A coprecipitation of copper(II) and zinc(II) from complex sulfate solutions with natural calcite was investigated. The main features of the process and mineral forms of incorporation of heavy metals in a solid phase were determined. Sequential precipitation proceeds at pH 5.3–5.5 and 6.5–7.0 for copper(II) and zinc(II), respectively, in mode of pH autoregulation. Sediments were represented by copper and zinc hydroxosulfates: posnjakite and namuvite, respectively. Smithsonite and hydrozincite formation was not detected unlike precipitation of zinc(II) from monometallic sulfate solutions. The mechanism explaining the lack of zinc carbonates and the formation of mixed cation salts was suggested. The formation of hydroxosulfates should be considered in the thermodynamic description of the interaction of heavy metals with natural calcium carbonate.

Pine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.

This paper presents the results of studies on the reduction of dispersed cobalt and nickel metal powders from their salts in ammonia-alkaline aqueous solutions under hydrothermal autoclave conditions. A unified and environmentally friendly method for producing these powders has been developed. Hydrazine hydrate, with a 25–50 % excess of the stoichiometric ratio, was used as a reducing agent. This choice allows for obtaining metal phases that are chemically uncontaminated by decomposition products. The experiments determined the conditions for the quantitative reduction of cobalt (II) and nickel (II) ions from ammonia-alkaline aqueous solutions. The synthesis temperature for the dispersed phases ranged from 110 to 155 °C. It has been demonstrated that under the conditions used, the process is completed quantitatively within 60 min. Metal concentrations in the solutions were determined using atomic absorption spectroscopy. The results of the X-ray phase analysis confirm that cobalt forms in the HCP lattice, while nickel forms in the FCC lattice. No other phases, including X-ray amorphous phases, were observed. It was found that with an increase in the hydrothermal synthesis temperature from 110 to 155 °C, the specific surface area of cobalt increased by more than 1.5 times, and that of nickel black powders increased by approximately 2 times. Scanning electron microscopy revealed that cobalt is formed in the shape of lamellar particles with a lateral size of about 500 nm and a thickness of 50 nm, which aggregate into fractal structures. Nickel is represented by spherical particles arranged in chain-like structures. Using X-ray photoelectron spectroscopy, it was determined that the surface of the materials is covered with oxidized forms. The surface atomic concentration of cobalt (0) was approximately 2 %, while that of nickel (0) was about 25 %.

A systematic study of the compositions of individual microspheres with sizes of <2.5 μm in a fine fraction of fly ash after the pulverized combusti

The structure of Kaa-Khem coal and its carbon derivatives is analyzed by Raman spectroscopy and X-ray phase analysis; in the production of the carbon deriv