Jin Wang,Fudi Wang,Bing Yang,Jiang Wu,Mengtao Tian,Jiani Zhu,Xudong Wang,Lei Wang
A lamellar membrane assembled by parallel restacking of two-dimensional nanosheets provides a novel platform for studying the electrostatic manipulation of ion mobility under angström-scale confinement. The membrane nanostructure in aqueous solution is unstable due to intercalation. However, because accurate measurements of structural changes under different charged conditions are difficult, their effect on the ion modulation was seldom fully addressed, and the electrostatic modulation mechanism was not good. Here, we report the efficient manipulation of ion diffusion in the confined channels through a Ti3C2Tx membrane and gain insight into the mechanism by an in situ measurement of the lamellar nanostructure using an electrochemical quartz crystal microbalance with dissipation (EQCM-D). By precisely tuning the external potential directly applied to the membrane, the ion permeation rate can be effectively and reversibly increased by 6 times or decreased by 15 times. The EQCM-D measurement provides empirical evidence to demonstrate that the anomalous ion-flow modulation is determined by both the channel diameter and an ion rearrangement in the electrical double layers (EDLs), particularly, in the Stern layers. Although the channel expanded at low negative voltage, the ion permeation rate decelerated due to the counterion distribution in the Stern layers.
Jiani Zhu,Lei Wang,Jin Wang,Fudi Wang,Mengtao Tian,Shuchang Zheng,Ning Shao,Lele Wang,Miaolu He
Two-dimensional (2D) membranes exhibit exceptional properties in molecular separation and transport, which reveals their potential use in various applications. However, ion sieving with 2D membranes is severely restrained due to intercalation-induced swelling. Here, we describe how to efficiently stabilize the lamellar architecture using Keggin Al13 polycations as pillars in a Ti3C2Tx membrane. More importantly, interlayer spacing can be easily adjusted with angstrom precision over a wide range (2.7–11.2 Å) to achieve selective and tunable ion sieving. A membrane with narrow d-spacing demonstrated enhanced selectivity for monovalent ions. When applied in a forward osmosis desalination process, this membrane exhibited high NaCl exclusion (99%) with a fast water flux (0.30 L m–2 h–1 bar–1). A membrane with wide d-spacing showed notable selectivity, which was dependent on the cation valence. When it was applied to acid recovery from iron-based industrial wastewater, the membrane showed good H+/Fe2+ selectivity, which makes it a promising substitute for traditional polymeric membranes. Thus, we introduce a possible route to construct 2D membranes with appropriate structures to satisfy different ion-sieving requirements in diverse environment-, resource-, and energy-related applications.
Peng Zhang,Yiran Wang,Xiaomin Luo,Jian Wang,Wenqi Wang,Xubin Duan,Kai Qi,Meng Li
The heterogeneous electro-Fenton (HEF) membrane has shown great potential for the treatment of refractory organic pollutants, but there are growing demands to improve its degradation efficiency and suitability for addressing practical organic pollutant issues. Here, a novel Co-CNT/Ti3C2TX nanocomposite membrane was successfully prepared by vacuum filtration, followed by heat treatment. Different from the traditional batch reactor, a flow-through reactor with Co-CNT/Ti3C2TX membrane was designed as an electrode to make the full use of the combined synergistic effect of adsorption and electro-Fenton (EF) process for the degradation of organic pollutants. The results found that the Co-CNT/Ti3C2TX flow-through HEF system exhibited satisfactory degradation (99.0–83.2%) on tetracycline (TC) in a wide range of pH 2.0–7.0. In addition, the obtained Co-CNT/Ti3C2TX membrane possesses self-cleaning performance in long-term continuous conditions. Co-CNT/Ti3C2TX membrane can also be used to treat practical TC wastewater with complex components, tannery printing and dyeing wastewater, and wastewater with different water matrices, and their removal efficiency can reach more than 87.0%. Specially, the coupling effect could be beneficial to accelerate the degradation of pollutants in the EF process. The method provided in this work could be further expanded, making industrial usage of the HEF membrane a reality.
危险品化学品经营许可证（带存储）