Malic acid and KMnO.SUB.4.-based combined and modified cow dung biogas residue hydrochar preparation method

Abstract

A malic acid and KMnO4-based combined and modified cow dung biogas residue hydrochar preparation method, comprising: mixing a cow dung biogas residue with malic acid, and performing ultrasonic treatment to obtain a malic acid modified cow dung biogas residue; performing a hydrothermal reaction with KMnO4 in a high-temperature high-pressure reactor to obtain a combined and modified cow dung biogas residue hydrochar material.

Claims

1. A method for preparing hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue, comprising the following steps: 1) mixing cow dung biogas residue and malic acid solution homogeneously and then performing ultrasonic treatment, to obtain malic acid modified cow dung biogas residue; 2) adding KMnO.sub.4 solution to the malic acid modified cow dung biogas residue obtained in the step 1), mixing homogenously and then performing a hydrothermal reaction, to obtain the hydrothermal carbon based on cow dung biogas residue; wherein, the filling degree of reactor of hydrothermal reaction is 60%˜80%.

2. The method for preparing hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue according to claim 1, wherein, the cow dung biogas residue has 7%˜10% moisture content and is filtered through a 20-mesh screen in the step 1).

3. The method for preparing hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue according to claim 1, wherein, the ultrasonic treatment is performed at 35˜85° C., 40 KHz and 100 W for 40˜90 min.

4. The method for preparing hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue according to claim 1, wherein, the concentration of the malic acid solution is 0.5˜1.0 mol.Math.L.sup.−1, and the solid to liquid ratio of the cow dung biogas residue to the malic acid is 1:6˜1:10.

5. The method for preparing hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue according to claim 1, wherein, the concentration of the KMnO.sub.4 solution is 0.13˜0.25 mol.Math.L.sup.−1, and the solid to liquid ratio of the malic acid modified cow dung biogas residue to the KMnO.sub.4 solution is 1:5˜1:10.

6. The method for preparing hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue according to claim 1, wherein, the reaction temperature of the hydrothermal reaction is 180˜220° C., the reaction time is 2˜3 h, and the heating rate is 1˜5° C..Math.min.sup.−1.

Description

IV. DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows scanning electron microscope (SEM) images of hydrothermal carbon based on modified cow dung biogas residue and hydrothermal carbon based on unmodified cow dung biogas residue;

(2) In the figure: (a) unmodified hydrothermal carbon; (b) modified hydrothermal carbon.

(3) FIG. 2 shows schematic diagram of adsorption effects of hydrothermal carbon based on modified cow dung biogas residue and hydrothermal carbon based on unmodified cow dung biogas residue for ammonia nitrogen (NH.sub.4.sup.+—N) at different initial concentrations;

(4) FIG. 3 shows schematic diagram of kinetic effects of adsorption of hydrothermal carbon based on modified cow dung biogas residue and hydrothermal carbon based on unmodified cow dung biogas residue for ammonia nitrogen (NH.sub.4.sup.+—N);

(5) FIG. 4 shows schematic diagram of adsorption effects of hydrothermal carbon based on modified cow dung biogas residue and hydrothermal carbon based on unmodified cow dung biogas residue for ammonia nitrogen (NH.sub.4.sup.+—N) at different initial concentrations in actual waste water in a pig farm.

V. EMBODIMENTS

(6) Hereunder the present invention will be fully described in the following examples. However, it should be noted that the involved specific parameters are provided only for the purpose of fully exhibiting the features and advantages of the present invention, and those skilled in the art can realize further popularization and application without departing from the connotation of the present invention.

(7) Please see the document “Hongmei Jin, Guangqing Fu, Zhizhou Chang, Xiaomei Ye, Guangyin Chen, Jing Du, Form Transformation of Nitrogen in Anaerobic Fermentation of Pig Manure and Cow Dung and Distribution of Nitrogen in Biogas Slurry and Biogas Residue, Journal of Agricultural Engineering” for the source of the cow dung biogas residue in the examples; the cow dung biogas residue is naturally air-dried or oven-dried at 60˜70° C. to 7%˜10% moisture content, milled, and then filtered through a 20-mesh screen.

Example 1. Preparation of Hydrothermal Carbon Based on Male Acid and KMnO.SUB.4 .Combined Modified Cow Dung Biogas Residue

(8) Experimental Group:

(9) 1) 0.5 mol.Math.L.sup.−1 malic acid solution is added into an appropriate amount of cow dung biogas residue at 1:10 solid to liquid ratio (w/v, kg/L) (in the specific implementation, the solid to liquid ratio of the cow dung biogas residue to the malic acid may be selected within a range of 1:6˜1:10), after uniform mixing, the mixture is treated by ultrasonic treatment at 50° C. for 60 minutes (40 KHz, 100 W); the obtained solid-liquid mixture is filtered, washed with water till the eluate is neutral, and then dried at 55˜80° C.; thus, malic acid modified cow dung biogas residue is obtained; 2) The malic acid modified cow dung biogas residue obtained in the step 1) is mixed with 0.1367 mol.Math.L.sup.−1 KMnO.sub.4 solution (in the specific implementation, the concentration may be within a range of 0.13˜0.25 mol/L) at 1:8 solid to liquid ratio (w/v, kg/L) (in the specific implementation, the solid to liquid ratio of the malic acid modified cow dung biogas residue to the KMnO.sub.4 solution may be selected within a range of 1:5˜1:10) to a homogeneous state, and then the mixture is subjected to a hydrothermal reaction at 220° C. for 2 h with 1˜5° C..Math.min.sup.−1 heating rate in a high temperature and high pressure reactor; after the reaction is finished, the reaction product is cooled down, washed with water till the eluate is essentially neutral, filtered, and dried at 55˜80° C.; thus, hydrothermal carbon based on malic acid and KMnO.sub.4 combined modified cow dung biogas residue (G-HTC) is obtained;

(10) Control group: an appropriate amount of cow dung biogas residue powder is fully mixed with deionized water at 1:8 solid to liquid ratio (w/v), then the mixture is subjected to a hydrothermal reaction at 220° C. for 2 h with 1˜5° C..Math.min.sup.−1 heating rate in a high temperature and high pressure reactor, after the reaction is finished, the reaction product is cooled down, washed with water till the eluate is essentially neutral, filtered, and dried at 55˜80° C.; thus, hydrothermal carbon based on unmodified (control group) cow dung biogas residue (Y-HTC) is obtained.

(11) The elemental composition and specific surface area of G-HTC and Y-HTC are shown in Table 1 respectively: please see the document “Hongmei Jin, Sergio Capareda, Zhizhou Chang, Jun Gao, Yueding Xu, Jianying Zhang, Biochar Pyrolytically Produced from Municipal Solid Wastes for Aqueous As (V) Removal: Adsorption Property and Its Improvement with KOH Activation. Bioresouree Technology” for the determination method.

(12) TABLE-US-00001 TABLE 1 Specific Surface Area and Elemental Composition of Hydrothermal Carbon Based on Cow Dung Biogas Residue Specific Total pore Average pore Sample Elemental composition (%) surface area volume diameter No. C H O N S (m.sup.2 .Math. g.sup.−1) (cm.sup.3 .Math. g.sup.−1) (nm) Y-HTC 39.81 4.26 21.15 1.86 — 5.52 3.1 × 10.sup.−2 22.27 G-HTC 44.79 4.95 23.30 1.85 — 15.44 9.4 × 10.sup.−2 24.34

(13) As can be seen from Table 1, the pores of G-HTC and Y-HTC are mainly mesopores, and the specific surface area of G-HTC is significantly increased compared with that of Y-HTC, almost by 179.78%; the C/O content is at the top position in Y-HTC and G-HTC, and the C/O content in G-HTC is higher than that in Y-HTC.

(14) The scanning electron microscope (SEM) images of G-HTC and Y-HTC are shown in FIG. 1. As shown in FIG. 1, the surface of the unmodified hydrothermal carbon Y-HTC (FIG. 1a) has long trenches and has less pores; the surface of the modified hydrothermal carbon G-HTC (FIG. 1b) has obviously improved porosity and is in a cellular form.

(15) In the specific implementation process, the ultrasonic treatment in the step 1) may be performed within a temperature range of 35˜85′C, at 40 KHz, with a power of 100 W, for 40˜90 minutes, in order to attain the object of the present invention;

(16) The hydrothermal reaction may be performed at 180˜220° C. for 2˜3 h with 1˜5° C./min heating rate, in order to attain the object of the present invention.

Example 2

(17) 0.3 g G-HTC obtained in the example 1 is weighed and loaded into a 250 mL conical flask, and 100 mL ammonia nitrogen (NH.sub.4.sup.+—N) solution at different concentrations (20 mg.Math.L.sup.−1, 50 mg.Math.L.sup.−1, or 100 mg.Math.L.sup.−1) is added into the conical flask respectively; each experiment is repeated for three times; the mixture is shaken on a constant temperature shaking table (28° C., 220r.Math.min.sup.−1) for 3 h to achieve adsorption equilibrium, then the supernatant is taken and filtered through a 0.45 μm filter membrane, the concentration of ammonia nitrogen (NH.sub.4.sup.+—N) in the filtrate is measured with an ultraviolet-visible spectrophotometer; at the same time, the Y-HTC obtained in the example 1 is treated with the same steps described above for comparison.

(18) The experimental results are shown in FIG. 2. As can be seen, the adsorption effect of G-HTC and Y-HTC for ammonia nitrogen (NH.sub.4.sup.+—N) is increased as the initial concentration of ammonia nitrogen is increased; in addition, when the concentration of ammonia nitrogen (NH.sub.4.sup.+—N) is 100 mg.Math.L.sup.−1, the adsorptive capacity of G-HTC is as high as 9.83 mg.Math.g.sup.−1, while the adsorptive capacity of Y-HTC is only 0.81 mg.Math.g.sup.−1, indicating that the hydrothermal carbon based on modified cow dung biogas residue has better adsorptive capacity for ammonia nitrogen (NH.sub.4.sup.+—N).

Example 3

(19) 0.3 g G-HTC obtained in the example 1 is weighed and loaded into a 250 mL conical flask, 100 mL ammonia nitrogen (NH.sub.4.sup.+—N) solution at 100 mg.Math.L.sup.−1 concentration is added into the conical flask, the mixture is shaken on a constant temperature shaking table (28° C., 220r.Math.min.sup.−1), the supernatant is taken at different sampling times (0, 15, 30, 60, 90, 120, 150, 180 min) and filtered through a 0.45 μm filter membrane, the concentration of ammonia nitrogen (NH.sub.4.sup.+—N) in the filtrate is measured with an ultraviolet-visible spectrophotometer; at the same time, the Y-HTC is treated with the same steps described above for comparison.

(20) The detection results are shown in FIG. 3. as can be seen, the maximum adsorptive capacity of G-HTC for ammonia nitrogen (NH.sub.4.sup.+—N) is 12.21 times of that of Y-HTC, and both G-HTC and Y-HTC achieve adsorption saturation within 60 min.

Example 4

(21) 0.3 g G-HTC obtained in the example 1 is weighed and loaded into a 250 mL conical flask, and 100 mL dilute solution of waste water from a pig farm (taken from a sedimentation tank in the pig farm, the NH.sub.4.sup.+—N concentration of the stock solution is about 200 mg.Math.L.sup.−1) is added into the conical flask, i.e., the stock solution is diluted with water so that the NH.sub.4.sup.+—N concentration of the waste water is 20, 50, and 100 mg.Math.L.sup.−1 respectively; the mixture is shaken on a constant temperature shaking table (28° C., 220r.Math.min.sup.−1) for 3 h, the supernatant is taken and filtered through a 0.45 μm filter membrane, and the NH.sub.4.sup.+—N concentration in the filtrate is measured with an ultraviolet-visible spectrophotometer, at the same time, the Y-HTC is treated with the same steps described above for comparison.

(22) The detection results are shown in FIG. 4. As can be seen, the maximum adsorptive capacity of G-HTC for ammonia nitrogen (NH.sub.4.sup.+—N) is 9.51 times of that of Y-HTC.

(23) Those skilled in the art can understand that all terms used herein (including technical terms and scientific terms) are intended to have the common meanings that are comprehended by those having ordinary skills in the art to which the present invention belongs, unless otherwise defined.

(24) It should also be understood that those terms defined in general dictionaries should be understood as having meanings in line with their meanings in the context of the prior art, and should not be comprehended with meanings that are too ideal or formal, unless otherwise defined herein.

(25) While the object, technical scheme, and beneficial effects of the present invention are described in detail in the above specific embodiments, it should be understood that those embodiments are just specific embodiments of the present invention, without constituting any limitation to the present invention. Any modification, equivalent replacement, or improvement made without departing from the spirit and principle of the present invention shall be deemed as falling in the scope of protection of the present invention.