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A large amount of currently useless basically oxide residue is produced by the treatment of dross obtained from the melting of alloyed aluminium scrap.Its negligible residual metallic component does not make it feasible for any further metallurgical processing.On the other hand, it may have a high content of chloride salts.Its removal may not only serve the purpose of recycling but it may be mandatory to make this residue suitable for applications in preparing construction and road paving materials, or as a slag forming additive in the steel industry.A hydrometallurgical treatment with pure waterafter fine grindingmay be efficient in this respect and it may even reduce the residual metallic content if acidic or alkaline media are also used.In order to develop a suitable method of purification, the composition of the raw residue has been examined by SEM and XRD techniques and carried out experiments to determine the efficiencies of the treatments with water, sulphuric acid and sodium hydroxide.The results show that leaching with water can remove the main salt components of NaCl and KCl in a short time.However, the evolution of some NH3 gas from the side reaction of the AlN compound formed during the preliminary thermos-mechanical treatment cannot be avoided.The application of sulphuric acid can be efficient not only in removing the residual metal content but also in suppressing the evolution of NH3.Although the sodium-hydroxide reagent is capable of aggressively dissolve aluminium not only in the metallic but also in the oxidised states, but it may also enhance the evolution of NH3.According to the phase composition and structure of the treated materials, water leaching -perhaps combined with an extra step of sulphuric acid leachingcan be satisfactory for assuring the state of the residual dross to be accepted in non-metallurgical applications.1.

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.

Potentiodynamic and galvanostatic experiments have been used to investigate the electrodeposition of Zn and to develop a reliable recovery method from a purified spent pickling liquor (SPL) of hot dip galvanization. The main bjective was to find the suitable conditions to deposit high-grade Zn from the purified ZnCl 2 –HCl–NaCl solution in a conventional electrowinning cell holding the stationary electrolyte. The effects of pH (1.5–4.5) in and Zn concentration (30–150 g/dm 3 ) in the stationary electrolytes were studied first by the potentiodynamic method to reveal the major characteristics of the cathodic process and to give reference for further practical examinations by the galvanostatic technique. The electrowinning experiments pointed out the effects of these major parameters, beside other practical factors, like apparent current density (c.d.) and additional NaCl concentration. The long-term galvanostatic experiments proved that the current efficiency (c.e.) increases significantly as the pH and the Zn concentration are increased. A c.e. of ~ 99% can be reached with an electrolyte of pH ~ 5, Zn concentration ~ 50 g/dm 3 applying a c.d. in the 300–600 A/m 2 range. Increasing the Zn concentration could considerably improve also the deposit morphology. The addition of NaCl can practically improve the c.e. if the Zn concentration is at least around 50 g/dm 3 . In contrast, this improvement is largely off-set by the negative effects of strong H 2 evolution at low (e.g. < 10 g/dm 3 ) Zn concentrations. Extremely high Cl − ion concentrations, however, inhibit the cathodic reaction by stronger chloro-complex formation. In this case the intensive H + reduction causes hydroxide precipitation.

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.

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.

The possibility and the main characteristics of cementation applied for indium recovery from aqueous chloride and sulphate solutions were considered theoretically and examined experimentally. Aluminium and zinc, in the forms of plates and powders were examined as reducing agents. It was found that indium can be cemented on Al or Zn surfaces best in chloride solutions. Zinc plate proved to be inefficient, however Zn powder performed well. In the case of aluminium, both the plate and the powder worked well, and virtually complete recoveries of indium could be achieved within 10–60 min - depending on the pH and temperature of the solutions. The produced sponge can be detached easily from the Al plate and efficiently melted under protective atmosphere, vacuum or salt flux. The purity of the produced sponges can be generally above 99.9%, and the cementation on Al plate produces the purest indium.

Primarily, the mechanical removal of LCD panels from smartphones was examined, and a relatively easy and quick manual method was established. The LCD panels can be separated from the rest of the screen in a few seconds. In the cases of more tightly packed applications, the whole screen can be directly ground to a fine powder. The separated LCD screens were leached in different concentrations of HCl and H2SO4. The latter was found as practically more advantageous. Leaching with slightly acidic solutions (0.1 M H2SO4) results in longer leaching time, however solutions with higher purity can be obtained. If further purification is required, a relatively straightforward method of selective hydrolytic precipitation has also been examined. The practically recoverable amounts of indium may be close to the 400 mg/kg level in a dilute sulphuric acid solution containing less than 10 mg/dm3 of total impurities (Fe, Zn, Al, Cr, Ni and Cu).

The major goal of this potentiodynamic study was to explore the characteristics of zinc electrodeposition from chloride (ZnCl2 -HCl) media.The influence of various operating parameters such as zinc concentration in the 30 -150 g/dm 3 range, acidity level (pH in the 1.5 -5.5 range) and rotation speed (0 -950 r.p.m.) were investigated at room temperature.Deposit morphologies were recorded by a digital camera during cathodic polarization.The physical quality of the electrode surface seems to be one of the important parameters not only for the deposit structure but also for the side reaction of H2 evolution and also for the development of the polarization curves.There are three kinds of cathodic depositions occurring.It generally starts with a uniform and stable structure, followed by a sponge-like deposit and finally it turns into a dendritic growth due to concentration changes near the surface.However, electrolyte agitation can influence the deposition pattern.With increased rotation speeds (above ~ 500 r.p.m.), resulting in higher available concentrations of electroactive ions at the surface, there is not much sponge-like deposit, yet the dendrite formation at the edges could not be avoided.The strong increase in the actual specific surface area of the cathode, due to the sponge-like deposit and the dendrite formation, caused irregularities in the potential change executed by the computer controlled potentiostat.Although this instrument was designed and produced at the institute specifically for high speed measurements.By lowering the pH in the electrolytes of the lowest Zn concentrations, the side reaction of H2 evolution soon appeared, after the limiting current of Zn deposition was reached.At higher Zn concentrations though, instead of a clear limiting current, the slope of the polarization curve persisted all across the examined potential range, indicating a continual co-deposition of H2 together with that of Zn.

Pickling is one of the essential steps in galvanizing industries in which hydrochloric acid (HCl) is used as the main composition to clean up the steel surface. This HCl lost its pickling efficiency because of decreasing in its concentration as well as increasing metals content because of dissolution processes. Recovery processes could be done to this kind of waste, so circular economics and a nearly zero waste cycle industry can be established. Processing SPL by electrodeposition is possible to recover pure metal from the waste solution. However, the presence of iron in the zinc chloride solution changes the nature and the conditions. It was found that the effect of iron concentration on the polarization curves is complex. Initially it has a negative effect on the generated cathodic current because of the enhancement of hydrogen bubble formation. Further increased iron concentrations may make the composition of the Zn-Fe deposit dominantly in favour of iron, resulting in a hydrogen dominated cathodic mechanism. Controlling the parameters such as Zn and Fe concentration, and the electrolyte's agitation intensity could play essential impacts on the electrodeposition of zinc from chloride media. Nevertheless, separation is still essential; thus, introducing the anion exchange separation to prepare the electrolyte is needed to achieve an acceptable quality of zinc deposition. In the relatively low concentration of HCl, Zn tend to be retained in the resin as its more likely to produce chloro-complex. As in the higher concentration of HCl (>1), Fe(III) distribution fucntion in HCl will increase thus the Fe may retain in the resin. However oxidation state control can be the answer of this problem by reducing Fe(III) to Fe(II) or in order to optimalize the separation process partially precipitation of Fe might be an option.

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...

White LED bulbs contain significant quantities of Cu, Sn, Pb, Al and appreciable amounts of Ga and traces of In. A feasible recovery of the valuable components – either in metallic or compound forms - has been devised and examined. Leaching the assemblies with 4 M HNO3 at 80 °C could leach Cu, Fe, Pb and Ag, while Al is passivated and Sn precipitates. In this step, the LED beads are detached from the aluminium base plates. The solid residue comprises of practically pure Al plates and Sn(OH)4. Pure Cu hydroxide was recovered by precipitation. The physically liberated solid bodies of the detached LED beads were roasted to convert Ga and In into soluble compounds. While a simple oxidative roasting could assure ∼80% recovery, alkaline fusion with NaOH or roasting with Na2CO3 yielded >90% recoveries. Leaching the roasted material with 1–6 M NaOH could efficiently dissolve Ga, while In was only slightly attacked. However, the major portion of In could be leached by applying as high as 10–11 M NaOH with similar efficiencies. Finally, the extractions of Ga and In were studied by electrowinning from the alkaline solutions yielding 99.99% pure Ga and 99.9% pure In deposits, respectively.

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.

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.

Electrodeposition of Zn from chloride media had been studied by potentiodynamic method to understand the characteristics of Zn recovery from spent pickling liquor (SPL). Various concentration, pH, agitation speed and impurities contamination were examined in the series of experiments. The influence of Zn concentration in the range of 30-150 g/dm 3 relevant to the real SPL were studied along with acidity level change (pH 1.5-5.5). It was found that the cathodic deposition started with the uniform patern followed by sponge-like deposit and as the concentration of the electrolyte near the cathode surface decreased, the dendritic deposition start to grow, especially at the edge of the cathodes. It was found that the effect of iron concentration on the polarization curves of zinc from SPL is complex. Initially it has a negative effect on the generated cathodic current because of the enhancement of hydrogen bubble formation. At a higher concentration range, however, iron deposits at a relatively higher rate. Further increased iron concentrations may make the composition of the Zn-Fe deposit dominantly in favor of iron, resulting in a hydrogen dominated cathodic mechanism. It is also characterised by the loss of the dendritic structure – attributed mostly of zinc deposition when hydrogen bubbles are not blocking the cathode. As the gas evolution becomes more characteristic, the deposit tends to become more powdery. Under such conditions the cathode becomes smoother and the active surface is reduced. Increasing the stirring speed, the powder was easily detached from the cathode surface. Iron, however can enhance the cathodic deposition process of zinc. With 30 – 60 g/dm 3 iron in the 90 g/dm 3 Zn solution, an increased iron concentration resulted in a significant increase in the mass of the deposited zinc. This may be interpreted by a beneficial effect of the increased hydrogen evolution enhancing the zinc ion transport to the electrode surface. However further increments of iron had a contrary effect, possibly by the locally increased – and generally detected – pH of the solution indirectly causing a superficial precipitation of hydroxides. Technically pure zinc could be deposited from only low-iron (< < 30 g/dm 3 ) zinc solutions (of 90 g/dm 3 Zn) at relatively vigorous stirring speeds. High iron concentration in the solution is definitely unsuitable for obtaining the aimed quality of cathode zinc.

Equilibrium studies of anion-exchange distribution pointed out the feasibility of eliminating virtually all the impurities from a copper chloride solution

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

By studying the leaching kinetics of indium from waste liquid crystal displays (LCD), it was pointed out, that recoveries of > 90 % are possible with 0.5 M HCl at 80 °C or 2 M HCl at 55 °C. The anion-exchange sorption of indium was found practically negligible from sulphate solutions, however, in chloride solutions of 2 mol/dm3 HCl (or NaCl) indium was moderately sorbed (log D = 0.83), and a further increase of the distribution coefficient (log D = 1.1) was found until 6 mol/dm3 Cl- ion concentration. Based on the determined activation energies, at low (< 1 M) HCl concentrations, the process is controlled by the formation of the complex species, while above, diffusion and transport processes are more important. The devised chromatographic separation in an anion-exchange column was able to eliminate virtually all the practical impurities. After loading the leachate of 5 mol/dm3 chloride ion concentration, the non-sorbed alkali, alkaline earth and some transition metals can be removed by rinsing the resin bed with a solution of 2 mol/dm3 chloride ion concentration. Indium can be eluted by reducing the chloride ion concentration in the influent to 0.25 mol/dm3. The still retained elements (Zn, Sn, Bi) can be removed with 1 M NaOH solution. The pure solution was used to electrowon indium metal, which was analysed by SEM-EDS and - after dissolution – with ICP – OES. The purity of the metallic indium product was found to be 99.9997 %.