diffraction (XRD) analysis. The size of the produced powders was 20-50 nm, with a noticeable presence of agglomerates. The composite powders were characterized by a homogenous distribution of Al2O3 in a copper matrix. The powders were cold pressed at a pressure of 500 MPa and sintered in a hydrogen atmosphere under isothermal conditions in the temperature range from 800 to 900 ?C for up to 120 min. Characterization of the Cu-Al2O3 sintered system included determination of the density, relative volume change, electrical and mechanical properties, examination of the microstructure by SEM and focused ion beam (FIB) analysis, as well as by EDS. The obtained nano-composite, the structure of which was, with certain changes, preserved in the final structure, provided a sintered material with a homogeneous distribution of dispersoid in a copper matrix, with exceptional effects of reinforcement and an excellent combination of mechanical and electrical properties.

This paper presents the production of sintered materials from nano-composite powders obtained by a novel synthesis method, which represents a combination of thermochemical synthesis and mechanical alloying. Produced powders were characterized by an average individual particle size of 30nm, with the presence of a small number of aggregates with a size of 150nm. The positive effect on dispersion strengthening of the copper matrix occurred up to 1 wt.% Al2O3, whereas a further increase of the Al2O3 content showed a negative effect on hardness. The new synthesis method is more suiTab. for composite materials containing maximum 1wt.% Al2O3. By this novel method it is possible to produce composites possessing a good combination of hardness and electrical conductivity.

The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl₂ reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al₂O₃ catalysts. The effect of temperature and time on NiO and NiCl₂ reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl₂ reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al₂O₃ catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina‐based foam and prepared via aerosol route. Properties of the samples before and after low‐temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al₂O₃ catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni‐Pd/Al₂O₃ catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K.