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.     

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.     

Sorptive technology of extracting nonferrous metals from pit water

Mine waters containing dangerous heavy metals are a significant environmental problem. Traditional methods of purification do not make it possible to completely eliminate impurities. In this work, the results of sorptive studies into the recovery of nonferrous metals from the mine water of a copper-zinc deposit are presented. Laboratory experiments for the selection of the optimal material and extended tests for the selected sample of a Lewatit TP 207 ion exchanger were performed. The possibilities of using ion exchangers to eliminate ions of heavy nonferrous metals are presented, and their capacity and selectivity indices relative to the sorption of nonferrous metals are determined.     

Comparative study of chelating ion exchange resins for the recovery of nickel and cobalt from laterite leach tailings

Commercially available chelating resins with the iminodiacetate functional group have been evaluated for their suitability for the adsorption of nickel and other metal ions by a resin-in-pulp process from the tailings of a pressure acid leach process for nickel laterites. The Amberlite IRC 748 and TP 207 MonoPlus resins were found to be the most suitable in terms of loading capacity for nickel and kinetics of adsorption. The resin with the highest nominal capacity was observed to adsorb less nickel as a result of the adsorption of greater amounts of the impurity ions. The equilibrium loading for nickel on the preferred resin was found to be similar from the ammonium and protonated form of the resin although the kinetics of adsorption is greater when the resin is initially in the ammonium form. A study of the kinetics of the loading of nickel and cobalt from pulp has shown that the rate can be described in terms of a first-order approach to equilibrium. The optimum pH for adsorption was found to be in the range 4 to 5 as this pH is high enough to maximize the adsorption of nickel and cobalt while preventing precipitation of nickel and cobalt as hydroxides from the pulp. A method for minimizing the competition from more strongly loaded ions such as iron(III) and chromium(III) which are present in the pulp was also developed in the initial laboratory phase of the study.     

The adsorption extraction of nickel(II) ions from aqueous solutions

Processes of the sorption of nickel(II) ions from aqueous solutions on carbon adsorbents synthesized based on fossil coals are investigated. The maximal adsorption is observed in a neutral medium. Adsorption isotherms are obtained under static conditions in various temperature modes. It is shown that they are described satisfactorily by the Langmuir isotherm. The decrease in the value of adsorption as the temperature increases indicates that the process is exothermic. The kinetics of the process is investigated and thermodynamic parameters of adsorption are determined.     

Recovery of nickel from Orimulsion fly ash by iminodiacetic acid chelating resin

Macroporous resins containing imminodiacetic acid (IDA) groups (Lewatit TP-207, Purolite S-930 and Amberlite IRC-748) were studied under dynamic conditions for uptake of nickel ions from the sulphate solution at pH 4 deriving from preliminary acid leaching of Orimulsion fly ash and subsequent vanadium recovery and impurities removal stages. The effects of temperature and ionic medium on the Ni adsorption were investigated.     

Use of Phosphate Rock for the Removal of Ni2+ from Aqueous Solutions: Kinetic and Thermodynamics Studies

A study was carried out in batch conditions to examine the removal of nickel ions from an aqueous solution by phosphate rock. The effect of different sorption parameters, such as initial metal concentration, equilibration time, solution pH, and temperature on the amount of Ni2+ sorbed was studied and discussed. The sorption process followed pseudo-second-order kinetics with necessary time of 2?h to reach equilibrium. The maximum removal obtained is at initial pH around 8. Nickel uptake was quantitatively evaluated using the Langmuir and Dubinin–Kaganer–Radushkevich model. The Langmuir adsorption isotherm constant corresponding to adsorption capacity, Q0, was found to be 7.63?mg/g. The possibility of metal recovery was investigated using several eluting agents. The desorbed amount of nickel decreased continuously with increasing pH, and increased with increasing Ca2+ concentration in leaching solution.     

Ecological Evaluation of Bacterial Leaching of Arsenous Gold Concentrates

Phase changes of arsenic in the process of biohydrometallurgical treatment of refractory arsenous gold concentrates, including bacterial leaching, sorption from cyanide solution using active carbons, and purification of sorption tailings by calcium hypochlorite were studied by physico-chemical methods.

It was found by X-ray crystal and X-ray spectrum analyses that in tailings from the process of purification of cyanide pulps, arsenic occurs mainly in the form of amorphous species of ferric sulphate arsenates, their composition depending on molar ratios of iron and arsenic. The presence of crystal phases of arsenic, mainly as scorodite, is observed. According to the results of sample surface study by X-ray photoelectronic spectroscopy, the base of amorphous species is presumed to be hydrated. Acid ferric arsenates and arsenic (III) composites were found in the cakes of bacterial leaching.

The washout of arsenic from the products of biohydrometallurgical treatment was studied. Experiments revealed that the migration of arsenic from the solid phase depends on molar ratios of iron and arsenic. It may be possible to reduce arsenic concentration in the liquid phase to 0.05 mg/1 by temperature treatment of arsenic products. The obtained results demonstrate the possibility to create an ecological acceptable technology for the treatment of refractory arsenous gold concentrates.     

The nature of active centers during sorption of cyanide complexes of noble metals on carbon sorbents

Carbon sorbents obtained from cannel coal of the Leninsk-Kuznetskii coal field are investigated by EPR spectroscopy. It is established that the sorption capacity of activated carbons by silver increases as the concentration of paramagnetic centers increases, and both parameters are peaked at the activation temperature of ～900°C. As the sorption surface, the polyconjugated aromatic system with a delocalized unpaired electron is suggested.     

Sorption from slurries—A promising method in the processing of rare earth elements

The article presents the results of sorptive extraction of rare-earth elements (REE) from the solutions and slurries of complex salt compositions using sulfocationites and carboxyl cationites with a predominant content of the latter on laboratory and pilot scales. Upon REE sorption from hydrate slurry on KM-2p carboxyl cationite, the REE extraction rate of at least 98% has been achieved, and the following factors of ΣREE purification from impurities have been obtained: K _REE/Al = 1.7, K _REE/Th = 2.3, K _REE/Ca ≈ 20, K _REE/Zr = 15, K _REE/Fe ≈ 40, and K _REE/P,F ≈ 90. It is demonstrated that the REE capacity of cationite SG-1m is higher than that of cationite KM-2p by 10%; moreover, the content of thorium on KM-2p cationite is lower by 2.5 times and that of zirconium by 6 times. After the recovery of saturated cationites by 1.5–2.0 M HNO₃ solutions, strippants have been extracted with a REE concentration of 15–20 g/L. The factors of REE purification from impurities upon desorption are as follows: K _REE/Al = 2.5, K _REE/Th = 0.5, K _REE/Ca = 5.3, K _REE/Zr = 5.6, and K _REE/Fe = 0.8. The REE recovery rate is ≥99%.     

Sorption extraction of cobalt ions from nitrate media by the iminodiacetate chelating resins Lewatit TR-207 and TR-260

Cobalt-ion sorption from nitrate media by the macroporous chelating resins Lewatit TR-207 and TR-260, which contain active functional groups based on iminodiacetic acid, is studied. Both resins are shown to sorb cobalt from nitrate solutions rather efficiently at pH 1.5–2.0, and the degree of cobalt extraction reaches ～100% for a solid to liquid ratio of ≥0.3. Under optimal conditions, the cobalt capacity of the resins is ～160 mg/g. The system under study is equilibrated within 240 min, and >70% Co is extracted during the first hour of sorption. On heating to 40–40°C, cobalt sorption enhances; however, upon further heating to 50–52°C, the extraction of cobalt decreases, which is probably caused by thermal destruction of the resin. The estimated change in the enthalpy of cobalt sorption in the temperature range 21–41°C is about +84 kJ/mol. The results obtained are employed to test the cobalt sorption under dynamic conditions in a laboratory column packed with Lewatit TR-207 resin in the H⁺ form (the working volume of the column is 100 ml) using the real mother liquor (24.5 mg Co/l) of cobalt oxalate precipitation. Quantitative desorption of cobalt is conducted with a solution of HNO₃ (400 g/l). During dynamic tests, about nine specific volumes of the initial mother liquor are passed through the column. After this, the cobalt content in the purified solution is lower than 0.4–0.5 mg/l; i.e., the total degree of cobalt extraction is >98%. In the desorption solution, the cobalt concentration increases to ～0.3 g/l, which corresponds to a more than tenfold degree of cobalt enrichment. Thus, the resins under study can be recommended for the extraction of cobalt microamounts (20–50 mg/l) from foul and reused waters.     

Properties of Ni–Cr–Al Alloys Obtained by a Powder Metallurgy Method

Alloys of practically 100% density were formed by hot pressing mixtures of nickel, chromium and aluminum powders. The principal phases formed are solid solutions based on chromium, on nickel, and also the intermetallic NiAl. These correspond to phases in the phase equilibrium diagram of theNi Cr Al system. The strength and wear resistance of the alloys are determined by the ratio of phase components.     

Investigation into the influence of hydroxyl ions on the mechanism of interaction between cyanic compounds of gold and an active surface of carbon sorbents

In the framework of methods of quantum-chemical simulation, the possible participation of hydroxyl groups in the sorption and desorption of aurocyanides on active surfaces of aromatic characters is investigated. It is shown that the saturation of an active surface with hydroxyl groups leads to a considerable lowering of the barriers of sorption and desorption. This effect can be used to intensify the desorption of gold and silver from active carbons.     

Water adsorption in the organic phase for the D2EHPA–kerosene/water and aqueous Zn2+, Co2+, Ni2+ sulphate systems

Water adsorption by bis-2-ethylhexyl phosphoric acid (D2EHPA) during the extraction of zinc, cobalt and nickel using a D2EHPA–kerosene/H₂O mixture is investigated. Based on the experimental results, about 1 mol of water is adsorbed by 2 mol of D2EHPA (which exists in the form of a dimer), irrespective of the pH. Water adsorption decreases with presence of zinc, cobalt and nickel. The stoichiometric coefficients of D2EHPA in water adsorption reactions are determined with and without zinc, cobalt and nickel by applying the slope-analysis method. It is experimentally confirmed that 1.0, 1.8 and 1.2 mol of adsorbed water will be rejected from the organic phase when zinc, cobalt and nickel are extracted, respectively. It is predicted that a similar organic complex is formed by D2EHPA and water during the extraction of different metallic ions.     

Mechanically activated reduction of nickel oxide with graphite

The reduction of nickel oxide with graphite during ball milling at both ambient and elevated temperatures was investigated using X-ray diffraction (XRD), simultaneous thermogravimetry and differential thermal analysis (TG/DTA), and electron microscopy. It was found that milling at ambient temperature did not result in the reduction of nickel oxide to nickel. However, milling significantly reduced the critical reaction temperature for the reduction, from 1350 K for the unmilled sample to ∼650 K for samples milled for 12 hours or longer. This reduction in reaction temperature is rationalized in terms of the microstructural refinement observed in the milled samples. The reduction of nickel oxide to nickel was observed to occur at elevated temperatures during milling. The thermodynamics and kinetics of the reduction reaction are discussed.     

硝酸铵-丁二酮肟-百里酚酞体系分离富集镍

建立了一种以微晶百里酚酞作吸附剂分离富集镍的新方法。探讨了分离富集镍的行为及其与常见离子定量分离的条件, 详细讨论了Ni²⁺的富集机理。结果表明, 控制pH 8.0, 在硝酸铵-丁二酮肟-百里酚酞体系中, 镍与丁二酮肟(DMG)形成的螯合物沉淀[Ni(DMG)₂]可被定量吸附至微晶百里酚酞表面上, 形成界面清晰的液-固两相, 而锰、铜、镉、铝、锌等不被吸附, 实现了镍与这些金属离子的定量分离, 据此建立了分离富集镍的新方法。方法成功用于合成水样中微量镍的定量分离, 富集率为95.9%~106.5%。     

Gold recovery from non-metallic secondary raw materials by leaching with thiourea and adsorption on ion exchangers

Elemental gold on non-metallic secondary raw materials is easy to dissolve by leaching with sulphuric acid solutions of thiourea in the presence of an oxidant such as iron(III) sulphate or hydrogen peroxide. Leaching time is highly dependent upon oxidant concentration and the thickness of the gold coating. The gold goes into solution as the Au[SC(NH₂)₂]_2⁺ complex and can be removed almost completely using cationites, the gold residues being not greater than 6 μM. The gold-free leaching solution may be reused for leaching; the completely-loaded cationite resin (with a gold content of about 30–60 g/l) is burnt to recover the gold.A study of the adsorption of Au and Fe by cationites indicates that the adsorption of gold takes place purely by means of an ion-exchange mechanism, the bond of the gold complex being considerably stronger than that of the iron compounds.     

Properties of fine metal powders produced by the formate pyrolysis method

Conclusions Optimum parameters have been determined for the processes of preparation of fine copper, nickel, and cobalt powders by the pyrolysis of formates in a protective argon atmosphere. Use of fine copper, nickel, and cobalt powders prepared by this method as interlayers in the vacuum diffusion welding of copper and steel parts enables the temperature of the process to be substantially lowered. Copper coatings can be applied to metallic and nonmetallic materials in the course of the pyrolysis of copper formate.Translated from Poroshkovaya Metallurgiya, No. 3(207), pp. 1–6, March, 1980.     

Tantalum sorption from chloride-fluoride solutions by anionites

The calculated and experimental data on sorption of tantalum ions from chloride-fluoride solutions by anionites of various classes and structures are considered and discussed. Based on the calculations carried out, it is shown that, in chloride-fluoride solutions, tantalum forms a whole series of complex ions, namely, chloride, fluoride, hydroxy, and mixed chloride-fluoride and hydroxychloride complex ions. The equilibrium of tantalum ions during their sorption from chloride solutions is investigated. The behavior of the tantalum ions during the sorption from hydrochloric acid solutions over a wide range of its concentration is interpreted from the viewpoint of the ionic state of the metal in the solution as well as the structure and functional features of ion exchangers. The conclusions made on the sorption chemistry are confirmed by the data of the IR spectroscopy investigations.     

中间层成分对TP304H不锈钢瞬间液相连接的影响

 采用镍基、铁镍基和铁基3种中间层合金进行了TP304H不锈钢的瞬间液相(TLP)连接试验,利用电子探针和能谱分析了中间层成分对接头组织和成分的影响。结果表明,镍基接头组织为固溶体,接头区出现了跨界面晶粒。虽然接头拉伸断裂于焊缝处,但强度、塑性已达到母材水平。铁镍基接头组织与母材组织不同,元素扩散差,焊缝界限清晰,接头性能低。铁基接头组织与母材组织相同,成分连续均匀分布,实现了真正的TLP连接。挂管试验结果表明,铁基接头不仅具有很好的强度和塑性,而且接头抗腐蚀性能好,可满足实际工业应用。