The Use of Mining Waste Materials for the Treatment of Acid and Alkaline Mine Wastewater

The mining of metal ores generates both liquid and solid wastes, which are increasingly important to manage. In this paper, an attempt was made to use waste rocks produced in the mining of zinc and lead to neutralizing acid mine drainage and alkaline flotation wastewater. Waste rock is a quartz-feldspar rock of hydrothermal origin. It is composed of, besides quartz and potassium feldspar (orthoclase), phyllosilicates (chlorite and mica), and sulfides (chiefly pyrite). To determine its physicochemical parameters and their variability, acid mine water and flotation wastewater were monitored for 12 months. Acid mine drainage (AMD) is characterized by a low pH (~3), high zinc concentration (~750 mg·L−1), and high sulfate content (~6800 mg·L−1). On the other hand, the determinations made for flotation wastewater showed, among others, a pH of approximately 12 and ca. 780 mg·L−1 of sulfates. AMD and flotation wastewater neutralization by the waste rock was shown to be possible and efficient. However, in both cases, the final solution contained elevated concentrations of metals and sulfates. Premixing AMD with alkaline flotation wastewater in the first step and then neutralizing the obtained mixture with the waste rock was considered the best solution. The produced solution had a circumneutral pH. However, the obtained solution does not meet the legislative requirements but could be further treated by, for example, passive treatment systems. It is noteworthy that the proposed approach is low cost and does not require any chemical reagents.

ZnO Nanoparticles: A Promising Anticancer Agent

Nanoparticles, with their selective targeting capabilities and superior efficacy, are becoming increasingly important in modern cancer therapy and starting to overshadow traditional cancer therapies such as chemotherapy radiation and surgery. ZnO nanoparticles, with their unique properties such as biocompatibility, high selectivity, enhanced cytotoxicity and easy synthesis, may be a promising anticancer agent. Zinc, as one of the major trace elements of the human body and co-factor of more than 300 mammalian enzymes, plays an important role in maintaining crucial cellular processes including oxidative stress, DNA replication, DNA repair, cell cycle progression and apoptosis. Thus, it is evident that an alteration in zinc levels in cancer cells can cause a deleterious effect. Research has shown that low zinc concentration in cells leads to the initiation and progression of cancer and high zinc concentration shows toxic effects. Zinc-mediated protein activity disequilibrium and oxidative stress through reactive oxygen species (ROS) may be the probable mechanism of this cytotoxic effect. The selective localization of ZnO nanoparticles towards cancer cells due to enhanced permeability and retention (EPR) effect and electrostatic interaction and selective cytotoxicity due to increased ROS present in cancer cells show that ZnO nanoparticles can selectively target and kill cancer cells, making them a promising anticancer agent.

Hydrothermal Synthesis of Zinc-Doped Magnetite Nanoparticles

ABSTRACTHydrothermal techniques have been used to synthesize samples of ZnxFe3−xO4 (x=0.0-1.0) starting with ZnSO4.7H2O/FeSO4.7H2O aqueous solution. The sequence of phases, structural and magnetic properties were followed by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). Refinement of the XRD spectra yielded the dependence of the lattice parameters of zinc–doped magnetite and zinc ferrite phase as function of the Zn molar concentration x. As well, the particle diameter was derived as a function of Zn content x. As a function of Zn concentration, the phase content of hydrothermally synthesized samples was found to consist of zinc-doped magnetite, goethite and zinc ferrite. Consistent with the XRD results, Mössbauer spectroscopy data indicate the presence of magnetite and goethite at x≤0.2, magnetite and zinc ferrite at x≤0.9 and pure zinc ferrite only at high zinc concentrations. The presence of different magnetite phases was confirmed by TEM and particles with a size of 50 nm were identified. Our results show that zinc ferrite is formed at high zinc concentration by the hydrothermal method and an acicular component of goethite-magnetite is obtained at low zinc content.

EMPIRICAL ESTIMATES OF PHYSICAL PARAMETERS FROM ELECTRICAL RESISTIVITY MEASUREMENTS ON FERRITES

Measurements on the electrical resistivity of Mn 1−x Zn x Fe 2 O 4 ferrites with 0<x< 0.15 in the temperature range 300 K <T<450 K , have been carried out. Analysis of the normalised electrical resistivity of these ferrites shows deviations from linearity both at low and high temperatures. There exists a deviation in the electrical resistivity at 300 K at high zinc concentration which may be due to hopping of electrons between Fe +2 and Fe +3 ions at octahedral sites.