Method for treating fuling preserved vegetable wastewater by alkali etching diatomite mineral

Abstract

The application provides a method for treating Fuling preserved vegetable wastewater by adding alkali-treated diatomite minerals into the Fuling preserved vegetable wastewater; or a method for treating Fuling preserved vegetable wastewater by adding untreated diatomite minerals into the Fuling preserved vegetable wastewater, carrying out solid-liquid separation after a period of reaction, filtering out the solid part, and then adding alkali-treated diatomite minerals into the liquid part. The method can effectively adjust the pH value of the Fuling preserved vegetable wastewater, reduce the content of ammonia nitrogen in the Fuling preserved vegetable wastewater, and improve the purity of the diatomite minerals. The method for treating Fuling preserved vegetable wastewater has the advantages of simplicity, feasibility, low operation cost, and no potential environmental threat, and is a green and environmentally-friendly treatment method, which can effectively improve the treatment effect of the Fuling preserved vegetable wastewater.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment, specifically to a method for treating Fuling pickled mustard tuber wastewater by alkaline etching of diatomaceous earth minerals. Background Technology

[0002] Fuling pickled mustard tuber wastewater is acidic, with a pH value typically around 4, and contains a large amount of ammonium nitrogen. In practical utilization and treatment, it needs to be adjusted to a weakly alkaline environment of 7-8.5 and its ammonium nitrogen concentration reduced to facilitate subsequent aerobic treatment and avoid ammonia release and environmental stress. In the past, sodium bicarbonate and sodium hydroxide were commonly used to adjust the pH value during aerobic treatment. However, on the one hand, these chemicals are relatively expensive, leading to high treatment costs for pickled mustard tuber wastewater and hindering its widespread adoption; on the other hand, alkaline reagents such as sodium hydroxide pose potential environmental hazards and could cause secondary pollution; furthermore, these alkaline reagents are corrosive, posing significant safety risks during transportation and use. Therefore, using alkaline reagents to treat the aforementioned wastewater is difficult to apply on a large scale.

[0003] Studies have found that directly adding mined diatomaceous earth to pickled mustard tuber wastewater can neutralize organic acids in the wastewater. However, it should be noted that its neutralization capacity is limited. Although adding more than 200 kg of diatomaceous earth to 1 ton of pickled mustard tuber wastewater significantly increases its pH to 6.5, the pH remains essentially unchanged with subsequent additions of diatomaceous earth. Furthermore, diatomaceous earth minerals often contain carbonates or hydroxides of metallic elements such as calcium and magnesium during the mining process. These impurities reduce the purity and quality of the diatomaceous earth.

[0004] There is an urgent need to find a wastewater treatment method for Fuling pickled mustard tuber that is environmentally friendly, economical, efficient, and can also purify diatomite minerals.

[0005] To address the above problems, this invention is proposed. Summary of the Invention

[0006] This invention provides a method for treating Fuling pickled mustard tuber wastewater with diatomaceous earth minerals, which involves adding alkali-treated diatomaceous earth minerals to the Fuling pickled mustard tuber wastewater.

[0007] Preferably, untreated diatomaceous earth minerals can be added to the wastewater of Fuling pickled mustard tuber first, and after reacting for a period of time, solid-liquid separation is carried out, the solid part is filtered out, and then the alkali-treated diatomaceous earth minerals are added to the liquid part.

[0008] Preferably, the specific steps of the method for preparing the alkali-treated diatomaceous earth mineral include placing diatomaceous earth in an alkaline solution to form a suspension, heating and holding the suspension at a certain temperature, cooling it, and then performing solid-liquid separation. The solid part is the alkali-treated diatomaceous earth mineral. Heating the suspension and holding it for a period of time helps to accelerate the reaction process between the diatomaceous earth and the alkaline solution, allowing the silica in the diatomaceous earth to react quickly and fully with the alkaline solution. Etching the surface of the diatomaceous earth also helps to form more Si-O bonds.

[0009] Preferably, the alkaline solution includes, but is not limited to, one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, and potassium carbonate.

[0010] Preferably, the concentration of the alkaline solution is 0.05–0.5 mol / L.

[0011] Preferably, the amount of alkaline solution added is calculated as the ratio of the mass of diatomaceous earth to the volume of alkaline solution: 1g / 40mL to 1g / 20mL.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The diatomaceous earth mineral prepared by the method of this invention can not only adjust the wastewater from Fuling pickled mustard tuber production to a weakly alkaline environment and effectively remove ammonia nitrogen, but also purify the diatomaceous earth using the wastewater. Furthermore, the treated diatomaceous earth contains a large amount of ammonia nitrogen, which can be used as an ammonia nitrogen-based organic fertilizer. The method for treating Fuling pickled mustard tuber wastewater in this invention not only has advantages such as simplicity, feasibility, and low operating costs, but also does not pose a potential environmental threat. Therefore, it is a green and environmentally friendly treatment method that can effectively improve the treatment effect of Fuling pickled mustard tuber wastewater. At the same time, this method is easy to implement and has broad application prospects.

[0014] 2. Due to its high acidity and high organic matter content, the wastewater from pickled mustard tubers contains a large number of positively charged organic colloids in its suspension (due to H...). + The diatomaceous earth is mostly adsorbed onto these micelles. These micelles have the same charge and repel each other, so they do not aggregate and form a stable suspension. After alkaline treatment, the surface of the diatomaceous earth carries more negative charge (due to silanol groups). The negative charge can neutralize the positive charge of the micelles, making the micelles uncharged and easier to aggregate and settle. This is beneficial to improving the clarity of wastewater and reducing the COD of wastewater. This effect is unmatched by conventional minerals such as calcium carbonate / non-alkali treated diatomaceous earth.

[0015] 3. The acid in the wastewater from pickled mustard tuber is divided into free acid (H+ directly contributes to low pH) and suspended organic acid flocs (H+ is released after the free acid is consumed due to the equilibrium principle, which makes a backup contribution to low pH). Therefore, a portion of conventional diatomaceous earth can be added first to adsorb and precipitate those organic acid flocs, and then solid-liquid separation can be performed to remove the backup acid. Then, diatomaceous earth treated with alkali can be added to the liquid, so that less alkali can be used to treat the diatomaceous earth to efficiently increase the pH value. Attached Figure Description

[0016] Figure 1 These are scanning electron microscope images of diatomaceous earth minerals treated with alkali as described in Example 1;

[0017] Figure 2 These are scanning electron microscope images of diatomaceous earth minerals treated with alkali as described in Example 2;

[0018] Figure 3 These are electron microscope scan images of diatomaceous earth minerals treated with alkali as described in Example 3;

[0019] Figure 4 These are scanning electron microscope images of diatomaceous earth minerals treated with alkali as described in Example 4;

[0020] Figure 5 This is a scanning electron microscope image of diatomaceous earth minerals treated with alkali in Example 5. Detailed Implementation

[0021] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specified in the embodiments generally use conventional conditions and conditions described in the manual, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified.

[0022] Example 1

[0023] 100 kg of diatomaceous earth (Sichuan Miyi diatomaceous earth mineral, with an alkali metal carbonate or hydroxide content of approximately 7%) was placed in 1000 L of 0.05 mol / L sodium hydroxide solution to form a suspension. After thorough stirring, the solution was heated to boiling under normal pressure and maintained for 12 hours. After cooling, solid-liquid separation was performed to obtain the alkali-treated diatomaceous earth. The obtained alkali-treated diatomaceous earth was observed under a scanning electron microscope as follows: Figure 1 As shown in the figure and evaluated by a particle size analyzer, the single particle size distribution is 7–25 μm.

[0024] Through actual treatment of pickled mustard tuber wastewater with diatomaceous earth minerals, it was found that within just one day, 20 kg of alkali-treated diatomaceous earth could raise the pH of 100 kg of pickled mustard tuber wastewater from 4 to 7.5, reduce the ammonium nitrogen content by 30%, and increase the purity of the diatomaceous earth by 15%. (While diatomaceous earth minerals that have not undergone alkali treatment can only adjust the pH to 6.5 and reduce the ammonium nitrogen content by 15%).

[0025] Example 2

[0026] 100 kg of diatomaceous earth (Sichuan Miyi diatomaceous earth mineral, with an alkali metal carbonate or hydroxide content of approximately 7%) was placed in 500 L of 0.5 mol / L sodium hydroxide solution to form a suspension. After thorough stirring, the solution was heated to boiling under normal pressure and maintained for 24 hours. After cooling, solid-liquid separation was performed to obtain the alkali-treated diatomaceous earth. The obtained alkali-treated diatomaceous earth was observed under a scanning electron microscope as follows: Figure 2 According to particle size analyzer evaluation, the single particle size distribution is 5-20 μm.

[0027] Through actual treatment of pickled mustard tuber wastewater with diatomaceous earth minerals, it was found that within just one day, 20 kg of alkali-treated diatomaceous earth could raise the pH of 100 kg of pickled mustard tuber wastewater from 4 to 8, reduce the ammonium nitrogen content by 25%, and increase the purity of diatomaceous earth by 13%.

[0028] Example 3

[0029] 100 kg of diatomaceous earth (Sichuan Miyi diatomaceous earth mineral, with an alkali metal carbonate or hydroxide content of approximately 7%) was placed in 1000 L of 0.1 mol / L ammonia solution to form a suspension. After thorough stirring, the suspension was placed in a hydrothermal apparatus and heated to 100°C, maintained for 12 hours. After cooling, solid-liquid separation was performed to obtain alkali-treated diatomaceous earth. The obtained alkali-treated diatomaceous earth was observed under a scanning electron microscope as follows: Figure 3 According to particle size analyzer evaluation, the single particle size distribution is 10-30 μm.

[0030] Through actual treatment of pickled mustard tuber wastewater with diatomaceous earth minerals, it was found that within just one day, 20 kg of alkali-treated diatomaceous earth could raise the pH of 100 kg of pickled mustard tuber wastewater from 4 to 7, reduce the ammonium nitrogen content by 20%, and increase the purity of diatomaceous earth by 10%.

[0031] Example 4

[0032] 100 kg of diatomaceous earth (Sichuan Miyi diatomaceous earth mineral, with an alkali metal carbonate or hydroxide content of approximately 7%) was placed in 500 L of 1 mol / L sodium carbonate solution to form a suspension. After thorough stirring, the suspension was placed in a hydrothermal apparatus and heated to 200°C, maintained for 6 hours. After cooling, solid-liquid separation was performed to obtain alkali-treated diatomaceous earth. The obtained alkali-treated diatomaceous earth was observed under a scanning electron microscope as follows: Figure 4 According to particle size analyzer evaluation, the single particle size distribution is 7-25 μm.

[0033] Through actual treatment of pickled mustard tuber wastewater with diatomaceous earth minerals, it was found that within just one day, 20 kg of alkali-treated diatomaceous earth could raise the pH of 100 kg of pickled mustard tuber wastewater from 4 to 7, reduce the ammonium nitrogen content by 20%, and increase the purity of diatomaceous earth by 10%.

[0034] Example 5

[0035] 100 kg of diatomaceous earth (Sichuan Miyi diatomaceous earth mineral, with an alkali metal carbonate or hydroxide content of approximately 7%) was placed in 1500 L of a 0.5 mol / L mixed solution of sodium hydroxide and potassium hydroxide to form a suspension. After thorough stirring, the suspension was placed in a hydrothermal apparatus and heated to 150 °C, maintained for 10 hours. After cooling, solid-liquid separation was performed to obtain alkali-treated diatomaceous earth. The obtained alkali-treated diatomaceous earth was observed under a scanning electron microscope as follows: Figure 5 According to particle size analyzer evaluation, the single particle size distribution is 5-20 μm.

[0036] Through actual treatment of pickled mustard tuber wastewater with diatomaceous earth minerals, it was found that within just one day, 20 kg of alkali-treated diatomaceous earth could raise the pH of 100 kg of pickled mustard tuber wastewater from 4 to 8.5, reduce the ammonium nitrogen content by 25%, and increase the purity of diatomaceous earth by 15%.

[0037] Example 6

[0038] First, 10 kg of untreated diatomaceous earth was added to 100 kg of pickled mustard tuber wastewater for solid-liquid separation. Then, 10 kg of alkali-treated diatomaceous earth (as described in Example 1) was added to the filtrate. Experimental results showed that the pH of the 100 kg pickled mustard tuber wastewater increased from 4 to 7.5, the ammonium nitrogen content decreased by 27%, and the purity of the diatomaceous earth increased by 13%. (This saves half the amount of alkali-treated diatomaceous earth while achieving a similar treatment effect to diatomaceous earth treated only with alkali.)

[0039] Example 7

[0040] First, 10 kg of untreated diatomaceous earth was added to 100 kg of pickled mustard tuber wastewater for solid-liquid separation. Then, 10 kg of alkali-treated diatomaceous earth from Example 2 was added to the filtrate. Experimental results showed that the pH of 100 kg of pickled mustard tuber wastewater increased from 4 to 8, the ammonium nitrogen content decreased by 23%, and the purity of diatomaceous earth increased by 10%. (This can save half of the alkali-treated diatomaceous earth while achieving a similar treatment effect as diatomaceous earth treated with only alkali).

Claims

1. A method for treating Fuling preserved vegetable wastewater by diatomite mineral, characterized in that, The untreated diatomite mineral is added into the Fuling preserved vegetable wastewater, so that the untreated diatomite absorbs the suspended organic acid colloid in the wastewater, and after a period of reaction, solid-liquid separation is performed, the solid part is filtered out, and pretreated wastewater is obtained; then the diatomite mineral with negative charges on the surface after alkali treatment is added into the pretreated wastewater.

2. The method of claim 1, wherein, The preparation method of the diatomite mineral after alkali treatment specifically comprises the following steps: placing diatomite in an alkaline solution to form a suspension, heating and keeping the suspension, cooling, and performing solid-liquid separation, and the solid part is the diatomite mineral after alkali treatment.

3. The method of claim 2, wherein, The alkaline solution comprises but is not limited to one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate and potassium carbonate.

4. The method of claim 2, wherein, The concentration of the alkaline solution is 0.05-0.5 mol / L.

5. The method of claim 2, wherein, The addition amount of the alkaline solution is 1 g / 40 mL-1 g / 20 mL in terms of the mass of diatomite to the volume of the alkaline solution.

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