Patent Application
20240424475
The present disclosure is directed to a zeolite composite, more particularly to a graphene oxide-zeolitic imidazolate framework-based nanocomposite and a method for its use for water decontamination.
The description of the related prior art provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
An upsurge in industrialization has led to a severe global challenge of water contamination by heavy metals. Lead (Pb2+) is one of the most toxic heavy metals since it is highly carcinogenic, non-biodegradable, and tends to bioaccumulate and biomagnify in the ecosystem. Lead usually finds applications in paints, smelting, manufacture of batteries, paper, as well as pulp industries. The lead discharge occurs from different sources such as paint industries, leaded gasoline, and mining sources along with battery manufacturing plants. The leakage of inorganic lead from these sources into water bodies is a prime cause of lead contamination. The permissible limit of lead in drinking water has been set up at 0.05 mg L−1 by the World health organization (WHO). Acute Pb poisoning in human beings may lead to critical damage to the kidneys, liver, and reproductive system. Pb poisoning from environmental exposure also causes headaches, anemia, insomnia, dizziness, irritability, muscle weakness, and hallucination, apart from renal damage. In humans, Pb absorption primarily starts from the lungs and the digestive tract and then circulates in the bloodstream. Thereafter, Pb binding with blood cells takes place, and finally, Pb gets accumulated in the bones.
It is important to eliminate heavy metal ions from contaminated wastewater for the safety of aquatic life and human beings. To address this challenge, various methods have been developed for the removal of contaminants viz., coagulation, ion exchange, chemical precipitation, electrochemical methods, reverse osmosis, and membrane processes [Mahmud, H. N. M. E., Huq, A. O., & binti Yahya, R. (2016). The removal of heavy metal ions from wastewater/aqueous solution using polypyrrole-based adsorbents: a review. RSC Advances, 6(18), 14778-14791]. However, most of these techniques suffer from crucial shortcomings, such as high capital and operational costs, inadequate efficiency at usual discharge levels, and the occurrence of secondary pollution. As opposed to the above limitations, adsorption has come across as a valuable alternative owing to the low cost of adsorbent materials, lower working costs, feasible operational conditions, high efficacy for dilute solutions, and easy handling. Furthermore, adsorption is normally reversible, thus the adsorbents can be simply regenerated via an appropriate desorption method. Furthermore, lead removal via graphene oxide-based nanomaterials is also an appealing option accrediting its favorable properties.
Accordingly, an object of the present disclosure is to develop a nanocomposite of graphene oxide and a metal-organic framework. The nanocomposite has a high lead adsorption capacity at relatively low dosages of adsorbent and can effectively be used as an alternative to conventional adsorbents.
In an exemplary embodiment, a nanocomposite is described. The nanocomposite includes graphene oxide, a zeolitic imidazolate framework (ZIF), wherein the zeolitic imidazolate framework has a phase I, II, or III structure.
In some embodiments, the zeolitic imidazolate framework is ZIF-7.
In some embodiments, the zeolitic imidazolate framework has a phase III structure.
In some embodiments, the graphene oxide is less than 5 wt. % of the total mass of the nanocomposite.
In some embodiments, the graphene oxide is about 1.6 wt. % of the total mass of the nanocomposite.
In some embodiments, the nanocomposite has an average particle size of less than 500 nanometers (nm).
In some embodiments, the graphene oxide has an average particle size of less than 100 nm.
In some embodiments, the nanocomposite has a Pb2+ ion uptake capacity ranging from 900 milligrams per liter (mg/L) to 5,000 mg/L, where the Pb2+ ion uptake capacity is calculated according to:
In some embodiments, the zeolitic imidazolate framework encases the graphene oxide.
In some embodiments, a method for producing a graphene oxide-zeolitic imidazolate framework nanocomposite includes dissolving an amount of a hydrated zinc nitrate salt in methanol to produce a first solution; adding graphene oxide to the first solution to produce a second solution; adding benzimidazole dissolved in methanol to the second solution to produce a third solution; and heating the third solution at a temperature greater than 100° C. to form the graphene oxide-zeolitic imidazolate framework nanocomposite.
In some embodiments, the amount of graphene oxide added to the first solution is less than 5 wt. % relative to a combined mass of the amount of hydrated zinc nitrate and the amount of benzimidazole.
In some embodiments, the amount of graphene oxide added to the first solution is about 1.6 wt. % relative to a combined mass of the amount of hydrated zinc nitrate and the amount of benzimidazole.
In some embodiments, the graphene oxide-zeolitic imidazolate framework nanocomposite was dried at 50° C.
In some embodiments, the method includes heating the third solution to a temperature of 130° C.
In some embodiments, the method includes heating the third solution for at least 24 hours.
In an exemplary embodiment, a water filtration composition, including the graphene oxide-zeolitic imidazolate framework nanocomposite, is described.
In an exemplary embodiment, a method for removing metal ions from water is described. The method includes mixing an amount of the graphene oxide-zeolitic imidazolate framework nanocomposite to a sample of water comprising one or more metal ions to form a solution; removing the one or more metal ions from the sample of water by adsorbing the one or more metal ions onto the graphene oxide-zeolitic imidazolate framework nanocomposite; and recovering the graphene oxide-zeolitic imidazolate framework nanocomposite.
In some embodiments, one or more metal ions include lead.
In some embodiments, the solution containing nanocomposite and metal ion solution is mixed for at least 24 hours.
In some embodiments, the amount of graphene oxide-zeolitic imidazolate framework nanocomposite has a Pb2+ ion uptake capacity ranging from 900 mg/L to 5,000 mg/L, where the Pb2+ ion uptake capacity is calculated according to:
The foregoing general description of the illustrative embodiments and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.
A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.
Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable, in that some, but not all embodiments of the disclosure are shown.
In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words “a,” “an” and the like generally carry a meaning of “one or more,” unless stated otherwise.
Furthermore, the terms “approximately”, “approximate”, “about,” and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.
The use of the terms “include,” “includes”, “including,” “have,” “has,” or “having” should be generally understood as open-ended and non-limiting unless specifically stated otherwise.
As used herein, “particle size” may be thought of as the length or longest dimension of a particle.
As used herein, “nanocomposites” are solid materials that have multiple phase domains, and at least one of these domains has a nanoscale structure. The nanoparticles may exist in various morphological shapes, such as nanowires, nanocrystals, nanorectangles, nanotriangles, nanopentagons, nanohexagons, nanoprisms, nanodisks, nanocubes, nanoribbons, nanoblocks, nanobeads, nanotoroids, nanodiscs, nanobarrels, nanogranules, nanowhiskers, nanoflakes, nanofoils, nanopowders, nanoboxes, nanostars, tetrapods, nanobelts, nano-urchins, nanofloweres, etc., and mixtures thereof.
As used herein, “adsorption capacity” refers to the amount of adsorbate taken up by the adsorbent per unit mass (or volume) of the adsorbent.
A weight percent of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. For example, if a particular element or component in a composition or article is said to have 5 wt %, it is understood that this percentage is in relation to a total compositional percentage of 100%.
Aspects of the present disclosure are directed to a graphene oxide-zeolitic imidazolate framework-based nanocomposite (GO@ZIF-7) or herein referred to as a “nanocomposite”. The nanocomposite was characterized by various analytical techniques, such as X-ray diffractogram (XRD) and Fourier Transform Infrared (FTIR); and was further evaluated for its potential in water decontamination applications. The nanocomposite of the present disclosure demonstrated a high lead removal at relatively low dosages of the adsorbent (i.e., GO@ZIF-7 nanocomposite). The process used herein to prepare the nanocomposite is effective at ambient conditions with minimal energy input and with no additional material inputs. The GO@ZIF-7 nanocomposite outperforms the pristine GO and ZIF-7 in terms of its performance for lead removal.
A nanocomposite is described. The nanocomposite includes graphene oxide and a zeolitic imidazolate framework (ZIF). Graphene oxide (GO) is a single-atomic-layered material, made by the oxidation of graphite, which is cheap, abundant, and widely used as an adsorbent in various water purification technologies. GO is an oxidized form of graphene, with an average particle size of less than 100 nm. It is laced with high concentrations of functional groups, such as the hydroxyl (C—OH), epoxyl (—O—), carboxylate (—COOH), or other oxygen-containing groups, at the edges and on the face of the GO nanosheets. The polar oxygen functional groups of GO render it hydrophilic so that it can be dispersible in water (and other solvents). In an embodiment, the GO has a weight percentage in a range of 0.5-5%, preferably 0.75 to 4.5 wt. %, preferably 1 to 4 wt. %, preferably 1.3 to 3.5 wt. %, preferably 1.5 to 3 wt. %, preferably 1.6 to 2 wt. %, preferably 1.6 wt. % based on the total mass of the nanocomposite.
ZIF on the other hand, is a class of metal-organic frameworks (MOFs) that are topologically isomorphic with zeolites. ZIFs are composed of tetrahedrally-coordinated transition metal ions (e.g., Fe, Co, Cu, Zn) connected by imidazolate linkers. Various ZIF's are known in the art, such as ZIF-1, ZIF-3, ZIF-7, ZIF-8, ZIF-9, ZIF-11, and ZIF-67. The ZIF may exist in various phases, such as phase I, phase II, phase III, and/or combinations thereof. In a preferred embodiment, the ZIF exists in phase III. The ZIF is preferably ZIF-7. The ZIF, preferably ZIF-7 is modified with GO in such a way that the ZIF encases the GO, to form the nanocomposite (GO@ZIF-7).
The ZIF may fully or partially encase the graphene oxide, e.g., the graphene oxide forms one or more layers inside the GIF. Preferably a major portion of the surface area of the GO is covered or encased with the ZIF. For example, at least 80% of the surface area of the GO is encased in or covered with ZIF, preferably at least 90%, at least 95% or the total surface area of the GO. The GO-ZIF nanocomposite may be represented as a core-shell structure in which the core is GO and the shell is ZIF. In some embodiments a portion of the GO protrude from or extends outside of a ZIF matrix. A GO functionalized with ionic or polar groups such as carboxylate groups, hydroxyl groups and/or epoxy groups may help direct metal ions to the surface of the surrounding ZIF for adsorption and/or sequestration out of an aqueous solution.
The nanocomposite has an average particle size of less than 500 nm, preferably in the range of 10-500, preferably 20-490, preferably 25-480, preferably 30-470, preferably 40-460, preferably 50-450, preferably 60-440, preferably 70-430, preferably 80-420, preferably 90-410, preferably 100-400, preferably 110-390, preferably 120-380, preferably 130-370, preferably 140-360, preferably 150-350, preferably 160-340, preferably 170-330, preferably 180-320, preferably 190-310, preferably 200-300, preferably 210-290, preferably 220-280, preferably 230-270, preferably 240-280, preferably 250-270, and preferably 255-260 nm.
At step 52, the method 50 includes dissolving an amount of a hydrated zinc nitrate salt in methanol to produce a first solution. Suitable examples of hydrated zinc salts include zinc sulfate heptahydrate (ZnSO4·7H2O), zinc nitrate hexahydrate (Zn(NO3)2·6H2O), zinc acetate dihydrate (Zn(CH3CO2)2), zinc oxalate dihydrate (ZnC2O4·2H2O), zinc acetylacetonate hydrate Zn(C5H7O2)2·xH2O. In an embodiment, the hydrated zinc salt is Zn(NO3)2·6H2O. In an embodiment, the hydrated zinc salt is a nitrate salt. In an embodiment, the hydrated zinc salt is Zn(NO3)2·6H2O. In an embodiment, the concentration of the hydrated zinc salt in methanol is in a range of 0.1-0.3 g/mL, preferably 0.12 to 0.2 g/mL/, preferably 0.1485 g/mL. In an embodiment, other solvents, such as N, N-dimethylformamide (DMF), N-dimethylformamide (DEF), butanol, and the like, can be used as well instead of/in combination with methanol to produce the first solution.
At step 54, the method 50 includes adding graphene oxide to the first solution to produce a second solution. The weight ratio of the graphene oxide to the hydrated zinc salt in the first solution is in a range of 1:30 to 1:15, preferably 1:28 to 1:17, preferably 1:20 to 1:25. After the addition of the graphene oxide to the first solution, the first solution was stirred thoroughly to ensure uniform dissolution of the graphene oxide in the second solution. In an embodiment, the stirring was carried out using a stirrer for a period of 2-30 minutes, preferably 4-15 minutes, preferably 5-10 minutes, preferably 5 minutes, at room temperature (20-30° C.) to form the second solution. The graphene oxide in the second solution may be further exfoliated to produce single and multiple layers of graphene oxide by sonication. The sonication may be carried out using a probe sonicator (preferably) or an ultrasonic bath. Critical factors affecting the exfoliation process are the sonication time and power. In an embodiment, the second solution is sonicated with 50% amplitude for 10-60 minutes, preferably 20-50 minutes, preferably 30-40 minutes, and preferably 30 minutes.
At step 56, the method 50 includes adding benzimidazole dissolved in methanol to the second solution to produce a third solution. In an embodiment, the amount of graphene oxide added to the first solution is less than 5 wt. %, preferably 1-5 wt. %, preferably 1.2 to 4 wt. %, preferably 1.4 to 3 wt. %, preferably 1.5 to 2 wt. %, preferably 1.6 wt. % relative to a combined mass of the amount of hydrated zinc nitrate and the amount of benzimidazole.
At step 58, the method 50 includes heating the third solution at a temperature greater than 100° C. to form the graphene oxide-zeolitic imidazolate framework nanocomposite. In a specific embodiment, the third solution is heated to a temperature of 100-150° C., preferably 110-140° C., preferably 120-130° C., and more preferably 130° C. In a specific embodiment, the third solution is heated for 12-48 hours, preferably 15-40 hours, preferably 20-35 hours, preferably 24 hours, to form the graphene oxide-zeolitic imidazolate framework nanocomposite. The nanocomposite thus formed may be washed several times with an organic solvent, preferably methanol, to remove any impurities. The washed nanocomposite is further dried at 40-50° C. to allow for evaporation of the solvent. The drying may be carried out using heating appliances such as ovens, microwaves, autoclaves, hot plates, heating mantles and tapes, oil baths, salt baths, sand baths, air baths, hot-tube furnaces, and hot-air guns. The nanocomposite is further ground to a fine powder to reduce its particle size. The particle size may be reduced by ball milling, grinding, pressure homogenization, or a combination thereof. The small particle size of the nanocomposite imparts a high surface area and increased pore volume, resulting in an improved adsorptive capacity of the nanocomposite towards heavy metals, such as lead, when used for water purification applications.
In an embodiment, nanocomposites may be immobilized on a supporting material or substrate, such as, but not limited to, silica. The resultant supported composite is used for the removal of heavy metal waste from water. Suitable examples of supporting material include alumina, zeolites, activated carbon, cellulose fibers, coconut fibers, clay, banana silks, nylon, coconut shell, and a combination thereof.
Another aspect of the present disclosure relates to water filtration composition. The water filtration composition includes the GO@ZIF-7 nanocomposite. In an embodiment, metals/metal oxides thereof that can be incorporated into the water filtration composition include, without limitation, gold, silver, platinum, palladium, cobalt, manganese, iron, tellurium, rhodium, ruthenium, copper, iridium, molybdenum, chromium, cerium, or a combination thereof.
The nanocomposite of the present disclosure can be used for removing heavy metals from water. Examples of heavy metals include but are not limited to, lead (Pb(II)) and manganese (Mn(II)), copper (Cu(II)), nickel (Ni(II)), cadmium (Cd(II)) and mercury (Hg(II)). In a preferred embodiment, the nanocomposite is used to remove lead from water. Suitable examples of water sources can be any groundwater source, an industrial source, a municipal source, and/or a combination thereof.
At step 62, the method 60 includes mixing an amount of the GO@ZIF-7 nanocomposite to a sample of water comprising one or more metal ions to form a solution. The water may include metal ions, such as lead (Pb(II)) and manganese (Mn(II)), copper (Cu(II)), nickel (Ni(II)), cadmium (Cd(II)), and mercury (Hg(II)). In a preferred embodiment, the nanocomposite is particularly effective for the removal of lead from water. The pH of the water is about 2-10, preferably 4-7.
At step 64, the method 60 includes removing one or more metal ions from the sample of water by adsorbing the one or more metal ions onto the GO@ZIF-7 nanocomposite. The nanocomposite is made to contact the water containing one or more metal ions for a sufficient period, such as 1 hour to 24 hours, to allow for adsorption of the metal ions to the nanocomposite. In some embodiments, the nanocomposite removes at least 50%, preferably at least 60%, preferably at least 70%, more preferably at least 80%, or more preferably at least 90%, or more preferably at least 95% of the metal ions in the water.
At step 66, method 60 includes recovering the GO@ZIF-7 nanocomposite. The nanocomposite with the metal ions adsorbed onto it is separated from water via filtration or any other methods known in the art. The metal ions are further adsorbed onto the nanocomposite are desorbed via thermal or solvent desorption techniques to recover the nanocomposite. In an embodiment, the recovered nanocomposite can be used multiple times without compromising on the efficiency for up to 5-20 cycles.
The nanocomposite of the present disclosure has a Pb2+ ion uptake capacity ranging from 900 mg/L to 5,000 mg/L, where the Pb2+ ion uptake capacity is calculated according to:
where Ci and Cf are, respectively, an initial and a final lead concentrations, V is the sample volume, and m is the amount of graphene oxide-zeolitic imidazolate framework nanocomposite.
The following examples demonstrate a graphene oxide-zeolitic imidazolate framework-based nanocomposite as described herein. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.
GO was prepared according to the improved Hummers method [Marcano, D. C., Kosynkin, D. V, Berlin, J. M., Sinitskii, A., Sun, Z., Slesarev, A., Alemany, L. B., Lu, W., & Tour, J. M. (2010). Improved Synthesis of Graphene Oxide. ACS Nano, 4(8), 4806-4814—incorporated herein by reference]. Briefly, 360 mL of H2SO4 and 40 mL of H3PO4 (H2SO4:H3PO4 volumetric ratio=9:1) were carefully mixed in a flask. To regulate the temperature, the flask was placed in an ice bath. Then, 3 g of graphite powder was added to the above mixture, followed by the slow addition of 18 g KMnO4 while continuously stirring. The reaction mixture was then transferred to a warm water bath and stirred for 12 h at 50° C. After that, the reaction mixture was poured into about 400 g of crushed ice, followed by the slow addition of H2O2 (˜5 mL) until the mixture color turned dark yellow. Then, the mixture was stirred continuously for 12 h at room temperature. The mixture was, then, washed consecutively with distilled water and HCl (10 vol %) solution three times each, and the solid was recovered after each wash cycle by centrifugation at 8000 rpm. After this step, GO was further rinsed several times with a copious amount of distilled water to remove the acid. Finally, the obtained GO was dried at 50° C. and ground to produce fine powders.
The preparation of ZIF-7 was according to the protocol reported by Yaghi group, with some modifications [Morris, W., He, N., Ray, K. G., Klonowski, P., Furukawa, H., Daniels, I. N., Houndonougbo, Y. A., Asta, M., Yaghi, O. M., & Laird, B. B. (2012). A Combined Experimental-Computational Study on the Effect of Topology on Carbon Dioxide Adsorption in Zeolitic Imidazolate Frameworks. The Journal of Physical Chemistry C, 116(45), 24084-24090—incorporated herein by reference]. In this preparation, 5.94 g of Zn(NO3)2·6H2O was added to 40 mL HPLC grade methanol. In a separate beaker, 9.44 g benzimidazole was added to 40 mL high-performance liquid chromatography (HPLC) grade methanol. The two solutions were then stirred at room temperature until the solid materials (Zn(NO3)2·6H2O and benzimidazole) were completely dissolved. After that, the zinc solution was poured quickly into the benzimidazole solution while stirring for 1 h at room temperature. The mixture was then transferred into a Teflon-lined autoclave reactor and kept in an oven at 130° C. for 24 h. Then, the autoclave reactor was removed from the oven and left to cool down naturally. Following that, the formed ZIF-7 powder was purified via several washes with HPLC-grade methanol; the solid ZIF-7 material was recovered after each wash using centrifugation at 6000 rpm. The purified ZIF-7 was then dried at 50° C. The dried ZIF-7 powder was ground to obtain a fine powder. The ZIF-7 powder was stored in tightly closed containers until use.
To prepare GO@ZIF-7 nanocomposite, 5.94 g Zn(NO3)2·6H2O was added to 40 mL HPLC grade methanol, followed by stirring until the zinc salt was completely dissolved. Then, 0.25 g GO was added to the above solution and stirred at room temperature for 5 min to disperse GO. After that, the GO dispersion was sonicated at 50% amplitude for 30 min (30 seconds pulse on/3 seconds off) using a probe sonicator. The remaining preparation steps are similar to those described in Example 2. The synthesized samples are characterized by various analytical techniques, and they were further evaluated for their potential in water decontamination.
The Fourier Transform Infrared (FTIR) spectra of GO@ZIF-7 nanocomposite, ZIF-7, and GO and is shown in
The ZIF-7 spectra shown in
The adsorption performance of GO@ZIF-7 was compared to those of GO and ZIF-7. In these experiments, the adsorbent dosage, sample volume, adsorption time, and shaking speed were fixed at 100 mg/L, 100 mL, 24 h, and 250 rpm, respectively. Two lead concentrations (100 and 500 mg/L) were prepared using distilled water and utilized in these experiments to measure the lead uptake capacity by the above 3 adsorbents. The uptake capacity (qe) was calculated using the following equation:
Where Ci and Cf are, respectively, the initial and final (after 24 h) lead concentrations, V is the sample volume, and m is the adsorbent mass.
The adsorption of lead on GO, ZIF-7, and GO@ZIF-7 nanocomposite is shown in
Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
