Efficient sequestration of cesium ions using phosphoric acid-modified activated carbon fibers from aqueous solutions.

In this study, acid-modified activated carbon fibers (ACF-Ps) were synthesized by phosphorylation. Three different types of ACF-based adsorbents functionalized with PO43-, P2O74-, or P3O105- ions, namely, ACF-P1, ACF-P2, and ACF-P3, were prepared by phosphorylating ACF with trisodium phosphate (Na3PO4), sodium dihydrogen pyrophosphate (Na2H2P2O5), and sodium tripolyphosphate (Na5P3O10), respectively, and utilized as adsorbents to remove cesium ions (Cs+) from aqueous solutions. Among the tested adsorbents, ACF-P3 exhibited the highest Cs+ adsorption capacity of 37.59 mg g-1 at 25 °C and pH 7 which is higher than that of ACF (5.634 mg g-1), ACF-P1 (19.38 mg g-1), and ACF-P2 (30.12 mg g-1) under the same experimental conditions. More importantly, the Cs+ removal efficiencies of ACF-P3 (82.90%), ACF-P2 (66.2%), ACF-P1 (34.2%) were 29.3-, 23.4-, and 12.11-fold higher than that of un-treated ACF (2.83%). The results suggested that the phosphorylation with Na5P3O10 is highly suitable for Cs+ adsorption which effectively functionalizes ACF with a greater number of phosphate functional groups. Adsorption and kinetic data well-fitted the Langmuir isotherm and pseudo-second-order model, respectively, which indicated the monolayer adsorption of Cs+ onto ACF-P1, ACF-P2, and ACF-P3 which were largely controlled by chemisorption. Overall, phosphoric acids containing different phosphate-based polyanions (PO43-, P2O74-, or P3O105-) enriched -OH and/or -COOH surface functional groups of ACF in addition to P-containing surface groups (PO, C-P-O, C-O-P, and P-O) and facilitated the Cs+ adsorption through surface complexation and electrostatic interactions.

Materials Containing Single-, Di-, Tri-, and Multi-Metal Atoms Bonded to C, N, S, P, B, and O Species as Advanced Catalysts for Energy, Sensor, and Biomedical Applications.

Modifying the coordination or local environments of single-, di-, tri-, and multi-metal atom (SMA/DMA/TMA/MMA)-based materials is one of the best strategies for increasing the catalytic activities, selectivity, and long-term durability of these materials. Advanced sheet materials supported by metal atom-based materials have become a critical topic in the fields of renewable energy conversion systems, storage devices, sensors, and biomedicine owing to the maximum atom utilization efficiency, precisely located metal centers, specific electron configurations, unique reactivity, and precise chemical tunability. Several sheet materials offer excellent support for metal atom-based materials and are attractive for applications in energy, sensors, and medical research, such as in oxygen reduction, oxygen production, hydrogen generation, fuel production, selective chemical detection, and enzymatic reactions. The strong metal-metal and metal-carbon with metal-heteroatom (i.e., N, S, P, B, and O) bonds stabilize and optimize the electronic structures of the metal atoms due to strong interfacial interactions, yielding excellent catalytic activities. These materials provide excellent models for understanding the fundamental problems with multistep chemical reactions. This review summarizes the substrate structure-activity relationship of metal atom-based materials with different active sites based on experimental and theoretical data. Additionally, the new synthesis procedures, physicochemical characterizations, and energy and biomedical applications are discussed. Finally, the remaining challenges in developing efficient SMA/DMA/TMA/MMA-based materials are presented.

Layered hydrated-titanium-oxide-laden reduced graphene oxide composite as a high-performance negative electrode for selective extraction of Li via membrane capacitive deionization.

In this work, we initially prepared layered lithium titanate (Li2TiO3) using a solid-state reaction. Then Li+ of Li2TiO3 were acid-eluded with Hydrochloric acid to obtain hydrated titanium oxide (H2TiO3). Different weight percentages (50%, 60%, 70%, 80%, and 90%) of the as-prepared H2TiO3 were deposited on a conductive reduced graphene oxide (rGO) matrix to obtain a series of rGO/ H2TiO3 composites. Of the prepared composites, rGO/H2TiO3-60% showed excellent current density, high specific capacitance, and rapid ion diffusion. An asymmetric MCDI (membrane capacitive deionization) cell fabricated with activated carbon as the anode and rGO/H2TiO3-60% as the cathode displayed outstanding Li+ electrosorption capacity (13.67 mg g-1) with a mean removal rate of 0.40 mg g-1 min-1 in a 10 mM LiCl aqueous solution at 1.8 V. More importantly, the rGO/H2TiO3-60% composite electrode exhibited exceptional Li+ selectivity, superior cyclic stability up to 100,000 s, and a Li+ sorption capacity retention of 96.32% after 50 adsorption/desorption cycles. The excellent Li+ extraction obtained by MCDI using the rGO/H2TiO3-60% negative electrode was putatively attributed to: (i) ion exchange between Li+ and H+ of H2TiO3; (ii) the presence of narrow lattice spaces in H2TiO3 suitable for selective Li+ capture; (iii) capture of Li+ by isolated and hydrogen-bonded hydroxyl groups of H2TiO3; and (iv) enhanced interfacial contact and transfer of large numbers of Li+ ions from the electrolyte to H2TiO3 achieved by compositing H2TiO3 with a highly conductive rGO matrix.

Efficient lithium extraction using redox-active Prussian blue nanoparticles-anchored activated carbon intercalation electrodes via membrane capacitive deionization.

Global demand for lithium (Li) resources has dramatically increased due to the demand for clean energy, especially the large-scale usage of lithium-ion batteries in electric vehicles. Membrane capacitive deionization (MCDI) is an energy and cost-efficient electrochemical technology at the forefront of Li extraction from natural resources such as brine and seawater. In this study, we designed high-performance MCDI electrodes by compositing Li+ intercalation redox-active Prussian blue (PB) nanoparticles with highly conductive porous activated carbon (AC) matrix for the selective extraction of Li+. Herein, we prepared a series of PB-anchored AC composites (AC/PB) containing different percentages (20%, 40%, 60%, and 80%) of PB by weight (AC/PB-20%, AC/PB-40%, AC/PB-60%, and AC/PB-80%, respectively). The AC/PB-20% electrode with uniformly anchored PB nanoparticles over AC matrix enhanced the number of active sites for electrochemical reaction, promoted electron/ion transport paths, and facilitated abundant channels for the reversible insertion/de-insertion of Li+ by PB, which resulted in stronger current response, higher specific capacitance (159 F g-1), and reduced interfacial resistance for the transport of Li+ and electrons. An asymmetric MCDI cell assembled with AC/PB-20% as cathode and AC as anode (AC//AC-PB20%) displayed outstanding Li+ electrosorption capacity of 24.42 mg g-1 and a mean salt removal rate of 2.71 mg g min-1 in 5 mM LiCl aqueous solution at 1.4 V with high cyclic stability. After 50 electrosorption-desorption cycles, 95.11% of the initial electrosorption capacity was retained, reflecting its good electrochemical stability. The described strategy demonstrates the potential benefits of compositing intercalation pseudo capacitive redox material with Faradaic materials for the design of advanced MCDI electrodes for real-life Li+ extraction applications.

Iron oxide (Fe3O4)-laden titanium carbide (Ti3C2Tx) MXene stacks for the efficient sequestration of cationic dyes from aqueous solution.

We prepared two-dimensional (2D) stack-structured magnetic iron oxide (Fe3O4) nanoparticle anchored titanium carbide (Ti3C2Tx) MXene material (Ti3C2Tx/Fe3O4). It was used as a potential adsorbent to remove carcinogenic cationic dyes, such as methylene blue (MB) and rhodamine B (Rh B), from aqueous solutions. Ti3C2Tx/Fe3O4 exhibited maximum adsorption capacities of 153 and 86 mg g-1 for MB and Rh B dyes, respectively. Batch adsorption experimental data fits the Langmuir model well, revealing monolayer adsorption of MB and Rh B onto the adsorption sites of Ti3C2Tx/Fe3O4. Additionally, Ti3C2Tx/Fe3O4 showed rapid MB/Rh B adsorption kinetics and attained equilibrium within 45 min. Moreover, Ti3C2Tx/Fe3O4 demonstrated recyclability over four cycles with high stability due to the presence of magnetic Fe3O4 nanoparticles. Furthermore, it exhibited remarkable selectivities of 91% and 88% in the presence of co-existing cationic and anionic dyes, respectively. Given the extraordinary adsorption capacities, Ti3C2Tx/Fe3O4 may be a promising material for the effective removal of cationic dyes from aqueous media.