Method for preparing phosphorus removal adsorbent by utilizing ultrasonic-assisted hemicellulase method and application

Abstract

The invention discloses a method for preparing a phosphorus removal adsorbent by using an ultrasonic-assisted hemicellulase method and application, the preparation method comprises the following steps: cooking dried shaddock peel in boiling water for a period of time, treating the cooked shaddock peel in a hemicellulase solution for a period of time, and then washing the shaddock peel to be neutral; placing the pomelo peel washed to be neutral in an ultrasonic instrument for enzyme deactivation treatment, filtering after treatment, adding absolute ethyl alcohol for decoloration treatment, and filtering and cleaning after treatment to obtain a semi-finished product; and drying the semi-finished product to constant weight, and crushing to obtain the phosphorus removal adsorbent. The optimized shaddock peel powder obtained through ultrasonic-assisted hemicellulase treatment has a relatively strong adsorption effect on phosphorus-containing wastewater. The waste shaddock peel is used as a cheap adsorption material, has the advantages of wide raw material source, low cost budget and high adsorption rate, and can be used as a novel biological adsorbent to realize high-valued utilization of agricultural product processing byproducts.

Description

Technical Field

[0001] The invention relates to the technical field of adsorbents, and more particularly to a method for preparing a dephosphorus adsorbent by utilizing an ultrasound-assisted hemicellulase method and its application. Background Art

[0002] Plant nutrients mainly include inorganic non-metallic elements such as nitrogen and phosphorus, especially phosphorus. Phosphorus is considered to be the main limiting factor that causes eutrophication of water bodies. With the rapid development of the country's chemical industry, the eutrophication of water bodies is becoming increasingly serious. Reducing the degree of eutrophication of water bodies, thereby ensuring the safety of people's drinking water, reducing the discharge of phosphorus-containing wastewater, and taking strong measures to effectively control it are the main ways to reduce phosphorus pollution in water bodies.

[0003] At present, the commonly used phosphorus removal methods include chemical precipitation, ion exchange, biological method, adsorption method and membrane separation method. Biological method and chemical precipitation method are the most widely used methods. Chemical precipitation method has the advantages of high efficiency, simple operation and higher efficiency, but it requires the addition of a large amount of reagents, the cost is high, and it is not suitable for some small factories. In addition, the water content of sludge increases significantly after phosphorus removal, which is easy to cause secondary pollution. Compared with chemical precipitation method, biological method produces less sludge, has a wider range of phosphorus removal, and has lower cost, but the operating conditions are more stringent, and the effluent quality is often unstable. The total phosphorus content often cannot meet the sewage discharge standard, and deep treatment is required to achieve further removal. The most ideal phosphorus removal method is adsorption method. Its most significant features are high efficiency and low consumption, large adsorption capacity, stable adsorbent performance, and easy recycling and regeneration. It can be used to recover phosphates.

[0004] Grapefruit is one of the fruits grown in southern my country. Grapefruit peel accounts for about 50% of the total weight of grapefruit, mainly containing cellulose, hemicellulose, pectin and pigments. The natural sponge-like structure is an excellent choice for wastewater adsorbents. A large number of experimental studies have shown that the modification of grapefruit peel provides a good prospect for the preparation of biosorbents with excellent adsorption performance.

[0005] With the continuous improvement of social production level, urban water pollution, pesticide wastewater pollution, industrial wastewater, etc. are closely related to the quality of human living environment and have become the top priority treatment problems in the world. Therefore, how to provide a low-consumption, high-efficiency, and environmentally friendly preparation method for phosphorus removal adsorbent is a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0006] In view of this, the present invention provides a method and application of preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method. The present invention uses waste pomelo peel as experimental raw materials to prepare an adsorbent that meets the public consumption concept to meet the national wastewater discharge standard.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for preparing a phosphorus removal adsorbent using an ultrasound-assisted hemicellulase method comprises the following steps:

[0009] (1) Pretreatment

[0010] Put the dried pomelo peel into boiling water and steam for a while, set aside;

[0011] (2) Enzymatic hydrolysis

[0012] The steamed grapefruit peel is placed in a hemicellulase solution for a period of time, and then the grapefruit peel is rinsed to neutrality;

[0013] (3) Enzyme inactivation and decolorization

[0014] The washed pomelo peel is placed in an ultrasonic instrument for enzyme inactivation treatment, filtered after treatment, and then anhydrous ethanol is added for decolorization treatment, filtered and washed after treatment to obtain a semi-finished product;

[0015] (4) Drying

[0016] The semi-finished product is dried to constant weight and crushed to obtain a phosphorus removal adsorbent.

[0017] Preferably, the cooking time is 25-35 minutes.

[0018] Preferably, the mass concentration of the hemicellulase solution is 0.4%.

[0019] Preferably, the enzymatic hydrolysis time is 12 h.

[0020] Preferably, the parameters of the enzyme inactivation treatment include: pH=2.5 buffer solution, enzyme inactivation treatment at 80°C, 200W for 30 minutes.

[0021] Preferably, the decolorization time is 18 hours.

[0022] Another object of the present invention is to provide the use of the phosphorus removal adsorbent prepared by the above-mentioned method of preparing the phosphorus removal adsorbent using the ultrasound-assisted hemicellulase method in treating phosphorus-containing wastewater.

[0023] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0024] The optimized pomelo peel powder obtained by ultrasound-assisted hemicellulase treatment in the present invention has a strong adsorption effect on phosphorus-containing wastewater. As a cheap adsorption material, waste pomelo peel has a wide range of raw material sources, a low cost budget, and a high adsorption rate. It can be used as a new type of biosorbent to achieve high-value utilization of agricultural product processing by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0026] Figure 1 is the standard curve of potassium dihydrogen phosphate;

[0027] Figure 2 This is the influence curve of the addition amount on the adsorption effect;

[0028] Figure 3 This is the curve of the effect of particle size on adsorption effect;

[0029] Figure 4 This is the influence curve of the initial phosphate concentration on the adsorption effect;

[0030] Figure 5 This is the influence curve of temperature on adsorption effect;

[0031] Figure 6 This is the influence curve of adsorption time on adsorption effect;

[0032] Figure 7 This is the curve of the effect of solution pH on adsorption effect;

[0033] Figure 8 This is a comparison chart of the adsorption effect of phosphate on various materials;

[0034] Fig. 9 is the infrared spectrum curve;

[0035] Fig.10 The potential particle size changes of grapefruit peel powder in different states, among which 1 is modified grapefruit peel, 2 is original grapefruit peel, and 3 is modified grapefruit peel after adsorption;

[0036] Fig.11 It is the desorption experimental curve;

[0037] Fig.12 is the phosphate adsorption isotherm;

[0038] Fig.13 It is a linear Langmuir adsorption isotherm;

[0039] Fig.14 It is a linear Freundlich adsorption isotherm;

[0040] Fig.15 is the adsorption kinetic curve of potassium dihydrogen phosphate;

[0041] Fig.16 is a quasi-first-order equation curve;

[0042] Fig.17 It is a quasi-second-order equation curve. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] This embodiment provides a method for preparing a phosphorus removal adsorbent using an ultrasound-assisted hemicellulase method, comprising the following steps:

[0046] (1) Pretreatment

[0047] Put the dried pomelo peel into boiling water and boil for 30 minutes, and set aside;

[0048] (2) Enzymatic hydrolysis

[0049] The steamed grapefruit peel was placed in a 0.4% hemicellulase solution for 12 h, and then the grapefruit peel was rinsed until neutral;

[0050] (3) Enzyme inactivation and decolorization

[0051] The washed pomelo peel is placed in an ultrasonic instrument for enzyme inactivation treatment (enzyme inactivation conditions: pH = 2.5 buffer solution, 80 ° C, 200W enzyme inactivation treatment for 30 minutes), filtered after treatment, and then added with anhydrous ethanol for decolorization for 18 hours, filtered after treatment, washed, and obtained a semi-finished product;

[0052] (4) Drying

[0053] The semi-finished product is dried to constant weight and crushed to obtain a phosphorus removal adsorbent.

[0054] Example 2

[0055] Adsorption experiments

[0056] Drawing of the standard curve of potassium dihydrogen phosphate

[0057] (1) Accurately weigh 0.5g of KH2PO4 solid particles into a small beaker, add a small amount of distilled water, stir evenly with a glass rod, and then pour into a 1000ml volumetric flask. Wash the beaker 2-3 times, pour into the volumetric flask, and continue to add distilled water. When the distance from the scale is 1-2cm, use a rubber-tipped dropper to adjust the volume to the scale line, shake well, and let it stand. Prepare a 500mg / L solution for use.

[0058] (2) Use a pipette to draw 4 mL of the reserve solution into a 100 mL volumetric flask and dilute to volume to prepare a 20 mg / L phosphate solution. Use the same method to dilute to prepare 35 mg / L phosphate solution, 50 mg / L phosphate solution, 65 mg / L phosphate solution, 80 mg / L phosphate solution, and 100 mg / L phosphate solution.

[0059] (3) Using distilled water as a blank control, measure the absorbance of solutions of different concentrations in each cuvette at room temperature at a UV-visible light wavelength of λ = 650nm, and draw a standard curve for phosphate with C (phosphate) as the abscissa and absorbance value (ABS) as the ordinate. The results are shown in Tables 1 and Figure 1 :

[0060] Table 1

[0061]

[0062] Determination of optimal adsorption parameters by single factor experiment

[0063] With particle size 80 mesh, mass 0.5 g, time 60 min, temperature 30 ° C, initial concentration 50 mg / L, pH = 7 as basic parameters, six groups of single factor experiments were designed. After the adsorption, the absorbance of each supernatant was measured, and the adsorption rate and adsorption amount were calculated.

[0064] a. Effect of powder addition amount on adsorption effect

[0065] Except for the amount of grapefruit peel powder added, the rest were prepared according to the basic parameters, and the mass of grapefruit peel powder was set to 0.2g, 0.3g, 0.4g, 0.5g, and 0.6g for adsorption experiments. Figure 2 The adsorption rate and adsorption amount both increase with the addition amount. When the optimized addition amount of grapefruit peel powder is greater than 0.5g, it basically stabilizes. 0.5g is determined to be the optimal addition amount.

[0066] b. Effect of powder particle size on adsorption effect

[0067] Except for the particle size of grapefruit peel powder, the rest were prepared according to the basic parameters, and the powder particle size was set to 20 mesh, 40 mesh, 60 mesh, 80 mesh, and 100 mesh for adsorption experiments. Figure 3The adsorption rate and adsorption amount increase with the increase of mesh size. Considering the economic cost, 80 mesh is determined to be the best.

[0068] c. Effect of initial phosphate concentration on adsorption effect

[0069] Except for the initial concentration, the rest were prepared according to the basic parameters, and the concentrations were set to 20mg / L, 35mg / L, 50mg / L, 65mg / L, and 80mg / L for adsorption experiments. Figure 4 The adsorption effect is best when the concentration is 50 mg / L, the adsorption rate is 94.22%, and the adsorption amount is positively correlated with the concentration.

[0070] d. Effect of temperature on adsorption

[0071] Except for the temperature, all other parameters were prepared according to the basic parameters, and the temperature was set at 20℃, 30℃, 40℃, 50℃, and 60℃ for adsorption experiments. Figure 5 The adsorption amount and adsorption rate are inversely correlated with temperature. Too high temperature will reduce the adsorption effect. Finally, 20℃ was selected as the optimal adsorption temperature.

[0072] e. Effect of time on adsorption effect

[0073] Except for the time, all other parameters were prepared according to the basic parameters, and the time was set to 15min, 30min, 45min, 60min, and 75min to conduct adsorption experiments. Figure 6 The adsorption effect is positively correlated with time. When the adsorption time is greater than 60 minutes, the adsorption effect is basically in equilibrium, saving time, and 60 minutes is determined to be the optimal time.

[0074] f. Effect of solution pH on phosphate adsorption

[0075] Except for the different pH of phosphate, the rest were prepared according to the basic parameters, and the pH was adjusted to 5-9 with a gradient of 1 for adsorption experiments. Figure 7 , at pH 8, the phosphate adsorption effect is best.

[0076] Comparative experiment

[0077] The modified pomelo peel powder prepared in Example 1 was used as an experimental example, and the original pomelo peel powder, activated carbon, strongly acidic cation exchange resin, and diatomaceous earth were used as comparative examples to conduct an adsorption experiment. The adsorption parameters are shown in Table 2:

[0078] 0.5g of original pomelo peel powder, diatomaceous earth, activated carbon, exchange resin, and optimized pomelo peel powder were added to each beaker, and the initial phosphate concentration was 50mg / L, and the adsorption was allowed to stand at room temperature. After filtration, the supernatant was taken and the ABS value was measured. This was repeated three times, and the average adsorption rate of each adsorption material was calculated.

[0079] Table 2

[0080]

[0081] Adsorption effect Figure 8 The adsorption effects are as follows: modified pomelo peel powder > activated carbon > diatomaceous earth > exchange resin > original pomelo peel powder. Considering many aspects, the value of modified pomelo peel powder is higher than that of activated carbon.

[0082] Elemental analysis

[0083] The original grapefruit peel, the optimal modified grapefruit peel, and the modified grapefruit peel after adsorption were analyzed by an element analyzer, and the element contents obtained are shown in Table 3:

[0084] Table 3

[0085]

[0086] It can be seen from the above table that the contents of C, H, N, and S elements have changed after modification, indicating that the modification treatment may change the number of polar groups such as C=N groups and -COOH in the original material, which plays an important role in the adsorption of phosphorus. The H content of the modified grapefruit peel has increased, indicating that the modification has increased the number of -OH and other groups in the material, which will effectively adsorb phosphorus-containing wastewater to a large extent.

[0087] Infrared spectrum analysis

[0088] See also Fig. 9 , as can be seen from the figure:

[0089] C: The infrared spectrum of the original pomelo peel powder shows that 3449.34 cm -1 There is -OH stretching vibration at the , indicating that grapefruit peel contains -OH.

[0090] B: Before modification and adsorption, 3420.73cm -1 The -OH stretching vibration indicates that the modification will expose more -OH.

[0091] A: After modified adsorption, 3420.66cm -1 The -OH stretching vibration indicates that some -OH groups play a certain role in the adsorption of phosphate on grapefruit peel.

[0092] Particle size analysis

[0093] Through Zeta potential and particle size analysis Fig.10 ,It can be seen that the potential and particle size have changed significantly before and after the modification of grapefruit peel, indicating that the modified grapefruit peel may have a certain adsorption effect.

[0094] Desorption regeneration cycle

[0095] Desorption experiments were carried out on modified grapefruit peel. Fig.11 It can be seen that as the number of adsorption times increases, the phosphate adsorption rate gradually decreases. After 5 desorptions, the adsorption rate is still greater than 60%, and the adsorption capacity exceeds 1.183 mg / g. After 5 times, both the adsorption rate and the adsorption capacity are on a downward trend. In summary, the modified pomelo peel can be reused for phosphate adsorption, but it cannot be reused infinitely.

[0096] Adsorption mechanism

[0097] Adsorption isotherm

[0098] Linear Langmuir equation:

[0099] Linear Freundlich equation: lgq = lgK + (1 / n)lgC

[0100] where C—adsorption equilibrium concentration (mg / L); q—adsorption capacity (mg / g); q m —saturation adsorption capacity (mg / g); b—adsorption equilibrium constant; K—constant at a certain temperature; 1 / n—adsorption index

[0101] At room temperature, with the phosphate adsorption capacity q (mg / g) as the ordinate and the equilibrium concentration C (mg / L) as the abscissa, an adsorption isotherm curve is plotted, as shown in Figure 12-14 ;

[0102] From Fig.13 , Fig.14 it can be seen that the R L 2 of the Langmuir isotherm is 0.9425, and the R F 2 of the Freundlich isotherm is 0.9994. R F 2 >R L 2 . It can be seen that the adsorption of phosphate by the modified pomelo peel conforms to the adsorption law of the Freundlich model and is more inclined to the adsorption mode of multi-layer adsorption in terms of the adsorption state. Generally, n can be used as an index of the adsorption strength of the adsorbent. When 0.1 < n < 0.5, it is conducive to adsorption; when 1 / n > 2, it is difficult to adsorb. In the fitting equation, 1 / n = 0.6116, indicating that the adsorption behavior is conducive to occurrence.

[0103] Table 4

[0104]

[0105] Adsorption kinetic curve

[0106] The adsorption kinetics was analyzed and studied using the following two rate equations:

[0107] Pseudo-first-order kinetic model: lg(Qq)=lgQ-K1t / 2.303

[0108] Pseudo-second-order kinetic model: t / q = 1 / (K2Q2) + t / Q

[0109] Where Q is the saturated adsorption amount; K1 is the pseudo-first-order rate constant; q is the adsorption amount at time t; K2 is the pseudo-second-order rate constant.

[0110] The adsorption amount (mg / g) is taken as the ordinate and the adsorption time (min) is taken as the abscissa to draw the adsorption kinetics curve. The adsorption amount at each moment is brought into the two kinetic equations for fitting to obtain the adsorption kinetics curve. Fig.16 and 17 ;

[0111] Depend on Fig.16 , Fig.17 It can be seen that R1 2 is 0.9588, R2 2 The calculated equilibrium adsorption capacity is 2.779 mg / g, while the actual equilibrium adsorption capacity is 2.772 mg / g. It can be judged that the adsorption law of phosphate by modified pomelo peel conforms to the second-order kinetic model. The mechanism is established according to the quasi-second-order kinetic equation, which shows that the adsorption process of phosphorus-containing wastewater by pomelo peel is mainly chemical adsorption and physical and chemical adsorption coexist.

[0112] Table 5

[0113]

[0114]

[0115] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0116] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method, characterized in that: The following steps are involved: (1) Pretreatment Put the dried pomelo peel into boiling water and steam for a while, set aside; (2) Enzymatic hydrolysis The steamed grapefruit peel is placed in a hemicellulase solution for a period of time, and then the grapefruit peel is rinsed to neutrality; (3) Enzyme inactivation and decolorization The washed pomelo peel is placed in an ultrasonic instrument for enzyme inactivation treatment, filtered after treatment, and then anhydrous ethanol is added for decolorization treatment, filtered and washed after treatment to obtain a semi-finished product; (4) Drying The semi-finished product is dried to constant weight and crushed to obtain a phosphorus removal adsorbent.

2. The method for preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method according to claim 1, characterized in that: The cooking time is 25-35 minutes.

3. The method for preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method according to claim 1, characterized in that: The mass concentration of the hemicellulase solution is 0.4%.

4. The method for preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method according to claim 1, characterized in that: The enzymatic hydrolysis time was 12 h.

5. The method for preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method according to claim 1, characterized in that: The parameters of the enzyme inactivation treatment include: pH=2.5 buffer solution, enzyme inactivation treatment at 80°C and 200W for 30 minutes.

6. The method for preparing a phosphorus removal adsorbent using ultrasound-assisted hemicellulase method according to claim 1, characterized in that: The decolorization time is 18h.

7. Use of a dephosphorus adsorbent prepared by the method for preparing a dephosphorus adsorbent by ultrasound-assisted hemicellulase method as described in any one of claims 1 to 6 in treating phosphorus-containing wastewater.

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