Water decontamination via C

A method of removing a contaminant from water may include contacting contaminated water, including a heavy metal and/or an organic pollutant, with a nanocomposite including graphitic C3N4, MoO3, and MgAl2O4 in a mass relationship to each other in a range of from 5 to 15:2 to 7:75 to 95, thereby adsorbing the heavy metal and/or the organic pollutant onto the nanocomposite, as an adsorbed material. The method further includes removing the adsorbed material from the contaminated water, thereby reducing a concentration of the heavy metal in the contaminated water by at least 2 wt. %, the heavy metal includes Cd, Cr, Cu, Fe, Pb, Ni, Ag, Zn, and/or U, and the organic pollutant includes a dye.

BACKGROUND

Technical Field

The present disclosure is directed towards water decontamination techniques, and more particularly, towards a method of removing a contaminant from water using a nanocomposite including graphitic-C3N4, MoO3, and MgAl2O4.

Description of Related Art

The presence of both inorganic and organic pollutants in environmental systems has resulted in serious harm, often leading to disastrous consequences. Heavy metal ions are among the most concerning pollutants due to high toxicity, carcinogenic nature, and non-biodegradable characteristics of heavy metal ions. Currently, certain water bodies are significantly contaminated by heavy metals, which primarily result from anthropogenic activities, including chemical, textile, leather, plastic, mining, battery, paint and pigment, and paper and pulp industries. Common heavy metals found in industrial wastewater include, but are not limited to, cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), nickel (Ni), silver (Ag), zinc (Zn), and uranium (U). Among these, Cu is particularly prevalent in wastewater due to its extensive use in various engineering applications such as metal finishing, electroplating, and etching. A discharge of the aforementioned toxic metals into water streams and effluents without adequate treatment poses a severe threat to biotic systems. Through the food chain, heavy metals may accumulate in living organisms, potentially leading to severe health conditions such as cancer, nervous system damage, and kidney failure, and may ultimately be fatal at high concentrations. In response to this growing concern, various remediation techniques, such as ion exchange, precipitation, coagulation, membrane filtration, reverse osmosis, and adsorption, have been employed to remove toxic metal ions. Among these methods, adsorption is highly favored due to high removal efficiency, cost-effectiveness, and ability to target trace amounts of ions.

Graphite-phase carbon nitride (g-C3N4) has recently gained attention as a promising material for heavy metal removal due to certain desirable properties, including cost-effectiveness, metal-free n-type semiconductor nature, chemical and thermal stability, visible light responsiveness, and ease of preparation (see Singh, et al., Citric acid coated magnetic nanoparticles: synthesis, characterization and application in removal of Cd (II) ions from aqueous solution, J. Water Proc. Eng. 2014, 4, 233-241, which is incorporated by reference herein). However, g-C3N4 exhibits several drawbacks, such as low specific surface area, rapid electron-hole recombination, and challenging exfoliation. To overcome the above listed limitations, emphasis has been placed on modifying the microstructure and incorporating heteroatom doping. Infusing g-C3N4 nanosheets with metal nanoparticles may prevent the aggregation of g-C3N4 sheets, thereby enhancing the specific surface area and adsorption capacity. Various composites such as MgY2O4-g-C3N4, Ox-g-C3N4/Pani-NF, and CoFe2O4− g-C3N4 have been utilized for the removal of copper ions, whereas cadmium ion removal has been achieved using composites like CdS/g-C3N4, Y2O3@g-C3N4, and ZnO-g-C3N4. Furthermore, several studies have reported that incorporating metal oxides can enhance the pore volume and average pore size of the material, further improving adsorption efficiency (see Sharma, et al. In-situ synthesis of ZnO modified g-C3N4 composite: a potential photocatalyst and adsorbent for wastewater remediation, Mater. Res. Innov. 2022, 26(2), 65-75; Li, et al., Electrochemical hydrogen evolution reaction efficiently catalyzed by Ru—N coupling in defect-rich Ru/g-C3N4 nanosheets, J. Mater. Chem. 2021, 9(26), 15019-15026, each of which is incorporated by reference herein).

Despite the above suggested advancements, existing methods for heavy metal removal exhibit several limitations, including high operational costs, complex processing requirements, secondary waste generation, and limited efficiency at high concentrations of contaminants. Therefore, there is a requirement for development of advanced materials and techniques that may offer enhanced adsorption capabilities, improved reusability, and environmental sustainability.

Accordingly, one object of the present disclosure is to provide a method of water decontamination using carbon nanomaterials, that may circumvent the above specified drawbacks and limitation of the methods known in the art.

SUMMARY

In an exemplary embodiment, a method of removing a contaminant from water is described. The method includes contacting contaminated water, including a heavy metal and/or an organic pollutant, with a nanocomposite including graphitic C3N4, MoO3, and MgA2O4 in a mass relationship to each other in a range of from 5 to 15:2 to 7:75 to 95, thereby adsorbing the heavy metal and/or the organic pollutant onto the nanocomposite, as an adsorbed material. The method may include removing the adsorbed material from the contaminated water, thereby reducing a concentration of the heavy metal in the contaminated water by at least 2 wt. %, the heavy metal includes Cd, Cr, Cu, Fe, Pb, Ni, Ag, Zn, and/or U. The organic pollutant may include a dye.

The average pore distribution of the nanocomposite may be unimodal, and a (Brunauer-Emmett-Teller) BET specific surface area of the nanocomposite may be in a range of from 8 m2/g to 12 m2/g (e.g., ˜10.1 m2/g), and/or an average pore diameter of the nanocomposite, according to (Barrett-Joyner-Halenda) BJH measurement method, may be in a range of 5 to 15 nanometers (nm) (e.g., ˜8.34 nm), and/or an average pore volume of the nanocomposite, according to the BJH measurement method, may be in a range of from 0.01 cm3/g to 0.5 cm3/g (e.g., ˜0.033 cm3/g).

The nanocomposite may have a (311) spinel interplanar spacing in a range of 0.205 nm to 0.285 nm, (411) MoO3 interplanar spacing in a range of 0.150 nm to 0.230 nm, (511) spinel interplanar spacing in a range of 0.115 nm to 0.195 nm, (311) MgO interplanar spacing in a range of 0.087 nm to 0.167 nm, and/or (622) spinel interplanar spacing in a range of 0.080 nm to 0.160 nm, according to selected area diffraction (SAED).

The mass relationship of the nanocomposite may be in a range of from 9 to 11:4 to 6:84 to 86, where the nanocomposite may have a (311) spinel interplanar spacing of 0.245±2% nm, (411) MoO3 interplanar spacing of 0.19±2% nm, (511) spinel interplanar spacing of 0.155±2% nm, (311) MgO interplanar spacing of 0.127±2% nm, (622) spinel interplanar spacing of 0.12±2% nm, according to selected area diffraction. Further, an X-ray diffraction (XRD spectrum of the nanocomposite under Cu-filtered Cu-Kα radiation (1.5418 Å) powered at 45 kV and 10 mA may have 20 peaks of an MoO3 hexagonal phase at 18.7±1°, 28.7±1°, 33.0±1°, 33.8±1°, 36.8±1°, and/or 42.8±1°, an MgAl2O4 spinel phase at 19.3±1°, 36.8±1°, 44.6±1°, 59.3±1°, and/or 65.01±1°, an MgO cubic phase at 42.8±1°, 62.2±1°, and/or 74.6±1°, g-C3N4-related diffractions at 27.8±1°, 36.8±1°, 44.6±1°, and/or 59.3±1°. No more than 1% relative intensity, e.g., less than 0.5, 0.1, or 0.1% Al2O3 may be detected in the XRD spectrum.

The organic pollutant may be adsorbed and may include an indolinone sulfonate substructure (indigo carmine) in a mass ratio of 0.01 to 0.2 parts (e.g., ˜0.0982) of the organic molecules per part of the nanocomposite.

The nanocomposite obtained may include no MoS2 and/or no sulfide or metal sulfide, such as no added no MoS2 and/or no sulfide or metal sulfide.

The nanocomposite obtained may include less than 10 wt. % Co, relative to total nanocomposite weight.

The nanocomposite obtained may include less than 1 wt. % Co, relative to total nanocomposite weight.

The nanocomposite obtained may include no added Co. (only inevitable traces).

The nanocomposite obtained may include no more than 1 wt. % potassium.

The nanocomposite obtained may include no more than 1 wt. % iron.

The nanocomposite obtained may include no more than 1 wt. % zinc.

The nanocomposite obtained may include no more than 1 wt. % carbonaceous material besides the graphitic carbon nitride.

The nanocomposite may have a structure including a dispersion of homogeneous spherical metal oxides nanoparticles on a two-dimensional porous structure including curled and wrinkled nanosheets and platelets of the g-C3N4.

The above-described method may remove no more than 0.001 wt. % of uranium, based on total water weight.

In some embodiments, the nanocomposite preferentially adsorbs charged indigo-derivative dyes to radioactive metals.

In some embodiments, at least 70 mg per gram of nanocomposite are adsorbed from the water within 30 minutes of the contacting.

An average adsorption rate of the organic pollutant on the nanocomposite in the contacting may be in a range of from 3 milligrams per minute (mg/min) to 4 mg/min from an initiation of the contacting over 30 minutes.

The nanocomposite may adsorb specifically or preferentially organic dyes as the organic pollutant.

DETAILED DESCRIPTION

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.

As used herein, the term ‘room temperature’ refers to a temperature range of ′25 degrees Celsius (° C.)±3° C. in the present disclosure.

As used herein, the term ‘nanoparticles (NPs)’ refers to particles having a particle size of 1 nanometer (nm) to 500 nm within the scope of the present invention.

As used herein, the term ‘nanocomposite’ refers to a composite material that has at least one component with a grain size measured in nanometers.

As used herein, the term ‘nanohybrid composite’ refers to a material that combines nanomaterials (such as nanoparticles, nanotubes, or nanofibers) with another material, typically a polymer, metal, or ceramic, to form a composite structure. The nanomaterials are typically incorporated at the nanoscale level to enhance the properties of the base material, such as improving strength, conductivity, or flexibility, while maintaining the advantages of both components. The resulting nanohybrid composite exhibits unique properties that are superior to the individual materials alone.

As used herein, the term ‘porosity’ refers to a measure of the void or vacant spaces within a material.

As used herein, the term ‘pore diameter’ refers to an average width or size of the pores (void spaces) within a material, typically measured in nm or angstroms (Å). It is a key parameter in characterizing the texture and permeability of porous materials, influencing their adsorption, filtration, or catalytic properties. The pore diameter is often determined using methods such as nitrogen adsorption or mercury intrusion, which provide insights into the material's ability to absorb or interact with molecules of specific sizes.

As used herein, the term ‘pore volume’ refers to the total volume of void spaces (pores) within a material that is capable of being filled by a gas or liquid. It is typically expressed in cubic centimeters per gram (cm3/g) and is an important parameter in characterizing the porous structure of materials, such as adsorbents or catalysts.

As used herein, the term ‘photodegradation’ refers to the process by which a material undergoes chemical breakdown or alteration due to exposure to light. This process typically results in the breaking of molecular bonds within the material, leading to the formation of new compounds or the degradation of its physical and chemical properties.

As used herein, the term ‘contaminants’ refer to the harmful substances or contaminants that degrade the quality of water, air, soil, or food, making them unsafe or unsuitable for specific uses. In water, contaminants include biological agents like bacteria, viruses, and parasites; chemical substances such as heavy metals, pesticides, pharmaceuticals, and industrial chemicals; and physical materials like dirt, debris, and sediment. These contaminants can pose serious risks to human health, the environment, and ecosystems, depending on their type, concentration, and exposure levels.

As used herein, the term ‘organic contaminants’ refers to carbon-based compounds, typically derived from industrial, agricultural, or domestic activities, that are present as contaminants in water or the environment. These contaminants may include pesticides, pharmaceuticals, dyes, and other synthetic or natural organic substances that can pose environmental or health risks.

In some embodiments, the organic contaminant may be a dye, a phenol, a polycyclic aromatic hydrocarbon, an herbicide, a pesticide, a persistent organic contaminant, or the like.

A pesticide is a substance meant to prevent, destroy, or control pests including, but not limited to algae, bacteria, fungi, plants, insects, mites, snails, rodents, and viruses.

A pesticide intended for use against plants is known as an herbicide as described above.

A pesticide intended for use against mites is known as a miticide. Examples of miticides are permethrin, ivermectin, carbamate insecticides as described above, organophosphate insecticides as described above, dicofol, abamectin, chlorfenapyr, cypermethrin, etoxazole, hexythiazox, imidacloprid, propargite, and spirotetramat.

A pesticide intended for use against snails and other mollusks is known as a molluscicide. Examples of molluscicides are metaldehyde and methiocarb.

A pesticide intended for use against viruses is known as a virucide. Examples of virucides are cyanovirin-N, griffithsin, interferon, NVC-422, scytovirin, urumin, virkon, zonroz, and V-bind viricie.

A persistent organic contaminant is a toxic organic chemical that adversely affects human and environmental health, can be transported by wind and water, and can persist for years, decades, or centuries owing to resistance to environmental degradation by natural chemical, biological, or photolytic processes. Persistent organic contaminants are regulated by the United Nations Environment Programme 2001 Stockholm Convention on Persistent Organic Contaminants. Examples of persistent organic contaminants are Aldrin, chlordane, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, polychlorinated biphenyl (PCBs), dichlorodiphenyltrichloroethane (DDT), dioxins, polychlorinated dibenzofurans, chlordecone, hexachlorocyclohexane (α- and β-), hexabromodiphenyl ether, lindane, pentachlorobenzene, tetrabromodiphenyl ether, perfluorooctanesulfonic acid, endosulfans, and hexabromocyclododecane.

As used herein, the term ‘unimodal’ refers to a distribution or pattern that has a single peak or mode. In the context of particle size or material properties, it indicates that the sample consists of particles or components that are primarily of one size or characteristic, rather than varying widely in size or composition.

As used herein, the term ‘spinel interplanar spacing’ refers to the distance between parallel planes of atoms in the crystal structure of a spinel material. Spinel is a type of mineral with a specific crystalline arrangement, represented by the general formula AB2O4, where ‘A’ and ‘B’ are metal ions. The interplanar spacing is crucial for understanding the material's structural properties and is typically measured using X-ray diffraction (XRD) techniques.

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%.

The present disclosure is intended to include all hydration states of a given compound or formula, unless otherwise noted or when heating a material.

Aspect of the present disclosure is directed to a method of forming a nanocomposite of graphitic carbon nitride (g-C3N4), molybdenum oxide (MoO3), and magnesium aluminate (MgAl2O4) (g-C3N4@MoO3/MgAl2O4). Each component of the nanocomposite, when used in appropriate ratios, is effective in the removal of organic contaminants in water with high efficiency and removal activity.

A nanocomposite (g-C3N4@MoO3/MgAl2O4) including g-C3N4, MoO3, and MgAl2O4 is described. The nanocomposite includes a coating of g-C3N4 on MoO3 and MgAl2O4. The g-C3N4, MoO3, and MgAl2O4 are present in the nanocomposite in a mass relationship to each other in a range of from 5 to 15:2 to 7:75 to 95, preferably 7 to 13:3 to 6:80 to 90, and preferably 9 to 11:4 to 5:84 to 86. The g-C3N4, MoO3, and MgAl2O4 may be present in the nanocomposite in a mass relationship to each other of 10:5:85, while tolerable variations of any of these values may be 2.5, 2, 1.5, 1, 0.75, 0.5, 0.25, 0.1, 0.5, or 0.1. When each component of the nanocomposite is used in desired weight ratios, the nanocomposite exhibits excellent performance in photodegradation of organic pollutants owing to its enhanced catalytic properties, high surface reactivity, and efficient adsorption, making it suitable for applications in environmental remediation, energy production, and biomedical treatments.

The nanocomposite obtained may include no molybdenum sulfide (MoS2) and/or sulfide. The nanocomposite obtained may include no molybdenum sulfide (MoS2), or may exclude added MoS2, such as no detectable amounts thereof by, e.g., combustion analysis and/or spectroscopic analysis (e.g., UV-vis, fluorescence, XPS, IR, ESR, etc.). The nanocomposite obtained may include no sulfide, exclude added sulfide or metal sulfide, such as no detectable amounts thereof by, e.g., combustion analysis and/or spectroscopic analysis (e.g., UV-vis, fluorescence, XPS, IR, ESR, etc.). The nanocomposite obtained may include no sulfide, particularly no added Mo2S and/or sulfide. The nanocomposite may include no more than 0.1, 0.01, 0.001, or 0.0001 wt. % Mo2S and/or sulfide, e.g., no detectable Mo2S and/or sulfide, based on total nanocomposite weight.

The nanocomposite may be porous. A porous material is the one that forms a porous bulk solid. Pores may be micropores, mesopores, macropores, and/or a combination thereof. The pores exist in the bulk material, not necessarily in the molecular structure of the material. The term ‘microporous’ means that nanocomposite have pores with an average pore width (i.e. diameter) of less than 2 nm, e.g., in a range with an upper limit of 2, 1, 0.9, 0.75, 0.5, 0.25, 0.1, 0.05, or 0.01 nm, and/or a lower limit of 0.00001, 0.0001, 0.001, 0.01, 0.1, 0.25, 0.5, 0.75, or 1 nm. The term ‘mesoporous’ means the pores of the nanocomposite have an average pore width of 2 to 50 nm, though this may include subranges within this general range, e.g., a minimum diameter of 2, 3, 5, 10, 15, 20, 25, or 35 m, and/or a maximum diameter of 50, 45, 40, 35, 30, 25, 20, 15, or 10 nm. The term ‘macroporous’ means the pores of nanocomposite have an average pore width larger than 50 nm, e.g., at least 55, 75, 100, 250, 500, 750, or 1000 nm. Pore size may be determined by methods including, but not limited to, gas adsorption (e.g. N2 adsorption), mercury intrusion porosimetry, and imaging techniques such as scanning electron microscopy (SEM), and X-ray computed tomography (XRCT).

The Brunauer-Emmett-Teller (BET) surface area of the nanocomposite may be in a range of from 8 to 12 square meters per gram (m2/g), preferably 9 to 11 m2/g, and preferably 10 m2/g. The surface area on the nanocomposite may be 10.1±2.5, 2, 1.5, 1, 0.75, 0.5, 0.25, 0.2, or 0.1 m2/g. The BET hypothesis is the foundation for a significant analysis method for determining the specific surface area of a material. It attempts to explain the physical adsorption of gas molecules on a solid surface. Specific surface area is a property of solids, which is the total surface area of a material per unit of mass, solid or bulk volume, or cross-sectional area. Pore diameter, pore volume, and BET surface area may be measured by gas adsorption analysis, preferably N2 adsorption analysis (e.g., N2 adsorption isotherms).

The average pore distribution of the nanocomposite may include, but is not limited to, crystalline average pore distribution, bimodal, trimodal, multimodal, narrow, broad, and Gaussian. The average pore distribution of nanocomposite may be (only) unimodal, indicating a single dominant pore size within the material. This unimodal distribution suggests that the nanocomposites possess a relatively narrow pore size range, resulting in more uniform pore structures and enhancing specific properties such as adsorption capacity, catalytic activity, or surface reactivity.

The average pore diameter of the nanocomposite, according to Barrett-Joyner-Halenda (BJH) measurement method, may be in a range of from 5 to 15 nm, preferably 6 to 14 nm, preferably 7 to 13 nm, preferably 8 to 12 nm, and preferably 9 to 11 nm. The nanocomposite may have an average pore diameter of 8.34±2.5, 2, 1.5, 1, 0.5, 0.1, 0.05, 0.025, or 0.01 nm nm.

The average pore volume of the nanocomposite, according to the BJH measurement method, may be in a range of from 0.01 to 0.5 cm3/g, preferably 0.02 to 0.4 cm3/g, preferably 0.03 to 0.3 cm3/g, preferably 0.04 to 0.2 cm3/g, and preferably 0.05 to 0.1 cm3/g. The average pore volume of the nanocomposite may be 0.033 cm3/g±0.1, 0.05, 0.025, or 0.01 cm3/g.

The mass relationship of the nanocomposite may be in a range of from 9 to 11:4 to 6:84 to 86, and preferably 9.5 to 10.5:4.5 to 5.5:84.5 to 85.5. The mass relationship of the nanocomposite may be 10:5:85, wherein the ratios may vary by ±3, 2.5, 2, 1.5, 1, 0.5, 0.25, or 0.1.

The nanocomposite may have a (311) spinel interplanar spacing in a range of from 0.205 to 0.285 nm, preferably 0.215 to 0.275 nm, preferably 0.225 to 0.265 nm, and preferably 0.235 to 0.255 nm; (411) MoO3 interplanar spacing in a range of from 0.150 to 0.230 nm, preferably 0.160 to 0.220 nm, preferably 0.170 to 0.210 nm, and preferably 0.180 to 0.200 nm; (511) spinel interplanar spacing in a range of from 0.115 to 0.195 nm, preferably 0.125 to 0.185 nm, preferably 0.135 to 0.175 nm, and preferably 0.145 to 0.165 nm; (311) MgO interplanar spacing in a range of from 0.087 to 0.167 nm, preferably 0.097 to 0.157 nm, preferably 0.107 to 0.147 nm, and preferably 0.117 to 0.137 nm; and/or (622) spinel interplanar spacing in a range of from 0.080 to 0.160 nm, preferably 0.090 to 0.150 nm, preferably 0.100 to 0.140 nm, and preferably 0.110 to 0.130 nm, according to SAED.

The XRD spectrum of the nanocomposite under Cu-filtered CuKα radiation (1.5418 A) powered at 45 kilovolt (kV) and 10 milliampere (mA) may have 2θ peaks of an MoO3 hexagonal phase at 18.7±1°, 28.7±1°, 33.0±1°, 33.8±1°, 36.8±1°, and/or 42.8±1°, an MgAl2O4 spinel phase at 19.3±1°, 36.8±1°, 44.6±1°, 59.3±1°, and/or 65.0±1°; an MgO cubic phase at 42.8±1°, 62.2±1°, and/or 74.6±1°; and g-C3N4-related diffractions at 27.8±1°, 36.8±1°, 44.6±1°, and/or 59.3±1°. No more than 1% relative intensity Al2O3, e.g., less than 0.5, 0.25, 0.1, or 0.1%, may be detected in the XRD spectrum. The minimal presence of Al2O3 (less than 1%) in the nanocomposite is critical to maintaining its enhanced catalytic properties, high surface reactivity, and efficient adsorption. This may ensure desired performance in environmental remediation, energy production, and biomedical applications, free from interference by less reactive Al2O3 phases. The MoO3 in the nanocomposite may have a hexagonal crystal structure. In alternate embodiments, MoO3 may exist in other crystal phases including cubic, monoclinic, tetragonal, rhombohedral, and orthorhombic phases. The hexagonal phase of MoO3 may be represented by diffractions at 2.6 values of 18.7, 28.7, 33.0, 33.8, 36.8, and/or 42.8°. At 2θ values of 42.8, 62.2, and/or 74.6°, the cubic phase of MgO is detected. At 2θ values of 19.3, 36.8, 44.6, 59.3, and/or 65.01°, MgAl2O4 spinel is detected. At 2θ values of 27.8, 36.8, 44.6, and/or 59.3° g-C3N4-related diffractions is detected. MgAl2O4 may have a spinel phase, for example at least 95, 97.5, 99, 99.9%, or exclusively. The spinel phase is a mixed oxide with the general formula AB2O4, including one divalent cation (A2+) and two trivalent cations (B3+). The unit cell consists of a face-centered cubic arrangement of oxygen ions, containing 32 O2− ions, with 64 tetrahedral and 32 octahedral sites occupied by A2+ and B3+ cations. When one half of the octahedral interstices are occupied by B3+ cations and one-eighth of the tetrahedral sites are occupied by A2+ cations, the spinel phase is termed “normal.” Conversely, when tetrahedral sites are occupied by half of the B3+ and octahedral sites by the other half along with A2+, the spinel phase is termed “inverse.”

The spinel phase with the chemical formula MgAl2O4 is a mineral type of this oxide family. MgAl2O4 has been widely used in various applications, such as in metallurgical, electrochemical, radio-technical, and chemical industrial fields owing to its high thermal stability (melting point at 2135° C., high hardness (16 gigapascal (GPa)), high mechanical resistance, high resistance against chemical attack, wide band gap energy, high electrical resistivity, relatively low thermal expansion coefficient (9·10−6 m/m ° C.) between 3° and 1400° C., low dielectric constant, low density (3.58 gram per cubic centimeter (g/cm3)), high thermal shock resistance, hydrophobicity, and low surface acidity.

The nanocomposite may consist essentially of sheet morphologies, i.e., such that at least 98% of the adsorption capacity is retained relative to exclusive sheet morphology, preferably nanosheets, although other morphologies such as nanowires, nanospheres, nanocrystals, nanorectangles, nanotriangles, nanopentagons, nanohexagons, nanoprisms, nanodisks, nanocubes, nanoribbons, nanoblocks, nanotoroids, nanodiscs, nanobarrels, nanogranules, nanowhiskers, nanoflakes, nanofoils, nanopowders, nanoboxes, nanobeads, nanobelts, nano-urchins, nanoflowers, nanostars, tetrapods, and their mixtures thereof are also possible. Any of these may be excluded from the composition, however. The nanocomposite may have a structure including a dispersion of homogeneous spherical metal oxides nanoparticles on a two-dimensional porous structure including curled and wrinkled nanosheets and platelets of the g-C3N4.

A method 50 for removing contaminants from water is described. The order in which the method 50 is described is not intended to be construed as a limitation, and any number of the described method steps can be combined to implement the method 50. Additionally, individual steps may be removed or skipped from the method 50 without departing from the spirit and scope of the present disclosure.

At step 52, the method 50 includes contacting contaminated water, comprising a heavy metal and/or an organic pollutant, with the nanocomposite, thereby adsorbing the heavy metal and/or the organic pollutant onto the nanocomposite, as an adsorbed material. This interaction facilitates the adsorption of heavy metals and/or organic pollutants onto the nanocomposite. In some embodiments, the nanocomposite preferentially adsorbs charged indigo-derivative dyes to radioactive metals. The nanocomposite may adsorb organic dyes as the organic pollutant. The organic pollutant may be a dye, a phenol, a polycyclic aromatic hydrocarbon, an herbicide, a pesticide, a persistent organic contaminant, or the like. The removed dye may be indigo carmine dye. The dye or organic pollutant may also be decomposed by irradiation of the nanocomposite in its presence.

The organic pollutant may be adsorbed, e.g., as an indolinone sulfonate substructure (e.g., Indigo carmine), in a mass ratio of 0.01 to 0.2 parts, preferably 0.05 parts, preferably 0.1 parts, preferably 0.15 parts, preferably 0.2 parts, of the organic molecules per part of the nanocomposite. The organic pollutant adsorbed may include an indolinone sulfonate substructure (Indigo carmine) in a mass ratio of 0.0982 parts of the organic molecules per part of the nanocomposite.

The average adsorption rate of the organic pollutant on the nanocomposite may be in a range of from 3 to 4 mg/min, preferably 3.2 to 4 mg/min, preferably 3.6 to 4 mg/min, preferably 3.8 to 4 mg/min from an initiation of the contacting over 30 minutes. In some embodiment, at least 70 mg, preferably at least 75, at least 80 mg, at least 85 mg, at least 90 mg, at least 95 mg of the organic pollutant is adsorbed per gram of nanocomposite within 30 minutes of the contacting the organic pollutant with the nanocomposite. 98.2±5, 2.5, 2, 1.5, 1, 0.75, 0.5, 0.25, or 0.1 mg per gram of nanocomposite may be adsorbed from the water within 30 minutes of contacting the organic pollutant with the nanocomposite. The adsorption profile may be twice, thrice, 3.5-fold, etc., as fast over the first 30 minutes than over the subsequent 10 minutes, then again ½, ⅓, or ¼, etc., as fast over the subsequent 10 minutes.

The contaminant may be a heavy metal. Suitable examples of the heavy metals include, but are not limited to, Cd, Cr, Cu, Fe, Pb, Ni, Ag, Zn, and/or U. The heavy metal may be uranium. Contacting the contaminated water with the nanocomposite results in removal of no more than 0.001 wt. % of uranium, or other heavy metal(s), preferably no more than 0.0009 wt. % of uranium, preferably no more than 0.0008 wt. % of uranium, preferably no more than 0.0006 wt. % of uranium, preferably no more than 0.0005 wt. % of uranium, preferably no more than 0.0002 wt. % of uranium, based on total water weight.

At step 54, the method 50 includes removing the adsorbed material from the contaminated water, thereby reducing the concentration of the heavy metal in the contaminated water by at least 2 wt. %. The adsorbed materials may be separated from the contaminated water and reducing a concentration of the heavy metal in the contaminated water by at least 2 wt. %, preferably at least 2.5 wt. %, preferably at least 3 wt. %, preferably at least 3.5 wt. %, preferably at least 4 wt. %, preferably at least 5 wt. %.

According to the present disclosure, magnesium nitrate, and aluminum nitrate can be added together in one beaker with ammonium molybdate, in predetermined amount—e.g., stoichiometric, to produce a 10% MoO3/MgAl2O4. Further, about 10 g of menthol (e.g., 100:1 to 1:1, 25:1 to 1:1, or 10:1 to 1:1, by weight) as fuel was added to the beaker, followed by 30 milliliters (mL) of distilled water. The beaker was heated till a clear solution was obtained, heated further till dryness. The product was ground in a mortar, transferred to a 150 mL porcelain dish, and calcined at 700° C. for 3.0 hours (h). Furthermore, the 10% MoO3/MgAl2O4 product was cooled down to room temperature and weighed, ground with urea in an amount suitable (depending upon the reaction conditions, this may be 5, 10, 15, 20, 25, 33, 50, 100, 150, 250, 500, or 1000 parts by weight of urea to 100 parts by weight of 10% MoO3/MgAl2O4, and optionally no more than 100,000, 50,000, 25,000, 10,000, 5,000, 1,000, 750, 500, 400, 333, 250, 125, 100, 75, 50, or 25 parts by weight urea to 100 parts) to produce g-C3N4@MoO3/MgAl2O4 (10:5:85, wt. %) nanohybrid. The quadruple mixture was returned, and heated to 600° C. for 1.0 h in a covered porcelain crucible, and subsequently, the g-C3N4@MoO3/MgAl2O4 (10:5:85, wt. %) nanohybrid was collected.

X-ray diffraction (XRD) was used to identify the crystalline states in each specimen studied, employing the JDX-8030 X-ray (JEOL), made in Japan. Cu-filtered Cu-Kα radiation (1.5418 angstroms (Å)) powered at 45 kV and 10 mA was used to run the patterns. The specimens were tested at ambient temperatures in a range of 2θ=5° to 80°. The surface morphologies of the obtained samples were analyzed by transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) images, obtained using a Tecnai-G20 (USA) transmission electron microscope with a 200 kV speed voltage. Nitrogen (N2) adsorption isotherm obtained at 77 K using Micrometrics ASAP 2020 Brünauer-Emmett-Teller (BET) analyzer was used to calculate the surface characteristics, specifically the BET surface area, total pore volume (Vp), and mean pore radius (r). Before beginning the measurement, the samples were outgassed for three h at 200° C. with a decreased pressure of 10˜5 Torr.

XRD can be used to examine the crystallinity and phase identification of the g-C3N4@MoO3/MgAl2O4 catalyst. A high crystalline nature of the powders may be indicated by the strong peaks. MoO3, MgO, MgAl2O4, and g-C3N4 phases are detected when the diffraction patterns are compared to the normal JCPDS cards. The hexagonal phase of MoO3 is represented by diffractions at 2.6 values of 18.7°, 28.7°, 33.0°, 33.8°, 36.8°, and 42.8° (JCPDS No. 00-021-0569). At 20 values of 42.8°, 62.2°, and 74.6°, the cubic phase of MgO (JCPDS card, No. 45-0946) was detected. At 20 values of 19.3°, 36.8°, 44.6°, 59.3°, and 65.01°, MgAl2O4 spinel was discovered. The cubic phase of MgAl2O4 spinel is identified by these diffractions (JCPDS card, No. 21-1152). It was previously reported that MgO was present together with the MgAl2O4 spinel phase. The g-C3N4-related diffractions were detected at 27.8°, 36.8°, 44.6°, and 59.3°. The production of g-C3N4@MoO3/MgAl2O4 was shown by the absence of additional phases (such as Al2O3).

Further, TEM images of a g-C3N4@MoO3/MgAl2O4 within the claims shows the dispersion of homogeneous spherical metal oxides nanoparticles with size 9.4 nm on two-dimensional porous structure constructed with curled and wrinkled nanosheets and platelets of the g-C3N4. The corresponding SAED pattern reveals diffraction spots with interplanar spacing of 0.245 nm, 0.19 nm, 0.155 nm, 0.127 nm, 0.12 nm, due to (311, spinel), (411, MoO3), (511, spinel), (311, MgO), and (622, spinel) diffraction planes. The corresponding HRTEM of the composite shows a plane spacing of 0.34 nm related to the (002) of CN, where 0.25 nm and 0.24 nm relates to (311) planes of spinel as well as (410) of MoO3, and 0.32 nm relates to (210) plane of MoO3, characterizing the heterostructure formation, as shown in FIG. 3C. The fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) measurements show a d value of 0.35 nm given to g-C3N4@MoO3/MgAl2O4 nanocomposite, signifying the lattice spacing of (002), indicating the development of g-C3N4 structure.

The nitrogen sorption isotherm of the composite relates to type IV with clear hysteresis loop, indicating the formation of mesoporous structures. However, shifting the loop to a relatively lower pressure (P/P°=0.51 to 1) suggests a decrease in the size of the mesopores, which may result from the deposition of metal oxides particles in the wide pores of g-C3N4. Furthermore, the BET surface area of the g-C3N4@MoO3/MgAl2O4 sample was calculated to be 10.1 m2/g. The marked high specific surface area reflects the good dispersion of the aforementioned metal oxides nanoparticles on g-C3N4. Moreover, the pore size distribution curves, plotted using the BJH method, for the g-C3N4@MoO3/MgAl2O4 sample exhibited unimodal distribution with average pore diameters maximized at 8.34 nm and pore volume of 0.033 cm3/g. The isotherm belongs to the category H3 type of pores, which do not exhibit limiting adsorption at high P/P° and may arise due to aggregation of plate-like particles giving rise to slit-shaped pores. The aforementioned observation indicates that the assembly of g-C3N4@MoO3/MgAl2O4 composite provoked a mesoporous array.

The following 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.

EXAMPLES

The following examples demonstrate a method of removing contaminants from water using a nanocomposite. 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.

According to the present disclosure, magnesium nitrate, and aluminum nitrate were added together in one beaker with ammonium molybdate, in predetermined amount (here stoichiometric), to produce a 10% MoO3/MgAl2O4. Further, about 10 g of menthol as fuel was added to the beaker, followed by 30 mL of distilled water. The beaker was heated till a clear solution was obtained, heated further till dryness. The product was ground in a mortar, transferred to a 150 mL porcelain dish, and calcined at 700° C. for 3.0 hours. Furthermore, the 10% MoO3/MgAl2O4 product was cooled down to room temperature and weighed, ground with urea in an amount suitable (here, 2 g urea to 20 g of the 10% V2O5/MgAl2O4 product, but depending upon the reaction conditions, this may be 5, 10, 15, 20, 25, 33, 50, 100, 150, 250, 500, or 1000 parts by weight of urea to 100 parts by weight of 10% V2O5/MgAl2O4, and optionally no more than 100,000, 50,000, 25,000, 10,000, 5,000, 1,000, 750, 500, 400, 333, 250, 125, 100, 75, 50, 25, 20, 15, or 10 parts by weight urea to 100 parts) to produce g-C3N4@MoO3/MgAl2O4 (10:5:85, wt. %) nanohybrid/nanocomposite. The quadruple mixture was returned, and heated to 600° C. for 1.0 h in a covered porcelain crucible, and subsequently, the g-C3N4@MoO3/MgAl2O4 (10:5:85, wt. %) nanocomposite was collected.

Example 2: Characterization

According to the present disclosure, X-ray diffraction (XRD) was used to identify the crystalline states in each specimen studied, employing the JDX-8030 X-ray (JEOL), made in Japan. Cu-filtered Cu-Kα radiation (1.5418 Å) powered at 45 kV and 10 mA was used to run the patterns. The specimens were tested at ambient temperatures in a range of 2θ=5° to 80°. The surface morphologies of the obtained samples were analyzed by transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) images, obtained using a Tecnai-G20 (USA) transmission electron microscope with a 200 kV speed voltage. Nitrogen (N2) adsorption isotherm obtained at 77 K using Micrometrics ASAP 2020 Brünauer-Emmett-Teller (BET) analyzer was used to calculate the surface characteristics, specifically the BET surface area, total pore volume (Vp), and mean pore radius (r).

RESULTS AND DISCUSSION

As mentioned above, XRD was used to examine the crystallinity and phase identification of the g-C3N4@MoO3/MgAl2O4 catalyst, the results are depicted in FIG. 2. As can be seen from FIG. 2, high crystalline nature of the powders is indicated by the strong peaks. MoO3, MgO, MgAl2O4, and g-C3N4 phases are detected when the diffraction patterns are compared to the normal JCPDS cards. The hexagonal phase of MoO3 is represented by diffractions at 2.6 values of 18.7°, 28.7°, 33.0°, 33.8°, 36.8°, and 42.8° (JCPDS No. 00-021-0569). At 20 values of 42.8°, 62.2°, and 74.6°, the cubic phase of MgO (JCPDS card, No. 45-0946) was detected. At 2θ values of 19.3°, 36.8°, 44.6°, 59.3°, and 65.01°, MgAl2O4 spinel was discovered. The cubic phase of MgAl2O4 spinel is identified by these diffractions (JCPDS card, No. 21-1152). It was previously reported that MgO was present together with the MgAl2O4 spinel phase. The g-C3N4-related diffractions were detected at 27.8°, 36.8°, 44.6°, and 59.3°. The production of g-C3N4@MoO3/MgAl2O4 was shown by the absence of additional phases (such as Al2O3).

Further, TEM images of g-C3N4@MoO3/MgAl2O4 nanocomposite are shown in FIG. 3A. The TEM image shows the dispersion of homogeneous spherical metal oxides nanoparticles with size 9.4 nm on two-dimensional porous structure constructed with curled and wrinkled nanosheets and platelets of the g-C3N4. The corresponding SAED pattern reveals diffraction spots with interplanar spacing of 0.245 nm, 0.19 nm, 0.155 nm, 0.127 nm, 0.12 nm, due to (311, spinel), (411, MoO3), (511, spinel), (311, MgO), and (622, spinel) diffraction planes, as shown in FIG. 3B. The corresponding HRTEM of the composite shows a plane spacing of 0.34 nm related to the (002) of CN, where 0.25 nm and 0.24 nm relates to (311) planes of spinel as well as (410) of MoO3, and 0.32 nm relates to (210) plane of MoO3, characterizing the heterostructure formation, as shown in FIG. 3C. The fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) measurements show a ‘d’ value of 0.35 nm given to g-C3N4@MoO3/MgAl2O4 nanocomposite, signifying the lattice spacing of (002), indicating the development of g-C3N4 structure, as shown in FIGS. 3D-3E.

According to the present disclosure, FIGS. 4A to 4B shows the nitrogen adsorption-desorption isotherms of g-C3N4@MoO3/MgAl2O4 nanocomposite. The nitrogen sorption isotherm of the composite relates to type IV with clear hysteresis loop, indicating the formation of mesoporous structures. However, shifting the loop to a relatively lower pressure (P/P°=0.51 to 1) suggests a decrease in the size of the mesopores, which may result from the deposition of metal oxides particles in the wide pores of g-C3N4. Furthermore, the BET surface area of the g-C3N4@MoO3/MgAl2O4 sample was calculated to be 10.1 m2/g. The marked high specific surface area reflects the good dispersion of the aforementioned metal oxides nanoparticles on g-C3N4. Moreover, the pore size distribution curves, plotted using the BJH method, for the g-C3N4@MoO3/MgAl2O4 sample exhibited unimodal distribution with average pore diameters maximized at 8.34 nm and pore volume of 0.033 cm3/g. The isotherm belongs to the category H3 type of pores, which do not exhibit limiting adsorption at high P/P° and may arise due to aggregation of plate-like particles giving rise to slit-shaped pores. The aforementioned observation indicates that the assembly of g-C3N4@MoO3/MgAl2O4 composite provoked a mesoporous array.

An accurate mass of 50 mg of the g-C3N4@MoO3/MgAl2O4 was transferred to a 120 mL beaker to which 100 mL of 50 mg/L indigo carmine dye was added, and an aliquot was picked at serial time intervals till about 2.0 hours. The portion of the solution was filtered through a 0.22 m syringe filter, and the absorbance of the dye in the solution was measured with a ultraviolet visible (UV-vis) spectrophotometer, as shown in FIG. 5. The measured absorbance was employed to compute the sorption capacity of the nanohybrid, which reached about 98.2 mg indigo carmine per 1.0 gram of the g-C3N4@MoO3/MgAl2O4.