Synthesis and characterization of a plat sheet potassium ion sieve membrane and its performances for separation potassium

Preparation of Alumina-Sphere-Supported Potassium Chabazite Zeolite Membrane with Excellent Potassium Extraction Performance at Room Temperature

In this paper, a potassium chabazite (KCHA) zeolite membrane was prepared by coating KCHA zeolite on the surface of a porous alumina sphere. The performance of the KCHA zeolite membrane in extracting potassium from seawater and sea bittern at room temperature was studied in detail. The XRD results show that the prepared KCHA zeolite was a KCHA membrane. The EDS test indicated that the potassium content of the KCHA zeolite membrane reached a value of 18.33 wt.%. The morphology of the KCHA zeolite grown on the surface of the alumina sphere was similar to a sphere, and it had good symmetry. The potassium ion-exchange capacities of the KCHA zeolite membrane reached 32 mg/g in seawater and 77 mg/g in sea bittern at room temperature. Ion exchange between the ammonium ions and potassium ions in the KCHA zeolite membrane could be completed in a short time at room temperature. The KCHA zeolite membrane was proven to have good reusability in seawater and sea bittern. The selective ion-exchange mechanism of the KCHA zeolite membrane was controlled by a specific K⁺ ion memory.

Potassium-Ion Recovery with a Polypyrrole Membrane Electrode in Novel Redox Transistor Electrodialysis

Conductive polymers are potential selective ion-exchange membrane materials. In this study, a novel redox transistor electrodialyzer consisting of two chambers separated by a polypyrrole (PPy) membrane electrode was designed for potassium ion (K⁺) recovery from water. The PPy membrane electrode was fabricated by depositing PPy on a stainless-steel wire mesh through the electrochemical method. Based on ion-exchange results, the PPy membrane exhibited electrodialysis selectivity for K⁺ in the presence of Na⁺, with a K⁺/Na⁺ separation factor of 2.10. Adding modified active carbon to PPy provided a larger electroactive area and better conductivity, resulting in higher ion-exchange capacity (1.04 mmol/L) compared with the original PPy membrane. Even for seawater containing a very low concentration of K⁺ (16.18 mmol/L), the PPy membrane still demonstrated K⁺ selectivity (separation factor of 2.18). Energy consumption in the electrodialyzer was 3.80 kW h/kg K, which was 37% lower than that in traditional electrodialysis. Furthermore, the PPy membrane exhibited antiscaling/fouling ability with the help of a pulse voltage. These findings highlight a novel redox transistor electrodialysis process with great potential application in K⁺ recovery from wastewater with relatively low energy consumption.

Cucurbit[7]uril-Based Metal-Organic Rotaxane Framework for Dual-Capture of Molecular Iodine and Cationic Potassium Ion

Metal-organic rotaxane frameworks (MORFs) attracted much attention in the past years for construction of intelligent functional materials. Herein, a one-pot synthesis is reported of a three-dimensional (3D) cucurbit[7]uril (Q[7])-based MORF under hydrothermal conditions, namely Q[7]-MORF-1, formed by encapsulating the anionic benzoate moieties of the tricarboxylate ligand into the cavity of Q[7]. Furthermore, Q[7]-MORF-1 shows dual-capture capacity for iodine and K⁺ selectively among the alkali metal ions. The captured molecular iodine is included in the cavity of Q[7] through halogen-bonding interactions and the K⁺ cations are positioned at the carbonyl port of the Q[7] through K-O coordination interactions.