METHOD OF PRODUCTION OF ADSORPTION/FILTRATION NANOMATERIAL FOR HIGH-VOLUME CLEANING OF LIQUIDS AND COMPOSITE ADSORPTION/FILTRATION NANOMATERIAL

Abstract

A method of manufacturing a carbon nanotubes-based adsorption/filtration nanomaterial for high-volume cleaning of fluids, which are annealed without access to ambient air at a temperature of 300 to 1150 C. for 0.1 to 12 hours, is described, said carbon nanotubes being subsequently immobilized on a support. substrate based on fibrous natural or synthetic material. Preferably, an inert coarse-grained inorganic and/or organic material is mixed with the immobilized carbon tubes to form a composite adsorption/filtration nanomaterial as a homogeneous mixture.

Claims

1. A process for the production of a carbon nanotube-based adsorption/filtration nanomaterial for high-volume cleaning of fluids based on carbon nanotubes, characterized in that the carbon nanotubes are annealed without access to ambient air at a temperature of 300 to 1150 C. for 0.1 to 12 hours to remove amorphous carbon, graphene, fullerenes and other by-products of carbon crystallization, to form carbon nanotubes without lattice distortion and a chemically modified surface, said carbon nanotubes being subsequently immobilized on a support substrate based on fibrous natural or synthetic material.

2. The process for the production of a carbon nanotube-based adsorption/filtration nanomaterial for high-volume cleaning of fluids, according to claim 1, characterized in that a pulping of the natural or synthetic material takes place in water or an organic solvent to form a suspension of natural or synthetic fibres.

3. The process for the production of a carbon nanotube-based adsorption/filtration nanomaterial for high-volume cleaning of fluids according to claim 1, characterized in that an inert coarse-grained inorganic and/or organic material is added to the immobilized carbon nanotubes in a weight ratio of immobilized carbon nanotubes on substrate to an inert coarse-grained inorganic and/or organic material of 1:15 to 1:0.001 to form a composite homogeneous mixture.

4. An adsorption/filtration nanomaterial, for high-volume fluid purification, produced by the process according to claim 1, characterized in that it comprises immobilized carbon nanotubes on a support substrate based on fibrous natural or synthetic material.

5. The adsorption/filtration nanomaterial according to claim 4, characterized in that it is in the form of a stationary large-volume three-dimensional adsorption bed with a diameter of 0.03 to 10 m and a filling height of 0.03 to 5 m.

6. An adsorption/filtration nanomaterial in the form of a homogeneous mixture, for high-volume liquid cleaning, produced by the process according to claim 3, characterized in that it comprises immobilized carbon nanotubes on a support substrate based on fibrous natural or synthetic material, and further comprises an inert inorganic and/or organic coarse-grained material in a volume weight ratio of immobilized carbon nanotubes on the substrate to an inert coarse-grained inorganic and/or organic material of 1:15 to 1:0.001.

7. The adsorption/filtration nanomaterial according to claim 4, characterized in that the immobilized carbon nanotubes contain a catalytic metal seed particle from the crystallization.

8. The adsorption/filtration nanomaterial according to claim 7, characterized in that the catalytic particle is iron or another transition metal of the Periodic Table of the Elements.

9. The adsorption/filtration nanomaterial according to claim 4, characterized in that the fibrous natural or synthetic material comprises fibres, wherein the fibres are cellulose fibres, synthetic fibres, glass fibres, wool fibres or cotton fibres, whereas the fibre diameter being from 0.1 to 500 m, and their length is 0.1 mm to 1000 mm.

10. The adsorption/filtration nanomaterial according to claim 6, characterized in that the inert coarse-grained material is glass, silica sand, alumina, granular activated carbon, crushed coconut shells, or synthetic stone, whereas having a grain size ranging from 0.01 to 5 mm.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0036] FIG. 1 shows an optical image of an adsorption/filtration nanomaterial according to the present invention.

[0037] FIG. 2A shows a comparison of adsorption isotherms of untreated CNTs (bare) and annealed CNTs (pur).

[0038] FIG. 2B shows linearized forms of adsorption isotherms of untreated CNTs (bare) and annealed CNTs (pur).

EXAMPLES

Example 1

[0039] a) The adsorption/filtration nanomaterial of the present invention was prepared from commercially available carbon nanotubes (CNTs). An amount of 16 g of CNTs was weighed into a glass vessel and diluted to a volume of 2 l with water and dispersed by ultrasound. In the next step, the CNTs were separated from the aqueous suspension by vacuum filtration, spread on a glass tray and dried at 50 C. After drying, the CNTs were ground to a fine powder which was layered in a thin layer on a glass tray and the CNTs were thus annealed in a closed oven without fresh air at 630 C. for 2 hours, with the weight ratio of oxygen in the air to the weight of the CNTs being treated was 1:16. Under these conditions, the oxygen present in the furnace chamber is consumed, which upon reaction with amorphous carbon, graphene, fullerenes and other carbon crystallization by-products creates a non-oxidizing atmosphere preventing the combustion of additional carbon.

[0040] In another embodiment of this example, the annealing was performed at 320 C. for 5 h in oven without access to fresh air as described in the paragraph above. Furthermore, for example, at a temperature of 1050 C. for 1 hour. In all the above examples, purified CNTs free of amorphous carbon, graphene, fullerenes and other carbon crystallization by-products were prepared. The annealed CNTs were weighed into a glass vessel and mixed together with 2 l of water. The CNTs were then disintegrated/dispersed using a Fisherband 11201a ultrasonic homogenizer for 15 min (20-80 kHz, 20-100% A).

[0041] 16 g of pulp were weighed into a glass vessel and suffused with 5 l of water. Using conventional mixers, the pulp was mixed for 1 minute to form a suspension of cellulose fibres in water.

[0042] The above-described suspension of disintegrated/dispersed CNTs in water was added to the cellulose fibre suspension. The mixture was then homogenized using a mixer for 2 min. During this step, the CNTs are fixed on the surface of the cellulose fibres. The aqueous CNT-cellulose suspension is then freed of excess water. The CNT-cellulose suspension is poured onto a stainless-steel screen lined with a nonwoven filtration cloth and left there until excess water drains from it. The wet CNT-cellulose mixture was transferred to a stainless-steel mixer for further processing.

[0043] 438 g of an inert coarse-grained inorganic and/or organic material, in particular silica sand with a grain size of 0.1-0.5 mm, were added to a stainless-steel mixer with a CNT-cellulose mixture. The mixture was homogenized for 5 minutes using a mixer. By mixing with an inert coarse-grained inorganic and/or organic material, a large-volume adsorption/filtration composite nanomaterial is formed in the form of a homogeneous mixture. The weight ratio of the immobilized nanotube on the support substrate to the inert inorganic and/or organic material is in this case 1:13.6.

[0044] The adsorption/filter material prepared as described above could then be filled into adsorption vessels of various types and constructions so as to produce a large-volume adsorption apparatus with a layer height of 30 cm and a diameter of 5 cm. The placement of the adsorbent bed in the adsorption apparatus and the flow of water through the adsorbent bed is arranged so that the purified water flows through the entire height of the adsorption/filtration nanomaterial. It is therefore a large-volume adsorption device that does not use membranes and contains CNTs as the active material. [0045] b) In another embodiment of this example, the CNTs annealed as described in the second paragraph of this example were disintegrated/dispersed using a Fisherband 11201 ultrasonic homogenizer for 15 min (20-80 kHz, 20-100% A).

[0046] Subsequently, 16 g of polypropylene fibres were weighed into a glass vessel and suffused with 5 l of water. Using commonly available mixers, the fibres were pulped for 1 minute to form a suspension of polypropylene fibres in water. Polypropylene fibres had a diameter of 30 microns and a length of 25 mm.

[0047] The above-described suspension of disintegrated/dispersed CNTs in water was added to the polypropylene fibre suspension. The mixture was then homogenized using a mixer for 2 min. During this step, the CNTs are fixed on the surface of the polypropylene fibres. The aqueous CNT-polypropylene fibres suspension is then freed of excess water. The CNT-polypropylene fibres suspension is poured onto a stainless-steel sieve lined with a nonwoven filtration cloth and left there until excess water drains from it. The wet CNT-polypropylene fibres mixture material was transferred to a stainless-steel mixer for further processing.

[0048] 438 g of an inert coarse-grained inorganic and/or organic material, in this embodiment of Example 1, specifically crushed limestone with a grain size of 1-3 mm, were added to a stainless-steel mixer with a CNT-polypropylene fibres. The mixture was homogenized for 5 minutes using a mixer. Mixing with crushed limestone produces a large-volume adsorption/filtration nanomaterial. [0049] c) In another embodiment of this example, 16 g of disintegrated/dispersed CNTs were mixed with 16 g of fibrous cellulose, and material permeability tests were performed in comparison with the material according to paragraph b). The results showed that the permeability of such a material was on average 23% lower than that of a composite material containing an inert coarse-grained inorganic and/or organic material.

Example 2

[0050] The adsorption/filtration nanomaterial prepared according to Example 1, except that synthetic fibers were used to fix the CNTs and the CNTs used were not annealed. The adsorption capacity of the nanomaterial with unannealed CNTs was 25% lower, measured on a methylene blue standard, as documented in FIG. 2.

Example 3

[0051] The adsorption rate (adsorption kinetics) of the nanomaterial prepared according to Example 1 is approximately 10 times higher than that of GAC. This fact is described in this example.

[0052] One 3.5 cm diameter glass column with a barren bottom was packed with the adsorbent of the present invention, and second column with the GAC. The height of the adsorbent in both columns was 8 cm. A cane molasses solution with a concentration of 1 wt. % (corresponding to a BRIX value of 1) was used as model water contaminated with organic substances. The molasses solution flowed gravitationally through the layer of both adsorbents, with the linear flow rate of the molasses solution being similar in both cases. The resulting contact times of the molasses solution with the adsorbent (residence time) were 10 s for the adsorbent material according to the invention and 12 s for GAC.

[0053] Despite the comparable contact time of the molasses solution with the adsorbent, the adsorbent according to the invention completely removed the molasses from the solution (BRIX 0), while for the GAC adsorbent the decrease in molasses concentration in the solution was minimal (BRIX 0.98). Thus, this example clearly demonstrates the fact that a substantially shorter residence time (10 s for molasses as a pollutant) is sufficient to remove certain organic substances from water with the adsorbent of the present invention in comparison to GAC, which in practice normally requires a residence time of 10 minutes or more.

Example 4

[0054] This example describes the use of an adsorption/filtration nanomaterial prepared according to Example 1 for the removal of drug residues and antibiotics from already treated wastewater at the outlet of a central wastewater treatment plant (WWTP).

[0055] The collected wastewater (already treated by technology used in wastewater treatment plants, referred to herein as V_COV) was subjected to analysis, which monitored the content of 50 different drugs and antibiotics. The analysis revealed the presence of 37 of the 50 monitored substances. The concentrations of these substances are summarized in Table 1.

TABLE-US-00001 TABLE 1 Summary of the content of drugs and antibiotics in the wastewater and after adsorption on the material according to the invention. V_COV T_COV_10 T_COV_20 Compound name (ug/L) (ug/L) (ug/L) 10,11-Dihydro-10- 0.010 0 0 hydroxy Carbamazepine 10,11- 0.600 0 0 Dihydroxycarbamazepine 2-Hydroxy 0.040 0 0 Carbamazepine 4-Hydroxy 0.430 0 0 Diclofenac Atenolol 0.060 0 0 Azithromycin 0.230 0 0 Bezafibrate 0.010 0 0 Caffeine 0.200 0 0 Carbamazepin 0.490 0 0 Carbamazepine 0.570 0 0 10,11-Epoxide Carboxyibuprofen 0 0 0 Chloramphenicol 0 0 0 Ciprofloxacin 0 0 0 Clarithromycin 0.250 0 0 Diclofenac 1.270 0 0 Diltiazem 0.040 0 0 Erythromycin 0.070 0 0 Fluoxetine 0.050 0 0 Furosemide 1.130 0 0 Gabapentin 1.710 1.508 1.236 Gemfibrozil 0.040 0 0 Hydrochlorothiazide 0.790 0 0 Iohexol 0 0 0 Iopamidol 0.030 0 0 Iopromide 0 0 0 Ketoprofen 0.120 0 0 Lincomycin 0.030 0 0 Metoprolol 1.850 0 0 Naproxen 0.350 0 0 Nifedipine 0 0 0 O-Desmethylnaproxen 0.190 0 0 Oxcarbazepine 0.150 0 0 Paracetamol 0 0 0 Paraxanthine 0.100 0 0 Penicillin G 0 0 0 Ranitidine 0.650 0 0 Roxithromycin 0.080 0 0 Saccharin 0.120 0 0.082 Sertraline 0.080 0 0 Sulfamerazine 0 0 0 Sulfamethazine 0 0 0 Sulfamethoxazol 0.390 0 0.250 Sulfanilamide 0 0 0 Sulfapyridine 0.300 0 0 Tramadol 0.660 0 0 Triclocarban 0 0 0 Triclosan 0 0 0 Trimethoprim 0.130 0 0 Venlafaxine 0.430 0 0 Warfarin 0.030 0 0

[0056] The adsorption/filtration nanomaterial was filled into a laboratory adsorption column. The adsorption column was provided with a barren bottom in the lower part, on which an adsorption/filter material with a height of 30 mm was subsequently layered. The column was connected at the bottom to a vacuum pump, which was the driving force behind the filtration.

[0057] The wastewater V_COV was filtered through an adsorption column prepared as described above. For the analysis of drugs and antibiotics content, a sample of filtered water after 10 and 20 litres of filtered wastewater was taken. These samples were marked as T_COV_10 and T_COV_20. After filtering the wastewater through the adsorption/filtration nanomaterial, only 3 of the originally 37 substances present were found. The concentration of these three substances, which were not fully captured during filtration, decreased. The adsorption/filtration nanomaterial behaved as broad-spectrum adsorption material in real wastewater, i.e. it captured a wide range of chemically different substances and it was arranged in the form of a large-volume bed, whose height was 4 times greater than its width.

Example 5

[0058] This example describes the ability of an adsorption/filtration nanomaterial prepared according to Example 1 to remove four selected pesticides from model water (most common in groundwater and surface water in the Czech Republic).

[0059] The model solution was prepared from the following analytical grade pesticides: chloridazon, alachlor, metazachlor, metolachlor. The concentration of individual pesticides in the model solution was 150 mg/l, which corresponds to a total concentration of 600 mg/l. Of course, such high concentrations will not occur in real waters and were thus chosen only for the purpose of determining the adsorption capacity of the adsorbent. The adsorption bed was arranged as in Example 3. The model solution contained four pesticides at the same time, in order to approximate the real conditions. In real waters, several different substances will always be adsorbed simultaneously.

[0060] Indicative adsorption isotherms for individual pesticides present in the solution were measured on the model solution. The percentage decrease in the concentration of individual pesticides was calculated from them, as shown in Table 2. From the measured data it is evident that even with such high concentrations of pesticides in model waters, adsorption/filtration nanomaterial can remove 35 to 70% of micropollutants present.

[0061] In real waters, where the total concentration of micropollutants is significantly lower (units to low tens of g/l), the percentage capture will be significantly higher, similar to the drug capture described in Example 4.

TABLE-US-00002 TABLE 2 Percentage decrease of pesticide concentration in the model solution after adsorption on the material according to the invention. The average decrease based on four experiments performed at different pesticide concentrations is shown in bold. Chloridazon Alachlor Metazachlor Metolachlor 67.87% 50.34% 26.45% 56.61% 73.03% 29.68% 40.69% 61.04% 68.35% 33.85% 36.67% 49.43% 67.10% 44.63% 41.84% 58.09% 69.09% 39.62% 36.41% 56.29%

Example 6

[0062] This example describes the ability of an adsorption/filtration nanomaterial prepared according to Example 1 to remove four selected pesticides from model water, the same as in Example 5, except that their initial concentrations are at the level expected in real waters (on the order of low tens g/l).

[0063] The model solution was prepared from the following analytical grade pesticides: chloridazon, alachlor, metazachlor, metolachlor. The concentrations of individual pesticides in the model solution were 1.7-2.6 g/l, which corresponded to a total concentration of all pesticides of 8.24 mil. These relatively low concentrations can be expected in real waters and this example is therefore complementary to Example 5. The adsorption material was in this case arranged in a stainless-steel pressure filter with a diameter of 22.5 cm, where the height of the adsorption material according to the invention was 26 cm, 15 cm, 10 cm and 5 cm. The residence time, which was 313 s, 147 s, 78 s and 25 s, also depended on the height of the adsorption bed. The results in table 3 show the concentration of pesticides in input water as well as in water which passed through the adsorbent of different height. The results in this table show reduction of pesticide concentration by more than 99% with the exception of one pesticide at a thickness of the adsorption layer of 5 cm. This example further illustrates the rapid adsorption kinetics of pollutants.

TABLE-US-00003 TABLE 3 Concentrations of the four selected pesticides in the input water and the water after passing through the filter filled with different heights of the adsorbent according to the invention. (g/l) Alachlor Chloridazon Metazachlor Metolachlor Total Input 1.74 2.63 1.92 1.95 8.24 water 26 cm 0.005 0.01 0.01 0.01 0.035 Capture, 99.7 99.6 99.5 99.5 99.6 % 15 cm 0.005 0.01 0.01 0.01 0.035 Capture, 99.7 99.6 99.5 99.5 99.6 % 10 cm 0.005 0.01 0.01 0.01 0.035 Capture, 99.7 99.6 99.5 99.5 99.6 % 5 cm 0.02 0.01 0.112 0.011 0.153 Capture, 98.9 99.6 94.2 99.4 98.1 %

Example 7

[0064] This example describes the ability of an adsorption/filtration nanomaterial prepared according to Example 1 to disinfect wastewater at the outlet of a wastewater treatment plant (V_COV) and groundwater from the Elbe region, Kersko (V_KER) (Czech Republic) arranged in the form of a large-volume adsorption bed.

[0065] First, the input water samples (V_COV and V_KER) were subjected to microbiological analysis by culturing microorganisms with growth specifications at 22 C. and 36 C. (according to SN EN ISO 6222), determination of intestinal enterococci (SN EN ISO 7899-2), determination of coliform bacteria in non-disinfected waters (SN 75 7837), determination of thermotolerant coliform bacteria and E. coli (SN 75 7835), determination of Clostridium perfringens (Annex No. 6 to Decree No. 252/2004 Coll.). Furthermore, a microscopic analysis was performed in order to determine the presence of biosestone (living organisms) and abiosestone (non-living particles) according to SN 75 7712 and SN 75 7713 standards.

[0066] For the purpose of this experiment, a laboratory adsorption column was packed as described in Example 2. Both water samples were then filtered through this column and samples after 10 and 20 filtered litres were taken for the analyses described above. The results of microbiological, resp. microscopic analysis of disinfected water, are given in Table 4, resp. Table 5.

[0067] Microbiological analysis shows the effectiveness of the filter in non-chemical microbial decontamination of water. CNTs have a demonstrable effect on cell wall disruption (National Research Council (US) Safe Drinking Water Committee. Drinking Water and Health: Volume 2. Washington (DC): National Academies Press (US); 1980. IV, An Evaluation of Activated Carbon for Drinking Water Treatment Available from: https://www.ncbi.nlm.nih.gov/books/NBK234593/). Although drinking water was not prepared from highly contaminated and microbially very active water by above described filtration, a significant decrease in the content of microorganisms suggests that a significantly lower amount of chlorine could be used for additional microbial decontamination, the use of which is also problematic in itself (residual chlorine in water and formation of chlorinated hydrocarbons. (Koek F.: Pro voda s chlorem, pro voda bez chloru? Sbomk konference Pitn voda 2010, s. 35-40. W&ET Team, . Budejovice 2010. ISBN 978-80-254-6854-8)

[0068] Microscopic analysis shows the effectiveness of the adsorption/filtration nanomaterial to eliminate plant and animal masses from filtered water. Since biosestone and abiosestone are represented by relatively large particles, their complete capture is expected.

[0069] The number of cultured bacteria (KOLI, ECOLI, ENTERO, CLO; see Table 4 for explanations) are summarized in Table 4.

TABLE-US-00004 TABLE 4 Summary of the results of microbiological analysis of wastewater samples (V_COV), groundwater (V_KER) and corresponding filtered water samples (T_COV_10, T_COV_20 and T_KER). V_COV T_COV_10 T_COV_20 V_KER T_KER CUMI 22 C. 49120 10 131 3720 15 [CFU/ml] CUMI 36 C. 29840 3 80 2580 9 [CFU/ml] COLI 57000 7 89 210 0 [CFU/100 ml] ECOLI 27700 4 16 104 0 [CFU/100 ml] ENTERO 10700 20 11 0 0 [CFU/100 ml] CLO 1000 0 10 0 0 [CFU/100 ml] Explanations: CUMI22 C. . . . culturable microorganisms with growth specification at 22 C. CUMI36 C. . . . culturable microorganisms with growth specification at 36 C. COLI . . . coliform bacteria ECOLI . . . Escherichia coli ENTERO . . . intestinal enterococci CLO . . . Clostridium perfringens CFU . . . colony forming units

TABLE-US-00005 TABLE 5 Summary of the results of microscopic analysis of wastewater samples (V_COV), groundwater (V_KER) and corresponding filtered water samples (T_COV_10, T_COV_20 and T_KER). V_COV T_COV 10 T_COV 20 V_KER T_KER Number Number Number Number Number Biosestone/type [indiv./ml] [indiv./ml] [indiv./ml] [indiv./ml] [indiv./ml] Cyanobacteria 6 Diatoms 20 4 Chlorococcal algae 12 Colorless 42 4 whipworms Funnels 16 Purses and covers 10 Total number of 106 8 biosestone [indiv./ml] Abioseston/type Percentage Percentage Percentage Percentage Percentage of coverage of coverage of coverage of coverage of coverage [%] [%] [%] [%] [%] Anorg. particles, 3 3 2 2 1 sand, starch, diatom boxes, rose. fibers, animal residues

Example 8

[0070] The last example shows the ability of the adsorption/filtration nanomaterial prepared according to Example 1 to remove water from the viral load, namely the removal of rotaviruses A.

[0071] For the purposes of this experiment, wastewater was first taken from the wastewater treatment plant, but this time immediately after the sieves, i.e. water that has not yet undergone the biological sludge treatment process. 8.8 million rotavirus A particles were found in the unfiltered wastewater. No rotavirus A particles were found in the water that passed through the adsorption/filtration nanomaterials. With current knowledge, it can be assumed that virus elimination is caused by the capture of virus particles in the structure of the adsorption/filtration nanomaterial. The measurements were performed in duplicate to verify the accuracy of the measurements and its summary is shown in Table 6.

TABLE-US-00006 TABLE 6 Summary of the number of viral particles measured in the wastewater (taken just after the sieves) and in water after adsorption on the material according to the invention. Number of virotic particles in 1 I of concentrated Sample Cp wastewater/treated water Sample nmb.1 29.08 1690 (concentrated wastewater) Sample nmb.2 29.24 1510 (concentrated wastewater) Sample nmb.1 Not detected (concentrated wastewater after treatment with adsorption/filtration material) Sample nmb.1 Not detected (concentrated wastewater after treatment with adsorption/filtration material) Negative control Not detected