Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Ghent 9000, Belgium.
Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, United States.
Water Res. 2021 Jan 1;188:116532. doi: 10.1016/j.watres.2020.116532. Epub 2020 Oct 17.
Ammonium is typically removed from wastewater by converting it to nitrogen gas using microorganisms, precluding its recovery. Copper hexacyanoferrate (CuHCF) is known to reversibly intercalate alkali cations in aqueous electrolytes due to the Prussian Blue crystal structure. We used this property to create a carbon-based intercalation electrode within an electrochemical cell. Depending on the electrode potential, it can recover NH from wastewater via insertion/regeneration while leaving organics. In the first phase, different binders were evaluated towards creating a stable electrode matrix, with sodium carboxymethyl cellulose giving the best performance. Subsequently, based on voltammetry, we determined an intercalation potential for NH removal of + 0.3 V vs. Ag/AgCl, while the regeneration potential of the electrode was + 1.1 V (vs. Ag/AgCl). Using the CuHCF electrodes 95% of the NH in a synthetic wastewater containing 56 mM NH and 68 mM methanol was removed with an energy input of 0.34 ± 0.01 Wh g NH. A similar removal of 93% was obtained using an actual industrial wastewater (56 mM NH, 68 mM methanol, 0.02 mM NO, 0.05 mM NO, 0.04 mM SO and 0.34 mM ethanol), with an energy input of 0.40 ± 0.01 Wh g NH. In both cases, there was negligible removal of organics. The stability of CuHCF electrodes was evaluated either by open circuit potential monitoring (61 h) or by cyclic voltammetry (50 h, 116 cycles). The stability during cycling of the electrode was determined in both synthetic and real streams for 25 h (125 cycles). The charge density (C cm) of the CuHCF electrodes declined by 17 % and 19% after 125 cycles in the synthetic stream and the actual wastewater, respectively. This study highlights the possibility of low-cost CuHCF coated electrodes for achieving separation of NH from streams containing methanol. The stability of electrodes has been improved but needs to be further enhanced for large-scale applications and long-term operation.
氨通常通过利用微生物将其转化为氮气来从废水中去除，从而阻止其回收。已知铜六氰合铁酸盐（CuHCF）由于普鲁士蓝晶体结构而能够在水性电解质中可逆地嵌入碱金属阳离子。我们利用这一特性在电化学电池内创建了一种基于碳的嵌入电极。根据电极电势，它可以通过插入/再生从废水中回收 NH，同时留下有机物。在第一阶段，评估了不同的粘合剂来创建稳定的电极基质，其中羧甲基纤维素钠的性能最佳。随后，根据伏安法，我们确定了 NH 去除的嵌入电势为+0.3 V 相对于 Ag/AgCl，而电极的再生电势为+1.1 V（相对于 Ag/AgCl）。使用 CuHCF 电极，在含有 56 mM NH 和 68 mM 甲醇的合成废水中，95%的 NH 被去除，能量输入为 0.34 ± 0.01 Wh g NH。使用实际的工业废水（56 mM NH、68 mM 甲醇、0.02 mM NO、0.05 mM NO、0.04 mM SO 和 0.34 mM 乙醇），获得了相似的 93%的去除率，能量输入为 0.40 ± 0.01 Wh g NH。在这两种情况下，有机物的去除量都可以忽略不计。通过开路电势监测（61 h）或循环伏安法（50 h，116 次循环）评估 CuHCF 电极的稳定性。在合成液和实际液中分别对电极的循环稳定性进行了 25 h（125 次循环）的测试。在合成液和实际废水中，CuHCF 电极的电荷密度（C cm）在 125 次循环后分别下降了 17%和 19%。该研究强调了使用低成本 CuHCF 涂层电极从含有甲醇的废水中分离 NH 的可能性。虽然电极的稳定性已经得到提高，但仍需要进一步提高，以实现大规模应用和长期运行。
