摘要
煤矸石长期堆存将对周边环境造成酸性污染和重金属含量超标。为研究煤矸石山发生氧化自热对酸性污染物降雨淋溶释放特性的影响机理,以山西省阳煤集团煤矸石为研究对象,建立了自动温控喷淋系统,通过对不同温度煤矸石进行动态淋溶实验,研究了淋溶液中pH值、电导率(EC)值、氧化还原电位(ORP)和硫酸盐(SO_4^(2-))含量的淋溶规律,并对淋溶前后煤矸石矿物组成进行半定量分析。结果表明:风化煤矸石中含有大量硫酸盐等可溶性组分,且酸性组分含量大于碱性组分和黏土矿物组分中和量总和,初期润湿液SO_4^(2-)含量超过地下Ⅲ类水指标,可看作高度矿化水,呈弱酸性和氧化状态,但氧化性未超过一般界定氧化性土壤的值(400 mV);随着累计淋溶时间延长,淋溶液pH值先增大后减小并最终趋于稳定,在t=3 h达到最大值为7. 34～8. 03,SO_4^(2-)含量和EC值先急剧减小后趋于稳定,稳态值分别约为2 500 mg/L和2 mS/cm,ORP在325. 9～435. 2 mV波动;随着温度升高(50～200℃),淋溶液稳态pH值(pH_s)和煤矸石剩余黄铁矿含量先减小后增大,150～200的pH_s值小于5.79,SO_4^(2-)含量和石膏相对质量分数先增大后减小,ORP波动性增强,相对标准偏差RSD由9. 54%增大到10.06%,EC值受温度影响不显著;淋溶液各项指标均在150℃条件下取得极值,pH_(s,min)为4. 98,呈较强酸性;ORP_(max)为435. 2 mV,呈强氧化态。由此可得:煤矸石中产酸物质氧化作用可分为风化氧化和自热氧化,主要受环境温度、含水量和与空气接触程度的综合影响;煤矸石自热氧化造成的酸性污染演变过程是由碱性组分、含氮物质和氧化产生的酸性组分共同决定的,且3种组分淋溶释放速率经长期堆存后逐渐趋于稳定。本研究解释了煤矸石中黄铁矿氧化产酸受环境温度的影响机制,为自热煤矸石山降雨淋溶造成酸性污染动力学演变预测提供依据。
Long-term stockpiling of coal gangue would cause acidic pollution at surrounding area and heavy metal content to exceed the standard.The coal gangue was obtained from Yangquan coalmine in Shanxi to study the mechanism of the influence that coal gangue’s self-heating oxidation has on the leaching and release characteristics of acidic pollutants.The dynamic leaching experiments were carried out in an automatic temperature-controlled leaching system.The leaching rules of leaching solutions’pH values,electrical conductivities(ECs),oxidation-reduction potentials(ORPs)and sulfate contents(SO4^ 2-)were investigated at different temperatures.Also,the respective mineral components of coal gangue samples before and after the leaching operations were analyzed semi-quantitatively.The result shows that weathered coal gangue contains a great quantity of soluble sulfates,and the content of acidic components is greater than the sum of alkaline and argillaceous mineral components.The sulfate content of wetting solution exceeds the subsurface classⅢwater index at the beginning of the experiment,so it can be regarded as highly mineralized water.Besides,the wetting solution assumes weak acidity and oxidation state,but the oxidizing property does not exceed the value of the general defined oxidizing soil(400 mV).As time goes on,however,the pH value will increase at first,then decrease and tend to be stable eventually.At t=3 h,the pH value reaches a maximum of about 7.34-8.03.The sulfate content and EC value will decrease sharply at first and then stabilize at around 2 500 mg/L and 2 mS/cm respectively,while the ORP will be fluctuating within the range of 325.9 mV and 435.2 mV.When temperature rises from 50 to 200℃,the steady state pH value(pH s)of solution and the residual pyrite content in coal gangue will decrease at first and then increase,and pH s values are maintained less than 5.79 at 150℃to 200℃.The sulfate and gypsum contents will increase at first and then decrease while the volatility of ORP will increase gradually as temperature increases,and the relative standard deviation(RSD)increases from 9.54%to 10.06%.The EC value is not significantly affected by temperature.All these indexes will obtain their extreme values at 150℃,the extreme values of pH s,min and ORP max are 4.98 and 435.2 mV,respectively,which present a strong acidity and strong oxidation state.Therefore,the oxidation of acid-generating substances in coal gangue can be divided into weathering oxidation and autothermal oxidation,which are mainly affected by the combination of ambient temperature,water content and degree of air contact.The acid pollution evolution process caused by the autothermal oxidation of coal gangue is determined by alkaline components,nitrous substances and acidic components produced by oxidation,also,the leaching release rate of three components gradually tend to be stable after long-term storage.This paper explains the mechanism of temperature’s influence on the acid production of pyrite oxidation in coal gangue,which could provide a research basis for forecasting the dynamic evolution of self-heated coal gangue hills’acidic pollution caused by rainfall leaching and infiltrating.
作者
冉洲
刘文礼
潘永泰
刘文昌
高自然
赵英霄
RAN Zhou;LIU Wenli;PAN Yongtai;LIU Wenchang;GAO Ziran;ZHAO Yingxiao(School of Chemical and Environmental Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;Yangquan Coal (Group) Co.,Ltd.,Yangquan 045000,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2019年第4期1239-1246,共8页
Journal of China Coal Society
基金
中央高校基本科研业务费专项资助项目(2010YH11)
关键词
煤矸石
温度
动态淋溶
酸性污染物
黄铁矿
coal gangue
temperature
dynamic leaching
acidic pollutant
pyrite
