青藏高原盐湖提锂的环境影响与管控对策

Environmental impacts and management strategies of lithium extraction from salt lakes in the Qinghai-Xizang Plateau

  • 摘要: 盐湖锂资源是全球锂供给的关键来源,其绿色开发对实现能源转型具有重要意义;盐湖兼具高原盐湖矿和天然湖泊的双重属性,其生态环境保护问题不容忽视。近年来,我国青藏高原多个盐湖的锂资源开发进入快速发展阶段,盐湖提锂技术正由传统盐田蒸发模式向吸附法、膜分离法及电化学法等直接提锂技术(DLE)转型,但复杂工艺运行引发的水文化学平衡及污染物排放回湖等问题引起高度关注。基于典型提锂工艺流程分析,将直接提锂过程划分为预处理、分离提取、深度除杂、沉锂等关键环节,并对已开展的相关研究进行综述,系统梳理直接提锂技术各工艺带来的环境影响,并从宏观层面对盐湖开发的区域环境影响进行分析。研究表明,盐田蒸发法是导致盐湖萎缩的重要驱动因素;直接提锂的部分工艺废水与尾卤如果处置不当回湖易引发局部酸碱变化,并伴随重金属等污染风险,进而威胁盐湖水生态系统安全。为实现盐湖锂资源的绿色可持续开发,建议推动盐田沉淀法向“预浓缩+DLE”模式升级,推广电化学脱嵌、双极膜电渗析与机械蒸汽再压缩(MVR)蒸发结晶等低环境负荷工艺,同时需构建全流程产排污清单强化污染特征定量识别,结合关键物种毒性效应制定回湖污染物负面清单,优化尾卤回湖管理策略。

     

    Abstract: Salt lake lithium (Li) resources are a key source of global Li supply, and their green development is of great significance for achieving the goal of energy transition. Salt lakes possess dual attributes: they function both as plateau salt lake mines and as natural lakes, and their ecological and environmental concerns cannot be overlooked. In recent years, Li extraction activities in several salt lakes across the Qinghai-Xizang Plateau of China have entered a stage of rapid development. Meanwhile, Li extraction technologies are transitioning from conventional solar evaporation methods to direct lithium extraction (DLE) technologies, including adsorption, membrane separation, and electrochemical processes. However, the operation of these complex processes has raised growing concerns, primarily regarding the hydrochemical balance and the discharge of pollutants back into the lake. Based on typical Li extraction process flows, the DLE process can be divided into four key stages: pretreatment, separation and extraction, deep purification, and lithium precipitation. Existing studies are systematically reviewed to synthesize the environmental impacts associated with each process stage of DLE, while the regional environmental effects of salt lake development are further analyzed from a macro perspective. The results indicate that solar evaporation is a major driver of salt lake shrinkage. In contrast, improper management of process wastewater and residual brine in DLE operations may lead to localized pH fluctuations and introduce risks of heavy metal contamination when discharged back into the lake, thereby threatening the safety of salt lake aquatic ecosystems. To realize the green and sustainable exploitation of salt lake Li resources, the conventional solar pond precipitation process should be upgraded toward an integrated "pre-concentration+DLE" model. Low-environmental-impact technologies, including electrochemical intercalation and deintercalation, bipolar membrane electrodialysis, and mechanical vapor recompression (MVR) evaporation crystallization, should be promoted. In addition, a full-process pollutant generation and discharge inventory should be established to strengthen quantitative identification of pollution characteristics. A negative list of pollutants discharged back to salt lakes should be formulated based on toxic effects of key species, and management strategies for residual brine returning to lakes should be optimized.

     

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