During the leaching process of zinc concentrates, the waste materials rich in various metals such as eg. silver are produced. So far no attempts of silver recovery from the mentioned waste materials have been made due to the lack of any method which would be both effective and beneficial. The paper presents some possibilities of application of flotation process in silver recovery form waste materials generated during zinc production

A. Tomaszewska

B. Oleksiak

D. Piękoś

G. Siwiec

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59METALURGIJA 57 (2018) 1-2, 59-61B. OLEKSIAK, G. SIWIEC, A. TOMASZEWSKA, D. PIĘKOŚSILVER RECOVERY FROM THE WASTE MATERIALS BY THE METHOD OF FLOTATION PROCESSReceived – Primljeno: 2017-05-25Accepted – Prihvaćeno: 2017-08-20Original Scientific Paper – Izvorni znanstveni radB. Oleksiak (Beata.Oleksiak@polsl.pl), Silesian University of Technol-ogy, Institute of Metals Technology, Katowice, PolandG. Siwiec, A. Tomaszewska, D. Piękoś - Silesian University of Technol-ogy, Institute of Metals Technology, Katowice, PolandDuring the leaching process of zinc concentrates, the waste materials rich in various metals such as eg. silver are produced. So far no attempts of silver recovery from the mentioned waste materials have been made due to the lack of any method  which would be both effective and beneficial. The paper presents some possibilities of application of flotation process in silver recovery form waste materials generated  during zinc production. Key words: zinc concentrate, leaching, waste products, flotation process, silverINTRODUCTIONIn an era of shrinking natural resources the need of metals  recovery  is focused on recyclable materials or the  materials with  quite limited participation of metals. Recycling has become a necessity both from an envi-ronmental and economic point of view. Since there is a wide variety of the materials  which contain metals,  and both the content and their physical nature are varied, the need for the methods of  metal recovery which suit each individual recyclable  material appeared. The methods should guarantee high degree of recovery efficiency and meet the environmental requirements.The paper presented suggests the use of flotation process for the separation of metals from the nonmetal-lic components of waste materials being the by-prod-ucts  of the leaching process of zinc concentrates. The leaching process is one of the main technological  stag-es of zinc production [1]. Flotation is the method of separation most frequently used for the processes of en-richment of metal ores and carbon. Flotation occurs as the result of interfacial phenomena in the  solid/liquid/gas system. If a grain exhibits hydrophilic properties under certain defined conditions, then in the flotation process it can be separated from the grains which do not demonstrate such properties. The intensity of flotation process depends on a number of factors the most essen-tial being properties of flotation foam (type of frothing agent) and grain size The flotation method can be used for separation of  metal from grain fraction of some ox-ides and carbides [2, 3]. This was confirmed by test re-sults obtained during recovery of native gold from poly-metallic copper ores performed by CSIRO Minerals in Australia [4]. The studies on silver recovery form jewellery wastes carried out with the flotation method ISSN 0543-5846METABK 57(1-2) 59-61 (2018)UDC – UDK 546.47-66.082:66.066.1.004.8:546.57=111have also been conducted at the Silesian University of Technology in Poland [5].DESCRIPTION OF TECHNOLOGICAL PROCESS AND ITS FINAL PRODUCT USED FOR FURTHER STUDIESThe material used for tests in the form of slime is the effect of leaching process of zinc concentrates which have been developed as the result of flotation of ores containing zinc.Zinc concentrates go to a Roasting Department where sulfide zinc  concentrates are subjected to roast-ing. Roasting process is conducted in a fluidized bed furnace at a temperature 960OC. The product is zinc ox-ide and roast gases. Zinc oxide goes to Zinc Electrolysis Department and gases which contain  SO2 after cleaning go to Sulphuric Acid Plant.Oxide concentrate supplied by the Roasting Depart-ment is subjected to leaching process at the  Leaching Department. There, it is dissolved in sulphuric acid  with the participation of reverse acid electrolyte bath originat-ing from the Department of Electrolysis . The resulting acidic zinc sulfate solution is then subjected to sedimen-tation. After clarification it is cleaned with zinc fluid and filtered. The electrolyte solution is cooled in cooling tow-ers and subjected to the process of electrolysis. Addition-ally to the generated electrolyte, waste slime of 20-25 % of its initial mass is produced. And  it is this slime which is the subject of the described investigations.CHEMICAL COMPOSITION OF THE STUDIED WASTES In order to determine the chemical composition of wastes, 2 samples were taken and subjected to qualita-tive analysis with the application of Joel  JDX-7S X-ray. The it was followed by quantitative analysis with 60B. OLEKSIAK et al.: SILVER RECOVERY FROM THE WASTE MATERIALS BY THE METHOD OF FLOTATION PROCESS METALURGIJA 57 (2018) 1-2, 59-61Unicam atomic absorption spectometer Solaar M6. X-rays of  wastes for the analyzed samples are present-ed in Figures 1-2, whereas Table 1 contains their chem-ical compositions. Table 1 Chemical composition of wastes under studiesZn / % Pb / % Mg / % Fe /% Cd / % Ag / %18,6 5,85 0,68 19,8 0,23 0,023MATERIALS AND TEST APARATUSIn the course of the conducted research on the flota-tion process, various types of frothing agents, collectors and pH regulators have been used. They are listed in Table 2Table 2 Agents used in the studies of flotation process Agent typefrothing agents pine oil, Dawtrotcollectors oleic acid, sodium amyl xanthate, sodium ethyl xanthatepH regulators CaOTEST RESULTS The conducted studies aimed at determining the con-ditions of the flotation process of materials contained in wastes. The analysis of the following factors affecting the course of floating process has been performed: rotor speed, gas flow rate, type and amount of flotation  agents, process length.The studies with the use of wastes generated at the leaching process have been conducted at the rotor speed of 300 and 500 rpm.Silver content in the flotation concentrate reaches the concentration close to its final content in the product of flotation already after ca. 15 min.  It proves that run-ning the process for a long time is not necessary. Longer Figure 1  Sample X-ray/radiograph of waste generated in the leaching process (sample 1)Figure 2  Sample X-ray/radiograph of waste generated in the leaching process (sample 2)Figure 3  Laboratory flotation device used in the studies of flotation processFigure 4  The dependence of the degree in silver enrichment on pH at the rotor speed of 500 rpm (gas flow rate 4 cm3/min)Figure 5  The dependence of the degree in silver enrichment on the rotor speed (pH = 6, Dawtrot as frothing agent, gas flow rate 4 cm3/min)61B. OLEKSIAK et al.: SILVER RECOVERY FROM THE WASTE MATERIALS BY THE METHOD OF FLOTATION PROCESSMETALURGIJA 57 (2018) 1-2, 59-61SUMMARYOn the basis of the carried out investigations the fol-lowing conclusions can be formulated:-  Flotation process can be applied successfully for enrichment of silverbearing fractions of wastes generated in the leaching process of roasted blend.-  The best results have been obtained for the follow-ing frothing agents: Dawtrot collectors: methyl xanthate, sodium ethyl xanthate.-  The high rest degree in silver enrichment of the concentrate has been achieved for the following parameters of the flotation process:- rotor speed - 500 rpm,- flow rate - 4 cm3/min,- pH=6.-  At best, the degree of concentrate enrichment in silver was 169% which has been achieved through the studies of flotation process of silverbearing wastes generated in the leaching process.REFERENCES[1]  M. K. Jha, V. Kumar, R. J. Singh, Review of hydrometal-lurgical recovery of zinc from industrial waste, Elsevier Resources, Conservation and Recycling 33 (2001), 1–22.[2]  J. Drzymała, H. A. M. Ahmed, Mathematical equations for approximation of separation results using the Fuerstenau upgrading curves, International Journal of Mineral Proces-sing 76 (2005) 1-2, 55-65.[3] J. Drzymała, A. Łuszczewicz, D. Foszcz, Aplication of up-grading curves for evaluation of past, present, and perfor-mance of a separation plant, Mineral Processing and Ex-tractive Metall. Rev. 31 (2010) 3, 165-175.[4]  G. C. Allan, J. T. Woodcock, A review of the flotation of native gold and electrum, Minerals Engineering14 (2001) 9, 931-962[5] B. Oleksiak, G.  Siwiec, A. Blacha-Grzechnik, Recovery of precious metals from waste materials by the method of flotation process, Metalurgija 52 (2013) 1, 107-110.Note:  Krajewska T. is responsible for English language, Katowice, Polandtime of the process reduces the concentration in the product of flotationFigures 4 - 7 depict sample results of the studies on flotation process which have been conducted on wastes form leaching process of the roasted blend.Figure 6  The dependence of the degree in silver enrichment on gas flow rate (Dawtrot as frothing agent, rotor speed of 500 rpm, pH = 6)Figure 7  The dependence of the degree in silver enrichment on the type of frothing agent with the use  of  amyl xanthate as collector, air flow rate cm3/min, rotor speed of 500 rpm

Silver recovery from the waste materials by the method of flotation process

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