Environmental Science and New Energy Technology Research Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen 518055, China.
Shenzhen Engineering Research Laboratory for Sludge and Food Waste Treatment and Resource Recovery, Tsinghua Shenzhen International Graduate School, Shenzhen 518055, China.
Environ Sci Technol. 2020 Oct 6;54(19):12723-12731. doi: 10.1021/acs.est.0c04383. Epub 2020 Sep 18.
Ammonium (NH) in wastewater is both a major pollutant and a valuable resource. Flow-electrode capacitive deionization (FCDI) is a promising technology for chemical-free and environmentally friendly NH removal and recovery from wastewater. However, the coexisting sodium (Na) in wastewater, with a similar hydrated radius to NH, competes for the adsorption sites, resulting in low NH removal efficiency. Here, potassium dititanate (KTiO or KTO) particles prepared by the electrospray method followed by calcination were mixed with activated carbon (AC) powder to form a novel KTO-AC flow-electrode for selective NH removal over Na. The mixed KTO-AC electrode exhibits a much higher specific gravimetric capacitance in NHCl solution than in NaCl solution. Compared with the pure AC electrode in the FCDI tests on NH removal from synthetic wastewater, 25 wt % KTO addition in the electrode mixture increases the adsorption selectivity from 2.3 to 31 toward NH over Na, improves the NH removal from 28.5% to 64.8% and increases the NH desorption efficiency from 35.6% to over 80%, achieving selective NH recovery and effective electrode regeneration. Based on DFT calculations, NH adsorption on the KTiO (0 0 1) surface is more thermodynamically favorable than that of Na, which contributes to the high NH adsorption selectivity observed.
废水中的铵（NH）既是主要污染物又是有价值的资源。流动电极电容去离子（FCDI）是一种有前途的技术，可用于从废水中无化学物质且环保地去除和回收 NH。然而，废水中与 NH 具有相似水合半径的钠离子（Na）会竞争吸附位点，导致 NH 的去除效率较低。在这里，通过电喷雾法制备的钛酸钾（KTiO 或 KTO）颗粒，然后经过煅烧，与活性炭（AC）粉末混合形成一种新型的 KTO-AC 流动电极，用于选择性去除废水中的 NH 而不是 Na。混合的 KTO-AC 电极在 NHCl 溶液中的比重量比电容比在 NaCl 溶液中高得多。与 FCDI 测试中从合成废水中去除 NH 时使用的纯 AC 电极相比，电极混合物中添加 25wt%的 KTO 将 NH 对 Na 的吸附选择性从 2.3 提高到 31，将 NH 的去除率从 28.5%提高到 64.8%，并将 NH 的解吸效率从 35.6%提高到 80%以上，实现了选择性 NH 回收和有效的电极再生。基于 DFT 计算，NH 在 KTiO（001）表面的吸附在热力学上比 Na 更有利，这有助于观察到高 NH 吸附选择性。
