WO2022156835A1 - Biochar-based composites for decontamination of chemical warfare agents - Google Patents

Biochar-based composites for decontamination of chemical warfare agents Download PDF

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Publication number
WO2022156835A1
WO2022156835A1 PCT/CZ2021/050073 CZ2021050073W WO2022156835A1 WO 2022156835 A1 WO2022156835 A1 WO 2022156835A1 CZ 2021050073 W CZ2021050073 W CZ 2021050073W WO 2022156835 A1 WO2022156835 A1 WO 2022156835A1
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alkaline earth
earth metal
metal oxide
biochar
composite material
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PCT/CZ2021/050073
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French (fr)
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Kristyna POSPISKOVA
Ivo SAFARIK
Jana OBORNA
Ivo Medrik
Jan Filip
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Univerzita Palackeho V Olomouci
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Priority to PCT/CZ2021/050073 priority Critical patent/WO2022156835A1/en
Publication of WO2022156835A1 publication Critical patent/WO2022156835A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
    • B01J20/041—Oxides or hydroxides
    • A—HUMAN NECESSITIES
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    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
    • A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
    • A62D3/33—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by chemical fixing the harmful substance, e.g. by chelation or complexation
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    • A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
    • A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
    • A62D3/35—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by hydrolysis
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    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
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    • B01J20/28004—Sorbent size or size distribution, e.g. particle size
    • B01J20/28007—Sorbent 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
    • B01J20/3204—Inorganic carriers, supports or substrates
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    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B01J20/3234—Inorganic material layers
    • B01J20/3236—Inorganic material layers containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/288—Treatment of water, waste water, or sewage by sorption using composite sorbents, e.g. coated, impregnated, multi-layered
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
    • A62D2101/02—Chemical warfare substances, e.g. cholinesterase inhibitors
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D2203/00—Aspects of processes for making harmful chemical substances harmless, or less harmful, by effecting chemical change in the substances
    • A62D2203/04—Combined processes involving two or more non-distinct steps covered by groups A62D3/10 - A62D3/40
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/102—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/112—Metals or metal compounds not provided for in B01D2253/104 or B01D2253/106
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/93—Toxic compounds not provided for in groups B01D2257/00 - B01D2257/708
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0225—Other waste gases from chemical or biological warfare
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2101/30—Organic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00—Use of specific compounds during water treatment
    • C02F2305/08—Nanoparticles or nanotubes

Definitions

  • the present invention relates to a composite material containing biochar support and alkaline earth metal oxide nanoparticles, method of preparation thereof, and use thereof for the removal of chemical warfare agents (categories: blister - sulfur mustards and nerve agents - G and V series).
  • chemical warfare agents categories: blister - sulfur mustards and nerve agents - G and V series.
  • Biochar based composites have been in the centre of interest for last few years.
  • Biochar is a carbon material, which is prepared from biomass by thermochemical process in the absence of oxygen, namely by slow or fast pyrolysis, hydrothermal carbonisation, gasification, etc.
  • Different types of biochar composites have been studied, where the carbon matrix is modified by various kinds of particles, e.g. metals / metal oxides / hydroxides (including special group of magnetic iron oxides, so these composites can be manipulated by external magnetic field) and other various functional or catalytic materials.
  • the biochar matrix itself contains various functional groups, surface active sites or catalytic components; and has a porous structure.
  • Biochar based nanocomposites can be prepared by various procedures. The most common process is pre-treatment of biomass by suitable precursor(s) followed by pyrolysis. Another possibility is modification of an already prepared biochar.
  • Nanocrystalline metal oxides exhibit properties of reactive sorbents during interaction with acid gases, polar organic compounds and chemical / biological warfare agents. Compounds are adsorbed and irreversibly degraded. Materials in powder form can be transformed into pellets, thin layers with other oxides (e.g. Fe2C>3, V2O3, MmCL, ZrCF. etc.) or into composites with catalytic metals (e.g. Cu) without significant loss of previous properties.
  • the disadvantage is that the activity of these oxides often decreases by prolonged exposure to air humidity (Lucas, E. et al. Chem.-Eur. J. 7, 2505-2510 (2001)).
  • Particles of metal oxides have been tested in several studies for the interaction with chemical warfare agents or their simulants. Adsorption of compounds or their hydrolysis can occur through the reactive sites on their surface, forming non-toxic products. Nanoparticles of these oxides can be more reactive, which is associated with a larger surface area, with a number of reactive sites, defects or structural specialities (donors of free electron pair or vacant orbitals, hydroxyl groups, ion vacations). Degradation of nerve paralytic compounds was studied e.g. on nanoparticles of aluminium oxide, magnesium oxide, calcium oxide, titanium dioxide, zinc oxide and on clay mineral fragments (Sharma, N. & Kakkar, R. Adv. Mater. Lett. 4, 508-521 (2013); Sharma, L.
  • Nanoparticles of magnesium oxide can simultaneously adsorb and degrade toxic chemical compounds; e.g. interaction with organophosphates has been studied.
  • the reaction mechanism of chemical warfare hydrolysis is associated with the formation of surface-bound non-toxic phosphonate complexes (in the case of VX and soman) or alkoxide (in the case of mustard gas) as compared to the basic hydrolysis in solution, where toxic product is formed.
  • mustard gas hydrolytic processes (including elimination of hydrochloric acid) occur to produce thiodiglycol and divinyl sulfide, which no longer bind to the surface (Sharma, N. & Kakkar, R. Adv. Mater. Lett. 4, 508-521 (2013); Wagner, G.W. et al. J. Phys. Chem. B 103, 3225-3228 (1999)).
  • Calcium oxide nanoparticles adsorb well acidic gaseous substances (e.g. SO2), polar organic substances, etc., so interactions with chemical warfare agents have been tested. Their decomposition (in the case of soman and substance VX) on the surface of nanoparticles proceeds similarly, forming surface-bound phosphonates; during the elimination reaction, calcium chloride is formed, which is more reactive than calcium oxide itself.
  • soman and substance VX acidic gaseous substances
  • the aim of the present invention is to provide materials and methods for decontamination of chemical warfare agents which are environmentally friendly, low-cost, easy-to-prepare, efficient, and have a broad specificity.
  • the present invention provides a composite material, method of production thereof, and a method for decontamination of chemical warfare agents (CWA), particularly suitable for use in aqueous environment.
  • CWA chemical warfare agents
  • the composite material of the present invention contains biochar and alkaline earth metal oxide nanoparticles.
  • the alkaline earth metal oxide nanoparticles are embedded in the biochar support or adsorbed on the biochar support. Such particles are non-covalently bound to the surface of biochar.
  • the alkaline earth metal oxide nanoparticles are deposited in particular on the surface of the biochar support (biochar matrix) individually or in aggregates.
  • the composite may contain also inert salt particles as a by-product of its preparation procedure.
  • the inert salt may be, in particular, an alkali metal halide, typically sodium chloride.
  • nanoparticles in the present application refers to particles having the size in the range of 1 to 250 nm.
  • Metal oxide particles is typically in the range of 5-40 % of the composite mass, preferably 10-30 % of composite mass. Value of metal oxide particle loading is estimated from thermogravimetric analysis.
  • Size of the composite surface area BET is typically in the range of 100-1000 m 2 /g, preferably 100-400 m 2 /g.
  • the BET surface is measured by N2 adsorption at 77 K.
  • the alkaline earth metal oxide nanoparticles include calcium oxide nanoparticles, magnesium oxide nanoparticles and mixtures thereof.
  • Another aspect of the invention is a method for preparation of the composite material of the invention.
  • the method comprises the steps of:
  • the precursor of alkaline earth metal oxide is an alkaline earth metal halide (typically chloride) or nitrate.
  • the step of pre-treatment of the carbon-containing biomaterial with the precursor of alkaline earth metal oxide is then preferably followed by treatment with alkali metal hydroxide, followed by the pyrolysis step.
  • the precursor of alkaline earth metal oxide is an alkaline earth metal halide (typically chloride) or nitrate, wherein the step of pre-treatment is followed by the step of pyrolysis.
  • alkaline earth metal halide typically chloride
  • nitrate typically nitrate
  • the precursor of alkaline earth metal oxide is an alkaline earth metal carbonate or hydroxide, wherein the step of pre-treatment is followed by the step of pyrolysis.
  • the carbon-containing biomaterial is wood, preferably in the form of sawdust or shavings.
  • the weight ratio of the precursor of alkaline earth metal oxide to the carbon- containing biomaterial is within the range of 3: 1 to 1:20, preferably 1: 1 to 1: 10.
  • the composites of the invention are effective for decontamination of CWA leakage.
  • the composites of the invention are a gentle alternative to standard agents such as hypochlorite -based agents which often have destructive effects on the treated surface (for example, hypochlorites are very strong oxidizing agents with exothermic reaction and bleaching effect).
  • the composites of the present invention were tested for decontamination of several types of chemical warfare agents.
  • the present invention further provides a method of decontamination of chemical warfare agents (CWA), which comprises the step of contacting a chemical warfare agent to be decontaminated with the composite material comprising biochar and alkaline earth metal oxide nanoparticles.
  • CWA chemical warfare agents
  • the CWA and the composite material of the invention are preferably contacted in an aqueous solution.
  • the CWA is present in an aqueous solution (such as water), and the composite material is added into this aqueous solution.
  • the composite material may be in solid form (e.g., powder) or in the form of aqueous suspension.
  • a surface containing a liquid CWA is treated by aqueous suspension of composite material (e.g. by spraying or sprinkling).
  • a surface containing a liquid CWA is treated by the composite material of the invention which is in solid form (e.g., powder), and this can be followed by addition of water (e.g. by spraying or sprinkling).
  • the CWA is preferably selected from blister agents, G-series nerve agents and V-series nerve agents. More preferably, the CWA is selected from sulphur mustard (mustard gas); soman, sarin, tabun, VX and Russian VX.
  • sulphur mustard mustard gas
  • soman soman, sarin, tabun, VX and Russian VX.
  • the composite material of the invention shows a very good decontamination efficiency.
  • the efficiency is particularly high for the VX compound.
  • the VX is a substance which does not undergo spontaneous hydrolysis in water and is particularly difficult to decontaminate.
  • the present invention thus further includes use of the composite materials comprising biochar and alkaline earth metal oxide nanoparticles for decontamination of CWA, preferably in aqueous environment (e.g. in aqueous solution).
  • the composite material of the invention contains biochar and alkaline earth metal oxide nanoparticles.
  • the alkaline earth metal oxide nanoparticles are nanoparticles of at least one alkaline earth metal oxide.
  • the nanoparticles may be nanoparticles of one alkaline earth metal oxide, or nanoparticles of several alkaline earth metal oxides.
  • Particularly preferred alkaline earth metal oxides are calcium oxide (CaO) and magnesium oxide (MgO).
  • the loading of the alkaline earth metal oxide nanoparticles is preferably in the range of 5 to 40 wt. %, more preferably 10 to 30 wt. %, relative to the total weight of the dry composite material.
  • the particle size of the nanoparticles is preferably within the range of 1-250 nm, more preferably 10- 120 nm.
  • nanoparticles of MgO are crystalline cubic MgO with size 15-25 nm.
  • CaO particle size ranges between 80-130 nm.
  • the nanoparticles may also form aggregates which may have the size within the range of 200-1000 nm.
  • the surface area of the composite material is preferably at least 100 m 2 /g, more preferably ranges between 100-400 m 2 /g, even more preferably in the range 120-200 m 2 /g.
  • the composite material of the invention is typically prepared by a process comprising the steps of:
  • the carbon-containing biomaterial may be, for example, sawdust, biomass, wood chips.
  • carbon-containing biomaterial is a material of biological (e.g., plant) origin which consists of or contains carbon-containing organic compounds (e.g., polysaccharides, proteins, etc.).
  • the carbon- containing biomaterial can contain particles of the size of up to 5 cm, more preferably up to 1 cm, even more preferably up to 5 mm (larger initial biomaterial particles are crushed or ground to smaller particles before pyrolysis to biochar, depending on further application; smaller composite particles are in better contact with contaminated aqueous environment or surface).
  • the precursor of alkaline earth metal oxide may be a compound selected from halides (typically chlorides), nitrates, carbonates and hydroxides of the corresponding alkaline earth metal.
  • halides typically chlorides
  • nitrates typically chlorides
  • hydroxides typically chlorides
  • the precursor is selected from alkaline earth metal soluble salts - halides (preferably chlorides) or nitrates.
  • This soluble precursor may be converted to a hydroxide form by precipitation with alkali metal hydroxide (e.g., sodium hydroxide or potassium hydroxide) or used directly and then treated at high temperature to form metal oxide.
  • alkali metal hydroxide e.g., sodium hydroxide or potassium hydroxide
  • the halide is precipitated with hydroxide (e.g., calcium chloride with sodium hydroxide to give calcium hydroxide and inert by-product sodium chloride) and then calcined to give calcium oxide; as another example, magnesium chloride can be directly calcined to give magnesium oxide.
  • hydroxide e.g., calcium chloride with sodium hydroxide to give calcium hydroxide and inert by-product sodium chloride
  • magnesium chloride can be directly calcined to give magnesium oxide.
  • precursor is selected from insoluble compounds such as carbonates or hydroxides and directly treated at high temperature to form metal oxide.
  • calcium oxide may be calcined from calcium carbonate or calcium hydroxide; as another example, the precursor of magnesium oxide may be magnesium hydroxide.
  • the pre-treatment of carbon-containing biomaterial by alkaline earth metal oxide precursor may be carried out by contacting or soaking the carbon-containing biomaterial with a solution or suspension of the alkaline earth metal oxide precursor.
  • the solution or suspension may preferably be an aqueous solution or suspension.
  • the temperature of pyrolysis is preferably within the range of 600 to 900 °C, and takes place under an inert atmosphere (preferably nitrogen).
  • an inert atmosphere preferably nitrogen
  • the pyrolysis may preferably be performed at a temperature within the range of 700 to 850 °C.
  • the pyrolysis may preferably be performed at a temperature within the range of 600 to 700 °C.
  • the pyrolysis may preferably be performed at a temperature about 700 °C.
  • the duration of pyrolysis is at least 30 minutes, preferably at least 1 hour.
  • Fig. 1 Decontamination reactions of various amounts of CaO/MgO-BC with VX in time.
  • Fig. 2. Decontamination reactions of various amounts of CaO/MgO-BC with GD in time.
  • Fig. 3. Decontamination reactions of various amounts of CaO/MgO-BC with HD in time.
  • Fig. 4. Decontamination reactions of various amounts of BC with VX in time.
  • Fig. 6. Degradation of VX by spontaneous hydrolysis at higher pH (sodium hydroxide water solution).
  • Fig. 7 Comparison of decontamination reactions of CaO/MgO-BC composite or biochar without modification (BC) with the degradation of VX in water and basic environment in time.
  • Fig. 8 Comparison of the reactivity of various materials (commercial nCaO nanoparticles, CaO-BC and CaO/MgO-BC composites) with VX and spontaneous degradation of VX in water or sodium hydroxide solution.
  • Fig. 9 Decontamination reactions of CaO/MgO-BC with GA, GB and RVX in time.
  • Sawdust pine and spruce wood was obtained from local sources; CWA (GD, purity 91.89%; HD, purity 93.74%; VX, purity 88.35%; GA, purity 95.03%; GB, purity 97.07%; VR, purity 97.51%) and other chemicals (sodium thiosulphate, commercial MgO and CaO particles for comparative purposes) were from Sigma Aldrich, isopropyl alcohol was from Merck and nonane was from Fluka. Other common chemicals for preparation of the composite materials were obtained from Lach-Ner, s.r.o., Czech Republic or Sigma Aldrich.
  • CWA chemical warfare agents
  • the structural and crystalline phase composition of samples was identified by X-ray powder diffraction (XRD); patterns were recorded on an X Pert PRO diffractometer (Malvern Panalytical, United Kingdom) in Bragg -Brentano geometry with Fe-filtered CoKa radiation (40 kV, 30 mA) at the 20 range from 10 to 105°.
  • XRD X-ray powder diffraction
  • the commercial standards SRM640 (Si) and SRM660 (LaB6) were used for the evaluation of the line positions and instrumental line broadening, respectively.
  • the acquired patterns were evaluated (including Rietveld analysis) using High Score Plus software in conjunction with PDF- 4+ database.
  • Thermogravimetric analysis (TGA) of materials was performed using thermal analyzer (STA 449 C Jupiter®, Netzsch-Geratebau GmbH) under N2/O2 atmosphere (alumina crucible, temperature range 45 °C - 1000 °C, heating rate of 10 K min ’).
  • the composite material is prepared as follows: carbon-containing biomaterial - namely sawdust, mixture of pine and spruce wood, 1-2 mm size, is soaked with calcium chloride aqueous solution (details are in Table 1). This is followed by precipitation of metal hydroxides by addition of sodium hydroxide solution to increase pH to approximate value 12. The sawdust is soaked in this mixture for several hours (typically overnight), the rest of the solution (supernatant) is poured out and the pre-treated biomaterial is dried in an oven (80 °C) (typically overnight).
  • This material is then pyrolyzed in tube laboratory furnace under inert gas (nitrogen) at 700 °C for 1 h to form biochar with embedded particles of calcium oxide anchored and distributed on a carbon (biochar) matrix. Finally, the composite CaO-BC is cooled down to laboratory temperature.
  • the composite material is prepared as follows: carbon-containing biomaterial - namely sawdust, mixture of pine and spruce wood, 1-2 mm size, is soaked with a mixture of calcium and magnesium chloride in aqueous solution (details are in Table 1). This is followed by precipitation of metal hydroxides by addition of sodium hydroxide solution to increase pH to approximate value 12. The sawdust is soaked in this mixture for several hours (typically overnight), the rest of the solution (supernatant) is poured out and the pre-treated biomaterial is dried in an oven (80 °C) (typically overnight).
  • This material is then pyrolyzed in tube laboratory furnace under inert gas (nitrogen) at 700 °C for 1 h to form biochar with embedded particles of calcium oxide and magnesium oxide anchored and distributed on a carbon (biochar) matrix. Finally, the composite CaO/MgO-BC is cooled down to laboratory temperature.
  • Corresponding pure biochar sample to each biochar composite is prepared by pyrolysis of untreated carbon-containing biomaterial in tube laboratory furnace under the same pyrolytic conditions as described for biochar composite.
  • Table 1 Overview of conditions for preparation of CaO-BC (Example 1) and CaO/MgO-BC (Example 2) composites.
  • COMPOSITE sawdust CaCL anh. (10 g) modification in salt solution (ca 400 CaO-BC
  • Composition of crystalline phase of the prepared composite materials from Example 1 and 2 was determined by X-ray powder diffraction.
  • the proportion of the individual components of composite and size of particles is included in Table 2.
  • the size of MgO nanoparticles is around 20 nm, the size of CaO particles are in the range of 85-115 nm.
  • Prepared materials were not washed after pyrolysis to maintain original state of CaO and MgO, so the composites contain crystalline NaCl, which is formed during the precipitation process of metal hydroxides. This component (NaCl) does not negatively affect any processes during utilization of composites after its dissolution in water (the concentration does not exceed the physiological saline concentration value in the standard use described).
  • Example 1 and 2 Surface structure and morphology of composite from Example 1 and 2 was studied by scanning electron microscopy. Surface of carbon (biochar) matrix is covered by nanoparticles and their nano to micrometer-sized aggregates.
  • Decontamination of selected real surfaces using composite aqueous suspension was performed as follows. Concrete and material with protective paint were contaminated with CWA drops (surface contamination was 10 g/m 2 ; the drop volume was 1 pl; HD: 20 drops, GD / VX: 25 drops). After 30 min of contamination, the surface was sprayed (using laboratory airbrush) with composite water suspension (CaO/MgO-BC; 1 g/100 mL; 2 doses were applied in two 15-min intervals, applied maximal amount of 100 ml of suspension, covering the whole surface of contaminated area) and decontaminated for 30 minutes. The samples were then placed in weighing bottles, 10 ml of hexane was added and the bottles were placed in an ultrasonic bath for 15 minutes. Concentrations of individual CWA in the extracts were determined on gas chromatograph (as described previously).
  • Decontamination of selected real surfaces using powdered composite was performed as follows. Butyl rubber and silicone were contaminated with CWA drops (surface contamination was 10 g/m 2 ; the drop volume was 1 pl; HD: 20 drops, GD / VX: 25 drops). After contamination (5 min for butyl rubber, 2 min for silicone), the powdered biochar composite was applied to sufficiently cover the surface and decontaminated for 2 minutes. After this treatment, the biochar was removed from the surfaces by wiping with a swab. Subsequently, the surfaces were wiped with a swab moistened with water. The samples were then placed in weighing bottles with 10 ml of isopropyl alcohol and placed in an ultrasonic bath for 5 minutes. The CWA concentrations in the extract were then determined on gas chromatograph (as described previously).
  • reaction rate constants (ki a k2) of the subsequent first order decontamination reaction were used to evaluate and match the measured and calculated data.
  • the reaction rate constants were calculated from the equation: where c T is the residual concentration of CWA in time r, Co indicates the initial concentration of CWA.
  • the percentage of decontamination was calculated by the dependence:
  • Example 5 Reactivity of various materials (commercial nCaO and nMgO nanoparticles, CaO-BC and CaO/MgO- BC composites from Example 1 and 2) with VX and spontaneous degradation of VX in water or sodium hydroxide solution were compared. Results are summarized in Table 9 and illustrated by graph (Fig. 8).
  • tested amount of commercial nanoparticles corresponds to estimated content (average value: 20 wt. %) of nanoparticles in composite (400 mg); selected values of pH 12.7 and 12.44 are proportional to estimated pH of suspension containing 200 mg or 100 mg of composite, respectively
  • Example 6 CaO/MgO-BC composite from Example 2 was also tested with other agents, namely GA, GB and RVX (using the same procedure). Results are summarized in Table 10 and illustrated by graph (Fig. 9).

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Abstract

The present invention relates to a composite material containing biochar support and alkaline earth metal oxide nanoparticles, wherein the alkaline earth metal oxide nanoparticles are embedded in the biochar support or adsorbed on the biochar support. The composite material is used in a method of decontamination of chemical warfare agents, which comprises the step of contacting a chemical warfare agent to be decontaminated with the composite material comprising biochar and alkaline earth metal oxide nanoparticles.

Description

Biochar-based composites for decontamination of chemical warfare agents
Technical Field
The present invention relates to a composite material containing biochar support and alkaline earth metal oxide nanoparticles, method of preparation thereof, and use thereof for the removal of chemical warfare agents (categories: blister - sulfur mustards and nerve agents - G and V series).
Background Art
Biochar based composites have been in the centre of interest for last few years. Biochar is a carbon material, which is prepared from biomass by thermochemical process in the absence of oxygen, namely by slow or fast pyrolysis, hydrothermal carbonisation, gasification, etc. Different types of biochar composites have been studied, where the carbon matrix is modified by various kinds of particles, e.g. metals / metal oxides / hydroxides (including special group of magnetic iron oxides, so these composites can be manipulated by external magnetic field) and other various functional or catalytic materials. The biochar matrix itself contains various functional groups, surface active sites or catalytic components; and has a porous structure. Generally, applications of carbon composites are focused on adsorption of hazardous metals, organic and inorganic contaminants and combined processes of adsorption and catalytic degradation (Tan, X.-F. et al. Bioresour. Technol. 212, 318-333 (2016)). Biochar based nanocomposites can be prepared by various procedures. The most common process is pre-treatment of biomass by suitable precursor(s) followed by pyrolysis. Another possibility is modification of an already prepared biochar.
Nanocrystalline metal oxides, especially MgO, CaO, AI2O3, ZnO, etc., exhibit properties of reactive sorbents during interaction with acid gases, polar organic compounds and chemical / biological warfare agents. Compounds are adsorbed and irreversibly degraded. Materials in powder form can be transformed into pellets, thin layers with other oxides (e.g. Fe2C>3, V2O3, MmCL, ZrCF. etc.) or into composites with catalytic metals (e.g. Cu) without significant loss of previous properties. The disadvantage is that the activity of these oxides often decreases by prolonged exposure to air humidity (Lucas, E. et al. Chem.-Eur. J. 7, 2505-2510 (2001)).
Particles of metal oxides have been tested in several studies for the interaction with chemical warfare agents or their simulants. Adsorption of compounds or their hydrolysis can occur through the reactive sites on their surface, forming non-toxic products. Nanoparticles of these oxides can be more reactive, which is associated with a larger surface area, with a number of reactive sites, defects or structural specialities (donors of free electron pair or vacant orbitals, hydroxyl groups, ion vacations). Degradation of nerve paralytic compounds was studied e.g. on nanoparticles of aluminium oxide, magnesium oxide, calcium oxide, titanium dioxide, zinc oxide and on clay mineral fragments (Sharma, N. & Kakkar, R. Adv. Mater. Lett. 4, 508-521 (2013); Sharma, L. & Kakkar, R. CrystEngComm. 19, 6913-6926 (2017)). Nanoparticles of magnesium oxide can simultaneously adsorb and degrade toxic chemical compounds; e.g. interaction with organophosphates has been studied. The reaction mechanism of chemical warfare hydrolysis is associated with the formation of surface-bound non-toxic phosphonate complexes (in the case of VX and soman) or alkoxide (in the case of mustard gas) as compared to the basic hydrolysis in solution, where toxic product is formed. In the case of mustard gas, hydrolytic processes (including elimination of hydrochloric acid) occur to produce thiodiglycol and divinyl sulfide, which no longer bind to the surface (Sharma, N. & Kakkar, R. Adv. Mater. Lett. 4, 508-521 (2013); Wagner, G.W. et al. J. Phys. Chem. B 103, 3225-3228 (1999)).
Calcium oxide nanoparticles adsorb well acidic gaseous substances (e.g. SO2), polar organic substances, etc., so interactions with chemical warfare agents have been tested. Their decomposition (in the case of soman and substance VX) on the surface of nanoparticles proceeds similarly, forming surface-bound phosphonates; during the elimination reaction, calcium chloride is formed, which is more reactive than calcium oxide itself. In the case of reaction with mustard gas, autocatalytic dehydrohalogenation occurs, the sulfonium ion forms as a competitive component in the reaction (Sharma, N. & Kakkar, R. Adv. Mater. Lett. 4, 508-521 (2013); Wagner, G.W. et al. J. Phys. Chem. B 104, 5118-5123 (2000)).
Up to now, only decontamination studies dealing with testing of bare metal oxide (nano)particles have been described.
The aim of the present invention is to provide materials and methods for decontamination of chemical warfare agents which are environmentally friendly, low-cost, easy-to-prepare, efficient, and have a broad specificity.
Summary of the invention
The present invention provides a composite material, method of production thereof, and a method for decontamination of chemical warfare agents (CWA), particularly suitable for use in aqueous environment.
The composite material of the present invention contains biochar and alkaline earth metal oxide nanoparticles. The alkaline earth metal oxide nanoparticles are embedded in the biochar support or adsorbed on the biochar support. Such particles are non-covalently bound to the surface of biochar. The alkaline earth metal oxide nanoparticles are deposited in particular on the surface of the biochar support (biochar matrix) individually or in aggregates. According the type of precursor and preparation process used, the composite may contain also inert salt particles as a by-product of its preparation procedure. The inert salt may be, in particular, an alkali metal halide, typically sodium chloride. The term “nanoparticles” in the present application refers to particles having the size in the range of 1 to 250 nm.
Loading of metal oxide particles is typically in the range of 5-40 % of the composite mass, preferably 10-30 % of composite mass. Value of metal oxide particle loading is estimated from thermogravimetric analysis.
Size of the composite surface area BET is typically in the range of 100-1000 m2/g, preferably 100-400 m2/g. The BET surface is measured by N2 adsorption at 77 K.
In preferred embodiments, the alkaline earth metal oxide nanoparticles include calcium oxide nanoparticles, magnesium oxide nanoparticles and mixtures thereof.
Another aspect of the invention is a method for preparation of the composite material of the invention. The method comprises the steps of:
- pre-treatment of a carbon-containing biomaterial with at least one precursor of alkaline earth metal oxide, and
- pyrolysis of the pre-treated carbon-containing biomaterial to form biochar composite with embedded or adsorbed alkaline earth metal oxide nanoparticles.
In some embodiments, the precursor of alkaline earth metal oxide is an alkaline earth metal halide (typically chloride) or nitrate. The step of pre-treatment of the carbon-containing biomaterial with the precursor of alkaline earth metal oxide is then preferably followed by treatment with alkali metal hydroxide, followed by the pyrolysis step. These embodiments result in material comprising inert alkali metal halide (in case of alkaline earth metal halide precursor).
In some embodiments, the precursor of alkaline earth metal oxide is an alkaline earth metal halide (typically chloride) or nitrate, wherein the step of pre-treatment is followed by the step of pyrolysis.
In some embodiments, the precursor of alkaline earth metal oxide is an alkaline earth metal carbonate or hydroxide, wherein the step of pre-treatment is followed by the step of pyrolysis.
In some embodiments, the carbon-containing biomaterial is wood, preferably in the form of sawdust or shavings. In a preferred embodiment, the weight ratio of the precursor of alkaline earth metal oxide to the carbon- containing biomaterial is within the range of 3: 1 to 1:20, preferably 1: 1 to 1: 10.
The composites of the invention are effective for decontamination of CWA leakage. The composites of the invention are a gentle alternative to standard agents such as hypochlorite -based agents which often have destructive effects on the treated surface (for example, hypochlorites are very strong oxidizing agents with exothermic reaction and bleaching effect). The composites of the present invention were tested for decontamination of several types of chemical warfare agents.
The present invention further provides a method of decontamination of chemical warfare agents (CWA), which comprises the step of contacting a chemical warfare agent to be decontaminated with the composite material comprising biochar and alkaline earth metal oxide nanoparticles.
The CWA and the composite material of the invention are preferably contacted in an aqueous solution. For example, the CWA is present in an aqueous solution (such as water), and the composite material is added into this aqueous solution. The composite material may be in solid form (e.g., powder) or in the form of aqueous suspension. Alternatively, a surface containing a liquid CWA is treated by aqueous suspension of composite material (e.g. by spraying or sprinkling). In some embodiments, a surface containing a liquid CWA is treated by the composite material of the invention which is in solid form (e.g., powder), and this can be followed by addition of water (e.g. by spraying or sprinkling).
The CWA is preferably selected from blister agents, G-series nerve agents and V-series nerve agents. More preferably, the CWA is selected from sulphur mustard (mustard gas); soman, sarin, tabun, VX and Russian VX.
The composite material of the invention shows a very good decontamination efficiency. The efficiency is particularly high for the VX compound. The VX is a substance which does not undergo spontaneous hydrolysis in water and is particularly difficult to decontaminate.
The present invention thus further includes use of the composite materials comprising biochar and alkaline earth metal oxide nanoparticles for decontamination of CWA, preferably in aqueous environment (e.g. in aqueous solution).
Detailed description of the invention
The composite material of the invention contains biochar and alkaline earth metal oxide nanoparticles. The alkaline earth metal oxide nanoparticles are nanoparticles of at least one alkaline earth metal oxide. The nanoparticles may be nanoparticles of one alkaline earth metal oxide, or nanoparticles of several alkaline earth metal oxides. Particularly preferred alkaline earth metal oxides are calcium oxide (CaO) and magnesium oxide (MgO).
The loading of the alkaline earth metal oxide nanoparticles, i.e., their amount in the composite material, is preferably in the range of 5 to 40 wt. %, more preferably 10 to 30 wt. %, relative to the total weight of the dry composite material.
The particle size of the nanoparticles is preferably within the range of 1-250 nm, more preferably 10- 120 nm. In some embodiments, nanoparticles of MgO are crystalline cubic MgO with size 15-25 nm. In some embodiments, CaO particle size ranges between 80-130 nm.
The nanoparticles may also form aggregates which may have the size within the range of 200-1000 nm.
The surface area of the composite material, expressed as BET measured by N2 adsorption/desorption at 77 K, is preferably at least 100 m2/g, more preferably ranges between 100-400 m2/g, even more preferably in the range 120-200 m2/g.
The composite material of the invention is typically prepared by a process comprising the steps of:
- pre-treatment of a carbon-containing biomaterial with at least one precursor of alkaline earth metal oxide, and
- pyrolysis of the pre-treated carbon-containing biomaterial to form biochar composite with embedded or adsorbed alkaline earth metal oxide nanoparticles.
The carbon-containing biomaterial may be, for example, sawdust, biomass, wood chips. Generally, carbon-containing biomaterial is a material of biological (e.g., plant) origin which consists of or contains carbon-containing organic compounds (e.g., polysaccharides, proteins, etc.). Preferably, the carbon- containing biomaterial can contain particles of the size of up to 5 cm, more preferably up to 1 cm, even more preferably up to 5 mm (larger initial biomaterial particles are crushed or ground to smaller particles before pyrolysis to biochar, depending on further application; smaller composite particles are in better contact with contaminated aqueous environment or surface).
The precursor of alkaline earth metal oxide may be a compound selected from halides (typically chlorides), nitrates, carbonates and hydroxides of the corresponding alkaline earth metal. Two manufacturing procedures are available. In the first case the precursor is selected from alkaline earth metal soluble salts - halides (preferably chlorides) or nitrates. This soluble precursor may be converted to a hydroxide form by precipitation with alkali metal hydroxide (e.g., sodium hydroxide or potassium hydroxide) or used directly and then treated at high temperature to form metal oxide. As an example, the halide is precipitated with hydroxide (e.g., calcium chloride with sodium hydroxide to give calcium hydroxide and inert by-product sodium chloride) and then calcined to give calcium oxide; as another example, magnesium chloride can be directly calcined to give magnesium oxide. In the second case precursor is selected from insoluble compounds such as carbonates or hydroxides and directly treated at high temperature to form metal oxide. As an example, calcium oxide may be calcined from calcium carbonate or calcium hydroxide; as another example, the precursor of magnesium oxide may be magnesium hydroxide.
The pre-treatment of carbon-containing biomaterial by alkaline earth metal oxide precursor may be carried out by contacting or soaking the carbon-containing biomaterial with a solution or suspension of the alkaline earth metal oxide precursor. The solution or suspension may preferably be an aqueous solution or suspension.
The temperature of pyrolysis is preferably within the range of 600 to 900 °C, and takes place under an inert atmosphere (preferably nitrogen). For example, to produce a composite material containing calcium oxide, the pyrolysis may preferably be performed at a temperature within the range of 700 to 850 °C. As another example, to produce a composite material containing magnesium oxide, the pyrolysis may preferably be performed at a temperature within the range of 600 to 700 °C. As yet another example, to produce a composite material containing calcium oxide and magnesium oxide, the pyrolysis may preferably be performed at a temperature about 700 °C. The duration of pyrolysis is at least 30 minutes, preferably at least 1 hour.
Brief description of drawings
Fig. 1. Decontamination reactions of various amounts of CaO/MgO-BC with VX in time. Fig. 2. Decontamination reactions of various amounts of CaO/MgO-BC with GD in time. Fig. 3. Decontamination reactions of various amounts of CaO/MgO-BC with HD in time. Fig. 4. Decontamination reactions of various amounts of BC with VX in time.
Fig. 5. Degradation of VX by spontaneous hydrolysis in water.
Fig. 6. Degradation of VX by spontaneous hydrolysis at higher pH (sodium hydroxide water solution). Fig. 7. Comparison of decontamination reactions of CaO/MgO-BC composite or biochar without modification (BC) with the degradation of VX in water and basic environment in time.
Fig. 8. Comparison of the reactivity of various materials (commercial nCaO nanoparticles, CaO-BC and CaO/MgO-BC composites) with VX and spontaneous degradation of VX in water or sodium hydroxide solution.
Fig. 9. Decontamination reactions of CaO/MgO-BC with GA, GB and RVX in time.
Examples of carrying out the Invention
Materials and Methods
Sawdust (pine and spruce wood) was obtained from local sources; CWA (GD, purity 91.89%; HD, purity 93.74%; VX, purity 88.35%; GA, purity 95.03%; GB, purity 97.07%; VR, purity 97.51%) and other chemicals (sodium thiosulphate, commercial MgO and CaO particles for comparative purposes) were from Sigma Aldrich, isopropyl alcohol was from Merck and nonane was from Fluka. Other common chemicals for preparation of the composite materials were obtained from Lach-Ner, s.r.o., Czech Republic or Sigma Aldrich.
List of chemical warfare agents (CWA) used:
GA . . . Tabun . . . (RS)-Ethyl W-Dimcthylphosphoramidocyanidatc
GB . . . Sarin . . . (RS)-Propan-2-yl methylphosphonofluoridate
GD ... Soman ... 3, 3'-Dimethylbutan-2-yl methylphosphonofluoridate
HD ... Sulfur mustard / Yperite / Mustard gas ... l-Chloro-2-[(2-chloroethyl)sulfanyl]ethane
VX ... Ethyl ({2-[bis(propan-2-yl)amino]ethyl}sulfanyl)(methyl)phosphinate
VR . . . Russian VX . . . W-Dicthyl-2-(mcthyl-(2-mcthylpropoxy)phosphoryl)sulfanylcthanaminc
Characterization of biochar composites
The structural and crystalline phase composition of samples was identified by X-ray powder diffraction (XRD); patterns were recorded on an X Pert PRO diffractometer (Malvern Panalytical, United Kingdom) in Bragg -Brentano geometry with Fe-filtered CoKa radiation (40 kV, 30 mA) at the 20 range from 10 to 105°. The commercial standards SRM640 (Si) and SRM660 (LaB6) were used for the evaluation of the line positions and instrumental line broadening, respectively. The acquired patterns were evaluated (including Rietveld analysis) using High Score Plus software in conjunction with PDF- 4+ database.
Particle-size and morphology characterization of materials was performed using scanning electron microscope (SEM) Hitachi SU 6600 (Hitachi, Tokyo, Japan) with accelerating voltage 5 kV.
Surface area analysis of samples was performed by means of N2 adsorption/de sorption measurements at 77 K on a volumetric gas adsorption analyzer (3Flex, Micromeritics) up to 0.965 P/Po. Prior to the analysis, the samples were degassed under high vacuum (7x l0-2 mbar) for 12 hours at 130 °C, while high purity (99.999 %) N2 and He gases were used for the measurements. The Brunauer-Emmett-Teller area (BET) was determined with respect to Rouquerol criteria for BET determination assuming a molecular cross-sectional area of 16.2 A2 for N2 (77 K).
Thermogravimetric analysis (TGA) of materials was performed using thermal analyzer (STA 449 C Jupiter®, Netzsch-Geratebau GmbH) under N2/O2 atmosphere (alumina crucible, temperature range 45 °C - 1000 °C, heating rate of 10 K min ’).
A/ Preparation of biochar composites
Example 1
The composite material is prepared as follows: carbon-containing biomaterial - namely sawdust, mixture of pine and spruce wood, 1-2 mm size, is soaked with calcium chloride aqueous solution (details are in Table 1). This is followed by precipitation of metal hydroxides by addition of sodium hydroxide solution to increase pH to approximate value 12. The sawdust is soaked in this mixture for several hours (typically overnight), the rest of the solution (supernatant) is poured out and the pre-treated biomaterial is dried in an oven (80 °C) (typically overnight). This material is then pyrolyzed in tube laboratory furnace under inert gas (nitrogen) at 700 °C for 1 h to form biochar with embedded particles of calcium oxide anchored and distributed on a carbon (biochar) matrix. Finally, the composite CaO-BC is cooled down to laboratory temperature.
Example 2
The composite material is prepared as follows: carbon-containing biomaterial - namely sawdust, mixture of pine and spruce wood, 1-2 mm size, is soaked with a mixture of calcium and magnesium chloride in aqueous solution (details are in Table 1). This is followed by precipitation of metal hydroxides by addition of sodium hydroxide solution to increase pH to approximate value 12. The sawdust is soaked in this mixture for several hours (typically overnight), the rest of the solution (supernatant) is poured out and the pre-treated biomaterial is dried in an oven (80 °C) (typically overnight). This material is then pyrolyzed in tube laboratory furnace under inert gas (nitrogen) at 700 °C for 1 h to form biochar with embedded particles of calcium oxide and magnesium oxide anchored and distributed on a carbon (biochar) matrix. Finally, the composite CaO/MgO-BC is cooled down to laboratory temperature.
B/ Preparation of biochar without modification (for comparative purposes)
Corresponding pure biochar sample to each biochar composite is prepared by pyrolysis of untreated carbon-containing biomaterial in tube laboratory furnace under the same pyrolytic conditions as described for biochar composite. Table 1. Overview of conditions for preparation of CaO-BC (Example 1) and CaO/MgO-BC (Example 2) composites.
MA'fERIAL PRE( LRS()R PRE fREA fMEX f RESELLING
COMPOSITE sawdust CaCL anh. (10 g) modification in salt solution (ca 400 CaO-BC
(50 g) NaOH (to pH approx, ml), precipitation of hydroxides by
12) increasing the pH, soaking (overnight), drying (80 °C, overnight) sawdust MgC12.6H2d (10 gj modification in salt solution (ca 400 CaO/MgO-BC
(50 g) CaCL anh. (5 g) ml), precipitation of hydroxides by
NaOH (to pH approx, increasing the pH, soaking (overnight),
12) drying (80 °C, overnight)
Table 2. Phases identified in the diffraction pattern of composites CaO-BC (Example 1) and CaO/MgO- BC (Example 2), their quantification and parameters specified by Rietveld analysis.
Sample Phase Relative amount MCL* Structure Lattice parameters
(weight %) (nm) a /b (nm)
CaO-BC nCaO 41 85 Cubic a = 0.4812
CaO/MgO-BC nCaO 11 115 Cubic a = 0.4820 nMgO 21 19 Cubic a = 0.4229
Ca(OH)2 3 21 Hexagonal a = 0.3605 b = 0.4918
* MCL - mean X-ray coherence length; samples contain nanocrystalline NaCl as a by-product of material preparation, relative amount and MCL is in the composite CaO-BC: 59 %, 88 nm and in the composite CaO/MgO-BC: 65 %, 45 nm)
Composition of crystalline phase of the prepared composite materials from Example 1 and 2 was determined by X-ray powder diffraction. The proportion of the individual components of composite and size of particles is included in Table 2. The size of MgO nanoparticles is around 20 nm, the size of CaO particles are in the range of 85-115 nm. Prepared materials were not washed after pyrolysis to maintain original state of CaO and MgO, so the composites contain crystalline NaCl, which is formed during the precipitation process of metal hydroxides. This component (NaCl) does not negatively affect any processes during utilization of composites after its dissolution in water (the concentration does not exceed the physiological saline concentration value in the standard use described). In practice, an unimportant washing and drying step is uneconomical and leads to unwanted chemical processes of CaO and MgO hydration. In addition, during the potential use of biologically active compounds as an additional component for the degradation of chemical warfare agents (e.g., enzymes), NaCl can act as an important part of the reaction mixture.
Surface structure and morphology of composite from Example 1 and 2 was studied by scanning electron microscopy. Surface of carbon (biochar) matrix is covered by nanoparticles and their nano to micrometer-sized aggregates.
Surface area analysis of materials from Example 1 and 2 (performed by means of N2 adsorption/desorption measurements at 77 K) gave results: 182 and 120 m2/g for CaO-BC and CaO/MgO-BC composite, respectively.
C/ Testing of composite reactivity with chemical warfare agents (CWAs)
Experiments were performed in aqueous suspensions. Appropriate amount of composite material from Example 1 and/or 2 (see Table 1 and 2; pure biochar without nanoparticle modification prepared under the same pyrolytic conditions was also tested for comparison) was mixed with aqueous solutions of CWA (1 pl of CWA into 10 ml of distilled water; CWAs were dissolved in 150 pl of isopropyl alcohol before diluting into water). This mixture was homogenized by shaking on automatic rotator.
100 pl of reaction mixture was removed at defined time intervals and put into the vial with 900 pl of nonane and 200 mg of sodium thiosulphate (extraction of CWA into nonane was performed by shaking for 1 minute). Finally, concentration of CWA in nonane was determined by gas chromatography (gas chromatograph 6890 N, Agilent Technologies, with FPD/P and FPD/S detectors; with autoinjectors - type G2613A Agilent 7683 Series and with carousel - type G2614A Agilent 7683 Series). Testing the effect of pH on the degradation of CWA was performed in hydroxide solution of appropriate pH (pH corresponding to the water suspension with the composite).
Decontamination of selected real surfaces using composite aqueous suspension was performed as follows. Concrete and material with protective paint were contaminated with CWA drops (surface contamination was 10 g/m2; the drop volume was 1 pl; HD: 20 drops, GD / VX: 25 drops). After 30 min of contamination, the surface was sprayed (using laboratory airbrush) with composite water suspension (CaO/MgO-BC; 1 g/100 mL; 2 doses were applied in two 15-min intervals, applied maximal amount of 100 ml of suspension, covering the whole surface of contaminated area) and decontaminated for 30 minutes. The samples were then placed in weighing bottles, 10 ml of hexane was added and the bottles were placed in an ultrasonic bath for 15 minutes. Concentrations of individual CWA in the extracts were determined on gas chromatograph (as described previously).
Decontamination of selected real surfaces using powdered composite was performed as follows. Butyl rubber and silicone were contaminated with CWA drops (surface contamination was 10 g/m2; the drop volume was 1 pl; HD: 20 drops, GD / VX: 25 drops). After contamination (5 min for butyl rubber, 2 min for silicone), the powdered biochar composite was applied to sufficiently cover the surface and decontaminated for 2 minutes. After this treatment, the biochar was removed from the surfaces by wiping with a swab. Subsequently, the surfaces were wiped with a swab moistened with water. The samples were then placed in weighing bottles with 10 ml of isopropyl alcohol and placed in an ultrasonic bath for 5 minutes. The CWA concentrations in the extract were then determined on gas chromatograph (as described previously).
Analysis of the results:
Kinetic data were analysed using the equation:
Figure imgf000012_0001
where cT is the residual concentration of CWA in time r, Co indicates the initial concentration of CWA.
In some experiments, reaction rate constants (ki a k2) of the subsequent first order decontamination reaction were used to evaluate and match the measured and calculated data. The reaction rate constants were calculated from the equation:
Figure imgf000012_0002
where cT is the residual concentration of CWA in time r, Co indicates the initial concentration of CWA. The percentage of decontamination was calculated by the dependence:
%=100- L .100 kc0
In the following graphs, the individual points of the measured CWA concentrations are converted to the percentage of decontamination (decontamination efficiency). Full lines are then calculated values.
Example 3
Testing of the dependence of composite (CaO/MgO-BC) reactivity on its various amount (200 / 100 / 50 / 20 mg) in the reaction mixture containing VX, GD and HD was performed. Results are presented in Fig. 1, 2 and 3 and Tab. 3, 4 and 5. Reaction with unmodified biochar (prepared without modification using the same pyrolytic conditions) was also performed for comparison - see Fig. 4 and Table 6.
Table 3. Decontamination efficiency of various amounts of CaO/MgO-BC in reaction mixture with VX.
Figure imgf000012_0003
Figure imgf000013_0001
Table 4. Decontamination efficiency of various amounts of CaO/MgO-BC in reaction mixture with GD.
Figure imgf000013_0002
Table 5. Decontamination efficiency of various amounts of CaO/MgO-BC in reaction mixture with HD.
Figure imgf000013_0003
Figure imgf000014_0001
Table 6. Decontamination efficiency of various amounts of BC in reaction mixture with VX.
Figure imgf000014_0002
Example 4
Removal efficiency of VX using composites from Example 1 and 2 was compared with the effect of spontaneous hydrolysis of VX in water or in alkaline environment (sodium hydroxide solution pH 12.7 / 12.44 / 12.07 / 11.66; selected values of pH are proportional to estimated pH of suspensions containing 200 / 100 / 50 / 20 mg of composite). Results are summarized in Table 7 and 8 and illustrated by graphs
(Fig. 5 and 6).
Tab. 7. Spontaneous hydrolysis of VX in water.
Figure imgf000015_0001
Tab. 8. Spontaneous hydrolysis of VX at higher pH (sodium hydroxide water solutions).
Figure imgf000015_0002
The discussed selected results are illustrated together in graph (Fig.7; selected value of pH 12.44 corresponds to estimated pH of suspension containing 100 mg of composite, respectively).
Example 5 Reactivity of various materials (commercial nCaO and nMgO nanoparticles, CaO-BC and CaO/MgO- BC composites from Example 1 and 2) with VX and spontaneous degradation of VX in water or sodium hydroxide solution were compared. Results are summarized in Table 9 and illustrated by graph (Fig. 8).
Tab. 9. Comparison of the reactivity of various materials (commercial nCaO and nMgO nanoparticles, CaO-BC and CaO/MgO-BC composites) with VX and spontaneous degradation of VX in water or sodium hydroxide solution.
Figure imgf000016_0001
(-) ... no decontamination reaction; tested amount of commercial nanoparticles (80 mg) corresponds to estimated content (average value: 20 wt. %) of nanoparticles in composite (400 mg); selected values of pH 12.7 and 12.44 are proportional to estimated pH of suspension containing 200 mg or 100 mg of composite, respectively
Example 6 CaO/MgO-BC composite from Example 2 was also tested with other agents, namely GA, GB and RVX (using the same procedure). Results are summarized in Table 10 and illustrated by graph (Fig. 9).
Table 10. Decontamination efficiency of CaO/MgO-BC composite (200 mg) in reaction mixture with GA, GB and RVX.
Figure imgf000017_0001
Example 7
Decontamination of selected surfaces by water suspension of biochar composite CaO/MgO-BC from Example 2 was performed to demonstrate examples of practical implementation of the invention.
Concentration of the composite used in suspension (1 g / 100 mb) is the minimal concentration to ensure effective degradation of VX in real conditions (higher amount of composite is possible to use without the negative effects on treated surface). Results are summarized in Table 11. Tab. 11. Decontamination efficiency of CaO/MgO-BC aqueous suspension during decontamination of model surfaces (protective coating and concrete) contaminated with HD, VX or GD.
Figure imgf000017_0002
Example 8
Decontamination of selected surfaces by powdered biochar composite CaO-BC from Example 1 was performed to demonstrate examples of practical implementation of the invention. Selected model surfaces were butyl rubber (used for the production of tires) and silicone (simulating human skin - CWA easily penetrates into its internal structure). The original CWA contamination was around 950 pg. cm 1. Results are summarized in Table 12. Tab. 12. Decontamination efficiency of CaO-BC powder during decontamination of model surfaces (butyl rubber, silicone) contaminated with HD, VX or GD.
Figure imgf000018_0001

Claims

1. A composite material containing biochar support and alkaline earth metal oxide nanoparticles, wherein the alkaline earth metal oxide nanoparticles are embedded in the biochar support or adsorbed on the biochar support.
2. The composite material according to claim 1, which further contains alkali metal halide nanoparticles.
3. The composite material according to claim 1 or 2, wherein the alkaline earth metal oxide nanoparticles are calcium oxide nanoparticles, magnesium oxide nanoparticles or mixtures thereof.
4. A method for preparation of the composite material of the invention, which comprises the steps of:
- pretreatment of a carbon-containing biomaterial with at least one precursor of alkaline earth metal oxide, and
- pyrolysis of the pretreated carbon-containing biomaterial to form biochar composite with embedded or adsorbed alkaline earth metal oxide nanoparticles.
5. The method according to claim 4, wherein the precursor of alkaline earth metal oxide is an alkaline earth metal halide or nitrate, and the step of pretreatment of the carbon-containing biomaterial with the precursor of alkaline earth metal oxide is followed by treatment with alkali metal hydroxide, which is followed by the pyrolysis step.
6. The method according to claim 4, wherein the precursor of alkaline earth metal oxide is an alkaline earth metal carbonate or hydroxide, and the step of pretreatment of the carbon-containing biomaterial with the precursor of alkaline earth metal oxide is followed by the pyrolysis step.
7. The method according to claim 4, wherein the precursor of alkaline earth metal oxide is selected from alkaline earth metal halide, alkaline earth metal nitrate, alkaline earth metal carbonate and alkaline earth metal hydroxide.
8. Use of the composite material according to any one of claims 1 to 3, for decontamination of chemical warface agents.
9. A method of decontamination of chemical warfare agents, which comprises the step of contacting a chemical warfare agent to be decontaminated with the composite material comprising biochar and alkaline earth metal oxide nanoparticles.
10. The method according to claim 9, wherein the chemical warfare agent and the composite material are contacted in an aqueous solution or suspension.
11. The method according to claim 9, wherein the composite material is in solid form when contacted with the chemical warfare agent, and the step of contacting is optionally followed by addition of water.
12. Use according to claim 8 or method according to any one of claims 9 to 11, wherein the chemical warfare agent is selected from blister agents, G-series nerve agents and V-series nerve agents; more preferably, the chemical warfare agent is selected from sulphur mustard, soman, sarin, tabun, VX and Russian VX.
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