【作者】 常冬寅；

【导师】 陈天虎；

【作者基本信息】 合肥工业大学 ， 矿物学、岩石学、矿床学， 2014， 博士

【摘要】 矿产资源开采,尤其是金属矿产资源开采过程中,废石、尾矿、冶炼渣、矿坑排水、选冶废水、废气、烟尘中的重金属元素都是矿区环境的重要污染源。矿山固体废物通过风化、氧化、淋滤等作用导致固体中重金属元素逐渐释放,使地表水、土壤和地下水受到污染。水体和土壤中的重金属污染物不能被微生物分解,只能被富集和累积,所以,当重金属污染物累积到一定程度时,不但会影响生态物种,还会影响生态系统的结构与功能,污染农作物、水产品等；另外,矿山废弃地中以各种化学状态或化学形态存在的重金属,在进入环境或生态系统后就会存留、积累和迁移,通过直接接触或食物链,从环境、粮食或蔬菜中富集到人体内,直接或间接的威胁人类健康。据不完全统计,截至2011年底,安徽省查明储量的金属矿山共960余处,累计查明储量129.9亿吨,其中基建和开采矿区500余处,停采和关闭矿区250处,未利用矿区210余处,对于金属矿山的修复治理尤其是重金属污染的修复治理工作,也就变得尤为重要。在金属矿产资源分布较多的六安、马鞍山、合肥、铜陵、池州等地,矿山废弃地中的重金属污染及酸性矿山废水相对来说也比较严重,主要的重金属污染元素为Cu、Cd、Hg、Pb、Zn、Cr等,尤其是Cd元素,其毒性最大,多年来一直是专家学者及政府关注的焦点。本课题组的前期研究表明,沉积型凹凸棒石粘土对部分重金属离子具有很好的去除效果；氢气还原针铁矿制备铁粉对降解硝态氮、亚硝态氮和除磷具有很好的性能,也表现出优越的还原活性；蒙脱石对重金属离子的去除效果也广为研究,并表现出很好的吸附效果。所以,为了研究矿物吸附法对去除重金属离子的作用效果,拓展凹凸棒石粘土、天然针铁矿和蒙脱石的应用领域,充分挖掘矿物的材料属性,为环境保护开发新的功能材料,进而更有效的防治矿山重金属污染,促进经济、社会、生态环境可持续协调发展。本文分析了安徽省矿产资源开发利用现状、安徽省金属矿产资源及矿山废弃地的分布特征,根据可能产生的重金属污染,研究了三种铁粉、两种凹凸棒石粘土和两种蒙脱石对八种重金属离子的去除效果及可能的去除机理。首先对安徽省矿产资源开发利用现状,尤其是金属矿产资源的开发利用现状数据进行了整理,利用Arcgis软件分析,研究了安徽省矿产资源及矿山废弃地的分布特征,确定了不同类型矿山废弃地修复治理的重点区域。重点结合矿产资源开采过程中和开采后可能产生的重金属污染,研究了天然针铁矿氢还原铁粉、合成针铁矿氢还原铁粉和商用铁粉、沉积型凹凸棒石粘土、热液型凹凸棒石粘土、钠基蒙脱石和钙基蒙脱石对模拟矿山重金属污染(Pb2+、Zn2+Cu2+、Co2+、Cd2+、Hg+、Ag+、Cr6+)的去除效果。实验中运用伪二级吸附动力学模型分析、Langmuir和Freundlich吸附等温式拟合、吸附热力学分析考察了吸附时间、重金属初始浓度、温度等因素对七种材料去除八种重金属离子的影响；并利用X-射线衍射(XRD)、场发射扫描电镜(FE-SEM/EDS)、透射电镜(TEM)、红外光谱(FT-ATR、FT-IES)、热分析(TG/DTG)、比表面积和孔结构等分析表征手段,对反应前后材料进行表征,探究了各种材料的晶体结构、成分、形貌特征及其去除重金属离子的可能机制。主要成果总结如下：1.通过对安徽省矿产资源开发利用情况进行分析,发现从累计查明储量分布情况来看,金属矿产资源储量从大到小依次为六安、马鞍山、合肥、铜陵、池州等,大部分为长江沿岸区域,这也是安徽省矿山废弃地分布较广以及重金属污染及酸性矿山排水的重点防治区域。2.通过XRD、TEM、SEM、TG/DTG等技术表征了天然针铁矿氢还原铁粉、合成针铁矿氢还原铁粉和商用铁粉。结果显示,氢还原天然针铁矿可制备纳米级铁粉,氢还原合成针铁矿可制备百纳米级铁粉,商用铁粉为微米级铁粉。3.研究了三种铁粉去除重金属离子的效果,考察了时间、初始浓度、温度的影响。对八种重金属离子的去除效果来说,HG-ZVI>NG-ZVI≈CIP。HG-ZVI在去除各种重金属离子上都优于NG-ZVI和CIP,NG-ZVI在去除Cr6+上优于CIP,但去除Cu2+差于CIP,分析认为比表面积是制约CIP处理效果的主要因素,天然针铁矿中含有的杂质、铁的类质同相替代以及颗粒团聚是制约NG-ZVI的主要因素。4.研究了三种铁粉去除八种重金属离子的可能机理。结果表明,三种铁粉对Cu2+均具有很好的还原作用,CIP可将Cu2+迅速还原为Cu单质,NG-ZVI、HG-ZVI先将Cu2+还原为Cu+,再进一步还原为Cu0;NG-ZVI和HG-ZVI可迅速将Ag+还原为Ag单质。HG-ZVI可降解Cr6+为Cr3+,从而降低毒性。三种铁粉对Pb2+、Zn2+、Co2+、Cd2+四种离子的去除主要通过吸附或沉淀作用实现。5.通过XRD、FE-SEM/EDS、FT-ATR及FT-IES等技术手段表征了沉积型凹凸棒石粘土和热液型凹凸棒石粘土。结果表明,沉积型凹凸棒石粘土含有少量的石英和白云石杂质,且为富Fe凹凸棒石粘土,具有高比表面积和总孔体积：热液型凹凸棒石粘土纯度高,基本不含杂质,比表面积和总孔体积远低于沉积型凹凸棒石粘土。6.研究了沉积型凹凸棒石粘土和热液型凹凸棒石粘土去除八种重金属离子的影响。结果表明,沉积型凹凸棒石粘土对重金属离子的去除远优于热液型凹凸棒石粘土,但两者对Cr6+的去除效果很差。分析认为,沉积型凹凸棒石粘土的富铁特性、高比表面积、总孔体积及短棒形貌为其去除重金属离子提供了有利条件,如吸附位、断面质子化诱导金属离子沉淀。吸附机理研究表明,沉积型凹凸棒石粘土主要通过诱导金属离子沉淀和吸附作用去除重金属离子。7.通过XRD、TG/DTG、BET等技术表征了钠基蒙脱石和钙基蒙脱石。结果表明,钙基蒙脱石纯度高于钠基蒙脱石,钠基蒙脱石中含有少量的长石和石英；钙基蒙脱石层间水多于钠基蒙脱石,层间距大于钠基蒙脱石；钙基蒙脱石比表面积和总孔体积均比钠基蒙脱石大。8.研究了钠基蒙脱石和钙基蒙脱石去除八种重金属离子的影响。结果表明,钠基蒙脱石对重金属离子的去除效果优于钙基蒙脱石,但两者对Cr6+的去除效果很差。分析认为,效果差异性与两种蒙脱石去除重金属离子的机理有关。通过吸附前后溶液pH动态检测、溶液Na+或Ca2+浓度变化及吸附后固体XRD表征,结果表明,钙基蒙脱石主要通过交换作用实现去除重金属离子,钠基蒙脱石主要通过交换作用和诱导沉淀作用去除重金属离子。9.三种材料去除重金属离子的研究可知,铁粉主要通过吸附、共沉淀作用去除Pb2+、Zn2+、 Co2+、Cd2+、还原作用参与HG-ZVI去除Cu2+、Ag+和Cr6+的过程,从而去除或降低其毒性,其作用机理与蒙脱石和凹凸棒石粘土不尽相同。凹凸棒石粘土以诱导沉淀和吸附作用、蒙脱石主要以诱导沉淀和交换作用去除重金属离子,蒙脱石去除效果优于凹凸棒石粘土。更多还原

【Abstract】 Heavy metal derived from mine tailing, mine processing and metallurgy, and dust during the mining is the main pollution in mining area. Heavy metal can release from minerals after weathering, oxidation, and leaching and then step into surface water, soil, and ground water by irrigation, sedimentation, and permeation, which would result in the pollution of soil and groundwater. As we known, heavy metals are hard to be decomposed and easy to enrich and accumulate. This behavior will seriously affect the ecological species, the structure and function of ecosystem, and pollute the crops and aquatic products. In addition, heavy metals existing as different chemical state will indirectly or directly threaten human beings’life by food chains after they step into environments.According to the incomplete statistics, the quantity of metal mine identified metal mineral occurrence of Anhui province comes to960; identified storage comes to12.99billion ton, in which mining reaches500, stopped or closed comes to250, and unmining comes to210. Therefore, it is becoming more and more important to prevent and cure the heavy metal pollution. The metal mines mainly distribute in Luan, Maanshan, Hefei, Tongling, Chizhou city, etc, where Cu2+、Cd2+、Hg+、 Pb2+、Zn2+、Cr6+are found as the main metal pollutions and have been attracting the attention of experts, scholars, and governments.Sedimentary palygorskite is documented having a good adsorption capacity to heavy metals; iron powder prepared by reducing goethite possesses great reductive activity to nitrate and nitrite, and good adsorption capacity to phosphate. In addition, montmorillonite is also proved to be a good adsorbent to removal heavy metals. Therefore, in order to study the efficiency of mineral adsorption to remove heavy metals; to broaden the application field of palygorskite, goethite and montomorillonite, and explore the material properties of minerals; to explore new materials for environmental protection to effectively prevent and cure heavy metal pollutions of mining area and improve the sustainable development of economy, society and ecological environment. In the present work, we analysized the status of exploitation and utilization of Anhui metal mine resource and its distribution characteristics. Based on the possible pollution types of heavy metal, we studied the efficiency of three kinds of iron powders, two kinds of palygorskites and two kinds of montomorillonites to remove eight kinds of heavy metal ions from aqueous solution and the removal mechanism.In this thesis, the status of exploitation and utilization of Anhui mine resources, especially for the metal mine resources, was analysized. The distribution characteristics of Anhui mine resources and mining wasteland were drawn using Arcgis software and the key zone of prevention and cure was confirmed. What was mostly important, the efficiency of iron powder prepared by reducing natural goethite and synthetic goethite, commercial iron powder, sedimentary palygorskite, hydrothermal palygorskite, Na-montomorillonite and Ca-montomorillonite to remove Pb2+、Zn2+、 Cu2+、Co2+、Cd2+、Hg+、Ag+、Cr6+was investigated based on the analysis results above. In addition, pseudo-second-order kinetic model, Langmuir and Freundlich isotherms, and adsorption dynamic were used to analysize the effect of adsorption time, heavy meatal initial concentration and adsoption temperature on removal of heavy metals using seven kinds of materials. The solution pH of some materials before and after adsoption was measured. Eventually, XRD, FE-SEM/EDS, TEM, FT-ATR, FT-IES, TG/DTG, BET, etc, were utilized to characterize the seven materials before and after adsorption, in order to study the the removal mechanism. The main conclusions obtained from the analysis and experiments are listed as follows:1. Based on the analysis of the status of exploitation and utilization of Anhui mine resources, it can conclude that the order of the metal mine storage is Luan city>Maanshan city>Hefei city>Tongling city>Chizhou city>Huangshan city. These city was speculated as the key prevention and cure area of heavy metal pollution.2. Iron powder prepared by reducing natural goethite (NG-ZVI) and synthetic goethite (HG-ZVI), and commercial iron powder (CIP) were characterized using XRD, TEM, SEM, TG/DTG, etc. The results showed that NG-ZVI with a size of nano scale iron powder and HG-ZVI with a size of several hundreds of nanometer were prepared by reducing goethite in hydrogen. The CIP was a kind of micron scale iron powder.3. The effect of adsorption time, initial concentration, adsorption temperature on removal of heavy metals using three kinds of iron powder was investigated. Totally, the order of removal efficiency was HG-ZVI>NG-ZVI≈CIP. The adsorption capacity of HG-ZVI to eight heavy metals was higher that of NG-ZVI and CIP. The adsorption capacity of NG-ZVI to Cr6+was higher than that of CIP, however, The adsorption capacity of CIP to Cu2+was higher than that of NG-ZVI. It was suggested that the surface area was key factor limiting the activity of CIP, and the impurity, isomorphous substitution and aggregation were the factors affecting the activity of NG-ZVI.4. The removal mechanism showed that three kinds of iron have a reductive activity to Cu2+. Cu2+was reduced into Cu0by CIP, Cu2+was reduced into Cu+and then into Cu0by NG-ZVI or HG-ZVI. NG-ZVI and HG-ZVI can reduce Ag+into Ag0quickly, In addition, Cr6+can be degraded into Cr3+by HG-ZVI, which decreased the toxicity. Adsorption or/and precipitation is/are regarded as the main mechanism for three kinds of iron powder removal of Pb2+、Zn2+、 Co2+、Cd2+.5. Sedimentary palygorskite (SPG) and hydrothermal palygorskite (HPG) were characterized using XRD, FE-SEM/EDS, FT-ATR, FT-IES, etc. The results showed that SPG contained some quartz and dolomite, was kind of Fe-substituted palygorskite, and possessed large surface area and total pore volume. HPG was highly pure, however, had a lower surface area and total pore volume than that of SPG6. The effect of adsorption time, initial concentration, adsorption temperature on removal of heavy metals using SPG and HPG was investigated. The results showed that HPG had a better adsorption capacity to selected heavy metals than that of SPG. Nevertheless, the both palygorskite has a bad capacity to Cr6+. It was suggested that the characteristic of Fe substitution, large surface area and morphology of SPG provided benefit conditions for removal of heavy metals. The induced metal precipitation and adsorption were regarded as the main mechanism for removal of heavy metals by SPG.7. Na-montomorillonite (Na-M) and Ca-montomorillonite (Ca-M) were characterized by XRD, TG/DTG, and BET, etc. The results showed that Ca-M was purer than that of Na-M which contained some quartz and feldspar. The interlayer water of Ca-M was more than that of Na-M. The interlayer space, surface area and total pore volume of Ca-M were also larger than that of Na-M.8. The effect of adsorption time, initial concentration, adsorption temperature on removal of heavy metals using Na-M and Ca-M was investigated. The results showed that Na-M had a better adsorption capacity to selected heavy metals than that of Ca-M. Nevertheless, the both montomorillonite had a bad capacity to Cr6+, which was contributed to the different removal mechanism. The solution pH before and after adsorption was measured at a short interval. The adsorbed Na-M and Ca-M were characterized using XRD and the concentration of Na+and Ca2+before and after adsorption was detected using ICP-MS. The results showed that ion exchange was the mian mechanism for removal of heavy metals by Ca-M; however, induced metals precipitation was regarded as the other mechanism for removal of heavy metals besides ion exchange.9. All the results showed that adsorption and precipitation were proposed as the mian mechanism for removal of Pb2+、Zn2+、Co2+、Cd2+by iron powder. Besides, reduction participated the removal process of Cu2+、Ag+and Cr6+by HG-ZVI. The removal mechanism of iron powder was different from that of montomorillonite and palygorskite. Adsorption and induced precipitation were suggested as the mian mechanism of palygorskite, while ion exchange and induced precipitation were regarded as the mechanism of montomorillonite. In addition, the removal capacity of Na-M was higher that that of SPG.更多还原