MAGNETIC BIOMASS CARBON-QUATERNARY PHOSPHONIUM SALT STERILIZATION MATERIAL, PREPARATION METHOD THEREFOR AND USAGE THEREOF

Abstract

The present invention provides a magnetic biochar-quaternary phosphonium salt bactericidal material, a preparation method therefor and usage thereof, and belongs to the field of water treatment. The preparation method comprises: 1) using corn straw biochar as a precursor to prepare magnetic biochar by a co-precipitation method; and 2) adding the magnetic biochar into deionized water, then adding a quaternary phosphonium salt, performing the magnetic stir at room temperature, raising the temperature after sufficient impregnation, carrying out a hydrothermal reaction, and then cooling to the room temperature to obtain the bactericidal material. The temperature is raised to 60° C.˜70° C. The recycling of the biochar material is effectively realized, the long-acting sterilization of the quaternary phosphonium salt bactericide and the magnetic recovery and recycling of the materials are realized, the residue of the bactericide is reduced, and a foundation is laid for the effective removal of microorganisms in wastewater.

Claims

1. A magnetic biochar-quaternary phosphonium salt bactericidal material, characterized by the preparation method of the material, comprising the following steps: 1-1) using corn straw biochar as a precursor to prepare magnetic biochar by a co-precipitation method; 1-2) adding the magnetic biochar into deionized water, followed by an addition of quaternary phosphonium salt, performing magnetic stir at room temperature and sufficient impregnation, then heating for a hydrothermal reaction and cooling to room temperature to obtain the bactericidal material.

2. The magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 1, wherein the heating temperature for a hydrothermal reaction was 60° C.˜70° C.

3. The magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 1, wherein the mass ratio of the magnetic biochar and the quaternary phosphonium salt was 1:(1-50).

4. The magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 3, wherein the impregnation time in the step 1-2) is not less than 12 h.

5. The magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 4, wherein the quaternary phosphonium salt includes dodecyl tributyl phosphonium bromide.

6. The magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 4, wherein the step 1-1) particularly comprises the following steps: 1) under anoxic environment, adding Fe.sup.3+ and Fe.sup.2+ sequentially into deionized water with vigorous stir, followed by an addition of ammonia, and adding a biochar suspension after the reaction is stable, magnetically stirring in a water bath to obtain the product; 2) performing the solid-liquid separation of the product obtained in step 1), washing to remove impurities, and drying until the washing liquid is neutral to obtain the magnetic biochar.

7. Use of the magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 1, wherein the bactericidal material was used for the control of microbial contamination in water, and then the bactericidal material was separated and recovered from the water using a magnet.

8. The use of the magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 7, comprising the following steps: a) washing and drying the recovered bactericidal material, and then regenerating the product according to the step 1-2); b) adding the product prepared in the step a) into water containing microorganisms for sterilization; c) repeating the steps a) and b).

9. The use of the magnetic biochar-quaternary phosphonium salt bactericidal material according to claim 8, wherein the microorganisms include Escherichia coli and/or Staphylococcus aureus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a scanning electron microscope (SEM) image of magnetic biochar prepared in Example 1;

[0036] FIG. 2 is a magnetic hysteresis loop for magnetic bactericidal materials prepared in Example 1-5;

[0037] FIG. 3 is a X-ray diffraction (XRD) pattern of magnetic bactericidal materials prepared in Example 1-5;

[0038] FIG. 4 is Fourier transform infrared spectrometer (FTIR) spectra of magnetic bactericidal materials prepared in Example 1-5;

[0039] FIG. 5 is a thermo-gravimetric analysis (TGA) plot of magnetic bactericidal materials prepared in Example 1-5;

[0040] FIG. 6 shows the quaternary phosphonium salt (QPS) cumulative release profiles from magnetic bactericidal materials prepared in Example 2-5;

[0041] FIG. 7 is a transmission electron microscopy (TEM) image of Escherichia coli treated with magnetic bactericidal materials prepared in Example 2-5 in a scale of 1 μm;

[0042] FIG. 8 is a transmission electron microscopy (TEM) image of Escherichia coli treated with magnetic bactericidal materials prepared in Example 2-5 in a scale of 200 nm.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention provides the preparation of magnetic biochar-quaternary phosphonium salt, which is composed of biochar, magnetic irons and quaternary phosphonium salt. The method of preparing a magnetic biochar-quaternary phosphonium salt composite comprises the steps of: (a) biochar was produced at 500° C. under anoxic environments using corn straw as the feedstock due to its abundance in agricultural wastes; (b) biochar was dispersed in deionized water by sonication for 30 min to obtain a biochar suspension; (c) under N.sub.2 atmosphere, FeCl.sub.3.6H.sub.2O and FeSO.sub.4.7H.sub.2O were added into three-neck flask filled with deionized water with vigorous magnetic stir; (d) 25% ammonia was quickly added into the produced solution and followed by an addition of the prepared biochar suspension while stirring in a water bath; (e) after cooling to the room temperature, the product, magnetic biochar, was magnetically separated, washed by absolute ethanol and deionized water to remove impurities, and dried in a vacuum oven; (f) dodecyl tributyl phosphonium bromide (C.sub.24H.sub.52BrP) was slowly dissolved in deionized water in amounts of 1.0˜50.0 g, where magnetic biochar powder (1.0 g) was added into the above solutions under continuous stir overnight, then quaternary phosphonium salt was self-assembled with magnetic biochar after agitating at 60° C.˜70° C. The resulting precipitate, magnetic biochar-quaternary phosphonium salt was washed several times to remove unassembled bromonium ions, and vacuum-dried at in a vacuum oven.

[0044] The magnetic biochar-quaternary phosphonium salt not only has a high-efficiency bactericidal effect, but also adsorption and purification for waste water, and would be suitable for bactericidal disinfection in industrial circulating water, domestic sewage and recycling oilfield water.

[0045] The magnetic biochar-quaternary phosphonium salt for the control of microbial contamination in water will be better understood with reference to the following examples.

Example 1

Synthesis of Magnetic Biochar

[0046] According to the method mentioned in Chinese patent application No. CN200920232191.9, corn straw biochar (500° C.) was obtained: the corn straw was washed by tap water and deionized water successively, and oven-dried for 12 h at 80° C.

[0047] Then the dried straw was transferred into the biochar reactor under oxygen-limited conditions according to a stepwise heating program from 200° C. to 500° C. At each temperature node (such as 300° C., 400° C., 500° C.), the temperature was maintained for 1.5 h. When no further smoke was emitted from the gas exit pipe, the biochar reactor was closed. After cooling to room temperature, the prepared biochar was crushed and passed through a nylon sieve.

[0048] 1.0 g of biochar was placed in a beaker containing 100 mL deionized water, and vibrated in an ultrasonic cleaner (100 W) to obtain a well-mixed biochar suspension.

[0049] Under N.sub.2 atmosphere, 6.08 g FeCl.sub.3.6H.sub.2O and 4.17 g FeSO.sub.4.7H.sub.2O were added into three-neck flask filled with 100 mL deionized water with vigorous magnetic stir, followed by a quick addition of 10 mL 25% ammonia. After the reaction was stable, the biochar suspension was added, and the reaction was subject to the magnetic stir for 45 min at 85° C. in water bath. After cooling to room temperature, the magnetic biochar was obtained by magnetic separation.

[0050] The results showed that magnetic iron ions were loaded in the surface pores of biochar by scanning electron microscope (SEM) as shown in FIG. 1. It can be seen from FIG. 2 that the saturation magnetization of magnetic biochar at room temperature is 67.13 emu/g (curve 1).

[0051] As shown in FIG. 3 (XRD spectrum), five new produced diffraction peaks of magnetite at 2θ=30.1°, 35.4°, 43.1°, 53.4° and 56.9° were obvious (curve 1); the Fourier transform infrared (FTIR) spectrum (curve 1) shown in FIG. 4 further confirmed the existence of Fe—O characteristic peaks (630 and 586 cm.sup.−1); the thermogravimetric analysis test (curve 1) as shown in FIG. 5 showed that the magnetic biochar has good thermal stability, with only 6.64% material loss up to 800° C.

Example 2

Synthesis of Magnetic Biochar-Quaternary Phosphonium Salt with Mass Ratio of 1:1 (MBQ-1)

[0052] 1.0 g of magnetic biochar prepared in example 1 was taken into a beaker containing 200 mL deionized water. In the meanwhile, 1.0 g of dodecyl tributyl phosphonium bromide (C.sub.24H.sub.52BrP) was added into the above solutions under continuous stir overnight (12 h) at room temperature. After the full impregnation, dodecyl tributyl phosphonium bromide was self-assembled with magnetic biochar after agitating for 4 h at 65° C. After cooling to room temperature, the product was magnetically separated, washed several times until the pH of the washing liquid was neutral, and then placed in a vacuum drying oven (70° C., −0.06 MPa). Finally, the magnetic biochar-quaternary phosphonium salt with the mass ratio of 1:1 (MBQ-1) was obtained.

[0053] The saturation magnetization of MBQ-1 at room temperature was 75.27 emu/g (curve 2 in FIG. 2); as shown in FIG. 3 (XRD spectrum), the diffraction peaks of magnetite at 2θ=30.1°, 35.4°, 43.1°, 53.4° and 56.9° were also obtained (curve 2); in addition to the corresponding Fe—O characteristic peaks at 630 and 586 cm.sup.−1, new —CH.sub.2 stretching vibration peaks were generated at 2924 and 2856 cm.sup.−1 in FTIR spectrum (curve 2 in FIG. 4), which proved the successful loading of quaternary phosphonium salt into biochar. The thermogravimetric analysis test (curve 2 in FIG. 5) showed that there was 3.51% quaternary phosphonium salt loaded on the biochar.

Example 3

Synthesis of Magnetic Biochar-Quaternary Phosphonium Salt with Mass Ratio of 1:10 (MBQ-2)

[0054] 1.0 g of magnetic biochar prepared in example 1 was taken into a beaker containing 200 mL deionized water. In the meanwhile, 10.0 g of dodecyl tributyl phosphonium bromide (C.sub.24H.sub.52BrP) was added into the above solutions under continuous stir overnight (12 h) at room temperature. After the full impregnation, dodecyl tributyl phosphonium bromide was self-assembled with magnetic biochar after agitating for 4 h at 65° C. After cooling to room temperature, the product was magnetically separated, washed several times until the pH of the washing liquid was neutral, and then placed in a vacuum drying oven (70° C., −0.06 MPa). Finally, the magnetic biochar-quaternary phosphonium salt with the mass ratio of 1:10 (MBQ-2) was obtained.

[0055] The saturation magnetization of MBQ-2 at room temperature was 53.29 emu/g (curve 3 in FIG. 2); as shown in FIG. 3 (XRD spectrum), the diffraction peaks of magnetite at 2θ=30.1°, 35.4°, 43.1°, 53.4° and 56.9° were also obtained (curve 3); in addition to the corresponding Fe—O characteristic peaks at 630 and 586 cm.sup.−1 in FTIR spectrum (curve 3 in FIG. 4), the produced —CH.sub.2 stretching vibration peaks were strengthened at 2924 and 2856 cm.sup.−1. The thermogravimetric analysis test (curve 3 in FIG. 5) showed that there was 6.43% quaternary phosphonium salt loaded on the biochar.

Example 4

Synthesis of Magnetic Biochar-Quaternary Phosphonium Salt with Mass Ratio of 1:30 (MBQ-3)

[0056] 1.0 g of magnetic biochar prepared in Example 1 was taken into a beaker containing 200 mL deionized water. In the meanwhile, 30.0 g of dodecyl tributyl phosphonium bromide (C.sub.24H.sub.52BrP) was added into the above solutions under continuous stir overnight (12 h) at room temperature. After the full impregnation, dodecyl tributyl phosphonium bromide was self-assembled with magnetic biochar after agitating for 4 h at 60° C. After cooling to room temperature, the product was magnetically separated, washed several times until the pH of the washing liquid was neutral, and then placed in a vacuum drying oven (70° C., −0.06 MPa). Finally, the magnetic biochar-quaternary phosphonium salt with the mass ratio of 1:30 (MBQ-3) was obtained.

[0057] The saturation magnetization of MBQ-3 at room temperature was 52.74 emu/g (curve 4 in FIG. 2); similar characteristic peaks were also verified in the XRD spectrum (curve 4 in FIG. 3) and FTIR spectrum (curve 4 in FIG. 4), respectively. The results of thermogravimetric analysis (curve 4 in FIG. 5) further proved that the loading amount of quaternary phosphonium salt in MBQ-3 increased to 10.25%.

Example 5

Synthesis of Magnetic Biochar-Quaternary Phosphonium Salt with Mass Ratio of 1:50 (MBQ-4)

[0058] 1.0 g of magnetic biochar prepared in Example 1 was taken into a beaker containing 200 mL deionized water. In the meanwhile, 50.0 g of dodecyl tributyl phosphonium bromide (C.sub.24H.sub.52BrP) was added into the above solutions under continuous stir overnight (12 h) at room temperature. After the full impregnation, dodecyl tributyl phosphonium bromide was self-assembled with magnetic biochar after agitating for 4 h at 70° C. After cooling to room temperature, the product was magnetically separated, washed several times until the pH of the washing liquid was neutral, and then placed in a vacuum drying oven (70° C., −0.06 MPa). Finally, the magnetic biochar-quaternary phosphonium salt with the mass ratio of 1:50 (MBQ-4) was obtained.

[0059] The saturation magnetization of MBQ-4 at room temperature was 49.66 emu/g (curve 5 in FIG. 2); as shown in FIG. 3 (XRD spectrum), the diffraction peaks of magnetite at 2θ=30.1°, 35.4°, 43.1°, 53.4° and 56.9° were also obtained (curve 5). With the increase of mass ratio of quaternary phosphonium salt, the stretching vibration peak of —CH.sub.2 was significantly strengthened (curve 5 in FIG. 4), which indirectly indicated the increase of the loading amount of quaternary phosphonium salt.

[0060] The results of thermogravimetric analysis (curve 5 in FIG. 5) also showed that 18.88% of the quaternary phosphonium salt was loaded on the magnetic biochar.

Example 6

Determination of Slow-Release Behavior of Magnetic Biochar-Quaternary Phosphonium Salt

[0061] The synthesized composites of MBQ-1, MBQ-2, MBQ-3 and MBQ-4 (Example 2-5) were weighed 10 mg, respectively, added into centrifuge tubes containing 10 mL deionized water, and rotated on a rotating incubator at 25° C. Samples were taken at different times (6˜72 h), followed by filtering through 0.22-μm mixed cellulose membrane. Quaternary phosphonium salt concentration in the filtrate was quantified using an inductive coupled plasma (ICP) emission spectrometer (Agilent Technologies, USA).

[0062] The results showed that the release amount of quaternary phosphonium salt in curves 1˜4 (FIG. 6) increased with the increase of mass ratio of magnetic biochar to quaternary phosphonium salt. After 72 h rotary culture, the total release amount of quaternary phosphonium salt was 23.01, 66.57, 71.52 and 166.05 mg/L, respectively. The experiment identified that the material of this invention owned a good slow-release effect and a long-acting duration.

Example 7

Antibacterial Activity of Magnetic Biochar-Quaternary Phosphonium Salt

[0063] The representative strains used in the antibacterial activity test were ATCC 25922 Escherichia coli and ATCC 6538 Staphylococcus aureus, representing Gram-positive bacteria and Gram-negative bacteria, respectively. The bactericidal effect of magnetic biochar-quaternary phosphonium salt is tested according to AATCC-100 “shaking flask test method” and the determination method of bacteria and algae in industrial circulating cooling water (GB/T14643.2-2009). The bactericidal rate could reach to 50.46%˜100% with the oscillation frequency of 180 rpm.

[0064] Escherichia coli/Staphylococcus aureus with 4% inoculation amount were transferred to Luria-Bertani (LB) medium (10.0 g/L tryptone, 5.0 g/L yeast extract, 10.0 g/L sodium chloride, pH 7.4) for overnight cultivation (about 12 h); in the next day, the strain was streaked on LB agar medium and cultured in a constant temperature incubator at 37° C. for 24 h.

[0065] The purified single strain was selected and inoculated in LB medium by shaking at 37° C. to logarithmic-phase. After low speed centrifugation (5000 rpm/min, 10 min), the bacterial suspension was washed with sterile saline for three times, and adjusted the bacterial density to 10.sup.6 CFU/mL. Bactericidal materials with various dosages and loading ratios were added into above bacterial suspensions, and incubated in a thermostatic incubator (37° C.) at 180 rpm for 24 h. Then, aliquots (100 μL) of the diluted bacterial suspension were spread on LB agar plates and incubated at 37° C. for 24 h to count the numbers of colonies.

[0066] The antibacterial ratio (R) was calculated according to the following equation (1):

R (%)=(A.sub.0−A.sub.1)/A.sub.0×100  (1),

[0067] wherein A.sub.0 and A.sub.1 were defined as the number of colonies incubated with the untreated and treated samples, respectively.

[0068] The bactericidal effect of bactericidal materials with various dosage and loading ratios are shown in Table 1.

TABLE-US-00001 TABLE 1 The bactericidal effect of bactericidal materials with various dosage and loading ratios Bacteria Material 20 mg/L (%) 50 mg/L (%) 100 mg/L (%) 200 mg/L (%) Escherichia MBQ-1 50.46 ± 9.38  54.17 ± 10.56  56.02 ± 4.31  61.00 ± 4.07 coli (1:1) MBQ-2 98.31 ± 0.31  99.78 ± 0.01  99.98 ± 0.01 100.00 ± 0.00 (1:10) MBQ-3 99.12 ± 0.26  99.95 ± 0.01 100.00 ± 0.00 100.00 ± 0.00 (1:30) MBQ-4 99.93 ± 0.02 100.00 ± 0.00 100.00 ± 0.00 100.00 ± 0.00 (1:50) Staphylococcus MBQ-1 55.89 ± 4.36  91.62 ± 0.28  98.69 ± 0.30  99.95 ± 0.02 aureus (1:1) MBQ-2 100.00 ± 0.00  100.00 ± 0.00 100.00 ± 0.00 100.00 ± 0.00 (1:10) MBQ-3 100.00 ± 0.00  100.00 ± 0.00 100.00 ± 0.00 100.00 ± 0.00 (1:30) MBQ-4 100.00 ± 0.00  100.00 ± 0.00 100.00 ± 0.00 100.00 ± 0.00 (1:50)

[0069] The results in Table 1 showed that the magnetic biochar-quaternary phosphonium salt of this invention had a good bactericidal efficacy. As shown in FIG. 7 and FIG. 8, magnetic biochar-quaternary phosphonium salt can effectively damage the membrane structure of pathogenic bacteria, and make the intracellular substances that maintain physiological activities flow out, resulting in the abnormal subcellular structure and microbial death.

[0070] According to the above determination method, the bactericidal effect of the magnetic biochar in Example 1 was determined, and the results were shown in Table 2.

TABLE-US-00002 TABLE 2 The bactericidal effect of magnetic biochar with various dosage Bacteria 20 mg/L (%) 50 mg/L (%) 100 mg/L (%) 200 mg/L (%) Escherichia coli 27.66 ± 4.07 50.00 ± 3.91  45.14 ± 3.66 50.35 ± 5.93 Staphylococcus 18.23 ± 5.96 24.87 ± 15.73 49.65 ± 5.03 89.12 ± 3.14 aureus

[0071] The results in Table 2 showed that the combination of magnetic particles and biochar had a certain bactericidal effect, which significantly enhanced the bactericidal effect of magnetic biochar-quaternary phosphonium salt.

Example 8

Regeneration of Magnetic Biochar-Quaternary Phosphonium Salt and Bactericidal Effect Test

[0072] The bactericidal materials prepared in Examples 2-5 were used for antibacterial activities. After the bactericidal processes, the bactericidal materials were fixed by an external magnet and separated from the solution. Then the bactericidal materials were washed with deionized water for 2-3 times, and the recovered materials were dried in a vacuum drying oven.

[0073] The regenerative magnetic biochar-quaternary phosphonium salt bactericidal materials were obtained according to the preparation method of Examples 2-5. The bactericidal effect of the regenerative magnetic biochar-quaternary phosphonium salt was evaluated, and the determination process was basically the same as Example 7.

[0074] The comparison results of bactericidal effect between the regenerative material and first prepared material were shown in Table 3.

TABLE-US-00003 TABLE 3 The comparison results of bactericidal effect between the regenerative material and first prepared material Preparation 20 mg/L 50 mg/L 100 mg/L 200 mg/L Bacteria sequence Material (%) (%) (%) (%) Escherichia First MBQ-1 50.46 ± 9.38  54.17 ± 10.56  56.02 ± 4.31  61.00 ± 4.07 coli prepared (1:1) MBQ-2 98.31 ± 0.31 99.78 ± 0.01  99.98 ± 0.01 100.00 ± 0.00 (1:10) MBQ-3 99.12 ± 0.26 99.95 ± 0.01 100.00 ± 0.00 100.00 ± 0.00 (1:30) MBQ-4 99.93 ± 0.02 100.00 ± 0.00  100.00 ± 0.00 100.00 ± 0.00 (1:50) Regenerative MBQ-1 44.33 ± 3.66 78.82 ± 2.36  95.95 ± 2.71  98.03 ± 1.56 (1:1) MBQ-2 99.21 ± 3.55 99.81 ± 2.43 100.00 ± 0.00 100.00 ± 0.00 (1:10) MBQ-3 100.00 ± 0.00  100.00 ± 0.00  100.00 ± 0.00 100.00 ± 0.00 (1:30) MBQ-4 100.00 ± 0.00  100.00 ± 0.00  100.00 ± 0.00 100.00 ± 0.00 (1:50)

[0075] The comparison results showed that the bactericidal effect of the regenerative material was significantly better than that of the first prepared material. That might be due to the residual covalent bonding quaternary phosphonium salt attached into the recovered materials, and the regeneration process improved the loading amount of quaternary phosphonium salt on the magnetic biochar. This regeneration method can not only effectively recover the bactericidal material, but also significantly enhance the bactericidal effect of the regenerated complex material.

Comparative Example

Comparison of Bactericidal Effect Between Magnetic Biochar-Quaternary Phosphonium Salt and Other Bactericidal Materials

[0076] The comparison results of bactericidal effect between magnetic biochar-quaternary phosphonium salt and other bactericidal materials were shown in Table 4.

TABLE-US-00004 TABLE 4 The comparison results of bactericidal effect between magnetic biochar- quatemary phosphonium salt and other bactericidal materials Concentration Bactericidal effect of Bactericidal effect of Material (mg/L) Escherichia coli (%) Staphylococcus aureus (%) Ag—CoFe.sub.2O.sub.4-GO 50 99.80 99.40 Ps/Ag 500 95.00 90.00 HNTs-CS@Ag 180 94.00 92.60 GO-1227 10 99.98 99.97 PTQ 1000 94.40 99.50 MBQs 20 99.93 100

[0077] In the prior art, graphene oxide is used as the carrier of bactericidal material, which has a high bactericidal effect. For example, inorganic Ag—CoFe.sub.2O.sub.4-GO and organic GO-1227, fabricated by the carrier of graphene oxide, showed high antibacterial capacities, which only need the dosages of 50 and 10 mg/L, respectively, to remove the bacteria (up to 10.sup.6 CFU/mL) in water. Although graphene oxide carrier has excellent germicidal efficacy, it is difficult to be widely used in practical production due to its high cost. The simple synthesis of polystyrene silver nanoparticles (PS/Ag), abundant resources of chlorinated natural rubber quaternary ammonium salt (PTQ), and low-cost fabrication of chitosan silver nanocomposites (HNTs-CS@Ag) have been designed as new antibacterial agents, however, the actual dosages in disinfection are relatively large, up to 500, 1000 and 180 mg/L, respectively.

[0078] In view of the technical defects of the bactericidal material at the present stage, the magnetic biochar-quaternary phosphonium salt was prepared using the common biomass as raw materials, combining with a simple and mild preparation method. The results showed that only 20 mg/L was enough to remove pathogens in water environment, and the magnetic property for easy separation facilitated the water purification and reuse of antibacterial materials. This patent is expected to provide a new perspective for solving the pathogen pollution in water environment and improving the level of environmental health and safety.