Pyrazole-containing polymer sorbents for recovery of gold and silver from cyanic solutions

The results of an investigation into imparting hydrophilic properties to pyrazole-containing sorbents in cyanic media and increasing their capacitive characteristics with respect to noble metals are presented. It is established that adding up to 30% (relative to 3(5)-methylpyrazole) of triethanolamine or trimethylamine into the resin matrix exerts a positive effect on the capacitive characteristics of sorbents based on styrene divinylbenzene and 3(5)-methylpyrazole. It is shown that the introduction of deprotonating additives into the reaction mixture when synthesizing a sorbent of SDP-d grade makes it possible to increase its sorption capacity by 20–25% in regards to silver for its recovery from the AgNO₃ solution (the number of functional groups of resin correspondingly increases). A sorbent of SDDP-d grade of microporous structure with an increased content of 3(5)-methylpyrazole groups is obtained. The synthesized samples of resins are compared in regards to sorption from cyanic solutions on the background of high Cu and Zn contents in starting solutions. The sorption isotherms of Au, Ag, Cu, and Zn on the SDDP-d resin from cyanic solutions are recorded, and the sorption ability series Au > Ag > Zn > Cu is determined.     

Applicability of hydrogarnet technology for complex processing of Indian condalites

The results for one variant of processing high-silicon aluminum raw materials—Indian condalites—are given. It is established that the main impurity (silicon dioxide) can be removed in a sequential variant of Bayer hydrochemistry with the processing of red slime in high-module solutions by hydrogarnet technology. The formation conditions of ferrous hydrogarnet of the composition 3CaO · Fe₂O₃ · 2SiO₂ as a monomineral (prevailing) phase, such as a temperature of 230–250°C, an alkali concentration no lower than 200 g/dm³, and the introduction of the active form of iron oxide, are determined.     

Sorption concentration of thorium from solutions during complex processing and deactivation of scandium-containing technogeneous raw materials

The results of investigations into the selective sorption recovery of hydrolyzed thorium ions on macroporous sulfonic cationites from scandium-containing solutions forming during the complex processing of multicomponent polymetallic production wastes are generalized and systematized. It is shown that the efficiency and selectivity of the process can be substantially increased with the use of a KU-23 macroporous cationite and anionite in the OH⁻ form for sorption, as well as with the preliminary introduction of magnesium and calcium chlorides into Sc-Th-containing solutions in amounts of 50–150 g/dm³. Based on our experiments and previous investigations, a production flow chart for the complex processing, deactivation, and neutralization of production wastes with the localization of thorium and its decay products, as well as the acquisition of commercial products of scandium oxide, inorganic pigments, sorbents, catalysts, etc., is developed and suggested for practical implementation.     

The solubility of hydrogen in liquid binary Al-Li alloys

The solubility of hydrogen in liquid binary aluminum alloys with 1, 2, and 3 wt pct lithium has been determined for the temperature range of 913 to 1073 K and pressure 5.3 × 10⁴ to 10.7 × 10⁴ Pa, using an appropriate version of Sieverts’ method. The results fit the Van’t Hoff isobar and Sieverts’ isotherm and the solubility,S, is given by: Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2113/T/k + 2.568 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2797/T/k + 3.329 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2889/T/k + 3.508 whereS° is a standard value of solubility equal to 1 cm³ of diatomic hydrogen measured at 273 K and 101,325 Pa per 100 g of metal, andP° is a standard pressure equal to 101,325 Pa. Added lithium progressively increases the solubility of hydrogen in liquid aluminum, due more to its effect on the entropy of solution of hydrogen, through its influence on the liquid metal structure than to an increase in the solute hydrogen atom binding enthalpy.     

The solubility of hydrogen in liquid binary Al-Li alloys

The solubility of hydrogen in liquid binary aluminum alloys with 1, 2, and 3 wt pct lithium has been determined for the temperature range of 913 to 1073 K and pressure 5.3 × 10⁴ to 10.7 × 10⁴ Pa, using an appropriate version of Sieverts’ method. The results fit the Van’t Hoff isobar and Sieverts’ isotherm and the solubility,S, is given by: Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2113/T/k + 2.568 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2797/T/k + 3.329 Al-1 pct Li: log(S/S°) − 1/2 log(P/P°) = −2889/T/k + 3.508 whereS° is a standard value of solubility equal to 1 cm³ of diatomic hydrogen measured at 273 K and 101,325 Pa per 100 g of metal, andP° is a standard pressure equal to 101,325 Pa. Added lithium progressively increases the solubility of hydrogen in liquid aluminum, due more to its effect on the entropy of solution of hydrogen, through its influence on the liquid metal structure than to an increase in the solute hydrogen atom binding enthalpy.     

Sorption of Rhenium from Sulfuric Acid Solutions with Trialkylamine-Containing Impregnates

The sorption of rhenium (VII) from sulfuric acid solutions with impregnates based on macroporous polymeric carriers (copolymers of styrene with divinylbenzene, a weakly acidic cation-exchange resin), which contain technical trialkylamine (TAA), is investigated in batch conditions. Equilibrium and kinetic characteristics of sorption of rhenium with the K-TAA impregnate based on macroporous cationite having the best capacitive characteristics with respect to rhenium are found. The maximal distribution coefficient of rhenium in the K-TAA impregnate is observed during sorption from solutions with pH 2. The sorption isotherm of rhenium is described by the Langmuir equation with constant K = 29 ± 2 mL/g. Integrated kinetic curves of sorption are found by the method of a limited solution volume at various temperatures and effective diffusion coefficients of rhenium in an impregnate, which are equal to 3.8 × 10^–11 (295 K) and 1.3 × 10^–10 (308 K) m²/s, are calculated allowing to the half-transformation time. Processing the kinetic data by linearization according to equations of models of the pseudo-first, pseudo-second, internal diffusion, and Elovich showed that kinetic curves are described with the highest degree of correlation by pseudo-second-order equations with rate constants 0.00056 (295 K) and 0.00059 (308 K) g mg^–1 min^–1. The apparent activation energy of sorption of rhenium of 39 ± 2 kJ/mol is calculated according to the Arrhenius equation. The K-TAA impregnate is approved for the sorption of rhenium from the eluate formed during the desorption of rhenium from the weakly basic anion-exchange resin (Purolite A170) preliminarily saturated with rhenium from a productive leaching solution of processing products of rhenium-containing off-balance copper-sulfide ores with a complex composition.     

Investigation of behavior of elemental sulfur in H<Subscript>2</Subscript>O-OH<Superscript>−</Superscript>-CN<Superscript>−</Superscript> solutions

The processes of dissolution of elemental sulfur in S-H₂O-OH⁻-CN⁻ systems are investigated. These processes simulate the technological processes of cyanidation and the sorption leaching of Au from the biocakes of gold recovery plants in the range of concentrations of the CN⁻ ions of 0–0.02 mol/dm³ and the range of concentrations of the OH⁻ ions of 0–0.1 mol/dm³. Using the simple-lattice planning method of the experiment, mathematical models and “solvent composition-amount of dissolved sulfur” diagrams are constructed for temperatures of 20, 30, and 40°C. It is established that, at t = 20°C, the strongest effect on the solubility of S in the mentioned solvents exerts the concentration of cyanides, while, at t = 30 and 40°C, the larger contribution to an increase in transfer of S into the solution gives the OH⁻ content. The role of hydrolysis that the CN⁻ ion plays in increasing the solubility of sulfur in the studied systems is shown.     

Surface Tension of Liquid Alkali,Alkaline, and Main Group Metals: Theoretical Treatment and Relationship Investigations

An improved theoretical method for calculating the surface tension of liquid metals is proposed. A recently derived equation that allows an accurate estimate of surface tension to be made for the large number of elements, based on statistical thermodynamics, is used for a means of calculating reliable values for the surface tension of pure liquid alkali, alkaline earth, and main group metals at the melting point, In order to increase the validity of the model, the surface tension of liquid lithium was calculated in the temperature range 454 K to 1300 K (181 °C to 1027 °C), where the calculated surface tension values follow a straight line behavior given by γ = 441 – 0.15 (T-Tm) (mJ m⁻²). The calculated surface excess entropy of liquid Li (–dγ/dT) was found to be 0.15 mJ m⁻² K⁻¹, which agrees well with the reported experimental value (0.147 mJ/m² K). Moreover, the relations of the calculated surface tension of alkali metals to atomic radius, heat of fusion, and specific heat capacity are described. The results are in excellent agreement with the existing experimental data.     

Effect of heat treatment on the dispersity of Sn(IV)—Sb—O powders and the porosity of thick-film gas sensors based on them

A study is made of how the granulometric composition and porosity of powders of solid solutions in the system Sn(IV)−Sb−O is affected by the conditions of precipitation of mixtures of tin hydroxide and antimony hydroxide and the heat-treatment temperature. Powders of tin and antimony hydroxides have a microporous structure and a high (≥200 m ²/g) specific surface. Heat treatment above 870 K forms Sn_1−xSb_xO₂ solid solutions, this being accompanied by an increase in the size of the particles and transformation of the microporous structure to a mesoporous structure. An increase in the antimony content of the solid solutions helps form finer powders. A examination is made of the parameters of the pore structure of bulk specimens of semiconductor gas sensors obtained by heat-treating mixtures of powders of solid solutions and ultrafine clay. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(407), pp. 111–116, May–June, 1999.     

Modification of CaO by Organic Alumina Precursor for Enhancing Cyclic Capture of CO2 Greenhouse Gas

The modification of CaO sorbent with organic alumina precursor to enhance the sorption capacity during cyclic capture is demonstrated in this study. The results indicate that during the 10?min sorption time for each cycle, the CO2 sorption capacity of original CaO sorbent is significantly decreased from 0.27 to 0.19 and 0.12?g CO2/g sorbent after 5 and 60?cycles, respectively. On the other hand, the organic alumina modified CaO has a fresh capacity of 0.22?g CO2/g sorbent, it increases to 0.24?g CO2/g sorbent after 5?cycles, and then decreases to around 0.15?g CO2/g sorbent after 60?cycles. When increasing the sorption time to 60?min at the 66th cycle, the sorption capacity of original CaO is 0.2, whereas it is 0.26?g CO2/g sorbent for organic alumina modified CaO. The results demonstrate that by adding only 5% by weight of Ca12Al14O33 species into the CaO sorbent, the CO2 sorption capacity can be enhanced up to ～ 27% by weight.     

Recovery of copper from solutions by highly dispersed modified aluminum silicates

Sorption of copper ions from model solutions (1–100 mg/dm³ Cu) at pH = 5.5–9.5 and from wastewater (of the composition, mg/dm³: 0.2–0.4 Cu, 0.2–0.3 Zn, 0.3–0.4 Ni, 0.3–0.5 Fe, 0.6–0.9 Pb, 1.8 As, 0.2 Mn, 3.2 Mg) at pH = 8.5 on modified montmorillonite of the Zyryanovskoe deposit in the Naform is investigated in comparison with the known liming method. The considerable sorption capacity of highly dispersed alumosilicates (~3.0 mg-eq/g) makes it possible to acquire a precipitate with a high content of ions of heavy nonferrous metals from the precipitate and purified water with residual concentrations of metals (Cu < 0.01 mg/dm³) corresponding to discharge norms into the surrounding medium.     

Obtaining molybdenum powder by metallothermy of its compounds in a sodium chloride melt

The reduction conditions of the oxygen compound of molybdenum to metal powder using aluminum and magnesium in a sodium chloride solution are investigated. A thermodynamic evaluation of the reduction reactions is given. It is found that, in order to end up with a 95–97% yield of the powders, an excess of ∼30% of the reducing agent with respect to the calculated one is necessary. In this case, the content of impurity elements does not exceed 3%. The influence of obtaining conditions on the granulometric characteristics of the powder is established. It is shown that powders with a larger specific surface (64.4 × 10⁵ m⁻¹) are formed with the use of aluminum in concentrated solutions of the starting compound in the NaCl melt.     

Sorption technology of recovery of indium from solutions of zinc production

Sorption of indium ions from polycomponent solutions with preliminarily reduced iron(III), which contain, g/dm³, 0.084 In³⁺, 6.2 Fe²⁺, 67.0 Zn²⁺, and 19.6 H₂SO₄, on the Metosol reagent, is investigated in the dynamic mode. The Metosol reagent represents montmorillonite of composition (Na,Ca)_0.3(Al,Mg)₂Si₄O₁₀(OH)₂(H₂O) _n , modified with di(2-ethylhexyl)phosphoric acid. The absorption dynamics of ions by it is investigated by frontal chromatography. The values of working (DEC) and total (CDEC) dynamic exchange capacities of the mineral sorbent are determined depending on the eluent specific passing rate and temperature. The main parameters of the sorption technology of the selective recovery of indium from process solutions of the zinc production on the Metosol reagent in columns followed by the desorption of metal with the hydrochloric acid solution (1: 1) are substantiated and calculated.     

On the decomposition of solid solutions of magnesium in aluminum

A nonequilibrium version of measuring the electromotive force during a continuous decrease in the temperature at a rate of 5–7 °C/min is used to study the thermodynamic properties of solid solutions of magnesium in aluminum. The studies show that the abrupt change in the potential of an alloy containing 20–30 mol % Mg at 370–380°C reliably correlates with the decomposition of the solid solution formed at 450°C.     

Alkali-acidic method of processing of aluminum chip with obtaining aluminum hydroxychloride

The technology of obtaining a coagulant—aluminum hydroxychloride—from aluminum chip by the alkali-acidic method is investigated. In this method, the largest part of impurities present in the starting raw material is separated during the filtration of the aluminate solution. The reagent for the removal of oils, petroleum derivatives, and lubricoolant from the surface of aluminum chip is selected. A new principal process flow chart for obtaining the coagulant by the alkali-acidic method is suggested. The flow chart allows one to obtain a coagulant with a minimal content of impurities with the simultaneous liberation of chlorine for water disinfection and sodium hydroxide for the alkali dissolution of aluminum chip.     

Sorption of Scandium from Sulfuric–Chloride Solutions by Activated Carbons

Sorption of scandium by activated carbons of VSK, DAS, and PFT brands of different origin (coconut shell, anthracite, and thermosetting-plastic waste, respectively) from sulfuric–chloride solutions (pH 2) simulating the composition of solutions for the underground leaching of complex ores is studied in batch conditions. It is established that the sorption of scandium by carbons of DAS and VSK brands proceeds with the highest distribution coefficients (133 and 45.8 cm3/g, respectively). Herewith, the sorption of scandium by DAS carbon is also characterized by a large volume coefficient (116 $${{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} \mathord{\left/ {\vphantom {{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}} \right. \kern-0em} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}$$). Sorption isotherms of scandium by these carbons are linear and described by the Henry equation with constants 133 ± 21 and 46 ± 7 cm3/g, respectively. The integral kinetic curves of sorption of scandium are found by the method of the limited volume of the solution, and their linearization according to the kinetic models of the pseudo-first and pseudo-second order, the Elovich model, and the Weber–Morris intraparticle diffusion model evidences that the sorption kinetics of scandium by VSK carbon with a higher correlation coefficient (0.999) is described using the pseudo-second-order model. Processing the kinetic data on the sorption of scandium by DAS carbon showed that, when using all models, the correlation coefficient is low (<0.939) and the highest value is observed when applying the intraparticle diffusion model. It is assumed that the sorption of scandium occurs in the mixed diffusion region. The possibility of eluting scandium from VSK and DAS carbons by the sodium carbonate solution (10%) is studied under the batch conditions and the degree of desorption of scandium for two elution steps is 84.0 and 90.4%, respectively.     

Sorption of lanthanide ions on biochar composites

Sorption of lanthanum(Ⅲ), cerium(Ⅲ) and neodymium(Ⅲ) ions from the aqueous solutions of mixtures through adsorption on the biochar composites was investigated as a function of sorbent mass, pH, phase contact time and initial concentration of solutions at 295 K. The maximum removal of lanthanide ions takes place under the following conditions: 0.1 g of sorbent mass, pH 4 and 360 min contact time for all studied initial concentrations of solutions. Kinetics of La(Ⅲ), Ce(Ⅲ) and Nd(Ⅲ) ions sorption proceeded by a fast initial uptake reached equilibrium. This process was modelled by means of the pseudo first order, pseudo second order, intraparticle diffusion and Elovich models. The desorption of three lanthanide ions by nitric, hydrochloric and sulfuric acids at a concentration of 1 mol/L from biochar composites was also studied. In order to investigate the sorption mechanism FTIR, XRD and XPS analyses were performed after sorption of ions from the mixture.     

Anion structural effects on interaction of rare earth element ions with Dowex 50W X8 cation exchange resin

The effect of the anion in the original rare earth element(REE) solution on the reversible ion exchange of Ce nitrate and Ce sulfate with the Dowex 50 W X8 was investigated using attenuated total reflection infrared(ATR-IR) spectroscopy, continuous flow reactor studies coupled with inductively coupled plasma mass spectroscopy(ICP-MS), and density functional theory(DFT). The simulated IR spectrum at the DFT B3 LYP/6-31 G(d) level was compared to the experimental results to characterize the IR spectrum, molecular interactions, and bonding of the ion exchanged species. The continuous liquid flow reactor studies show a capacity of 0.72 mmol/g sorbent for the Ce nitrateand 0.96 mmol/g sorbent for the Ce sulfate with the Dowex 50 W X8. The flow reactor studies reveal the type of solute anion(SO_4~((2-)) or NO_3~((-))) associated with the REE during cation exchange significantly affects the sorption capacity of the Dowex 50 W X8 ion exchange resin. The calculated REE binding energy(BE) and the DFT optimized structures suggest that the differences in sorption capacity is the result of the formation of different types of partially ionexchanged Ce_2~((3+))2 SO_4~((2-)) and Ce~((3+)) 3 NO_3~((-)). These results suggest that the solute anion affects the equilibrium constants of the Dowex resin by the formation of a charged layer capable of retaining the counterion. Modifying the sulfonic acid site(H+) in the Dowex 50 W X8 with the NH_4~+ counterion does not affect the sorption capacity and retention times of the Ce nitrate and Ce sulfate species. These results suggest that the counterions and co-ions having a finite size, may limit access to the Dowex sulfonate active site where the type of REE cation as a nitrate or sulfate in solution may significantly modify the sorption capacity of the ion exchange resin. Similar results are obtained during sorption with nitrates and sulfates of Sm and Yb.     

Sorption behaviour and mechanism of ytterbium(III) on imino-diacetic acid resin

The sorption behaviour and mechanism of a novel chelate resin, imino-diacetic acid resin (IDAAR), for Yb(III) has been investigated in HAc–NaAc medium. The sorption of Yb(III) obeys the Freundlich isotherm. Optimum sorption for Yb(III) on IDAAR is at pH 5.13 and the statically saturated sorption capacity is 187 mg/g resin at 298 K. Yb(III) can be eluted using 1~2 mol L^− 1 HCl and the resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k₂₉₈ = 1.57 × 10^− 5 s^− 1; the apparent activation energy is 13.8 kJ mol^− 1 and the enthalpy change ΔH of IDAAR for Yb(III) is 29.8 kJ mol^− 1. The sorption mechanism of IDAAR for Yb(III) was examined by using chemical methods and IR spectrometry. The molar coordination ratio of the functional group of IDAAR to Yb(III) is 3:1 with the coordination compound formed between oxygen atoms in the functional group of IDAAR and Yb(III).     

Intensification of Gold Sorption by Anion Exchange Resins

Gold extraction technology based on anion exchange resins with mixed basicity, commonly used in former soviet countries, includes a complicated and expensive process of resin regeneration and gold stripping by thiocarbamide solution. Satisfactory sorption properties of weak base anion exchange resin at pH 6–8 and low cost of metal stripping by sodium hydroxide solution have aroused considerable interest in these resins as perspective means of gold extraction from cyanide pulps on a large scale. However, the possibility of industrial use of weak base anion exchange resins is hindered by their extremely low sorption activity at pH 10.5 and the formation and release of HCN in the pulp at pH 6–8.

The development of weak-based anion exchange resins which permits efficient gold sorption at pH 10.5 has already been described in literature. A special procedure for treating cyanide pulps has been devised in ?Irgiredmet”. It allows a sigificant rise of gold distribution coefficient between anion exchange resins and liquid phase.

Studies including counter-current tests of gold sorption by anion exchange resins of mixed and weak basicity from cyanide solutions and pulps treated accordingly were carried out. It was found that the gold capacity of mixed base resins has risen by 2–3 times, and the resin flowrate and reagent consumption during its regeneration and gold stripping by thiocarbamide solution have decreased proportionally. After special treatment the gold capacity of weak base resins in solutions and pulps is 3–6 times greater than in nontreated solutions and pulps, which indicated that the sorption capacity of resins is used to the full extent. Introduction of special treatment of cyanide pulp into existing technology makes possible an efficient industrial use of commercially available weak base anion exchange resins for gold recovery.