This paper investigates interaction processes of the Fe 3þ , Cu 2þ , Ni 2þ , and Co 2þ cations with humic acids isolated from brown coals of Ekibastuz basin. It was demonstrated that the sorption of heavy metal ions by humic acids (HA) depends on the concentration and nature of cations and decreases in the order of Fe 3þ > Cu 2þ > Ni 2þ > Co 2þ ; while increase in the concentration of humic acids (HA) results in the higher yield of ions and metals. The occurrence of ion exchange and complexation reactions in metal-humic acid systems is confirmed by the appearance of new bands and the shift of the absorption bands corresponding to stretching and deformation vibrations of carboxylate ions, C ¼ O and OH groups. The occurrence of these processes is also evidenced by spectrophotometric data, as well as a decrease in the pH of the solution due to deprotonation of humic acids during these reactions. Thus, based on the data on the degree of sorption of metal cations by humic acids, the results of infra-red spectroscopy and spectrophotometry, it can be concluded that the Fe 3þ , Ni 2þ , Co 2þ , Cu 2þ cations interact with HA by the ionic mechanism and by the complexation mechanism with electrondonating functional groups. Electrochemical studies of the Cu 2þhumic acid system carried out by the method of cyclic voltammetry also indicate the occurrence of the interaction of humic acid with copper cations. Modification of humic acid with copper ions shows the electrochemical activity of copper immobilized on the surface of dispersed humic acid, which is important for the implementation of electrocatalytic reactions on modified glassy carbonhumic electrodes.

Molybdenum is one of the valuable metals for the industry; its special properties make it extremely urgent to study the process of separation of molybdenum from other impurities. The article considers the optimization of electrochemical separation of molybdenum from Mo-W system. The electrochemical dissolution of molybdenum and tungsten in solutions of LiCl and NH4NO3 in dimethylsulfoxide was studied using polarization curves and calculation of the efficiency of anodic dissolution of molybdenum in the presence of tungsten. The electrolyte with a composition of 0.5 M LiCl; 5.2 M dimethylsulfoxide; 32.2 M water was selected as an effective solution for the electrochemical separation of molybdenum in the potential range of 1.0‒2.2 V. Results obtained in this study can be used for the development of selective separation method in the molybdenum production.

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Molybdenum (Mo) is a refractory metal used principally as an alloying agent in steels, cast irons, and super alloys to enhance hardness, strength, toughness, wear and corrosion resistance and it is also widely used in catalytic applications, lubricants and pigments. The single electrodeposition of Mo from aqueous solutions cannot be achieved but Mo it can be co-deposited as an alloy with iron group metals (induced co-deposition). In this study, the electrodeposition of Mo/MoO x from dimethyl sulfoxide solutions on a copper substrate has been investigated. Different experimental electrodeposition parameters have been assessed (i.e., supporting electrolyte concentration and small amounts of water to the electrolytic bath) to analyze their influence on mechanism of induced Mo/MoO x deposition. Linear scan voltammetry has been used to follow up the electrodeposition of Mo/MoO x films. Film morphology has been characterized using scanning electron microscopy (SEM), compositional analysis was performed using X-ray photoelectron spectroscopy. Mo bearing films were also chemically characterized by ICP-OES analysis. An electrodeposition mechanism was developed and discussed.