Remediation composition for soil hexavalent chromium pollution and soil remediation method

Abstract

The invention provides a remediation composition for soil hexavalent chromium pollution and a soil remediation method. The composition comprises catechin, flavonoid isorhamnetin and humic acid according to the mass ratio of 1: (1-3): (0.1-1). According to the remediation composition for soil hexavalent chromium pollution, the leaching rate of the remediation composition for soil hexavalent chromium pollution can reach 93%, meanwhile, the composition can reduce more than 95% of hexavalent chromium in leacheate into low-toxicity trivalent chromium, the purpose of thoroughly removing hexavalent chromium in soil is achieved, and the material cost of chemical leaching is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of soil remediation, and in particular relates to a remediation composition for soil hexavalent chromium pollution and a soil remediation method. Background Art

[0002] Heavy metal pollution in soil has a long cycle, is difficult to degrade, and is difficult to manage. Chromium is an important industrial metal that is widely used in many industries, but high concentrations of chromium emissions can cause harm to the environment and human health, and may lead to water pollution, soil deterioration, vegetation death, animal death, and increase the risk of human disease. In particular, hexavalent chromium (Cr(VI)) is particularly harmful to the environment. Chromium pollution exists in water, soil, and the atmosphere in some areas, mainly concentrated in industrial parks, mining areas, and abandoned sites.

[0003] Compared with Cr 3+ ,Cr 6+ It is highly toxic, about Cr 3+ Chromium also causes persistent pollution to the soil and its surrounding environment. High concentrations of chromium can damage the surrounding ecosystem and groundwater resources, leading to environmental degradation and harming human health. People who are exposed to chromium-containing soil for a long time are prone to symptoms such as skin itching, allergies, ulcers and dermatitis.

[0004] Chromium in the soil often seeps into groundwater and surface water with rainwater, causing water pollution. Hexavalent chromium (Cr(VI)) is highly toxic to aquatic organisms, and long-term drinking of contaminated water may cause harm to human health. High concentrations of chromium pollution will also affect the growth of microorganisms in the soil, destroy the ecological balance of microorganisms in the soil, destroy the activity of soil enzymes, inhibit plants from absorbing nutrients and water, lead to a decline in soil quality, affect the ecological function of the soil, cause poor growth, reduced yields, or even death of crops, affect the fertility of the soil, and its ability to retain water and fertilizer, damage soil biodiversity and ecosystem stability, and affect the balance of the ecosystem. High concentrations of chromium pollution can cause the soil structure to become loose or crusty, reduce soil aeration, permeability, and fertilizer retention, accelerate soil degradation, and damage the soil ecological environment.

[0005] A large number of scholars at home and abroad have conducted relevant research on the remediation of soil contaminated by heavy metals. Soil leaching is an effective and easy-to-control remediation method that can be used to remove a variety of pollutants. It uses water, redox agents, surfactants, chelating agents or acid solutions to remove pollutants from contaminated soil. Through ion exchange, precipitation, adsorption and chelation, heavy metals in the soil are transferred from the soil to the liquid phase, and then recovered or treated from the leachate for final disposal.

[0006] The Chinese invention patent with application number CN201310493630.2 uses hydrochloric acid, reduced iron powder and sodium pyrofumate to wash hexavalent chromium contaminated soil, and the removal rate of hexavalent chromium is close to 90%. However, hydrochloric acid and sodium pyrofumate are highly destructive to the physical and chemical properties of the soil itself.

[0007] The Chinese invention patent with application number CN202410316068.4 uses microorganisms to treat hexavalent chromium-contaminated soil. The microbial cultivation period is long and the cost is relatively high. The introduced microorganisms may also have a negative impact on the local ecology.

[0008] Traditional chemical leaching technology causes serious secondary pollution to the soil, and biomass natural thermal component extraction materials also have a variety of functional groups such as hydroxyl and carboxyl that can chelate with heavy metal ions. Compared with traditional chemical leaching, it can efficiently leach heavy metals from the soil while being environmentally friendly and causing less disturbance to the soil, and has broad development prospects. Summary of the invention

[0009] In view of this, the present invention aims to overcome the defects in the prior art and proposes a soil remediation composition and a soil remediation method for hexavalent chromium pollution.

[0010] To achieve the above object, the technical solution of the present invention is achieved as follows: The invention provides a soil hexavalent chromium pollution repair composition, which comprises catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 1:1-3:0.1-1.

[0011] Furthermore, the mass ratio of the catechins, the flavonoid isorhamnetin and the humic acid is 1: 1.5-3: 0.1-0.6.

[0012] Furthermore, the molecular weight of the humic acid is 3000-5000. Within the above molecular weight range, humic acid has the best "mediating effect" and has the least interference with the soil.

[0013] The basic structure of humic acid macromolecules is an aromatic ring and an aliphatic ring, with hydroxyl, carboxyl, carbonyl, methoxy and other functional groups attached to the ring; there are also a certain amount of free radicals on the humic acid molecule. First, the carboxyl and phenolic hydroxyl groups in humic acid can dissociate into H + , reacts with hexavalent chromium ions to form a soluble complex, and then the phenolic hydroxyl group dissociates to form H + Afterwards, it can also provide electron pairs, which have ion exchange capacity and can further exchange H in catechins and flavonoid isorhamnetin. + , thereby promoting the release of H from catechins and flavonoid isorhamnetin +The ability of catechins and flavonoid isorhamnetin to react with hexavalent chromium ions to form soluble complexes; in addition, due to the strong adsorption effect of humic acid, it can promote the chelation of hexavalent chromium heavy metal ions by catechins and flavonoid isorhamnetin; finally, humic acid has hydrophilic-hydrophobic properties, containing both hydrophobic groups such as CH groups and aromatic structures, and hydrophilic groups such as carboxyl and hydroxyl groups, which enables humic acid to play a "mediating role" similar to detergent degreasing in the process of hexavalent chromium transferring from soil to water phase, thereby better washing hexavalent chromium out of soil.

[0014] The present invention also provides a leaching solution for soil hexavalent chromium contamination, wherein the leaching solution contains the repair composition, and the repair composition accounts for 0.1-5% of the total weight of the leaching solution.

[0015] The present invention also provides a method for preparing a soil hexavalent chromium contaminated eluent, comprising the following steps: Step 1 is to add catechin to deionized water, mix evenly, and obtain a catechin solution; add flavonoid isorhamnetin to deionized water, mix evenly, and obtain a flavonoid isorhamnetin solution; add humic acid to deionized water, mix evenly, and obtain a humic acid solution; Step 2 is to mix and stir the catechin solution and the flavonoid isorhamnetin solution evenly, and then inject the humic acid solution into them under heating and stirring conditions, and then obtain the eluent.

[0016] Furthermore, the temperature of the heating step in step 2 is 35-55°C; the flow rate of the injection step in step 2 is 50-100 mL / min. Under this condition, humic acid can more fully exchange H in catechins and flavonoid isorhamnetin. + .

[0017] The invention also provides a method for repairing hexavalent chromium contaminated soil, comprising the following steps: adding hexavalent chromium contaminated soil to the elution solution, oscillating and eluting, and then centrifuging and filtering.

[0018] Furthermore, the solid-liquid ratio of the hexavalent chromium contaminated soil to the elution solution is 0.5-5kg:20L.

[0019] Furthermore, the temperature of the oscillation elution step is 25-50°C, and the rotation speed is 180-360r / min; the time of the centrifugation step is 3-10min, and the rotation speed is 3000-9000r / min.

[0020] Furthermore, the filtering step uses a microporous filter membrane for filtering, and the pore size of the microporous filter membrane is 0.22-0.45 μm.

[0021] Compared with the prior art, the present invention has the following advantages: The composition for repairing hexavalent chromium pollution in soil of the present invention can achieve a leaching rate of 93% for hexavalent chromium pollution in soil. At the same time, the composition can reduce more than 95% of hexavalent chromium in the elution liquid to trivalent chromium with low toxicity, thereby achieving the purpose of completely removing hexavalent chromium in the soil and greatly reducing the material cost of chemical leaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A bar graph showing the elution rate of hexavalent chromium in soil according to an embodiment of the present invention; Figure 2 It is a bar graph of the hexavalent chromium reduction rate in the eluent described in the embodiment of the present invention. DETAILED DESCRIPTION

[0023] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0024] Preparation of hexavalent chromium contaminated soil described in each embodiment of the present invention and the comparative example: The test soil is yellow soil, collected from the lakeside of Tianjin University of Technology, Xiqing District, Tianjin (39°03'N, 117°06'E), remove large gravel and weeds and other foreign matter, dry naturally, pass through a 60-mesh nylon sieve, mix evenly and package for standby use. Weigh 2.829g of potassium dichromate (K2Cr2O7, high-grade pure) dried at 110°C for 2h, dissolve it in water, move it into a 1000ml volumetric flask, dilute it to the mark with distilled water, shake it well, and prepare a 1g / L chromium solution. Put the soil sample that has passed the 60-mesh nylon sieve into a tray, pour 1g / L chromium solution into it, and immerse the soil sample in the chromium solution. Air-dry and age it under natural conditions for 90 days, stir it every two days or so during the period, and use the weight method to ensure that the soil moisture content is about 50% to make the soil pollution uniform. After air-drying and aging, the soil is ground into powder using a high-speed grinder, dried, mixed, and stored in a plastic box in a cool place for later use.

[0025] The present invention will be described in detail below with reference to the embodiments.

[0026] Example 1

[0027] A soil hexavalent chromium contamination repair composition comprises catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 1:2:0.5.

[0028] A method for preparing a soil hexavalent chromium contaminated eluent comprises the following steps: Step 1 is to add 10g of catechin to 1000mL of deionized water, mix well to obtain a catechin solution, add 20g of flavonoid isorhamnetin to 1000mL of deionized water, mix well to obtain a flavonoid isorhamnetin solution, and add 5g of humic acid to 1000mL of deionized water, mix well to obtain a humic acid solution; Step 2 is to mix and stir the catechin solution and the flavonoid isorhamnetin solution evenly, and then inject the humic acid solution therein at a temperature of 40° C. at a flow rate of 50 mL / min, and after completion, the eluent is obtained.

[0029] A method for repairing hexavalent chromium contaminated soil comprises the following steps: adding 0.1 kg of hexavalent chromium contaminated soil into 2 L of the eluent, performing oscillation elution, the oscillation elution temperature is 30° C., the rotation speed is 260 r / min, and then performing centrifugation and filtration, the centrifugation time is 5 min, the rotation speed is 5000 r / min, and the pore size of the microporous filter membrane is 0.45 μm.

[0030] Example 2

[0031] The only difference from Example 1 is that the repair composition includes catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 1:1:0.5.

[0032] Example 3

[0033] The only difference from Example 1 is that the solid-liquid ratio of the hexavalent chromium contaminated soil to the elution liquid is 2 kg / 20 L.

[0034] Comparative Example 1 The only difference from Example 1 is that the repair composition includes catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 0.5:2:0.5.

[0035] Comparative Example 2 The only difference from Example 1 is that the repair composition includes catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 1:0.5:0.5.

[0036] Comparative Example 3 The only difference from Example 1 is that the repair composition includes catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 1:2:0.05.

[0037] Comparative Example 4 The only difference from Example 1 is that no catechin is added.

[0038] Comparative Example 5 The only difference from Example 1 is that the flavonoid isorhamnetin is not added.

[0039] Comparative Example 6 The only difference from Example 1 is that humic acid is not added.

[0040] Comparative Example 7 The only difference from Example 1 is that the solid-liquid ratio of the hexavalent chromium contaminated soil to the elution liquid is 9 kg / 20 L.

[0041] The above Examples 1-3 and Comparative Examples 1-7 were tested for hexavalent chromium elution rate in soil and hexavalent chromium reduction rate in elution solution. The results are as follows: Figure 1-Figure 2 As shown. Catechins and flavonoid isorhamnetin can promote each other to dissociate H + , react with hexavalent chromium ions to form soluble complexes, which can promote the chelation of hexavalent chromium heavy metal ions, thereby better washing hexavalent chromium out of the soil. In addition, it can be seen from the above-mentioned role of humic acid in the eluent that the comparative example cannot give full play to the synergistic effect of the three when the ratio of the three is not appropriate or a certain component is not added. The hexavalent chromium elution rate and the hexavalent chromium reduction rate in the eluent are obviously not as good as those in the embodiment, and when the solid-liquid ratio of the contaminated soil to the eluent is too high, that is, the eluent is insufficient, the hexavalent chromium elution rate and the hexavalent chromium reduction rate in the eluent will also show a significant decrease.

[0042] 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, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composition for repairing hexavalent chromium contaminated soil, characterized in that: The composition comprises catechin, flavonoid isorhamnetin and humic acid in a mass ratio of 1:1-3:0.1-1.

2. The composition for repairing hexavalent chromium contaminated soil according to claim 1, characterized in that: The mass ratio of the catechin, the flavonoid isorhamnetin and the humic acid is 1: 1.5-3: 0.1-0.

6.

3. The composition for repairing hexavalent chromium contaminated soil according to claim 1, characterized in that: The molecular weight of the humic acid is 3000-5000.

4. A leachate for treating hexavalent chromium contamination in soil, characterized in that: The eluent contains the repair composition according to any one of claims 1 to 3, and the repair composition accounts for 0.1-5% of the total weight of the eluent.

5. The method for preparing the soil hexavalent chromium contaminated eluent according to claim 4, characterized in that: The steps include: Step 1 is to add catechin to deionized water, mix evenly, and obtain a catechin solution; add flavonoid isorhamnetin to deionized water, mix evenly, and obtain a flavonoid isorhamnetin solution; add humic acid to deionized water, mix evenly, and obtain a humic acid solution; Step 2 is to mix and stir the catechin solution and the flavonoid isorhamnetin solution evenly, and then inject the humic acid solution into them under heating and stirring conditions, and then obtain the eluent.

6. The method for preparing a soil hexavalent chromium contaminated eluent according to claim 5, characterized in that: The temperature of the heating step in step 2 is 35-55° C.; the flow rate of the injection step in step 2 is 50-100 mL / min.

7. A method for repairing hexavalent chromium contaminated soil, characterized in that: The method comprises the following steps: adding hexavalent chromium contaminated soil to the elution liquid of claim 4, eluting by shaking, and then centrifuging and filtering.

8. The method for remediating soil hexavalent chromium pollution according to claim 7, characterized in that: The solid-liquid ratio of the hexavalent chromium contaminated soil to the elution solution is 0.5-5kg:20L.

9. The method for remediating soil hexavalent chromium pollution according to claim 7, characterized in that: The temperature of the oscillation elution step is 25-50°C, and the rotation speed is 180-360r / min; the time of the centrifugation step is 3-10min, and the rotation speed is 3000-9000r / min.

10. The method for remediating soil hexavalent chromium pollution according to claim 7, characterized in that: The filtering step uses a microporous filter membrane for filtering, and the pore size of the microporous filter membrane is 0.22-0.45 μm.

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