煤中重金属元素的溶出潜力及其影响因素

水-煤相互作用是影响煤矿矿井水水质的重要因素之一。为揭示煤中重金属元素的溶出机制,利用连续化学提取、浸溶实验等方法分析了煤中10种重金属元素赋存形态,量化了水-煤相互作用过程中重金属元素平均溶出浓度,梳理了影响煤中重金属元素溶出的内在和外在因素。结果表明:①煤中的Hg和Cr主要以残渣态存在; Mo主要以残渣态和可氧化态存在; Ni、Cu、Co、Zn和Cd主要以残渣态、可氧化态和弱酸提取态存在; As和Pb主要以残渣态、可氧化态和可还原态存在。②各重金属元素的平均溶出浓度从高到低依次为Zn、Cu、Ni、Cr、Co、Mo、As、Cd、Pb、Hg,对应浓度分别为25.73、25.21、18.12、13.22、8.10、4.31、0.77、0.60、0.50、<0.10 μg·L^-1。③影响煤中重金属元素溶出的内在因素包括元素赋存含量、元素赋存状态和存在形式、煤炭产酸性能、水体Eh值等; 外在因素包括氧暴露条件、水-煤相互作用时间等。在内在和外在因素的共同影响下,导致了不同地区煤中重金属元素溶出特征具有较大差异。

Dissolution Potential of Heavy Metal Elements in Coal and Its Influence Factors

Water-coal interaction is an important factor affecting the water quality of coal mines. Using the analysis methods of continuous chemical extraction and leaching test, the existing forms of 10 heavy metal elements in coal were analyzed, the average dissolution concentrations of heavy metal elements in the process of water-coal interaction were quantified, and the internal and external factors affecting the dissolution of heavy metal elements in coal were sorted out. The results show that ① Hg and Cr in coal mainly exist in the residual fraction; the main existing forms of Mo are residual fraction and oxidisable fraction; the main existing forms of Ni, Cu, Co, Zn and Cd are residual fraction, oxidizable fraction and mild acido-soluble fraction; the main existing forms of As and Pb are residual fraction, oxidisable fraction and reducible fraction. ② The heavy metal elements in descending order of average dissolution concentration are Zn(25.73 μg·L^-1), Cu(25.21 μg·L^-1), Ni(18.12 μg·L^-1), Cr(13.22 μg·L^-1), Co(8.10 μg·L^-1), Mo(4.31 μg·L^-1), As( 0.77 μg·L^-1), Cd(0.60 μg·L^-1), Pb(0.50 μg·L^-1), Hg(<0.10 μg·L^-1). ③ The internal factors affecting the dissolution of heavy metal elements in coal, include element content, occurrence state and speciation, coal acid production performance, water Eh, etc.; the external factors include oxygen exposure condition, duration of water-coal interaction, etc. Under the combined influence of internal and external factors, the dissolution characteristics of heavy metal elements in coal in different regions are significantly different.