CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Singapore Patent Application No. 10201405486X, filed September 4, 2014, the contents of which being hereby incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The invention relates to a method for removing cesium from a waste material. In particular, the removal of cesium from the waste material is achieved by the use of herein disclosed macrocyclic aromatic pentamers.

BACKGROUND

Cesium-137 ( ¹³⁷ Cs) is one of the only two radioactive elements (the other is Strontium-90, Sr) among many produced from thermal neutron fission of uranium- 235 ( ²³⁵ U) in nuclear power plants worldwide that is characterized by a high fission yield of 6.337% (the second highest after 6.911% for ¹³⁵ Cs), a relatively long half-life of 30.2 years and a high decay energy of 1176 keV.

With respect to many other radioactives that are of low energy, low yield or short half-life,

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Cs is considered the major long-term contaminant for both Chernobyl disaster on April 26, 1986 and Fukushima Daiichi nuclear disaster on March 11, 2011. In particular for the latter disaster, ¹³⁷ Cs receives "prime" attention because the radioactives released into the environment are mostly volatile elements such as ¹³¹ I, ¹³⁴ Cs and ¹³⁷ Cs, among which ¹³⁴ Cs and ¹³¹ I have a respective half-life of 2.07 years and 8.02 days. In other words, 99.9% of ¹³¹ I will decay into a stable non-radioactive safe isotope ^I31 Xe in just 80 days after ten half-life cycles. In June 2011, just four months after Fukushima Daiichi nuclear disaster, the Japanese government estimated the radiation release of ¹³⁷ Cs to be as large as 7.7 <10 ¹⁷ Becquerels (Bq), representing the largest accidental release into the ocean in history. The release of ¹³⁴ Cs into the environment is estimated to be on the same scale as ¹³⁷ Cs. In fact, on February 13, 2014, Tokyo Electric Power Company (TEPCO) reported that 37,000 Bqs of ¹³⁴ Cs and 93,000 Bqs of ¹³⁷ Cs were detected per liter of groundwater sampled from a monitoring well.

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For Cs, this is 93 times the government's safety limit.

While non-radioactive ¹³³ Cs is not a major chemical environmental pollutant as the median lethal dose (LD ₅₀ ) value for ¹³³ CsCl in mice is 2.3 g per kilogram that is comparable to the LD ₅₀ values of KC1 and NaCl, radioactive ¹³⁷ Cs is extremely toxic, and a single dose of 4.1 g of Cs per kilogram is lethal to dog within three weeks, and smaller amounts may cause infertility and cancer. The International Atomic Energy Agency and other sources have even warned that radioactive ¹³⁷ Cs could be used in radiological dispersion devices, or "dirty bombs". Moreover, Cs possesses a high mobility in biosphere and can be easily incorporated into terrestrial and aquatic organisms. Upon entering the body, ¹³⁷ Cs ions get more or less uniformly distributed throughout the body with higher concentration in muscle tissues and lower in bones, and pose a serious threat to human health.

Materials and technologies that can efficiently extract ¹³⁷ Cs and its other radioactive isotopes ( ¹³⁴ Cs and ¹³⁵ Cs) in a highly selective manner therefore are of high interest and urgently needed, which should offer high potentials in (i) remediating the ¹³⁷ Cs-contaminated environment (water, soils and air), (ii) removing radioactive ¹³⁷ Cs elements from nuclear power plants or nuclear waste tanks worldwide for storage before their leaks into the

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surrounding environments, (iii) removing Cs from Cs-containing radioactive fly ash after waste incineration, and (iv) developing ¹³⁷ Cs decorporation drugs for accelerated excretion of radiocesium from the human body.

However, highly selective removal of Cs ⁺ ions from contaminated water or nuclear waste is still a challenging task in view of the facts that Cs ions are water-soluble and behave similarly to potassium and sodium ions in terrestrial/aquatic ecosystems and that there is insufficiently accumulated knowledge and understanding on how the high amount of monovalent cations (Na ⁺ and ⁺ ) as found in seawater and nuclear wastes may compete with ¹³⁷ Cs ⁺ ions. For instance, Goossens and co-workers found that removal of 31% of Cs ⁺ ions in coagulation-flocculation stage and 25% by filtration can be achieved by using alum as coagulants with activated carbon and activated silica, followed by sand filtering. This implies that conventional coagulation process for water purification is not a favored method to remove soluble Cs ⁺ ions from contaminated water sources.

Over the past few decades particularly since Fukushima Daiichi nuclear disaster on March 11, 201 1, there have been intense efforts dedicated to developing advanced materials and technologies for selective removal of radioactive Cs ⁺ ions. Notable advances have been largely made by means of (i) solid phase/solvent extraction using crown ethers, dicarbollides, calixarenes, functionalized latex, and clay, etc, (ii) inorganic ion exchange using zeolites, chalcogenido clusters, Prussian blue, crystalline silicotitanates, metal oxides, etc, and (iii) organic ion exchange using polystyrenes, phenolic resins, resorcinol- formaldehyde, polysaccharides, carbonaceous materials, etc. These technologies nevertheless have met with limited success, leaving room for further improvements due to low affinity for Cs ⁺ ions, high cost or difficulties in separating materials from wastes after Cs ⁺ sorption, etc.

Moreover, few studies have focused on the removal of Cs ⁺ ions down to ultra-low concentrations such as sub-ppb levels. In one example, binary conjugate adsorbent made by direct immobilization of dibenzo-24-crown-8 ether onto inorganic mesoporous silica enables the removal of CsCl by 99% at pH 7 with the residual concentration of Cs ⁺ ions down to 20 ppb. This is achieved, however, by using a very large absorbent/Cs ⁺ mass ratio of 500: 1. The ability of this conjugate adsorbent to selectively remove Cs ⁺ ions was tested in the presence of either ⁺ or Na ⁺ ions. A respective extraction efficiency of 98%, 92% and 65% for CsCl was obtained at absorbent:CsCl: Cl mass ratios of 500: 1.0:2.5, 500: 1.0:5.0, and 500: 1.0: 10. As for NaCl that exerts less influence on the sorption of CsCl by the adsorbent, the sorption efficiency remain as high as 99% at a mass ratio at 500: 1.0: 10 (absorbent:CsCl:NaCl), but decreases to 68% with an increased mass ratio to 500: 1.0:20. In another example, ternary spongiform adsorbent PU/CNT/DM/PB made up of polyurethane (PU) prepolymers, carbon nanotubes (CNTs), diatomite (DM), and Prussian-blue (PB) was shown to be capable of removing Cs ⁺ ions by 95.96%) and lowering down the concentration of Cs ⁺ ions from 10 ppm to 400 ppb similarly with the use of a large excessive amount of absorbent (mass ratio of absorbent/Cs ⁺ = 750: 1).

Therefore, there remains a need to provide for a more efficient and more cost effective method of removing Cs ⁺ ions by using less amount of absorbent. SUMMARY

It is herein described the use of macrocyclic aromatic pentamers, such as but not limited to macrocyclic pyridone pentamers, containing five convergently aligned electron-rich carbonyl oxygen atoms for highly selective high-capacity cesium removal from plain water, ground water, high-salinity, highly acidic, or highly alkaline liquid waste, showing high potential in

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(i) remediating Cs-contaminated environment (water, soils and air), (ii) removing radioactive Cs ⁺ from nuclear power plants or nuclear waste tanks, (iii) removing ¹³⁷ Cs- containing radioactive fly ash after waste incineration, and (iv) developing ¹³⁷ Cs decorporation drugs for accelerated excretion of radiocesium from the human body.

Thus, according to various embodiments of the invention, there is disclosed a method for removing Cs ⁺ from a waste material. The method includes:

contacting a waste material containing Cs ⁺ with a compound of Formula I

(1)

wherein:

A, B, C, D and E are independently selected from the group consisting of:

Ri, R ₂ , R ₃ , R4, R ₅ , and R ₆ are independently H, halogen, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl, a substituted or unsubstituted heterocycle, a substituted or unsubstituted aryl, a substituted or unsubstituted alkyl-aryl, a substituted or unsubstituted alkyl-heterocycle, a substituted or unsubstituted heteroaryl, -NRR', -NR, -OR, -SR, -CN, -N0 ₂ , -C(0)-R, -COOR, -NR'-C(0)-R, - C(0)-NRR', -C(NR)-R', -S0 ₂ -R, -(S0 ₂ )-OR, -C(S)-R, or -C(S)-NRR',

R and R' are independently selected from the group consisting of H and a substituted or unsubstituted alkyl.

According to various embodiments of the invention, the method includes providing a biphasic extraction system, wherein the biphasic extraction system comprises a first phase and a second phase, wherein the first phase comprises the waste material containing Cs ⁺ , wherein the second phase comprises the compound of Formula I in an organic solvent and further comprises allowing time for extraction of Cs ⁺ from the waste material by the compound of Formula I.

According to various alternative embodiments of the invention, the method includes contacting the waste material containing Cs ⁺ with the compound of Formula I in a column filtration system. Preferably, the compound of Formula I is conjugated to a porous solid support.

In preferred embodiments, the compound of Formula I has the following structure 1

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead generally being placed upon illustrating the principles of various embodiments. In the following description, various embodiments of the invention are described with reference to the following drawings. Fig. 1 shows the column filtration system set-up for removing Cs ⁺ ions from solution as described in the examples. .

DESCRIPTION

The following detailed description refers, by way of illustration, specific details and embodiments in which the invention may be practised. These embodiments are described in sufficient detail to enable those skilled in the art to practise the invention. Other embodiments may be utilized and structural and chemical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. Various embodiments of present disclosure are directed to a method for removing radioactive cesium from radioactive ash and high salinity acidic or alkaline seawater and nuclear wastes, for example.

In particular, selective macrocyclic cesium-binders for high capacity ultralow concentration cesium removal for selective decontamination of Cs-containing wastes are developed. With its suitably sized non-collapsible cavity of 1.4 A in radius formed by five convergently aligned interior-pointing carbonyl O-atoms, aromatic pentamers such as presently disclosed compounds are found to be able to tightly bind metal ions.

Thus, in accordance with various embodiments of the present invention, a method for removing Cs ⁺ from a waste material is described herein. The method includes providing a biphasic extraction system, whereby the biphasic extraction system includes a first phase and a second phase.

The first phase of the biphasic extraction system includes a waste material containing the Cs ⁺ to be removed. In some embodiments, the waste material may have a pH of 7. In alternative embodiments, the waste material may have a pH above 7. In yet other embodiments, the waste material may have a pH below 7.

In various embodiments, the waste material may be sea water at pH 7.6, acidic nuclear waste, or alkaline nuclear waste. The second phase of the biphasic extraction system includes a compound of Formula I in an organic solvent

wherein:

A, B, C, D and E are independently selected from the group consisting of:

R _l5 R ₂ , R ₃ , R ₄ , R ₅ , and R are independently H, halogen, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl, a substituted or unsubstituted heterocycle, a substituted or unsubstituted aryl, a substituted or unsubstituted alkyl-aryl, a substituted or unsubstituted alkyl-heterocycle, a substituted or unsubstituted heteroaryl, -NRR', -NR, -OR, -SR, -CN, -N0 ₂ , -C(0)-R, -COOR, -NR'-C(0)-R, - C(0)-NRR', -C(NR)-R\ -S0 ₂ -R, -(S0 ₂ )-OR, -C(S)-R, or -C(S)-NRR', and

R and R' are independently selected from the group consisting of H and a substituted or unsubstituted alkyl. The term "aliphatic", alone or in combination, refers to a straight chain or branched chain hydrocarbon comprising at least one carbon atom. Aliphatics include alkyls, alkenyls, and alkynyls. In certain embodiments, aliphatics are optionally substituted, i.e. substituted or unsubstituted. Aliphatics include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, ethynyl, butynyl, propynyl, and the like, each of which may be optionally substituted. As used herein, aliphatic is not intended to include cyclic groups. The term "alkyl", alone or in combination, refers to a fully saturated aliphatic hydrocarbon. In certain embodiments, alkyls are optionally substituted. In certain embodiments, an alkyl comprises 1 to 30 carbon atoms, for example 1 to 20 carbon atoms, wherein (whenever it appears herein in any of the definitions given below) a numerical range, such as "1 to 20" or "C1-C20", refers to each integer in the given range, e.g. "C1-C20 alkyl" means that an alkyl group comprising only 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., up to and including 20 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-amyl, pentyl, hexyl, heptyl, octyl and the like. The term "alkoxy", alone or in combination, refers to an aliphatic hydrocarbon having an alkyl-O- moiety. In certain embodiments, alkoxy groups are optionally substituted. Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy, butoxy and the like. The term "alkenyl", alone or in combination, refers to an aliphatic hydrocarbon having one or more carbon-carbon double-bonds, such as two or three carbon-carbon double-bonds. In certain embodiments, alkenyls are optionally substituted, i.e. substituted or unsubstituted. In certain embodiments, an alkenyl comprises 2 to 15 carbon atoms, for example 2 to 10 carbon atoms. "C2-C15 alkenyl" means that an alkenyl group comprising only 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, 10 carbon atoms, 11 carbon atoms, 12 carbon atoms, 13 carbon atoms, 14 carbon atoms, or 15 carbon atoms. Examples of alkenyls include, but are not limited to, ethenyl, propenyl, butenyl, 1 ,4-butadienyl, pentenyl, hexenyl, 4-methylhex-l-enyl, 4-ethyl-2-methylhex- 1 -enyl and the like.

The term "alkynyl", alone or in combination, refers to an aliphatic hydrocarbon having one or more carbon-carbon triple-bonds, such as two or three carbon-carbon triple-bonds. In certain embodiments, alkynyls are optionally substituted, i.e. substituted or unsubstituted. In certain embodiments, an alkynyl comprises 2 to 15 carbon atoms, for example 2 to 10 carbon atoms. "C2-C15 alkynyl" means that an alkynyl group comprising only 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, 10 carbon atoms, 11 carbon atoms, 12 carbon atoms, 13 carbon atoms, 14 carbon atoms, or 15 carbon atoms. Examples of alkynyls include, but are not limited to, ethynyl, propynyl, butynyl, and the like.

The term "heterocycle" refers to a group comprising a covalently closed ring wherein at least one atom forming the ring is a carbon atom and at least one atom forming the ring is a heteroatom. Heterocyclic rings may be formed by three, four, five, six, seven, eight, nine, or more than nine atoms. Any number of those atoms may be heteroatoms (i.e., a heterocyclic ring may comprise one, two, three, four, five, six, seven, eight, nine, or more than nine heteroatoms). Herein, whenever the number of carbon atoms in a heterocycle is indicated (e.g., C1-C6 heterocycle), at least one other atom (the heteroatom) must be present in the ring. Designations such as "C1-C6 heterocycle" refer only to the number of carbon atoms in the ring and do not refer to the total number of atoms in the ring. It is understood that the heterocylic ring will have additional heteroatoms in the ring. In heterocycles comprising two or more heteroatoms, those two or more heteroatoms may be the same or different from one another. Heterocycles may be optionally substituted. Binding to a heterocycle can be at a heteroatom or via a carbon atom.

The term "heteroatom" refers to an atom other than carbon or hydrogen. Heteroatoms are typically independently selected from oxygen, sulfur, nitrogen, and phosphorus, but are not limited to those atoms. In embodiments in which two or more heteroatoms are present, the two or more heteroatoms may all be the same as one another, or some or all of the two or more heteroatoms may each be different from the others.

The term "aromatic" refers to a group comprising a covalently closed planar ring having a delocalized 7T-electron system comprising 4n+2 τ electrons, where n is an integer. Aromatic rings may be formed by five, six, seven, eight, nine, or more than nine atoms. Aromatics may be optionally substituted. Examples of aromatic groups include, but are not limited to phenyl, naphthalenyl, phenanthrenyl, anthracenyl, tetralinyl, fluorenyl, indenyl, and indanyl. The term aromatic includes, for example, benzenoid groups, connected via one of the ring- forming carbon atoms, and optionally carrying one or more substituents selected from an aryl, a heteroaryl, a cycloalkyl, a non-aromatic heterocycle, a halo, a hydroxy, an amino, a cyano, a nitro, an alkylamido, an acyl, a C1-C6 alkoxy, a C1-C6 alkyl, a C1-C6 hydroxyalkyl, a C1-C6 aminoalkyl, an alkylsulfenyl, an alkylsulfmyl, an alkylsulfonyl, an sulfamoyl, or a trifluoromethyl. In certain embodiments, an aromatic group is substituted at one or more of the para, meta, and/or ortho positions. Examples of aromatic groups comprising substitutions include, but are not limited to, phenyl, 3-halophenyl, 4-halophenyl, 3-hydroxyphenyl, 4-hydroxyphenyl, 3-aminophenyl, 4-aminophenyl, 3-methylphenyl, 4- methylphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 4-trifluoromethoxyphenyl, 3- cyanophenyl, 4-cyanophenyl, dimethylphenyl, naphthyl, hydroxynaphthyl, hydroxymethylphenyl, (trifluoromethyl)phenyl, alkoxyphenyl, 4-mo holin-4-ylphenyl, 4- pyrrolidin-l-ylphenyl, 4-pyrazolylphenyl, 4-triazolylphenyl, and 4-(2-oxopyrrolidin-l- yl)phenyl.

The term "aryl" refers to an aromatic ring wherein each of the atoms forming the ring is a carbon atom. Aryl rings may be formed by five, six, seven, eight, nine, or more than nine carbon atoms. Aryl groups may be optionally substituted.

The term "heteroaryl" refers to an aromatic heterocycle. Heteroaryl rings may be formed by three, four, five, six, seven, eight, nine, or more than nine atoms. Heteroaryls may be optionally substituted. Examples of heteroaryl groups include, but are not limited to, aromatic C3-C8 heterocyclic groups comprising one oxygen or sulfur atom or up to four nitrogen atoms, or a combination of one oxygen or sulfur atom and up to two nitrogen atoms, and their substituted as well as benzo- and pyrido-fused derivatives, for example, connected via one of the ring-forming carbon atoms. In certain embodiments, heteroaryl groups are optionally substituted with one or more substituents, independently selected from halo, hydroxy, amino, cyano, nitro, alkylamido, acyl, C1-C6 alkoxy, C1-C6 alkyl, C1-C6 hydroxyalkyl, C1-C6 aminoallcyl, alkylamino, alkylsulfenyl, alkylsulfmyl, alkylsulfonyl, sulfamoyl, or tnfluoromethyl. Examples of heteroaryl groups include, but are not limited to, unsubstituted and mono- or di-substituted derivatives of furan, benzofuran, thiophene, benzothiophene, pyrrole, pyridine, indole, oxazole, benzoxazole, isoxazole, benzisoxazole, thiazole, benzothiazole, isothiazole, imidazole, benzimidazole, pyrazole, indazole, tetrazole, quinoline, isoquinoline, pyridazine, pyrimidine, purine and pyrazine, furazan, 1,2,3- oxadiazole, 1,2,3- thiadiazole, 1 ,2,4-thiadiazole, triazole, benzotriazole, pteridine, phenoxazole, oxadiazole, benzopyrazole, quinolizine, cinnoline, phthalazine, quinazoline, and quinoxaline. In some embodiments, the substituents are halo, hydroxy, cyano, 0-Cl-C6-alkyl, C1-C6 alkyl, hydroxy-Cl-C6-alkyl, and amino-Cl-C6-alkyl.

The term "non-aromatic ring" refers to a group comprising a covalently closed ring that is not aromatic.

The term "alicyclic" refers to a group comprising a non-aromatic ring wherein each of the atoms forming the ring is a carbon atom. Alicyclic groups may be formed by three, four, five, six, seven, eight, nine, or more than nine carbon atoms. In certain embodiments, alicyclics are optionally substituted, i.e. substituted or unsubstituted. In certain embodiments, an alicyclic comprises one or more unsaturated bonds, such as one or more carbon-carbon double-bonds.

Alicyclics include cycloalkyls and cycloalkenyls. Examples of alicyclics include, but are not limited to, cyclopropane, cyclobutane, cyclopentane, cyclopentene, cyclopentadiene, cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1 ,4-cyclohexadiene, cycloheptane, and cycloheptene.

The term "alkyl-aryl" refers to a group comprising an alkyl group bound to an aryl group. The term "alkyl-heterocycle" refers to a group comprising an alkyl group bound to a heterocycle group.

A "halo" or "halogen" group refers to fluorine, chlorine, bromine or iodine.

The method further includes allowing time for extraction of Cs ⁺ from the waste material by the compound of Formula I.

In various embodiments, R _l5 R ₂ , R ₃ , R4, R ₅ , and R ₆ are independently an alkyl substituted with one or more heteroatoms selected from the group consisting of O, halogen, N, S and P.

In alternative various embodiments, R _l5 R ₂ , R ₃ , R4, R ₅ , and R ₆ are independently an alkenyl substituted with one or more heteroatoms selected from the group consisting of O, halogen, N, S and P.

In yet other various embodiments, R _l5 R ₂ , R ₃ , R4, R , and R ₆ are independently an alkynyl substituted with one or more heteroatoms selected from the group consisting of O, halogen, N, S and P.

In certain disclosed embodiments, the compound of Formula I has the following structure 1

Pentamer structure 1 is one embodiment of the general structure of circularly folded aromatic pentamer of Formula I and carries four exteriorly arrayed straight octyl side chains. The core structure of pentamer of Formula I includes five units A-E interconnected by five amide bonds wherein A, B, C, D and E are independently Fl , F2, F3, F4, and F5, and can be exemplified by the pentamer structure 1 comprised of five F2.

In various embodiments, each of Ri is unsubstituted CI -CIO alkyl or alkoxy. For example, in the pentamer structure 1 , each of Ri is unsubstituted CI -CIO alkyl or alkoxy.

In alternative various embodiments, each of R _f is unsubstituted straight chain CI -CI O alkyl or H. For example, in the pentamer structure 1 , each of Ri is unsubstituted straight chain Cl- C10 alkyl or H. In preferred embodiments, in the pentamer structure 1 , Ri is CsH ₁₇ .

In various embodiments, the organic solvent containing the compound of Formula I includes at least one of a hydrocarbon, a halogenated hydrocarbon, an aryl, an ester, and an alcohol. For example, the organic solvent may include at least one of chloroform, dichloromethane, 1 ,2-dichloroethane, hexane, cyclohexane, benzene, toluene, ethyl acetate, and octanol. In various embodiments, the biphasic extraction system may include an equal volume of the waste material and the organic solvent. In other embodiments, the biphasic extraction system may include an unequal volume of the waste material and the organic solvent. For example, the biphasic extraction system may include a higher volume of the organic solvent than the volume of the waste material.

When using either solvent extraction or column filtration systems to remove Cs ⁺ ions, the ratio of the compound of Formula I to Cs ⁺ is not critically important and in general the higher the ratio, the better is the removal efficiency. In various embodiments, the molar ratio of the compound of Formula I to Cs ⁺ is between 0.5:1 and 80:1. For example, the molar ratio of the compound of Formula I to Cs ⁺ maybe 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, 15:1, 15.5:1, 16:1, 16.5:1, 17:1, 17.5:1, 18:1, 18.5:1, 19:1, 19.5:1, 20:1, 20.5:1, 21:1, 21.5:1, 22:1, 22.5:1, 23:1, 23.5:1, 24:1, 24.5:1, 25:1, 25.5:1, 26:1, 26.5:1, 27:1, 27.5:1, 28:1, 28.5:1, 29:1, 29.5:1, 30:1, 30.5:1, 31:1, 31.5:1, 32:1, 32.5:1, 33:1, 33.5:1, 34:1, 34.5:1, 35:1, 35.5:1, 36:1, 36.5:1, 37:1, 37.5:1, 38:1, 38.5:1, 39:1, 39.5:1, 40:1, 40.5:1, 41:1, 41.5:1, 42:1, 42.5:1, 43:1, 43.5:1, 44:1, 44.5:1, 45:1, 45.5:1, 46:1, 46.5:1, 47:1, 47.5:1, 48:1, 48.5:1, 49:1, 49.5:1, 50:1, 50.5:1, 51:1, 51.5:1, 52:1, 52.5:1, 53:1, 53.5:1, 54:1, 54.5:1, 55:1, 55.5:1, 56:1, 56.5:1, 57:1, 57.5:1, 58:1, 58.5:1, 59:1, 59.5:1, 60:1, 60.5:1, 61:1, 61.5:1, 62:1, 62.5:1, 63:1, 63.5:1, 64:1, 64.5:1, 65:1, 65.5:1, 66:1, 66.5:1, 67:1, 67.5:1, 68:1, 68.5:1, 69:1, 69.5:1, 70:1, 70.5:1, 71:1, 71.5:1, 72:1, 72.5:1, 73:1, 73.5:1, 74:1, 74.5:1, 75:1, 75.5:1, 76:1, 76.5:1, 77:1, 77.5:1, 78:1, 78.5:1, 79:1, 79.5:1, or 80:1. In one disclosed embodiment, the molar ratio of the compound of Formula I to Cs ⁺ is 2: 1. In another disclosed embodiment, the molar ratio of the compound of Formula I to Cs ⁺ is 4: 1.

In yet another disclosed embodiment, the molar ratio of the compound of Formula I to Cs ⁺ is 16: 1.

In a further disclosed embodiment, the molar ratio of the compound of Formula I to Cs ⁺ is 80:1. In various alternative embodiments, the method for removing Cs ⁺ from the waste material includes contacting the waste material containing Cs ⁺ with the compound of Formula I in a column filtration system. Preferably, the compound of Formula I is conjugated to a porous solid support. The porous solid supports can include, but are not limited to, porous glass, zeolite, zeolitelike materials, coral reef, porous organic materials such as porous polymer made of poly(methyl methacrylate) and carbon molecular sieves, porous inorganic materials such as macroporous ceramics, metal oxides, silica monoliths, and crystalline silicotitanates, organic/inorganic porous hybrid materials, pillared materials, clathrasils and clathrates, ordered mesoporous materials, etc

In order that the invention may be readily understood and put into practical effect, particular embodiments will now be described by way of the following non-limiting examples. EXAMPLES

SOLVENT EXTRACTION METHOD

Table 1. Extraction efficiencies (%) of 18 metal ions in their nitrate salts by macrocyclic host 1, 18-crown-6 ether, 21- crown-7 ether and valinomycin as determined by inductively coupled plasma mass spectrometry (ICP). ^a

Li*, Mg ^2÷ , Ca ² *, Ba ² *, A , Mn ^I+ , Fe ³⁺ , Total

Cs* Rb ⁺ Τ ⁺ Na ⁺

Co ^2" , Cr ^3" , NP, Zn ²⁺ , Cu ²⁺ , Pb ²⁺ , Cd ²⁺ Extraction*

1 90 31 23 19 10 7 - 180

" The concentration of each metal ion is set at 0.03 mM with a total concentration of 0.60 mM involving ail the 20 ions in H ₂ O, and that of macrocyclic host 1 is 0.12 mM in CHCI ₃ . Extractions were earned out in a biphasic system using equal volumes of ¾0 containing metal ions and CHCI3 containing organic host for 24 h at pH 7 at 25 "C. The [host]/[individual metal ion] ratio is 4:1. All the reported data are averaged values over six runs with a mean variation of less than 3%, and only extraction efficiencies of > 6% are listed. * Total extraction is the sum of all the measurable extraction efficiencies for the ions.

As shown in Table 1 , aromatic pentamer 1 reveals very interesting ion-differentiating ability toward 20 metal ions. In other words, pentamer 1 exhibits selective recognition and efficient extraction of several ions in the decreasing order of Cs ⁺ > Rb ²⁺ > Tl ⁺ > Ag ⁺ > ⁺ > Na ⁺ in the presence of many other metal ions using biphasic water-CHCl ₃ system. From Table 1, it can be seen that a single dose extraction using host (pentamer) 1 at 0.12 mM efficiently extracts 90% Cs ⁺ and lowers the concentration of Cs ⁺ from 4 ppm down to ppb level. To test whether or not host 1 still exhibits similarly high-capacity extractions of Cs ⁺ ions at the low concentrations, extractions of low-level Cs ⁺ ions by host 1 were carried out. In these experiments, Cs ⁺ ions were kept at 3.50 μΜ that corresponds to Cs ⁺ ions at 465.5 ppb level, and the concentration of host 1 was varied from 7 μΜ to 14 μΜ, which correspond to l :Cs ⁺ molar ratios of 2:1 and 4:1, respectively. Extractions were carried out in a biphasic system using equal volumes of H ₂ 0 containing Cs ₊ ions and CHC1 ₃ containing organic host 1 for 24 h at pH of 7.6 at 25 °C. As compiled in Table 2, at a 1/Cs ⁺ molar ratio of 4: 1 , more than 99% of CsN0 ₃ and CsCl are efficiently extracted by host 1. Table 2. Extraction efficiencies (%) of Cs ions in their nitrate and chloride salts by macrocyclic host 1 as determined by inductively coupled plasma mass spectrometry (ICP)."

Host l Molar Ratio CsNOj Sorption bv 1 Molar Ratio CsCl Sorption by 1

(μΜ) (l:CsN0 ₃ ) (%) (l:CsCl) (%)

7.00 2: 1 >87 2:1 >S8

14.00 4:1 >99 4:1 >99

" The concentration of both CsN0 ₃ and CsCl is 3.50 μΜ in H2O, and that of host 1 varies from 7.00 μΜ to 14.00 μΜ. Extractions were carried out in a biphasic system using equal volumes of Η2Ο containing Cs ^' ions and CHCl; containing organic host 1 for 24 h at pH 7 at 25 °C. The [host] [Cs ^" ] ratio ranges from 2 to 4.

For comparison, the macrocyclic ligands such as kryptofix222 and dibenzo-21-crown-7 known to strongly bind some alkaline metal ions both exhibit weak extractions of Cs ⁺ ions. At a ligand/Cs ⁺ molar ratio of 100:1, kryptofix222 hardly extracts CsN0 ₃ and marginably removes CsCl by -1%, while extraction efficiencies by dibenzo-21-crown-7 are 67% and 76% for CsN0 ₃ and CsCl, respectively. Similarly, valinomycin removes 62% CsCl at a ligand/Cs ⁺ molar ratio of 100: 1. The data from Table 2 strongly suggest that host 1 is highly efficient for removal of Cs ions from the nuclear wastes or contaminated seawater containing high concentrations of salts. A few more experiments were then carried out to evaluate the 1 -mediated Cs sorption efficiencies in highly acidic or alkaline sea water or nuclear wastes of high salinity. A total of four artificial solutions of high salinity at different pHs were prepared based on the actual concentrations of different ionic species found in sea water and liquid nuclear wastes. For some ions, the concentrations as prepared were higher than their actual values. Specifically, two artificial sea water solutions differ by the concentration of Cs+ ions, and were prepared to contain 0.48 M NaCl, 0.06 M Na ₂ S0 ₄ , 0.02 M KC1, 0.06 M MgCl ₂ and 0.02 M Ca(N0 ₃ ) ₂ at pH 7.6, followed by adding 2 mg/L of CsCl and 50 μg/L of CsCl to obtain the two artificial sea water solutions containing about 2 ppm Cs ⁺ and 50 ppb Cs ⁺ , respectively. The other two artificial nuclear waste solutions differ by pH, and were prepared to contain 4 M NaN0 ₃ , 0.5 M KN0 ₃ and various metal ions in their nitrate salts including 2 mg Cs ⁺ (about 2 ppm Cs ⁺ ), 75 mg Ca ²⁺ , 5 mg Rb ⁺ , 5 mg Cr ³⁺ , 3 mg Pb ²⁺ , 1 mg Ba ²⁺ , 1 mg Zn ²⁺ , 0.5 mg Mg ²⁺ and 0.5 mg Hg . The pH of the two solutions was then adjusted to 0.5 or 12.3 by adding additional 0.32 M HN0 ₃ or 0.02 M NaOH into the solutions, respectively.

From Table 3, it can be seen that Cs ⁺ ions can be efficiently removed by as high as 90.03% in the artificial water where the molar ratio of [Na ⁺ + K ⁺ + Mg ²⁺ + Ca ²⁺ ]/[host l]/[Cs ⁺ ] is equal to 4.6 x 10 ⁴ : 15.8: 1. With a decreasing concentration of Cs ⁺ from 2.02 ppm down to 47.95 ppb, Cs ⁺ removal efficiency gets stabilized around 90% in the presence of 80-fold excess of host 1 but 1.8 million- fold excess of combined inorganic ions including Na ⁺ , K ⁺ , Mg ²⁺ , and

From Table 4, it can be seen that Cs ⁺ ions can be efficiently removed by about 46% in the artificial nuclear waste where the molar ratio of [Na ⁺ + K ⁺ ]/[host l]/[Cs ⁺ ] is equal to 43.15 x 10 ⁵ : 16.8: 1 in the presence of many other di- and tri-valent cations at either highly acidic or alkaline solutions.

Table 3. Extraction efficiencies (%) of Cs* ions from artificial sea water by macrocyclic host 1 at different concentrations as determined by inductively coupled plasma mass spectrometry (ICP).

Host 1 Cs* Cs ⁺ Sorption by 1 Host l Cs* Cs* Sorption bv 1

(μΜ) (ppm) (%) (μΜ) (ppb) (%)

240 2.01 90.03 30 49.28 89.57

" The concentration of CsNOs is around 2 ppm and 50 ppb, respectively, and that of host 1 ranges is 240 or 30 μΜ with a [host]:[Cs ⁺ ] molar ratio of 16:1 and 80:1, respectively. Extractions were carried out in a biphasic system using equal volumes of ¾θ containing Cs ^* ions and CHCb containing organic host 1 for 24 h at pH 7.6 at 25 "C. Table 4. Extraction efficiencies (%) of Cs ^* ions from artificial nuclear waste by macrocyclic host 1 at 240 uM as determined by inductively coupled plasma mass spectrometry (ICP). ³

Host l Cs ⁺ s ⁺ Sorption by 1 V Cs ⁺ Sorption by 1

(μΜ) (ppm) (°% pH = 0.5) (ppm) (V pH = 12.3)

240 1.90 45.50 1.96 45.85

" The concentration of CsNO¾ is around 2 ppm and that of host 1 ranges is 240 μΜ with a [host]:[Cs*] molar ratio of 16.8: 1. Extractions were carried out in a biphasic system using equal volumes of ¾0 containing Cs" ions and CHCI3 containing organic host 1 for 24 h at pH 0.5 or 12.3 at 25 °C.

In conclusion, the macrocyclic aromatic pentamers such as 1 described herein possess a cavity decorated by five convergently aligned electron-rich carbonyl oxygen atoms that are capable of highly selective high-affinity recognition of cesium ions under acidic, neutral or alkaline conditions. Accordingly, compounds with a general Formula I as exemplified by host (or pentamer) 1 can efficiently lower the concentration of cesium ions by >99% at a ligand/Cs ⁺ molar ratio of 4: 1 in pure water, (2) remove -90% Cs ⁺ ions ppb from the simulated sea water solution containing 0.48 M NaCl, 0.06 M Na S0 ₄ , 0.02 M C1, 0.06 M MgCl ₂ and 0.02 M Ca(N0 ₃ ) ₂ at pH 7.6 (the combined concentration of Na ⁺ and K ⁺ , Mg ²⁺ and Ca ²⁺ is up to 1.8 million times that of Cs ⁺ ions in the same solution) and (3) remove ~46% of Cs ⁺ ions at 2 ppm from the simulated highly acidic or alkaline nuclear waste solutions in the presence of many other competitive ions including 4 M Na ⁺ , 0.5 M ⁺ , 75 ppm Ca ²⁺ , 5 ppm Rb , 5 ppm Cr , 3 ppm Pb , 1 ppm Ba , 1 ppm Zn , 0.5 ppm Mg and 0.5 ppm Hg (the combined concentration of Na ⁺ and ⁺ alone is 0.3 million times that of Cs ⁺ ions in the same solution. The compound of Formula I described herein clearly demonstrates a superior performance in sorption capacity and insensitivity to wide ranging pHs and good tolerance of high salinity with respect to the organic extractants or composite materials ever developed. COLUMN FILTRATION SYSTEM A column filtration system as shown in Fig. 1 was used in the following examples to be described.

In one example, 2 mg of the compound of Formula I was conjugated onto 3 g of zeolite. The conjugation procedure involves dissolving 2 mg of the compound in 5 mL dichloromethane, followed by adding 3g of zeolite to dichloromethane. The dichloromethane was then slowly removed under vacuum to allow the compound to precipitate out and distributed as evenly as on the surface of zeolite. A synthetic mineral water was prepared to contain 10 ppb of Cs ⁺ , 100 ppm of Na ⁺ , 10 ppm of K ⁺ , 60 ppm of Ca ²⁺ , 25 ppm of Mg ²⁺ at a pH of 7.4. This mineral water was then passed through a glass column containing 3.002 g of compound-conjugated zeolite at a flow rate of 0.17 ml/minute. It was found that 10% and 20% breakthroughs of Cs ⁺ ions, corresponding to the points where the concentration of Cs ⁺ ions in the eluted solution is 9 and 8 ppb respectively, were reached after passing 1.7 and 2.6 liters of the synthetic mineral water, respectively. This highlights a high capacity of the compound of Formula I in selectively removing Cs ⁺ ions in the presence of other competing metal ions including Na ⁺ , +, Ca ²⁺ and Mg ²⁺ ions.

In one example where synthetic mineral water solution containing 10 ppb Cs ⁺ , 100 ppm of Na ⁺ , 10 ppm of K ⁺ , 60 ppm of Ca ²⁺ , 25 ppm of Mg ²⁺ at a pH of 7.4 was used, 10 mg of the compound of Formula I was conjugated onto 3 g of zeolite. It was found that 10% breakthrough of Cs ⁺ ions, corresponding to the point where the concentration of Cs ⁺ ions in the eluted solution is 9 ppb, was reached after passing 3.0 liters of the synthetic mineral water.

In one example where artificial sea water solution containing 2 ppm Cs ⁺ , 0.48 M NaCl, 0.06 M Na ₂ S0 ₄ , 0.02 M KCl, 0.06 M MgCl ₂ and 0.02 M Ca(N0 ₃ ) ₂ at pH 7.6 was used, 0.15 g of the compound of Formula I was conjugated onto 2.85 g of zeolite. It was found that 10% and 20% breakthroughs of Cs ⁺ ions, corresponding to the points where the concentration of Cs ⁺ ions in the eluted solution is 0.2 and 0.4 ppm, respectively, were reached after passing 572 and 995 mL of the artificial sea water.

In one example where artificial sea water solution containing 2 ppt Cs ⁺ , 0.48 M NaCl, 0.06 M Na ₂ S0 ₄ , 0.02 M KCl, 0.06 M MgCl ₂ and 0.02 M Ca(N0 ₃ ) ₂ at pH 7.6 was used, 0.15 g of the compound of Formula I was conjugated onto 2.85 g of zeolite. It was found that 10% and 20% breakthroughs of Cs ⁺ ions, corresponding to the points where the concentration of Cs ⁺ ions in the eluted solution is 0.2 and 0.4 ppt, respectively, were reached after passing 322 and 402 mL of the artificial sea water.

By "comprising" it is meant including, but not limited to, whatever follows the word "comprising". Thus, use of the term "comprising" indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present.

By "consisting of is meant including, and limited to, whatever follows the phrase "consisting of. Thus, the phrase "consisting of indicates that the listed elements are required or mandatory, and that no other elements may be present.

The inventions illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms "comprising", "including", "containing", etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the inventions embodied therein herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention.

By "about" in relation to a given numerical value, such as for temperature and period of time, it is meant to include numerical values within 10% of the specified value.

The invention has been described broadly and generically herein. Each of the narrower species and sub-generic groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Other embodiments are within the following claims and non- limiting examples. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group. References

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