Highly Defective UiO-66 Materials for the Adsorptive Removal of Perfluorooctanesulfonate

Abstract

Perfluorooctanesulfonate (PFOS) is a persistent organic pollutant that is bioaccumulative and toxic. While its use in most countries has been restricted to certain industrial applications due to environmental and health concerns, chrome plating and semiconductor manufacturing facilities are industrial point sources of PFOS-containing wastewater. Current remediation technologies are ineffective at treating these highly concentrated industrial effluents. In this work, UiO-66 metal–organic frameworks (MOFs) of several defect concentrations were studied as sorbents for the removal of PFOS from concentrated aqueous solutions. PFOS sorption isotherms indicated that defective UiO-66, prepared with HCl as a modulator, had a maximum Langmuir sorption capacity of 1.24 mmol/g, which was ∼2× greater than powdered activated carbon (PAC), but ∼2× less than that of a commercial ion-exchange resin. Defective UiO-66 adsorbed PFOS 2 orders of magnitude faster than the ion-exchange resin. Large pore defects (∼16 and ∼20 Å) within the framework were critical to the increased adsorption capacity due to higher internal surface area and an increased number of coordinatively unsaturated Zr sites to bind the PFOS head groups. Of the common co-contaminants in chrome plating wastewaters, chloride ions have a negligible effect on PFOS sorption, while sulfate and hexavalent chromium anions compete for cationically charged adsorption sites. These materials were also effective adsorbents for the shorter-chain homologue, perfluorobutanesulfonate (PFBS). The enhanced PFOS and PFBS adsorptive properties of UiO-66 highlight the advantage of structurally defective MOFs as a water treatment approach toward environmental sustainability.

Rational Design of MOF‐Based Hybrid Nanomaterials for Directly Harvesting Electric Energy from Water Evaporation

“…It is reported that the UIO‐66 synthesized with the acid modulator (e.g., acetic acid) possesses numerous defects due to missing of organic linkers, resulting in unsaturated coordination of the Zr clusters [ 29,32 ] and subsequently the positively charged surface of UIO‐66. [ 33 ] Similar to the previously reported materials with positively charged surface, [ 13–16 ] since there are negatively charged OH − ions in water, EDLs with the excess OH − ions can form in the capillary channels. Therefore, when the water molecules move through the capillary channels driven by the water evaporation, the collective movement of negatively charged OH − ions results in a high electric potential at the bottom electrode and a low electric potential at the top electrode (Figure 3a).…”

Modulated synthesis of thiol-functionalized fcu and hcp UiO-66(Zr) for the removal of silver(i) ions from water

“…hcp UiO-66 was, so far, obtained by either using a terephthalate-containing ionic liquid or poly(ethylene terephthalate) as linker or by using large amounts of hydrochloric acid or acetic acid modulators. 49,53,54,55 To the best of our knowledge there is no functionalized hcp UiO-66 known. PXRD patterns showed the transition to the hcp structure starting with the use of ~80eq HMAc in relation to ZrCl 4 (details see Section S14, ESI †).…”

“…BET surface areas of the MAcmodulated fcu MOFs with 1290-1070 m 2 /g compare well with the surface areas of unmodulated UiO-66 of 1100 m 2 /g, 52 and modulated UiO-66 ranging from 700 up to 1600 m 2 /g, 3,52,58 Also, the BET surface area of hcp UiO-66-MAc-100eq is in good accordance with the literature. 49,53,54,55 The total surface area was differentiated in the internal micropore surface area (A Int ) and the external surface area (A Ext ) by the t-plot and V-t-method ( Table 2). The external surface area refers to all non-microporous areas and includes the surface area originating from meso-and macropores, i.e pores with diameters larger than 2 nm.…”

“…The total pore volume V total corresponds to the literature of small sized fcu UiO-66 particles, 59 which ranges from 0.3 to 0.6 cm 3 /g 60 and to the hcp UiO-66, for which V total values of 0.32 and 0.45 cm 3 /g were found. 53,54,55 Figure 3 N 2 sorption isotherm of UiO-66-MAc-10eq, 30eq, 50eq and 100eq at 77 K. Filled symbols: adsorption; empty symbols: desorption. a Multi-Point BET between p/p 0 = 0.01 -0.05.…”

Magnetically recoverable carbon-coated iron carbide with arsenic adsorptive removal properties

“…Fitted values for the Langmuir constant and the maximum sorption capacity were negative for Fe 3 C@C, indicating that the monolayer adsorption assumption of the model did not apply for arsenic adsorbing onto this nanopowder (Table S3). Multilayer adsorption of arsenic seems to play more of a role in arsenic adsorption onto the surface of Fe 3 C@C because of its porous nature [78]. The fitted values for the Langmuir constant and the maximum sorption capacity for c-Fe 3 O 4 were negative also.…”