TWI605856B - Method of removing heavy metals from soil - Google Patents

Description

Method for removing heavy metals from soil

The present invention relates to the technical field of soil rejuvenation, and in particular to a method for removing heavy metals from soil.

Although the rapid development of industry has driven the overall economic prosperity, it has led to environmental pollution, such as air pollution, water pollution and land pollution. Heavy metals can cause land pollution, and because the pollution source is relatively difficult to remove, the damage caused by entering the human body is extremely great, so the land pollution caused by heavy metals is particularly concerned.

At present, the commonly used methods for treating heavy metals in soil are: inverted dilution method, chemical removal method, and phytoremediation method. The "flip-dilution method" mainly involves the mixing of contaminated soil, but in fact the soil still has heavy metals that are not really removed from the soil. "Chemical removal method" mainly uses dilute acid solution or chelating agent to interact with contaminated soil; after chemical removal, heavy metals can be removed from contaminated soil, but soil texture and fertility deteriorate after action, thus affecting soil Subsequent applications. The "vegetation and rejuvenation method" mainly involves planting plants in contaminated soil and absorbing heavy metals through plants; however, heavy metals and soil particles are attracted by positive and negative charges, respectively, so heavy metals are not easily moved, making it costly. The remediation time is long. On the other hand, after the plant absorbs heavy metals, heavy metals are concentrated in the roots of the plants, so the whole plant must be removed to remove heavy metals from the soil. If the soil is contaminated to a serious extent and the phytoremediation method is to be carried out several times, the plants must be replanted each time and the plants should be long-leaved, flowered, or the result. In this way, the overall remediation time of the overall cost is extended.

For the sake of the job, it is indeed necessary to propose a new method of phytoremediation to solve the problem of the current phytoremediation method.

The object of the present invention is to improve the problems of the current planting and recultivating method for treating heavy metals in soil, such as poor mobility of heavy metals, resulting in excessive remediation time per planting and replanting method, and/or whole plant transfer. In addition to the long-term remediation of the total cost of the phytoremediation method.

Accordingly, in order to achieve the above and/or other objects, the present invention provides a method for removing heavy metals from soil, which comprises: planting a plant in a soil contaminated with heavy metals; adding a fermentation broth to the soil, wherein the fermentation broth is a culture yeast Bacteria, lactic acid bacteria, photosynthetic bacteria, and Pseudomonas to a molasses broth until the pH of the molasses broth reaches 4 or less; culture the plants to their long leaves, flowering or results; and remove the plant shoots .

According to the present invention, the fermentation broth used can promote plant growth to increase the tolerance of the plant to the toxicity caused by heavy metals. Moreover, the fermentation broth can also enhance the ability of plants to absorb heavy metals and assist in the transfer of heavy metals from the lower part of the plant to the shoot. In this way, the effect of removing heavy metals from the soil can be achieved by directly removing the shoots after plant cultivation, and the whole plant does not have to be removed. If the soil is too polluted, the fermentation can be added directly to the next removal, and it is not necessary to replant the plants.

In order to make the above and/or other objects, functions and features of the present invention more comprehensible, the preferred embodiments are described in detail below.

One embodiment of the present invention provides a method of removing heavy metals from soil by transferring plants to a particular fermentation broth to transfer heavy metals from the soil to the plant shoots. Afterwards, the removal of heavy metals from the soil can be achieved by directly removing the plant shoots. The detailed steps for the method proposed in this implementation are as follows:

First, plant plants in soils contaminated with heavy metals. In general, the life cycle of herbaceous plants is shorter than that of woody plants, and the aboveground parts of herbaceous plants are easier to remove from the shoots of woody plants, so the plants used are preferably herbaceous plants. Examples of plants may be, but are not limited to, rice, corn, Indian mustard, beetroot, sunflower, sphagnum, reed, medusa, american yam, yam, succulent, succulent, small fruit, lower Fern, phoenix, phoenix, fern, fern, or fern; and examples of heavy metals may be, but are not limited to, cadmium, zinc, mercury, copper, lead, arsenic, nickel, chromium , bismuth, selenium, or bismuth. In addition, in order to promote plant growth, a fertilizer may be added to the soil before or after planting, and examples of the fertilizer may be, but not limited to, Bokashi fertilizer.

Next, a fermentation broth is added to the soil, wherein the fermentation broth is obtained by cultivating yeast, lactic acid bacteria, photosynthetic bacteria, and Pseudomonas to a molasses broth until the pH of the molasses broth reaches 4 or less. In addition, the volume of the fermentation broth is enlarged to allow the fermentation broth to be uniformly mixed with the soil, and the fermentation broth may be mixed with a suitable liquid, such as water, physiological saline, liquid fertilizer, or other culture liquid suitable for the growth of the mixed bacteria. Further, in the present embodiment, the fermentation liquid addition step is carried out on the 15th to 45th day after the plant planting step. Moreover, in order to promote the ability of the plant to absorb heavy metals, the present embodiment may further add a chelating agent to the soil during the fermentation liquid addition step, and examples of the chelating agent may be, but not limited to, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetate). ), NTA (nitrilotriacetic acid), or EDDS (ethylenediamine-N, N'-disuccinic acid).

Next, the plants are grown to their long leaves, flowering or results. Further, in the present embodiment, the same fermentation broth may be added to the soil every 4 to 14 days during the culture to maintain the concentration of the fermentation broth in the soil. Similarly, to maintain the concentration of the chelating agent in the soil, the same chelating agent can be added to the soil every 4 to 14 days of culture.

Finally, remove the top of the plant. The term "overground" is relative to the lower part of the plant and mainly refers to organs that are not buried in the soil, such as stems, leaves, flowers, fruits, or any composition thereof. It should be noted that the plant topping removal step can be performed by directly removing the plant shoots and retaining the shoots in the soil, or directly removing the whole plants from the soil.

The invention is illustrated by the following examples:

<Preparation of cadmium metal contaminated soil>

Deionized water was first added to a soil and mixed for about 1 week to maintain a field capacity of about 50%. After adding the cadmium nitrate solution to the soil, the soil pH was adjusted with lime and mixed for 2 weeks to maintain the soil volume of the soil about 50%. Then, the soil was subjected to three wet and dry alternates to obtain soil contaminated with cadmium metal. If necessary, add 200g of Bosika fertilizer to the soil in advance.

<Addition of fermentation broth of rice planting and beneficial mixed bacteria>

After the rice is planted in the soil contaminated with cadmium metal for one month, the fermentation broth of the beneficial mixed bacteria having a pH of 4 or less is mixed with water at a ratio of 1:50 to 1:200 to obtain a diluted fermentation broth, and then the fermentation is diluted. The liquid is added to the soil; and the fermented liquid of the beneficial mixed bacteria is prepared by cultivating yeast, lactic acid bacteria, photosynthetic bacteria, and pseudomonas (hereinafter, the four kinds of bacteria are collectively referred to as "beneficial mixed bacteria") to a molasses culture. In the liquid, until the pH of the molasses medium reaches 4 or less. Next, it is cultured according to the physiological characteristics of rice, and the same diluted fermentation broth is added to the soil every 1 week until the rice is chopped. If necessary, when adding the diluted fermentation broth, an EDTA solution containing 2 mmol/kg of soil may be added to the soil; and the same amount of EDTA solution may be added to the soil every 1 week during the culture for 3 weeks.

<Appearance of rice>

After the earing, the whole rice was uprooted and the height and weight of the rice were measured. As shown in Table 1, cadmium metal does affect rice growth; however, under the same cadmium metal contamination, soil with diluted fermentation broth is more conducive to rice growth than soil without added soil. Table 1. Growth status of rice after cultivation with soil containing different additives         <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> Soil initial cadmium concentration (mg/kg) </td><td> Additives< /td><td> Rice height (cm) </td><td> Rice weight (kg) </td></tr><tr><td> 0 </td><td> None </td> Td><td> 71.0±2.9 </td><td> 104.15±4.18 </td></tr><tr><td> 20 </td><td> no </td><td> 63.7± 2.6 </td><td> 73.27±3.65 </td></tr><tr><td> Diluted fermentation broth</td><td> 64.5±3.7 </td><td> 79.97±2.77 </ Td></tr><tr><td> dilute fermentation broth+chelating agent</td><td> 67.5±4.0 </td><td> 80.52±3.00 </td></tr><tr>< Td> diluted fermentation broth + bokasi</td><td> 71.0±2.0 </td><td> 94.67±2.95 </td></tr><tr><td> diluted fermentation broth + chelating agent + Boccasi</td><td> 71.0±3.6 </td><td> 91.22±2.32 </td></tr></TBODY></TABLE>

<Analysis of cadmium metal content>

After the earing, take 1 g of each organ of rice. After adding 10 mL of nitric acid to each organ, it was allowed to stand for 1 hour. Next, the obtained nitric acid solution was sequentially subjected to microwave treatment, filtration, and analysis to obtain cadmium metal contents of various organs of rice.

After the earing, another 1 g of soil was taken. After adding 9 mL of nitric acid and 3 mL of hydrofluoric acid to the soil, it was allowed to stand for 1 hour. Thereafter, the obtained acid solution is subjected to microwave treatment; after adding 15 mL of a 4% boric acid solution to the acid solution, the acid solution is subjected to microwave treatment, filtration, and analysis to obtain a cadmium metal content of the soil.

As shown in Fig. 1, compared with rice grown in soil without added soil, rice grown in soil supplemented with only the fermented broth can absorb a large amount of heavy metals, and most of them exist in the upper part of the soil, especially the heavy metal concentration of the stem is greater than the root. Heavy metal concentration. In addition, the addition of soil that dilutes the fermentation broth and the chelating agent promotes a slight increase in the amount of heavy metals absorbed by the rice compared to the soil without added soil. Although the addition of the diluted fermentation broth and the soil of the bokasi fertilizer and the addition of the diluted fermentation broth, the chelating agent, and the soil of the bokasi fertilizer to promote the absorption of heavy metals by the rice are less than that of the unadded soil, the latter two are Plant growth is more beneficial than the former (Table 1).

Here, introduce the following terms: BCF, the full name of bioconcentration factor, Chinese called "bioconcentration factor", refers to the concentration of heavy metals in the roots of plants divided by the concentration of heavy metals in the soil; TF, the full name is translocation factor, Chinese "plant transfer factor" refers to the value of the heavy metal concentration in the plant shoots divided by the heavy metal concentration in the plant roots; BAF, the full name of bioaccumulation factor, is called "bioaccumulation factor" in Chinese, and refers to the concentration of heavy metals in the plant shoots. The value obtained by the heavy metal concentration of the soil, that is, the value obtained by multiplying BCF by TF.

It can be seen from the above definition that BCF represents the ability of heavy metals to transfer from the soil to the roots, TF represents the ability of heavy metals to transfer from the roots to the shoots, and BAF represents the ability of heavy metals to transfer from the soil to the shoots. It can be seen from Table 2 that the TF and BAF of the soil to which the diluted fermentation broth is added are superior to the soil without added, whether or not mixed with other substances. This means that diluting the fermentation broth can promote the transfer of heavy metals from the soil to the shoots. Table 2. Distribution of cadmium metal after cultivating rice with soil containing different additives         <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> Soil initial cadmium concentration (mg/kg) </td><td> Additives< /td><td> BCF </td><td> TF </td><td> BAF </td></tr><tr><td> 20 </td><td> None</td> <td> 1.168 </td><td> 0.425 </td><td> 0.496 </td></tr><tr><td> Diluted Fermentation Solution</td><td> 2.688 </td>< Td> 1.317 </td><td> 4.013 </td></tr><tr><td> Dilution Fermentation Liquid + Chelating Agent</td><td> 1.466 </td><td> 1.213 </td ><td> 1.778 </td></tr><tr><td> Diluted Fermentation Broth + Boccasi</td><td> 0.511 </td><td> 1.340 </td><td> 0.685 </td></tr><tr><td> Diluted Fermentation Broth + Chelating Agent + Boccasi</td><td> 1.151 </td><td> 1.066 </td><td> 1.227 </ Td></tr></TBODY></TABLE>

In summary, the fermentation broth of the present embodiment can promote plant growth to increase the tolerance of the plant to the toxicity caused by heavy metals. Moreover, the fermentation broth can also enhance the ability of plants to absorb heavy metals and assist in the transfer of heavy metals from the lower part of the plant to the shoot. In this way, the effect of removing heavy metals from the soil can be achieved by directly removing the shoots after plant cultivation, and the whole plant does not have to be removed. If the soil is too polluted, the fermentation can be added directly to the next removal, and it is not necessary to replant the plants.

The above is only the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made by the scope of the present invention and the contents of the description of the invention, All remain within the scope of the invention patent.

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Figure 1 is a long bar graph showing the amount of cadmium metal uptake by various organs of rice after different treatments.

Claims (10)

A method for removing heavy metals from soil comprises: planting a plant in a soil contaminated with heavy metals; adding a fermentation broth and a chelating agent to the soil, wherein the fermentation broth is a culture yeast, a lactic acid bacteria, a photosynthetic bacteria, and Pseudomonas to a molasses broth until the pH of the molasses broth reaches a value of 4; the plant is cultured to its long leaves, flowering or results; and the plant shoots are removed. The method of claim 1, wherein the plant is a herb. The method of claim 1, wherein the plant is selected from the group consisting of rice, corn, Indian mustard, beetroot, sunflower, sphagnum, reed, medusa, yarrow, yam, and citrus A group consisting of a small fruit leaf, a phoenix, a phoenix, a phoenix, a fern, a fern, a fern, a fern, and a long-leaved kidney fern. The method of claim 1, wherein the heavy metal is selected from the group consisting of cadmium, zinc, mercury, copper, lead, arsenic, nickel, chromium, antimony, selenium, and tellurium. The method of claim 1, wherein before the planting step, the method further comprises: adding a fertilizer to the soil. The method of claim 1, wherein the planting step further comprises: adding a fertilizer to the soil. The method of claim 5, wherein the fertilizer is Bokashi fertilizer. The method of claim 1, wherein the plant is above the stem, leaf, flower, or fruit. The method of claim 1, wherein the fermentation broth addition step is performed on days 15 to 45 after the plant planting step. The method of claim 1, wherein the plant culturing step comprises: adding the same fermentation broth to the soil.