Removal of Organic Micropollutants from Water by Macrocycle‐Containing Covalent Polymer Networks

Abstract

Access to clean drinking water is a recognized societal need that touches on the health and livelihood of millions of people worldwide. This is providing an incentive to develop new water‐treatment technologies. Traditional technologies, while widespread, are usually inefficient at removing organic pollutants from sewage or so‐called grey water. Macrocycle‐containing covalent polymer networks have begun to attract attention in the context of water treatment owing to the inherent stability provided by the polymer backbones and their ability to capture micropollutant guests as the result of tunable macrocycle‐based host–guest interactions. In this Minireview, we summarize recent advances (from 2016 to mid‐2020) involving the removal of organic micropollutants from water using macrocycle‐containing covalent polymer networks. An overview of future challenges within this subfield is also provided.

Effective and Rapid Removal of Polar Organic Micropollutants from Water by Amide Naphthotube‐Crosslinked Polymers

“…Thed ifferent adsorption kinetics for different micropollutants may be determined by their different size,f unctional groups,a nd interactions with the linkers in the polymer network during their intra-particle diffusion. [20] In general, these values are comparable to or higher than those of other macrocycle-crosslinked polymers to nonpolar or charged organic micropollutants, [4] and are significantly higher than those of other conventional adsorbents.For example,the adsorption rate constant of P2 to nitrobenzene is two orders of magnitude higher than that of the granular activated carbons [21] and three or more orders of magnitude higher than that of magnetic diatomite. [22] Thes uperior adsorption kinetics of P2 over other adsorbents was also observed for 4-nitrophenol, [23] benzocaine, [24] isoproturon, [21] and benzidine.…”

“…Since 2016, several cross-linked polymers containing macrocyclic hosts [4] have emerged as an ew class of effective adsorbents for the remediation of organic micropollutants in water. Thea dsorptions were proven to heavily rely on the host-guest binding property of the macrocyclic hosts.T his leads to at least two advantages:a)the adsorption selectivity and capacity can be well engineered by using different macrocyclic hosts.U ntil now,t he macrocyclic hosts used for this purpose include cyclodextrins, [5] pillararenes, [6] calixarenes, [7] "Texas-sized" box [8] and calix [4]pyrrole.…”

“…Since 2016, several cross-linked polymers containing macrocyclic hosts [4] have emerged as an ew class of effective adsorbents for the remediation of organic micropollutants in water. Thea dsorptions were proven to heavily rely on the host-guest binding property of the macrocyclic hosts.T his leads to at least two advantages:a)the adsorption selectivity and capacity can be well engineered by using different macrocyclic hosts.U ntil now,t he macrocyclic hosts used for this purpose include cyclodextrins, [5] pillararenes, [6] calixarenes, [7] "Texas-sized" box [8] and calix [4]pyrrole. [9] These crosslinked polymers have been shown to be very effective for removing charged and nonpolar organic micropollutants from water;b )n oncovalent interactions between hosts and guests are sensitive to environmental conditions,a nd thus these polymers can be easily regenerated by washing with organic solvents or acidic/basic solution.…”

Calix[4]pyrrole‐based Crosslinked Polymer Networks for Highly Effective Iodine Adsorption from Water

“…To date,macrocycle-based POPs have shown promise in anumber of applications,i ncluding gas adsorption and separation and pollutant adsorption, reflecting their ability to encapsulate various guest molecules with different sizes,s hapes,a nd charges. [7] Among the pollutants that have been targeted with POPs, radioactive iodine (e.g., 129 Io r 131 I) has received particular attention, both as at estbed for assessing the viability of the POP-based remediation approach and because of the importance of this micropollutant per se.R adioactive iodine, released into the environment through nuclear detonations and reactor accidents,isknown for its adverse effect on both human health and the broader environment. [8] Va rious porous adsorbents have been developed to capture iodine.…”

Aggregation Mode, Host‐Guest Chemistry in Water, and Extraction Capability of an Uncharged, Water‐Soluble, Liquid Pillar[5]arene Derivative

“…Such systems have been used for sensing, in catalysis, and for the preparation of new materials such as supramolecular polymers and gels. [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] As Nature operates in water, it is not surprising that host‐guest and supramolecular chemistry in water have become the focus of research. [ 19 , 20 , 21 , 22 , 23 , 24 ] This occurred due to the introduction of new families of macrocycles, some of which are water‐soluble (like cucurbiturils)[ 25 , 26 ] and others that can be made water‐soluble relatively easily (like calixarenes and pillararenes).…”