Cationic Covalent Organic Nanosheets for Rapid and Selective Capture of Perrhenate: An Analogue of Radioactive Pertechnetate from Aqueous Solution

Abstract

Capture of radioactive TcO4 – from nuclear wastes is extremely desirable for waste disposal and environmental restoration. Here, we report the synthesis of hydrolytically stable cationic covalent organic nanosheets (iCON) for efficient uptake of ReO4 –, a nonradioactive surrogate of TcO4 –. The iCON combines cationic guanidine-based knots with hydroxyl anchored neutral edge units and chloride ions loosely bonded in the pores, rendering extremely fast exchange kinetics toward ReO4 – with high uptake capacity of 437 mg g–1 and prominent distribution coefficient of 5.0 × 105. The removal efficiency remains stable over a pH range of 3–12 and allows selective capture of ReO4 – in the presence of excessive competing anions such as NO3 –, CO3 2–, PO4 3– and SO4 2– with good removal efficiency for ReO4 – in a simulated Hanford LAW Melter Recycle Stream. Anion exchange between the ReO4 – in solution and the chloride ion in iCON plays dominant role in the adsorption of ReO4 –. The iCON shows promise for effective removal of radioactive 99Tc from nuclear waste.

Covalent Organic Frameworks for Water Treatment

“…Beyond toxic heavy metal and radionuclide ion capture, there are several reports on COFs as adsorbents for lanthanide ions (Nd 3+ ), [ 98 ] perrhenate (ReO 4 − ), [ 99 ] phosphorus (PO 4 3− ), [ 100 ] arsenic (AsO 4 3− ), [ 100 ] organic compounds, [ 66,67,101–104 ] and even proteins. [ 105 ] Valtchev's group reported a carboxy‐functionalized COF (3D‐COOH‐COF) through the postsynthetic modification method and applied the 3D‐COOH‐COF in selective adsorption for lanthanide ion Nd 3+ over Sr 2+ and Fe 3+ .…”

“…This material combined cationic guanidine‐based knots with hydroxyl units and chloride ions bonded in the pools, which led to fast exchange kinetics toward ReO 4 − with high capacity of 437 mg g −1 . [ 99 ] Yang et al. applied EB‐COF:Br as an adsorbent for phosphate and arsenate removal from water with adsorption capacity for the phosphate of 35.3 mg g −1 and for arsenate of 53.1 mg g −1 .…”

Orderly Porous Covalent Organic Frameworks-based Materials: Superior Adsorbents for Pollutants Removal from Aqueous Solutions

“…These advantages, together with the characteristics of predesigned structure, ordered porous structure, and adjustable physicochemical properties, make COFs promising next-generation materials with remarkable high sorption capacities for radioactive/toxic metal ions and organic contaminants. 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 …”

Dual-functional ionic porous organic framework for palladium scavenging and heterogeneous catalysis

“…25 In addition, the ionic interface in IPOFs triggers electrostatic interactions with guest molecules or ions that could enhance their performances in CO 2 capture and in trapping ionic pollutants. 26,[29][30][31][32] Therefore, the design of IPOFs with tunable nanostructures, compositions and properties could further extend their applications in adsorption and catalysis.…”