Parviz Pourghahramani

PbS nanostructures synthesized via surfactant assisted mechanochemical route

PbS nanocrystals using surfactant assisted mechanochemical route has been successfully prepared. The methods of XRD, SEM, surface area and particle size measurements were used for nanocrystals characterization. The XRD patterns confirmed the presence of galena PbS (JCPDS 5–592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline nature in formation of PbS nanostructures where preferential crystal growth in the (200) direction after chelating agent (EDTANa2•2H2O) addition has been observed. The mean volume weighted crystallite size 4.9 nm and 35 nm has been calculated from XRD data using Williamson-Hall method for PbS synthesized without and/or with chelating agent, respectively corresponding with surface weighted crystallites sizes of 2.9 and 18.8 nm. The sample prepared without surfactant yields the smaller crystallites and the higher microstrain compared with surfactant assisted synthesis. The obtained results illustrate a possibility to manipulate crystal morphology by combining effect of milling and surfactant application.

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.

An Experimental Investigation on the Copper Recovery from Flotation Tailing Dams by Reflotation

In this study, the possibility of copper recovery from flotation tailing of Mazraeh copper mine was investigated. Magnetic separation method was used for concentration of non-magnetic minerals, especially copper bearing minerals, from iron minerals. As a result, copper grade increased up to 0.18% and its recovery reached 86%. Due to mineral’s oxidized surface, accompanied oxide minerals and large quantities of fine particles (i.e. about 80% and 57% were finer than 37 and 15 μm in the sample, respectively), flotation of copper was very difficult. In this regard, the effects of important factors including solution pH, type and collector dosage, dispersant, impeller speed, type of frother, percent solid and surface sulfurization were studied. It was concluded that copper recovery of 52% and copper grade of 2.7% could be obtained under following conditions: pH: 11, Collector: Z11 with 40 g/t, Impeller speed: 1400 rpm, Frother: A65, percent solid: 10% and surface sulfurization by Na2S with 1000 g/t. On the other hand, the addition of sodium silicate as a dispersant showed a negative effect on the flotation performance.