High Efficiency Adsorption and Removal of Selenate and Selenite from Water Using Metal–Organic Frameworks

Abstract

A series of zirconium-based, metal-organic frameworks (MOFs) were tested for their ability to adsorb and remove selenate and selenite anions from aqueous solutions. MOFs were tested for adsorption capacity and uptake time at different concentrations. NU-1000 was shown to have the highest adsorption capacity, and fastest uptake rates for both selenate and selenite, of all zirconium-based MOFs studied here. Herein, the mechanism of selenate and selenite adsorption on NU-1000 is explored to determine the important features that make NU-1000 a superior adsorbent for this application.

Water Purification: Adsorption over Metal‐Organic Frameworks

“…[5,73] For using MOFs as adsorbents to remove fluoride, the stability in fluoride solution was firstly considered by Zhong et al based on eleven water-stable MOFs (MIL-53 (Fe, Cr, Al), MIL-68 (Al), CAU-1, CAU-6, UiO-66 (Zr, Hf) and ZIFs-7, -8, -9). [65] Copyright 2015, American Chemical Society) and the adsorption data fits well with the Langmuir model and pseudo second-order kinetic model. Pore topology should also be taken into account.…”

“…[65][66][67][68] Zr-Based MOFs for adsorption of selenate and selenite were researched on NU-1000, UiO-66, UiO-67 and their derivatives, among which NU-1000 presents the highest adsorption capacity (85 mg•g 1 for selenate and 95 mg•g 1 for selenite, Table 2) and the fastest uptake rates of both selenate and selenite ( Figure 1B). [65][66][67][68] Zr-Based MOFs for adsorption of selenate and selenite were researched on NU-1000, UiO-66, UiO-67 and their derivatives, among which NU-1000 presents the highest adsorption capacity (85 mg•g 1 for selenate and 95 mg•g 1 for selenite, Table 2) and the fastest uptake rates of both selenate and selenite ( Figure 1B).…”

The dual capture of AsV and AsIII by UiO-66 and analogues

“…Interestingly, the uptake ratio for HCl-UiO-66| 9/12 in our standard 50 ppm initial As-exposure experiment levels out relatively quickly and does not change after 6 h: the As V uptake ratio at this time point, as well as after 24 h of exposure, only amounts to ∼60% of the available missing-linker sites (1.8 : 1 As V  : Zr 6 ) even though there is still excess As V in solution. 38 These data suggests that the As V uptake in HCl-UiO-66| 9/12 is probably dominated by an equilibrium-driven process, as demonstrated for organophosphorus 6 and selenates 42 uptakes in UiO-type MOFs. This is indeed the case: as the As-exposure concentration is increased to 100 ppm, all of the available missing-linker sites (3 : 1 As V  : Zr 6 ) for HCl-UiO-66| 9/12 can be filled after 24 h (Fig.…”

“…2, bottom section) in our HCl-UiO-type MOF crystals and form strong Zr–O–M bonds through the so-called anion-exchange mechanism. 39,42 Analyses of the diffuse-reflectance infrared Fourier-transformed spectroscopy (DRIFTS) data revealed a broad peak (800–900 cm –1 ) indicative of the adsorbed As V . The blue-shifted shoulder peak at 898 cm –1 could be due to formation of As–OZr stretch as observed for zirconium arsenate crystals.…”

Uncovering Structural Opportunities for Zirconium Metal–Organic Frameworks via Linker Desymmetrization

“…To reach adsorption equilibrium, 10 mg PCN-903-(CH 3 ) 6 was immersed in the aqueous solutions for 24 h, which was followed by inductively coupled plasma mass spectrometry (ICP-MS) analysis of supernatant fraction to determine the remaining SeO 3 2− concentration. [30,31] The kinetic behavior for SeO 3 2− was subsequently investigated (Figure 5b and Table S5, Supporting Information). The maximum Se capacity of PCN-903-(CH 3 ) 6 was calculated as 75.5 mg g −1 , which exhibits one of the highest adsorption capacities among MOF absorbents (Figure 5a and Table S4, Supporting Information).…”