On the basis of anion-exchange equilibrium data in hydrochloric acid solutions, elements were classified into three groups by their separation from copper. The Cu(I) chloro-complex species are fixed in the resin and the non-absorbed (Class I) impurities are eliminated. This is followed by in situ oxidation and elution of copper in the Cu(II) state, leaving the strongly absorbed (Class II) elements behind in the column. Impurities of varying absorbabilities (Class III) could also be separated by an appropriate elution technique. The experimental elution curves of the characteristic elements proved that the method is capable of eliminating practically all the impurities from copper. Application of the combined anion-exchange purification procedure could provide a relative degree of purification of 1000, removing more than 99.9% of the impurities, while the copper yield was kept above 70%.
. The potentiodynamic experiments of the nickel effects on the zinc electrodeposition have been done to understand the impact of Ni impurities on the electrowinning of Zn from spent pickling liquor. The nickel chloride solutions of Ni concentrations 90 and 1 g/dm3 were used as the electrolytes. The latter was also mixed with 90 g/dm3 Zn in the experiments. All the runs were carried out at room temperature with 40 mV/s continuous polarization speed and with 1/s sampling rate. It was observed that nickel electrodeposition from chloride media containing 90 g/dm3 Ni started with the generation of hydrogen bubbles, entirely blocking the cathode surface. Only a slight current development was observed until the polarization potential ~ -0,8 V. The visual observation showed bubbles also formed at the anode, which may represent chlorine and/or oxygen evolution. While, in the electrodeposition of nickel with only 1 g/dm3 Ni concentration in the electrolyte, metal deposition was hardly observed, but visible hydrogen bubbles constantly blocked the cathode surface. A similar tendency was observed in the mixed-solution electrolysis cell; the initial tiny bubbles accumulated at the cathode surface more than in the pure Zn solution. The enhancement of H2 evolution indicates how nickel deposition may contribute to the loss of useful current in the process of Zn electrodeposition. The mass of nickel deposited from the mixed solutions significantly decreases as the Ni concentration decreases in the electrolyte, while the mass of deposited zinc is relatively constant. It means that the purity of the produced Zn is appreciably higher – with respect to Ni – if nickel is efficiently eliminated from the solution before electrowinning.
High-tin containing soldering waste material could be recycled close to its origin on a flexible scale by electrolytic refining in pure hydrochloric acid&#
Tin refining in solutions containing just the necessary concentration of HCl for stability (1 mol/dm 3 ), has been investigated in different types of electrolysis cells.A rotating cathode with a centrally placed vertical axis was used to demonstrate the importance of the cathode crystal structure.A computer controlled special potentiostat and current supply was developed for the purpose of potentiostatic and galvanostatic experiments.The virtually even surface of the rotating cathode could offer a uniform conditions over also the anode surface.Cathodic and anodic current densities vs. overpotential were plotted and analysed, as well as cathode potential vs. time at different current densities, applying different tin concentrations.At low tin concentrations, the diffusion limiting current sets in early at the, followed by a shift of the dominant cathodic process for hydrogen evolution, whereas at higher tin concentrations tin deposition was undisturbed.Anodic processes were found virtually unaffected by any of the applied conditions.The optimum energy requirement was found at 30-90 g/dm 3 Sn in the 1M HCl solution at ~ 300 A/m 2 anodic current density.1.
In the aluminium industry, the large amount of dross – a by-product of scrap melting – is usually further processed at high temperature re-melting to reclaim the high metallic content entrapped in material. The residue of the hot dross treatment is mainly composed of oxides, and chloride salts from the flux added during the thermo-mechanical process. The major NaCl and KCl components of the added salt are removed by a technically simple leaching process, however, the brine must be treated to remove the dissolved chlorides. We have investigated the energy requirement and efficiency of the evaporation procedure with a simple vessel of insulated walls and submerged heater. The specific heat capacity of the examined NaCl/KCl saturated solution of 2 : 1 mass ratio was determined as ~3155 J/kgK and the latent heat as 1538 J/kgK. The heat efficiency obtained with the system at room temperature initially was found to approach a 97% level as stable conditions were reached. The crystallized NaCl/KCl salt mixture – with possible modifications of it composition – can be recycled to the furnace.
No abstract is provided for this article.
The Liquid Crystal Display (LCD) panels were removed and crushed to be leached. Sulphuric acid of 0.25 M H2SO4 was found best for relatively fast reactions and selectivity, recovering >99% of the indium from the indium‑tin oxide (ITO) layers, while >95% of the tin content was left in the solid residue. As potential impurities, Sn, Fe, Mn, Ni, Zn, Bi, Pb, Al and Cu were analysed in the solutions and in the final product. Synthetic solutions of larger volumes corresponding to the obtained leachate were used for developing the purification and metal recovery steps. Metallic indium was extracted selectively from the solution by cementation on Al plates. The purity of the primary indium deposit was controlled by increasing the temperature to 50–60 °C and keeping the pH in the 0.25–0.5 range, while the aluminium consumption was close to the stoichiometric value. The cemented sponge was vacuum-melted to produce an indium anode block of >99.9% purity for electrorefining. According to the galvanostatic and potentiodynamic results, the optimal electrolyte conditions were found as 50 g/dm3 In, 1 M free Cl− ions, pH 1. The cathodic deposition of Zn, Mn, and Fe was negligible; however, the prior removal of Cu and Sn from the solution is required for producing high-purity indium. Generally, increasing the cathodic current density in the range of 150–600 A/m2 enhanced the purity of the cathodes, while a maximum pH 2 value should be assured. Chloride ion concentration strongly influences the deposit morphology.
Anion exchange separations have been devised to purify model solutions of the usual pickling liquor (SPL) obtained from hot dip galvanization to produce a suitable ZnCl2 electrolyte for electrodepositing pure Zn. The method was based on the established anion-exchange distribution functions in chloride media. Both the simple batch and the more accurate chromatographic methods of separation were examined. The loaded solutions contained Zn, Fe, Mn, Ni and Pb of different concentrations with 1.8 - 2 M NaCl or HCl as the background. The resin bed primarily retained Zn while divalent Fe, Mn and Ni were removed in the loading and the continued rinsing steps with the mobile phase at the initial level of Cl- ion concentration. The elution of Zn was carried out by a significantly reduced Cl- ion concentration. The preliminary reduction of the iron to its divalent state was found of utmost importance. The only difficulty arises from the separation of Pb, which has an equilibrium distribution function comparable to the anion exchange of Zn, however in Europe this minor impurity should not be present at disturbing levels. Kinetic examination of the batch process revealed that Zn sorption is virtually complete within 20 minutes, however despite the low distribution coefficients, some 10 % of iron is also sorbed. Almost 90 % of the retained iron could be in the Fe(III) state caused by aerial oxidation. It was also found that the elution of Zn in the batch technique was not possible by just lowering the Cl- ion concentration. Therefore, the chromatographic method is the only possible way if only chloride media are to be applied.
Anion exchange in HCl solutions has proved as a reliable and efficient tool for the purification of a number of transition metals. There is, however, little reliable information available concerning the anion exchange characteristics of the practically important elements in Group VIa of the Periodic Table (Cr, Mo and W). Therefore, a detailed study has been carried out to investigate the stability of the multiple oxidation states and the relevant anion exchange characteristics. Batch equilibrium results in HCl media have been verified by spectrophotometry, and new anion exchange sorption functions–indispensable for designing separations–have been proposed for the various species.
Possible methods of purification, outlined in Sect. 2.1, are applied in practice to purify the technically important 3d-type (first series) transition metals used in modern industry. This group includes the elements in the d-block of the fourth row of the periodic...
Nagy mennyiségű és nagy sótartalmú végsalak származik az alumíniumötvözetek hulladék alapú gyártásánál keletkező primer olvasztási salakok meleg (termo-mechanikus) feldolgozásából. Az oxidos mátrix mellett ebben viszonylag kevés (5 ~ 10 %) fém és jelentős mennyiségű kloridos alkotók (30 ~ 40 % NaCl és KCl), valamint egyéb vegyületeket fordulnak elő. A vízben oldható, illetve azzal reagáló anyagok miatt, ez a Magyarországon is évi több ezer tonnás nagyságrendben keletkező ipari maradványanyag veszélyesnek minősül és valós környezetvédelmi terhet jelent. A gazdaságos technológiát célzó laboratóriumi kísérletek szerint, a kloridos alkotók kioldása néhány percen belül megtörténik legalább 1:1 cm3/g (víz térfogat:minta tömeg) folyadékarányt biztosítva a szedimentációt megakadályozó intenzitású vízszintes rázás mellett. Ugyanakkor, az edény telítettségi szintjének is van kimutatható hatása. A viszonylag kis költségű megvalósítás a só visszajáratását és a kezelt végmaradvány egyéb célú felhasználását is lehetővé tenné.
In order to obtain a metallic product from the CuCl2-HCl solution purified by anion-exchange separation, the straightforward method of evaporation to dryness and reduction with H2 was investigated. Thermodynamic study of the probable reactions in the Cu-Cl-H-O system pointed out the feasibility of the direct reduction of CuCl2. In order to find out the practical reduction rates and effective recoveries, the process was tested under different conditions. The first step of reduction, which results in the conversion of CuCl2 to CuCl, is readily executable at temperatures slightly below the CuCl-CuCl2 eutectic point. The second step, which results in the metallic product, requires higher temperatures, though safely below the melting point of CuCl. Kinetic analysis of the critical second step provided an activation energy of 138 kJ mol−1 which could be interpreted in terms of a chemical reaction dominated mixed mechanism
Equilibrium studies of anion-exchange distribution pointed out the feasibility of eliminating virtually all the impurities from a copper chloride solution
Most of the 3d-type transition metals have long been staple materials in industry. The advent of modern electronics has brought about a dynamically increasing need for a number of transition metals at an extremely high level of purity. Fields of application include materials for conductors, IC bonding, high-fidelity signal transmission (like Cu), new compound-type semiconductors, opto-electronic devices (like Fe and Zn) and thin films with special magnetic or magneto-optic properties (like Cr, Co and Fe).
The thermodynamic properties of aluminium make its oxidation by various reactant gases an important side-reaction of melting.Magnesium, as a major alloying component plays a further important role in determining the properties of the heterogeneous dross formed during the melting of aluminium alloys.The formed dross may entrap significant amounts of the metal, whose specific amount can be determined by a method including a thermo-mechanical treatment in an induction furnace with no special provisions, allowing most of the entrapped metal to be cast into blocks.Further significant portion of the contained metal is obtained by grinding and physical classification.These steps also a modelling of the industrial dross treatment.The remaining metal content in the fine residue was determined by a special chemical method.The metal content of the dross obtained from the melting of Al alloys of various Mg concentrations were typically in the 70 -85 % range.Magnesium was found to play an important role in determining the mass and the metal content of the dross.The useful effect of applying simple NaCl as melting additive was pointed out.1.
Soldering scrap, generated in large quantities by modern electronic industry, is basically lead-free but contains significant concentrations of copper and silver. This is a valuable raw material, and high purity tin can be obtained by electrolytic refining. There are a number of advantages in applying pure hydrochloric acid–tin chloride media, if the difficulties of solution stability, electrolytic efficiency and deposit morphology can be overcome. An aqueous procedure was developed on the basis of potentiodynamic studies and long-term electrorefining experiments. It can be used for an efficient purification of the valuable waste material in a single operational step. The formation of chloro-complex ionic species may offer a beneficial level of natural inhibition, therefore the inefficient and in some respects harmful organic additives should be omitted. The tendency of Sn(II) oxidation and precipitation can be overcome by properly controlling the concentration of the main components in the electrolyte solution. The virtual cathodic current efficiency can be increased close to the theoretical value by optimizing the composition of the electrolyte solution, the applied apparent current density and the technological parameters of the PCR (periodical current reversal) electric supply. The loose structure of a deposited metal may satisfy the technical requirements but it requires special cell arrangement and care during operation. Electrolyte circulation should only be applied for the control of composition. The attainable purity – of close to 99.99% – surpasses the standard technical requirements.
Scrap based aluminium production is increasing rapidly, however it generates significant amounts of dross of high metallic content.It is common to treat the dross at high temperature in a rotary "converter" furnace to recover most of the entrapped metal.The efficiency of this process depends on many factors, and the Mg content of the metallic phase is important.We have examined an extensive industrial data base and carried out experiments with a laboratory scale rotary furnace to compare the tapped metal yields from dross tapes divided in groups by the Mg-concentrations of the "mother alloys" generating them primarily.It has been found that a medium Mg-content in the metallic phase can offer the best yields.
High-purity Fe was manufactured using anion-exchange separation (AES), oxidation refining, and hydrogen-argon plasma arc melting. As a result, the purity o
