WO2017098314A1

WO2017098314A1 - Method of obtaining mobile magnetic composite adsorbents

Info

Publication number: WO2017098314A1
Application number: PCT/IB2016/001644
Authority: WO
Inventors: Michal BYSTRZEJEWSKI; Michal SOSZYŃSKI; Przemyslaw STRACHOWSKI; Wojciech KICIŃSKI; Slawomir DYJAK
Original assignee: Uniwersytet Warszawski
Priority date: 2015-12-10
Filing date: 2016-11-18
Publication date: 2017-06-15
Also published as: PL415222A1; WO2017098314A4; PL239357B1

Abstract

A method of obtaining mobile magnetic composite adsorbent consists in that the magnetic filler is impregnated with carbon or polymer precursor. The obtained impregnate is subsequently processed using chemical and/or physical techniques. As carbon precursors there are used carbohydrates, preferably sucrose, glucose, poly(ethylene terephthalate), resorcinol-furfural xerogel or waste hydrocarbons, preferably rubber granulate from waste tires. In case of using xerogel as the carbon precursor, the carbon encapsulated magnetic nanoparticles are added to the mixture of monomers and then the reaction system is subjected to the gelation process. A polymer material a polymer material, preferably styrene, divinylbenzene, 2,4-dihydroxybeznoic acid, formaldehyde, resorcinol, furfural, 2- thiophenecarboxaldehyde is used as the polymeric precursor. The impregnate is processed with carbonization and subsequent activation, simultaneous carbonization and activation, polymerization. In the activation process of the material there are used caustic activating agents, preferably potassium hydroxide, carbon dioxide and steam, or hygroscopic activating agents, preferably zinc chloride and phosphoric(V) acid. The material obtained is subjected to the surface sulfonation reaction using a mixture of sulfuric(VI) acid and acetic anhydride. The method according to the invention allows to obtain mobile, magnetic, composite adsorbents of high corrosion resistance, using economical methods of material preparation. The properly designed material, depending on the adapted synthesis route, can be used for adsorption of organic compounds or heavy metal ions and organic compounds from aqueous solution. The magnetic properties of the material facilitate the rapid separation of the adsorbents from water environment. The tests of the surface morphology, iron content, adsorption properties against organic compounds and heavy metal ions and kinetics of the adsorption process of the materials obtained by the method according to the invention we carried out which proved their usefulness.

Description

Method of obtaining mobile magnetic composite adsorbents

The invention relates to a method of preparation of mobile composite adsorbents based on carbon encapsulated magnetic nanoparticles (CEMNPs) surrounded by an additional porous carbon or polymeric coating. Such unique fusion of magnetic properties of CEMNPs with textural properties typical for porous carbons allows to obtain an effective adsorbent which is mobile in the presence of external magnetic field. Moreover, the carbon and polymeric matrixes guarantee the corrosion resistance of magnetic phase against external aggressive corrosion agents.

Background of the invention

Activated carbons are commonly used as adsorbents in aqueous and gas environment due to their highly developed porosity and specific surface area (Journal of the Taiwan Institute of Chemical Engineers 53 (2015) 112-121 - dyes, Fuel Processing Technology 138 (2015) 271- 283 - C0₂, Colloids and Surfaces A: Physicochem. Eng. Aspects 467 (2015) 113-123 - phenol and its derivatives). This type of adsorbent is commonly used in a form of beds or suspensions. The use of adsorption beds is connected with a short contact time between the material and the solution, thus the materials used in this system should reveal fast kinetics of the adsorption process. On the other hand, the use of the adsorbent in the suspended form causes technical problems with its separation after the adsorption process is completed.

The development of research on activated carbons led to a new kind of adsorbents - composite materials with magnetic particles immobilized in the network of pores. The idea of such hybrid material allows to obtain an adsorbent which is mobile in the presence of external magnetic field.

A method of magnetic phase immobilization in the porous structure of activated carbon was described in US8097185. The activated carbon was suspended in the solution of a metal salt and subsequently dried. The mixture was pyrolyzed at 627°C and activated with C0₂/N₂ in 927°C. The as-prepared material was used for adsorption of gold ions from water solutions. The magnetic adsorbent could be quickly removed from the suspension. The magnetic phase (iron) was fixed in the pores of the adsorbent. Unfortunately, the iron immobilized in the pore network of activated carbon was protected not enough against the external corrosive agents. In this case the ferromagnetic phase could be irreversible leached off from the pores what resulted in decrease of magnetic properties of the adsorbent. It is known a method of synthesis of magnetic particles (Fe₂0₃, Fe₃0₄) coated with silica layer, which can be used in separation and purification of biological materials such as nucleic acids (US6255477, US0191718).

There are known carbon encapsulated magnetic nanoparticles (CEMNPs). It is a hybrid, magnetic, carbon material where the magnetic phase is encapsulated in a multi-shell spherical graphene structure with the thickness of the carbon shell of 1-lOnm (Powder Technology 246 (2013) 7-15). The magnetic core of the material can be formed of nanocrystals of metals, their alloys and compounds, especially those of ferromagnetic properties. The carbon encapsulated magnetic nanoparticles have high corrosion resistance which is enough to protect the metallic core in case of performing the adsorption process in a wide range of conditions (acid-base, temperature, time).

CEMNPs covered with silica layer are used as magnetic filler in porous materials (EP2244268). This material was designed to separation of the nucleic acids from biological samples.

It is possible to modify the surface of magnetic carbon nanocapsules with functional groups which change the surface properties of the material (US0059449). The magnetic phase was well protected against the aggressive external factors. It is possible to make the surface more hydrophobic - a such modification allows to apply magnetic nanoparticles in the removal of oily fraction from water-oil mixtures. Moreover, the implementation of chelating functional groups on the CEMNPs surface results in a material which adsorbs metal ions from water solution. A relatively small specific surface area of carbon encapsulated magnetic nanoparticles causes the limitations in its chemical modifications. The adsorption properties of such materials can be significantly lower in comparison with activated carbon-based adsorbents. The modified surface of an adsorbent loses its chemical inertness, whilst the chemical inertness is an important feature of effective adsorbents.

It is known a method of synthesis of magnetic carbon adsorbent by deposition of an additional layer of a carbon material, which can be done by mechanical mixing, e.g. mixing of CEMNPs with graphene flakes what leads to increase of a specific surface area of the final magnetic material (US0264144). Graphene, graphene oxide, graphite, carbon fibers, activated carbon and carbon nanotubes were used as an additional carbon coating. This method leads to deposit the additional carbon layers but the components were very weakly bonded and this resulted in low mechanical and chemical stability of such composite.

Therefore, there is a great need to develop magnetic carbon adsorbents with high corrosion resistance. The invention solves the limitation known in the state of the art. The invention describes mobile magnetic composite adsorbents which are resistant to corrosive external factors and have high adsorption performance.

Summary of the invention

A method of obtaining mobile magnetic composite adsorbent, according to the invention is characterised in that the magnetic filler is impregnated with carbon or polymer precursor, and then the impregnate is subsequently processed using chemical and physical techniques.

According to the invention, carbon encapsulated magnetic nanoparticles are used as the magnetic filler, where the magnetic particles are preferably synthesized by carbon arc discharge using iron, cobalt, nickel and their alloys as a magnetic phase. The diameter of carbon encapsulated magnetic nanoparticles is in the range 5-200 nm. The carbon encapsulated magnetic nanoparticles are subjected to the purification procedure which includes boiling in HCI water solution to remove the non-encapsulated magnetic phase. The impregnate contains 5-80 wt.%, of carbon encapsulated magnetic nanoparticles, preferably 9-75wt.% of carbon encapsulated magnetic nanoparticles.

According to the invention, as a carbon precursors there are used carbohydrates, including recycled hydrocarbons, preferably sucrose, glucose, poly(ethylene terephthalate), resorcinol-furfural xerogel or rubber granulate from waste tires. In case of using xerogel as the carbon precursor the carbon encapsulated magnetic nanoparticles are added to the mixture of monomers and then the reaction system is subjected to the gelation process.

According to the invention, as a polymeric precursors it is used a polymer material, preferably styrene, divinylbenzene, 2,4-dihydroxybeznoic acid, formaldehyde, resorcinol, furfural, 2-thiophenecarboxaldehyde. The carbon encapsulated magnetic nanoparticles are added to the mixture of monomers and then the reaction system is subjected to polymerization or gelation process what results in the formation of porous organic matrix. The following co-polymers and xerogels are used as a porous organic matrix: styrene/divinylbenzene, 2,4-dihydroxybeznoic acid/ formaldehyde, resorcinol/furfural, resorcinol/2-thiophenecarboxaldehyde.

According to the invention, the impregnate is processed with carbonization and subsequent activation, simultaneous carbonization and activation, polymerization. The carbonization process of the impregnate is carried out under atmosphere of argon or nitrogen at the temperature range of 500-850°C for 1-3 h. The activation of the material as a subsequent process after the carbonization process is carried out at temperature range of 500-850°C for l-3h. The material obtained in carbonization and activation processes is subjected to the purification procedure which includes boiling in 0.5-3 mol/dm³ HCI water solution.

According to the invention, for the activation process there are used caustic activating agents, preferably potassium hydroxide, carbon dioxide and steam, or hygroscopic activating agents, preferably zinc chloride and phosphoric(V) acid.

According to the invention, the simultaneous carbonization and activation process is carried out using activating agents, preferably potassium hydroxide, zinc chloride and phosphoric(V) acid. The subsequent activation after carbonization process is carried out using activating agents, preferably carbon dioxide and steam. During activation using potassium hydroxide the mass ratio of the activating agent and carbon formed during carbonization of the impregnate is in the range between 1:1 and 4:1. During activation using zinc chloride the mass ratio of the activating agent and precursor used to prepare the impregnate is in the range between 1:1 and 4:1. During activation using phosphoric(V) acid the mass ratio of the activating agent and precursor used to prepare the impregnate is in the range between 0.8:1 and 1:1. During activation using carbon dioxide it is used a mixture carbon dioxide and inert gas, preferably a mixture of Ar/C0₂ or N₂/C0₂with the volume ratio of 1:1.

According to the invention, the synthesized organic composites adsorbents are subjected to the surface sulfonation reaction using a mixture of sulfuric(VI) acid and acetic anhydride.

The invention provides an economical preparation method of the mobile magnetic composite adsorbents. The composite adsorbents obtained by the method according to the invention can be used in various applications due to the possibility of application of miscellaneous processing methods of the initial impregnates. Particularly, the composite adsorbents are dedicated for the removal of heavy metal ions and organic compounds from aqueous solution. The magnetic properties of the mobile magnetic composite adsorbents facilitate the rapid separation of the adsorbents from water environment.

The method of obtaining mobile magnetic composite adsorbents is described below in details in examples of use, with reference to the accompanying drawings, in which:

Fig. 1 shows the adsorption isotherms of phenol, 2-chlorophenol and 4-chlorophenol from aqueous solutions onto the composite obtained from carbon-encapsulated magnetic nanoparticles and sucrose. The initial impregnate was prepared with 9% mass content of carbon encapsulated magnetic nanoparticles with potassium hydroxide as the activating agent. The mass ratio of the activating agent and carbon was 4:1 (carbon is formed from precursor after carbonization process, carbonization yield was determined experimentally).

Fig. 2 shows the adsorption kinetic curve of phenol from aqueous solution onto the composite, obtained from carbon-encapsulated magnetic nanoparticles and resorcinol-furfural xerogel. The initial impregnate was prepared with 20% mass content of carbon encapsulated magnetic nanoparticles. The mass ratio of activating agent and carbon was equal 4:1.

Fig. 3 shows the adsorption isotherm of phenol onto the composite obtained from carbon- encapsulated magnetic nanoparticles and rubber granulate from waste tires with particle size between 0-0,4 mm.

Fig. 4 shows the adsorption isotherm of Fe³⁺ onto the composite obtained from carbon- encapsulated magnetic nanoparticles and styrene-co-divinylbenzene copolymer which was functionalized with sulfonic groups.

Fig. 5 illustrates the surface morphology of the composite adsorbent obtained according to the presented invention. The figure presents an image from a scanning electron microscope with 100 000 fold magnification.

Detailed description of the invention

The invention relates to the economical preparation of mobile, magnetic, composite adsorbents with high corrosion resistance. The developed composite is dedicated to the removal of various chemicals (metal ions, organic compound) from aqueous solutions. Its magnetic properties allows for its easy separation from the environment. The as-obtained composites, according to the invention, were systematically investigated to reveal the morphology, chemical composition and their adsorption properties in the removal of organic compounds and heavy metal ions.

The as-obtained composites are in a form of dusty or granulated carbon materials. The composite reveals strong magnetic properties due to presence of iron nanocrystais (the mass fraction in the range between 3-33%), whilst ca. 5% of Fe is absolutely enough to obtain a material which has mobility in the presence of external magnetic field. The specific surface area of obtained composite is between 200-1800 m²/g and its adsorption capacity reaches 160 mg/g for phenol and 250 mg/g for 2-chlorophenol and 4-chlorophenol. The adsorption kinetic onto synthesized materials is faster in comparison to the commonly used activated carbons. The presented mobile composite are also able to remove heavy metal ions, i.e. the observed adsorption capacity reaches 60 mg/g for Fe(lll) and 45 mg/g for Co(ll). The application of carbon encapsulated carbon nanoparticles solves a problem with corrosion resistance of the magnetic phase - one of the most important limitations in the synthesis and application of this type of composites. Carbonization of mixture consisting of carbon precursor or polymeric precursor and CEMNPs results in an extra carbon matrix which further enhances the corrosion resistance of the magnetic phase. The final magnetic material is homogenous and chemically stable. According to the invention, the synthesis of the composite includes chemical or physical activation what allows to develop the porosity and increase the specific surface area in the developed composite.

The invention includes the activation of the adsorptive material which gives the material appropriate porosity. According to the invention the activation is realized by two alternative manners: (i) physical activation and (ii) chemical activation.

Chemical activation causes partial oxidation and gasification of the carbon phase and in consequence results in an increase of specific surface area and total pore volume of activated materials. Various activation agents are used, namely carbon dioxide, steam and metal hydroxides. The chemical activation can be utilized directly after the completion of the carbonization (KOH, C0₂, H₂0) or during one-step carbonization/activation process (KOH).

Physical activation is mainly carried out in the initial part of the process, i.e. during the impregnation of the raw carbon precursor with hygroscopic agent, which results in the dehydration of the starting precursor.

The present invention is also related to the synthesis of magnetic, porous materials dedicated to the removal of heavy metal ions. In this case the surface chemistry plays the key role in the adsorption process. Therefore, in order to enhance the adsorption performance the adsorbent surface is covalently decorated with sulfonic groups.

The sulfonation reaction strongly influences the adsorption and physicochemical properties of the material subjected to sulfonation. For example, polystyrene becomes fully soluble in water after sulfonation. It is essential to develop a polymeric material which will be used as a matrix in the desired composite and the matrix constituents will assure that the composite will be stable enough in aqueous environment. According to the invention the cross-linked copolymers of styrene are used as porous, polymeric coating.

Examples of use

The method of obtaining mobile, magnetic, composite adsorbents was systematically tested. The method can be divided into following steps: synthesis of carbon encapsulated magnetic nanoparticles, preparing of impregnate, thermal treatment of the impregnate, activation, purification and analyses of the final product. In some cases carbonization and activation process are conducted in the same step.

Carbon encapsulated magnetic nanoparticles were synthesized by carbon arc discharge route with iron as a magnetic phase. A graphite cathode and graphite/iron anode (45% mass iron content) were used as a starting electrodes. All experiments were carried out at the constant pressure of 600 mbar under Ar-H₂ (50% vol.: 50% vol.) atmosphere. The arcing was generated with the current of 80A.

Example 1 Carbon encapsulated magnetic nanoparticles were used without purification from an excess of the non-encapsulated iron.

The impregnate was prepared as a suspension of 1 g of carbon encapsulated magnetic nanoparticles in 500 ml of sucrose (20 g/L) water-acetone solution. 11 g of activating agent (KOH) was added to the impregnate and this amount is the four-fold mass excess of KOH in relation to the carbon mass available from the precursor. The impregnate was sonicated during 30 min and subsequently dried at 100°C. The impregnated sample was located in a ceramic crucible and moved to the high-temperature chamber furnace.

The carbonization process associated with activation was conducted in a chamber furnace for lh under argon atmosphere (flow rate 2000 ml/min). Five process temperatures (500°C, 600°C, 700°C, 800°C, 850°C - heating rate 5°C /min) were used to select the best condition of the process. The temperature of 600°C has been chosen as the optimal temperature for the effective synthesis of the magnetic composites. Then, the furnace was cooled down to room temperature and the collected product was purified with HCI 1M solution (at boiling point) and rinsed with water. The washed sample was dried and at 100°C for 2h. The obtained magnetic composite was subjected to morphology and composition analyses. Table 1 presents the representative results.

Table 1. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in sucrose solution activated with four-fold excess of KOH, different temperature of the carbonization/activation.

Temperature Adsorption capacity for Iron content in final Specific Surface

Yield [%]

ra phenol [mg/g] composite [% mass] area [m²/g]

500 12 46 9.6 260

600 11 99 8.9 319

700 8 47 10.0 288

800 8 24 14.5 182

850 1.5 20 16.2 95 Example 2 Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared as a suspension of 1 g of carbon encapsulated magnetic nanoparticles in 500 ml of sucrose (20 g/L) water-acetone solution. Different activating agent (KOH) doses were used to determine the best activation conditions. The doses of KOH were 11 g, 5.5 g, 2,7 g and these values represent the KOH/carbon made from precursor mass ratio equal 4/1, 2/1 and 1/1 respectively. The impregnate was sonicated during 30 min and subsequently dried at 100°C. The carbonization was carried at 600°C and purification steps were the same as in example 1. Table 2 shows the representative results of analyses.

Table 2. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in sucrose solution activated with different content of KOH at 600°C.

Example 3 Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared as a suspension of 1 g or 8 g of carbon encapsulated magnetic nanoparticles in 500 ml of sucrose water-acetone 20 g/L solution. 11 g and 39.5 g of activating agent (KOH) was added to the impregnate and then impregnate was sonicated during 30 min and subsequently dried at 100°C. The carbonization and purification step were conducted according to example 1. Temperature of carbonization/activation - 600°C. Table 3 shows the representative results of analyses.

Table 3. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in sucrose solution activated with four-fold excess of KOH at 600°C.

CEMNPs content in Adsorption capacity for Iron content in final Specific Surface

Yield [%]

impregnate [% mass) phenol [mg/g] composite [% mass] area [m²/g]

9.09 11 99 8.9 319

44.4 12.2 13 26.2 190 Example 4. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared according to example 3 but with using glucose as the carbon precursor. The carbonization and purification step were conducted according to example 1. Table 4 shows the representative results of analyses.

Table 4. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in glucose solution activated with four-fold excess of KOH at 600°C.

Example 5. Carbon encapsulated magnetic nanoparticles were used without purification. Firstly, the solution of 10 g of cut, waste poly(ethylene terephthalate) in 50 g of phenol/l,l,2,2,-tetrachloroethane mixture was prepared (phenol/l,l,2,2,-tetrachloroethane mass ratio 3/2, 60°C). 1 g or 8 g of carbon encapsulated magnetic nanoparticles were subsequently dispersed in the as-prepared viscous solution. Then, substequently 7 g and 12 g of activating agent (KOH) was added to the impregnate which represents the four-fold mass excess of KOH in relation to the carbon made from the precursor. The impregnate was magnetically stirred. The carbonization and purification step were conducted according to example 1. Temperature of carbonization/activation - 600°C. The results of analyses are presented in Table 5.

Table 5. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in PET @ phenol/1,1,2,2,- tetrachloroethane solution activated with four-fold excess of KOH at 600°C.

Example 6. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared according to the example 1, but without using activating agent. The carbonization step was performed according to example 1. The obtained char was grinded and put in a quartz tube which was located in a tubular furnace. CO^Ar mixture was used as the activating agent in the subsequent activation process. Different activation temperatures in the range between 500-800°C were tested in order to select the optimal process conditions (heating rate 10°C/min, gas flow 165 ml/min). The activation was conducted during 1 h at the selected temperature. The purification step was conducted according to example 1. The results of analyses are presented in Table 6.

Table 6. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in sucrose solution. Carbonization at 600°C followed by activation with C0₂ at different temperatures.

Example 7. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared according to example 6, but with glucose instead sucrose was used as the carbon precursor. The carbonization step was performed according to example 1. The obtained char was grinded and moved in a quartz tube which was located in a tubular furnace. CO^Ar mixture was used as the activating agent in the subsequent activation process. Different activation temperatures in range between 550-700°C were tested in order to select the optimal process conditions (heating rate 10°C/min, gas flow 165 ml/min). The activation was conducted during lh at the selected temperature. The purification step were conducted according to example 1. The results of analyses are presented in table 7. Table 7. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in glucose solution. Carbonization at 600°C followed by activation with C0₂ at different temperatures.

Example 8. The carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared according to example 5 excluding the addition of KOH addition and using 1 g of carbon encapsulated magnetic nanoparticles. The carbonization and subsequent activation steps (activation agent C0₂) were conducted according to example 7. The purification step were conducted according to example 1. The results of analyses are presented in table 8.

Table 8. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in PET @ phenol/1,1,2,2,- tetrachloroethane solution. Carbonization at 600°C followed by activation with C0₂ at different temperatures.

Example 9. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared as a suspension of 1 g of carbon encapsulated magnetic nanoparticles in 500 ml of sucrose water-acetone 20 g/L solution. 40 g of hygroscopic activating agent (ZnCI₂) was added to the impregnate which represents the four-fold mass excess of KOH in relation to the carbon precursor. The impregnate was sonicated during 30 min and subsequently dried at 120°C. The material was located in a ceramic crucible and moved to the high-temperature chamber furnace. The carbonization process was conducted according to example 1 at 800°C. The purification procedure was performed according to example 1. Magnetic adsorbent was produced with the yield of 28%, adsorption capacity of phenol onto obtained material was 140 mg/g. Iron content was 4.3 wt.%, and the specific surface area was 997 m²/g-

Example 10. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared according to example 9 but with addition of 2 g or 3 g of carbon encapsulated magnetic nanoparticles and 30 g of ZnCI₂ and this amount represents the three-fold excess of activating agent in relation to the mass of carbon precursor. The drying and carbonization step were performed according to example 9 at 700°C. The purification procedure was performed according to example 1. The results of analyses are presented in table 9. Table 9. The results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in sucrose solution activated with three-fold excess of ZnCI₂ at 700°C.

Example 11. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared according to example 9 but glucose instead sucrose was used. 1 g or 3 g of carbon encapsulated magnetic nanoparticles and 30 g of ZnCI₂ were used what represents the three-fold excess of activating agent in relation to the mass of carbon precursor. The drying and carbonization step were performed according to example 10. The purification procedure was performed according to example 1. The results of analyses are presented in table 10.

Table 10. Results of adsorption experiments and physicochemical parameters of magnetic adsorbent. Carbon encapsulated magnetic nanoparticles in glucose solution activated with three-fold excess of ZnCI₂ at 700°C.

Example 12. Carbon encapsulated magnetic nanoparticles were used without purification. Firstly, the solution of 10 g of cut, waste poly(ethylene terephthalate) in 50 g phenol/l,l,2,2,-tetrachloroethane mixture was prepared (phenol/l,l,2,2,-tetrachloroethane mass ratio 3/2, 60°C). 1 g of carbon encapsulated magnetic nanoparticles was subsequently dispersed in the as-prepared viscous solution. 30 g of hygroscopic activating agent (ZnCI₂) was added to the impregnate which represents the three-fold mass excess of ZnCI₂ in relation to the mass of the carbon precursor. The impregnate was magnetically stirred. The impregnate was cooled down to room temperature and moved to the ceramic crucible. The carbonization step were the same as in example 10. The purification procedure was performed according to example 1. Magnetic adsorbent was produced with the yield of 40%, adsorption capacity of phenol onto obtained material reached 125 mg/g. Iron content was 18.2% wt.% and the specific surface area was 950 m²/g- Example 13. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared as a suspension of l g of carbon encapsulated magnetic nanoparticles in 500 ml of sucrose water-acetone 20 g/L solution. The impregnate was sonicated during 30 min and subsequently dried at 100°C. 8 g of the as-prepared material was mixed with 3.85 ml o 85% H₃P0₄, what represents the sucrose/phosphoric acid mass ratio 0.9/1, and then this mixture was dried at 60°C. The impregnate was located in a ceramic crucible and moved to a high-temperature chamber furnace. The carbonization process associated with activation was conducted in the chamber furnace for 0.5 h under argon atmosphere (2000 ml/min) at 500°C with the heating rate of 5°C/min. The purification procedure was performed according to example 1. The magnetic adsorbent was produced with the yield of 31%, adsorption capacity of phenol onto obtained material reached 55 mg/g. Iron content 12.5 wt. %, specific surface area - 1055 m²/g-

Example 14. Carbon encapsulated magnetic nanoparticles were used without purification. The impregnate was prepared as a suspension of 1 g of carbon encapsulated magnetic nanoparticles in 500 ml of sucrose water-acetone 20 g/L solution. The impregnate was sonicated during 30 min and subsequently dried at 100°C. The dry mixture was moved to a ceramic crucible and located in the high-temperature chamber furnace. The carbonization process was carried out in chamber furnace for lh under argon atmosphere (2000ml/min) at 600°C with heating rate 5°C/min. After the process the furnace was cool down and the obtained char was pounded and moved to a quartz crucible and put in a tubular furnace. When the temperature of furnace reached 850°C (10°C/min) the activation process by nitrogen saturated with water vapor was started, the process was carried out during 2 h. The purification procedure was performed according to example 1. Magnetic adsorbent was produced with the yield of 6%, the adsorption capacity of phenol onto obtained material reached 36 mg/g. Iron content - 2.8% mass, specific surface area - 265 m²/g-

Example 15. Carbon encapsulated iron nanoparticles were subjected to the purification process in order to remove the non-encapsulated iron. The raw CEMNPs were boiled in 3M HCI solution during 5h, then the material was washed with distilled water to neutral pH and dried. The impregnate was prepared as a suspension of 0.5g or 2.5g of purified carbon encapsulated iron nanoparticles in a solution of 1.4 g of resorcinol, 2.4 ml of furfural, 13 ml of methanol and 13 ml of water, and the as-prepared mixture was sonicated and then acidified with 1ml of 36% HCI solution. The acidified liquid mixture started transform into a stiff gel. The impregnate consisting of carbon encapsulated iron nanoparticles dispersed in organic gel was subsequently carbonized during 2 h at 800°C with heating rate 3°C /min. The furnace was cooled down after the process, then sample was washed with water, ethanol and acetone until the supernatant was transparent. The content of iron in the obtained materials reached 12.3% and 27.1%, and the respective adsorption capacities for phenol reached 90 mg/g and 60 mg/g respectively.

Example 16. Carbon encapsulated iron nanoparticles were subjected to the purification process in order to remove the non-encapsulated iron. The raw CEMNPs were boiled in 3M HCI solution during 5h, after then the material was washed with distilled water to neutral pH and dried. The impregnate was prepared as a suspension of 0.5g or 2.5g of carbon encapsulated iron nanoparticles in a solution of 1.4 g of resorcinol, 2.4 ml of furfural, 13 ml of methanol and 13 ml of water, as prepared mixture was sonicated and then acidified with 1ml of 36% HCI solution. The acidified liquid mixture started transform into a stiff gel. The obtained gel was mixed two-fold or four-fold excess of KOH, and the as prepared impregnate was carbonizied/activated at 700°C. The final composite was purified with water and ethanol. The content of iron in the obtained materials reached 5.9% and 16.4%, and the adsorption capacities for phenol reached 120 mg/g and 110 mg/g respectively. Example 17. Carbon-encapsulated iron nanoparticles were purified according to example 15. The impregnate was prepared according to example 15. The impregnate was divided into several parts and then every part was carbonized according to example 15 but at 600°C, 800°C and 1000°C. The purification procedure was carried out according to example 15. The content of iron in the obtained materials was 9.7% and 12.3%, 10.1%, respectively and the adsorption capacities for phenol were 90 mg/g and 90 mg/g and 100 mg/g, respectively.

Example 18. Carbon-encapsulated iron nanoparticles were purified according to example 15. The impregnate was prepared as a mixture of 0.24g or 1.9 g of purified carbon encapsulated iron nanoparticles 1,5 g of resorcinol and 3 g of 2-thiophenecarboxaldehyde in 30 ml of methanol. After adding of 1,5ml of 36% HCI the mixture was stirred at 60°C. The obtained gel was located in an oven at 65°C during 24 h what resulted in the cross-linked material. The as-prepared composite was dried at 75°C. Table 11 presents the results of adsorption experiments. Table 11. Results of adsorption experiments - heavy metal ions onto magnetic adsorbent. Carbon encapsulated iron nanoparticles in methanol solution of resorcinol and 2- thiophenecarboxaldehyde.

Example 19. The material synthesized according to example 18 was subjected to sulfonation. 2 g of composite was dispersed in solution of 50 ml of 1,2-dichloroethane, and the as-prepared suspension was added to the solution containing 50 ml of 1,2-dichloroethane, 12 ml of 95% of sulfuric acid and 12 ml of acetate anhydride. The mixture was magnetically stirred during 4 h at 60°C. The obtained material was filtered and washed with ethanol and water to neutral pH and dried at 60°C. The results of analyses are presented in table 12.

Table 12. Results of adsorption experiments - heavy metal ions onto magnetic adsorbent. Carbon encapsulated iron nanoparticles in methanol solution of resorcinol and 2- thiophenecarboxaldehyde. The sulfonated material.

Example 20. Carbon-encapsulated iron nanoparticles were purified according to example 15. The impregnate was prepared as a suspension of 0,15g or l,5g of carbon encapsulated iron nanoparticles in the solution containing 0,65g of K₂C0₃, l,45g of 1,4- dihydroxybenzoic acid and 30ml of water, the as-prepared mixture was subjected to sonication. 3,45 ml of formalin and 1 g of K₂C0₃ was added during the sonication. The reactants were cooled by water because the gelation process was exothermic. The as-obtained gel was located in an oven at 75°C for 48 h what resulted in the cross-linked material. The composite was washed with 0.5M HCI solution and water and then dried by lyophilization. The adsorption capacity of Co²⁺ ions onto obtained organic composites with 5% and 35% CEMNPs content reached 13mg/g and 5mg/g respectively.

Example 21. Carbon-encapsulated iron nanoparticles were purified according to example 15. 250 mg or 500 mg or 1000 mg of the purified CEMNPs were dispersed in a mixture consisting 20ml water, 10 ml of 10% polyvinyl alcohol solution and 10 ml of 1% sodium dodecyl sulfate solution. The as-prepared suspension was heated up to 70°C and mechanically stirred. Then 1 ml of divinylbenzene, 4ml of styrene and 150 mg of benzoyl peroxide were added to the mixture and the suspension was mechanically stirred for 4h. The product was filtered, washed with ethanol and water and dried at 60°C during 12h.

Example 22. The material synthesized according to the example 21 was subjected to the sulfonation reaction. 2 g of composite was dispersed in 50 ml of 1,2-dichloroethane. The mixture consisted of 50ml of 1,2-dichloroethane, 12 ml of 95% sulfuric acid and 12ml of acetate anhydrite was added to the prepared suspension. The reaction was carried out at 60°C during 4h with mechanical stirring. After this time the product was filtered, washed with water to neutral pH and dried at 60°C. The materials with initial carbon encapsulated iron nanoparticles content of 250 mg, 500 mg and 1000 mg were tested as an adsorbent of Fe³⁺ ions from water solution. The adsorption capacity onto the obtained composites reached 22 mg/g, 27 mg/g and 65 mg/g respectively.

Example 23. The carbon encapsulated iron nanoparticles were used without purification. The impregnate were prepared as a solid mixture 5g of rubber granulate with particles size in range between 0-0.4 mm (from waste tires, separated pure rubber phase which was free from other components of the tire), 0.5g of carbon encapsulated iron nanoparticles and 9.16 g of activated agent (KOH) what represents the four-fold mass excess of KOH in relation to the carbon precursor. The impregnate ingredients were mixed by a mortar and automatic mixer. The impregnate was located in a ceramic crucible and placed in a high-temperature chamber furnace. The carbonization process associated with activation were conducted in chamber furnace at 600°C with the heating rate of 10°C/min for lh under argon atmosphere (2000 ml/min). After the process the furnace was cooled down to room temperature, and the obtained material was purified by boiling in 1M HCI solution in order to remove the non-encapsulated iron particles. The composite was washed with water and dried. Magnetic adsorbent with 11.5% of mass iron content was produced with yield of 18.1%.

Claims

1. A method of obtaining mobile magnetic composite adsorbent characterised in that the magnetic filler is impregnated with carbon or polymer precursor, and then the impregnate is subsequently processed using chemical and physical techniques.

2. A method according to claim 1, characterised in that carbon encapsulated magnetic nanoparticles are used as a magnetic filler, where the magnetic particles are preferably synthesized by carbon arc discharge using iron, cobalt, nickel and their alloys as a magnetic phase.

3. A method according to claim 2, characterised in that the diameter of carbon encapsulated magnetic nanoparticles is in the range 5-200 nm.

4. A method according to claim 2, characterised in that the carbon encapsulated magnetic nanoparticles are subjected to the purification procedure which includes boiling in HCI water solution to remove the non-encapsulated magnetic phase.

5. A method according to claim 2, characterised in that the impregnate contains 5-80 wt.%, of carbon encapsulated magnetic nanoparticles, preferably 9-75wt.%.

6. A method according to claim 1, characterised in that as a carbon precursors there are used carbohydrates, including recycled hydrocarbons, preferably sucrose, glucose, poly(ethylene terephthalate), resorcinol-furfural xerogel or rubber granulate from waste tires.

7. A method according to claim 6, characterised in that in case of using xerogel as the carbon precursor the carbon encapsulated magnetic nanoparticles are added to the mixture of monomers and then the reaction system is subjected to the gelation process.

8. A method according to claim 1, characterised in that as a polymeric precursors it is used a polymer material, preferably styrene, divinylbenzene, 2,4-dihydroxybeznoic acid, formaldehyde, resorcinol, furfural, 2-thiophenecarboxaldehyde.

9. A method according to claim 8, characterised in that the carbon encapsulated magnetic nanoparticles are added to the mixture of monomers and then the reaction system is subjected to polymerization or gelation process what results in porous organic matrix.

10. A method according to claim 9, characterised in that as a porous organic matrix there are used the following co-polymers and xerogels: styrene/divinylbenzene, 2,4-dihydroxybeznoic acid/ formaldehyde, resorcinol/furfural, resorcinol/2- thiophenecarboxaldehyde.

11. A method according to claim 1, characterised in that the impregnate is processed with carbonization and subsequent activation, simultaneous carbonization and activation, polymerization.

12. A method according to claim 11, characterised in that the carbonization process of the impregnate is carried out under atmosphere of argon or nitrogen at the temperature range of 500-850°C for 1-3 h.

13. A method according to claim 12, characterised in that activation of the material as a subsequent process after the carbonization process is carried out at temperature range of 500-850°C for l-3h.

14. A method according to claim 12, characterised in that the material obtained in carbonization and activation processes is subjected to the purification procedure which includes boiling in 0.5-3 mol/dm³ HCI water solution.

15. A method according to claim 11, characterised in that for activation process there are used caustic activating agents, preferably potassium hydroxide, carbon dioxide and steam, or hygroscopic activating agents, preferably zinc chloride and phosphoric(V) acid.

16. A method according to claim 15, characterised in that the simultaneous carbonization and activation process is carried out using activating agents, preferably potassium hydroxide, zinc chloride and phosphoric(V) acid.

17. A method according to claim 15, characterised in that the subsequent activation after carbonization process is carried out using activating agents, preferably carbon dioxide and steam.

18. A method according to claim 16, characterised in that during activation using potassium hydroxide the mass ratio of the activating agent and carbon formed during carbonization of the impregnate is in the range between 1:1 and 4:1.

19. A method according to claim 16, characterised in that during activation using zinc chloride the mass ratio of the activating agent and precursor used to prepare the impregnate is in the range between 1:1 and 4:1.

20. A method according to claim 16, characterised in that during activation using phosphoric(V) acid the mass ratio of the activating agent and precursor used to prepare the impregnate is in the range between 0.8:1 and 1:1.

21. A method according to claim 16-17, characterised in that during activation using carbon dioxide it is used a mixture carbon dioxide and inert gas, preferably a mixture of Ar/C0₂ or N₂/C0₂ with the volume ratio of 1:1.

22. A method according to claim 1, characterised in that the synthesized organic composites adsorbents are subjected to the surface sulfonation reaction using a mixture of sulfuric(VI) acid and acetic anhydride.