磁响应生物破乳菌的设计制备及其强化破乳机制

The demulsification of the oil-water emulsion has both benefits of oil recovery and water purification. Demulsifying bacteria gain a great popularity for their high-efficiency and environmental friendliness. However, their extensive application were limited by a low demulsification rate and a residue of cells in the system. In this study, a new magnetically responsive bacterial demulsifier(MRBD) is designed and synthesized through the combination of magnetic nanoparticles and demulsifying bacteria to accelerate the demulsifying rate and recover the MRBD. The Turbiscan technology and self-built micropipette technique testing platform are employed to study the effect of MRBD on the aggregation, coalescence and sedimentation of droplets in demulsification processes, discovering the key stage in enhancing the demulsification performance. The three dimensional transmutation of MRBD in emulsion during the demulsification process is analyzed by laser scanning confocal microscope and frozen scanning microscope. The magnetic tweezer manipulation apparatus is constructed to explore the mechanical characteristics of MRBD during its migration in oil and water phase, and obtain the energy changes of MRBD during its adsorption and desorption process from the oil-water interface. Finally, the key factor and mechanism of enhancing the demulsification efficiency are illustrated through analyzing the effects of MRBD action on demulsification performance and process. The outcome of the research will offer theoretical and technical technology for directional synthesis and application of highly efficient demulsifying bacteria.

油水乳状液的破乳具有资源回收和污染控制的双重效益。前期研究表明生物破乳菌有破乳率高、环境友好等优势；但也存在破乳速率偏低、破乳后菌体残留的问题。本项目将磁性纳米粒子与破乳菌结合设计制备了不同磁响应破乳菌(Magnetically Responsive Bacterial Demulsifier, MRBD)以强化破乳效能并实现破乳菌回用。通过稳定性分析仪和微吸液管测试平台分析MRBD对破乳宏观过程和微观液滴演变的影响规律，明晰其强化破乳的关键阶段。采用激光共聚焦显微镜和冷冻扫描电镜考察MRBD在乳状液中的3D分布演变；基于磁操纵技术平台探究MRBD在油相、水相中迁移的力学特征，重点分析测定MRBD在油水界面吸附解吸过程的能变；分析MRBD的行为特征对破乳效能和破乳过程的影响规律，揭示MRBD强化破乳的关键因素和机制。研究成果将为定向合成高效破乳菌提供理论和技术支撑。

废弃乳化液具有成分复杂、污染物浓度高、稳定性极强的显著特点，属于国家危险废物名录（HW09），废弃乳化液的破乳（油水分离）是废水处理和油资源回收的关键。生物破乳菌有破乳率高、环境友好等优势；但也存在破乳速率偏低、破乳后菌体残留的问题。本项目将磁性纳米粒子和破乳菌结合，设计制备了磁响应破乳菌，以及直接用于破乳的新型功能化磁性纳米颗粒；探究了磁性颗粒破乳剂对乳化液的破乳过程的作用机制；并进一步开发了磁絮凝破乳分离技术与工程应用。研究首次成功合成了具有磁响应的破乳菌系列，且可实现其表面亲疏水、带电性、磁响应性可调，磁响应破乳菌相比于破乳菌其对乳化液破乳速率提高33%，破乳后脱水质量提高6倍，可实现至少3次回收再利用。并进一步设计合成了直接用于乳化液破乳的功能化磁性纳米颗粒(M@NH2)，对复杂的机械加工废弃乳化液可实现85%~97%的破乳率。对颗粒破乳剂破乳过程与机制的研究表明，磁性颗粒破乳可分为三个阶段：磁性颗粒粘附到液滴表面，液滴发生聚并，在外磁场作用下磁性颗粒拖拽液滴实现定向迁移聚集，并最终完成破乳。其中基于静电作用力磁性纳米颗粒吸附乳化液中保护油滴稳定的乳化剂分子，破坏其结构的稳定性；同时基于磁性颗粒的表面亲疏水性和尺寸效应粘附到油滴表面，破乳界面结构，促进液滴之间的聚并；外磁场作用力驱动下，磁性颗粒破乳剂拖动油滴定向迁移，实现乳化液中液滴聚集聚并，并最终实现加速破乳油水分离。在技术开发与工程应用方面的研究表明，将絮凝剂与磁性颗粒进行耦合开发出了的磁絮凝破乳技术可实现对实际机械加工废弃乳化液的破乳分离。与传统絮凝相比，磁絮凝所需的絮体分离时间缩短了80%~95%，絮体体积减少了50%~80%。该项目研究成果为机械加工废弃乳化液高效、低成本处理提供了的新的技术途径与工程示范，为乳化液破乳过程中磁场作用机制的研究奠定了基础。