Preparation of Heavy Metal Passivation Materials from Biologically Domesticated Industrial Iron Mud and Its Application

Abstract

The present invention belongs to the field of heavy metal contaminated soil remediation, and discloses a method for preparing a heavy metal passivation material by biologically domesticating industrial iron sludge and its application. In the present invention, anaerobic granular sludge is placed in a reactor, and artificial simulated wastewater and industrial iron sludge are added for interaction. After being fully cultured and domesticated until mature, it is subjected to freeze-drying treatment to obtain the heavy metal passivation material. The present invention uses waste industrial iron sludge as a raw material, and improves the specific adsorption capacity of industrial iron sludge for heavy metals by means of biological domestication, which can enhance the removal effect of heavy metals in the aqueous phase. At the same time, the industrial iron sludge generates a bacterium-iron complex under the action of granular sludge microorganisms, which immobilizes heavy metals in the soil and forms stable secondary minerals, reducing the available state of heavy metals. The passivation material is applied to the remediation of heavy metal contaminated soil, and the passivation effect is remarkable.

Description

Technical Field

[0001] The present invention belongs to the field of heavy metal contaminated soil remediation, and particularly relates to a method for preparing a heavy metal passivation material from biologically domesticated industrial iron sludge and its application. Background Art

[0002] With the rapid development of industry and agriculture, soil heavy metal pollution has become increasingly serious and has received extensive attention. The main causes of soil heavy metal pollution are mainly natural sources and anthropogenic interference inputs. Compared with organic pollutants, heavy metals are not easily decomposed by soil microorganisms in the soil, but will be enriched through the food chain, having an important impact on human health. Therefore, the remediation of soil heavy metal pollution is extremely urgent. Currently, the main soil heavy metal pollution remediation technologies include: soil replacement method, solidification / stabilization, leaching technology, phytoremediation, etc. Among them, the solidification / stabilization technology has become a research and application hotspot due to its advantages such as simple operation, economy and high efficiency. The key to the remediation effect of the solidification / stabilization technology lies in the performance of the agent.

[0003] Iron-based materials have excellent characteristics such as high mechanical stability, good dispersion and suspension, large porosity, strong ion exchangeability and adsorption in the natural purification process of soil, and are widely used in the remediation of heavy metal contaminated soil. Industrial iron sludge has a wide range of sources, including chemical iron sludge, such as the waste residue generated in the process of preparing aromatic amines by reducing aromatic nitro compounds with iron powder; water treatment inorganic sludge, such as iron-containing sludge generated by iron-based coagulation, iron-carbon microelectrolysis, Fenton and other processes for water supply / wastewater treatment. The main components of industrial iron sludge include Fe(OH) x 3, organic matter, and also contain inorganic ions such as sulfate and phosphate.

[0004] However, granular sludge has received extensive attention due to its good biomass retention effect and good resistance to toxic and harmful substances. However, traditional granular sludge is prone to putrefaction and disintegration during storage, affecting its storage and use. Therefore, there is an urgent need to find a more stable sludge to meet the needs of large-scale soil remediation. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a method for preparing a heavy metal passivation material from biologically domesticated industrial iron sludge.

[0006] Another object of the present invention is to provide the heavy metal passivation material prepared by the above method.

[0007] Another object of the present invention is to provide the application of the above heavy metal passivation material in the field of heavy metal contaminated soil remediation.

[0008] The objects of the present invention are achieved by the following solutions:

[0009] A method for preparing a heavy metal passivation material from biologically domesticated industrial iron sludge, comprising the following steps: placing anaerobic granular sludge in an upflow anaerobic sludge bed (USAB) reactor, adding artificial simulated wastewater and industrial iron sludge for interaction, and after sufficient cultivation and domestication to maturity, performing freeze-drying treatment to obtain the heavy metal passivation material.

[0010] The industrial iron sludge is industrial waste iron sludge, including chemical iron sludge, such as the waste residue generated in the process of preparing aromatic amines by reducing aromatic nitro compounds with iron powder; water purification sludge, such as iron-containing sludge generated by iron-based coagulation, iron-carbon microelectrolysis, Fenton and other processes for water supply / wastewater treatment; steel slag iron sludge, such as the iron-containing waste residue generated in the steelmaking process; iron sludge generated in the acid mine drainage (AMD) treatment section, such as the purified water iron sludge generated in the section of adding lime to acid mine drainage (AMD). Its main components are Fe(OH)3, iron oxides, organic matter, etc., and the iron content is 20-60 wt%.

[0011] Before adding the industrial iron sludge to the USAB reactor, the following pretreatment steps are also required: air-drying the industrial iron sludge, crushing and grinding it, and passing it through a 100-mesh sieve.

[0012] The moisture content of the anaerobic granular sludge is 80%-90%, and its volume accounts for 8%-10% of the reactor volume.

[0013] The COD:N:P ratio (mass ratio) of the artificial simulated wastewater is 200-300:5:1. It uses glucose and yeast extract as the main carbon sources, NH4Cl and KH2PO4 provide nitrogen and phosphorus sources, and trace elements Ca, Mg, Mn, Co, Zn, Cu are added. In addition, NaHCO3 is used as a buffer reagent to maintain the pH, so that the influent pH is within the range of 7.2-8.2.

[0014] The amounts of trace elements in the artificial simulated wastewater are: Ca 2+ : 30-50 mg / L, Mg 2+ : 60-100 mg / L, Mn 2 + : 1.0-1.2 mg / L, Co 2+ : 0.5-0.6 mg / L, Zn 2+ : 0.05-0.06 mg / L, Cu 2+ : 0.02-0.03 mg / L.

[0015] The dosages of the anaerobic granular sludge, artificial simulated wastewater and industrial iron sludge satisfy: the volume of the anaerobic granular sludge accounts for 8-10% of the USAB reactor volume; the volume of the artificial simulated wastewater accounts for 70-90% of the USAB reactor volume; the amount of industrial iron sludge is 5-20 g / L (calculated based on the volume of the artificial simulated wastewater).

[0016] The culturing and domestication refers to culturing for 7 to 28 days at 28 to 38 °C.

[0017] For the described UASB reactor, the UASB reactor includes a reactor main body part, a heat preservation device, a water inlet device and a gas discharge device, and the experimental influent water is artificial simulated wastewater.

[0018] A heavy metal passivation material prepared by the above method. The particle size of the heavy metal passivation material is preferably above 2 mm. The adsorption capacity of the heavy metal passivation material for heavy metal lead ions is 172.3 mg / g.

[0019] An application of the above heavy metal passivation material in the field of heavy metal contaminated soil remediation.

[0020] Preferably, the application of the heavy metal passivation material in the field of heavy metal contaminated soil remediation specifically includes the following steps: mixing the heavy metal passivation material and the contaminated soil evenly, so that the water content of the mixed soil is 20 to 80 wt%.

[0021] The addition amount of the heavy metal passivation material is 1 to 10 wt% of the amount of the contaminated soil used.

[0022] The described contaminated soil can be contaminated soil containing copper, lead or cadmium.

[0023] The mechanism of the present invention is as follows:

[0024] After the anaerobic granular sludge is domesticated, its specific surface area increases, the functional groups increase, and the environmental compatibility is good. It is an excellent carrier and has a strong adsorption capacity for heavy metals such as lead, cadmium and copper. Under the domestication of microorganisms in the anaerobic granular sludge, the industrial iron sludge undergoes a phase change transformation to form iron minerals with good mass transfer performance. Through the synergistic work of the iron minerals and the microorganisms in the sludge, the physical and chemical properties of heavy metals in the soil are adjusted and changed, so that a series of reactions such as adsorption, complexation precipitation, ion exchange and redox occur. The trivalent iron in the iron sludge promotes the aggregation of the sludge into clusters, and at the same time, the microorganisms in the sludge also produce a coating effect with the iron sludge as the carrier, which can coat the heavy metals in the soil and form stable secondary iron minerals, thereby reducing the bioavailability and mobility of heavy metals in the soil environment, and further reducing the toxicity of heavy metal elements to animals and plants, and realizing the effective passivation of heavy metals in the contaminated soil.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] The present invention uses industrial iron sludge and anaerobic granular sludge to interact with each other, and has the advantages of easy material collection, low price, no other heavy metals, no secondary pollution, no change in soil structure, turning the granular sludge into a useful material, etc.

[0027] The present invention fully exploits and uses industrial iron sludge and anaerobic granular sludge, and has the characteristics of inexpensive and easily available raw materials, simple preparation method, easy control, good heavy metal soil remediation effect of the prepared passivation material, long stabilization time, etc. The obtained passivation material is easy for large-scale industrial production and popularization and application, and has broad application prospects and practical value. Description of the Drawings

[0028] Figure 1 It is the appearance diagram of the passivation material prepared in Example 1.

[0029] Figure 2 It is the FTIR diagram of the passivation material prepared in Example 1 and the control sludge material, where a represents the passivation material prepared in Example 1, and b represents the control sludge material prepared in Example 1.

[0030] Figure 3 It is the XRD spectrum diagram of the passivation material prepared in Example 1, as well as the raw material industrial iron sludge and anaerobic granular sludge, where a represents the passivation material prepared in Example 1, b represents anaerobic granular sludge, and c represents industrial iron sludge.

[0031] Figure 4 It is the lead ion adsorption equilibrium curve diagram measured in Example 2, where a represents the passivation material prepared in Example 1, and b represents the control sludge material prepared in Example 1.

[0032] Figure 5 It is the heavy metal passivation morphology distribution diagram in the contaminated soil measured in Example 3, where (a) is the morphology distribution diagram of metal lead, (b) is the morphology distribution diagram of metal copper, and (c) is the morphology distribution diagram of metal cadmium. Detailed Embodiments

[0033] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto. Those not specified in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase. The anaerobic granular sludge is purchased from Taobao (https: / / m.tb.cn / h.fS60shX?sm = 02793c), and its main components are methanogens, acetic acid-producing bacteria, hydrolysis and fermentation bacteria, etc., with a particle size of 0.3 - 3 mm, a water content of 80 - 90%, and a sedimentation rate of 50 - 150 m / h; the industrial iron sludge is purified iron sludge, that is, the iron sludge generated in the process of adding lime to treat acidic mine drainage (AMD), and its iron content is 20 - 60 wt%.

[0034] Unless otherwise specified, the reagents used in the embodiments can be conventionally purchased from the market.

[0035] Example 1

[0036] This embodiment prepares a heavy metal passivation material.

[0037] (1) 40 g of industrial iron mud (iron content: 28.46 wt%) was taken, air-dried, crushed and ground, and passed through a 100-mesh sieve to obtain iron mud for use;

[0038] (2) 400 mL of anaerobic granular sludge was placed in a UASB reactor. The reactor was made of organic glass, with an inner diameter of 12 cm, an overall height of 40 cm, and a working volume of 5 L. 4 L of artificial simulated wastewater and iron sludge were added to interact with the anaerobic granular sludge. The COD:N:P ratio of the artificial simulated wastewater was 200:5:1, and the amount of trace elements in the wastewater was Ca 2+ :38mg / L, Mg 2+ :80mg / L, Mn 2+ :1.1mg / L, Co 2+ :0.6mg / L, Zn 2+ :0.05mg / L, Cu 2+ :0.03mg / L, the pH value of the wastewater is 7.8, and it is cultured at 30°C for 14 days. After it is fully cultured and matured, it is freeze-dried to form a bacteria-mineral complex, which is a passivation material for the remediation of heavy metal-contaminated soil. The particle size of the passivation material is preferably above 2mm.

[0039] (3) Setting up a control group: The control group is anaerobic granular sludge cultured without industrial iron mud, and the remaining culture conditions are the same as those in step (1) and step (2), to obtain a control sludge material.

[0040] Figure 1 This is an appearance picture of the passivation material prepared in this embodiment. It can be seen from the picture that the material is a relatively regular black ellipsoid, fluffy and porous. Figure 2 FTIR spectra of the passivation material prepared in this example and the control group are shown in FIG. 1 , which show that the passivation material prepared in this example contains more types and larger quantities of organic functional groups, which is beneficial to its heavy metal passivation effect. Figure 3 The XRD spectra of industrial iron mud, anaerobic granular sludge and the passivation material prepared in this example show that neither the industrial iron mud nor the anaerobic granular sludge has a peak that can reflect the mineral crystal form. There is no mineral in the entire system before biological domestication. After biological domestication, the XRD diffraction peak of the material prepared in this example is very obvious. It can be seen that the granular sludge successfully domesticated the industrial iron mud under anaerobic conditions and generated FeOOH and other iron oxides.

[0041] Example 2

[0042] This example is to use the passivation material prepared in Example 1 for an adsorption experiment of a heavy metal solution, and the specific steps are as follows:

[0043] (1) Preparation of heavy metal solutions: Prepare lead nitrate solutions with concentrations of 20, 40, 60, 80, and 100 mg / L respectively.

[0044] (2) Take 100 mL of lead nitrate solutions with concentrations of 20, 40, 60, 80, and 100 mg / L respectively. Add 50 mg of the passivation material prepared in Example 1 to the above solutions, then place them in a shaker at 30 °C and shake at a speed of 180 r / min. After 2 h, perform solid-liquid separation and measure the concentration of lead ions in the solution before and after the reaction.

[0045] (3) Set up a control group: Take 100 mL of lead nitrate solutions with concentrations of 20, 40, 60, 80, and 100 mg / L respectively. Add 50 mg of the control sludge material prepared in Example 1 to the above solutions, place them in a shaker at 30 °C and shake at a speed of 180 r / min. After 2 h, perform solid-liquid separation and measure the concentration of lead ions in the solution before and after the reaction.

[0046] In this example, the flame atomic absorption method is used to measure the concentration of Pb. The adsorption equilibrium curve is shown as Figure 4 shown. This comparison result shows that the passivation material prepared by the present invention can more efficiently adsorb heavy metals in the solution, and the adsorption capacity for lead ions is about 172.3 mg / g.

[0047] Example 3

[0048] This example is an experimental application of the passivation material prepared in Example 1 for passivating heavy metals in contaminated soil. The specific steps are as follows:

[0049] (1) Preparation of contaminated soil: Remove gravel, branches, grass roots and other debris from the soil, crush the soil clods and pass through a 100-mesh sieve. Prepare copper nitrate, lead nitrate, and cadmium nitrate solutions, uniformly irrigate them into the soil, and place them in a constant temperature and humidity experimental incubator for aging. Set the temperature at a constant 60 °C, adjust the humidification rate, and keep the soil moisture content at about 50 wt%. Stir evenly every day, measure and observe regularly until no crystals precipitate in the soil, and the error of the measured value within 3 days does not exceed 2%. The experimental duration is 30 days. The copper pollution content of this soil is 500 mg / kg, the lead pollution content is 300 mg / kg, and the cadmium concentration is 20 mg / kg.

[0050] (2) Add passivation material: Weigh 0.6 g of the passivation material prepared in Example 1 and 15 g of self-made heavy metal contaminated soil, stir evenly, add deionized water to keep the soil moisture content at 50 wt%, place it in a shaker at 30 °C and shake for 15 days at a speed of 180 r / min, and measure the passivation of heavy metals in the contaminated soil.

[0051] (3) Set up a control group: Weigh 0.6 g of the control sludge material prepared in Example 1 and 15 g of the self-made heavy metal-contaminated soil, stir evenly, add deionized water to keep the soil moisture content at 50 wt%, place it in a shaker at 30 °C and shake for 15 days at a rotation speed of 180 r / min, and measure the heavy metal passivation in the contaminated soil.

[0052] The BCR four-step extraction method is used to determine the heavy metal speciation distribution. Figure 5 Figure 15 is the heavy metal speciation distribution diagram of the self-made contaminated soil after 15 days and after adding the passivation material and the control material. Among them, the soil mixture refers to the contaminated soil prepared in this example, the industrial iron sludge solidification refers to adding industrial iron sludge to the contaminated soil, the control sludge material solidification refers to adding the control sludge material prepared in Example 1 to the contaminated soil, and the passivation material solidification refers to adding the passivation material prepared in Example 1 to the contaminated soil. Among them, (a) is the speciation distribution diagram of lead, (b) is the speciation distribution diagram of copper, and (c) is the speciation distribution diagram of cadmium. From Figure 5 it can be seen that after adding the passivation material prepared in Example 1, the dissolved state content of Cu, Cd, and Pb in the soil decreases, and the oxidizable state and residual state content increase. The passivation effect is significantly higher than that of the control group adding the control iron sludge and the control sludge. It shows that the passivation material of the present invention has the function of efficiently repairing heavy metal-contaminated soil.

[0053] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a heavy metal passivation material from biologically domesticated industrial iron mud, characterized in that It includes the following steps: Put anaerobic granular sludge into a USAB reactor, add artificial simulated wastewater and industrial iron sludge for interaction, and after cultivation and domestication, perform freeze-drying treatment to obtain the heavy metal passivation material; the main components of the industrial iron sludge are Fe(OH)3, iron oxides and organic matter, and the iron content is 20-60 wt%; The volume of the anaerobic granular sludge accounts for 8% - 10% of the reactor volume; the dosage of the artificial simulated wastewater is 70 - 90% of the UASB reactor volume; the dosage of the industrial iron sludge is 5 - 20 g / L based on the volume of the artificial simulated wastewater; The cultivation and domestication means culturing at 28 - 38 °C for 7 - 28 days.

2. A method for preparing a heavy metal passivation material by biologically domesticating industrial iron sludge according to claim 1, wherein: The industrial iron sludge is industrial waste iron sludge, and the iron content in the industrial iron sludge is 20 - 60 wt%; Before adding the industrial iron sludge into the USAB reactor, the following pretreatment steps are also required: air-dry the industrial iron sludge, crush and grind it, and pass it through a 100-mesh sieve.

3. A method for preparing a heavy metal passivation material by biologically domesticating industrial iron sludge according to claim 1, wherein: The water content of the anaerobic granular sludge is 80% - 90%, and its volume accounts for 8% - 10% of the reactor volume.

4. A method for preparing a heavy metal passivation material by biologically domesticating industrial iron sludge according to claim 1, wherein: The COD:N:P mass ratio of the artificial simulated wastewater is 200 - 300:5:

1. It uses glucose and yeast extract as carbon sources, NH4Cl and KH2PO4 to provide nitrogen and phosphorus sources, and adds trace elements Ca, Mg, Mn, Co, Zn, Cu. In addition, NaHCO3 is used as a buffer reagent to maintain the pH, so that the influent pH is within the range of 7.2 - 8.

2.

5. A method for preparing a heavy metal passivation material by biologically domesticating industrial iron sludge according to claim 4, wherein: The amounts of trace elements in the artificial simulated wastewater are as follows: Ca 2+ : 30 - 50 mg / L, Mg 2+ : 60 - 100 mg / L, Mn 2+ : 1.0 - 1.2 mg / L, Co 2+ : 0.5 - 0.6 mg / L, Zn 2+ : 0.05 - 0.06 mg / L, Cu 2+ : 0.02 - 0.03 mg / L.

6. A heavy metal passivation material prepared by the method according to any one of claims 1 - 5.

7. Application of the heavy metal passivation material according to claim 6 in the field of heavy metal contaminated soil remediation.

8. Use of the heavy metal passivation material according to claim 7 in the field of heavy metal contaminated soil remediation, characterized in that It includes the following steps: mix the heavy metal passivation material and the contaminated soil evenly. The addition amount of the heavy metal passivation material is 1 - 10 wt% of the amount of the contaminated soil, and the water content of the mixed soil is 20 - 80 wt%.

Images