TW201825150A - Method for removing heavy metals from soils capable of effectively removing heavy metals from soils and shortening plant rehabilitation time - Google Patents

Abstract

The present invention provides a method for removing heavy metals from soils, which includes planting a plant in a soil contaminated with heavy metals; adding a fermentation broth into the soil, wherein the fermentation broth is obtained by culturing a yeast, a lactic acid bacteria, photosynthetic bacteria and Pseudomonas into a molasses culture solution until the molasses culture solution reaches a pH value of 4 or less; growing the plant to grow leaves, blossom or produce fruits; and removing the plant shoots.

Description

Method for removing heavy metals from soil

The invention relates to the technical field of soil rehabilitation, and particularly proposes a method for removing heavy metals from soil.

Although the rapid development of industry has promoted 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, and the damage caused by entering the human body is extremely great, land pollution caused by heavy metals is of particular concern.

At present, the commonly used methods for treating heavy metals in soil are: flip dilution method, chemical removal method, and vegetative rejuvenation method. The "flip-and-dilution method" is mainly to mix and contaminate the contaminated soil, but in fact there are still heavy metals in the soil that have not really been removed from the soil. "Chemical removal method" mainly uses dilute acid solution or chelating agent to interact with the contaminated soil. After chemical removal method, although heavy metals can be removed from the contaminated soil, the soil texture and fertility become worse after the effect, which affects the soil Follow-up application. The "Plant Rejuvenation Method" is mainly for planting plants in contaminated soil and absorbing heavy metals through the plants; however, heavy metals and soil particles are attracted to each other with positive and negative charges, so the heavy metals are not easy to move, making the costly Long rectification time. On the other hand, after a plant absorbs heavy metals, most of the heavy metals are concentrated in the roots of the plants, so the entire plant must be removed before the heavy metals can be removed from the soil. If the soil is too polluted, phytorejuvenation methods must be carried out multiple times, and plants must be replanted each time and the plants need to grow leaves, flower, or bear fruit. In this way, the overall rectification time that is repeatedly carried out is extended.

For this reason, it is indeed necessary to propose a new vegetative rejuvenation method to solve the problem of the currently used vegetative rejuvenation method.

The purpose of the present invention is to improve the problems of current phytoremediation methods for treating heavy metals in the soil, such as the excessive remediation time required for each phytoremediation method caused by poor mobility of heavy metals, and / or the entire plant must be moved In addition, the overall time required for remediation of the phytoremediation method is too long.

Therefore, in order to achieve the above and / or other objectives, the present invention proposes a method for removing heavy metals from soil, which includes: planting a plant in a soil contaminated with heavy metals; adding a fermentation broth to the soil, wherein the fermentation broth is cultured yeast Bacteria, lactic acid bacteria, photosynthetic bacteria, and Pseudomonas into a molasses broth until the pH of the molasses broth reaches below 4; cultivating the plant to its long leaves, flowering or fruiting; and removing the plant aerial .

According to the present invention, the fermentation broth used can promote the growth of plants to increase the tolerance of the plants to the poisons caused by heavy metals. In addition, 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 upper part of the plant. In this way, the effect of removing heavy metals from the soil can be achieved by directly removing the aerial parts after the plants are cultivated, and it is not necessary to remove the entire plant. If the soil is too polluted, continue to add the fermentation broth to carry out the next removal without necessarily re-planting the plants.

In order to make the foregoing and / or other objectives, effects, and features of the present invention more comprehensible, the preferred embodiments are described below in detail as follows:

An embodiment of the present invention provides a method for removing heavy metals from soil. This method transfers heavy metals from the soil to the above-ground parts of the plant through the planting of plants and the treatment of specific fermentation broth. Afterwards, heavy metals can be removed from the soil by directly removing the plant parts. The detailed steps related to the method mentioned in this embodiment are as follows:

First, grow plants in soil contaminated with heavy metals. In general, the life cycle of a herbaceous plant is shorter than that of a woody plant, and the above-ground part of an herbaceous plant is easier to remove than the above-ground part of a woody plant. Therefore, the plant used is preferably an herbaceous plant. Examples of plants can be, but are not limited to, rice, corn, Indian mustard, beetroot, sunflower, white grass, reed, prickly grass, broadleaf daisy, queen's sunflower, mandarin orange, small fruit leaf bead, arrow leaf anemone Ferns, Anchovies, Anchovies, Boston Ferns, Kidney Ferns, or Long Leaf Kidney Ferns; and examples of heavy metals can be, but are not limited to, cadmium, zinc, mercury, copper, lead, arsenic, nickel, chromium , Barium, selenium, or antimony. In addition, to promote plant growth, a fertilizer may be added to the soil before or during planting, and examples of the fertilizer may be, but not limited to, Bokashi fertilizer.

Secondly, a fermentation broth is added to the soil, wherein the fermentation broth is obtained by culturing yeast, lactic acid bacteria, photosynthetic bacteria, and Pseudomonas into a molasses broth until the pH of the molasses broth reaches 4 or less. In addition, in order to enlarge the volume of the fermentation broth so that the fermentation broth can be uniformly mixed with the soil, the fermentation broth can be mixed with an appropriate liquid before addition, such as water, physiological saline, liquid fertilizer, or other culture broth suitable for the growth of the mixed bacteria. In addition, in this embodiment, the fermentation broth adding step is performed on the 15th to 45th days after the plant growing step. In addition, in order to promote the ability of plants to absorb heavy metals, a chelating agent may be added to the soil when the fermentation broth is added in this embodiment, 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 plant is grown to its long leaves, flowering or fruiting. In addition, in the present embodiment, the same fermentation broth may be added to the soil every 4 to 14 days during the cultivation to maintain the concentration of the fermentation broth in the soil. Similarly, in order to maintain the concentration of the chelating agent in the soil, the same chelating agent may be added to the soil every 4 to 14 days during culture.

Finally, the plant ground is removed. The so-called "above-ground part" refers to the lower part of the plant, which mainly refers to the organs of the plant that are not buried in the soil, such as stems, leaves, flowers, fruits, or any composition thereof. It should be noted that the step of removing the above-ground plant can be performed by directly removing the above-ground plant and retaining the above-ground part in the soil, or directly removing the entire plant from the soil.

The following examples illustrate the invention:

＜ Preparation of cadmium metal contaminated soil ＞

First add deionized water to a soil and mix for about 1 week to maintain the soil field capacity of about 50%. After adding the cadmium nitrate solution to the soil, adjust the pH of the soil with lime and mix for 2 weeks to maintain the water capacity of the soil field at about 50%. Then, the soil was alternated between wet and dry 3 times to obtain soil contaminated with cadmium metal. If necessary, 200g of bosica fertilizer can be added in advance and mixed with the soil.

＜ The cultivation of rice and the addition of fermentation broth of beneficial bacteria ＞

After rice was planted in cadmium-contaminated soil for one month, the fermentation broth of beneficial mixed bacteria with pH below 4 was first mixed with water at a ratio of 1:50 to 1: 200 to obtain a diluted fermentation broth, and the diluted fermentation was then performed. Liquid is added to the soil; and the fermentation broth of beneficial mixed bacteria is prepared by culturing yeast, lactic acid bacteria, photosynthetic bacteria, and pseudomonas (hereinafter, the four strains are collectively referred to as "beneficial mixed bacteria") to a molasses culture Until the pH of the molasses broth reaches 4 or less. Next, culture according to the physiological characteristics of rice, and the same diluted fermentation broth is added to the soil every one week during the cultivation until the rice panicles are formed. If necessary, when adding a diluted fermentation broth, an EDTA solution with a content of 2 mmol / kg soil can be added to the soil; and the same amount of EDTA solution can be added to the soil every other week during the cultivation for a total of 3 weeks.

＜ Appearance of rice ＞

After 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; but under the same contamination with cadmium metal, soil added with diluted fermentation broth is better for soil growth than non-added soil. Table 1. Growth status of rice after cultivation in soil with different additives

＜ Analysis of Cadmium Metal Content ＞

After earing, 1 g of rice organs were taken. After adding 10 mL of nitric acid to each organ, let stand for 1 hour. Next, the obtained nitric acid solution was sequentially subjected to microwave treatment, filtration, and analysis to obtain the cadmium metal content of each organ of rice.

After earing, another 1 g of soil was taken. After adding 9 mL of nitric acid and 3 mL of hydrofluoric acid to the soil, let stand for 1 hour. After that, 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 the cadmium metal content of the soil.

As shown in Figure 1, compared to rice cultivated in soil without addition, rice cultivated in soil with only diluted fermentation broth can absorb a larger amount of heavy metals, and most of them are above ground, especially the stem has a higher concentration of heavy metals than roots. Heavy metal concentration. In addition, compared with the non-added soil, the amount of heavy metals absorbed by rice was slightly increased in the soil with diluted fermentation broth and chelating agent. Although the soils with diluted fermentation broth and bocasi fertilizer and the soils with diluted fermentation broth, chelating agent, and bocasi fertilizer promoted less absorption of heavy metals compared to soils without added fertilizer, the latter two were opposite. Plant growth is more beneficial than the former (Table 1).

Here, the following terms are introduced: BCF, full name bioconcentration factor, Chinese term "biological concentration factor", refers to the value obtained by dividing the concentration of heavy metals in the roots of plants by the concentration of heavy metals in the soil; TF, the full name is translocation factor, in Chinese As "plant transmission factor", it refers to the value obtained by dividing the concentration of heavy metals above the plant by the concentration of heavy metals at the root of the plant; BAF, full name is bioaccumulation factor, which is called "bioaccumulation factor" in Chinese, refers to the concentration of heavy metals above the plant The value obtained by the concentration of heavy metals in the soil, that is, the value obtained by multiplying BCF by TF.

From the above definition, 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 ground, and BAF represents the ability of heavy metals to transfer from the soil to the ground. It can be known from Table 2 that TF and BAF of the soil with the diluted fermentation broth are better than those without the addition of the soil, whether mixed with other substances or not. This means that dilute fermentation broth can promote the transfer of heavy metals from soil to above ground. Table 2. Distribution of cadmium metal after rice cultivation in soil with different additives

In summary, the fermentation broth of this embodiment can promote the growth of plants, so as to improve the tolerance of plants to poisons caused by heavy metals. In addition, 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 upper part of the plant. In this way, the effect of removing heavy metals from the soil can be achieved by directly removing the aerial parts after the plants are cultivated, and it is not necessary to remove the entire plant. If the soil is too polluted, continue to add the fermentation broth to carry out the next removal without necessarily re-planting the plants.

However, the above are merely preferred embodiments of the present invention, but cannot limit the scope of implementation of the present invention; therefore, any simple equivalent changes and modifications made in accordance with the scope of patent application and the contents of the invention specification of the present invention, All are still within the scope of the invention patent.

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Figure 1 is a bar graph illustrating the amount of cadmium metal absorbed by various organs of rice after treating the soil in different ways.

Claims (10)

A method for removing heavy metals from soil, comprising: planting a plant in soil contaminated by heavy metals; adding a fermentation broth to the soil, wherein the fermentation broth is cultured yeast, lactic acid bacteria, photosynthetic bacteria, and pseudomonas Into a molasses broth until the pH of the molasses broth reaches below 4; growing the plant to its long leaves, flowering or fruiting; and removing the above-ground part of the plant. The method according to claim 1, wherein the plant is a herbaceous plant. The method according to claim 1, wherein the plant is selected from the group consisting of rice, corn, Indian mustard, beetroot, sunflower, white grass, reeds, pelagow grass, American broadleaf, queen kwai, and oleander , Small fruit leaves under beads, arrowleaf anchovy fern, anchovies fern, anemone fern, Boston fern, kidney fern, and longleaf kidney fern. The method according to claim 1, wherein the heavy metal is selected from the group consisting of cadmium, zinc, mercury, copper, lead, arsenic, nickel, chromium, barium, selenium, and antimony. The method according to claim 1, wherein before or during the step of planting, the method further comprises: adding a fertilizer to the soil. The method according to claim 5, wherein the fertilizer is Bokashi fertilizer. The method according to claim 1, wherein the above-ground part of the plant is a stem, a leaf, a flower, or a fruit. The method according to item 1 of the claim, wherein the fermentation broth adding step is performed 15 to 45 days after the plant growing step. The method of claim 1, wherein the step of cultivating the plant comprises: adding the same fermentation broth to the soil. The method according to claim 1, wherein the step of adding the fermentation broth further comprises: adding a chelating agent to the soil.