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1、Phase Analysis of a Zinc Mine Tailings in Southern Guizhou China Ji ZHENG1*, Jinyan ZHAO1, 2 1Institute of Advanced Technology, BMEI Co., Ltd. Beijing, China 2College of Water Research, Beijing Normal University, Beij

2、ing, China * Dr. Ji Zheng, zhengji@bmei.net.cnAbstract—In the flotation process of zinc ore, abundant mine tailings was left after valuable metal concentration extracted. A zinc mine tailings sample from the south pa

3、rt of Guizhou province of China was characterized with XRD and IR analysis and its composition was investigated with chemical analysis. Chemical phase analysis was also conducted to identify occurrence of Zn, Fe and

4、heavy metals Pb, Cd, Cr, Hg and As. Mineral phases of the mine tailings were dolomite CaMg(CO3)2 chiefly with trace pyrite FeS2. Heavy metals in the mine tailings were mainly lead with concentration 348 μg/g and near

5、ly 60% lead lay in sulfide phase. An integrated utilization technology was suggested based on the mineral phases and occurrence of metals in the mine tailings. Keywords-zinc mine tailings; phase analysis; heavy metal

6、; integrated utilization I. INTRODUCTION China is rich in zinc ore resource with proved reserves about 0.13 billion metric tons (data for lead-zinc ore). After Zn extraction and beneficiation using floatation technolo

7、gy, abundant mine tailings was left, and generally heavy metals such as Pb, Cd, etc. remained in the zinc mine tailings, too. Not only polluted soil, sediment and groundwater or surface water near the tailing pond an

8、d exposed inhabitant into big risk, those heavy metals also brought additional difficulty to tailings utilization [1-3]. To find out chemical component, mineral phase, density and occurrence of heavy metals in the tai

9、lings is very important to protect environment and inhabitant near the tailing pond and to exploit the solid waste effectively. II. MATERIALS AND METHODS A zinc mine tailings was sampled from a tailing pond in south

10、ern Guizhou province, China. The tailings sample, mud- like remainder of ore flotation, was dried by air and then characterized by XRD and IR, respectively. Powder XRD was measured using an X-ray diffractometer (D/Max-

11、3C model, Rigaku Co., Japan) at a scanning rate of 2 °/min with 2θ angle from 10°to 80° . IR spectrum was collected using a Fourier transform infrared spectroscopy (Nicolet 5700 FT-IR model, Thermo Fis

12、her Scientific Inc., USA) with a conventional KBr pellet method. Chemical components of the tailings were analyzed using wet chemical method. Occurrence of elements Zn, Fe and heavy metals Pb, Cd, Cr, Hg and As was in

13、vestigated with a sequential chemical extraction procedure [4]. In this chemical phase analysis procedure, the dried sample at first was dissolved with deionized water and solid phase was separated with a high speed

14、centrifuge, then supernatant was used to detect soluble phase with ICP-MS/OES. Extracting reagents CH3COONH4, CH3COONa-CH3COOH buffer solution, Na4P2O7?10H2O and KClO3-HCl were used in turn to partition target ele

15、ment in specific fractions and supernatant was used to detect target element in sorption phase, carbonate, sulfide or organic phase respectively with ICP-MS or ICP-MS/OES. However, the residue of the sample treated he

16、re in the sequential extraction procedure was too small to be tested, the total amount of these elements had to be surveyed in addition, where tailings sample was dissolved with mixed acid HF- HNO3-HClO4 and supernata

17、nt was measured with ICP- MS/OES. III. RESULTS AND DISCUSSION A. Mineral Phase in Tailings As shown in Fig. 1, the zinc mine tailings was crystalline and the main mineral phase was dolomite CaMg(CO3)2 with strongest p

18、eak d value 2.88 or 2θ angle 31.03°. Besides dolomite, there was trace pyrite FeS2 in the mine tailings, too. Intensity(cps)Dolomite CaMg(CO3)2 PDF05-062220 40 60 802theta(o)Pyrite FeS2 PDF01-1295Figure 1. XRD sp

19、ectrum of zinc mine tailings 36___________________________________ 978-1-61284-478-7/11/$26.00 ©2011 IEEE and 25.4% in carbonate phase, 32.2% Cd in sulfide phase and 36.0% in carbonate phase and 43.4% Cr in sulfid

20、e phase and 26.2% in carbonate phase. D. Integrated Utilization Plan for Tailings In view of the rather low concentration of pyrite in the zinc mine tailings, it will be very hard to separate dolomite and pyrite from

21、tailings by beneficiation technology. Only an integrated utilization process seems to be feasible for the zinc mine tailings due to its complicated metal component and occurrence. To divide Ca and Mg effectively, to r

22、educe residue, to treat wastewater properly and especially to minimize content of heavy metals in discharge to fit effluent standard are the key points for the suggested integrated utilization plan for the zinc mine

23、tailings. Pyrite is slightly soluble in diluted HCl solution in room temperature while dolomite is soluble in it. In the first step of this integrated plan, diluted HCl solution is to be used to treat these tailings,

24、 and dolomite will dissolve into solution, leaving most of pyrite as residue. Seeing that almost 86.6% tailings is dolomite phase, great part of tailings will dissolve in diluted HCl solution. At the same time, other

25、metal ions including heavy metals existed in carbonate, sulfide or other mineral phases in the tailings will transfer into the solution or remain as residue. Metal ions in solution have their particular solubility pr

26、oduct, hence they will form precipitation in proper pH value, for example, precipitation pH value for Fe3+ is nearly 3.2, and for Mg2+ 11.2 and for Ca2+ 13.9 [5]. Based on the precipitation feature, in the second stag

27、e of this plan dissolved metal ions will form precipitation step by step through adjusting pH value with ammonia water. As a result, Ca and Mg are separated as different hydroxides phases, and can be converted into ot

28、her product if needed [5-6]. To deal with solid residue and waste water containing heavy metals with reasonable efficiency and cost, is of great importance to make this integrated utilization plan feasible. For heavy

29、metals in solid residue, to recovery valuable resource in pyrometallurgy or hydrometallurgy way, or to be buried in highly controlled landfills after solidification, are two common disposal methods, which will be plot

30、ted in the utilization scheme. As for heavy metals in liquid phase, recycling of wastewater is preferred, and many techniques such as chemical precipitation, ion exchange, adsorption, membrane filtration and electroch

31、emical methods can then be employed to treat this kind of wastewater [7]. Chemical precipitation is a traditional technique for heavy metal wastewater treatment with its simplicity process and inexpensive capital cost

32、, however, this process is usually suitable to treat wastewater with high concentration of heavy metal ions. To combine chemical precipitation and other treatment technology is suggested in the utilization plan to en

33、sure effluent reaching standard finally. Lab experiments are conducting to obtain first hand information based on this integrated acidification utilization plan. IV. CONCLUSIONS 1. Mineral phases of the zinc mine tai

34、lings were 86.6% dolomite with trace pyrite. 2. Occurrence of Zn was complicated with 37.2% in sulfide phase, 24.4% in residual phase, 18.2% in carbonate phase and 15.2% in sorption phase. Iron in the tailings mainly

35、 existed in sulfide phase (44.5%) and in residual phase (54.2%). 3. Major heavy metal in the mine tailings was Pb with concentration 348 μg/g and nearly 60% Pb lay in sulfide phase. 4. An integrated acidification uti

36、lization technology was suggested for the zinc mine tailings based on the mineral phase and occurrence of metals. REFERENCES [1] D. Wu, C. X. Li and Q. Deng, “Evaluation on soil heavy metal pollution around typical le

37、ad and zinc mining areas in Guizhou”, Guizhou Agr. Sci., vol. 38, pp. 92-94, 2010. [2] K. Zheng, L. Li, “The status of heavy metal pollution and its control in the Pb and Zn mining districts of China”, J. Anhui Agr. Sc

38、i., vol. 37, pp. 14837-14839, 2009. [3] Y. G. Yang, C.Q. Liu and G.P. Zhang, “Heavy metal accumulations in environmental media induced by lead and zinc mine development in northwestern Guizhou province, China”, Bull.

39、Miner. Petro. Geochem., vol. 22, pp. 305-309, 2003. [4] A. Tessier, P.G.C. Campbell and M. Bisson, “Sequential extraction procedure for the speciation of particulate trace metals”, Anal. Chem., vol. 51, pp. 844-851, 1

40、979. [5] W.G. Yao, H.W. Ma, X.Q. Jiang and Y.Q. Liu, “Preparation of light- weight magnesium oxide and calcium carbonate from dolomite by acidification: an experimental study”, Geosci., vol. 25, pp. 151-156, 2011. [6]

41、S. N. Bian, “Exploitation and comprehensive utilization of dolomite ore”, Min. Eng., vol. 8, pp. 4-6, 2010. [7] F. L. Fu, Q. Wang, “Removal of heavy metal ions from wastewaters: a review”, J. Environ. Manage., vol. 92,

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