WO2019081536A1 - Coating-free cobalt metal nanoparticles for heavy metal extraction from water - Google Patents

Coating-free cobalt metal nanoparticles for heavy metal extraction from water

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Publication number
WO2019081536A1
WO2019081536A1 PCT/EP2018/079071 EP2018079071W WO2019081536A1 WO 2019081536 A1 WO2019081536 A1 WO 2019081536A1 EP 2018079071 W EP2018079071 W EP 2018079071W WO 2019081536 A1 WO2019081536 A1 WO 2019081536A1
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Prior art keywords
coating
metal nanoparticles
nanoparticles
cobalt metal
free cobalt
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PCT/EP2018/079071
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French (fr)
Inventor
Erwan Rauwel
Protima Rauwel
Ülis SÕUKAND
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Pro-1 Nanosolution Oü
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Publication of WO2019081536A1 publication Critical patent/WO2019081536A1/en

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    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/28Treatment of water, waste water, or sewage by sorption
    • C02F1/281Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/28Treatment of water, waste water, or sewage by sorption
    • C02F1/288Treatment of water, waste water, or sewage by sorption using composite sorbents, e.g. coated, impregnated, multi-layered
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
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    • B01J20/28004Sorbent size or size distribution, e.g. particle size
    • B01J20/28007Sorbent size or size distribution, e.g. particle size with size in the range 1-100 nanometers, e.g. nanosized particles, nanofibers, nanotubes, nanowires or the like
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    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28002Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
    • B01J20/28009Magnetic properties
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J20/00Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28026Particles within, immobilised, dispersed, entrapped in or on a matrix, e.g. a resin
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    • B01J20/00Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30Processes for preparing, regenerating, or reactivating
    • B01J20/32Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3202Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J20/00Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30Processes for preparing, regenerating, or reactivating
    • B01J20/32Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3202Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
    • B01J20/3206Organic carriers, supports or substrates
    • B01J20/3208Polymeric carriers, supports or substrates
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J20/30Processes for preparing, regenerating, or reactivating
    • B01J20/32Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B01J20/3234Inorganic material layers
    • B01J20/3236Inorganic material layers containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts
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    • B01J20/30Processes for preparing, regenerating, or reactivating
    • B01J20/32Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3291Characterised by the shape of the carrier, the coating or the obtained coated product
    • B01J20/3293Coatings on a core, the core being particle or fiber shaped, e.g. encapsulated particles, coated fibers
    • BPERFORMING OPERATIONS; TRANSPORTING
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    • B01J20/30Processes for preparing, regenerating, or reactivating
    • B01J20/32Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
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    • B01J20/3295Coatings made of particles, nanoparticles, fibers, nanofibers
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/001Processes for the treatment of water whereby the filtration technique is of importance
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/48Treatment of water, waste water, or sewage with magnetic or electric fields
    • C02F1/488Treatment of water, waste water, or sewage with magnetic or electric fields for separation of magnetic materials, e.g. magnetic flocculation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/28Treatment of water, waste water, or sewage by sorption
    • C02F1/283Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/28Treatment of water, waste water, or sewage by sorption
    • C02F1/285Treatment of water, waste water, or sewage by sorption using synthetic organic sorbents
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/10Inorganic compounds
    • C02F2101/20Heavy metals or heavy metal compounds

Abstract

A process for the extraction of heavy metal ions from water comprising: i. mixing coating-free cobalt metal nanoparticles in contaminated water; and ii. waiting at least 5 seconds for heavy metal ions agglomerating around the coating-free cobalt metal nanoparticles, and iii. extracting the cobalt metal nanoparticles coated with the heavy metal ions in the metallic or oxide form from the contaminated water.

Description

COATING-FREE COBALT METAL NANOPARTICLES FOR HEAVY METAL EXTRACTION FROM WATER
Technical field
This invention relates to a process in which coating-free cobalt metal nanoparticles and more particularly coating-free (or surfactant-free) cobalt metal nanoparticles are used as medium for the extraction of heavy metal ions in solution and more particularly in water.
Background of invention
In the scientific paper Industrial & Engineering Chemistry Research, Vol. 49, 2010, Michael Rossier et al., "Energy-Efficient Noble Metal Recovery by the Use of Acid- Stable Nanomagnets", pages 9355-9362 the authors describe the synthesis and study of metal-based carbon coated magnetic nanoparticles used for the efficient extraction of gold and platinum at high dilution (milligram to gram per ton = ppb to ppm) at a mini- pilot level (0.1 m3). Acid-stable nanomagnets were first prepared by reducing flame synthesis and consisted of graphene-like carbon-coated cobalt metal nanoparticles (20-40 nm diameter) with an onion-like core/ shell structure. The use of a metal core affords high saturation magnetization, while carbon shells are highly resistant to most chemical conditions. The nanomagnet surface was further coated with a standard noble metal extraction resin-like polymer. In summary the cobalt nanoparticles are covered with carbon, which make them a completely different nanomaterial that the one we describes in present patent application. The document is then not relevant.
In report published in Journal of Nanoparticle Research, Vol. 16, 2014, Pipsa Mattila et al., "Scalable synthesis and functionalization of cobalt nanoparticles for versatile magnetic separation and metal adsorption", pages 1 -1 1 are described scalable synthesis and functionalization of cobalt nanoparticles for versatile magnetic separation and metal adsorption where magnetic cobalt nanoparticles coated/covered with a carbon shell and oxidized group are on the surface of the carbon. The cobalt is not the active material and the cobalt nanoparticles are the vehicle that will transport the contaminant extract by the carbon shell covered by oxidized species. The authors in article are disclosing the preparation of magnetic cobalt nanoparticles protected with a thin carbon shell by means of an easily scalable method. The carbonaceous protective layer effectively prevents cobalt leakage in neutral aqueous solutions thus the cobalt is not directly in contact to the aqueous method. In patent application WO 2013/008019 A1 (UNIVERSITY OF BRISTOL) the authors are describing a composite layer on a surface of the substrate in which the composite layer comprises nanoparticles comprising a first metal, a first metal oxide or a combination thereof; and a layer comprising a second metal, second metal oxide or combination thereof between the nanoparticles on the surface of the substrate.
In the patent application WO 2016/014505 A1 (CORNING) is described a method making an activated carbon support comprising a transition metal based nanoparticles. This method consists of the impregnation of the activated carbon with at least one transition metal containing compound followed by heating the activated carbon under inert atmosphere. Disclosed is a method of synthesis and the utilization of the materials synthesized through this method for water purification application.
US 2014/0042068 A1 (NAMIKI) describes a magnetic composite particles for decontamination, method for fabricating the same, radioactive substance family decontamination system, and radioactive substance family decontamination method. The invention relates to a magnetic composite particle for the decontamination and a method for fabricating the same. The magnetic composite if a multilayer structure that includes a magnetic core portion, a trapping compound formed in a surface layer, an intermediate layer that covers the magnetic core.
The cobalt metal nanoparticles when introduced into heavy metal contaminated water, promote the agglomeration of heavy metal ions in the form of metallic cluster or metal oxide clusters. Metal nanoparticles are an increasingly emerging industrial material that is now integrated in multiple applications. Due to their high surface area and very high reactivity, metal nanoparticles are used in a variety of applications, many of which arise from the improved behaviour and properties of nanomaterials. In fact, metallic nanoparticles with diameter ranging from 2 to 10Onm have received extensive attention in particular applications such as catalysis, biosensors, optical filters, biomedical applications, antibacterial coating, targeted drug delivery and cancer therapy. The synthesis of hybrid materials like carbon-based nanocomposite combining carbon nanotubes and nanoparticles or metal hydrides has spurred a lot of interest due to the synergetic effect of these nanocomposites.
By nanoparticles and nanomaterials one implies a size below 1 micrometer: typically below 500nm and generally above 3nm. Due to the industrial development and human population growth, the natural resources are decreasing. In addition, the discharge of industrial effluents and generation of pollution caused by increase in human population further contaminates most of the water resources by organic pollutants, microorganisms and heavy metal ions release. Contaminated water regroups general water resources like lakes, rivers, ground water, phreatic zone, seas. The main issue is to clean that contaminated water, but some contamination remains and the contamination by heavy metal ions is one of the most difficult contamination to eliminate from water. This contamination can be found in tape water, well water, but can also be present in water after industrial catastrophes like Minamata and Bhopal for mercury contamination or Fukushima and Chernobyl for radioactive elements contamination.
Many processes already involve nanoparticles for water purification, for example carbon based nanomaterials, graphene nanocomposites combining inorganic and organic moieties, layered double hydroxide nanomaterials etc. Graphene nanocomposites have demonstrated superior performance in the removal of heavy metal. However, their performance at industrial scale limits their application due to the high cost of maintenance, energy consumption and high sludge generation. In addition, the utilization of graphene oxide requires toxicity tests before their application in real wastewater systems. Layered double hydroxide nanomaterials have also been studied for water remediation. These nanomaterials have an enormous potential and exhibit higher anion exchange capacity. However, due to structural unsteadiness under low pH and high cost for regeneration; high scale use appears difficult to apply in the case of these nanomaterials.
Many methods are presently available like coagulation, flocculation, ion exchange, membrane filtration, bioremediation, adsorption, oxidation (catalysis) etc. However, the major disadvantages of these present methods are the handling and disposal problem due to the sludge production, the high cost for most of them and the technical constraints that have not yet been solved, more specifically in the case of heavy metal and radio elements removal. The continuous discharge of environmental pollutant is imposing to develop new and effective treatments and removal process and very recently many efforts have been made to develop magnetic nanosorbent for the separation of pollutants that can be easily recycled. However, most of these methods are not cost effective and scaling up these processes appears challenging. In addition, the absorption capacities of heavy metal for most of these methods are around 40 to 89mg/g, which remains a limitation to their efficiency.
In view of such problems as extracting heavy metal ions from liquid and more particularly from water, there is a need for the development of sustainable, simple, reliable and low cost methods. This method should enable the direct extraction of heavy metal from water with possibilities of recycling the extracted heavy metal without harming the environment. Cost effective treatment poses a challenge for environmental engineers, in particular for highly toxic and persistent pollutants difficult to treat. New water treatment approaches that are more cost effective than available techniques are under investigation and from all these studies, technologies involving nanomaterials appear as the most promising solutions.
During the last decade, due to their magnetic properties, high chemical stability and low toxicity and recycling capability, hierarchically structured magnetic nanoparticles like Fe nanoparticles functionalized multi-walled carbon nanotubes or citric acid coated magnetic nanoparticles, have attracted a lot of attention. They have been more particularly studied for toxic metal ions and organic pollutant removal due to higher removal capacities with lower contact time than the bulk material. As mentioned before, the nanopartide size should be below the critical limit to exhibit superparamagnetic properties. However, these magnetic nanoparticles are subjected to atmospheric conditions and are easily oxidized in open air and water: usually they need to be coated or functionalized in order to stabilize the magnetic nanoparticles in extreme environmental conditions. In addition, the synthesis of magnetic nanoparticles is a costly complex process due to their colloidal nature and high activity. One of the most popular example are SPIONs (superparamagnetic iron oxide (Fe3O4) nanoparticles) that exhibit very good magnetic saturation value (84 emu/g) demonstrating a strong magnetic responsivity easily separable from aqueous solutions using an external magnetic field. These superparamagnetic nanoparticles have, for example, been tested for Ni2+ ions extraction.
Co element appears to be well tolerated in the human body and for example is administered in the supplementation of vitamin B12 and in the case of anemia. Contrary to iron element, the human body can easily eliminate the excess of cobalt element via urinals system and cobalt element is known as non-accumulating metal. In addition, cobalt levels go down once the source of cobalt is removed. A recent study c
5
has shown that cobalt concentration ranging between 9.4 and 1 17 g/L in the blood system was not associated with clinically significant changes in basic hematologic and clinical variables (Tvermoes et al., Am. J. Clin. Nutr., Vol. 99(3), p632-646 (2014)), which makes cobalt element a possible suitable element for water purification. Summary of invention
In one aspect, the present invention provides a process for the extraction of heavy metal ions that can be present in water and more particularly polluted water comprising: i. mixing coating-free cobalt metal nanoparticles in water; and ii. waiting the necessary time for heavy metal ion agglomerating around the coating-free cobalt metal nanoparticles, and iii. Extracting the cobalt metal nanoparticles coated with the heavy metal ions in the metallic or metal oxide form from the water.
Preferably the process of the invention uses coating-free cobalt metal nanoparticles stable under air (figure 1 ). The term "coating-free" instead of term "surfactant-free" is appropriate term because it refers to any kind of coating, i.e. metal, organics, surfactant, stabilizers, carbon, polymers. The cobalt metal nanoparticles preferably exhibit superparamagnetic properties to enable their extraction from the liquid medium using magnetic field.
After the reaction process between the cobalt metal nanoparticles and the heavy metal ions 50% of the quantity of the heavy metal ions have been extracted, preferably from 50 to 80%, more preferably 60 to 90% and most preferably 70 to 100%.
The coating-free cobalt metal nanoparticles are preferably coated with one layer of oxygen or hydroxyl group or the coating-free cobalt metal nanoparticles are preferably coated with one monolayer of oxygen or hydroxyl group. The nanomaterials used for the extraction of heavy metal ions can be metal nanoparticles or a mixture of different metal nanoparticles decorating the surface of the superparamagnetic coating-free cobalt metal nanoparticles. The coating-free cobalt nanoparticles used for the extraction of heavy metal ions can be agglomerated which decreases possible toxicity and Co ion release in the treated solution. The coating-free cobalt metal nanoparticles can also be anchored or bonded via a chemical bonding on a support material or a substrate like sand (figure 2), activated carbon, metallic support, carbon nanotubes, graphene, alumina phases, glass, polymers but not limited to. In that case, the support material or substrate can be integrated in a filter.
The cobalt metal nanoparticles can also be integrated in a filter as active material. In that case, the polluted water flow goes through the filter and the process may further comprise: i. Passing the polluted water on the support material / substrate covered by coating-free cobalt metal nanoparticles. ii. Heavy metal ions are agglomerating around the coating-free cobalt metal nanoparticles anchored on the support material / substrate. iii. Recuperation of the cleaned water at the exit of the filter iv. Removing from the filter when necessary, the support material / substrate covered by cobalt nanoparticles coated by heavy metal in the metallic form or oxide form.
In one embodiment of the invention the active material is coating-free cobalt metal nanoparticles that are stable under air. The process comprises two possible ways for extracting the heavy metal ions from polluted water. The first way consists in spreading the coating-free cobalt metal nanoparticles in the polluted water and waiting sufficiently long in order to agglomerate all the heavy ions on the surface of the cobalt metal nanoparticles and then proceed to the extraction of the superparamagnetic cobalt nanoparticles covered by heavy metals in the metallic form or oxide form. The second way consists of using a filter that comprises a material support covered by coating-free cobalt metal nanoparticles on its surface through which water is passed. The heavy metal ions present in the water interact with the coating-free cobalt metal nanoparticles and agglomerate on the surface of the coating-free cobalt metal nanoparticles in the metallic form or oxide form. Decontaminated water, without heavy metal is then obtained after the utilization of such a filter. After the reaction process between the coating-free cobalt metal nanoparticles and heavy metal ions, 50% of the quantity of the heavy metal ions have been extracted, preferably from 50 to 80%, 15 more preferably 60 to 90% and most preferably 70 to 100%. In another aspect, the invention provides water that does not contain heavy metal ions after having used coating-free cobalt metal nanoparticles for the extraction of heavy metal ions via their agglomeration on the surface of the cobalt nanoparticles. In any case, the quantity of heavy metals in the water after extraction using Co based composites respects the individual water norms. In a further aspect, the invention provides water that either does not contain heavy metal ions after having used the filter or contains heavy metals in acceptable amounts. The filter here integrates a support materials covered with coating-free cobalt metal nanoparticles for the extraction of heavy metal ions via their growth or agglomeration on the surface of the coating-free cobalt nanoparticles.
In another aspect, the extracted cobalt metal nanoparticles covered by heavy metal in the metallic form or oxide form can be recycled in a high temperature oven to induce the separation of the different metals for reutilization.
Brief description of drawings
Figure 1 shows HRTEM images of coating-free cobalt metal nanoparticles that exhibit a cubic structure.
Figure 2 shows optical microscope image of sand covered with Co nanoparticles before reaction with water containing heavy metal ions.
Figure 3 shows X-ray diffraction (XRD) patterns show of coating-free Co metal nanoparticles with cubic structure.
Figure 4 shows SEM image of coating-free Co metal nanoparticles covered by metallic lead after reaction in a water solution containing lead ions. Figure 5 shows SEM image of coating-free Co metal nanoparticles lead before reaction in a water solution containing heavy metal ions.
Figure 6 shows SEM image of Ag-Co nanocomposite before reaction in a water solution containing heavy metal ions.
Figure 7 shows SEM image of Ag-Co nanocomposite after reaction in a water solution containing lead ions.
Figure 8 shows SEM image of sand covered with coating-free Co metal nanoparticles covered by metallic iron after reaction in a water solution containing iron ions.
Figure 9 shows SEM image and Si, Fe and Co mapping of sand covered with coating- free Co metal nanoparticles after reaction in a water solution containing iron ions. Figure 10 shows a photograph of water containing 34 ppm of iron ions before (Erlenmeyer on left side) and after purification (Erlenmeyer right side). o
Figure 1 1 shows a photograph of water containing 4 ppm of iron ions before (Erlenmeyer on left side) and after purification (Erlenmeyer right side).
Detailed Embodiment
The present invention provides a process for the extraction of heavy metal ions that can be present in water and more particularly polluted water. The process includes the utilization of coating-free cobalt metal nanoparticles (figure 1 ). Coating-free cobalt metal nanoparticles are preferred. Cobalt metal nanoparticles stable under air are preferred. The structure of the cobalt metal nanoparticles is cubic (Figure 3), but it is also possible to use cobalt metal nanoparticles with a hexagonal crystal structure. These metal nanoparticles can be coated with a layer of oxygen, and preferably one layer of hydroxyl group on their surface or one monolayer of hydroxyl group on their surface. The coating-free cobalt metal nanoparticles preferably exhibit superparamagnetic properties to enable their easy extraction from the liquid medium using magnetic field. The invention provides a process for the extraction of heavy metal ions that can be present in water and more particularly polluted water comprising: i. Mixing coating-free cobalt nanoparticles in water; and ii. Waiting the necessary time for heavy metal ion agglomerating around the coating-free cobalt metal nanoparticles, and iii. Extracting the cobalt metal nanoparticles coated with the heavy metal ions in the metallic or metal oxide form from the water.
In that process, the coating-free cobalt metal nanoparticles preferably exhibit superparamagnetic properties to enable their extraction from the liquid medium using magnetic field. The process of the invention can be applied essentially on water containing heavy metal ions. This process can also be applied to other liquid solution or gas medium that contains heavy metal ions.
In the process of the invention the heavy metal ions present in the solution or in the gas are interacting with the coating-free cobalt metal nanoparticles and attached on the surface of the nanoparticles. The interaction induces the growth of heavy metal structure on the surface of the coating-free cobalt metal nanoparticles. The heavy metal structure that grows on the surface of the coating-free cobalt metal nanoparticles can be in the metallic or oxide form. Figure 4 shows lead ions that grew in the metallic form on the surface of the cobalt metal nanoparticles after reaction in water.
The metal nanoparticles suitable for this process include coating-free cobalt metal nanoparticles. These coating-free cobalt nanoparticles can be used as sole active material for the extraction of heavy metal ions. The coating-free cobalt nanoparticles used for the extraction of heavy metal ions can be agglomerated preferably through hydrogen bonding which decreases possible toxicity and release in the treated solution (figure 5). Coating-free cobalt metal nanoparticles can also be combined with other metal nanoparticles. The other metal nanoparticles combined with the coating-free cobalt nanoparticles can be silver metal nanoparticles, copper metal nanoparticles, gold nanoparticles, platinum nanoparticles, but not limited to. Preferably the metal nanoparticles that will be combined with the coating-free cobalt metal nanoparticles are grown on the surface of the coating-free cobalt metal nanoparticles (figure 6).
The coating-free cobalt metal nanoparticles can be grown or spread on a material support (substrate) that will be used for filtering. The coating-free cobalt metal nanoparticles are then bonded on the support via a chemical bonding that anchored them on the surface of the materials support. The said substrate is covered by coating- free cobalt metal nanoparticles or by coating-free cobalt metal nanoparticles combined with other materials like other metal nanoparticles or polymer. The support material covered by the coating-free cobalt metal nanoparticles can be sand (figure 2), wood, cellulose, metallic fibres, porous ceramic, polymer, glass but not limited to.
The invention is a process that enables to extract heavy metal ions that contaminate a liquid like water or are present in gas like gas combustion exhaust. The process consists of introducing the metal nanoparticles in the liquid medium or gas and waiting sufficiently long to enable the heavy metal ions to react with the coating-free cobalt metal nanoparticles and form a metallic or oxide coating through the extraction of pollutant. The time necessary for the reaction is preferably 1 -60 minutes, for example 4-50 minutes, 5-30 minutes, preferably at around 5 minutes in the case of a liquid medium. The reaction with a gas medium is faster and preferably 1 -60 seconds, for example 4-50 seconds, 5-30 seconds, preferably at around 5 seconds.
The reaction process between the cobalt metal nanoparticles and the heavy metal ions occurs in the temperature range of 1 to 100 °C, preferably 10 to 80 °C, more preferably 15-40 °C and most preferably 15-30 °C. The reaction process between the coating-free cobalt metal nanoparticles and the heavy metal ions occurs in a liquid medium at a pH range of 1 to 14, preferably 3 to 10, more preferably 15 4 to 9 and most preferably 6 to 8.
Preferred heavy metal ions that will be extracted by the invention are: V, Cr, Mn, Fe, Ni, Cu, Zn, As, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, Ra, U, Pu
Heavy metal ions that will be extracted by the invention:
Ti, Ga, Ge, As, Y, Zr, Nb, Tc, Ru, Te, La, Hf, Ta, W, Re, Os, At, Ac, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, Cn, Nh, Fl, Mc, Lv, Ts, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa, Np, Am, Cm, Bk
The coating-free cobalt metal nanoparticles can also be integrated in a filter as the active material. In that case, the polluted water flow or contaminated gas goes through the filter and the said method comprises: i. Passing the polluted water or polluted gas on the support material or substrate covered by coating-free cobalt metal nanoparticles. ii. Heavy metal ions are agglomerating around the coating-free cobalt metal nanoparticles anchored on the support material or substrate. iii. Recuperation of the cleaned water or gas at the exit of the filter or exhaust. iv. Removing from the filter when necessary, the support material or substrate covered by cobalt nanoparticles coated by heavy metal in the metallic or oxide form.
The coating-free cobalt metal nanoparticles coating may cover at least 50% of the surface of the substrate, for example at least 60%, 70%, 80% of the surface of the substrate. Preferably the coating will cover at least 90% of the surface of the substrate, for example at least 95%, 98% or 100% of the substrate surface.
In another aspect the coating of coating-free cobalt metal nanoparticles may consist of discrete metal nanoparticles or aggregates of metal nanoparticles. The nanoparticles typically have diameters in the range of 1 -4000 nm, preferably 2-500 nm, more preferably 3-200 nanometers. The metal nanoparticle aggregates typically have an overall diameter in the range 50-500 nm, for example they may be approximately 100, 200, 300 or 400 nm in diameter. After the reaction, the materials support decorated with coating-free cobalt metal nanoparticles coated with heavy metal in the form of metallic of oxide film or coating (figure 4) oxide is removed from the filter for recycling via high temperature gradient treatment. Extraction of heavy metal from polluted water has been performed using both methods. The direct introduction of coating-free cobalt metal nanoparticles in a solution containing lead ions (Pb2+) during 5 minutes and the extraction of the superparamagnetic cobalt nanoparticles coated with lead in metallic form using a magnetic field of at least 0.2 Tesla, preferably ranging from 0.5 to ITesla (Example 1 ). The filtration of a solution containing copper ions (Cu2+) using sand coated with coating-free cobalt metal nanoparticles has been performed. The filter consisted of one essay tube of 15ml cut at its extremity and filled with active materials (sand decorated with coating-free cobalt metal nanoparticles) and to avoid the escape from the sand, net in polyethylene has been stretched at the bottom of the tube and glued with silicon (example).
All XRD patterns were produced using Cu-alpha radiation. Examples
The ions contents in examples 1 -4 have been measured by inductively coupled plasma mass spectrometer Agilent Technologies 7700x. The ions content in examples 5-8 have been measured by a multiparameter photometer Hanna Instruments HI83300 capable of providing Cu concentration in ppm.
Example 1
A solution of water contaminated with lead ions has been prepared. 1 .0031 g of Pb(NO3) has been dissolved in 100 ml of distilled water to 5 obtain a concentration of 6500 ppm of lead ion (Pb2+) in the water solution. The pH of the solution after preparation is pH = 4.24. 15ml of contaminated water has been transferred in one essay tube of 15ml and 6mg of coating-free Co metal nanoparticles have been added to the water containing lead ion. The solution has been shaked manually for 5 minutes. A magnet has been used to fix the superparamagnetic cobalt nanoparticles on the surface of the tube and the purified solution has been transferred in another essay tube of 15ml. A lead content of 6500ppm has then been measured. After the purification 5300ppm of lead ions has been measured indicating a decrease of 1200ppm of lead ions with the introduction of 536ppm of Co nanoparticles. The ratio of extraction is 2.24 ppm of Pb2+ for 1 ppm of Co metal nanoparticles. An increase of the pH of the solution after purification has been observed. The pH before extraction was 4.24 and after extraction the pH value is 6.02. Figure 5 is a SEM image of the cobalt nanoparticles before being used for lead extraction. Figure 4 is a SEM image of the cobalt nanoparticles after being used for lead extraction showing a modification of the surface morphology and the growth of Pb microsheets on the surface of the agglomerated Co nanoparticles.
Example 2 The solution of water contaminated with lead ions prepared in example 1 that contains 6500ppm of Pb2+ has been treated with 6mg of coating-free Co metal nanoparticles decorated with Ag nanoparticles of 10 nm (Ag-Co nanocomposite). 15ml of contaminated water has been transferred in one essay tube of 15ml and 6mg of coating-free Ag-Co nanocomposite have been added to the water containing lead ion. The solution has been shaken manually for 5 minutes. A magnet has been used to fix the superparamagnetic Ag-Co nanocomposite on the surface of the tube and the purified solution has been transferred in another essay tube of 15ml. The lead content has then been measured. After the purification 5700ppm of lead ions has been measured indicating a decrease of 800ppm of lead ions. An increase of the pH of the solution after purification has been observed. The pH before extraction was 4.24 and after extraction the pH is 5.27. Figure 6 is a SEM image of the Ag-Co nanocomposite before being used for lead extraction.
Example 3
The solution containing 6500 ppm of lead ions (Pb2+) prepared in example 1 has been used and diluted 10Otimes. 1 ml of water containing 6500ppm of Pb2+ has been mixed with 99ml_ of distilled water to prepare a solution containing 65ppm of lead ions. 15ml of contaminated water has been transferred in one essay tube of 15ml and 6mg of coating-free Co metal nanoparticles decorated with Ag nanoparticles of 10 nm (Ag-Co nanocomposite) (Figure 6) have been added to the water containing 65ppm of lead ions. The solution has been shaken manually for 5 minutes. A magnet has been used to fix the superparamagnetic Ag-Co nanocomposite on the surface of the tube and the purified solution has been transferred in another essay tube of 15ml. The lead content has then been measured. After the purification, 28ppb of lead ions has been measured indicating a decrease of 99,95% of lead content with the introduction of 560ppm of Ag- Co nanocomposite. Figure 7 is a SEM image of the Ag-Co nanocomposite after being used for lead extraction showing a modification of the surface morphology and the growth of Pb microsheets on the surface of the agglomerated nanocomposite. Example 4
15ml of tap water from our laboratory containing heavy metal ions like Mn, Ni, Pb, V and Cu has been transferred in a 15ml essay tube. 3.5mg of coating-free cobalt metal nanoparticles have been added to the water containing and then the tube has been shaken manually for 5 minutes. A magnet has been used to fix the superparamagnetic cobalt nanoparticles on the surface of the tube and the purified solution has been transferred in another essay tube of 15ml. The pH before extraction was 7.07 and after extraction the pH is 7.58. The heavy metal ions have been measured before and after the purification process and a clear decrease of heavy metal ion concentration in the water has been observed:
Figure imgf000014_0001
Example 5
15ml of well water from Estonia countryside and containing manganese (Mn) has been transferred in a 15ml essay tube. 2.3mg of coating-free cobalt metal nanoparticles have been added to the water containing and then the tube has been shaken manually for 5 minutes. A magnet has been used to fix the superparamagnetic cobalt nanoparticles on the surface of the tube and the purified solution has been transferred in another essay tube of 15ml. The manganese has been measured before and after the purification process and a clear decrease of Mn content has been observed. The Mn content decreased from 210ppb before extraction to 5.9ppb after the purification process. The pH before extraction was 7.47 and after extraction the pH is 8.00. Example 6
Coating-free cobalt metal nanoparticles have been spread on the surface of cleaned sand (Trixie Basissand Art. Nr. 76131 ) that has been used as material support (figure 2). The sand has been transferred in an essay tube of 15ml cut at its extremity and sealed with polyester net to allow the water to go through the sand in the tube and is then collected in a beaker. A 200 ml_ solution containing 22 ppm of Copper ions has been passed through the system containing sand coated with cobalt metal nanoparticles. The copper content in the water collected after the filtering process was 7.3ppm. The colour of the solution changed from translucent blue to a more translucent blue
Example 7
Coating-free cobalt metal nanoparticles have been spread on the surface of cleaned sand (Trixie Basissand Art. Nr. 76131 ) that has been used as material support (figure 2). The sand has been transferred in an essay tube of 15ml cut at its extremity and sealed with polyester net to let the water going through the sand in the tube and being collected in a beaker. A 1 L solution containing 7.32 ppm of Zn ions has been passed through the system containing sand coated with cobalt metal nanoparticles. The zinc content in the water collected after the filtering process was 2.66 ppm. The colour of the solution changed from translucent to colourless-translucent.
Example 8
Coating-free cobalt metal nanoparticles have been spread on the surface of sand (Trixie Basissand Art. Nr. 76131 ) that has been used as material support (figure 2). The sand has been transferred in an essay tube of 15ml cut at its extremity and sealed with polyester net to let the water going through the sand in the tube and being collected in a beaker. A 300 ml_ solution containing 34 ppm of Fe ions has been passed through the system containing sand coated with cobalt metal nanoparticles. The Fe content in the water collected after the filtering process was 0.8 ppm. After reaction, the iron ions have reacted and agglomerated on the surface of the sand coated with Co metal nanoparticles (Figure 8 and 9). The colour of the solution changed from yellow to colourless (figure 10). The pH before extraction was 2 and after extraction the pH is 5.9.
Example 9
Coating-free cobalt metal nanoparticles have been spread on the surface of sand (Trixie Basissand Art. Nr. 76131 ) that has been used as material support (figure 2). The sand has been transferred in an essay tube of 20 ml_ cut at its extremity and sealed with polyester net to let the water going through the sand in the tube and being collected in a beaker. A 15 ml_ solution containing 65 ppm of Pb ions has been passed c
Ί θ
through the system containing sand coated with cobalt metal nanoparticles. The Pb content in the water collected after the filtering process was 1 .2ppb. After reaction, the lead ions have reacted and agglomerated on the surface of the sand coated with Co metal nanoparticles. The pH before extraction was 4.24 and after extraction the pH is 6.2.
Example 10
Coating-free cobalt metal nanoparticles have been spread on the surface of sand (Trixie Basissand Art. Nr. 76131 ) that has been used as material support (figure 2). The sand has been transferred in an essay tube of 20mL cut at its extremity and sealed with polyester net to let the water going through the sand in the tube and being collected in a beaker. A 15ml_ solution containing 4ppm of Mn ions has been passed through the system containing sand coated with cobalt metal nanoparticles. The Mn content in the water collected after the filtering process was lower than 0.2ppb. After reaction, the manganese ions have reacted and agglomerated on the surface of the sand coated with Co metal nanoparticles. The colour of the solution changed from magenta to transparent (Figure 1 1 ).
Example 1 1
Coating-free cobalt metal nanoparticles have been spread on the surface of sand (Trixie Basissand Art. Nr. 76131 ) that has been used as material support (figure 2). The sand has been transferred in an essay tube of 20ml_ cut at its extremity and sealed with polyester net to let the water going through the sand in the tube and being collected in a beaker. A 15ml_ solution from Allahali lake (Bangalore, India) containing 145ppb of U ions and 70ppb of Mn ions has been passed through the system containing sand coated with cobalt metal nanoparticles. The U and Mn contents in the water collected after the filtering process were 55ppb and 0.74ppb, respectively.

Claims

Claims
1 . A process for the extraction of heavy metal ions from water where the process for the extraction is based on coating-free cobalt metal nanoparticles introduced into contaminated water comprising steps of:
i. mixing coating-free cobalt metal nanoparticles in contaminated water; and
ii. waiting at least 5 seconds for heavy metal ion agglomerating around the coating-free cobalt metal nanoparticles, and
iii. extracting the cobalt metal nanoparticles coated with the heavy metal ions in the metallic or metal oxide form from the contaminated water
2. The process according to claim 1 wherein said coating-free cobalt metal nanoparticles are bonded on sand.
3. The process according to claim 1 and 2 wherein coating-free cobalt metal nanoparticles coated with heavy metal ions in the metallic or metal oxide form are extracted by using magnetic field of up to 1 Tesla.
4. The process according to any one of the preceding claims wherein said coating- free cobalt metal nanoparticles are agglomerated.
5. The process according to claim 1 wherein said coating-free cobalt metal nanoparticles are fixed on a substrate integrated in a filter.
6. The process according to any one of the preceding claims wherein said coating- free cobalt metal nanoparticles exhibit surperparamagnetic properties.
7. The process according to any one of the preceding claims wherein the coating- free cobalt metal nanoparticles are coated with a layer of cobalt oxide.
8. The process according to any one of the preceding claims wherein the coating- free cobalt metal nanoparticles are stable under air.
9. The process according to any one of the preceding claims wherein the coating- free cobalt metal nanoparticles are functionalized.
10. The process according to any one of the preceding claims wherein the coating- free cobalt metal nanoparticles are extracted using a magnetic field of at least 0.2 Tesla.
1 1 . The process according to claim 9 wherein the magnetic field is produced by a permanent magnet or an electromagnet.
12. The process according to claim 2 wherein said coating-free cobalt metal nanoparticles are bonded on a substrate, a carbon based support, a glass support, a metal support or a polymer support.
13. The process according to any one of the preceding claims wherein said coating- free cobalt metal nanoparticles are synthesized using non-hydrolytic sol-gel method.
14. The process according to any one of the preceding claims wherein said coating- free cobalt metal nanoparticles are have one layer of oxygen or hydroxyl groups on their surface.
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