Recovering Cu, Pb and Zn in iron tailings by chlorination roasting with CaCl2
CAI Haili, NING Xunan,, BAI Xiaoyan, LU Xingwen, LI Riwen, SHEN Wen Guangzhou Key Laboratory Environmental Catalysis and Pollution Control, Institute of Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China
Abstract:In view of the resource utilization of iron tailings, the iron tailings were chlorination roasted by adding CaCl2. X-ray diffraction analysis and thermogravimetric analysis were used to analyze CaCl2, and atomic absorption spectrometry and X-ray fluorescence were used to analyze the roasted slag and collected materials. The CaCl2 action mechanisms under nitrogen and dry air conditions were investigated, the effects of roasting atmosphere and temperature on the volatilization rates of Cu, Pb and Zn in iron tailings, as well as the effects of different collection methods on the collection rates were studied. The results show that the CaCl2 reaction could generate Ca(OH)Cl and release Cl in nitrogen atmosphere, while CaCl2 reacted with O2 or H2O to release Cl in the dry air. The order of heavy metal volatilization rates was Pb>Cu>Zn, and the rates increased with the increase of temperature. For Pb volatile effect, nitrogen atmosphere was better than air atmosphere, which was contrary for Zn volatile effect, while roasting atmosphere has little influence on Cu volatile effect. In nitrogen atmosphere, the heavy metals in the flue gas were more easy to be collected by condensation, while in the circumstance of dry air, the heavy metals in the flue gas were more easy to be recovered by wet-washing and absorption. After chlorinated roasting, large part of Cu, Pb and Zn in iron tailings volatilized. Key words:metal ore/ iron tailings/ chlorination roasting/ volatilization rate/ heavy metal/ solid waste.
图4不同气氛和温度下重金属Cu、Pb、Zn的挥发率和冷凝液浓度 Figure4.Vaporization percentage and condensate concentration of heavy metals under different temperatures and atmospheres
表1铁尾矿中重金属浓度 Table1.Heavy metal concentration in iron tailings
mg·kg?1
Cu
Pb
Zn
Cr
Cd
4 568.00
1 761.68
2 518.70
85.81
2.81
mg·kg?1
Cu
Pb
Zn
Cr
Cd
4 568.00
1 761.68
2 518.70
85.81
2.81
下载: 导出CSV 表2干空气和氮气条件下不同温度热处理后的冷凝液主要成分 Table2.Main compositions of condensate after heat treatment under different temperature in dry air and N2 atmosphere
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Guangzhou Key Laboratory Environmental Catalysis and Pollution Control, Institute of Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China Received Date: 2018-12-31 Accepted Date: 2019-03-27 Available Online: 2019-09-17 Keywords:metal ore/ iron tailings/ chlorination roasting/ volatilization rate/ heavy metal/ solid waste Abstract:In view of the resource utilization of iron tailings, the iron tailings were chlorination roasted by adding CaCl2. X-ray diffraction analysis and thermogravimetric analysis were used to analyze CaCl2, and atomic absorption spectrometry and X-ray fluorescence were used to analyze the roasted slag and collected materials. The CaCl2 action mechanisms under nitrogen and dry air conditions were investigated, the effects of roasting atmosphere and temperature on the volatilization rates of Cu, Pb and Zn in iron tailings, as well as the effects of different collection methods on the collection rates were studied. The results show that the CaCl2 reaction could generate Ca(OH)Cl and release Cl in nitrogen atmosphere, while CaCl2 reacted with O2 or H2O to release Cl in the dry air. The order of heavy metal volatilization rates was Pb>Cu>Zn, and the rates increased with the increase of temperature. For Pb volatile effect, nitrogen atmosphere was better than air atmosphere, which was contrary for Zn volatile effect, while roasting atmosphere has little influence on Cu volatile effect. In nitrogen atmosphere, the heavy metals in the flue gas were more easy to be collected by condensation, while in the circumstance of dry air, the heavy metals in the flue gas were more easy to be recovered by wet-washing and absorption. After chlorinated roasting, large part of Cu, Pb and Zn in iron tailings volatilized.
采用热重分析法(NETZSCH TG 209 F1，德国NETZSCH公司)测定无水氯化钙(CaCl2，AR)的热重变化(升温速率：10 ℃·min?1；气氛：干空气和氮气(99.9%))；采用X射线荧光光谱(XRF)(EDX-7000，日本岛津公司)鉴定热处理后的铁尾矿残渣的主要成分；采用X射线衍射仪(XRD)(D8 ADVANCE，德国Bruker公司)进行结晶化合物的测定；用6 mL 65%硝酸(AR，HNO3)、2 mL 35%盐酸(AR，HCl)和3 mL 40%氢氟酸(AR，HF)在微波消解仪(MARS6，美国CEM公司)中消解后，用纯水稀释至50 mL，采用火焰原子吸收分光光度计(Z2000，日本日立公司)测定重金属的浓度。
为探究湿法收集方式对氮气和干空气焙烧气氛下的烟气中各元素的回收效果，本研究对烟气端连续5个盛有200 mL 5%稀硝酸的吸收瓶中重金属浓度进行检测，结果如图6所示。可以看出，干空气条件下吸收瓶中金属浓度较高。第3个及以后的吸收瓶基本未检测到各金属元素，由此可见，挥发出的各金属元素在前2个吸收瓶中基本被完全吸收。由第1个吸收瓶中各金属元素的浓度可以看出，吸收瓶中金属Zn、Cu、Pb浓度较高，而Cd、Fe元素浓度很低，这是因为铁尾矿中本身Cd含量较低，而Fe元素属于难氯化挥发金属。整体对比发现，干空气气氛下氯化焙烧的挥发物更易于被湿法洗涤收集。
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