Separation of Sr, Nd, and U from Geological Samples Using Tandem Resin Column
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摘要:
Sr、Nd、U等同位素体系被广泛应用于地球表生过程中年代测定及物源示踪等研究, 高效地分离这些同位素体系,对于推广这些同位素方法的应用具有重要现实意义。若要同时分析地质样品中Sr、Nd、U三种元素的同位素,现有方法往往需要消解两份样品,一份用于Sr-Nd而另一份用于U的分离提纯。这种方法不但增加了样品用量,而且需要多次蒸干溶液转换介质,既延长了分离流程也增加了样品被污染的风险。为了提高样品利用率和分析效率,本文通过将树脂柱串联改进了分离流程,提出一种仅需消解一份样品,便可同时提取Sr、Nd、U三种元素的新方法。本方法中Sr的分离采用Sr特效树脂,包含Nd在内的稀土元素(REE)的分离采用AG50W-X8树脂,U的分离采用UTEVA特效树脂。实验中将三种树脂柱串联,采用3mol/L硝酸淋洗液淋洗,同步进行平衡树脂、上样、洗杂志,避免了蒸干操作。分离后的淋出液使用电感耦合等离子体质谱仪(ICP-MS)测试元素含量。结果表明:U的回收率接近99.9%,Sr的回收率超过90%,Nd的回收率超过80%;同时三种树脂柱串联的分离流程,主要基体元素(K、Ca、Na、Ba、Fe、Rb等)的去除率均超过99%,降低了对Sr、Nd、U高精度同位素分析的干扰;REE中的Sm则可以通过后续使用Ln树脂等进一步去除。此外,本文还交换了Sr特效树脂和UTEVA树脂的位置,比对两种不同串联顺序对分离结果的影响,结果表明两种树脂柱串联顺序对目标元素的分离并无显著影响。使用该方法可以有效地实现Sr、Nd、U的分离,在减少操作步骤的同时节省约一半的样品用量,提高了同位素分析效率。
要点(1) 将树脂柱串联,采用相同淋洗液同步进行平衡树脂、上样、洗杂质,避免了蒸干操作。
(2) UTEVA特效树脂和Sr特效树脂的上下串联顺序,对Sr、Nd、U元素的回收率并无显著影响。
(3) 多次重复回收利用树脂可能导致树脂柱失效,影响对目标元素的吸附能力,需要及时更换新树脂。
HIGHLIGHTS(1) The resin columns are connected in series, and the same eluent is used to balance the resin, load the sample, and wash the impurities simultaneously, avoiding the operation of evaporation to dryness.
(2) Reversing the column positions, UTEVA column and Sr column, has no effect on Sr, Nd and U separation and the column recovery.
(3) Multiple reuse of resin can lead to resin column lapse, affecting the adsorption capacity of the target element, thus new resins should be used in a timely manner.
Abstract:BACKGROUNDUranium-series nuclides are one of the three major radioactive decay systems, which are suitable for studying various geological processes at different time scales. In addition, 87Sr/86Sr and 143Nd/144Nd isotopes (Sr-Nd isotopes for short) are two commonly used isotopes, for rock dating, chemical weathering assessment and tracing sediment sources. In this case, the combination of Sr-Nd-U isotopes can provide more comprehensively knowledge of the element cycle on the earth's surface and deepen our understanding of the sediment "Source to Sink"processes.
Most previous studies involving the Sr-Nd-U isotopes have been established by separating Sr-Nd and U isotopes respectively. In this way, the digestion operation must be performed twice, one for separating Sr-Nd and the other for separating U. Alternatively, if only one sample is digested for measuring all three isotopes, between each element separation, the residue must be dried and dissolved in another solution so as to start a new column work. The former increases the amount of samples, which is not conducive to analysis of precious and trace samples; the latter adds additional drying operation, which is time consuming and increases the risk of sample loss and contamination.
OBJECTIVESTo establish a new Sr-Nd-U combined separation scheme. In this method, only one sample is dissolved, avoiding solution transfer between each separation, so as to reduce sample amount and improve the efficiency of separation and purification of Sr-Nd-U isotopes.
METHODSA new chromatographic scheme of separating Sr-Nd-U with one sample digestion using a tandem column scheme is presented. Three columns were overlain sequentially to separate Sr in Sr Spec column, Nd in AG50W-X8 column and U in UTEVA column. 3mol/L HNO3 was used to pre-condition, load the sample, and rinse the matrix. After rinsing the matrix, the tandem column was separated to 3 independent columns to elute the target elements (Sr, Nd, U) respectively.
As the connection sequence of different resin columns may interfere with the recovery of target elements, two different chromatographic schemes were compared. In Scheme 1, U column was placed on top of Sr column, while in Scheme 2 the positions of U column and Sr resin column were exchanged. In both schemes, the AG50W-X8 resin column was set at the bottom as the cationic resin can adsorb the most complex elements.
All separated elution was tested for element concentration using inductively coupled plasma-mass spectrometry (ICP-MS). The basalt standard sample (BCR-2) was used to examine the behavior and recovery of each element in the separation procedure.
RESULTSA total of 10 fractions were recovered from the tandem column scheme, among which fraction 1 represented the leachate recovered by loading samples and rinsing matrix from the tandem three columns. Fraction 2, 5 and 8 represented the leachate recovered by Sr Spec resin, AG50W-X8 resin and UTEVA resin respectively rinsing matrix after separation of the three columns. Fraction 3, 6 and 9 represented the leachate recovered by Sr, REE and U columns, which was Sr, Nd and U collection. Fraction 4, 7 and 10 represented the leachate from each resin recycle stage.
In either Scheme 1 or Scheme 2, most matrix elements (high content of K, Ca, Na, Mg, Al, Fe, Ti and P and low content of Rb, Hf and Th) were mainly concentrated in fraction 1. The elution rate of Na, Ti, Rb and Hf was up to 99%. The elution rate of K and Ca was slightly lower at about 85% and the elution rate of Fe was about 56%. Sr was mainly concentrated in fraction 3, which contained only a small amount of P and Ba. Nd was mainly concentrated in fraction 6, which also contained both Sm and Ce. U was mainly concentrated in fraction 9, which only contained a very small amount of P and Pb. The column recovery was almost 99.9% for U, 90% for Sr and over 80% for Nd.
The removal rate of major matrix elements (K, Ca, Na, Ba, Fe, Rb, etc.) exceeded 99%, which reduced interference with high-precision isotope analysis of Sr, Nd, and U. The recovery and purity of Sr, Nd, U were all quite high. A very small amount of P and Ba in fraction 3 had no interference with Sr isotopes (87Sr/86Sr). The Rb which was isomorphism of Sr was removed completely. With regard to Sm and Ce in fraction 6, previous studies had shown that 142Ce could not interfere with Nd isotope (143Nd/144Nd), and Sm could be further separated by Ln resin, so as not to affect Nd isotopic test. Fraction 9 contained nearly 100% U with no other elements.
The sequence of resin column splicing is a crucial consideration which may impact the element separation. Hence, the position of Sr Spec column and UTEVA column was exchanged to compare the influence of different column sequences on eluting target elements. Both Scheme 1 and Scheme 2 can effectively wash off most of the matrix elements, and the target elements Sr, Nd and U can be efficiently adsorbed on the resin. There is no significant difference on target element separation between the two different column sequences. This indicates that Sr Spec and UTEVA resins do not interfere with each other on the target elements.
CONCLUSIONSThe new chromatographic scheme of separating Sr-Nd-U with one sample digestion using a tandem column scheme can be used to quickly and efficiently separate Sr, Nd and U elements from silicate rock samples. The recovery rate for U, Sr and Nd is 99.9%, 92.5% and 82.1%, respectively, which meet the requirements of subsequent isotope analysis. This Sr-Nd-U combined separation method can be used to reduce the sample consumption by about 50%, which is beneficial to the analysis of precious and trace samples. Meanwhile, as no solution transfer is needed between each column separation, this method can also save time for column work and increase the efficiency of chemical separation. A new idea for Sr-Nd-U multi-isotope separation is provided. If the recovery of Pb in the fraction 4 of this chromatographic scheme can be improved in further studies, the application of this new method may be expanded to more fields in the future.
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Keywords:
- Sr /
- Nd /
- U /
- tandem resin column /
- column recovery /
- isotopic separation /
- inductively coupled plasma-mass spectrometry
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实现资源、环境和经济的协调发展是当下世界各国广泛关注的问题。发展绿色矿业、推进绿色勘查、建设绿色矿山,是促进资源、环境和经济协调发展的重要一环,也是适应新时期资源国情的重要举措。我国建设“绿色矿山”的理念始于2006年。2009年《全国矿产资源规划2008—2015》明确提出“绿色矿山建设”的目标任务和要求。2011年“发展绿色矿业”被纳入国家“十二五”规划。2015年将“发展绿色矿业,加快推进绿色矿山建设”列入国家生态文明建设的重要内容。2016年国家选取50个矿山开展绿色矿业发展示范区建设,提出了“绿色勘查”行动宣言[1]。随着绿色矿山、绿色矿业、绿色开采、绿色勘查等理念的相继提出,有关单位和行业协会也重点研发了相关标准。2018年6月,中国矿业联合会发布了《绿色勘查指南》,同年7月,自然资源部发布了《有色金属行业绿色矿山建设规范》(适用于铜矿、铝土矿、铅锌矿、钨矿、钼矿、锑矿、锡矿、镍矿、镁矿)等9项推荐性行业标准,这是我国第一部绿色矿山建设规范。但针对“能源金属”锂的绿色调查及矿山环境评价的研究成果鲜见报道。锂是新兴产业发展不可或缺的战略资源,被称为“21世纪的能源金属”[2]。四川西部甲基卡具有锂矿资源的区位优势,是我国重要的大型能源金属资源基地。大型资源基地的“绿色调查”,是在资源基地环境扰动最小的前提下,实现找矿部署最优化和生态环境保护最大化,通过创新方法,以地质背景与生态环境作为整体系统进行调查研究,通过地质学、水文地质学、工程地质学、地球化学、生态学、环境科学、数学等专业的跨学科综合调查成果来优化找矿部署,重视3S新技术新方法应用,适度调整或替代对环境影响大的勘查手段,快速恢复景观和健康的生态系统,以服务于保障大型资源基地生态安全,调整优化找矿突破工作布局。对于大型矿产资源基地的调查评价,其所面临的社会、政治、经济、环境等方面的问题远比一般性矿产地质调查复杂[3],已有部分重点开发项目由于环境问题处于停滞状态[4]。
我国专家学者已开展了大量绿色矿山及矿山环境评价指标的研究工作,取得了丰富的研究成果,可以归纳为两大类。第一类是针对政策、计划、各类矿产资源规划方案实施可能产生的环境影响评价指标的研究,主要集中在矿区可持续发展指标体系[5-11]、矿区生态文明指标体系[12]、绿色矿山指标体系[13-16]、战略性环评指标体系[17]、矿产资源安全评价指标体系[18-19]五个方面;第二类是针对不同景观区(如平原湿热带、干旱戈壁带),不同矿种(如硫化物多金属矿、钨锡矿、金银矿、镉矿等)矿区整体生态环境为重点指标系列的研究,主要包括矿区生态系统健康评价指标体系[20-21]、矿区生态环境质量评价指标体系[22-28]、矿区资源承载力评价指标体系[29-30]、矿区土壤质量评价指标体系[31-33]、环境影响评价指标体系[34-40]、矿产资源开发利用指标体系[41-46]。但未见针对高海拔特殊地貌区锂矿山绿色调查与环境评价指标体系研究成果的报道。
本文在分析川西大型锂资源基地的自然环境、实地调研当地矿业开发现状的基础上,将绿色调查与环境评价两方面工作有机结合,通过3S技术手段对生态环境现状及变化过程进行信息提取,结合2016—2018年连续三年对该区地表水、土壤等多环境介质的野外调查取样与分析结果,分四个层次构建指标框架,建立了一套适用于大型锂资源基地的有针对性的评价指标体系。根据这套创新的调查和评价指标体系,对经过验证的、成熟的评价方法进行优化,运用Python语言研建了基于支持向量机的大型锂资源基地环境评价模型。运用该模型,对甲基卡锂资源基地进行评价,将其环境现状划分为四个级别,实现对大型资源基地环境现状“像元级”的评价,旨在为合理开发锂矿资源提供决策依据。
1. 川西甲基卡锂资源基地绿色调查及环境评价指标建立的依据
川西甲基卡地处青藏高原东部,是少数民族世代游牧的草场分布区,生态环境脆弱,其特殊的外部环境决定了在综合地质调查工作中必须走出一条高效、可行的绿色发展之路。采用科学的方法对每一阶段的开发活动开展环境调查评价、提出环境影响预测,是服务支撑生态环境保护与修复、建设绿色矿山、提高我国矿产资源保障能力的必然要求。从以往的环境评价指标体系研究中可以看出,不同国家、不同地区对于矿产资源环境评价的指标体系是互不相同的,每个指标体系的建立都是研究区自然、经济和特定外部环境特征的反映,指标体系的建立应适应现实工作的需要。尤其是针对川西高原特殊的地理景观区和脆弱的生态环境区环境评价,不能机械地运用前人的方法,要在仔细分析当地的自然环境了解当地矿业开发现状的基础上,结合适合于实地情况的绿色调查手段和高效的计算机运算平台,从而实现对大型资源基地环境的高效、实用的评价,为提出保障甲基卡锂辉石资源基地生态安全的对策,科学决策、合理开发锂矿资源提供基础依据。
2. 川西甲基卡锂资源基地绿色调查与环境评价指标体系的建立方法
当前对于环境评价工作已经有了很多有效的模型实现方法,如层次分析法、专家打分法、改进的二元对比分析法、熵权法、模糊综合评价法、协调程度评价法、多级模糊模式识别模型、等权加和法、加权求和法、PSR模型法、加权综合指数法等。相应的研究成果在矿产资源环境评价的各个阶段都获得了很好的效果,本文综合运用遥感、GIS技术,实现大型资源基地开发决策与空间信息结合,建立了大型资源基地的环境综合评价模型,并采用计算机编程辅助对模型进行实现和验证。
2.1 “绿色调查”与环境评价指标确定的原则
大型资源基地绿色调查与环境评价的指标体系应全面反映大型基地生态系统的自然特征(勘查初期)、矿山建设及矿产资源开发前后生态环境的变化特征、客观评价并预测资源开发的环境影响,并有针对性地提出矿山环境恢复治理措施,应是一个动态的、可持续监测的、科学的指标体系。在环境评价的同时,发挥环境地球化学调查的优势,将绿色调查与环境评价两方面工作有机结合。对指标的选择既要涵盖矿区环境评价普遍适用的指标,又要包含大型资源基地特定矿种在资源开发利用、生态环境保护方面的影响因子。指标体系的构建应分层次、分阶段、可量化、不冗余,并涵盖动态监测的结果。评价模型的建立及计算方法的选择应准确、实用、可推广,并能有效地结合空间信息,便于矿产资源开发利用管理及决策。
2.2 “绿色调查”与环境评价的主要内容
大型资源基地“绿色调查”有两个基本环节。一是将绿色调查与环境评价两方面工作有机结合,分层次构建指标框架,应用3S技术对生态环境现状及变化过程(如地形坡度、地质灾害隐患、植被覆盖度等)进行信息提取,辅以野外调查,根据实际情况优化调查取样手段,通过技术创新,实现调查过程的低扰动、无污染和零排放。通过对调查区的土壤、地表水、植被等连续的采样检测,高精度分析(ICP-MS等)其中有益有害元素的组成与含量,测定其理化特征参数(pH、Eh等),为评价指标体系的建立提供了大量宝贵的可选择指标,使得评价体系更加完整、真实。
对于水环境评价中涉及的元素及主要阴阳离子的含量数据由如下测试方法获得。主要阴离子测定仪器:离子色谱仪,型号Dionex DX-600,分离柱(Dionex IonPac AS18 4mm);保护柱(Dionex IonPac AG18 4mm);自动再生微膜抑制器(ASRS ULTRAⅡ 4mm);电导检测器。主要阳离子测定仪器:电感耦合等离子体发射光谱仪(ICP-OES),型号Optima 8300(美国PerkinElmer公司),测试精度 < 5%。微量元素测定仪器:电感耦合等离子体质谱仪(ICP-MS);按照仪器操作说明规定条件启动仪器,进行仪器参数最佳化试验,并进行校准,校准数据采集至少三次,取平均值。每批试料测定时,同时测定实验室试剂空白溶液。每批试料测定时,同时分析单元素干扰溶液,以获得干扰系数(k)并进行干扰校正。试料测定中间用清洗空白溶液清洗系统。
对于土壤环境评价中涉及的元素含量数据由如下测试方法获得。采集的土壤样品置于电热恒温鼓风干燥箱中于65℃烘干至恒重,过200目筛,得到土壤粉末。于封闭溶样的聚四氟乙烯内罐中,称取粉末样品0.0500g(误差范围±0.0010g),随后加2mL氢氟酸、1mL硝酸,盖上盖,装入钢套中封闭,于190℃加热保温30h。待冷却后打开盖子,取出聚四氟乙烯内罐,置于电热板上,170℃蒸发至干。加0.5mL硝酸再次蒸发至干,这一步骤重复两次,加50%硝酸5mL,盖上盖,将聚四氟乙烯内罐装钢套中封闭。熔样器放入烘箱中,150℃下保温3h,熔样器冷却之后,将其内溶液转至50mL容量瓶中,用超纯水定容至刻度,以备ICP-MS测定。
除土壤粉末样品制备外,以上测试均在国家地质实验测试中心完成。
二是研究建立相应计算方法与评价模型,环境效应的影响因素多样,包括大量定性、定量数据,最终要实现每一个评价指标的量化分级,宏观掌握每一阶段的开发活动的环境影响程度,辅助规范大型基地矿产资源开发利用的管理及决策。本文确立的大型锂矿资源基地绿色调查与环境评价技术准则、实现途径与最终目标如图 1所示。
2.3 绿色调查与环境评价指标体系的构成及模型方法的选择
大型资源基地矿产资源的开发时间跨度长、社会经济影响大,特别是当大型资源基地位于特殊地貌区或生态脆弱区时,其生态影响深远。川西高原生态的脆弱性主要受到自然环境和人类活动两方面作用的影响。研究区平均海拔超过3700米,由于海拔效应使得温度明显低于同纬度的其他地区,被称为“世界第三极”。同时该区域深处大陆内部远离海岸线,空气寒冷干燥降水量低,土壤发育历史短,肥力较弱,植物结构单一。低温缺水加之土壤肥力较差使得植物生产力低下,更新速度缓慢,破坏后恢复速度慢[47]。这一系列自然因素决定了川西高原生态承载力较弱的事实,使其对于外界扰动较为敏感,容易出现退化现象,且退化破坏后较难恢复。人为活动极大地扰动了生态系统稳定的状态,由于生态脆弱区的生态承载力的水平低下,人为活动如果没有得到有效的规范和控制,很容易超出环境生态的承载力,对环境造成破坏。尤其是矿业资源开发中的采矿、选矿、冶炼很容易给环境带来破坏,须在开发规划之初就有所重视。
实现矿产资源的合理开发,既需要协调好生态环境保护与资源开发利用的关系,又要科学预判采矿对环境可能造成的影响,还要制定合理的环境保护与减缓不良环境影响的措施,三者缺一不可。因此,在大型基地矿产资源开发的不同阶段,其环境评价的指标应各有所侧重,模型及计算方法的选择也各有不同。结合生态脆弱区的特点,从资源开发不同阶段出发,本文形成了一套大型基地矿产资源开发不同阶段环境评价指标体系(表 1)。该表中,自然地理和地质背景是对自然环境生态的评价,从地形地貌、植被、降雨量、岩性组合等几个角度较全面地总结和评价了自然环境原有承载能力的水平,因此这几项评价指标贯穿了整个资源基地开发的各个阶段。矿业开发与其带来的对于土壤和水的影响属于人为活动给环境带来扰动的范畴,该指标体系中对其详细地划分为20项分指标,能够较为客观地涵盖了人为矿业生产中的这种活动以及对于环境各方面的影响。
表 1 大型基地矿产资源开发不同阶段环境评价指标体系Table 1. Environmental assessment index system for different stages of mineral resources development in large bases目标层 指标层 勘查初期阶段 矿产资源开发阶段 环境恢复治理阶段 自然地理 地形地貌 √ √ √ 降雨量 √ √ √ 植被覆盖度 √ √ √ 地质背景 地质构造 √ √ √ 岩性组合 √ √ √ 矿业开发 主要开采方式 √ √ √ 噪声 √ √ √ 占用土地比例 √ √ √ 开采点密度 √ √ 采空区面积比 √ √ 开采回采率 √ √ 选矿回收率 √ √ 共伴生组分利用率 √ √ 尾矿利用率 √ √ 环境影响 地质灾害隐患 √ √ √ 地质灾害预警 √ √ √ 水资源破坏程度 √ √ √ 土壤资源破坏程度 √ √ √ 固废堆放占地 √ √ 废水废液排放 √ √ 大气环境质量 √ √ 荒漠化面积 √ √ 土壤侵蚀模数 √ √ 环境治理投入强度 √ 治理难度 √ 3. 川西甲基卡锂资源基地综合环境评价结果与分析
本文在青藏高原川西地区选择甲基卡大型资源基地及周边150平方公里范围为研究区域进行典型研究。川西锂辉石开发环境效应的影响因素多样,包括大量定性、定量数据。川西甲基卡大型锂矿基地正处于勘查初期阶段,本次研究参考《区域环境地质调查总则》基本要求,针对川西甲基卡锂辉石矿区环境特点与勘查开发阶段,对李东等(2015)[48]的矿山环境评价模型进行优化改进,结合2.3节构建的大型基地矿产资源开发不同阶段环境评价指标体系,建立了一套包括自然地理、基础地质、矿业开发以及地质环境在内4大类、12小类的评价指标体系。指标体系的构建共分2个层次:第一层次为4个矿山环境因子的大类指标划分,即自然地理(A)、基础地质(B)、矿山开发占地(C)和矿业活动有关的环境影响(D);第2个层次为各个大类指标的细化指标,包括12个分项指标(指标层,表 2)。
表 2 环境效应评价指标量化处理标准Table 2. Quantitative processing standard of the environmental effect evaluation index指标类型 评价指标 评价指标分级标准(分值) 1 2 3 自然地理(A) 地形地貌(A1)
降水量(A2)
植被覆盖度(A3)坡度>35°
<200mm
<40%坡度20°~35°
200~900mm
40%~60%坡度<20°
>900mm
>60%基础地质(B) 构造(B1)
岩性组合(B2)强烈发育
松散堆积物较发育
软质岩为主不发育
硬质岩为主矿业开发(C) 主要采选方式(C1)
噪声(C2)
占用土地比例(C3)浮选
嘈杂
>10%重选+磁选
一般
0~10%联合选矿
安静
无矿业占地环境影响(D) 地质灾害隐患(D1)
地质灾害预警(D2)
水环境破坏程度(D3)
土壤环境破坏程度(D4)易发
较多
严重
严重轻微
一般
一般
一般基本没有
较少
无
无评价过程中,依据建立的评价指标体系,通过典型区资料的收集处理包括Landsat遥感影像、研究区基础地质图、研究区数字高程模型(分辨率30米)、研究区行政区划图、研究区水样评价数据(野外调查实测)、研究区土壤评价数据(野外调查实测)、研究区自然、社会经济方面的文字资料等,利用ENVI、ArcGIS等空间数据处理软件,对遥感影像进行投影转换、几何校正、归一化植被指数计算;利用ArcGIS工具软件对研究区的DEM数据进行坡度计算,得到坡度图;利用ArcGIS、ENVI工具软件,通过人机交互解译、空间分析等方法,计算得到矿山开发占地等评价指标图层。
通过几何重采样、分值量化处理等方法,将研究区采样设置为27118个100m×100m的单元,每个单元均具有12个量化指标,评价指标值均量化为1、2、3三个分值。对经过验证的、成熟的评价方法[49]进行优化,构建基于支持向量机的环境评价模型,将研究区划分为环境较差区、环境一般区、环境较好区、环境良好区四类区域(图 2)。评价结果中,环境较差区主要集中在矿区、矿区周边及尾矿库周边,环境较好区主要分布在远离矿区的、坡度较小、植被覆盖较高的区域。通过对已有先期经验的验证单元进行分类,判断分类评价模型的客观性和准确性。628个验证样本中,13个为环境较差区样本,48个为环境一般区样本,106个为环境较好区样本,461个为环境良好区样本。验证结果表明,除环境良好区单元中有19个环境良好区单元被误评价为环境较好区单元外,其余单元均被正确分类,总体准确率达到97.77%;尤其是针对环境较差区的判别,准确率达100%。由此可见该分类模型具有较高的准确性和客观性。基于支持向量机的定量评价模型应用与锂辉石矿区环境评价,将环境评价得分划分为4个级别,为当地资源开发与环境保护协调发展提供了一定证据与参考。
4. 结论
针对当前能源金属锂绿色矿山建设行业标准与环境评价指标体系研究成果较少的现实问题,本文提出了适用于高原地区大型资源基地“绿色调查”的方法,即在资源基地环境扰动最小的前提下,实现了找矿部署最优化和生态环境保护最大化,通过创新方法[50],以地质背景与生态环境作为整体系统进行调查研究,通过跨学科综合调查成果来优化找矿部署。拓展并提出了相应的环境评价指标体系,各指标的评价结果以可量化的数据表达,并能有效地结合空间信息,便于矿产资源开发利用各阶段的管理及决策。对经过验证的、成熟的评价方法进行优化,运用Python语言编程建立了基于支持向量机的大型锂资源基地环境评价模型。
将提出的环境评价指标体系及评价模型应用于甲基卡矿区,对研究区的环境现状作出了合理的分级,解决了以往以行政单元(市区县界)为单元的评价在矿区或大型基地尺度的应用壁垒,从技术上实现了大型资源基地环境现状的“像元级”的评价分级。研究结果表明本指标体和模型能够比较客观地反映甲基卡矿区及周边地质环境背景、资源开发环境问题与影响范围,回答了“能不能开发”以及“开发哪里”这两个实际问题,为当地资源开发与环境保护协调发展提供了一定证据与参考。研究成果有助于突破高原生态脆弱区找矿部署与环境保护瓶颈问题,具有较强的现实意义。
致谢: 感谢同济大学海洋与地球科学学院马松阳硕士对本文撰写提供的指导和建议,同时感谢两位匿名审稿人提出的宝贵意见。 -
表 1 Sr、Nd、U同位素联合过柱分离流程
Table 1 Procedure of combined Sr, Nd, U isotopes separation
流程 分离步骤 树脂柱 淋洗试剂 试剂总体积
(mL)馏分
编号①
预清洗本底清洗 Sr特效树脂 3mol/L硝酸 6 - 超纯水 6 - 3mol/L硝酸 5 - 超纯水 5 - 3mol/L硝酸 5 - 超纯水 5 - AG50W-X8
树脂6mol/L盐酸 15 - 超纯水 5 - UTEVA特效
树脂3mol/L硝酸 4 - 3mol/L盐酸 4 - 3mol/L盐酸 4 - 超纯水 4 - ②
三柱串联平衡树脂 - 3mol/L硝酸 3 - 上样 3mol/L硝酸 2 1 洗杂质 3mol/L硝酸 6 ③
三柱分离洗杂质 Sr特效
树脂3mol/L硝酸 9 2 收集Sr 超纯水 4 3 回收树脂 6mol/L盐酸+超纯水 11 4 洗杂质 AG50W-X8
树脂2.5mol/L盐酸 4 5 收集REE 6mol/L盐酸 10 6 回收树脂 6mol/L盐酸 5 7 洗杂质 UTEVA特效
树脂3mol/L盐酸 6 8 收集U 1mol/L盐酸 4 9 回收树脂 超纯水+3mol/L硝酸 +3mol/L盐酸 +1mol/L盐酸 20 10 -
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