Liu Ying, Qin Mohan, Luo Shuai, He Zhen, Qiao Rui
Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Sci Rep. 2016 Mar 3;6:22547. doi: 10.1038/srep22547.
We report an integrated experimental and simulation study of ammonia recovery using microbial electrolysis cells (MECs). The transport of various species during the batch-mode operation of an MEC was examined experimentally and the results were used to validate the mathematical model for such an operation. It was found that, while the generated electrical current through the system tends to acidify (or basify) the anolyte (or catholyte), their effects are buffered by a cascade of chemical groups such as the NH3/NH4(+) group, leading to relatively stable pH values in both anolyte and catholyte. The transport of NH4(+) ions accounts for ~90% of the total current, thus quantitatively confirming that the NH4(+) ions serve as effective proton shuttles during MEC operations. Analysis further indicated that, because of the Donnan equilibrium at cation exchange membrane-anolyte/catholyte interfaces, the Na(+) ion in the anolyte actually facilitates the transport of NH4(+) ions during the early stage of a batch cycle and they compete with the NH4(+) ions weakly at later time. These insights, along with a new and simple method for predicting the strength of ammonia diffusion from the catholyte toward the anolyte, will help effective design and operation of bioeletrochemical system-based ammonia recovery systems.
我们报告了一项关于使用微生物电解池（MEC）回收氨的综合实验和模拟研究。对MEC间歇模式运行过程中各种物质的传输进行了实验研究，并将结果用于验证该运行模式的数学模型。研究发现，虽然通过系统产生的电流倾向于使阳极电解液（或阴极电解液）酸化（或碱化），但其影响会被NH₃/NH₄⁺等一系列化学基团缓冲，从而使阳极电解液和阴极电解液中的pH值相对稳定。NH₄⁺离子的传输占总电流的约90%，从而定量证实了NH₄⁺离子在MEC运行过程中作为有效的质子穿梭体。进一步分析表明，由于阳离子交换膜 - 阳极电解液/阴极电解液界面处的唐南平衡，阳极电解液中的Na⁺离子实际上在间歇循环的早期促进了NH₄⁺离子的传输，并且在后期它们与NH₄⁺离子的竞争较弱。这些见解，以及一种预测氨从阴极电解液向阳极电解液扩散强度的新的简单方法，将有助于基于生物电化学系统的氨回收系统的有效设计和运行。
