不同浸提工艺的金矿尾矿中砷的存在形态研究

摘要

Gold mine tailing is an important source of arsenic pollution. There are great differences in the arsenic forms of mine tailings formed by different smelting processes. Different arsenic form directly affects its migration and transformation in the environment. Confirming the existing form of arsenic is an important method in the study of repairing arsenic contamination sites. Based on mine tailings generated by two different leaching methods( flotation process and biological oxidation process ) for gold,pH meter and Eh meter was used to measure the physical properties of mine tailings( pH,Eh),X-ray Diffraction and X-ray Fluorescent to analyze the mineral phases and main compositions of the mine tailings and Electro-probe Microanalysis to analyze the arsenic existing form. The characterization result shows that the physical properties of flotation mine tailing and biological oxidation mine tailing change with the stacking environment. pH,Eh and pHPZC are almost equal,ie pH≈8. 5 and pHpzc≈8. 5. The choice of repair method is also restricted because both min tailings belong to the alkaline condition. For example,the electric repair method is only suitable for the acid condition but not for the two main mine tailings. Meanwhile the choice of repair reagent must be alkaline substance and iron oxide( hydroxide). The main mineral compositions of flotation mine tailing are quartz,dolomite and clay minerals and their chemical components are mainly Si and Al. The color of mine tailing is off-white. The arsenic content of this mine tailing is about 754 μg/g, mainly existing in the form of arsenopyrite( FeAsS). However,the main mineral type of biological oxidation mine tailing is gypsum. The main chemical components are Fe,Ca and S with a reddish-brown colour. The arsenic content is about 26350 μg/g. The existing forms of arsenic of this mine tailing are mainly arsenopyrite( FeAsS) and arsenic pentoxide( As2 O5 ). There are many differences in mineral phase,main chemical components and arsenic forms of two kinds of mine tailings because every procedure step of the two-gold leaching processes is different. Therefore,in the in-situ repair work of mine tailings,it should be considered that different methods of gold leaching will influence the piled-up environment of mine tailings and arsenic forms and should be taken into consideration in order to choose a more appropriate,cheap and efficient repair method and choice of reagents.%金矿尾矿是砷污染的重要来源，不同冶炼工艺形成的尾矿中砷的赋存状态有很大差异，不同的砷形态会直接影响其在环境中的迁移转化行为，确认砷的存在形态是修复砷污染场地研究中的重要内容。本文针对浮选法和生物氧化法两种不同浸金方法的尾矿，采用pH计和氧化还原电位自动测定仪测量尾矿的物理性质（ pH、氧化还原电位），采用X射线衍射和X射线荧光光谱分析尾矿的矿物物相和主要成分，电子探针分析砷的存在形态。表征结果表明，浮选法尾矿和生物氧化法尾矿的物理性质都会因堆置环境的变化而变化，其Eh、pH和零电荷点都大致相同，pH≈8.5，样品零电荷点（ pHPZC ）大约为8.5。由于两种尾矿都属于碱性环境，因此在修复方法的选择上也受到限制，如只适合在酸性条件下进行的电动修复法就不适用于这两种尾矿，修复试剂的选择也以碱性物质和铁的氧化物（氢氧化物）为主。浮选法尾矿的主要矿物类型为石英、白云石和黏土矿物，化学主要成分是Si和Al，尾矿呈灰白色，其中砷的含量约为754μg/g左右，主要以毒砂（ FeAsS）形式存在；而生物氧化法尾矿的主要矿物类型为石膏，化学主要成分是Fe、Ca和S，尾矿呈红棕色，其中砷的含量约为26350μg/g，主要以毒砂（ FeAsS）和五氧化二砷（ As2 O5）形式存在。两种浸金工艺每一道工序的不同，都会造成两种尾矿在矿物相、主要成分和其中砷存在形态上的差异。因此在进行尾矿原位修复工作时，应考虑不同浸金方法对尾矿堆置环境和砷存在形态的影响，从而选择出一种更加合适、廉价、高效的修复方法和试剂。