贵州中北部燃煤型砷中毒地区煤中砷的赋存状态研究

Abstract

贵州中北部存在着高砷煤并引起环境和健康问题,对这些地区的煤进行了中子活化分析(InAA)、电子探针(EMPA)、能谱扫描电子显微镜(SEM-EdX)、低温灰化(lTA)、X射线衍射(Xrd)、X光吸收精细结构(XAfS)和连续淋滤实验分析,综合研究了这些煤中砷的赋存状态。结果表明不同煤中砷具有不同的赋存状态。在部分样品中砷主要以无机砷的形式存在,而在其它样品中砷主要以有机砷的形式存在。除了黄铁矿和毒砂外,SEM-EdX结合lTA和Xrd发现硫酸盐、粘土也不同程度含有砷。XAfS显示煤中的砷主要以AS5+的形式存在。连续淋滤实验表明在样品zJ-1中超过50%的砷不能被淋滤出来,而在另外两个样品(zJ-8和rH-5b)中绝大部分的砷被淋滤出来。综合分析表明一些煤中以+5价存在的砷主要与有机质结合。煤中如此高的砷及其主要与有机质结合的现象是很罕见。

High As-bearing coals were found in northwestern Guizhou Province,the use of high As-bearing coals would cause environmental and health problems.Coal samples from these areas have been analyzed with instrument neutron activation analysis(INAA),electron microprobe analyzer(EMPA),scanning electron microscopy with an energy dispersive X-ray analyzer(SEM-EDX),low temperature ashing(LTA),X-ray diffraction analysis(XRD),X-ray absorption fine structure(XAFS),and sequential leaching experiment.The modes of occurrence of arsenic in high As-coals were discussed.Arsenic has different modes of occurrence in different samples.Arsenic is present mainly as inorganic As in some samples,and mainly as organic As in other samples.Besides pyrite and arsenopyrite,SEM-EDX combined with LTA and XRD revealed that sulfates and clay also contain arsenic.XAFS showed that arsenic mainly exists in the form of As5+.Analytical results of leaching experiment showed that more than 50 % of arsenic is present in residual solid in sample ZJ-1,but most arsenic is leached out in samples ZJ-8 and RH-5b.Analysis of the samples indicated that arsenic exists mainly in the form of As5+,and is combined with compounds in the organic matrix.