Using the method of solid-phase reaction of AlCl3·6H2O and MgCl2·6H2O with (NH4)2CO3 at room temperature, a Mg–Al layered hydroxide with composition Mg4Al2(OH)12CO3·3.85H2O with the structure of hydrotalcite is obtained. The results of determining the effect of rehydration conditions on the structural and surface properties of layered reduced double hydroxides (LDHs) of magnesium and aluminum are described. It is shown that the samples obtained by reduction of thermally treated initial Mg–Al LDH for 2 h (regardless of the pH of the medium) have specific surface-area parameters (both total area and outer surface area) that are not different from those of the initial LDH sample, and their specific pore volume increases by a factor of 1.3–1.5 (from 0.121 to 0.159–0.183 cm3/g). It is established that the pH of the isoionic point of the rehydrated Mg–Al LDH samples depends only slightly on the rehydration conditions and equals 9.7 ± 9

Layered magnesium aluminum hydroxide Mg 4 Al 2 (OH) 12 CO 3 ⋅3.85H 2 O with the hydrotalcite structure is obtained by the solid-phase interaction of AlCl 3 ⋅6H 2 O and MgCl 2 ⋅6H 2 O with (NH 4 ) 2 CO 3 at room temperature. The change in the phase composition of the products of its heat treatment in the temperature range 180–600°C is studied. It is determined by DSC/TG that the thermal decomposition occurs in two stages: the first stage occurs in the temperature range 180–215°C; the second, in the range 400–440°C. The apparent activation energies E a of both stages of thermal decomposition are found by the model-free Kissinger method to be 62.85 and 141.86 kJ/mol, respectively. The obtained E a values agree well with the literature data and indicate that both stages are single-step kinetic processes.

Mg–Al layered hydroxide of Mg4Al2(OH)12CO3·3H2O composition with hydrotalcite structure was obtained by solid-phase interaction of AlCl3·6H2O and MgCl2·6H2O with (NH4)2CO3. The sorption properties of the obtained sample with respect to nonferrous metal ions—Co2+, Cu2+, Sr2+, and Cs+—are investigated. Experimental data were processed using the Freundlich and Langmuir sorption equations. It is established that the sorption process of these ions is adequately described by the Langmuir monomolecular adsorption equation (the coefficients of determination R2 of the linear forms of the equations are 0.985–0.999. The capacities of the adsorption monolayer of the synthesized Mg–Al layered hydroxide sample were calculated, amounting to 2.13, 2.21, 1.88, and 3.48 mmol/g with respect to Co2+, Cu2+, Sr2+, and Cs+ ions, respectively, which is in good agreement with the values noted in international practice and the adsorption equilibrium constants. Morris–Weber and Boyd diffusion models, Lagergren pseudo-first-order models, and Ho and McKay pseudo-second-order models were used to model sorption kinetics. It is shown that the sorption process is most accurately described by a pseudo-second-order kinetic model and proceeds in a mixed diffusion mode involving not only the outer surface of the material but also the inner surface of its particles due to their porosity in the sorption process. The obtained values of the sorption capacity of the synthesized material indicate the prospects of its application for the extraction of Co2+, Cu2+, Sr2+, and Cs+ ions from industrial wastewater and for drinking water purification.

Samples of Mg–Zn–Al layered double hydroxide (LDH) have been synthesized by solid-phase interaction of Mg, Zn, and Al crystalline hydrates with (NH4)2CO3, and then studied by chemical, X-ray phase analysis, as well as by Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods. The paper presents results of studies of structural and surface properties (specific surface area and volume of pores, distribution of pores by their diameter). It was found that an increase in the degree of substitution of Mg by Zn leads to an increase in the specific surface area and the specific volume of samples. At the same time, the distribution of mesopores has a polymodal character with a predominance of pores having dpor = 3–4 and 25–50 nm. It was found that the substitution of Mg for Zn in the composition of layered double hydroxides leads not only to an increase in the specific capacity of the monomolecular layer of LDH, but also to a stronger interaction of adsorbate (nitrogen) with their surface.

Layered double magnesium–aluminum hydroxide Mg 4 Al 2 (OH) 12 CO 3 ⋅3H 2 O with hydrotalcite structure is obtained by the solid-phase interaction of AlCl 3 ⋅6H 2 O and MgCl 2 ⋅6H 2 O with (NH 4 ) 2 CO 3 . The possibility of the intercalation of the hexathiocyanochromate(III) ion into the interlayer space by anion exchange and reduction during rehydration after heat treatment is investigated. The effect of the process parameters (temperature, solution concentration, duration of phase contact) on the efficiency of the exchange processes is shown. The characteristics of the obtained sample in the sorption of complex hexathiocyanochromate(III) ions are studied. The experimental data are processed using the Freundlich and Langmuir sorption equations. It is determined that the sorption of [Cr(SCN) 6 ] 3– ions is adequately described by both the Langmuir monomolecular adsorption equation and the Freundlich equation. The parameters of the Langmuir adsorption equation are calculated, namely, the capacity of the adsorption monolayer of the synthesized sample to sorb the [Cr(SCN) 6 ] 3– ion and the adsorption equilibrium constant, which are 0.5485 mmol/g and 0.6018 L/mmol, respectively. The data obtained are used to evaluate the sorption treatment of solutions containing the [Cr(SCN) 6 ] 3– ion up to the maximum allowable concentration.

The paper presents the results of studies of the effect of the surface tension of the interstitial fluid on the structural and surface properties (specific surface area and pore volume, pore diameter distribution) of layered magnesium and aluminum double hydroxides (Mg-Al LDH) obtained by the interaction of AlCl 3 ·6H 2 O, MgCl 2 ·6H 2 O and ammonium carbonate. The equations connecting the specific surface area and the specific pore volume of the synthesized Mg-Al LDH samples with the surface tension of the interstitial medium are obtained. It is shown that the substitution of the aqueous medium in the pore space for acetone before drying the synthesized Mg-Al LDH allows to significantly increase the capacity of the adsorption monolayer of products and does not significantly affect the mechanism of the sorption process.

Mg–Al layered hydroxides with the composition Mg 4 Al 2 (OH) 12 CO 3 ⋅3H 2 O are synthesized by mixing crystalline magnesium and aluminum chlorides with ammonium carbonate. The samples are described by XRD, IR, DSC–TG, chemical analysis, and some other methods. It is found that complete recovery of the layered structure occurs upon the interaction of the product of thermal treatment of layered double hydroxides with an aqueous solution.

Data on the mineral, phase, and elemental compositions of a zinc clinker as zinc production waste have been given and the possibility of hydrometallurgical processing using HCl solutions has been investigated. The kinetics of the clinker interacting with HCl solutions of 50–200 g/L in the temperature range of 50–90°C has been studied. The high efficiency of the muriatic acid for the decomposition of both the magnetic fraction and the general clinker sample with the 95–99% extraction of iron and nonferrous metal in solution and the more than 3.5-fold reduction in the clinker mass have been determined. The possibility of processing the filtrate extraction from the decomposition of the clinker by HCl using 100% tributyl phosphate as an extracting agent while obtaining oxide product containing >97% Fe suitable for producing iron-oxide pigment has been shown.

The study is concerned with optimizing of some procedures of titanomagnetite concentrate (TMC) decomposition with a non-aqueous solvent, prepared from n-octanol saturated with hydrochloric acid, by applying the factorial experimental design. The factors, essential for TMC decomposition, were found to be the concentration of hydrochloric acid in extract, process temperature, and the volume ratio of reacting phases. Comparison of the decomposition thermodynamics in aqueous and non-aqueous media has shown that the latter approach required one-fifth as much of activation energy. By employing the solvent decomposition it is possible to eliminate several process stages and diminish the consumption of both the process time, power, and mineral acid.

The main physicochemical properties of the extracts, such as density, viscosity, and conductivity, as well as the mutual solubility of the phases in the ROH-H2O and ROH-H2O-H3PO4 extraction systems, where ROH (R = C5–C10) stands for higher monofunctional aliphatic alcohols with a different length and structure of the hydrocarbon radical, have been studied in water and aqueous solutions containing phosphoric acid. The properties correlate with the length and structure of the hydrocarbon chain in the aliphatic alcohols, as well as with the concentration of mineral acid in the extracts.

Изучены основные физико-химические свойства (плотность, вязкость и удельная электропроводность) экстрактов и взаимная растворимость фаз в экстракционных системах с высокомолекулярными одноатомными алифатическими спиртами ROH (R = C5 C10) с различной длиной и структурой углеводородного радикала в воде и водных растворах, содержащих фосфорную кислоту: ROH H2O и ROH H2O H3PO4. Установлена корреляция свойств с длиной и строением углеводородного радикала алифатического спирта и концентрацией минеральной кислоты в экстрактах.

The paper considers vanadium (V) distribution during its extraction from hydrochloric acid solutions by phosphorus-containing extracting agents. It has been shown that vanadium can be concentrated in one of the phases during the extraction processing of filtrates after titanomagnetite decomposition with HCl solutions.

The interaction of Khibins titanomagnetite concentrate (TMC) with hydrochloric acid solutions has been investigated. The decomposition of TMC in the HCl solutions has been optimized using factorial experimental design. The main factors in the efficiency of TMC decomposition with hydrochloric acid and in metal extraction into the filtrate are the HCl concentration, HCl input, processing temperature, and reaction mixture stirring time. By varying the decomposition conditions, it is possible to control the selectivity of the process: in TMC decomposition at a high temperature and a high acid concentration and input (t = 95°C, C HCl = 320−340 g/L, TMC (S): HCl (L) = 1: 10, τ = 4 h), the metals pass collectively into the solution with a large recovery factor (93–95%); at smaller values of the above parameters (t = 50−80°C, C HCl = 200–220 g/L, S: L = 1: 6–7, τ = 2 h), TMC decomposition proceeds more selectively towards iron and vanadium leaching into the solution with the minimum possible leaching of titanium (<15%).

The mutual solubility of components in the extraction system HCl-monohydric aliphatic alcohol ROH (R = C5–C10)-H2O at 20°C was studied.

The decomposition of TMC with hydrochloric acid solutions (15–25% HCl) at the boiling point of the reaction mixture and atmospheric pressure has been investigated. The processing conditions have been determined for efficient recovery of titanium (up to 99.3%) as photocatalytically active anatase and for extracting Fe (up to 99.6%) and V (98.8%) into the leaching solution. Subsequent treatment of the leach liquor with aqueous ammonia affords 99.3 wt % Fe 2 O 3 and an iron-vanadium product containing 3.2 wt % V 2 O 5 .