Search
Search Results
-
Efficient removal of salts from the residual dross of aluminium melting
259-269Views:107A 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.
-
Potentiodynamic Study of the Effects of Nickel on The Electrodeposition of Zinc from Chloride Media
15-24Views:104Abstract. 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.
