A Chemical-Microbial Synergistic Remediation Method for Hexavalent Chromium and Treatment Liquid

Abstract

The present invention discloses a chemical-microbial synergistic remediation method and treatment solution for hexavalent chromium, belonging to the technical field of hexavalent chromium pollution remediation. The present invention takes Penicillium oxalicum SL2 and nano-zero valent iron as the research objects and establishes a chemical-microbial synergistic remediation method. The remediation method provided by the present invention can completely reduce hexavalent chromium with a concentration of 200 mg / L in water within 24 h, reduce the soil hexavalent chromium concentration to 3.4 mg / kg (less than the soil pollution risk screening value of 5.7 mg / kg), and still be lower than 5.7 mg / kg after 360 d, verifying the long-term stability of the remediation method and the remediation products. In addition, Penicillium oxalicum SL2 not only has high hexavalent chromium reduction ability, but also can dissolve chromium-iron precipitate, drive the reduction of trivalent iron, activate nano-zero valent iron, and significantly improve the reaction activity of nano-zero valent iron. The synergistic remediation of Penicillium oxalicum SL2 and nano-zero valent iron can improve the reduction and stabilization efficiency of hexavalent chromium while reducing the treatment cost, and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of hexavalent chromium pollution remediation, and particularly relates to a chemical-microbial synergistic remediation method for hexavalent chromium and a treatment solution. Background Art

[0002] The problem of heavy metal pollution in soil in China is prominent, and chromium (Cr) is one of the main inorganic pollutants. Among the commodity types in China, chromium compound products account for about 15%. Among them, the chromium chemical industry, electroplating, and leather-making are the main industries, accounting for more than 70% of the total chromium consumption. The number of enterprises in the three chromium-related industries reaches tens of thousands. With the adjustment of China's industrial structure in recent years, a large number of enterprises have been shut down and relocated. Years to decades of extensive production have led to serious pollution of these legacy site plots, threatening human health and ecological safety. A large number of contaminated plots urgently need to be treated. Cr(VI) has strong migration ability, high toxicity, and is easy to cause cancer. It is one of the five heavy metals under key control in China. Cr(III) has low water solubility, weak migration ability, and cannot penetrate the cell membrane, and its toxicity is relatively low. Therefore, reducing Cr(VI) to less toxic Cr(III) is an important way for environmental chromium pollution treatment.

[0003] Soil chemical reduction and stabilization technology has been widely used in recent years. Common chemical agents for soil chromium pollution remediation include ferrous sulfate, iron-containing minerals, and sulfur-based materials (such as hydrogen sulfide and sulfite). The chemical reduction and stabilization technology has the advantages of high treatment efficiency and strong operability, but it has a large consumption of reagents, is prone to secondary pollution, and significantly changes the physical and chemical properties of the soil. In addition, the failure of chemical agents and the re-oxidation of reduction products affect the long-term effectiveness of soil chromium reduction and stabilization, resulting in the difficulty of a single chromium chemical reduction and stabilization technology to meet the requirements of soil hexavalent chromium risk control in construction land in China.

[0004] The participation of microorganisms can form sub-nanoscale trivalent chromium and reduce the probability of re-oxidation of trivalent chromium. However, its tolerance to chromium in complex environments is relatively low. The combination of microorganisms and chemical remediation technology is expected to break through the limitations of re-oxidation of chemical reduction products and low adaptability of microorganisms, and build a green, economic, and long-term soil chromium reduction and stabilization technology system.

[0005] Nanotechnology has sustainable competitiveness in multiple industrial application fields. The uniqueness of nanoparticles lies in their larger specific surface area and high reactivity, etc. Among them, nano zero-valent iron (nZVI) shows great potential in the remediation of hexavalent chromium in soil and solution. Nano zero-valent iron is an environmentally friendly material with excellent reaction life, good fluidity, low toxicity, controllable particle size and abundant surface active sites, and is an ideal material for the remediation of chromium-contaminated soil and groundwater. However, relevant studies have shown that nano zero-valent iron particles are prone to agglomeration and surface oxidation themselves, and chromium-iron precipitates adhere to the particle surface, hindering the reduction of hexavalent chromium and greatly reducing the reaction activity of nano zero-valent iron. Therefore, it is urgent to solve the problem that nano zero-valent iron is prone to passivation and inactivation during the remediation of hexavalent chromium-contaminated solution and soil, and to provide a synergistic remediation method for chromium-contaminated solution and soil that can dissolve chromium-iron precipitate and regenerate divalent iron to extend the reaction life of the material. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a chemical-microbial synergistic remediation method and treatment liquid for hexavalent chromium.

[0007] The specific technical solutions adopted by the present invention are as follows:

[0008] In the first aspect, the present invention provides a chemical-microbial synergistic remediation method for hexavalent chromium. Specifically, a treatment liquid obtained by mixing one of Penicillium oxalicum SL2 spore suspension or Penicillium oxalicum SL2 mycelial pellets with nano zero-valent iron particles is added to the hexavalent chromium pollutant to be remediated.

[0009] Preferably, the preparation method of the above-mentioned Penicillium oxalicum SL2 spore suspension is as follows: Penicillium oxalicum SL2 is inoculated into a potato dextrose agar medium, cultured in the dark and then inoculated into a sterile Triton X solution, and the spore suspension of Penicillium oxalicum SL2 is obtained after filtering the mycelium.

[0010] Preferably, the preparation method of the above-mentioned Penicillium oxalicum SL2 mycelial pellets is as follows: the above-mentioned Penicillium oxalicum SL2 spore suspension is inoculated into a potato dextrose liquid medium for pre-culture, and after the pre-culture is completed, it is rinsed with sterile water to obtain Penicillium oxalicum SL2 mycelial pellets.

[0011] Preferably, the culture temperature under the above-mentioned dark condition is 30 °C and the time is 7 d.

[0012] Preferably, the above-mentioned pre-culture time is 48 h.

[0013] Preferably, the preparation method of the above-mentioned nano zero-valent iron particles is as follows: under a nitrogen atmosphere condition, the particles prepared by the reduction of ferric chloride with potassium borohydride are dispersed in absolute ethanol, and nitrogen blowing treatment is carried out to obtain nano zero-valent iron particles.

[0014] Preferably, the above hexavalent chromium pollutant is soil, and the remediation method is as follows:

[0015] S1: Collect the original hexavalent chromium contaminated soil. After air-drying, grinding and passing through a 2.0 mm sieve, it is pretreated by gamma-ray irradiation to achieve the purpose of sterilization, and the hexavalent chromium contaminated soil to be treated is obtained.

[0016] S2: Spray a treatment solution containing Penicillium oxalicum SL2 spore suspension and nano zero-valent iron particles into the above-mentioned hexavalent chromium contaminated soil to be treated. After mixing evenly, it is repaired at 30 °C for 180 - 360 d; the addition amount of spores in the Penicillium oxalicum SL2 spore suspension is 10 8 spores / g soil; the addition amount of nano zero-valent iron particles is 4.0 g / kg soil.

[0017] Preferably, the above hexavalent chromium pollutant is water, and the remediation method is as follows:

[0018] Add glucose liquid medium to the hexavalent chromium pollutant water body to provide a carbon source, and then add a treatment solution containing Penicillium oxalicum SL2 mycelial pellets and nano zero-valent iron particles for remediation; the addition amount of the above Penicillium oxalicum SL2 mycelial pellets is 9 g / L; the addition amount of the above nano zero-valent iron particles is 0.2 g / L, and the remediation is carried out at 180 rpm and 30 °C for 24 h.

[0019] Furthermore, the glucose concentration in the above glucose liquid medium is 4.5 - 20 g / L.

[0020] In the second aspect, the present invention provides a treatment solution for remediating hexavalent chromium pollutants, which is obtained by mixing one of Penicillium oxalicum SL2 spore suspension or Penicillium oxalicum SL2 mycelial pellets and nano zero-valent iron.

[0021] The present invention has the following beneficial effects compared with the prior art:

[0022] (1) The chemical-microbial co-remediation method provided by the present invention has good remediation effects in both water bodies and soils. In the water body contaminated with hexavalent chromium, the synergistic remediation of Penicillium oxalicum SL2 and nano-zero-valent iron particles provided by the present invention can completely reduce hexavalent chromium with an initial concentration of 200 mg / L in the water body within 1 day; the remediation method provided by the present invention can reduce the soil hexavalent chromium concentration to 3.4 mg / kg, which is lower than the screening value of soil pollution risk for Class II construction land in China (5.7 mg / kg, see "Soil Environmental Quality - Risk Control Standards for Soil Pollution of Construction Land GB36600-2018" issued by the Ministry of Ecology and Environment). In order to evaluate the leaching rate of heavy metals in the hexavalent chromium-contaminated soil after remediation, the TCLP method was used for extraction. The results showed that the concentration of TCLP-extractable hexavalent chromium in the soil decreased from 7.7 mg / L to 0.09 mg / L after 180 days of remediation (lower than the limit value of Class V environmental quality standard for surface water in China, 0.1 mg / L, see "Surface Water Environmental Quality Standard GB3838-2002" issued by the former State Environmental Protection Administration), indicating that the harm of the remediated soil to groundwater and surface water was significantly reduced;

[0023] (2) The chemical-microbial co-remediation method provided by the present invention reduces the dosage of nano-zero-valent iron particles by involving the functional microorganism Penicillium oxalicum SL2 in the reduction and stabilization of hexavalent chromium. In addition, Penicillium oxalicum SL2 can dissolve the chromium-iron precipitate on the surface of nano-zero-valent iron, making the nano-zero-valent iron react sufficiently, and can reduce trivalent iron to activate nano-zero-valent iron, thus fully prolonging the service life of nano-zero-valent iron. It reduces the treatment cost while improving the reduction and stabilization efficiency of hexavalent chromium, is more environmentally friendly, and can avoid significant changes in soil physical and chemical properties and the occurrence of secondary pollution;

[0024] (3) The reduction products of the chemical-microbial co-remediation method provided by the present invention are stable. The reduction products of soil chromium involving only chemical agents are prone to re-oxidation, while the remediation method provided by the present invention is still relatively stable after 360 days of remediation, and the concentration of hexavalent chromium in the soil is lower than 5.7 mg / kg, indicating the long-term stability of the remediation agent and trivalent chromium products. Description of the Drawings

[0025] Figure 1 It is a transmission electron microscope image of Penicillium oxalicum SL2 under chemical-microbial co-remediation in Example 1.

[0026] Figure 2 It is the reduction rate of hexavalent chromium in the solution measured in Example 1 and Comparative Examples 1 and 2.

[0027] Figure 3 It is the total iron and divalent iron concentrations in the solution measured in Example 1 and Comparative Example 2.

[0028] Figure 4The concentrations of hexavalent chromium in the soil measured for Example 2, Example 3, and Comparative Examples 3-5.

[0029] Figure 5 The concentrations of ferrous iron in the soil measured for Example 2, Comparative Example 3, and Comparative Example 5. Detailed implementation manners

[0030] The present invention will be further described and explained below in conjunction with the accompanying drawings and specific implementation manners. The technical features of each implementation manner in the present invention can be combined correspondingly on the premise that there is no conflict with each other.

[0031] The Penicillium oxalicum SL2 strain used in the following examples of the present invention is preserved in the China Center for Type Culture Collection, with the preservation number CCTCC No: M 2014505, the strain name: Penicillium oxalicum SL2, and the preservation date: October 22, 2014. The rest of the reagents in the following examples can all be commercial products of analytical purity or above available on the market.

[0032] Example 1

[0033] This example provides a chemical-microbial synergistic remediation method for hexavalent chromium in water bodies, specifically as follows:

[0034] (1) Boil 200 g of potatoes for 30 min, filter through sterile gauze to obtain the supernatant, add 20 g of glucose, and make up the volume to 1000 mL. Sterilize the above mixture at 115 °C for 20 min to obtain potato dextrose liquid (PDL) medium; add 1.8% (w / v) agar to the above PDL medium to obtain potato dextrose agar (PDA) medium for culturing Penicillium oxalicum SL2; add 2 g of glucose to 100 mL of deionized water and sterilize at 115 °C for 20 min to prepare glucose liquid medium.

[0035] The glucose concentration in the above PDL medium, PDA medium, and glucose liquid medium is 20 g / L. Through experimental determination, the actual glucose concentration consumed by microorganisms during the culture process is 4.5 - 5.0 g / L. Therefore, in practical applications, directly adding glucose liquid medium with a concentration of 4.5 g / L to the water body can also meet the growth requirements of Penicillium oxalicum SL2.

[0036] (2) Weigh dried potassium dichromate (K 2 Cr 2 O 7) 5.66 g was placed in a 100 mL beaker. After adding 50 mL of deionized water and completely dissolving it, it was diluted to 100 mL in a volumetric flask to obtain a potassium dichromate standard solution with a concentration of 20 g / L.

[0037] (3) Penicillium oxalicum SL2 was inoculated into a potato dextrose agar (PDA) medium and cultured at 30 °C in the dark for 7 days to harvest fresh spores. The above fresh spores were extracted into a 0.05% sterile Triton X solution and filtered through sterile glass wool to obtain a Penicillium oxalicum SL2 spore suspension with a concentration of 10 8 spores / mL.

[0038] (4) 1 mL of the above Penicillium oxalicum SL2 spore suspension was inoculated into 99 mL of PDL medium, so that the addition amount of Penicillium oxalicum SL2 spores was 10 6 spores / mL. It was pre-cultured at 30 °C for 48 h and then rinsed 3 times with sterile deionized water to obtain Penicillium oxalicum SL2 mycelial pellets.

[0039] (5) Under a nitrogen (N 2 ) atmosphere, iron chloride (FeCl 4 ) was reduced by potassium borohydride (KBH 3 ·6H 2 O) to prepare particles dispersed in absolute ethanol, and then subjected to nitrogen blowing treatment to obtain nano zero-valent iron particles (nZVI). The nano zero-valent iron particles were sealed and stored in a -70 °C ultra-low temperature refrigerator for later use.

[0040] (6) 1 mL of the above potassium dichromate standard solution was measured and placed in a 250 mL conical flask, and 99 mL of glucose liquid medium was added to simulate a hexavalent chromium-contaminated water body, in which the concentration of hexavalent chromium was 200 mg / L. Penicillium oxalicum SL2 mycelial pellets and nano zero-valent iron particles were added to the above simulated hexavalent chromium-contaminated water body (where the addition amount of Penicillium oxalicum SL2 mycelial pellets was 9 g / L and the addition amount of nano zero-valent iron particles was 0.2 g / L), sealed with a breathable membrane, and placed in a constant temperature shaker (180 rpm, 30 °C) for 24 h of remediation.

[0041] (7) The supernatant in step (6) was taken regularly in a laminar flow hood, and the concentration of hexavalent chromium in the supernatant was measured by the diphenylcarbazide spectrophotometric method (see "Determination of hexavalent chromium in water - Diphenylcarbazide spectrophotometric method GB / T 7467 - 1987" of the Ministry of Ecology and Environment), and the total iron and divalent iron concentrations in the solution were measured by the o-phenanthroline spectrophotometric method (see "Determination of iron in water - o-phenanthroline spectrophotometric method HJ / T 345 - 2007" of the former State Environmental Protection Administration).

[0042] Example 2

[0043] This example provides a chemical-microbial synergistic remediation method for hexavalent chromium in soil (denoted as the SL2+nZVI group), which is as follows:

[0044] (1) Boil 200 g of potatoes for 30 min, filter through sterile gauze to obtain the supernatant, add 20 g of glucose, and make up the volume to 1000 mL. Sterilize the above mixture at 115 °C for 20 min to obtain potato dextrose liquid (PDL) medium; add 1.8% (w / v) agar to the above PDL medium to obtain potato dextrose agar (PDA) medium for culturing Penicillium oxalicum SL2.

[0045] The glucose concentration in the above PDL medium and PDA medium is 20 g / L.

[0046] (2) Inoculate Penicillium oxalicum SL2 into the PDA medium and culture it under dark conditions at 30 °C for 7 d to harvest fresh spores; filter the mycelium of the above fresh spores through sterile glass wool in 0.05% sterile Triton X solution to obtain a concentrated suspension of Penicillium oxalicum SL2 spores with a concentration of 10 10 spores / mL.

[0047] (3) Under a nitrogen (N 2 ) atmosphere, prepare nanoparticles by reducing ferric chloride (FeCl 4 ·6H 3 O) with potassium borohydride (KBH 2 ). Disperse the particles in absolute ethanol and perform nitrogen blowing treatment to obtain nano zero-valent iron particles (nZVI). Seal the nano zero-valent iron particles and store them in a -70 °C ultra-low temperature refrigerator for later use.

[0048] (4) Collect the original hexavalent chromium-contaminated soil (with a total chromium concentration of 314.1 mg / kg and a hexavalent chromium concentration of 187.1 mg / kg), air-dry, grind it through a 2.0 mm sieve, and then pre-treat it by gamma-ray (50 kGy) irradiation to obtain the hexavalent chromium-contaminated soil to be treated. Gamma-ray irradiation can achieve the purpose of sterilization while minimizing the disturbance to the basic physical and chemical properties of the soil, reducing the influence of indigenous microorganisms, and thus facilitating the colonization of the exogenous functional microorganism Penicillium oxalicum SL2.

[0049] (5) Weigh 50 g of the above hexavalent chromium-contaminated soil to be treated into a 250 mL beaker. Add the concentrated suspension of Penicillium oxalicum SL2 spores and nano zero-valent iron particles to 50% PDL medium through a 30 mL plastic spray bottle and evenly spray it onto the hexavalent chromium-contaminated soil (the final addition amount of spores in the Penicillium oxalicum SL2 spore suspension in the soil is 10 8(with 1.0×10⁶ spores / g soil and an addition amount of 4.0 g / kg of nano zero-valent iron particles), spray and stir simultaneously, seal the beaker with a breathable membrane, and place it in an artificial climate chamber (30 °C) for 180 d of remediation. Supplement the Penicillium oxalicum SL2 spore suspension and 50% PDL medium into the soil every 30 d. Control the moisture content at 15% (v / m), and supplement deionized water every week to compensate the samples to maintain the required moisture during the remediation period.

[0050] The above 50% PDL medium is diluted from PDL medium and sterilized deionized water at a ratio of 1:1 (v / v).

[0051] (6) Regularly take the soil samples in step (5), and use flame atomic absorption spectrophotometry (refer to "Determination of hexavalent chromium in soil and sediment - Alkaline solution extraction - Flame atomic absorption spectrophotometry HJ 1082 - 2019" of the Ministry of Ecology and Environment) to determine the concentration of hexavalent chromium in the soil; after the soil samples are extracted with 0.5 mol / L HCl, use phenanthroline spectrophotometry (refer to "Determination of iron in water - Phenanthroline spectrophotometry HJ / T 345 - 2007" of the former State Environmental Protection Administration) to determine the concentration of divalent iron in the soil.

[0052] Example 3

[0053] This example provides a chemical - microbial synergistic remediation method for hexavalent chromium in soil (denoted as SL2 + nZVI 360d group), which is as follows:

[0054] (1) Boil 200 g of potatoes for 30 min, filter through sterile gauze to obtain the supernatant, add 20 g of glucose and make up the volume to 1000 mL, and autoclave the above mixture at 115 °C for 20 min to obtain potato dextrose liquid (PDL) medium; add 1.8% (w / v) agar to the above PDL medium to obtain potato dextrose agar (PDA) medium for culturing Penicillium oxalicum SL2.

[0055] The glucose concentration in the above PDL medium and PDA medium is both 20 g / L.

[0056] (2) Inoculate Penicillium oxalicum SL2 into the PDA medium, culture it under dark conditions at 30 °C for 7 d, and harvest fresh spores; filter the mycelium of the above fresh spores through sterile glass wool in 0.05% sterile Triton X solution to obtain a concentrated solution of Penicillium oxalicum SL2 spore suspension with a concentration of 10 10 spores / mL.

[0057] (3) Under the atmosphere of nitrogen (N 2 ), reduce ferric chloride (FeCl 4 ) with potassium borohydride (KBH 3·6H 2 The particles prepared by the borohydride reduction method were dispersed in absolute ethanol and subjected to nitrogen blowing treatment to obtain nano zero-valent iron particles (nZVI). The nano zero-valent iron particles were sealed and stored in a -70 °C ultra-low temperature refrigerator for later use.

[0058] (4) The original hexavalent chromium contaminated soil (with a total chromium concentration of 314.1 mg / kg and a hexavalent chromium concentration of 187.1 mg / kg) was collected. After air-drying, grinding through a 2.0 mm sieve, it was pre-treated by gamma-ray (50 kGy) irradiation to obtain the hexavalent chromium contaminated soil to be treated. Gamma-ray irradiation can achieve the purpose of sterilization on the premise of reducing the disturbance of the basic physical and chemical properties of the soil, so as to reduce the influence of indigenous microorganisms, and thus is more conducive to the colonization of the exogenous functional microorganism Penicillium oxalicum SL2.

[0059] (5) Weighed 50 g of the above-mentioned hexavalent chromium contaminated soil to be treated into a 250 mL beaker. The concentrated suspension of Penicillium oxalicum SL2 spores and nano zero-valent iron particles were added to 50% sterile PDL medium through a 30 mL plastic spray bottle and evenly sprayed onto the hexavalent chromium contaminated soil (where the addition amount of spores in the Penicillium oxalicum SL2 spore suspension was 10 8 spores / g soil, and the addition amount of nano zero-valent iron particles was 4.0 g / kg). Stir while spraying, seal the beaker with a breathable film, and place it in an artificial climate chamber (30 °C) for 360 d of remediation. Every 30 d, the Penicillium oxalicum SL2 spore suspension and 50% PDL medium were supplemented to the soil. The moisture content was controlled at 15% (v / m), and deionized water was supplemented weekly to compensate for the samples to maintain the required moisture during the remediation period.

[0060] The above-mentioned 50% PDL medium was diluted from PDL medium and sterilized deionized water in a ratio of 1:1 (v / v).

[0061] (6) Regularly take the soil samples in step (5), and use flame atomic absorption spectrophotometry (see "Determination of hexavalent chromium in soil and sediment - Alkaline solution extraction - Flame atomic absorption spectrophotometry HJ 1082 - 2019" of the Ministry of Ecology and Environment) to measure the hexavalent chromium concentration in the soil; after the soil samples were extracted with 0.5 mol / L HCl, o-phenanthroline spectrophotometry (see "Determination of iron in water - o-phenanthroline spectrophotometry HJ / T 345 - 2007" of the former State Environmental Protection Administration) was used to measure the divalent iron concentration in the soil.

[0062] Comparative Example 1

[0063] Compared with Example 1, this comparative example provides a chemical-microbial synergistic remediation method for hexavalent chromium in water without adding nano zero-valent iron particles, which is as follows:

[0064] (1) Boil 200 g of potatoes for 30 min, filter through sterile gauze, take the supernatant, add 20 g of glucose, and make up the volume to 1000 mL. Autoclave the above mixture at 115 °C for 20 min to obtain potato dextrose liquid (PDL) medium; add 1.8% (w / v) agar to the above PDL medium to obtain potato dextrose agar (PDA) medium for culturing Penicillium oxalicum SL2; add 2 g of glucose to 100 mL of deionized water and autoclave at 115 °C for 20 min to prepare dextrose liquid medium.

[0065] The glucose concentration in the above PDL medium, PDA medium, and dextrose liquid medium is 20 g / L.

[0066] (2) Weigh 5.66 g of dried potassium dichromate (K 2 Cr 2 O 7 ) into a 100 mL beaker, add 50 mL of deionized water to completely dissolve it, and make up the volume to 100 mL in a volumetric flask to obtain a potassium dichromate standard solution with a concentration of 20 g / L.

[0067] (3) Inoculate Penicillium oxalicum SL2 into potato dextrose agar (PDA) medium and culture it in the dark at 30 °C for 7 d to harvest fresh spores; extract the above fresh spores into 0.05% sterile Triton X solution, filter the mycelium through sterile glass wool, and obtain a Penicillium oxalicum SL2 spore suspension with a concentration of 10 8 spores / mL.

[0068] (4) Inoculate 1 mL of the above Penicillium oxalicum SL2 spore suspension into 99 mL of PDL medium so that the addition amount of Penicillium oxalicum SL2 spores is 10 6 spores / mL. Place it in an environment at 30 °C for pre-culture for 48 h, then rinse it 3 times with sterile deionized water to obtain Penicillium oxalicum SL2 mycelial pellets.

[0069] (5) Measure 1 mL of the above potassium dichromate standard solution into a 250 mL conical flask, add 99 mL of dextrose liquid medium to simulate hexavalent chromium-contaminated water, where the concentration of hexavalent chromium is 200 mg / L. Add Penicillium oxalicum SL2 mycelial pellets to the above simulated hexavalent chromium-contaminated water, with the addition amount of Penicillium oxalicum SL2 mycelial pellets being 9 g / L, seal it with a breathable membrane, and place it in a constant temperature shaker (180 rpm, 30 °C) for remediation for 24 h.

[0070] (6) Regularly take the supernatant in step (5) in a laminar flow hood, and use the diphenylcarbazide spectrophotometry method (see "Determination of hexavalent chromium in water quality - Diphenylcarbazide spectrophotometry GB / T 7467 - 1987" of the Ministry of Ecology and Environment) to measure the concentration of hexavalent chromium in the supernatant, and use the phenanthroline spectrophotometry method (see "Determination of iron in water quality - Phenanthroline spectrophotometry HJ / T 345 - 2007" of the former State Environmental Protection Administration) to measure the total iron and divalent iron concentrations in the solution.

[0071] Comparative Example 2

[0072] Compared with Example 1, this comparative example provides a chemical - microbial synergistic remediation method for hexavalent chromium in water without adding Penicillium oxalicum SL2 mycelial pellets, which is as follows:

[0073] (1) Add 2 g of glucose to 100 mL of deionized water and autoclave at 115 °C for 20 min to obtain a glucose liquid medium, and the glucose concentration in the glucose liquid medium is 20 g / L.

[0074] (2) Weigh 5.66 g of dried potassium dichromate (K 2 Cr 2 O 7 ) into a 100 mL beaker, add 50 mL of deionized water to completely dissolve it, and then make up the volume to 100 mL in a volumetric flask to obtain a potassium dichromate standard solution with a concentration of 20 g / L.

[0075] (3) Under the atmosphere of nitrogen (N 2 ), prepare nanoparticles by reducing ferric chloride (FeCl 4 ·6H 3 O) with potassium borohydride (KBH 2 ), disperse the particles in absolute ethanol, and perform nitrogen blowing treatment to obtain nano - zero - valent iron particles (nZVI). The nano - zero - valent iron particles are sealed and stored in a - 70 °C ultra - low temperature refrigerator for later use.

[0076] (4) Measure 1 mL of the above potassium dichromate standard solution into a 250 mL conical flask, add 99 mL of glucose liquid medium to simulate hexavalent chromium - contaminated water, where the concentration of hexavalent chromium is 200 mg / L. Add nano - zero - valent iron particles to the above - mentioned simulated hexavalent chromium - contaminated water (the addition amount of nano - zero - valent iron particles is 0.2 g / L), seal it with a breathable membrane, and place it in a constant - temperature shaker (180 rpm, 30 °C) for 24 h for remediation.

[0077] (5) Regularly take the supernatant in step (3) in a laminar flow hood, and use the diphenylcarbazide spectrophotometric method (see "Determination of Hexavalent Chromium in Water Quality - Diphenylcarbazide Spectrophotometric Method GB / T 7467-1987" of the Ministry of Ecology and Environment) to measure the concentration of hexavalent chromium in the supernatant, and use the phenanthroline spectrophotometric method (see "Determination of Iron in Water Quality - Phenanthroline Spectrophotometric Method HJ / T 345-2007" of the former State Environmental Protection Administration) to measure the total iron and divalent iron concentrations in the solution.

[0078] As Figure 2 shown, when using the chemical-microbial synergistic remediation method provided in this example to remediate hexavalent chromium in water, the corresponding removal rate is calculated from the measured hexavalent chromium concentration. The results show that the reduction rate of hexavalent chromium in the solution in Example 1 can reach 100.0% at 24 h, while the reduction rates of hexavalent chromium in Comparative Example 1 and Comparative Example 2 are only 63.1% and 58.4% respectively at 24 h. It shows that the synergistic remediation method of Penicillium oxalicum SL2 and nano-zero valent iron particles has excellent hexavalent chromium reduction efficiency, which can completely reduce 200 mg / L of hexavalent chromium within 24 h, and the content of hexavalent chromium in the solution after remediation is less than 0.05 mg / L, lower than the Class II water standard of surface water environmental quality (see "Surface Water Environmental Quality Standard GB3838-2002" of the former State Environmental Protection Administration).

[0079] As Figure 3 shown, at 24 h of the reaction, the total iron concentration and divalent iron concentration in the water body of Example 1 are as high as 156.1 mg / L and 43.7 mg / L respectively, and the proportion of divalent iron in the total iron is 28.0%. While the total iron concentration and divalent iron concentration in the solution of Comparative Example 2 are 79.7 mg / L and 6.5 mg / L respectively. This shows that Penicillium oxalicum SL2 can dissolve more iron from the nano-zero valent iron particles and participate in the redox reaction process. Penicillium oxalicum SL2 can also reduce trivalent iron in the solution to divalent iron, and has a strong ability to promote the cycle of trivalent iron / divalent iron and activate nano-zero valent iron. As Figure 1 shown, it can be seen from the transmission electron microscope image of Penicillium oxalicum SL2 that the particles in the cells are the iron taken up and transported, proving that the combined action of Penicillium oxalicum SL2 and nano-zero valent iron particles has the ability to uptake and reduce trivalent iron.

[0080] Comparative Example 3

[0081] In this comparative example, compared with Example 2, a chemical-microbial synergistic remediation method for hexavalent chromium in soil without adding Penicillium oxalicum SL2 and nano-zero valent iron particles (denoted as the Control group) is provided, as follows:

[0082] (1) Collect the original hexavalent chromium contaminated soil (where the total chromium concentration is 314.1 mg / kg and the hexavalent chromium concentration is 187.1 mg / kg). After air-drying, grinding and passing through a 2.0 mm sieve, the soil is pretreated by gamma-ray irradiation (50 kGy) to obtain the hexavalent chromium contaminated soil to be treated. Gamma-ray irradiation can achieve the purpose of sterilization on the premise of reducing the disturbance of the basic physical and chemical properties of the soil, so as to reduce the influence of indigenous microorganisms, and thus is more conducive to the colonization of the exogenous functional microorganism Penicillium oxalicum SL2.

[0083] (2) Weigh 50 g of the above-mentioned hexavalent chromium contaminated soil to be treated into a 250 mL beaker, seal the beaker with a breathable membrane, and place it in an artificial climate chamber (30 °C) for 180 d of remediation. The moisture content is controlled at 15% (v / m), and deionized water is supplemented weekly to compensate for the sample to maintain the required moisture during the remediation period.

[0084] (3) Regularly take the soil samples in step (3), and use flame atomic absorption spectrophotometry (see "Determination of hexavalent chromium in soil and sediment - Alkaline solution extraction - Flame atomic absorption spectrophotometry HJ 1082 - 2019" of the Ministry of Ecology and Environment) to measure the hexavalent chromium concentration in the soil; after the soil samples are extracted with 0.5 mol / L HCl, o-phenanthroline spectrophotometry (see "Determination of iron in water - o-phenanthroline spectrophotometry HJ / T 345 - 2007" of the former State Environmental Protection Administration) is used to measure the divalent iron concentration in the soil.

[0085] Comparative Example 4

[0086] This comparative example provides a chemical-microbial synergistic remediation method for hexavalent chromium in soil without adding nano-zero valent iron particles (denoted as the SL2 group) compared with Example 2, specifically as follows:

[0087] (1) Boil 200 g of potatoes for 30 min, filter the supernatant through sterile gauze, add 20 g of glucose, and make up the volume to 1000 mL. Sterilize the above mixture at 115 °C for 20 min to obtain potato dextrose liquid (PDL) medium; add 1.8% (w / v) agar to the above PDL medium to obtain potato dextrose agar (PDA) medium for culturing Penicillium oxalicum SL2.

[0088] The glucose concentration in the above PDL medium and PDA medium is 20 g / L.

[0089] (2) Inoculate Penicillium oxalicum SL2 into the PDA medium, culture it under dark conditions at 30 °C for 7 d, and harvest fresh spores; after filtering the mycelium of the above fresh spores through sterile glass wool in 0.05% sterile Triton X solution, a concentrated suspension of Penicillium oxalicum SL2 spores with a concentration of 10 10 spores / mL is obtained.

[0090] (3) Collect the original hexavalent chromium contaminated soil (where the total chromium concentration is 314.1 mg / kg and the hexavalent chromium concentration is 187.1 mg / kg). After air-drying, grinding and passing through a 2.0 mm sieve, irradiate it with gamma rays (50 kGy) for pretreatment to obtain the hexavalent chromium contaminated soil to be treated. Gamma ray irradiation can achieve the purpose of sterilization on the premise of reducing the disturbance of the basic physical and chemical properties of the soil, so as to reduce the influence of indigenous microorganisms, and thus is more conducive to the colonization of the exogenous functional microorganism Penicillium oxalicum SL2.

[0091] (4) Weigh 50 g of the above-mentioned hexavalent chromium contaminated soil to be treated into a 250 mL beaker. Add the concentrated spore suspension of Penicillium oxalicum SL2 into 50% sterile PDL medium through a 30 mL plastic spray bottle and evenly spray it onto the hexavalent chromium contaminated soil. The addition amount of spores in the spore suspension of Penicillium oxalicum SL2 in the soil is 10 8 spores / g soil. Stir while spraying, seal the beaker with a breathable membrane, and place it in an artificial climate chamber (30 °C) for 180 d of remediation. Every 30 d, supplement the spore suspension of Penicillium oxalicum SL2 and 50% PDL medium to the soil. Control the water content at 15% (v / m), and supplement deionized water to the sample every week for compensation to maintain the required moisture during the remediation period.

[0092] The above 50% PDL medium is diluted from PDL medium and sterilized deionized water in a ratio of 1:1 (v / v).

[0093] (5) Regularly take the soil samples in step (4), and use flame atomic absorption spectrophotometry (see "Determination of hexavalent chromium in soil and sediment - Alkaline solution extraction - Flame atomic absorption spectrophotometry HJ 1082 - 2019" of the Ministry of Ecology and Environment) to measure the hexavalent chromium concentration in the soil; after the soil samples are extracted with 0.5 mol / L HCl, use phenanthroline spectrophotometry (see "Determination of iron in water - Phenanthroline spectrophotometry HJ / T 345 - 2007" of the former State Environmental Protection Administration) to measure the divalent iron concentration in the soil.

[0094] Comparative Example 5

[0095] This comparative example provides a chemical - microbial co - remediation method for hexavalent chromium in soil without adding the spore suspension of Penicillium oxalicum SL2 (denoted as the nZVI group) compared with Example 2, specifically as follows:

[0096] This example provides a chemical - microbial co - remediation method for hexavalent chromium in soil, specifically as follows:

[0097] (1) Under the atmosphere of nitrogen (N 2 ) through potassium borohydride (KBH 4)Reduction of iron(III) chloride (FeCl 3 ·6H 2 O) method, the prepared particles were dispersed in absolute ethanol and subjected to nitrogen blowing treatment to obtain nano zero-valent iron particles (nZVI). The nano zero-valent iron particles were sealed and stored in a -70 °C ultra-low temperature refrigerator for later use.

[0098] (2) Collect the original hexavalent chromium contaminated soil (with a total chromium concentration of 314.1 mg / kg and a hexavalent chromium concentration of 187.1 mg / kg). After air-drying, grinding and passing through a 2.0 mm sieve, it was pretreated by gamma-ray (50 kGy) irradiation to obtain the hexavalent chromium contaminated soil to be treated. Gamma-ray irradiation can achieve the purpose of sterilization on the premise of reducing the disturbance of the basic physical and chemical properties of the soil, so as to reduce the influence of indigenous microorganisms and facilitate the colonization of the exogenous functional microorganism Penicillium oxalicum SL2.

[0099] (3) Weigh 50 g of the above-mentioned hexavalent chromium contaminated soil to be treated into a 250 mL beaker. Add the nano zero-valent iron particles to 50% sterile PDL medium through a 30 mL plastic spray bottle and evenly spray it onto the hexavalent chromium contaminated soil. The addition amount of nano zero-valent iron particles is 4.0 g / kg. Stir while spraying. Seal the beaker with a breathable tissue culture sealing film composed of plastic and cotton sheets and place it in an artificial climate chamber (30 °C) for 180 days of repair. Supplement 50% PDL medium to the soil every 30 days. Control the moisture content at 15% (v / m), and supplement deionized water to the sample every week to compensate for the moisture required during the repair period.

[0100] The above 50% PDL medium was diluted from PDL medium and sterilized deionized water at a ratio of 1:1 (v / v).

[0101] (4) Regularly take the soil samples in step (3), and use flame atomic absorption spectrophotometry (see "Determination of hexavalent chromium in soil and sediment - Alkaline solution extraction - Flame atomic absorption spectrophotometry HJ 1082 - 2019" of the Ministry of Ecology and Environment) to measure the hexavalent chromium concentration in the soil; after the soil samples are extracted with 0.5 mol / L HCl, use phenanthroline spectrophotometry (see "Determination of iron in water - Phenanthroline spectrophotometry HJ / T 345 - 2007" of the former State Environmental Protection Administration) to measure the divalent iron concentration in the soil.

[0102] As Figure 4As shown, after 180 days of synergistic remediation by Penicillium oxalicum SL2 and nano-zero valent iron particles in Example 2, the concentration of hexavalent chromium in the soil can be reduced to 3.4 mg / kg. After 360 days of remediation in Example 3, the content of hexavalent chromium in the soil is 4.1 mg / kg (lower than 5.7 mg / kg), meeting the screening value standard for Class II construction land in China. In the treatment groups with only Penicillium oxalicum SL2 and nano-zero valent iron added in Comparative Examples 4 and 5, the concentrations of hexavalent chromium in the soil are 104.7 mg / kg and 31.6 mg / kg respectively. This indicates that the remediation effect of the combined treatment is better than that of the individual addition, and there is also a significant synergistic remediation effect during the process of soil chromium reduction and stabilization.

[0103] As Figure 5 shown, after 180 days of synergistic remediation by Penicillium oxalicum SL2 and nano-zero valent iron particles in Example 2, the concentration of divalent iron in the soil is 186.2 mg / kg, while the concentration of divalent iron in the soil detected in the control group without Penicillium oxalicum SL2 and nano-zero valent iron particles in Comparative Example 3 is 39.0 mg / kg, and the concentration of divalent iron in the soil in the treatment group with only nano-zero valent iron particles added in Comparative Example 4 is 105.5 mg / kg. The change of divalent iron content in the soil is similar to that in the solution system. The concentration of divalent iron in the combined treatment group is relatively high, which further indicates that the addition of Penicillium oxalicum SL2 prolongs the reaction activity of nano-zero valent iron particles, verifying that the two can synergistically remediate the hexavalent chromium-contaminated solution and soil.

[0104] In addition, Penicillium oxalicum SL2 not only has high efficiency in reducing hexavalent chromium, but also can dissolve chromium-iron precipitates, drive the reduction of trivalent iron, activate nano-zero valent iron, and significantly improve the reaction activity of nano-zero valent iron. The synergistic remediation of Penicillium oxalicum SL2 and nano-zero valent iron can improve the efficiency of hexavalent chromium reduction and stabilization while reducing the treatment cost, and has broad application prospects.

[0105] The above-described embodiments are only a preferred solution of the present invention, but it is not intended to limit the present invention. Those of ordinary skill in the relevant technical fields can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A chemical-microbial synergistic remediation method for hexavalent chromium, characterized in that, a treatment solution obtained by mixing one of Penicillium oxalicum SL2 spore suspension or Penicillium oxalicum SL2 mycelial pellets with nano zero-valent iron particles is added to the hexavalent chromium pollutant to be remediated; The preparation method of the Penicillium oxalicum SL2 spore suspension is as follows: Inoculate Penicillium oxalicum SL2 into a potato dextrose agar medium, cultivate it under dark conditions, and then extract it into a sterile Triton X solution. After filtering the mycelium, the Penicillium oxalicum SL2 spore suspension is obtained; The preparation method of the Penicillium oxalicum SL2 mycelial pellets is: inoculate the Penicillium oxalicum SL2 spore suspension into a potato dextrose liquid medium for preculture. After the preculture is completed, rinse it with sterile water to obtain Penicillium oxalicum SL2 mycelial pellets; The hexavalent chromium pollutant is soil, and the remediation method is as follows: S1: Collect the original hexavalent chromium contaminated soil, air-dry, grind it through a 2.0 mm sieve, and then irradiate it with gamma rays for pretreatment to achieve the purpose of sterilization, obtaining the hexavalent chromium contaminated soil to be treated; S2: Spraying a treatment solution containing Penicillium oxalicum SL2 spore suspension and nano zero-valent iron particles on the to-be-treated hexavalent chromium contaminated soil, mixing evenly, and then carrying out remediation at 30 °C for 180 - 360 d; the addition amount of spores in the Penicillium oxalicum SL2 spore suspension is 10 8 spores / g soil; the addition amount of the nano zero-valent iron particles is 4.0 g / kg soil; The hexavalent chromium pollutant is water body, and the remediation method is as follows: Add a glucose liquid medium to the hexavalent chromium pollutant water body to provide a carbon source, and then add a treatment solution containing Penicillium oxalicum SL2 mycelial pellets and nano zero-valent iron particles for remediation; the addition amount of the Penicillium oxalicum SL2 mycelial pellets is 9 g / L; the addition amount of the nano zero-valent iron particles is 0.2 g / L; the remediation is carried out at 180 rpm and 30 °C for 24 h.

2. According to the chemical-microbial synergistic remediation method for hexavalent chromium described in claim 1, characterized in that, the cultivation temperature under dark conditions is 30 °C and the time is 7 d.

3. According to the chemical-microbial synergistic remediation method for hexavalent chromium described in claim 1, characterized in that, the preculture time is 48 h.

4. According to the chemical-microbial synergistic remediation method for hexavalent chromium described in claim 1, characterized in that, the preparation method of the nano zero-valent iron particles is as follows: Under a nitrogen atmosphere, disperse the particles prepared by the potassium borohydride reduction of ferric chloride method in absolute ethanol, and carry out nitrogen blowing treatment to obtain nano zero-valent iron particles.

5. According to the chemical-microbial synergistic remediation method for hexavalent chromium described in claim 1, characterized in that, the glucose concentration in the glucose liquid medium is 4.5 - 20 g / L.

6. A treatment solution for remediating hexavalent chromium pollutants, characterized in that, the treatment solution is obtained by mixing one of Penicillium oxalicum SL2 spore suspension or Penicillium oxalicum SL2 mycelial pellets with nano zero-valent iron.

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