CN112521952A

CN112521952A - Soil passivation microcapsule and method for resource utilization of titanium gypsum

Info

Publication number: CN112521952A
Application number: CN202011404165.7A
Authority: CN
Inventors: 廖述成; 熊集兵; 俞润华
Original assignee: Suzhou Churun Environmental Remediation Technology Co ltd
Current assignee: Suzhou Churun Ecological Technology Co ltd
Priority date: 2020-12-07
Filing date: 2020-12-07
Publication date: 2021-03-19
Anticipated expiration: 2040-12-07
Also published as: CN112521952B

Abstract

The invention provides a soil passivation microcapsule, S1, titanium gypsum is crushed, sieved and dried to obtain titanium gypsum powder, and the titanium gypsum powder is uniformly mixed with biochar and/or powdered rock phosphate to obtain mixed powder; s2, dissolving grape polyphenol and sodium alginate in deionized water to obtain a solution A, adding the mixed powder obtained in the step S1 into the solution A, and performing ultrasonic treatment until the mixed powder is uniformly dispersed to obtain a feed liquid; s3, dissolving chitosan and calcium chloride in deionized water, and adjusting the pH value to 7-8 to obtain a solution B; and S4, dripping the solution B into the feed liquid at a constant speed by using a needle, stirring after dripping, standing for 20-40min, filtering and separating, collecting filtrate, washing separated capsule particles with water, and drying in vacuum to obtain the soil passivation microcapsule. The invention utilizes the titanium gypsum solid waste, promotes the plant growth, effectively treats the heavy metal pollution of the soil, plays a role of a soil conditioner, widens the use approach of the titanium gypsum, treats the waste with the waste and protects the environment.

Description

Soil passivation microcapsule and method for resource utilization of titanium gypsum

Technical Field

The invention relates to the technical field of environmental management, in particular to a soil passivation microcapsule and a method for resource utilization of titanium gypsum.

Background

Titanium gypsum, also known as red gypsum, is waste residue produced by adding lime (or carbide slag) to neutralize a large amount of acidic waste water and using dihydrate gypsum as a main component when titanium dioxide is produced by a sulfuric acid process. 4-5 tons of titanium gypsum can be produced when 1 ton of titanium dioxide is produced, along with the increasing material demand of people and the high-speed development of the coating industry, more and more countries pay more and more attention to the solid waste treatment problem at present, the supervision and punishment on solid waste discharge and treatment are increased, manufacturers are forced to actively search for a new waste residue treatment mode, and the resource utilization problem of the titanium gypsum becomes more important. Compared with other industrial byproduct gypsums which are mature in application, such as desulfurized gypsum, phosphogypsum and the like, the titanium gypsums are large in water content, low in mechanical strength and low in gypsum purity, so that the titanium gypsums are narrow in usable range and are limited by a plurality of factors. Titanium gypsum is the industrial byproduct gypsum with the lowest utilization rate at present, so that huge resource waste is formed. At present, titanium gypsum is applied to the aspects of manufacturing cementing materials and cement retarders, and is hardly utilized as a large-scale effective resource. Titanium gypsum is piled up as an industry solid waste, not only occupies a large amount of land, causes environmental risks such as secondary raise dust through blowing and solarization, but also causes great economic burden for titanium white powder enterprises. Meanwhile, when the titanium gypsum is used for land landfill, heavy metals contained in the titanium gypsum can possibly cause underground water pollution, vegetation pollution and soil pollution, so that the research on how to further apply the titanium gypsum improves the resource utilization rate, reduces the environmental risk, changes waste into valuables and reduces the enterprise burden is the future research direction of titanium gypsum disposal.

The titanium gypsum contains calcium sulfate dihydrate as main component, and also contains metal elements such as Ti, Fe, Al and Mg and non-metal elements such as S, Si. Under the condition that the sources of iron ore concentrates are different, some iron gypsum contains a small amount of heavy metal substances, and the radioactive pollution of titanium gypsum is not reported in China at present. The dried titanium gypsum contains about 75 percent of calcium sulfate and about 25 percent of iron floccule, and the high impurity content and the high water content of the titanium gypsum are one of the main limitations of the recycling of the titanium gypsum. The researches of M.J.Gazzez and the like show that when the titanium gypsum is actually used, metal elements contained in the titanium gypsum enter the environment and cannot enable metal ions in water and soil to exceed the minimum harmful standard, so that the titanium gypsum can be directly used for building materials, soil remediation and the like, and other procedures are not needed for removing the metal ions. From the aspect of environmental influence, the iron gypsum belongs to alkalescent substances and can be used as a substrate for directly planting crops in a PH range suitable for plant growth. From the viewpoint of soil fertility, the titanium gypsum is rich in medium and trace nutrient elements such as calcium, magnesium, iron, manganese and the like for promoting plant growth, and has the potential of improving the soil fertility. The titanium gypsum is used for soil improvement, the crop yield can be improved to a certain extent, no adverse effect is caused on crop growth and soil environment, and researches show that natural greening can be carried out in ten years after the titanium gypsum is used as a refuse landfill, and natural tree succession is established. By combining the influence factors of the cadmium form change of the soil, the iron gypsum is added, so that the PH value of the soil can be effectively improved, the cadmium form of the soil is promoted to change, the effective cadmium content of the soil and the cadmium content absorbed by crops are reduced, and the titanium gypsum has stable improvement effect. The main impurity component of the titanium gypsum, namely iron, exists in a colloid form with negative charges, so that the titanium gypsum has a strong adsorption effect on heavy metal ions with positive charges, and the improvement effect is better.

Because titanium gypsum contains more elements such as iron, sulfur and the like, and the excessive high concentration of iron, sulfur and the like has toxic action on plant growth and is not beneficial to plant growth. Due to the excellent properties of the biomass charcoal, such as high specific surface area, abundant gaps and surface functional groups, the biomass charcoal has wide attention in the direction of treating soil heavy metal pollution and land remediation, and a lot of researches have been made on the passivation effect of the biomass charcoal on cadmium transportation in a soil-crop system. The ground phosphate rock has large specific surface area, small particle size and strong adsorption and fixation effects, and is widely applied to the restoration of polluted soil. And the titanium gypsum is less researched for the in-situ remediation of the Cd pollution in the alkalescent soil.

Disclosure of Invention

The invention aims to provide a soil passivation microcapsule and a method for recycling titanium gypsum, which utilize the solid waste of the titanium gypsum, can promote plant growth and effectively treat heavy metal pollution of soil, play a role of a soil conditioner, combine an organic passivator and an inorganic passivator, effectively passivate heavy metal pollutants such as cadmium element and the like in the soil, lead the plant not to be easily enriched with heavy metals, can promote plant growth and development, provide suitable trace elements, widen the use approach of the titanium gypsum, treat the waste with the waste, protect the environment and have wide application prospect.

The technical scheme of the invention is realized as follows:

the invention provides a preparation method of a soil passivation microcapsule, which comprises the following steps:

s1, crushing titanium gypsum, sieving, drying to obtain titanium gypsum powder, and uniformly mixing the titanium gypsum powder with biochar and/or powdered rock phosphate to obtain mixed powder;

s2, dissolving grape polyphenol and sodium alginate in deionized water to obtain a solution A, adding the mixed powder obtained in the step S1 into the solution A, and performing ultrasonic treatment until the mixed powder is uniformly dispersed to obtain a feed liquid;

s3, dissolving chitosan and calcium chloride in deionized water, and adjusting the pH value to 7-8 to obtain a solution B;

and S4, dripping the solution B into the feed liquid at a constant speed by using a needle, stirring after dripping, standing for 20-40min, filtering and separating, collecting filtrate, washing separated capsule particles with water, and drying in vacuum to obtain the soil passivation microcapsule.

As a further improvement of the invention, the sieving screen is 200-500 meshes.

As a further improvement of the invention, the mass ratio of the titanium gypsum to the biochar to/or the powdered rock phosphate is 100: (80-120): (80-120).

As a further improvement of the present invention, the biochar includes but is not limited to peanut shell carbon, corn cob carbon, corn stalk carbon, rice stalk carbon.

As a further improvement of the invention, the powdered rock phosphate contains 10-35% of total phosphorus (phosphorus pentoxide).

As a further improvement of the invention, the mass ratio of the grape polyphenol, the sodium alginate, the chitosan and the calcium chloride is 100: (20-40): (70-120): (10-25).

The invention further protects the soil passivation microcapsule prepared by the preparation method.

The invention further protects the application of the soil passivation microcapsule in treating the soil with high cadmium pollution.

The invention further provides a method for resource utilization of titanium gypsum, which is characterized in that the soil passivation microcapsules are added into the soil with high cadmium pollution, uniformly mixed and paved on the surface of the soil with the thickness of 5-10 cm.

As a further improvement of the invention, the cadmium content in the high-cadmium polluted soil is that every 1kg of soil contains no less than 1mg of cadmium element.

The invention has the following beneficial effects: the invention utilizes the titanium gypsum solid waste, can promote plant growth and effectively treat soil heavy metal pollution, plays a role of a soil conditioner, combines organic and inorganic passivators, effectively passivates heavy metal pollutants such as cadmium element and the like in soil, is not easy for plants to enrich heavy metal, can promote plant growth and development, provides suitable trace elements, widens the use approach of the titanium gypsum, treats waste with waste, protects the environment and has wide application prospect.

The shell material of the soil passivation microcapsule prepared by the invention is chitosan and sodium alginate, the coating mixed powder comprises titanium gypsum powder, biochar and/or phosphate rock powder, when the microcapsule is added into soil, the titanium gypsum powder, the biochar and/or the phosphate rock powder are slowly released under the protection of the shell material, so that the slow release effect is achieved, the soil is improved for a long time, on the other hand, the microcapsule shell material has degradability, and after the content is completely dispersed, the shell material can be degraded by microorganisms, so that the environment is not damaged, and the environment is protected.

Drawings

FIG. 1 is an SEM image of soil-passivating microcapsules prepared in example 3 of the present invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The titanium gypsum of the inventive example was subjected to the basic composition analysis, and the results are shown in tables 1 and 2.

TABLE 1 titanium Gypsum composition Table

Table 2 table for detecting content of heavy metal elements in titanium gypsum

Unit: mg/kg

Analysis index	PH	Cadmium (Cd)	Chromium (III)	Mercury	Arsenic (As)	Lead (II)	Copper (Cu)	Nickel (II)	Zinc
										The result of the detection	7.15	0.18	150	0.114	10.4	28	12.5	20	96

Example 1 soil passivation microcapsules

S1, crushing 100g of titanium gypsum, sieving with a 200-mesh sieve, drying at 45 ℃ to obtain titanium gypsum powder, and uniformly mixing the titanium gypsum powder with 80g of charcoal to obtain mixed powder;

s2, dissolving 100g of grape polyphenol and 20g of sodium alginate in 100mL of deionized water to obtain a solution A, adding the mixed powder obtained in the step S1 into the solution A, and performing ultrasonic treatment until the mixed powder is uniformly dispersed to obtain a feed liquid;

s3, dissolving 70g of chitosan and 10g of calcium chloride in 100mL of deionized water, and adjusting the pH value to 7 to obtain a solution B;

Example 2 soil passivation microcapsules

S1, crushing 100g of titanium gypsum, sieving with a 200-mesh sieve, drying at 55 ℃ to obtain titanium gypsum powder, and uniformly mixing the titanium gypsum powder with 120g of phosphate rock powder (containing 10% of total phosphorus (phosphorus pentoxide)) to obtain mixed powder;

s2, dissolving 100g of grape polyphenol and 40g of sodium alginate in 100mL of deionized water to obtain a solution A, adding the mixed powder in the step S1 into the solution A, and performing ultrasonic treatment until the mixed powder is uniformly dispersed to obtain a feed liquid;

s3, dissolving 120g of chitosan and 25g of calcium chloride in 100mL of deionized water, and adjusting the pH value to 8 to obtain a solution B;

and S4, dripping the solution B into the feed liquid at a constant speed by using a needle, stirring after dripping, standing for 40min, filtering and separating, collecting filtrate, washing separated capsule particles with water, and drying in vacuum to obtain the soil passivation microcapsule.

Example 3 soil passivation microcapsules

S1, crushing 100g of titanium gypsum, sieving with a 500-mesh sieve, drying at 50 ℃ to obtain titanium gypsum powder, and uniformly mixing the titanium gypsum powder with 100g of biochar and 100g of phosphate rock powder (containing 35% of total phosphorus (phosphorus pentoxide)) to obtain mixed powder;

s2, dissolving 100g of grape polyphenol and 30g of sodium alginate in 100mL of deionized water to obtain a solution A, adding the mixed powder obtained in the step S1 into the solution A, and performing ultrasonic treatment until the mixed powder is uniformly dispersed to obtain a feed liquid;

s3, dissolving 100g of chitosan and 15g of calcium chloride in 100mL of deionized water, and adjusting the pH value to 7.5 to obtain a solution B;

s4, dripping the solution B into the feed liquid at a constant speed by using a needle, stirring after dripping, standing for 30min, filtering and separating, collecting filtrate, washing separated capsule particles with water, and drying in vacuum to obtain the soil passivation microcapsule, wherein an SEM picture of the soil passivation microcapsule is shown in figure 1, and the soil passivation microcapsule prepared by the method is basically circular and has the particle size of 10-50 mu m.

Example 4 soil passivation microcapsules

S1, crushing 100g of titanium gypsum, sieving with a 500-mesh sieve, drying at 50 ℃ to obtain titanium gypsum powder, and uniformly mixing the titanium gypsum powder with 100g of charcoal to obtain mixed powder;

and S4, dripping the solution B into the feed liquid at a constant speed by using a needle, stirring after dripping, standing for 30min, filtering and separating, collecting filtrate, washing separated capsule particles with water, and drying in vacuum to obtain the soil passivation microcapsule.

Test example: cabbage test

1. Materials and methods

1.1 Experimental materials

The soil is collected from Xuzhou local soil (0-20cm), and dead branches, broken stones, animal remains and other coarse residues are removed, naturally dried, and then screened by a 2.0 mm sieve for storage and later use. The biochar is prepared by drying wheat straws, carbonizing at 500 ℃ for 1 hour, naturally cooling, and sieving by a 2mm sieve. The titanium gypsum was obtained from Xuzhou titanium dioxide powder Mill. The powdered rock phosphate comes from a phosphate rock factory in Hubei.

2 method of experiment

2.1 culture of cadmium-contaminated soil

In the experiment, 0.275g of cadmium nitrate tetrahydrate is dissolved in 100mL of water to obtain a standard solution with the cadmium ion concentration of 1g/L for storage and standby application, the solution is added into the soil to be tested, mixed and stirred uniformly, deionized water is added by a weighing method to keep the soil water content of 70%, the soil is aged for one month at room temperature and then air-dried, and the ground soil is sieved by a 60-mesh sieve to prepare the cadmium-polluted soil for standby application.

The cadmium ion contamination concentration was 5mg/kg and a blank control was added to the soil.

2.3 Experimental recipe settings

The experiment was carried out by setting four groups of experiments, namely a blank group, a titanium gypsum group, an example 3 group and an example 4 group.

The blank group is quartz sand.

The titanium gypsum group is titanium gypsum powder obtained by crushing titanium gypsum, sieving with a 50-mesh sieve and drying at 50 ℃.

2.4 potting experiment

Adding the passivators into soil according to the addition amount of 9g/kg, uniformly mixing the passivators and the soil, and repeating the treatment three times by using a blank group without the passivators as a control experiment.

After the treatment is finished, uniformly sowing 10 Chinese cabbage seeds in each pot, randomly discharging the potted plants, continuously culturing 4 Chinese cabbage seedlings with good growth conditions in each pot after the Chinese cabbages emerge, watering by a weighing method at regular intervals to ensure that the water holding rate in the field is 70%, and not additionally fertilizing in the whole pot culture period. After the growth of the pakchoi is carried out for 8 weeks, the soil at the root part is shaken off and sealed and stored in a plastic bag, then the bag is washed for a plurality of times by tap water and deionized water, the bag is divided into two parts of the root part (inedible) and the overground part (edible), and the fresh weight of the overground part is weighed, recorded and compared. Deactivating enzyme of the aerial parts of the Chinese cabbage in a drying oven at 105 deg.C for 30min, baking at 70 deg.C to constant weight, pulverizing, grinding, and storing. And (4) respectively taking 100g of soil sample from each pot, air-drying, sieving, numbering and storing for later use.

2.5. Index testing and data analysis

The germination number is: the number of sprouts divided by the total number of seeds sowed; the pH of the soil (soil: deionization: 1:2.5) was measured by a pH meter. Measuring the fresh weight of the overground part of the pakchoi by adopting a one-ten-thousandth balance; the cadmium in different forms in the soil is extracted by adopting a BCR continuous extraction method, and the forms of the extractable cadmium are respectively as follows: weak acid is used for extracting cadmium in a reduced state, cadmium in an oxidizable state and cadmium in a residual state, and ICP-MS is used for measuring the concentration of the cadmium in different states so as to investigate the passivation effect of the passivator. Significant difference analysis single factor difference analysis was performed using statistical software SPSS 18.

3. Results and analysis

(1) Comparison of germination rates

The germination rate of potted plants with different cadmium pollution concentrations and passivant ratios in each treatment group reaches 100 percent.

(2) Fresh weight comparison of Chinese cabbage on the ground

TABLE 3

Treatment of	Average fresh weight (g)
		Blank group	2.072±0.211
Titanium gypsum group	2.508±0.251
		EXAMPLE 3 group	3.426±0.315^*
EXAMPLE 4 group	4.224±0.391^*

Note that: p is <0.5 compared to the blank group.

(3) pH value

TABLE 4

Note that: p is <0.5 compared to the blank group.

(4) Cadmium content of each form in soil

TABLE 5

Note that: p <0.5, p <0.01, compared to the blank group.

The more the residue state proportion in the form proportion of the heavy metal in the soil, the better the passivation effect.

4. Analysis of

(1) Compared with the blank control group, the overground parts of the pakchoi in the titanium gypsum group and the groups in examples 3 and 4 can obviously promote the growth of plants, and the fresh weight of the pakchoi is obviously increased compared with that of the blank control group under various cadmium pollution concentrations. (2) For cadmium-polluted soil with different concentrations, the passivator has a certain adsorption effect on cadmium, and the passivator has an obvious passivation effect within a certain range on cadmium pollution.

(3) For the soil with different cadmium pollution concentrations, the titanium gypsum powder can obviously reduce the cadmium content enriched in the roots and the overground parts of plants, the cadmium content in the biological effective state in the soil is obviously reduced, and the cadmium content in the iron-manganese combined state and the cadmium content in the residue state are increased; for the combined use of titanium gypsum powder and biochar, the combined use of organic and inorganic passivators has better effect on improving cadmium pollution than the single use of titanium gypsum powder, the content of cadmium in soil which is converted into a ferro-manganese combined state and a residue state in a biological effective state is more, and the effect of reducing plant enrichment is obvious; the combination of the titanium gypsum powder, the biochar and the phosphate rock powder provides more nutrient elements and fertility for soil, the combination of the three passivators has a better soil heavy metal passivation effect, and the effect of reducing the enrichment of plant heavy metal cadmium is more obvious.

Compared with the prior art, the method utilizes the titanium gypsum solid wastes, can promote plant growth, effectively treat soil heavy metal pollution, play a role of a soil conditioner, combines organic and inorganic passivators, effectively passivates heavy metal pollutants such as cadmium element and the like in soil, ensures that plants are not easy to enrich heavy metals, can promote plant growth and development, provides proper trace elements, widens the use approach of the titanium gypsum, treats wastes with processes of wastes against one another, protects the environment, and has wide application prospect.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A method for preparing soil passivation microcapsules is characterized by comprising the following steps:

2. The method for preparing soil passivation microcapsules according to claim 1, wherein the sieve of step S1 is 200-500 mesh.

3. The method for preparing soil passivation microcapsules according to claim 1, wherein the mass ratio of the titanium gypsum, the biochar and/or the ground phosphate rock in the step S1 is 100: (80-120): (80-120).

4. The method for preparing soil-passivating microcapsules of claim 1, wherein the biochar includes, but is not limited to, peanut shell carbon, corn cob carbon, corn stover carbon, rice straw carbon.

5. The method for preparing soil passivation microcapsules according to claim 1, wherein the powdered rock phosphate contains 10-35% of total phosphorus (phosphorus pentoxide).

6. The method for preparing the soil passivation microcapsule according to claim 1, wherein the mass ratio of the grape polyphenol, the sodium alginate, the chitosan and the calcium chloride is 100: (20-40): (70-120): (10-25).

7. A soil-passivating microcapsule obtainable by the process for the preparation of a soil-passivating microcapsule according to any of claims 1 to 6.

8. Use of the soil passivating microcapsules of claim 7 for treating high cadmium contaminated soil.

9. A method for resource utilization of titanium gypsum, which is characterized in that the soil passivation microcapsules of claim 7 are added into soil polluted by high cadmium, uniformly mixed and paved on the surface of the soil to have a thickness of 5-10 cm.

10. The method of claim 9, wherein the cadmium content of the soil with high cadmium pollution is not less than 1mg of cadmium element in 1kg of soil.