Various types of waste, including dusts, are produced in the pyrometallurgical production of copper from secondary raw materials. According to the European Waste Catalogue and Hazardous Waste List, dusts from secondary copper production are classified as hazardous waste. In secondary copper production 3.87 million tons of copper were produced worldwide in 2017. The dusts are produced in the following thermal operations: reduction of the melt in the shaft furnace (shaft furnace dust), converting (converter dust), and pyrometallurgical refining (refining dust). These dusts contain significant amounts of heavy metals (Zn, Pb, and Sn) in oxidic forms. The dusts are regarded as secondary raw materials, and it is necessary to look for ways of extracting these heavy metals. The aim of this work was to characterize the individual types of dust and determine their quantitative and qualitative composition. The content of heavy metals in copper shaft furnace dust is (52.16% Zn, 19.33% Pb), in copper converter dust (32.40% Zn, 14.46% Pb), and in refining dust (32.99% Zn).
This paper presents experimental results obtained by agitation leaching of hazardous waste sample -flux skimming. Such flux is formed by Zn(OH)Cl and NH 4 Cl phases. Distilled water and water solutions of hydrochloric acid were selected as a leaching media. The aim of this study was to determine optimal conditions of zinc extraction into the solution. The apparent order of reaction with regard to the initial HCl concentration in the leaching solution is n=0.18 in the concentration range from 0.01 mol.dm -3 to 0.25 mol.dm -3 . The obtained results also indicate that the temperature does not significantly affect zinc extraction. The value of apparent activation energy was estimated to E a =3.985 kJ.mol -1 . Optimal liquid to solid ratio L:S=80 for both used leaching media was also determined experimentally as well as the stirring rate at 200 rpm.
Waste generation is a part of every technological process, including galvanizing. The presented paper deals with the characterization of flue dust generated in the process of hot-dip galvanizing, and proposes possible methods for zinc recycling. The flue dust is released into the atmosphere as a white fume above the zinc bath, which is caused by the decomposition of ammonium chloride and zinc chloride present in the flux. This dust is classified as hazardous waste and is a material with a particle size below 90 µm. In addition to zinc and iron compounds, it contains water vapor and oils. The presented elemental, phase, and other characteristic methods of flue dust are important for the subsequent selection of a suitable method for processing the material. At present, this waste is not processed separately due to its low production, which is approximately 0.3 kg per 1 tonne of galvanized steel. The proposed hydrometallurgical recycling method enables the processing of flue dust on a small scale and enables the recovery of high-purity zinc in the form of metallic zinc or zinc oxide.
Copper anode furnace dust is waste by-product of secondary copper production containing zinc, lead, copper, tin, iron and many other elements. Hydrometallurgical Copper Anode Furnace dust recycling method was studied theoretically by thermodynamic calculations and the proposed method was verified experimentally on a laboratory scale. The optimum condition for leaching of zinc from dust was identified to be an ambient leaching temperature, a liquid/solid ratio of 10 and H2SO4 concentration of 1 mol/L. A maximum of 98.85% of zinc was leached under the optimum experimental conditions. In the leaching step, 99.7% of lead in the form of insoluble PbSO4 was separated from the other leached metals. Solution refining was done by combination of pH adjustment and zinc powder cementation. Tin was precipitated from solution by pH adjustment to 3. Iron was precipitated out of solution after pH adjustment to 4 with efficiency 98.54%. Copper was selectively cemented out of solution (99.96%) by zinc powder. Zinc was precipitated out of solution by addition of Na2CO3 with efficiency of 97.31%. ZnO as final product was obtained by calcination of zinc carbonates.
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