US20200261885A1

US20200261885A1 - New composites for extraction of metal or contaminating chemical species

Info

Publication number: US20200261885A1
Application number: US16/639,839
Authority: US
Inventors: Wendy Lee QUEEN; Daniel Teav SUN
Original assignee: Ecole Polytechnique Federale de Lausanne EPFL
Current assignee: Ecole Polytechnique Federale de Lausanne EPFL
Priority date: 2017-08-21
Filing date: 2018-08-17
Publication date: 2020-08-20
Also published as: US11857945B2; EP3672721A1; WO2019038645A1; US20220168706A1; EP3672721B1

Abstract

Disclosed is a composite for extracting one or more metal or contaminating chemical species from an aerial or aqueous medium by selective binding, the composite including at least one porous template functionalized by at least one polymer, the polymer including one of the folowing chemical functions: primary, secondary or tertiary amine, amide, nitrile, pyridine, pyrole, thiol, thiolether, thiophene, thiadiazole, alcohol/hydroxyl, phenol, catechol, pyragalol, carboxylic acid, aldehyde, ester, acyl, crown ether, phosphate, phosphoryl, epoxide, halogen, haloalkane.

Description

BACKGROUND OF THE INVENTION

The invention concerns new composites for extracting metals, typically precious metals, and other contaminating chemical species from aerial or aqueous environments, preferably from aqueous mediums such as the oceans, rivers, or waste streams produced by various industries such as the electronics, electroplating, and pharmaceuticals industry.
Industry uses a number of processes that require the use of a variety of different metals, many of which are discharged into aqueous environments. In many cases, these metals (i.e. mercury (Hg) or lead (Pb)) can have toxic effects on the body and environment making it important to extract them from water to inhibit human exposure.
Other metals, particularly those with very low natural abundance, have high economic value, (i.e. gold (Au), silver (Ag), platinum (Pt), and palladium (Pd)) making extraction imperative for recycling purposes. Precious metals are used in a variety of applications that include manufacturing of fine jewelry, electroplating, electronics, pharmaceuticals, and much more.
Many methods, including chemical precipitation, chemical coagulation, electrochemical technologies, ion exchange, and membrane technologies, can be used to extract metals from the wastewater that results from industrial activities. However, these methods suffer from many disadvantages including the need for large quantities of chemical additives forming by-product sludges, high energy usage, high cost and their poor efficiency at very low metal concentrations.
Resins such as Smopex® or Superlig® are quite expensive. Moreover, overtime, large organic molecules such as humic acid typically clog the pores of large pore resins. Often, selectivity to other ions, such as Ca and Mg, is a big problem associated to these ion-exchange resins.
Sustainable metal recovery technologies are mentioned in the publication «recovery of precious metals through biosorption—A review». Hydrometallurgy, 2010, 103, 2236. Compared with the previously listed conventional methods, biosorption-based processes disclosed in this publication offer a number of advantages including low operating costs, minimization of the volume of chemical and high efficiency in detoxifying effluents, but these methods also have many disadvantages. Indeed, the use of freely suspended microbial biomass has disadvantages that include small particle size, low mechanical strength and difficulty in separating the biomass and eflluent. Moreover, since biosorption is determined by equilibrium, it is largely influenced by pH, by the concentration of biomass and by the interactions between different metallic ions. The biosorption process mechanism is thus complex.
Chemical species different from metals, for example volatile organic compounds (VOCs), may also need to be extracted from their environment which could be an aerial or an aqueous medium.
The object of the present invention is to provide compounds for extracting one or more metal or contaminating chemical species from its environment that overcomes, at least in part, the aforementioned disadvantages.
The present invention typically concerns the extraction of such species from both aerial and aqueous environments, preferably from aqueous environments.
In particular, the ability to remediate to low concentrations of a desired chemical specie in the presence of high concentrations of undesirable chemical species coupled with high removal capacity and fast removal rate are important properties required for materials to be applicable in chemical separations.
Limiting the cost of these compounds is also an objective of the present invention.
The ultimate goal aimed at developing materials that can be precisely designed with varying surface functionality, for the extraction of specific metal or contaminating chemical species from different predefined sources including aerial and aqueous mediums, and typically aqueous mediums including wastewaster mixtures resulting from various industries.

General Description

For this purpose, the invention proposes a composite for extracting one or more metal or contaminating chemical species from an aerial or aqueous medium by selective binding, said composite comprising at least one porous template functionalized by at least one polymer, said polymer comprising one of the following chemical functions: primary, secondary or tertiary amine, amide, nitrile, pyridine, pyrrole, thiol, thiolether, thiophene, thiadiazole, alcohol/hydroxyl, phenol, catechol, pyragallol, carboxylic acid, aldehyde, ester, acyl, crown ether, phosphate, phosphoryl, epoxide, halogen and haloalkane. Preferably, said medium is an aqueous medium.
Advantageously, said at least one polymer is chosen among redox active polymers, peptides, biopolymer including polypeptides and polysaccharides, epoxy based polymer, fluoropolymer, acrylics, dedrimers, rubbers, inorganic polymers and organic polymers. Preferably, said at least one polymer is a redox active polymer.
In the context of this invention, a “redox active polymer” is defined as a polymer that can undergo electron transfer reactions with other chemical species. Redox polymers contain electrostatically and spatially localized redox sites which can be oxidized or reduced, and the electrons are transported by an electron exchange reaction (electron hopping) between neighboring redox sites if the segmental motions enable this. Redox polymers can be divided into several subclasses:

- Polymers that contain covalently attached redox sites, either built into the chain, or as pendant groups; the redox centers are mostly organic or organometallic molecules; and
- Ion exchange polymeric systems (polyelectrolytes) where the redox active ions (mostly complex compounds) are held by electrostatic binding.

In the present invention, redox active polymers are preferably chosen among the followings: Poly(Tetracyanoquinodimethane) (PTCNQ), Poly(Viologens) Poly(Tetrathiafulvalene) (PTTF), Quinone Polymers, Polyhydroquinone (PHQ), Polydopamine (PDA), Polytyramine (PTA), Poly-para-phenylediamine (PpPDA), Poly(Vinylferrocene) (PVF or PVFc) (Organometallic Redox Polymer), Perfluorinated Sulfonic Acids (Nafion®), Poly(Styrene Sulfonate) (PSS), Poly(4-vinylpyridine) (PVP, QPVP), Polyaniline (PANI) and PANI Derivatives, Poly(1-aminoanthracene), Poly(o-toluidine), Poly(1,8-diaminonaphthalene) (PDAN), Poly(aniline-co-N-propanesulfonic acid-aniline), Poly(Diphenylamine) (PDPA), Poly(2-Am inodiphenylam ine) (P2ADPA), Poly(o-Phenylenediamine) (PPDA), Poly(o-Aminophenol) (POAP), Polyluminol (PL), Polypyrrole (PP) and PP Derivatives, Polyindole and Derivatives, Polymelatonin (PM), Polyindoline, Polycarbazoles (PCz), Polythiophene (PT) and PT Derivatives, Polyazines, Poly(1-Hydroxyphenazine) (PPhOH), Poly(Acridine Red) (PAR), Poly(Phenosafranin) (PPhS), Polyflavin (PFI), Poly(New Fuchsin) (PnF), Polyfluorene (PF), Poly(9-Fluorenone) (PFO), Poly (9,10-Dihydrophenanthrene), Poly(p-Phenylene) (PPP), Poly(Phenylenevinylene) (PPPV), Polytriphenylamine (PTPA), Poly(4-Vinyl-Triphenylamine) (PVTPA), Polyrhodanine (PRh), Poly (Eriochrome Black T), Poly(5-Amino-1,4-Naphthoquinone) (PANQ), Poly(5-Amino-1-Naphthol), Poly(4-Ferrocenylmethylidene-4H-Cyclopenta-[2,1-b;3,4-b⁰]-Dithiophene), Fullerene-Functionalized Poly(Terthiophenes) (PTTh-BB), Poly[Iron(4-(2-Pyrrol-1-Ylethyl)-4⁰-Methyl-2,2⁰-Bipyridine)₃ ²⁺], Polypyrrole Functionalized by Ru(bpy)(CO)₂, Poly(Tetra-Substituted Porphyrins), Poly(Tetra- Substituted Phtalocyanines),) Poly[4,4⁰(5⁰-Bis(3,4-Ethylenedioxy)Thien-2-Yl] Tetrathiafulvalene (PEDOT-TTF), Poly {3-[7-Oxa-8-(4-Tetrathiafulvalenyl) Octyl]-2,2⁰-Bithiophene} (PT-TTF), Poly(Aniline-co-Diaminodiphenyl Sulfone), Poly(Aniline-co-2/3-Amino or 2,5-Diamino Benzenesulfonic Acid), Poly(Aniline-co-o-Aminophenol), Poly(m-Toluidine-co-o-Phenylenediamine), Poly (Luminol-Aniline), polymer of 2,5-dihydroxy-1,4-benzenediacetic acid (PDHAA), poly-para-phenylenediamine (PpPDA), and polyhydroquinone (PHQ), preferably among polydopamine (PDA), poly-para-phenylenediamine (PpPDA), polyhydroquinone (PHQ), polymer of 1,4-benzenedithiol (PBDT), polytyramine (PTA) or polymer of 2,5-dihydroxy-1,4-benzenediacetic acid (PDHAA).
Hereunder are the semi-developed formulas of some of the previously cited polymers:

- Polymer of 1,4-benzenedithiol (PBDT):

PBDT is a polymer comprising several monomers of 1,4-benzenedithiol.

- polyhydroquinone (PHQ):

PHQ is a polymer comprising several monomers of hydroquinone.

- Poly-para-phenylenediamine (PpPDA):

PpPDA is a polymer comprising several monomers of para-phenylenediamine.

- polytyramine (PTA):

PTA is a polymer comprising several monomers of tyramine.

- polydopamine (PDA):

PDA is a polymer comprising several monomers of dopamine.
Preferably, the porous template according to the invention includes at least a metal, for example Fe or Cu.
A porous template comprising at least a metal has the advantage to drive polymerization and to attach to the polymer allowing easy separation from the solution.
The applicants have shown that the metal can help drive the polymerization process. Once the monomer is in contact with the porous template comprising metal, it interacts with the metal, which behaves like a catalyst to form the polymer. Because of this process, most of the formed polymer is located inside the porous template rather than on the surface outside. With the polymer trapped inside and/or attached to the metal inside, it cannot leave the porous template. As a polymer is quite hydrophilic, if it came out of the porous template, it would potentially disperse in the water. As such, the polymer by itself is more difficult to separate from water than the composite comprising both the porous template and the polymer. Therefore, using a porous template comprising at least one metal is advantageous because with such a template the polymer does not disperse in water, making it easy to separate after extraction of the metal or contaminating chemical specie of interest.
Although a porous template comprising at least one metal is preferred for the reasons discussed above, a porous template not including metal can also be used in the present invention. In that case, it would be necessary to adapt the process of polymerization by common techniques.
Preferably, the at least one porous template is chosen among a metal-organic framework, a zeolite, carbons, a silica, an aerogel, a covalent organic framework, a porous polymer network, a porous molecular solid, an hydrogel, a porous boron nitride, a porous graphene and a porous graphene oxide, more preferably among a metal-organic framework, a zeolite, carbons, a silica, an aerogel, a covalent organic framework, a porous polymer network, a porous molecular solid and an hydrogel.
Even more preferably, said at least one porous template is a metal organic framework (MOF).
Metal organic frameworks (MOFs) are a relatively new class of microporous materials constructed by metal-ions or metal-ions clusters interlinked by organic ligands. Their high internal surface area makes them an ideal candidate for uptake of ions.
In the context of the invention, preferred MOFs are chosen among Fe-BTC, Cu-BTC, Cu-TDPAT and Al-BDC-NH₂, preferably among Fe-BTC and Cu-BTC.
As mentioned before, the invention aims at extracting one or more specific metal or contaminating chemical species from an aerial or aqueous medium.
Said one or more metal or contaminating chemical species is typically chosen among: palladium, platinum, ruthenium, iridium, gold, silver, rhodium, cadmium, chromium, lead, mercury, arsenic, barium, fluoride, nitrates, nitrites, radium, selenium, sodium, radioactive (U, Th, Ra, Cs), lithium, magnesium, indium, gallium, germanium, tellurium, bismuth, rhenium, niobium, molybdenum, osmium, lanthanides, iron, cobalt, nickel, copper, zinc, ozone, chlorine gas, ammonia, hormones, dyes, volatile organic compounds, perchlorate and hydrocarbons (oil). Preferably, said one or more metal or contaminating chemical species is chosen among palladium, platinum, ruthenium, iridium, gold, silver, rhodium, cadmium, chromium, lead, mercury, arsenic, iron, cobalt, nickel and copper, even more preferably among precious metals such as palladium, platinum, ruthenium, iridium, gold, silver and rhodium.
The composite according to the invention is highly porous with a high density of designable functional groups resulting in high selectivity for the metal or contaminating chemical specie of interest.
The mechanism of action of the composite according to the invention depends on the target chemical specie to extract.
In some cases, the composite acts by reducing the chemical specie of interest. It is the case for example for the Hg, Au, Ag or Pd species in solution and it is also probably the case of toxic chlorine gas or ozone from air.
In some cases, the reduction leads to a solid compound. For example, Au³⁺ is reduced in Au⁰(s) and thus precipitates into a solid material, which facilitates its extraction.
Hexavalent chromium ions Cr⁶⁺ that are very toxic can be reduced into Cr³⁺ species by the composite according to the invention. It does not always precipitate but it is still very advantageous as Cr³⁺ is 500 to 1000 times less toxic than Cr⁶⁺.
Some other chemical species like Pb are more probably extracted, typically from water, by other mechanisms, like selective adsorption.
The composite according to the invention is also easily recyclable with mild cheap additives like ascorbic acid or ethylenediaminetetraacetic acid (EDTA).
Once the compound of interest is transformed or captured by the composite according to the invention, several means can be used for its extraction from the medium and then from the composite.
In the case of gold, which is in solid form with the composite, it is possible to use the composite over and over until you want to separate the gold. At this time, it would be possible to simply heat, for example around 900° C., and adjust the pH to very acidic values, typically values below 3, to destroy the porous template and polymer in order to recover the gold. The destruction of the porous template have minimal economic impact considering its low cost.
Another option is to use the composite, once it reaches maximal capacity for the target chemical specie (typically precious metal), as a catalyst.
Another option, for example in the case of gold extraction from water, is to use a sturdy porous template, typically a porous carbon, which can resist the chemical conditions needed to oxidize the gold back to the 3⁺ oxidation state to be washed out of the composites.
The composite according to the invention is highly competitive with regard to capacity, removal rate, facile synthetic conditions and selectivity compared to the current state of the art. It operates well at room temperature requiring no energy input to heat the solutions to drive the reduction process.
Other details and advantages of the present application will become more fully apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the architecture of the porous template Fe-BTC and the polymerization of the monomer dopamine into polydopamine in this porous template.

FIG. 2 is a schematic representation of a metal organic framework (MOF) and the polymerization of a monomer inside its pores.

FIG. 3a shows the result of evolution of the Pb concentration over a period of an hour after introduction of FeBTC or Fe-BTC/PDA in a 1 ppm Pb²⁺ aqueous solution.

FIG. 3b is a graph showing the evolution of lead concentration in a 0.9 ppm Pb²⁺ aqueous solution after introduction of Fe-BTC or Fe-BTC/PDA for 24 hours.

FIG. 3c shows lead removal capacity vs cycle number.

FIG. 4a shows the evolution of the mercury concentration after introduction of Fe-BTC or Fe-BTC/PDA composite in a 1 ppm Hg²⁺ solution over a period of an hour.

FIG. 4b is a graph showing the evolution of Hg concentration in a 0.9 ppm Hg²⁺ solution after introduction of Fe-BTC or Fe-BTC/PDA for 24 hours.

FIG. 4c shows mercury removal capacity vs cycle number.

FIG. 5a shows removal capacity of Fe-BTC or Fe-BTC/PDA in river water spiked with varying concentrations of Hg²⁺.

FIG. 5b present the results of X-ray photoelectron spectroscopy (XPS) of of Fe-BTC/PDA soaked in a 1000 ppm solution of HgCl₂for 24 hours.

FIG. 5c shows the results of powder X-ray diffraction pattern (PXRD) of Fe-BTC/PDA after being soaked in 1000 ppm solution of HgCl₂for 24 hours.

FIG. 6a shows the results of high resolution X-ray photoelectron spectroscopy (XPS) of Fe-BTC/PDA after treating an aqueous medium comprising Cr⁶⁺.

FIG. 6b shows Cr⁶⁺ removal capacity (Qe) plotted against the equilibrium concentration.

FIGS. 7, 8, 9 and 10 respectively show the results of powder X-ray diffraction patterns, nitrogen adsorption isotherms at 77K, total reflectance infrared spectroscopy and scanning electron microscopy of the porous template Fe-BTC after reaction with 1,4-benzenedithiol (leading to polymerized 1,4-benzenedithiol—PBDT), hydroquinone (leading to polymerized hydroquinone—PHQ), para-phenylenediamine (leading to poly-para-phenylenediamine—PpPDA), tyramine (leading to polytyramine—PTA) or dopamine (leading to polydopamine—PDA).

FIG. 11a powder X-ray diffraction patterns of Fe-BTC/PTA and Fe-BTC/PDA after being soaked in an aqueous solution containing Au³⁺.

FIG. 11b microscope image of an aqueous solution containing Au³⁺ after reaction with Fe-BTC/PDA.

FIGS. 12a and 12b are bar graphs illustrating the evolution of gold concentration in a water solution comprising respectively 1 ppb Au³⁺ and in a 90 ppm Au³⁺ before and after being in presence of Fe-BTC or composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT for 24 hours.

FIGS. 13a and 13b are bar graphs illustrating the evolution of palladium concentration in a water solution comprising respectively 550 ppb Pd²⁺ and 55 ppm Pd²⁺ before and after being in presence of Fe-BTC or composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT for 24 hours.

FIGS. 14a and 14b are bar graphs illustrating the evolution of silver concentration in a water solution comprising respectively 718 ppb Ag⁺ and 90.5 ppm Ag⁺ before and after being in presence of Fe-BTC or composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT for 24 hours.

FIGS. 15a and 15b show respectively the evolution of Au³⁺ concentration in a 1 ppm Au³⁺ aqueous solution from the Rhone river before and after treatment with Fe-BTC/PTA for 24 hours and the gold removal rate associated to this reaction.

FIG. 16a illustrates the evolution of Au concentration in a 1 ppm Au³⁺ aqueous solution comprising roughly 200000 ppb of Cu and Ni before and after treatment with Fe-BTC/PTA for 24 hours. FIG. 16b illustrates the evolution of Au concentration in a roughly 200000 ppb Au³⁺ aqueous solution comprising roughly 200000 ppb concentration of Cu and Ni before and after treatment with Fe-BTC/PTA for 24 hours. FIG. 16c illustrates the evolution of Cu and Ni concentration in a roughly 200000 ppb Au³⁺ aqueous solution comprising roughly 200000 ppb concentration of Cu and Ni before and after treatment with Fe-BTC/PTA.

FIGS. 17a and 17b show the evolution of Cu, Ni, Ca, Mg, K, Na and Au concentration in a simulated e-waste solution before and after a 24 hours treatment with Fe-BTC/PpPDA.

FIG. 17c illustrates the gold extraction speed of Fe-BTC and Fe-BTC/PpPDA in a simulated e-waste solution identical to that studied in FIGS. 17a and 17 b.

FIG. 17d shows the percent removal of gold in a simulated e-waste solution identical to that studied in FIGS. 17a and 17b at different pH after a 24 hours treatment with Fe-BTC/PpPDA.

FIG. 17e shows the percent removal of gold by Fe-BTC/PpPDA after multiple exposures and regenerations using ascorbic acid in samples of a simulated e-waste solution identical to that studied in FIGS. 17a and 17 b.

FIG. 18a shows the percent removal of gold from an electronic waste leaching solution after a thirty minutes treatment with Fe-BTC/PpPDA.

FIGS. 18b and 18c show the rate of gold removal from several matrices including the electronic waste leaching solution of FIG. 18a (with an initial gold concentration of 7.3 ppm), wastewater (with an initial gold concentration of 3.7 ppb), river water (with an initial gold concentration of around 120 ppb), sea water (with an initial gold concentration of 1 ppm), and of a solution obtained by treating incinerated sewage with NBS/Py (with an initial gold concentration of 5.47 ppm).

FIGS. 18d and 18e show the evolution of Ca, Cs, Mg, Na, Fe, Cu, K, B, Zn, Rb and Au concentration in a solution obtained by treating incinerated sewage with NBS/Py identical to that studied in FIGS. 18b and 18c , before and after a 24 hours treatment with Fe-BTC/PpPDA.

FIG. 19 shows CO₂adsorption isotherms at 25° C. for Fe-BTC and Fe-BTC/PpP DA.

FIG. 20a shows the concentration of Na, Mg, Ca and Sr in a Rhone river water sample.

FIG. 20b shows the concentration of lead in the Rhone River water sample of FIG. 20a after treatment with Fe-BTC or with composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT.

FIG. 21a shows the concentration of B, Na, K, Mg, Ca and Sr in a Mediterranean Sea water sample.

FIG. 21b shows the concentration of lead in the Mediterranean Sea water of FIG. 21a after treatment with Fe-BTC or with composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT.

FIG. 22 shows powder X-ray diffraction patterns of the porous template HKUST-1 (also known as Cu-BTC). The template was soaked in para-Phenylenediamine (pPDA) leading to polymerized poly-para-phenylenediamine (PpPDA). Cu-BTC and Cu-BTC/PpPDA were soaked in water for 7 days.

FIG. 23 shows CO₂adsorption isotherms at 25° C. for Cu-BTC and Cu-BTC/PpP DA.

FIGS. 24a and 24b show scanning electron microscopy of the porous template Cu-BTC and FIG. 24c shows scanning electron microscopy of the same Cu-BTC/PpPDA. Scale bars in FIGS. 24a, 24b and 24c all correspond to 1000 nm.

DETAILED DESCRIPTION

The applicants have started to design components for mercury remediation in order to produce clean potable water.
In this work, the applicants have synthesized a cheap environmentally and biologically friendly iron base porous metal-organic framework (MOF), known as Fe-BTC, as shown in FIG. 1 (detailed process of synthesis at the end of the patent application).
The MOFs unique framework architecture allows metal ions to diffuse through while inhibiting large organic molecules (like humic acid) from entering.
The Fe-BTC MOF acts as a porous template that catalyzes the in-situ polymerization of a variety of small molecules.
For example, the applicants have found that the Fe³⁺ sites of Fe-BTC distributed throughout the framework facilitates the polymerization of the monomer dopamine, to its polymer polydopamine (PDA) and adheres the polymer to the pore surface.
During this process PDA is pinned to the internal surface of the pores via attachment to the open metal sites introducing extrinsic porosity to an intrinsically non-porous polymer as illustrated in FIG. 2. The result is a highly porous composite. The activity of this porous composite has been studied by the applicants.
Firstly, the applicants studied the rate of mercury removal (FIG. 4a ). In order to do that, a solution of Hg²⁺ has been treated with Fe-BTC/PDA or Fe-BTC over a period of an hour. For each experiment, 20 mL of Millipore water containing 1 ppm of Hg²⁺ were treated with 20 mg of Fe-BTC or 20 mg of Fe-BTC/PDA.
Secondly, the applicants studied the mercury removal capacity at low Hg²⁺ concentrations (FIG. 4b ). To study this, Fe-BTC or Fe-BTC/PDA were soaked in Millipore water spiked with mercury for 24 hours. For the experiment ˜10 mg of Fe-BTC or ˜10 mg Fe-BTC-PDA were added to 20 mL of a 0.9 ppm solution of Hg²⁺.
The results of these experiments show that Fe-BTC/PDA is a highly porous composite that fosters the rapid, selective removal of Hg²⁺ from water samples containing high concentrations of Hg²⁺. Indeed, the composite component Fe-BTC/PDA binds up to 1634 mg Hg²⁺ per gram of composite, and removes over 99% of these ions from a 1 ppm solution to yield drinkable levels in less than a minute.
FIG. 5a shows that Fe-BTC/PDA is efficient at different initial Hg concentrations. For each experiment, ˜10 mg of Fe-BTC or ˜10 mg Fe-BTC/PDA were added to 20 mL of Rhone river water containing various amounts of Hg²⁺.
The results of the experiments shown in FIGS. 5b and 5c , clearly indicates that the high removal capacity for Hg from water is achieved via reduction of Hg²⁺ to Hg¹⁺.
In FIG. 5b , 10 mg Fe-BTC/PDA was soaked in 20 mL of 1000 ppm solution of HgCl₂for 24 hours. The XPS was used to elucidate the electronic structure of the heavy metal. Two signature peaks fitting the data for HgCl₂and Hg₂Cl₂or HgO were observed. This data confirms that the polymer is reducing the Hg²⁺ to Hg¹⁺.
For the experiment presented in FIG. 5c , 10 mg Fe-BTC/PDA was soaked in 20 mL of 1000 ppm solution of HgCl₂for 24 hours. After treating a solution of Hg²⁺ with Fe-BTC/PDA the mercury precipitates as solid Hg₂Cl₂, evident by PXRD. This data also confirms that the polymer is reducing the Hg²⁺ to Hg¹⁺.
Hereunder is the proposed mechanism of the Fe-BTC/PDA composites' enhanced properties for Hg²⁺ remediation from water.
Through a reduction mechanism the Fe-BTC/PDA composite is able to remediate large quantites of mercury.
The material Fe-BTC/PDA has also proven to be easily regenerated and cycleable after reduction of mercury as shown in FIG. 4c . For this experiment, 0.500 g of Fe-BTC/PDA was added to a 1 L solution of Milipore water spiked with 1000 ppm of Hg²⁺. The remaining Hg²⁺ concentration in the aqueous media were analyzed to determine the mercury capacity (Q_e, mg/g). The Fe-BTC/PDA samples was then added to 0.001 M solutions of ascorbic acid. The samples were filtered, washed with methanol, dried and weighed. The regenerated materials were then added to 1000 ppm solutions of Hg²⁺ again. This procedure was repeated three more times to obtain the capacity Q_e(mg/g) for each of the four cycles.
Previously described performance results are also maintained using real-world water samples from the Rhone River (which contains other metal ions and organics) and water samples spiked with large amounts of humic acid, illustrating the uptake selectivity of Fe-BTC/PDA. Thus, this material is an excellent, inexpensive candidate for in-home and industrial water treatment.
The applicants have discovered the impact of the MOF Fe-BTC on the polymerization of the monomer dopamine to polydopamine (PDA).
They have discovered that the polymer, PDA undergoes redox chemistry that fosters the extraordinary heavy metal remediation properties of Fe-BTC/PDA with Hg²⁺.
After these experiments the applicants have tried to apply this composite to other metals with a high reduction potential starting with toxic heaxavalent chromium Cr⁶⁺.For each experiment associated to FIG. 6b , ˜10 mg of Fe-BTC or ˜10 mg Fe-BTC-PDA were added to 20 mL of river water containing various amounts of Cr⁶⁺. Results of this experiment show that Fe-BTC/PDA sees a 7-fold increasing in removal capacity compared to Fe-BTC alone.
For high resolution-XPS experiment of FIG. 6a , 10 mg Fe-BTC/PDA was soaked in 20 mL of 300 ppm solution of Cr⁶⁺ for 24 hours. Two signature peaks fitting the data for Cr³⁺ and Cr⁶⁺ species were observed. The data implies that the increase in removal capacity for Fe-BTC/PDA compared to Fe-BTC is the result of the redox active polymer reducing Cr⁶⁺ to Cr³⁺.
Hereunder is the proposed mechanism of the Fe-BTC/PDA enhanced properties for Cr⁶⁺ remediation from water.
Through a reduction mechanism Fe-BTC/PDA component is able to remediate large quantites of hexavalent chromium. This result is very interesting as Cr³⁺ is 500 to 1000 times less toxic than Cr⁶⁺ hexavalent chromium.
Previously presented results led the applicants to begin to design a variety of new redox activate MOF/polymer composites with the hope of creating high selectivity in order to design materials for specific analytes.
Indeed, since it was possible to remove over 99% of Hg from aqueous medium comprising Hg²⁺ by a reduction reaction with Fe-BTC/PDA and since the standard reduction potentials of precious metals are comparable to Hg²⁺ reduction potential, as shown in table 1 hereafter, it may be possible to recover other precious metals from water. It is to be noted that the standard reduction potential of Cr⁶⁺/Cr³⁺ is of about 1.36 as shown in table 1 hereunder.

TABLE 1

standard reduction potentials E° of various compounds (V)

	Half-Reaction	E^° (Volts)

	Li⁺ + e⁻ → Li	−3.040
	K⁺ + e⁻ → K	−2.942
	Rb⁺ + e⁻ → Rb	−2.942
	Cs⁺ + e⁻ → Cs	−2.923
	Ba²⁺ + 2e⁻ → Ba	−2.92
	Sr²⁺ + 2e⁻ → Sr	−2.89
	Ca²⁺ + 2e⁻ → Ca	−2.84
	Na⁺ + e⁻ → Na	−2.713
	La³⁺ + 3e⁻ → La	−2.37
	Mg²⁺ + 2e⁻ → Mg	−2.356
	Ce³⁺ + 3e⁻ → Ce	−2.34
	Nd³⁺ + 3e⁻ → Nd	−2.32
	H₂+ 2e⁻ → 2H⁻	−2.25
	Sc³⁺ + 3e⁻ → Sc	−2.03
	Be²⁺ + 2e⁻ → Be	−1.97
	Al³⁺ + 3e⁻ → Al	−1.676
	U³⁺ + 3e⁻ → U	−1.66
	Ti²⁺ + 2e⁻ → Ti	−1.63
	Hf⁴⁺ + 4e⁻ → Hf	−1.56
	No³⁺ + 3e⁻ → No	−1.2
	Mn²⁺ + 2e⁻ → Mn	−1.18
	Cr²⁺ + 2e⁻ → Cr	−0.90
	2H₂O + 2e⁻ → H₂+ 2OH⁻	−0.828
	Zn²⁺ + 2e⁻ → Zn	−0.7626
	Cr³⁺ + 3e⁻ → Cr	−0.74
	Ga³⁺ + 3e⁻ → Ga	−0.529
	U⁴⁺ + e⁻ → U³⁺	−0.52
	2CO₂+ 2H⁺ + 2e⁻ → H₂C₂O₄	−0.475
	S + 2e⁻ → S²⁻	−0.447
	Fe²⁺ + 2e⁻ → Fe	−0.44
	Cr³⁺ + e⁻ → Cr²⁺	−0.424
	2H₂O + 2e⁻ → H₂+ 2OH⁻ (10⁻⁷M)	−0.414
	Cd²⁺ + 2e⁻ → Cd	−0.4025
	Ti³⁺ + e⁻ → Ti²⁺	−0.37
	PbI₂+ 2e⁻ → Pb + 2I⁻	−0.365
	PbSO₄+ 2e⁻ →Pb + SO₄	−0.3505
	In³⁺ + 3e⁻ → In	−0.3382
	Tl⁺ + e⁻ → Tl	−0.3363
	Co²⁺ + 2e⁻ → Co	−0.277
	H₃PO₄+ 2H⁺ + 2e⁻ → H₃PO₃+ H₂O	−0.276
	Ni²⁺ + 2e⁻ → Ni	−0.257
	Sn²⁺ + 2e⁻ → Sn	−0.136
	Pb²⁺ + 2e⁻ → Pb	−0.1251
	Hg₂I₂+ 2e⁻ → 2Hg + 2I⁻	−0.0405
	Fe³⁺ + 3e⁻ → Fe	−0.04
	2H⁺ + 2e⁻ → H₂	0.0000
	Sn⁴⁺ + 2e⁻ → Sn²⁺	0.154

	Half-Reation	E Volts

	SO₄ ²⁻ + 4H⁺ + 2e⁻ → H₂SO₃+ H₂O	0.158
	Cu²⁺ + e⁻ → Cu⁺	0.159
	HAsO₂+ 3H⁺ + 3e⁻ → As + 2H₂O	0.248
	UO₂ ²⁺ + 4H⁺ + 2e⁻ → U⁴⁺ + 2H₂O	0.27
	Bi³⁺ + 3e⁻ → Bi	0.3172
	Cu²⁺ + 2e⁻ → Cu	0.340
	O₂+ 2H₂O + 4e⁻ → 4OH⁻	0.401
	Cu⁺ + e⁻ → Cu	0.520
	I₂+ 2e⁻ → 2I⁻	0.5355
	H₃AsO₄+ 2H⁺ + 2e⁻ → HAsO₂+ 2H₂O	0.560
	O₂+ 2H⁺ + 2e⁻ → H₂O₂	0.695
	Rh³⁺ + 3e⁻ → Rh	0.7
	Tl³⁺ + 3e⁻ → Tl	0.72
	Fe³⁺ + e⁻ → Fe²⁺	0.771
	NO₃ ⁻ + 2H⁺ + e⁻→ NO₂+ H₂O	0.775
	Hg₂ ²⁺ + 2e⁻ → Hg	0.7960
	Ag⁺ + e⁻ → Ag	0.7991
	O₂+ 4H⁺ (10⁻⁷M) + 4e⁻ → 2H₂O	0.815
	AmO₂ ⁺ + 4H⁺ + e⁻ → Am⁴⁺ + 2H₂O	0.82
	NO₃ ⁻ + 2H⁺ + 2e⁻ → NO₂ ⁻ + H₂O	0.835
	OsO₄+ 8H⁺ + 8e⁻ → Os + 4H₂O	0.84
	Hg²⁺ + 2e⁻ →Hg	0.8535
	2Hg²⁺ + 2e⁻ → Hg₂ ²⁺	0.9110
	Pb²⁺ + 2e⁻ → Pb	0.915
	NO₃ ⁻ + 4H⁺ + 3e⁻ → NO(g) + 2H₂O	0.957
	Br₂+ 2e⁻ → 2Br⁻	1.0652
	SeO₄ ²⁻ + 4H⁺ + 2e⁻ → H₂SeO₃+ H₂O	1.151
	Ir³⁺ + 3e⁻ → Ir	1.156
	Pt²⁺ + 2e⁻ → Pt	1.188
	O₂+ 4H⁺ + 4e⁻ → 2H₂O	1.229
	Tl³⁺ + 2e⁻ → Tl⁺	1.25
	Pb⁴⁺ + 2e⁻ → Pb²⁺	1.263
	Cl₂+ 2e⁻ → 2Cl⁻	1.35828
	AU³⁺ + 2e⁻ → Au⁺	1.36
	Cr₂O₇ ²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O	1.36
	MnO₄ ⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O	1.51
	Au³⁺ + 3e⁻ → Au	1.52
	H₅IO₆+ H⁺ + 2e⁻ → IO₃ ⁻ + 3H₂O	1.603
	2HBrO + 2H⁺ + 2e⁻ → Br₂+ 2H₂O	1.604
	PbO₂+ SO₄ ²⁻ + 4H⁺ + 2e⁻ → PbSO₄+ 2H₂O	1.698
	H₂O₂+ 2H⁺ + 2e⁻ → 2H₂O	1.763
	Au⁺ + e⁻ → Au	1.83
	Co³⁺ + e⁻ → Co²⁺	1.92
	S₂O₈ ²⁻ + 2e⁻ → 2SO₄ ²⁻	1.96
	O₃+ 2H⁺ + 2e⁻ → O₂+ H₂O	2.075
	F₂+ 2e⁻ → 2F⁻	2.87
	F₂+ 2H⁺ + 2e⁻ → 2HF	3.053

With this in mind, the applicants have synthesized and tested the following composites: Fe-BTC/PBDT, Fe-BTC/PHQ, Fe-BTC/PpPDA, Fe-BTC/PTA and Fe-BTC/PDA. In all polymerization reactions, the porous template retains its structural integrity, as determined by the powder x-ray diffraction patterns of FIG. 7.
These new composites are quite porous as illustrated by the results of nitrogen adsorption isotherms (77K) of FIG. 8.
Attenuated total reflectance infrared spectroscopy illustrate new peaks from the vibration modes of the functional groups of the polymers of these composites (see FIG. 9). Moreover, FIG. 10 shows numerous crystal facets hinting at polymerization inside the pores.
FIG. 11a illustrates that the composites Fe-BTC/PDA and Fe-BTC/PTA are capable of reducing Au³⁺ to Au⁰. For each experiment, ˜10 mg of Fe-BTC/PTA or ˜10 mg Fe-BTC-PDA were soaked in 20 mL of Milipore water containing 500 ppm of Au³⁺ for 24 hours.
Hereunder is the proposed mechanism of the Fe-BTC/PDA composite's enhanced properties for Au³⁺ remediation from water.
Such a mechanism is confirmed by FIG. 11b that shows the apparition of solid gold Au⁰(s) after contacting Fe-BTC/PDA. Similar results are obtained with Fe-BTC/PTA composite.
For each experiment of FIGS. 12a and 12b , 10 mg of Fe-BTC, Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT were soaked in 20 mL of the Millipore water spiked with Au³⁺ for 24 hours. All the studied composites Fe-BTC/PDA, Fe-BTC/PTA, BTC/PHQ, Fe-BTC/PpPDA and BTC/PBDT, in a 1 ppm solution, have the ability to remove over 99% of gold from water compared to the Fe-BTC alone which only retains 74% of the gold as shown in FIG. 12a . While the capacities of all composites have not been determined, Fe-BTC/PDA, is able to remove up to 1.3 g of Au per gram of composite. The applicants estimate the cost of the raw materials needed to make the composite, if bought on a ton scale, to be around 2.5 USD per kg of composite.
For each experiment of FIGS. 13a and 13b , 10 mg of Fe-BTC, Fe BTC/PDA, Fe BTC/PTA, Fe BTC/PHQ, Fe BTC/PpPDA or Fe BTC/PBDT were soaked in 20 mL of the Millipore water spiked with Pd²⁺ for 24 hours. Results of FIG. 13a show that, for palladium, the situation is similar as for gold. Indeed, all composites remove 99% of palladium from water in a 550 ppb Pd aqueous solution compared to 78% for the Fe-BTC template.
For each experiment of FIGS. 14a and 14b , 10 mg of Fe-BTC, Fe BTC/PDA, Fe BTC/PTA, Fe BTC/PHQ, Fe BTC/PpPDA or Fe BTC/PBDT were soaked in 20 mL of the Millipore water spiked with Ag+ for 24 hours. The data reveals over 99% silver removal for one of the composites, which is significantly enhanced compared to Fe-BTC. Results of FIG. 14a show that, for silver, the situation differs. The bare framework Fe-BTC can remove 86% of Ag ions from water in a 718 ppb Ag aqueous solution. Fe-BTC/PDA, Fe-BTC/PpPDA and Fe-BTC/PHQ can remove over 95% of Ag of the same 718 ppb Ag aqueous solution. In the same 718 ppb Ag aqueous solution, Fe-BTC/PBDT only removes 81.8%, which is less than the bare framework and Fe-BTC/PTA removes only 0.8% of Ag illustrating no activity.
From a roughly 100 ppm solution of Au, the bare framework is only able to remove 43% of the gold from water, but all the composites can remove over 99% of the gold, with some composites reaching even 99.9% removal as shown in FIG. 12 b.
For Pd, the bare framework can remove 96% from a 55 ppm solution while all the other composites can remove over 99% of Pd, as shown in FIG. 13 b.
Concerning Ag, at roughly 90 ppm (90.5 ppm), most composites showed removal capabilities less than the bare framework, but interestingly Fe-BTC/PDA is the only composite that is highly active for silver, removing over 99% of Ag from water, as shown in FIG. 14 b.
These results illustrate that the different redox active composites Fe-BTC/PBDT, Fe-BTC/PHQ, Fe-BTC/PpPDA, Fe-BTC/PTA and Fe-BTC/PDA can reduce and/or remove precious metals from aqueous media.
It is to be noted that changing the polymer alters the activity and hence the selectivity of the composite towards certain precious metals. Remarkably the composites are highly selective and fast.
For the experiment of FIG. 15a , Rhone River water was spiked with 1 ppm of Au³⁺ and then 10 mg of Fe-BTC/PTA were soaked in the 20 mL of water for 24 hours. For the experiment of FIG. 15b , ˜10 mg Fe-BTC/PTA were soaked in 20 mL of Milipore water spiked with 1 ppm of Au³⁺. Using Fe-BTC/PTA as an example, it as been found that it removes over 99% of gold in a 1 ppm aqueous solution in less than 30 minutes, as shown in FIG. 15b . Fe-BTC/PTA illustrate high selectivity for Au over common inteferents found in river water, such as Ca and large organics.
Further it was discovered that Fe-BTC/PTA can selectively remove over 99% of gold from a 1 ppm Au³⁺ solution obtained from Milipore water (FIG. 16). For this experiment Millipore water was spiked with 1000 ppb of Au³⁺ and 200000 ppb of Cu²⁺ and Ni²⁺. 20 mL of the solutions were treated with 10 mg of Fe-BTC/PTA for 24 hours. The results illustrate that the composite Fe-BTC/PTA exhibits high selectivity over high concentrations of these other common ions, copper and nickel.
To stress the selectivity capabilities of the Fe-BTC-redox polymer, the applicants have assessed its Au removal performance in the presence of high concentrations of abundant Cu and Ni seen in electroplating industry for example. To do so, Millipore water was spiked with 190000 ppb of Au³⁺ and 200000 ppb of Cu²⁺ and Ni²⁺. 20 mL of the solutions were treated with 10 mg of Fe-BTC/PTA for 24 hours. Results are presented in FIG. 17. Fe-BTC/PTA removes over 99% of a roughly of 190000 ppb solutions of Au (FIG. 17) in the presence of roughly 200000 ppb of Cu and Ni, with little to no removal of Cu or Ni from water, as shown in FIG. 18.
At lower concentration, 1000 ppb of Au, the results are remarkable: Fe-BTC/PTA is capable of removing 99% of Au in the presence of roughly 200000 ppb concentration of Cu and Ni, as shown in FIG. 16. The concentration of Cu and Ni is 200 times the concentration of Au and there is no uptake of Cu or Ni. This implies the selectivities are tremendous.
After Fe-BTC/PTA, the ability of Fe-BTC/PpPDA to remove gold from water has also been studied more specifically.
The experiments of FIGS. 17a to 17e evaluate the capacity of Fe-BTC/PpPDA to extract gold from a simulated e-waste solution. Said solution is obtained by spiking the main components in e-waste including ˜870 ppm of Cu²⁺ and Ni²⁺ and ˜9 ppm of Au³⁺ in a Rhone water solution that already contains many competing ions and organics.
In the experiment of FIGS. 17a and 17b , 10 mg of Fe-BTC/PpPDA were added to a sample of 20 mL of said simulated e-waste solution. Then, they were placed in a thermo scientific maxQ4450 orbital shaker at 420 rpms and held at a constant temperature of 28° C. under shaking for 24 hours.
For the experiment of FIG. 17c , a sample of 20 mL of the aforementioned simulated e-waste solution was treated with 10 mg of Fe-BTC/PpPDA. At each time point (1, 2, 5, 10, 15, 20 and 30 minutes), the aqueous samples were isolated and filtered using a 25 mm hydrophilic PTFE membrane syringe filter with 0.22 μm pores. After elemental analysis, the percent removal of gold was calculated.
The results of said experiments show that Fe-BTC and Fe-BTC/PpPDA remove 75% and 99.9% of the gold respectively (FIG. 17c ) from said simulated e-waste solution, with a minimal uptake of the other ions (FIGS. 17a and 17b ). The lack of uptake of the other ions is likely due to gold's higher reduction potential combined with higher polarizability when compared to the other ions present.
Further, as shown in FIG. 17c , like for Fe-BTC, for Fe-BTC/PpPDA the gold is extracted in less than 2 minutes. This remarkable rapid extraction rate is attributed to the extrinsic porosity of PpPDA introduced by the MOF template.
The Fe-BTC/PpPDA composite's extraction efficiency was also investigated at varying pH, within the same e-waste simulated solution. For this experiment, 10 mg of Fe-BTC/PpPDA was added to samples of 20 mL of the aforementioned e-waste solution with varying pH. For each sample the pH was adjusted using 0.02 M aqueous solutions of HCl and NaOH and was then remeasured. The vials were placed in a Thermo Scientific MaxQ4450 Orbital Shaker for 24 hours at 420 rpms and held at a constant temperature of 28° C. The samples were then filtered using a 25 mm hydrophilic PTFE membrane syringe filter with 0.22 pm pores to remove any solids for elemental analysis of the aqueous media.
The results of this experiment are shown in FIG. 17d . Remarkably, more than 99% removal is achieved for solutions between pH 2-10. At pH 11 gold removal is only slightly reduced to ˜98%, indicating that at these concentrations, pH does not hinder the composite's extraction properties.
The aforementioned assessments indicate that the composite Fe-BTC/PpPDA has the unprecedented selectivity and the relevant stability needed for various gold extraction processes.
While the material rapidly extracts Au³⁺ (FIG. 17c ), the quantity of gold compared to the composite mass is about 0.018 weight % which is quite low, due to low starting concentrations.
As such, the material must be able to concentrate gold over time or with regeneration for actual implementation into recovery processes. So, the regenerability of Fe-BTC/PpPDA was tested. The results of this experiment are shown in FIG. 17 e.
For this experiment, 50 mg of Fe-BTC/PpPDA was exposed to a sample of 20 mL of previously mentioned simulated e-waste solution for five minutes. After said exposure the composite was removed from the solution and exposed to another sample of 20 mL of previously mentioned simulated e-waste solution for five more minutes, this process was repeated nine times. Then the composite Fe-BTC/PpPDA was soaked in ascorbic acid for four hours to reduce the imine (═NH) generated during Au³⁺ reduction back to the amine (—NH₂) and then washed with ethanol. The regenerated Fe-BTC/PpPDA composite was again soaked successively ten more times into samples of the e-waste simulated solution, subsequently regenerated, and then washed. The same process was repeated one more time.
The results of this experiment are shown in FIG. 17e . In this figure, the grey bars correspond to successive cycles of exposure and every white bar constitutes regeneration with ascorbic acid. They reveal that the removal efficiency remained at 99% removal for four exposures. After cycle five, the removal efficiency decreases to 98% and after ten cycles to 81%. It should be noted that after each regeneration, 99% removal of Au³⁺ is observed. However, there is a decrease in performance with continued exposure. This is likely due to a combination of material loss, decrease in extraction rate, and/or pore clogging as the gold is becoming more concentrated inside the composite.
After three regeneration cycles, the composite reclaimed 0.29 mg of Au⁰per mg of composite, a value that is readily increased with continued cycling.
The composite/Au powder resulting from the previously described experiment associated to FIG. 17e was loaded in an MTI OTF-1200X tube furnace and heated to 900° C. at a ramp of 30° C. per minute in air. The temperature was held for two hours and then allowed to cool to room temperature. The brown powder was transferred to a vial and 10 mL of concentrated HCl was added. The vial was loaded into a thermos scientific maxQ4450 orbital shaker at 420 rpms and held at a constant temperature of 28° C. for 24 hours. The Au particles were separated from the obtained yellow acidic solution and soaked in a fresh batch of concentrated HCl. The sample was allowed to shake at 420 rpms at a constant temperature of 28° C. for another 12 hours. The Au particles were then separated from the clear acidic solution and washed with distilled water 3 times. PXRD was performed to confirm neutral state gold. The purified Au was then dissolved in aqua regia and underwent subsequent elemental analysis to determine the purity. It was determined to be 23.9 karat which is very high purity.
The gold can also be concentrated over time. In order to demonstrate that, the applicant have placed 10 mg of Fe-BTC/PpPDA in 10 L of a solution containing 0.8 ppm Au³⁺. All of the gold was removed over a three-weeks period without regeneration steps. It means that the composite has extracted a weight of gold equal to about 80% of its mass. These results demonstrate that the Fe-BTC/PpPDA can concentrate metals also without regeneration step and that if simply soaked in large quantities of solutions with low concentrations of gold, the composite can still concentrate gold inside.
In order to confirm the effectiveness of the Fe-BTC/PpPDA composite for gold extraction from e-waste, gold was extracted from actual solutions obtained from e-waste. For this purpose, metals were mechanically removed from a computer processing unit (CPU), and then leached into an aqueous N-bromosuccinimide (NBS) and pyridine (Py) solution. It should be noted that, like ore extraction, gold extraction from e-waste is currently done using toxic alkali cyanide agents and/or extreme pH conditions. Here, a facile method that utilizes an aqueous solution of N-bromosuccinimide and pyridine at near neutral pH levels has been used (reference is made to the article « Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials » Angew. Chem. Int. Ed. 56, 9331-9335, (2017), Yue, C. et al.) This oxidative leaching process is more environmentally benign than the aforementioned methods. The resulting solution is a blue solution that had a metal composition of 1470 ppm Cu²⁺, 95 ppm Ni²⁺ and 7.3 ppm Au³⁺.
After soaking 30 mg of the composite Fe-BTC/PpPDA in a 20 mL sample of said blue solution, 86% gold removal was obtained in less than two minutes, over 90% in 10 minutes, and 95% removal in 30 minutes, as shown in FIGS. 18a and 18c . The composite Fe-BTC/PpPDA is over 662 times more selective for Au³⁺ than Cu²⁺ and Ni²⁺ based on the calculated distribution coefficient, k_d, 1.3×10⁴mL/g, 19.13 mL/g, and 5.38 mL/g, respectively.
With continued cycling and subsequent composite removal, it is expected that the extracted gold metal will be free of other competing metals, as previously observed in river water (FIG. 17a-17e ). Hence, it is concluded that Fe-BTC/PpPDA has great potential for Au recovery from e-waste.
The applicants have also studied the rate of gold removal from several matrices including river water, wastewater, electronic waste leaching solution, sea water, and a solution obtained after treating incinerated sewage with NBS/Py.
For the experiment in river water, 10 mg of Fe-BTC/PpPDA were soaked in 20 mL of a solution comprising Rhone river water spiked with 120 ppb of Au³⁺, for various periods of time. After the time point was reached the sample was filtered and elemental analysis was done to calculate the % removal of gold. Such a concentration of 120 ppb of Au approaches the gold concentration in Alaskan river which is usually between 60 and 120 ppb. Indeed, mining operations near the fresh water sources tend to discharge metal ions into the environment.
For the experiment in waste water, 10 mg of Fe-BTC/PpPDA were soaked in 20 mL of a solution of waste water that contained 3.7 ppb Au received from a waste water treatment plant in Switzerland, for various periods of time. After the time point was reached the sample was filtered and elemental analysis was done to calculate the % removal of gold.
For the experiment in electronic waste leaching solution, 30 mg of Fe-BTC/PpPDA were soaked in 20 mL of a solution of electronic waste water obtained by oxidizing and hence dissolving the metals extracted from a CPU in a NBS/Py solution (same solution as the one studied in FIG. 18a ), for various periods of time. Said solution of NBS/Py had 1470 ppm Cu²⁺, 95 ppm Ni²⁺ and 7.3 ppm Au³⁺. After the time point was reached the sample was filtered and elemental analysis was done to calculate the % removal of gold.
For the experiment in Mediterranean sea water, 10 mg of Fe-BTC/PpPDA were soaked in 20 mL of Mediterranean sea water spiked with 1 ppm Au³⁺, for various periods of time. Said Mediterranean sea water had many other complex ions in the solution including Ca, Mg, Na, K, Sr, B and Pb. After the time point was reached the sample was filtered and elemental analysis was done to calculate the % removal of gold. We find that the final concentration of Au³⁺ is below our detectable limit, indicating it is less than 100 ppt.
For the experiment in incinerated ash leaching solution, 50 mg of Fe-BTC/PpPDA were soaked in 10 mL of an incinerated ash leaching solution for various periods of time. Said solution comes from a treatment plant in Switzerland and the NBS/Py previously mentioned method was used to extract the metals. The resulting solution contained 5.47 ppm of Au³⁺ and many other species such as Ca²⁺, Cs⁺, Mg²⁺, Na⁺, Fe³⁺, Cu²⁺, K⁺, B³⁺, Zn²⁺ and Rb⁺. After the time point was reached the sample was filtered and elemental analysis was done to calculate the % removal of gold. FIGS. 18d and 18e show the identity and concentrations of the metals present in said incinerated ash leaching solution before and after a 24 hours treatment with said Fe-BTE/PpPDA.
The percents removal of gold over time resulting from the five experiments mentioned above are illustrated in FIGS. 18b and 18 c.
Concerning waste water, the results show that, in less than 1 minute 90% removal is achieved, and in under 30 minutes over 99% of Au³⁺ was extracted from the wastewater solution and the final concentration was <10 ppt. This extraction is truly remarkable, particularly considering the high concentrations of organics in wastewater, which often competitively complex metal ions and also often foul mesoporous adsorbents.
Concerning the incinerated ash leaching solution, the results show that in less than two minutes, the composite Fe-BTC/PpPDA is able to extract 61% of the Au³⁺ from the solution and then reaches 90% removal in 24 hours. Moreover, it can be observed little to no uptake of most of the other metal interferents present, as shown in FIGS. 18d and 18e . Although the Cu²⁺ concentration is decreased from 1.76 ppm to 0.16 ppm, the removal capacity is quite low. Further, Cu²⁺ is readily desorbed, and hence will not influence the gold purity.
Regarding the river water solution, remarkably, in less than 2 minutes the applicants have observed 90% Au extraction and then 99% removal in less than 30 minutes in the solution indicating that Fe-BTC/PpPDA could be implemented in mining Au from surface water sources.
One of the most difficult challenges is gold recovery from the sea. Indeed, it is estimated that the ocean contains gold valued at 720 trillion US dollars. But, unfortunately, gold in seawater has an ultra-low concentration, less than 20 ppt, and is one of the most complex matrices in the world. For example, competing ions, such as Na⁺ can have concentrations that are 2×10⁹times higher than that of Au³⁺. As such, extraction of the precious metal from the sea is conceptually thought to be nearly impossible. The experiment conducted for FIGS. 18b and 18c in Mediterranean Sea water spiked with 1 ppm Au³⁺ showed that Fe-BTC/PpPDA is able to extract 95% of the gold in 20 minutes and then reached more than 99% removal in 30 minutes. It should be noted that given the complexity of the solution, it was not possible to obtain the remaining concentration of gold in the seawater. However, it is below 100 ppt based on the detection limit of the ICP-MS method. As this value is approaching the gold concentration in the sea, the applicants daringly attempted to concentrate Au directly from the ocean. For this, 0.5 g of Fe-BTC/PpPDA was soaked in the ocean for 1 week off the coast of Jacksonville Fla., USA. The sample was then recovered, dried and digested in aqua regia to determine if any Au was extracted while soaking. The post-treated sample was found to contain 0.01 wt % Au. While this is a small amount, with much longer soak times and subsequent regeneration, composites like Fe-BTC/PpPDA might bring new found optimism towards even mining Au from the sea.
Another compound has been made by functionalizing a porous template “Cu-BTC” by in-situ polymerization of bio-derived para-phenylenediamine onto the internal surface of the pores of Cu-BTC, thereby introducing extrinsic porosity to the intrinsically non-porous polymer PpPDA and obtaining Cu-BTC/PpPDA.
FIG. 22 shows powder X-ray diffraction patterns of the porous template HKUST-1 (also known as Cu-BTC). The template was soaked in para-Phenylenediamine (pPDA) leading to polymerized Poly-para-phenylenediamine (PpPDA). Cu-BTC and Cu-BTC /PpPDA were soaked in water for 7 days. The diffraction patterns show that the polymerization process enhances the stability of the Cu-BTC porous template in water.
FIG. 23 CO₂adsorption isotherms at 25° C. for Cu-BTC and Cu-BTC/PpPDA. Cu-BTC and Cu-BTC/PpPDA were degassed under vacuum at 125° C. for 15 hours at a ramp rate of 1.0° C. per minute. After activation, adsorption experiments were performed at 25° C. using a water bath. It is observed that Cu-BTC/PpPDA has an enhancement in CO₂adsorption at ambient temperatures compared to HKUST-1. The increase in adsorption at low pressures illustrates that the binding energy of CO₂increased compared to Cu-BTC.
Images of FIGS. 24a,b and c imply the polymer is going inside of the porous template.
These results show that the polymerization of para-phenylenediamine onto the surface of the pores of Cu-BTC can also enhance its stability in water.
The applicants have also tested Fe-BTC/PDA composite for extraction of Pb from water sample. As the standard reduction potential of Pb is much lower it was not expected to observe a reduction reaction.
In a first experiment (see FIG. 3a ), the applicants have determined the rate of lead removal. For this experiment, a solution of Pb²⁺ was treated with Fe-BTC or Fe-BTC/PDA over a period of an hour. For each experiment, 20 mL of Millipore water containing 1 ppm of Pb²⁺ were treated with 20 mg of Fe-BTC or 20 mg of Fe-BTC/PDA. In the solution treated with Fe-BTC/PDA, over 99% of lead is removed to reach drinkable limits in less than a minute.
In a second experiment (see FIG. 3b ), the applicants have determined the lead removal capacity at low Pb concentrations. Fe-BTC or Fe-BTC/PDA were soaked in Millipore water spiked with lead for 24 hours. For the experiment ˜10 mg of Fe-BTC or ˜10 mg Fe-BTC/PDA were added to 20 mL of a 0.9 ppm solution of Pb²⁺.
The results of these experiments are presented in FIGS. 3a and 3b and show the rapid and selective removal of lead from water samples containing high concentration of Pb²⁺. The composite Fe-BTC/PDA binds up to 394 mg Pb²⁺ per gram of composite, and removes over 99% of Pb²⁺ ions from a 1 ppm solution to yield drinkable levels in less than a minute (see FIG. 3a ).
Therefore, the applicants have discovered that Fe-BTC/PDA is able to efficiently reduce the concentration of Pb in water. X-ray diffraction experiments have been made and have shown no other lead compound. These results seem to confirm that the mechanism of action of the composite Fe-BTC/DPA for extraction of Pb from water is different from the aforementioned reduction process observed for Hg²⁺ and various precious metals.
The composite Fe-BTC/PDA has also proven to be easily regenerated and cycleable in this context, as illustrated by the results of FIG. 3c . For this experiment, 0.500 g of Fe-BTC/PDA was added to a 1 L solution of Milipore water spiked with 1000 ppm of Pb²⁺. The remaining Pb²⁺ concentration in the aqueous media were analyzed to determine the lead capacity (Qe, mg/g). The Fe-BTC/PDA sample was then added to 0.001 M solutions of EDTA (ethylenediaminetetracetic acid). The samples were filtered, washed with methanol, dried and weighed. The regenerated composites were then added to 1000 ppm solutions of Pb²⁺ again. This procedure was repeated three more times to obtain the capacity Qe (mg/g) for each of the four cycles.
Concerning Pb extraction, other experiments have been made in order to study the selectivity of the porous template Fe-BTC and of the composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA and Fe-BTC/PBDT, it means their ability to extract Pb from water comprising other common ions such as Na, Mg, Ca, Sr and K and organics.
A first experiment has been made in a sample of Rhone river water comprising an initial concentration of Pb around 700 ppb and 39.49 ppm Na, 9.18 ppm Mg, 74.13 ppm Ca and 1.21 ppm Sr (FIGS. 20a and 20b ). For FIG. 20b , 10 mg of Fe-BTC or the composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA or Fe-BTC/PBDT were soaked in 20 mL of Rhone River water spiked with 700 ppb of lead for 24 hours. Results of FIG. 20b show that Fe-BTC is able to remove 72% of Pb, while Fe-BTC/PDA, Fe-BTC/PTA and Fe-BTC/PpPDA are able to extract over 99% of Pb (below detectable limit) and Fe-BTC/PHQ and Fe-BTC/PBDT are able to remove more than 93% of Pb. It means that almost all the studied composites reduce the concentration of Pb²⁺ to what is deemed drinkable by the Environmental Protection Agency in the presence of other chemical species present in the river water (FIG. 20a ).
A second experiment has been conducted in Mediterranean Sea water. For this experiment (FIG. 21b ), 10 mg of Fe-BTC or the composites Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ or Fe-BTC/PpPDA were soaked in 20 mL of Mediterranean Sea water spiked with 350 ppb of lead for 24 hours. The results show that Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PHQ, Fe-BTC/PpPDA are able to remove over 99% (below detectable limit) of Pb a roughly of 350 ppb solution of Pb in the presence of 2640 ppm of Na, 407.89 of Cu, 378.86 ppm of Mg, 546.12 ppm of Ca, 8.66 ppm of Sr and 5.22 ppm of B, as shown in FIGS. 21a and 21b . Fe-BTC/PBDT is able to remove 91.4% of Pb of this same solution. That is to say, almost all the studied composites reduce the concentration of Pb²⁺ to what is deemed drinkable by the Environmental Protection Agency in the presence of other chemical species present in the Mediterranean Sea water, refer to FIG. 21 a.
These experiments show that the studied composites adsorb a significant amount of lead. In most composites it is possible to get below the EPA limit of lead in water in both Rhone river water and sea water. These graphs show high selectivity as there are many other ions in solution that compete with lead.
The applicants have also studied the efficiency of the composite according to the invention for extraction of some specific chemical species from a gas medium.
FIG. 19 shows CO₂adsorption isotherms at 25° C. for Fe-BTC and Fe-BTC/PpPDA. Fe-BTC and Fe-BTC/PpPDA were degassed under vacuum at 125° C. for 15 hours at a ramp rate of 1.0° C. per minute. After activation, adsorption experiments were performed at 25° C. using a water bath. It is observed that Fe-BTC/PpPDA has an enhancement in CO₂adsorption at ambient temperatures compared to Fe-BTC. The increase in adsorption at low pressures illustrates that the binding energy of CO₂increased compared to Fe-BTC. Therefore the composites according to the invention show high promise for air purification. It seems possible to change the binding energy of certain small molecules with different polymers.
The introduction of porosity to redox active polymers has shown improvements in chemical separation of metals in water but also has shown an enhancement in small molecule gas adsorption and framework stability as well.
In view of these results, the applicants believe that the composites according to the invention will be good for adsorption of Cl₂gas, ozone, ammonia, and also volatile organics compounds from air. It is to be expected that with the high reduction potential of Cl₂or ozone that the composites according to the invention would be very efficient for scrubbing toxic chlorine gas or ozone from air.
Moreover, it is known that volatile organic compounds (VOCs) are well absorbed by intrinsically porous polymers (polymers that are naturally porous), as mentioned for example in the publication “Rapid removal of organic micropollutants from water by β-cyclodextrin polymer”, Alsbaiee et al. 2016-doi:10.1038/nature16185. And, as demonstrated by the applicants, it is possible to introduce extrinsic porosity to polymers using a porous template. For these reasons, it is supposed that the composites according to the present invention would also be efficient in extracting VOCs from both air and water.
According to the invention, VOCs are typically chosen among ethanol, methanol, butanone,ethylbenzene, acetone, n-hexane, cyclohexane, toluene, benzene, various xylenes, dichloromethane and n-butylamine, benzothiophene, thioanisole, Methyl tert-butyl ether, Dibromochloropropane, Chloroform, Perchloroethane, 1,1,1-Trichloroethane, 1,2-chloropentane,ethylene dibromide, 1,2-Dichloroethene, Vinyl chloride, Dichlorodofluoromethane, Decabromodiphenyl ether, Trichloroethylene (TCE), organochlorine insecticides (DDT).
The methods that have been used in order to synthesize Fe-BTC, Fe-BTC/PDA, Fe-BTC/PTA, Fe-BTC/PpPDA, Fe-BTC/PHQ, Fe-BTC/PBDT and Cu-BTC are described in details below. The method to obtain the compound of interest Fe-BTC/PDHAA is also disclosed.
As mentioned before other MOFs such as Cu-TDPAT and Al-BDC-NH₂can be used in the context of this invention. Methods for obtaining them are also disclosed.

Synthesis of Fe-BTC (Porous Template)

Iron(III) chloride hexahydrate (FeCl₃.6H₂O), 97% was bought from Alfa Aesar and 1,3,5-benzenetricarboxylic acid (trimesic acid, BTC), 98% was bought from ABCR GmbH and used without further purification. 19.44 g of iron(III) chloride hexahydrate, 6.72 g of trimesic acid and 240 mL of distilled water were loaded in a 1 L teflon reactor.
The reactor was placed in a 1200 watts Milestone SynthWAVE Microwave Single Reaction chamber and pressurized to 5 bars with nitrogen. The reaction was heated to 130° C. over 5 min and remained at the temperature for 60 mins. After the reaction was cooled down to room temperature the orange solid was filtered under vacuum and washed with copious amounts of water and methanol. The resulting powder was loaded into a double thickness whatman cellulose extraction thimble and underwent soxhlet purification with methanol for 24 hours. After purification the sample was dried under vacuum overnight. The material was activated under vacuum at 150° C. for 17 hours before nitrogen adsorption and standard characterization.

Free Base Dopamine Synthesis (Monomer for PDA)

Dopamine HCl, dry sodium hydride 95% and anhydrous solvents were bought from Sigma Aldrich and used without further purification. In a N₂purged, 2-neck round bottom flask, 10 g of Dopamine HCl was mixed with 80 mL of anhydrous tetrahydrofuran (THF) and 80 mL of anhydrous methanol. 1.264 g of dry sodium hydride 95% was added slowly in small quantities over a period of approximately 15 minutes. The reaction mixture was allowed to stir for 48 hours with flowing N₂. After the completion of the reaction, the mixture was filtered under vacuum and washed with copious amounts of THF. The white powder was dried and kept under vacuum until further use.
¹H NMR (400 MHz, Methanol-d4): δ=6.72 (d, J=8.0 Hz, 1H), 6.67 (d, J=2.1 Hz, 1H), 6.55 (dd, J=8.0, 2.1 Hz, 1H), 2.87 (t, J=7.1 Hz, 2H), 2.65 (t, J=7.1 Hz, 2H)

Synthesis of Fe-BTC/PDA (Polydopamine)

Fe-BTC was activated at 150° C. under vacuum overnight in a 500 mL 2-neck round bottom flask using a schlenk line and an oil pump. After activation of Fe-BTC, the reaction vessel was cooled to room temperature and then N₂was flowed over the sample for 10 minutes. After the sample was sealed under an inert atmosphere, 400 mL 0.02 M anhydrous methanol solution containing the as-prepared free base dopamine, was prepared in a glove box purged with N₂. Using a steel cannula and N2, the methanol/dopamine solution was transferred to the flask containing the activated Fe-BTC. Over a period of 1 hour, the orange powder turned dark purple indicative of polymerization. The reaction was allowed to stir for 24 hours at room temperature under an inert atmosphere. After completion, the reaction mixture was filtered under vacuum and washed with copious amounts of methanol and water. To remove any excess dopamine, the resulting purple powder was loaded into a double thickness Whatman cellulose extraction thimble, and the composite underwent soxhlet extraction with methanol for 24 hours under N₂. Afterwards, the sample was dried under vacuum at room temperature over night, and then the material was activated under vacuum at 125° C. for 17 hours before nitrogen adsorption and standard characterization.
Elemental Analysis Fe-BTC/PDA-19: C 39.553% N 1.81% H 2.45% Fe 17.84%

Synthesis of Fe-BTC/PTA (Polytyramine)

Tyramine 99% and anhydrous solvents were bought from Sigma Aldrich without further purification. 2 g of Fe-BTC was activated at 150° C. under vacuum vernight in a 500 mL 2-neck round bottom flask using a schlenk line and an oil pump. After activation, the reaction was cooled to room temperature and then N₂was flowed over the sample. A 400 mL anhydrous ethanol 0.06 M solution of tyramine was prepared in a nitrogen purged glove box. Using a steel cannula and N₂, the ethanol/tyramine solution was transferred to the flask containing the activated Fe-BTC. The orange powder turned dark purple indicative of polymerization. The reaction was allowed to stir for 24 hours at room temperature under an inert atmosphere. After completion, the reaction mixture was filtered under vacuum. Once dry the sample was placed in a vacuum oven and heated at 125° C. over night. The material was activated under vacuum at 125° C. for 17 hours before nitrogen adsorption and standard characterization.

Synthesis of Fe-BTC/PpPDA

para-phenylenediamine >99% and anhydrous solvents were bought from Sigma Aldrich without further purification. 0.300 g of Fe-BTC was activated at 150° C. under vacuum overnight in a 100 mL 2-neck round bottom flask using a schlenk line and an oil pump. After activation, the sample was cooled to room temperature and then N₂was flowed over the sample. 0.384 g of pphenylenediame was added to 50 mL anhydrous methanol in a nitrogen purged glove box. Using a steel cannula and N₂, the ethanol/para-phenylenediamine solution was transferred to the flask containing the activated Fe-BTC. The orange powder turned dark purple indicative of polymerization. The reaction was allowed to stir at room temperature under an inert atmosphere for 24 hours. After completion, the powder was recovered using vacuum filtration. The material was activated under vacuum at 125° C. for 17 hours before nitrogen adsorption and standard characterization.

Synthesis of Fe-BTC/PHQ

Hydroquinone 99.5% and anhydrous solvents were bought from Sigma Aldrich without further purification. 0.2 g of Fe-BTC was activated at 150° C. under vacuum overnight in a 100 mL 2- neck round bottom flask and schlenk line and an oil pump. After activation, the sample was allowed to cool to room temperature and then N₂was flowed over the sample. 0.869 g of hydroquinone was added to 50 mL of anhydrous ethanol in nitrogen purged glove box. Using a steel canula, and N₂, the ethanol/hydroquinone solution was transferred to the reaction flask containing Fe-BTC. The reaction was allowed to stir for 1 hour to allow the monomers to diffuse through the porous system. After the diffusion of the monomers equilibrated, 1.5 mL of 25% NH₃in water was added to the reaction vessel with a syringe. The orange powder turned dark purple indicative of polymerization. The reaction was allowed to stir at room temperature under an inert atmosphere for 24 hours. After completion, the powder was recovered using vacuum filtration. The material was activated under vacuum at 125° C. for 17 hours before nitrogen adsorption and standard characterization.

Synthesis of Fe-BTC/PBDT

1,4-benzenedithiol 99% and anhydrous solvents were bought from Sigma Aldrich without further purification. 0.2 g of Fe-BTC was activated at 150° C. under vacuum overnight in a 100 mL 2-neck round bottom flask and schlenk line and an oil pump. After activation, the sample was allowed to cool to room temperature and then N₂was flowed over the sample. 0.056 g of 1,4-benzendithiol was added to 50 mL of ethanol in a nitrogen purged glove box. Using a steel canula, and N₂, the ethanol/1,4-benzenedithiol solution was transferred to the reaction flask containing Fe-BTC. The reaction was allowed to stir for 1 hour to allow the monomers to diffuse through the porous system. After the diffusion of the monomers equilibrated, 0.073 mL of 25% NH₃in water was added to the reaction vessel with a syringe. The reaction was allowed to stir at room temperature under an inert atmosphere for 24 hours. After completion, the powder was recovered using vacuum filtration. The material was activated under vacuum at 125° C. for 17 hours before nitrogen adsorption and standard characterization.

Synthesis of Fe-BTC/PDHAA

2,5-Dihydroxy-1,4-benzenediacetic acid and anhydrous solvents were bought from Sigma Aldrich without further purification. 0.250 g of Fe-BTC was activated at 150° C. under vacuum overnight in a 100 mL 2-neck round bottom flask and schlenk line and an oil pump. After activation, the sample was allowed to cool to room temperature and then N2 was flowed over the sample. 0.0893 g of 2,5-dihydroxy-1,4-benzenediacetic acid was added to 50 mL of ethanol in a nitrogen purged glove box. Using a steel canula, and N₂, the ethanol/2,5-dihydroxy-1,4-benzenediacetic acid solution was transferred to the reaction flask containing Fe-BTC. The orange powder turned dark purple indicative of polymerization. The reaction was allowed to stir for 24 hours at room temperature under an inert atmosphere. After completion, the reaction mixture was filtered under vacuum. Once dry the sample was placed in a vacuum oven and heated at 125° C. over night. The material was activated under vacuum at 125° C. for 17 hours before nitrogen adsorption and standard characterization.

Synthesis of Cu-BTC

Cu-BTC can be made using a Cu²⁺ salt and trimesic acid. In order to do that, the two compounds are added together in a water ethanol mixture. The material can precipitate out through the addition of base or by heating the solution. The result is a blue powder and is purified using a soxhlet extractor with ethanol as the solvent. The material is highly crystalline and has a surface area up to 2000 m²/g.

Synthesis of Cu-TDPAT

Cu-TDPAT is a copper-containing MOF where copper is linked by TDPAT ligands (where TDPAT=deprotonated 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine).
Since TDPAT is not commercially available, it has to be synthesized, for example by using the following procedures.

- In a 250 mL round bottom flask, mix together 7.6 g of 5-aminoisophthalic acid acid, 2.68 g of NaOH, 4.37 g of NaHCO₃and 70 mL of H₂O.
- Cool the mixture to 0° C. using an ice bath and add drop wise 1.84 g of cyanuric chloride in 35 mL of 1,4-dioxane with an addition funnel.
- Heat the mixture to 100° C. under reflux for 24 hours.
- Once cooled to room temperature, adjust the pH to pH-2 with HCl.
- Recover the resulting solid by vacuum filtration and wash it with distilled water and hot methanol. The resulting solid isa dried powder. It is pure H₆TDPAT ((2,4,6-tris (3,5-dicarboxylphenylamino)-1,3,5-triazine)) which is subsequently used for the synthesis of Cu-TDPAT.
- In a 100 mL bottle, mix together 30 mL of dimethylamine, 30 mL dimethylsulfoxide, 13.5 mL HBF₄and 1.5 mL H₂O.
- After, add 2.46 g of Cu(NO₃)₂.H₂O and 0.45 g of H₆TDPAT to the mixture. Place the bottle in a Thermo Scientific Heratherm oven and heat to 85° C. for 72 hours.
- After completion of the reaction, purify the resulting solid with methanol using a soxhlet apparatus for 24 hours.
- Dry the sample under vacuum and then heat to 125° C. before standard characterization.

Synthesis of Al-BDC-NH₂

Al-BDC-NH₂is a MOF containing Al³⁺ that are linked together by BDC-NH₂ligands (where BDC-NH₂is deprotonated 2,amino terepthalic acid). It can be synthesized as follows.

- In a 250 mL round bottom flask, dissolve completely 544 mg of 2-aminoterephthalic acid in 120 mL of dimethylformamide.
- Stir the solution at 420 rpm and heat to 110° C.
- Divide 1.45 g of AlCl₃.6H₂O into 6 equal portions and add two portions to the heated mixture every 15 minutes.
- Stir the mixture for 3 hours and then turn off the stirring for another 16 hours.
- After completion of the reaction, filter the resulting yellow powder was and underwent soxhlet extraction with ethanol for 24 hours.
- Dry the sample under vacuum and heat at 125° C. before standard characterization.

Material and Methods

Inductive Coupled Plasma Optical Emission Spectroscopy

Precious metal salts and standards were bought from Sigma Aldrich and used without further purification. Precious metals were simulated at different concentrations in water obtained from a millipore purification system and also from the Rhone river (Sion, Switzerland, Latitude: 46.228332, Longitude: 7.369975). The precious metal concentrations were measured using an Agilent 5110 Synchronous Vertical Dual View ICP-OES. Before ICP analysis, all samples, including the standards, controls, and treated water solutions were first filtered using a 25 mm hydrophilic PTFE membrane syringe filter with 0.22 μm pores to remove any solid and then the remaining solutions were treated with HNO₃or HCl, to create a 2%, 3% and 5% acidic solutions. Five wavelengths were chosen for analysis and averaged.

Batch Precious Metal Removal Experiments

Fe-BTC and the composites mentioned above removal capacities were evaluated at low concentrations (1 ppm) and at higher concentrations (>60 ppm). Aqueous solutions of Au³⁺ (AuCl₃), Pd²⁺ (Pd(NO₃)₂and Ag⁺ (Ag(NO₃) were prepared using millipore water and water from the Rhone river (Sion, Switzerland, Latitude: 46.228332, Longitude: 7.369975). About 10 mg of Fe-BTC or the composites were added to 20 mL of the solution and the vials were placed in a Thermo Scientific MaxQ4450 Orbital Shaker for 24 hours at 400 rpms and held at a constant temperature of 30° C. The samples were filtered using a 25 mm hydrophilic PTFE membrane syringe filter with 0.22 μm pores to remove any solids and elemental analysis was carried out on the remaining aqueous media after acidification.

Claims

1. A composite for extracting one or more metal or contaminating chemical species from an aerial or aqueous medium by selective binding, said composite comprising at least one porous template functionalized by at least one polymer, said polymer comprising one of the following chemical functions: primary, secondary or tertiary amine, amide, nitrile, pyridine, pyrrole, thiol, thiolether, thiophene, thiadiazole, alcohol/hydroxyl, phenol, catechol, pyragallol, carboxylic acid, aldehyde, ester, acyl, crown ether, phosphate, phosphoryl, epoxide, halogen, haloalkane.

2. A composite according to claim 1, wherein said at least one polymer is chosen among redox active polymers, peptides, biopolymer including polypeptides and polysaccharides, epoxy based polymer, fluoropolymer, acrylics, dedrimers, rubbers, inorganic polymers and organic polymers.

3. A composite according to claim 2, wherein said at least one polymer is chosen among redox active polymers.

4. A composite according to claim 3, wherein said redox active polymer is chosen among Poly(Tetracyanoquinodimethane) (PTCNQ), Poly(Viologens) Poly(Tetrathiafulvalene) (PTTF), Quinone Polymers, Polyhydroquinone (PHQ), Polydopamine (PDA), Polytyramine (PTA), Poly-para-phenylediamine (PpPDA), Poly(Vinylferrocene) (PVF or PVFc) (Organometallic Redox Polymer), Perfluorinated Sulfonic Acids (Nafion®), Poly(Styrene Sulfonate) (PSS), Poly(4-vinylpyridine) (PVP, QPVP), Polyaniline (PANI) and PANI Derivatives, Poly(1-aminoanthracene), Poly(o-toluidine), Poly(1,8-diaminonaphthalene) (PDAN), Poly(aniline-co-N-propanesulfonic acid-aniline), Poly(Diphenylamine) (PDPA), Poly(2-Aminodiphenylamine) (P2ADPA), Poly(o-Phenylenediam ine) (PPDA), Poly(o-Aminophenol) (POAP), Polyluminol (PL), Polypyrrole (PP) and PP Derivatives, Polyindole and Derivatives, Polymelatonin (PM), Polyindoline, Polycarbazoles (PCz), Polythiophene (PT) and PT Derivatives, Polyazines, Poly(1-Hydroxyphenazine) (PPhOH), Poly(Acridine Red) (PAR), Poly(Phenosafranin) (PPhS), Polyflavin (PFI), Poly(New Fuchsin) (PnF), Polyfluorene (PF), Poly(9-Fluorenone) (PFO), Poly (9,10-Dihydrophenanthrene), Poly(p-Phenylene) (PPP), Poly(Phenylenevinylene) (PPPV), Polytriphenylamine (PTPA), Poly(4-Vinyl-Triphenylamine) (PVTPA), Polyrhodanine (PRh), Poly (Eriochrome Black T), Poly(5-Amino-1,4-Naphthoquinone) (PANQ), Poly(5-Amino-1-Naphthol), Poly(4-Ferrocenylmethylidene-4H-Cyclopenta-[2,1-b;3,4-b⁰]-Dithiophene), Fullerene-Functionalized Poly(Terthiophenes) (PTTh-BB), Poly[Iron(4-(2-Pyrrol-1-Ylethyl)-4⁰-Methyl-2,2⁰-Bipyridine)₃ ²⁺], Polypyrrole Functionalized by Ru(bpy)(CO)₂, Poly(Tetra-Substituted Porphyrins), Poly(Tetra-Substituted Phtalocyanines),)Poly[4,4⁰(5⁰-Bis(3,4-Ethylenedioxy)Thien-2-Yl] Tetrathiafulvalene (PEDOT-TTF), Poly {3-[7-Oxa-8-(4-Tetrathiafulvalenyl) Octyl]-2,2⁰-Bithiophene} (PT-TTF), Poly(Aniline-co-Diaminodiphenyl Sulfone), Poly(Aniline-co-2/3-Amino or 2,5-Diamino Benzenesulfonic Acid), Poly(Aniline-co-o-Aminophenol), Poly(m-Toluidine-co-o-Phenylenediamine), Poly (Luminol-Aniline), polymer of 2,5-dihydroxy-1,4-benzenediacetic acid (PDHAA), poly-para-phenylenediamine (PpPDA) and polyhydroquinone (PHQ), preferably among polydopamine (PDA), poly-para-phenylenediamine (PpPDA), polyhydroquinone (PHQ), polymer of 1,4-benzenedithiol (PBDT), polytyramine (PTA) or polymer of 2,5-dihydroxy-1,4-benzenediacetic acid (PDHAA).

5. A composite according to claim 1, wherein said at least one porous template includes at least a metal.

6. A composite according to claim 5, wherein said at least one porous template is chosen among a metal-organic framework, a zeolite, carbons, a silica, an aerogel, a covalent organic framework, a porous polymer networks, a porous molecular solid, an hydrogel, a porous boron nitride, a porous graphene and a porous graphene oxide.

7. A composite according to claim 6, wherein said at least one porous template is chosen among a metal-organic framework, a zeolite, carbons, a silica, an aerogel, a covalent organic framework, a porous polymer networks, a porous molecular solid and an hydrogel.

8. A composite according to claim 7, wherein said at least one porous template is a metal organic framework.

9. A composite according to claim 8, wherein said metal organic framework comprises Fe-BTC, Cu-BTC, Cu-TDPAT or Al-BDC-NH₂, preferably Fe-BTC or Cu-BTC.

10. A composite according to claim 1, wherein said one or more metal or contaminating chemical species is chosen among: palladium, platinum, ruthenium, iridium, gold, silver, rhodium, cadmium, chromium, lead, mercury, arsenic, barium, fluoride, nitrates, nitrites, radium, selenium, sodium, radioactive (U, Th, Ra, Cs), lithium, magnesium, indium, gallium, germanium, tellurium, bismuth, rhenium, niobium, molybdenum, osmium, lanthanides, iron, cobalt, nickel, copper, zinc, ozone, chlorine gas, ammonia, hormones, dyes, volatile organic compounds, perchlorate and hydrocarbons (oil).

11. A composite according to claim 10, wherein said one or more metal or contaminating chemical specie is chosen among palladium, platinum, ruthenium, iridium, gold, silver, rhodium, cadmium, chromium, lead, mercury, arsenic, iron, cobalt, nickel and copper, preferably among precious metals such as palladium, platinum, ruthenium, iridium, gold, silver and rhodium.