Kaniadakis Iosif, van Lier Jules B, Spanjers Henri
Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, Delft 2628 CN, the Netherlands.
Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, Delft 2628 CN, the Netherlands.
Water Res. 2025 Nov 1;286:124185. doi: 10.1016/j.watres.2025.124185. Epub 2025 Jul 8.
Despite growing scientific interest in the past decade, bipolar membrane electrodialysis has seen limited advancement in controlled operation of water dissociation via the bipolar membrane (BPM). For nutrient recovery applications, such as ammonia (NH₃) extraction from anaerobic digestion reject water, implementing in-situ pH control in the base solution could enhance energy efficiency. By controlling the electric current, pH is regulated through OH⁻ generation from the bipolar membrane (BPM). Once the targeted pH is reached, the electric current is applied in pulses and pauses with the purpose to sustain and to not overpass the pH setpoint. A selective electrodialysis reversal (SEDR) combined with a two-compartment bipolar membrane electrodialysis (BPMC) and vacuum membrane stripping (VMS) enabled the recovery and conversion of ammonium ions (NH₄⁺) into volatile ammonia (NH₃). Operating the BPMC with the developed pH control method lowered energy consumption ( [Formula: see text] ) and improved current efficiency for NH₄⁺ removal compared to constant current (CC) operation. Under pH control, the BPMC maintained the target pH throughout the whole operation, with an [Formula: see text] between 12.5 and 35.3 MJ·kgN⁻¹, compared to 12.1 and 78.6 MJ·kgN⁻¹ under CC. The current efficiency was maintained across setpoints with pH control, ranging between 25 % and 29 %. With CC, the current efficiency declined from 27 % to 12 % at higher current densities. Furthermore, pH control applying a pulsed electric current reduced the occurrence of scaling by minimising the transport of divalent cations across the cation exchange membrane and CO formation in the acid compartment. Similar removal efficiencies were attained, applying pH controlled operation and CC; however, both methods performed a declining removal efficiency during 30 h operation. The developed pH control method can provide distinct improvement in scale-up applications, where energy reduction by preventing excessive water dissociation by the BPM is of interest. In addition, external caustic dosing can be substituted by pH control with a BPMC layout of the stack, reducing the residual impurities of the chemical dosing.
尽管在过去十年中科学兴趣不断增加，但双极膜电渗析在通过双极膜（BPM）控制水电离操作方面进展有限。对于营养物回收应用，如从厌氧消化渗滤液中提取氨（NH₃），在碱溶液中实施原位pH控制可以提高能源效率。通过控制电流，通过双极膜（BPM）产生OH⁻来调节pH。一旦达到目标pH，就以脉冲和暂停方式施加电流，以维持并不过超pH设定值。选择性电渗析反转（SEDR）与两室双极膜电渗析（BPMC）和真空膜汽提（VMS）相结合，能够将铵离子（NH₄⁺）回收并转化为挥发性氨（NH₃）。与恒流（CC）操作相比，采用所开发的pH控制方法运行BPMC降低了能耗（[公式：见原文]），并提高了NH₄⁺去除的电流效率。在pH控制下，BPMC在整个操作过程中保持目标pH，能耗在12.5至35.3 MJ·kgN⁻¹之间，而CC操作下为12.1至78.6 MJ·kgN⁻¹。在pH控制下，电流效率在设定点之间保持在25%至29%之间。采用CC时，在较高电流密度下电流效率从27%降至12%。此外，施加脉冲电流的pH控制通过最小化二价阳离子跨阳离子交换膜的传输和酸室中CO的形成，减少了结垢的发生。采用pH控制操作和CC可获得相似的去除效率；然而，在30小时的操作过程中，两种方法的去除效率均呈下降趋势。所开发的pH控制方法在放大应用中可提供显著改进，在放大应用中，通过防止BPM过度水电离来降低能源消耗是令人关注的。此外，通过堆叠的BPMC布局进行pH控制可以替代外部苛性碱投加，减少化学投加的残留杂质。
