69 publications from this institution
The production of ferro-alloys from waste Li-ion batteries has been examined thermosdynamically and experimentally. It was found that Co and Ni can be reduced even with relatively low pCO/pCO2 ratios in the gas phase, while the reduction of Mn or Fe requires strongly reducing conditions and higher temperatures. Even the reduction and selective recovery of Li are thermodynamically possible due to the possible evaporation. The optimum slag compositions were evaluated theoretically, followed by an experimental investigation. Ferrocobalt, ferrocobalt-nickel and ferrocobalt-nickelmanganese were produced using calcium-magnesium-ferrite type slags. Furthermore, secondary Al dross – containing Al – was also tested both as a reducing and a slag-forming agent for the production of ferrocobalt and ferromanganese affiné.
White light beads containing light emitting diodes (LED) were removed from the commercial light bulbs and treated with a complex, but easily implementable hydro-electrometallurgical method to recover pure Ga. Using concentrated H2SO4 as the digesting agent at 180 °C for 60 minutes resulted in >90% efficiencies of gallium and indium solubilization by the subsequent water leaching. All metals - except for Ag – could be fixed in a strongly acidic cation-exchange resin by loading the solution into a chromatographic column. Indium, Cd, Pb and Sn are selectively eluted with 1 M HCl, while Al can be transferred into the aqueous phase using a 0.25 M NaF solution. Gallium is recovered in a pure eluate from the resin with 3 M NaOH, and finally, Y is eluted with 0.5 M Na2CO3. The cathodic deposition of Ga from the alkaline eluate was studied by potentiodynamic and galvanostatic methods. As high current efficiencies as 99% could be reached in solutions of 50 g/dm3 Ga and 6 M free NaOH at 300 A/m2 cathodic current density. Decreasing the NaOH concentration to 1.5 M resulted in a 10 ~ 15% decrease in the current efficiency. Lower Ga concentrations also reduced the current efficiency significantly. The cell voltages were in the range of 2.1 – 2.4 V, yielding a relatively low (2 kWh/kg) specific energy consumption. The obtained cathodes were immersed into 2 M HCl at 55 °C, resulting in 99.999% Ga metal melted from Ti mother plates.
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%.
Although the environmental industry has developed many modern techniques to treat spent pickling liquors, including also the membrane separation, still neither of them can be applied alone for the efficient treatment of HCl containing spent pickling solutions originating from hot dip zinc galvanizing plants. In this area, the most frequently applied treatment is still the common precipitation–filtration process. However, this technique generates large amounts of hazardous waste to be deposited at high costs and does not recover the acid. Our novel approach to treat such spent liquors consists of an ion-exchange separation and a membrane electrolysis step to recover HCl, Fe and ZnCl2 as saleable products. The experimental part of this paper concentrates on the anion-exchange separation of the components in the raw liquor and the cathodic deposition of iron at varied pH, temperature and cathode materials by using potentiodynamic testing technique. As a result, a direct anion-exchange with a strongly basic resin can separate the main components (Fe and Zn) of the raw solution loaded at a moderate flow rate into the column. The recommended conditions for the electrolytic deposition of iron are pH>1 and nickel cathode.
A residual dross of high quantity and high salt content arises from the hot (thermo-mechanical) treatment of the primary dross generated by the production of aluminium alloys from scrap. It contains a relatively low concentration of metal (5 – 10 %) but a high amount (30 - %) of chloride salts and some other components beside the oxide matrix. Due to the components dissolved in or reacted with water, this industrial residue - arising in thousands of tons also in Hungary – qualifies as hazardous and causes a real burden to the environment. According to the laboratory experiments aimed at an economical technology, the chlorides are dissolved within a few minutes when a liquid/solid ratio of 1:1 cm3/g (water volume:sample mass) is assured with an intensity of the horizontal shaking to prevent sedimentation. However, the filling ratio of the vessel also appears to have an effect. An implementation of relatively low cost would allow the recycling of the salt and the application of the final residue for alternative purposes.
Recent application in advanced electronics have increased the practical importance of ultrahighpurity cobalt. Anion exchange in HCl media is considered an
High-tin containing soldering waste material could be recycled close to its origin on a flexible scale by electrolytic refining in pure hydrochloric acid&#
The rotary converter melting of Al-containing drosses with and without NaCl addition was examined. It was found that simple NaCl can enhance the recovery by 9% while decreasing the mass of the secondary dross. It implied a significant decrease in the metallic Al concentration, which indicates a superior coalescence of the molten metal drops when NaCl is present. However, the thermodynamic analysis showed that it might also imply the possibility of a certain degree of aluminothermic and magnesiothermic reduction of NaCl. On the other hand, neither the analysis of the flue dust nor that of the tapped metal showed the presence of the reaction products; thus, no melt contamination occurred.
Promising applications in advanced electronics have created a demand for ultra-high purity iron. Anion exchange in chloride solutions may offer an efficient and practical way of purification. Examination of anion-exchange distribution functions revealed a variety of behavior patterns to be exploited. Elution tests in laboratory-scale columns suggested that virtually all the impurities can be separated from the iron chloride solution by anion exchange. The hydrochloric acid concentration and volume of the rinsing and eluent solutions determine the efficiency of the procedure. Separation of certain elements (e.g. copper and molybdenum) requires strict control of redox conditions. The designed procedure consists of two anion-exchange steps. In the first step and during solution preparation, those impurities are separated which can be precipitated by iron, or sorbed in the resin at low HCl solutions under reducing conditions determined by the addition of Fe powder. The remaining impurities are separated from iron, applying a second ion exchange step under oxidizing conditions. Performance characteristics (yield, purification ratio and volume efficiency) of the separation indicate the optimum parameters of the rinsing and eluent solutions and the suitable way of defining the collected volume fraction of the effluent.
The main purpose of this research was to find a suitable, economical and simple way to recover mainly zinc from waste Zn-Mn batteries.The most feasible way can be leaching the soluble zinc content in diluted sulphuric acid after a proper physical separation of the raw material.The leachate however contains an equally high concentration of manganese, and the residual iron contentnot removed by magnetic separationgoes also into solution.Other significant impurities may be copper, nickel and cadmium, by experience.Electrolytic deposition of technically pure zinc is made possible by an efficient hydrolytic separation of iron at the end of the leaching step, followed by the oxidative precipitation of the manganese content.The practically neutral and pure zincsulphate solution can be utilized advantageously for electrowinning zinc.The procedure is still hardly economical, which shortcoming can be improved by the admixing of the easily available centrally stored electric arc furnace dust, containing comparable amounts of zinc, but very low concentration of other soluble metals.Experimental results have proved the viability of this combined processing, although complete recovery of the zinc content is not achieved from the added dust, which results in a basically zinc-ferrite type residue.It can be however recycled to ferrous metallurgy together with the manganese dioxide precipitate and the carbon-iron hydroxidemanganese dioxide containing residue from the battery waste leaching step.The other large scale source of secondary zinc is the electric arc furnace (EAF) dust, which is produced and stored at high quantities in a centralized manner.It is an interesting proposition to improve the availability of zinc by introducing the less soluble, but more accessible and less complex EAF dust into the processing scheme of the better leachable but more complex and less available Zn-Mn battery waste.The latter material represented a collected amount of 164 000 tons in 2003 in Europe consisting of ~30% Zn-carbon and ~60% Zn-Mn varieties [1].
Recycling of the impure tin generated by the hot dip tinning and wave soldering technologies widely applied in modern electronic industry can be carried in a flexible and economical way even at relatively low production rates by electrorefining. In order to avoid the economical disadvantages of the alkali stannate or the sulphuric acid – cresylic phenylic sulphonic acid baths, the hydrochloric acid tin chloride electrolyte solutions can be applied. The major difficulties of solution stability, cathode corrosion and rough electro-crystallization can be overcome by optimizing the solution composition and the current parameters. Strong chloro – complex formation in the hydrochloric acid solution enhance stability of the Sn(II) species and the consequent natural inhibition promotes a cathodic deposition of acceptable quality. The virtual current efficiency and the morphology of electro-crystallization were improved by applying periodically reversed (PCR) current. Although cathode corrosion could be depressed to a negligible level, dendritic crystal growth remains to be dominant, therefore special cell arrangement and cathode handling should be applied. The cathode deposit is easily removed and melted, allowing to obtain a recycled tin of high purity.
No abstract is provided for this article.
A flexible and efficient process of tin electrorefining has been devised, using aqueous solutions of relatively low HCl and tin chloride concentrations. Any additives have been avoided, which enhances purity but also incurs the difficulty of obtaining compact cathode deposits. This feature is however assisted by the natural inhibition in complexing chloride solutions and the modulation of the current. Due to the rough dendritic crystal growth, special provisions are required to avoid short circuiting. Using short pulses in the 50-250 μs range of periodically reversed or interrupted currents, the lengths of the usually large dendrites can be moderated. The periodic current with extremely short cycle times and special electrode arrangement can be utilized for averting short circuits and for achieving better coverage of the cathode surface. This technique can be applied efficiently to obtain pure tin from soldering waste materials.
The waste material produced in lead-free wave soldering is melted, skimmed and cast into anodes.Anode slime, the by-product of electrorefining in hydrochloric solutions is collected and the basically undissolved silver and copper constituents are removed by selective leaching.The first step is the elimination of metallic tin using HCl of high concentration and temperature, followed by the leaching of the nobler metallic components in HNO 3 under similar conditions.Kinetic study on the leaching behavior of the raw anode slime in both media has shown the optimum conditions.The metallic tin content of the anode slime can be dissolved virtually completely in 10 M HCl at the highest possible temperature of 85 o C, however it takes about 3 hours.On the other hand, silver can be o quickly dissolved in about 15 minutes by applying approx.50% HNO 3 at 90 C. Combination of the two steps in this order can result in an efficient recycling of the slime by producing relatively pure SnCl 2 and AgNO 3 solutions, respectively.The tin content can be recycled conveniently to the tin electrolysis and the silver containing solution can be used for recovering silver by electrowinning or precipitation.
The main characteristics of electrolytic reduction applied for indium recovery from aqueous chloride solutions were considered theoretically and examined experimentally. In comparison, also sulphuric and other media were examined. Potentiodynamic examinations pointed out that chloride electrolytes are superior to sulphuric, nitric and methanesulphonic acid ones for efficient In deposition. The optimum conditions allowing higher than 90% cathodic current efficiencies, were determined by galvanostatic experiments, confirming the findings of the potentiodynamic study. In contrast, similar sulphate electrolytes could only yield lower than 50% efficiencies, mainly because of stronger hydrogen evolution and the potentially slower transformations of the complex ions. The structure of the – relatively dense - cathodic deposit was examined. Various levelling agents were also tested, and gelatine was found efficient in preventing the formation of dendrites.
A better procedure for recovering high-purity Zn from the SPL solution has been devised. To provide a suitable electrolyte for the efficient cathodic deposition of high-purity Zn, complete anion-exchange purification had been done by chromatographic technique. The process was then continued by galvanostatic electrodeposition to determine the efficiencies. As the SPL needs to be neutralized before any attempts of Zn electrodeposition, NaCl may provide the required source of Cl- ions for complex formation. The equilibrium studies of the anion-exchange distribution in such solutions showed similar tendencies to those already known in HCl media. The anion-exchange chromatographic separation was devised – with the finer tuning of the parameters – according to the equilibrium result, but other physical parameters were also examined for improving the efficiency of separation and the recovery of Zn. The devised anion-exchange separation in chloride media can purify the SPL, containing Zn as the valuable component and higher concentrations of Fe as the main impurity. The most important impurities (Fe, Mn, Ni, Al and Co) can be efficiently separated in a dissolved state. At the same time, Zn is sorbed in the strongly basic anion[1]exchange resin at a moderate Cl- ion concentration (~ 2 M). Stirring with Fe chips provides a reduction of iron to the Fe(II) state. The remaining problem is minor copper contamination in the same effluent fraction as Zn, which however can be eliminated by a simple additional step of cementation or directly by pre-electrolysis.
A process consisting of anion exchange in a hydrochloric acid solution, electrowinning, plasma arc melting and electron beam melting of electrolytic cobalt has been developed for preparing high-purity cobalt. Glow discharge mass spectrometry (GDMS) and residual resistivity ratio (RRR) were applied for analysis and purity evaluation of the produced cobalt. Almost all the metallic impurities except for copper were removed efficiently and reduced to lower than 1 mass ppm by the anion exchange step. Electron beam melting at a final step was very useful for removal of copper by vaporization from the molten cobalt and the copper concentration could be lowered to below 1 mass ppm. As a result, high-purity cobalt with above 99.9995% in purity (RRR=210) was produced by this practical purification process.
Different ways of investigation were applied to address the main difficulties of electrolytically refining the tin-based lead-free soldering waste materials in chloride solutions. The characteristics of electrorefining and the phenomena of electrocrystallisation have been targeted by examining the electrode processes with different copper and silver concentrations in the anodes. Galvanostatic experiments were carried out using a specially developed system detecting the changes in the electrode masses continually, complemented by the recording of the electrode potentials. In order to clarify the main cathode and anode processes, further investigations were carried out by the potentiodynamic technique. Galvanostatic results pointed out the causes of current losses and rough deposit structure. Potentiodynamic examinations have demonstrated the strong influence of material transport on the electrode processes. Nevertheless, with a quasi-optimised procedure, cathode tin of higher purity than technical standards could be achieved from the soldering waste material in a conventional cell.
Extraction of tin from tinned plates serves the double purpose of preparing steel scrap for re-melting and producing secondary tin. The best route to reach these goals is offered by hydrometallurgy. In order to compare the efficiency of chemical and electrochemical removal of tin coatings, the mechanisms of the principal processes were investigated. Laboratory analysis demonstrated that tin dissolution rates in oxygenated NaOH solutions are controlled by the oxygen transport to the reaction interface. Increased sodium hydroxide concentration (>0.1 M) has a negative effect on tin dissolution because of reduced oxygen diffusivity. The efficiency of electrolysis in alkaline stannate/stannite electrolytes strongly depends on the applied current density and temperature. Under the applied experimental conditions, cathodic extraction of tin (in an appropriate spongy form) could be stabilised at current efficiencies higher than 80%. Measurement of the anode potential was found to yield a proper end-point indication for de-tinning tinned steel plate scrap in anode baskets. The results demonstrate the practical advantages of electrochemical processing in alkaline media.
The behavior of cuprous species at electrodes polarized in hydrochloric acid solutions has been investigated in order to obtain the fundamental knowledge o
