Preparation method of tillering onion waste bio-adsorbent

Abstract

The invention is applicable to the technical field of bio-adsorbents, and particularly relates to a preparation method of a tillering onion waste bio-adsorbent, which comprises the following steps: obtaining tillering onion waste, removing impurities in the tillering onion waste, cleaning and drying the tillering onion waste, crushing and grinding, and sieving to obtain the tillering onion waste bio-adsorbent. The adsorbent is obtained. According to the preparation method of the tillering onion waste bio-adsorbent, the tillering onion waste is used for preparing the bio-adsorbent, when the bio-adsorbent is applied to environmental restoration, complicated steps such as modification are reduced, the adsorption efficiency is improved, under the condition that the adding amount is 5.0 g / L, the removal rate of cadmium ions in a cadmium ion solution with the concentration being 100 mg / L reaches up to 92.48%, and the removal rate of the cadmium ions in the cadmium ion solution with the concentration being 100 mg / L reaches up to 92.48%. The long-term stability and effectiveness are realized in the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of biosorbents, and in particular relates to a method for preparing a tillering onion waste biosorbent. Background Art

[0002] Tillering onion (Allium cepa var.aggregatum), Allium family, has a compact fruit nutritional structure and extremely high medical value. It is produced in Northeast China and is planted in April and harvested in June. After harvesting, its inedible parts such as skin, roots, and leaves are often dumped on the sides of the road, directly causing adverse effects on the local soil and air environment. The waste ferments under the influence of the hot summer climate and continuously releases greenhouse gases into the surrounding environment.

[0003] Considering that the epidermis of tillering onions is rich in bioactive ingredients such as cellulose and lignin, it can provide more active adsorption sites, which can be used to adsorb potentially toxic element ions, thereby achieving "waste treatment with waste" and realizing a win-win situation of water pollution remediation and greenhouse gas emission reduction.

[0004] At present, the treatment methods for heavy metal pollution in water bodies include chemical precipitation, ion exchange, membrane separation, electrochemical method, etc. Among them, traditional methods such as chemical precipitation and membrane separation are complex in operation and high in cost. The electrochemical method is greatly limited in practical application. The main problem of these traditional methods is the high energy consumption of the equipment. How to achieve energy conservation, emission reduction and consumption reduction while controlling pollution has become the biggest challenge facing traditional methods.

[0005] In this context, adsorption method stands out due to its low cost, simple operation and high efficiency. The main adsorption materials include activated carbon, clay minerals, nanomaterials and industrial and agricultural solid wastes, among which agricultural wastes such as straw, wheat straw and fruit shells have been widely studied. However, when agricultural wastes such as straw are directly used for environmental remediation, they are often inefficient and have disadvantages such as poor mechanical strength and low density. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a tillering onion waste biosorbent, aiming to solve the problem of low efficiency when agricultural waste is directly used for environmental remediation.

[0007] The present invention is achieved by providing a method for preparing a tillering onion waste biosorbent, the method comprising: obtaining tillering onion waste, removing impurities in the tillering onion waste, washing and drying the tillering onion waste, crushing and grinding the tillering onion waste, and then sieving to obtain an adsorbent.

[0008] Preferably, the tillering onion waste contains at least the outer skin of the bulb, roots and leaves, and the proportion of the outer skin of the bulb is not less than 85%.

[0009] Preferably, impurities including leaves and foam are removed from the tillering onion waste.

[0010] Preferably, when cleaning the tillering onion waste, distilled water is used for cleaning.

[0011] Preferably, when the tillering onion waste is cleaned, dust and soil in the tillering onion waste are removed.

[0012] Preferably, in the step of drying the tillering onion waste, the drying is carried out at a temperature of 80°C.

[0013] Preferably, in the step of drying the tillering onion waste, the drying time is 20 hours.

[0014] The invention provides a method for preparing a tillering onion waste biosorbent, which proposes the use of tillering onion waste to prepare the biosorbent, reduces complicated steps such as modification when applied to environmental remediation, improves the adsorption efficiency, and has a removal rate of cadmium ions in a 100 mg / L cadmium ion solution of up to 92.48% under the condition of an addition amount of 5.0 g / L, and has long-term stability and effectiveness in the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of a method for preparing a tillering onion waste biosorbent provided by an embodiment of the present invention;

[0016] Figure 2 An electron microscope image of the surface morphology of the adsorbent provided in an embodiment of the present invention when it passes through a 140-mesh sieve;

[0017] Figure 3 An electron microscope image of the surface morphology of the adsorbent provided by an embodiment of the present invention when passing through a 20-mesh sieve;

[0018] Figure 4 The infrared spectrum of the adsorbent provided by the embodiment of the present invention;

[0019] Figure 5 The pH of the adsorbent provided by the embodiment of the present invention is PZC Schematic diagram of

[0020] Figure 6 A schematic diagram of the influence of different environmental factors on the adsorption effect provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] like Figure 1 As shown, a method for preparing a tillering onion waste biosorbent comprises: obtaining tillering onion waste, removing impurities in the tillering onion waste, washing and drying the tillering onion waste, crushing and grinding the tillering onion waste, and then sieving to obtain an adsorbent.

[0023] In this embodiment, tillering onion waste was collected in Nong'an County, Jilin Province, where tillering onion crops have been planted for many years. Tillering onion waste includes the outer skin of the bulb, roots and leaves, etc., with the outer skin of the bulb being the main component (accounting for more than 85%). After the tillering onion waste is collected, the mixed impurities such as leaves and foam are removed, and the waste is washed with distilled water to remove the dust, soil and other impurities on the surface. It is then dried at 80°C for 20 hours, crushed and ground, and sieved to obtain an adsorbent (AW). The preparation process of the adsorbent is shown in Figure 1 .

[0024] like Figure 2 and Figure 3 As shown in the figure, the surface morphology was observed by scanning electron microscopy to obtain the surface characteristics of the adsorbent. The surface of the adsorbent is rough, with developed wrinkles, depressions and corrugated structures ( Figure 2 ), retaining the complete biological cell structure ( Figure 3 ).

[0025] like Figure 4 As shown, the functional groups on the adsorbent surface were analyzed:

[0026] Take 1 mg of adsorbent powder sample and place it in an agate mortar, add 100 mg of dried potassium bromide, grind it and press it into a transparent sheet (pressure 8-10 MPa), and use Fourier transform infrared spectrometer to collect and test to obtain the surface functional groups of the adsorbent. The results show ( Figure 4 ), at 3400cm -1 The stretching vibration peak of C-OH appears at 2920 cm -1 The CH stretching vibration peak appears at 1640cm -1 Strong conjugated C=O group or C=C appears nearby; 1432cm -1 Nearby, there is a C-H2 shear vibration peak from cellulose or a C-H2 bending vibration peak from lignin; 1369cm -1 There is a CH bending vibration peak near 1324 cm -1 The CH deformation vibration peak appears at 1160cm-1 The COC stretching vibration of ether or CO stretching vibration of alcohol appears nearby at 1054 cm -1 The infrared spectrum shows that the tillering onion waste adsorbent is mainly composed of cellulose, hemicellulose and lignin, and contains rich structures such as phenol, alcohol, ketone and aromatic ring.

[0027] Analyze the physical and chemical properties of adsorbent:

[0028] The pH of the adsorbent was measured at a solid-liquid ratio of 1:20; the conductivity of the adsorbent was measured at a solid-liquid ratio of 1:100, and the ash content of the adsorbent was measured by calcination at 800°C for 4 hours; the C, H, N, and O contents of the adsorbent were obtained using an elemental analyzer, and the contents of constant elements such as K, Ca, Na, and Mg in the adsorbent were obtained using an X-ray fluorescence spectrometer. The test results of the physical and chemical properties of the adsorbent are shown in Table 1. AW has a lower O / C and (O+N) / C atomic ratio, lower ash content, less inorganic content, and poor hydrophilicity and polarity. The adsorbent surface contains cations such as K, Na, and Ca, which can adsorb cadmium by ion exchange with cadmium ions.

[0029] Table 1 Physical and chemical properties of adsorbents

[0030]

[0031] like Figure 5 As described above, the pH value of zero charge point of the adsorbent (pH PZC )

[0032] The pH of the adsorbent was obtained by titration with an inert electrolyte. PZC , the pH0 of 0.1 mol / L K2SO4 solution was adjusted between 2 and 12 using HCl and NaOH solutions of different concentrations, 0.1 g of adsorbent was added to 50 mL of the solution and then oscillated on a 160 rpm / min cyclotron for 24 h, the pH1 of the solution was measured, and the difference in pH before and after (ΔpH) was used as the ordinate and pH0 as the abscissa to plot, and the pH corresponding to the intersection of the curve and ΔpH=0 was the pH PZC The experimental results show that the pH of the adsorbent PZC =4.62( Figure 5 ).

[0033] 1. Removal of cadmium ions in water by adsorbent

[0034] Weigh 0.2371g of C4H6CdO4·2H2O solid and dissolve it in 1L of water to obtain a 100mg / L cadmium ion solution. Measure 50mL of the cadmium ion solution in a conical flask, add 0.25g of adsorbent, place it on a 170rpm / min cyclotron oscillator for 2h, remove it, centrifuge it, and use an atomic absorption spectrometer to determine the concentration of cadmium ions in the supernatant. The adsorption rate and equilibrium adsorption amount of the adsorbent for cadmium ions are calculated according to Formula 1 and Formula 2:

[0035] R=(C0-C t ) / C0×100% (Formula 1)

[0036] q e =(C0–C t )×V / m(Formula 2)

[0037] Where R is the adsorption rate, %; C0 is the initial concentration of cadmium ions, mg / L; C t is the cadmium ion concentration after adsorption, mg / L; q e is the adsorption amount, mg / g; V is the solution volume, V=50mL; m is the mass of the adsorbent, m=0.25g.

[0038] Under this condition, the adsorption rate of the adsorbent for cadmium ions is 92.48%, and the adsorption amount is 18.43 mg / g.

[0039] 2. Analysis of factors affecting adsorption rate of cadmium ions by adsorbent

[0040] The factors affecting the adsorption rate mainly include the initial concentration of cadmium ions, the ionic strength of the solution, pH, organic ligand concentration, the amount of adsorbent and the particle size of the adsorbent. The particle size of the adsorbent was set to 20, 40, 60, 80, 100, 120, 140, 160 and 180 mesh, the pH of the solution was set to 2.05, 3.04, 4.05, 4.9, 5.7, 6.06, 6.48, 7.0 and 8.0, the initial concentration of cadmium ions was set to 16.5, 52.7, 105.8, 234.7, 535.1, 966 and 2676 mg / L, and the adsorbent dosage was set to 0.2, 0.5, 2.0, 2.0, 5.0, 10.0, 20.0 and 40.0 mg / g, the ionic strength was set to 0, 0.001, 0.002, 0.004, 0.008, 0.01, 0.02, 0.04, 0.08 and 0.1 mol / L according to the concentration of sodium chloride, and the organic ligand was set to 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.4, 0.6, 0.8 and 1.0 mmol / L according to the concentration of EDTA. The results show that different environmental factors have a significant effect on the removal effect of cadmium ions by the adsorbent ( Figure 6). Overall, different particle sizes have little effect on the adsorption effect, but as the adsorbent particle size decreases, the adsorption efficiency decreases. Acidic conditions are not conducive to the adsorption process. As the acidity of the solution decreases, the adsorption efficiency gradually increases. When the adsorbent dosage is constant, the increase in cadmium ion concentration in the solution will lead to a decrease in the adsorption rate, but the adsorption capacity per unit adsorbent increases. The optimal dosage of the adsorbent is 5.0g / L. When the amount of adsorbent is <5.0g / L, the adsorption efficiency is not high. When the dosage exceeds 5.0g / L, the adsorption capacity per unit adsorbent decreases. While the cost increases, there is no significant increase in the removal rate of cadmium ions. The presence of chloride ions, sodium ions and organic ligands in the solution will seriously affect the adsorption effect. With the increase of solution ionic strength and organic ligands, the adsorption efficiency and adsorption amount will drop significantly. Figure 6 Among them, (a) the effect of adsorbent particle size on the adsorption effect; (b) the effect of solution pH on the adsorption effect; (c) the effect of initial cadmium ion concentration on the adsorption effect; (d) the effect of adsorbent dosage on the adsorption effect; (e) the effect of ionic strength on the adsorption effect; (f) the effect of organic ligand on the adsorption effect.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a biosorbent from tillering onion waste, characterized in that: The method comprises: obtaining tillering onion waste, removing impurities in the tillering onion waste, washing and drying the tillering onion waste, crushing and grinding the tillering onion waste, and then sieving to obtain an adsorbent.

2. The method for preparing the tillering onion waste biosorbent according to claim 1, characterized in that: The tillering onion waste contains at least the outer skin of the bulb, roots and leaves, and the proportion of the outer skin of the bulb is not less than 85%.

3. The method for preparing the tillering onion waste biosorbent according to claim 1, characterized in that: Remove impurities including leaves and foam from tiller onion waste.

4. The method for preparing the tillering onion waste biosorbent according to claim 2, characterized in that: When cleaning the tillering onion waste, use distilled water to clean it.

5. The method for preparing the tillering onion waste biosorbent according to claim 1, characterized in that: When washing the tiller onion waste, remove dust and soil from the tiller onion waste.

6. The method for preparing the tillering onion waste biosorbent according to claim 1, characterized in that: In the step of drying the tillering onion waste, the waste is dried at a temperature of 80°C.

7. The method for preparing the tillering onion waste biosorbent according to claim 3, characterized in that: In the step of drying the tillering onion waste, the drying time is 20 hours.

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