生物淋滤-生物还原两步反应从废旧锌锰电池制备纳米ZnS和MnS

Disposal of spent batteries represents a growing environmental problem due to the metallic content, being considered as hazardous waste. The Zn-Mn batteries occupy over 90% of the total annual sales of portable batteries due to their low prices, especially in the developing countries like China. They are run out rapidly and thrown away, so the spent Zn-Mn batteries pose the worst potential environmental threat and the most serious resource loss of both Zn and Mn as the largest category of spent batteries. In this proposal, a novel idea, preparation of valuable nano ZnS and MnS from the Zn-Mn batteries using a two-step reaction of bioleaching and bioreduction which is high efficiency, low cost, few industrial requirements and eco-friendly, was raised not only from the viewpoint of treatment of hazardous waste but also with respect to recovery of valuable metals. On the one hand, release of both Zn and Mn from the spent Zn-Mn batteries is achieved using bioleaching in a low-cost and eco-friendly way; on the other hand, high-purity and wide-application nano ZnS and MnS is prepared through bioreduction under a mild condition, fully implementing resource-recovery treatment of the spent Zn-Mn batteries. The main research contents cover ⅰ) to expound the chemical and microbiological mechanisms involved in the bioleaching of the spent Zn-Mn batteries for release of both Zn and Mn, especially the ones of interface and electrochemistry; ⅱ) to offer the optimum conditions and key technique for efficient dissolution of both Zn and Mn from the spent Zn-Mn batteries by bioleaching under 10% of pulp density; ⅲ) to reveal the microcosmic process and micro-mechanism involved in fractional precipitation of Zn and Mn from the leachate by bioreduction; ⅳ) to determine the technological conditions and adjustment measures for preparation of nano ZnS and MnS using the leachate containing both Zn and Mn ions as precursor based on bioreduction principle.

废旧电池的产生及污染已成为国内外关注的重大环境问题之一。锌锰电池长期以来处于国家电池生产和消费的主体地位，构成我国废旧电池污染的重要来源并造成锌锰资源的巨大浪费。本项目将经济高效、环境友好、二次污染小、操作条件温和的微生物技术引入废旧锌锰电池的资源化处理，提出生物淋滤-生物还原两步反应从废旧锌锰电池制备高纯纳米ZnS和MnS的学术思想。阐明废旧电池锌锰离子生物淋溶的化学和微生物学机制，确立高固液比条件下废旧电池锌锰离子高效溶释的优化条件和关键技术；揭示电池淋滤液锌锰离子生物还原分步沉淀的微观过程和微观机理，确定电池淋滤液生物还原制备高纯纳米ZnS和MnS的工艺条件及调控措施，建立生物淋滤-生物还原两步反应从废旧锌锰电池制备纳米ZnS和MnS的总体流程和关键参数。项目研究对于我国废旧锌锰电池的处理和锌锰资源的回收利用具有重要意义，对于我国电池工业的节能减排、循环经济和可持续发展产生重要影响。

提出生物淋滤-生物还原两步反应从废旧锌锰电池制备高纯纳米ZnS和MnS的资源化处理路线。三维荧光光谱分析表明电池投加量影响着EPS的组成和浓度，而锌锰溶释效率与EPS之间存在正相关关系。外加EPS促进了菌株生长， 提升了H+,Fe3+,Fe2+生成，提高了非接触沥浸效能；增强了菌株和电池的吸附作用，提高了接触沥浸效能。应用曲面响应法研究了底物浓度、pH控制、温度和固液比对锌锰溶释效率的影响模式以及其交互关系，建立了锌锰溶出效能的数学模型，实现了10%固液比下锌52.5%和锰52.4%的最大溶出。0.8 g/L的Cu2+显示了最高的生物沥浸催化活性，锰和锌的溶出效率分别由30.9%和47.7%升至62.5%和62.7%；其催化机制在于Cu2+和电极材料ZnMn2O4反应生成中间产物CuMn2O4，而后者易于Fe3+氧化攻击溶释Mn2+并再生Cu2+。廉价安全的Fe3+外加也可大幅提高锌锰溶释效率，5.0%固液比下5.0 g/L加入量锰和锌的溶出效率分别由29.4%和34.5%升至83%和85%。Fe3+外加促进了Fe2+和S0生成，刺激了L.f 和 A.t生长，改善了锌锰浸提；7.5g/L的过量加入则导致大量黄钾铁矾生成，其对电池的包裹阻止了锌锰溶释；相应地，5.0g/L加入腐蚀电流达到最大0.571mA/cm2。在锌锰共存条件下，控制Zn2+为10mmol/L、Mn2+为6-8mmol/L、EDTA为10mmol/L、SO42-为10mmol/L、PO43-为2mmol/L、pH为5-6时, 先生成ZnS纳米球沉淀，粒径20-30纳米，后生成MnS纳米片，厚度5-10纳米，分步沉淀制备了高纯纳米ZnS和MnS。在单一Mn2+存在下，精确控制PO43-为0.014g/L和pH为5.8生物制备直径为2-3μm、厚度为200-300nm、质地均匀的六边形γ-MnS颗粒；利用Mn2+-EBT螯合物的空间位阻实现了Mn2+和S2-的选择性沉淀，在高PO43-浓度、 高碱度条件下生物制备了八面椎体γ-MnS颗粒。在单一Zn2+存在下, 外加HPS介导生物制备了晶形和大小可控的ZnS量子点：低HPS为8±2 nm的α –ZnS，高HPS为4±1 nm的β –ZnS；多菌株复配实现了5.49nm的ZnS量子点直接胞外生物合成，胞外蛋白在胞外蛋白胞外蛋白在量子点合成中起了成核和模板的