CN101555548A - Method for improving bioleaching effect of municipal solid waste incineration flying ash - Google Patents

Abstract

The invention discloses a method for improving the biological leaching effect of municipal solid waste incineration fly ash, which relates to a method for combining biological desiliconization and bioleaching to leach heavy metals in waste incineration fly ash. The specific steps are: use silicate bacteria to carry out biological desilication treatment of fly ash, destroy the mineral lattice in fly ash to release more metal oxides; use Aspergillus niger to carry out bioleaching of fly ash after desilication treatment , because more heavy metal oxides can fully contact and react with the organic acid produced by Aspergillus niger, thus significantly improving the dissolution effect of heavy metals in the bioleaching process. The method is easy to operate, high in efficiency, economically feasible and safe, and is an environmentally friendly and effective method for removing heavy metals in waste incineration fly ash, and the leaching toxicity is far lower than the hazardous waste identification standard, and fly ash can enter landfill or further utilization of resources.

Description

A method for improving bioleaching effect of urban domestic waste incineration fly ash

technical field

The invention relates to a method for improving the heavy metal removal effect in the biological leaching treatment of municipal solid waste incineration fly ash.

Background technique

With the continuous rapid growth of China's economy and the rapid improvement of people's living standards, the problem of municipal solid waste disposal has become one of the most serious public hazards in China. Therefore, the rapid development of waste incineration power generation technology in China has also brought about a significant increase in the output of waste fly ash.

A large amount of ash is produced in the process of waste incineration, including slag (80-90%) and fly ash (10-20%), but the content of heavy metals in fly ash is several times or even hundreds of times larger than that of slag. The heavy metals in fly ash mainly come from waste paper, waste batteries, building decoration materials, and road cleaning garbage in daily life. In particular, the waste classification system in my country is not perfect, and industrial waste and medical waste are often mixed in urban domestic waste, making Heavy metal pollutants migrate and transform during the incineration process, which enriches the fly ash with high concentrations of heavy metals and other pollutants. If the fly ash is directly landfilled or handled improperly, in the natural environment, due to the effects of acid rain and other factors, the heavy metals will gradually leach out in the acidic environment, re-enter the environment, pollute the groundwater source and endanger human beings. Therefore, the "National Hazardous Waste List" "It has been clearly stipulated that the fly ash of domestic waste incineration is hazardous waste, that is, the code is HW18, and the disposal of fly ash must be carried out in strict accordance with the specifications of hazardous waste disposal.

Scholars at home and abroad have tried to apply Biohydrometallurgy Technology to the field of solid waste treatment, that is, Bioleaching, which uses bioleaching agents or microbial metabolites to interact with incineration fly ash to remove the A method of leaching heavy metals from a solid phase to a liquid phase. The method has the advantages of mild reaction, less acid consumption, environmental friendliness, no secondary pollution, and low operating cost. However, compared with the traditional chemical treatment method, there are still disadvantages such as lower treatment load, long treatment time, and unsatisfactory heavy metal dissolution rate.

Fly ash has a structure and composition similar to ores, mainly metal oxides and silicates. In the process of bioleaching, a large part of the metal oxides wrapped in the Si-O lattice is difficult to fully contact with the bacterial metabolites-organic acids, thus affecting the metal dissolution effect.

Contents of the invention

The purpose of the present invention is to use the characteristics of such bacteria that can destroy the Si-O bond of the silicate component in the fly ash, and adopt the method of combined leaching of biological desilication pretreatment and biological leaching to oxidize the wrapped metal in the fly ash The material is exposed and fully contacted with the organic acid, the metabolite of the bacteria during bioleaching, so as to improve the metal dissolution effect of bioleaching.

Concrete steps of the present invention are as follows:

(1) Biological desilication of fly ash using silicate bacteria

(a) Select a ring of activated silicate bacterial slant strains and insert them into 10-50mL seed culture medium, and culture them with constant temperature shaking at 25-35°C and 140-220r/min for 40-55h.

The composition of silicate bacteria seed medium is: sucrose 4.0～10.0g/L, yeast powder 0.5～2.0g/L, K ₂ HPO ₄ 1.0～3.0g/L, MgSO ₄ 7H ₂ O 0.2～0.6g/L L, CaCO ₃ 0.1~0.2g/L, FeCl ₃ ·6H ₂ O 0.005~0.010g/L, pH 7.5~8.5.

(b) above-mentioned seed liquid is inserted in the silicate bacteria liquid culture medium with the inoculation amount of 1～5% (v/v), and the filling liquid quantity of culture medium is controlled at 15～30% (v/v) of culture container ), at 25-35° C., 140-220 r/min, constant temperature shaking culture for 2-7 days. After the silicate bacteria enter the logarithmic growth phase, add 10-30g/L fly ash, continue shaking culture for 5-7 days, and carry out desilication treatment.

The composition of silicate bacteria liquid culture medium is: sucrose 5.0～10.0g/L, yeast powder 10.0～15.0g/L, Na ₂ HPO ₄ 1.0～3.0g/L, MgSO ₄ 7H ₂ O 0.2～0.8g/L L, FeCl ₃ ·6H ₂ O 0.005-0.010g/L, CaCO ₃ 0.05-0.15g/L, adjust the pH value to 6.0-8.0.

(2) Bioleaching of desiliconized fly ash by Aspergillus niger

(c) Aspergillus niger is cultured on a slant with PDA medium, cultured at 25-35° C. for 5-7 days, mature spores grow, and the spores are washed with sterile deionized water. The spore suspension was counted with a hemocytometer, and the spore concentration was adjusted to 1×10 ⁷ -2×10 ⁸ /mL with sterile deionized water. Among them, the components of the PDA slant medium are: 200-400 g/L of potatoes, 15-25 g/L of glucose, and 15-25 g/L of agar.

(d) Put the Aspergillus niger spore suspension (c) into the sucrose liquid culture medium to make the spore concentration 0.5-2.5× ¹⁰⁷ /mL, and cultivate it under constant temperature shaking at 25-35°C and 140-220r/min . After Aspergillus niger grows for 2-8 days and enters the acid production period, add fly ash (b) after desiliconization at a rate of 10-80 g of fly ash per L of liquid medium. Oscillating and leaching at constant temperature for 15 to 25 days at a rotating speed of 1/min.

The composition of the sucrose liquid medium is: sucrose 100～150g/L, NaNO ₃ 1.0～1.5g/L, KH ₂ PO ₄ 0.5～0.8g/L, MgSO ₄ 7H ₂ O 0.02～0.03g/L, KCl 0.02 ～0.03g/L, NH ₄ Cl 3～5g/L.

The advantages of the present invention are that the fly ash is biologically desiliconized by using silicate bacteria, destroying the mineral lattice in the fly ash to release more metal oxides, and improving the dissolution of heavy metals from domestic waste incineration fly ash by bioleaching Rate. The method is easy to operate, high in efficiency, economical, feasible and safe, and is an environmentally friendly and effective method for removing heavy metals from waste incineration fly ash. The heavy metals of the fly ash treated by this method are effectively removed, and the leaching toxicity is far lower than the hazardous waste identification standard, and the fly ash can be put into landfill or further resource utilization.

Description of drawings

Figure 1 shows the concentration and dissolution rate of heavy metals dissolved in non-desiliconized fly ash after AS 3.879 bioleachate.

Figure 2 shows the concentration and dissolution rate of heavy metals dissolved in fly ash after desiliconization through AS 3.879 bioleachate.

Figure 3 is a comparison of the dissolution rate of heavy metals after AS 3.879 bioleaching of non-desiliconized fly ash and desiliconized fly ash.

Detailed ways

Example 1

(1) Biological desilication of fly ash using silicate bacteria

(a) Pick a ring of the activated silicate bacteria SDB6 slant strain and inoculate it into 50 mL of seed culture medium, and incubate at 28° C. and 180 r/min constant temperature shaking for 48 hours. Among them, the composition of silicate bacteria seed medium is: sucrose 5.0g/L, yeast powder 1.0g/L, K ₂ HPO ₄ 2.0g/L, MgSO ₄ 7H ₂ O 0.5g/L, CaCO ₃ 0.1g /L, FeCl ₃ ·6H ₂ O 0.005g/L, pH 8.0.

(b) the seed liquid (a) is inserted in the silicate bacteria liquid medium with a volume ratio of 2% (v/v), and the liquid filling amount of the medium is controlled at 20% (v/v) of the culture container, Under the conditions of temperature 30° C. and rotational speed 180 r/min, constant temperature shaking culture was carried out for 3 days. Then, 10 g/L fly ash was added to the Erlenmeyer flask for desiliconization treatment for 5 days. Among them, the composition of silicate bacteria liquid medium is: sucrose 5.0g/L, yeast powder 10.0g/L, Na ₂ HPO ₄ 2.0g/L, MgSO ₄ 7H ₂ O 0.5g/L, FeCl ₃ 6H ₂ O 0.005g/L, CaCO ₃ 0.1g/L, adjust the pH value to 7.0. The sample without fly ash was used as a blank control to analyze the heavy metal content of fly ash without desiliconization treatment and fly ash after desiliconization treatment (see Table 1). The results showed that the content of heavy metals in fly ash after desiliconization was not much different from that before desilication, which indicated that the metabolites of silicate bacteria SDB6 could not react with heavy metal oxides and had only desilication effect on fly ash.

(2) Using Aspergillus niger AS 3.879 to carry out bioleaching of fly ash after desiliconization

(c) Aspergillus niger AS 3.879 was cultured on a slant with PDA medium, cultured at 28°C for 5 days, mature spores grew, and the spores were washed with sterile deionized water. The spore suspension was counted with a hemocytometer, and the spore concentration was adjusted to the desired value with sterile deionized water.

(d) Inoculate the Aspergillus niger spore suspension (c) into the sucrose liquid medium to make the spore concentration 1.7×10 ⁷ /mL, and cultivate at constant temperature and shaking at 30°C and 140r/min. Among them, the composition of sucrose liquid medium is: sucrose 120g/L, NaNO ₃ 1.5g/L, KH ₂ PO ₄ 0.5g/L, MgSO ₄ 7H ₂ O 0.025g/L, KCl 0.025g/L, NH ₄ Cl 4g/L, after Aspergillus niger grows for 4 days and enters the acid production period, add non-desiliconized fly ash and desiliconized fly ash (b) at the rate of 70g of fly ash per L of liquid medium, respectively. Constant temperature oscillation leaching at 30°C and 140r/min for 20 days.

Analyze the content of heavy metals in the biological leachate of non-desiliconized fly ash and fly ash after desiliconization (see Figure 1 and Figure 2). The results showed that the fly ash was biologically desiliconized by SDB6, and then bioleached by Aspergillus niger strain AS 3.879, and the combined treatment had a significant effect on the dissolution of heavy metals. Compared with non-desilication treatment, the dissolution rate of Cu, Mn, Cr, Zn and Fe increased by 49%, 48%, 35%, 26% and 21%, respectively. The total heavy metal dissolution rate also increased from 41% to 50% from undesiliconized, and the total amount of heavy metals in the leachate reached 1102.9mg/L. This is because the mineral structure of the fly ash after desiliconization is destroyed, and more heavy metal oxides can fully contact and react with the organic acids produced by the bacteria, thus significantly improving the dissolution effect of heavy metals in the bioleaching process. The content of heavy metals in the fly ash after desilication and bioleaching is greatly reduced (see Table 1). After the fly ash was tested by the toxic leaching procedure (TCLP), it was found that the leaching toxicity of heavy metals was far lower than the national standard (see Table 2).

Example 2

(a) the steps are the same as in Example 1; (b) the seed liquid (a) is inserted into the silicate bacteria liquid culture medium with a volume ratio of 2% (v/v), and the liquid filling amount of the culture medium is controlled at 20% (v/v) of the container was cultured with constant temperature shaking at a temperature of 25° C. and a rotation speed of 150 r/min for 5 days. Then, 20 g/L fly ash was added to the Erlenmeyer flask for desiliconization for 5 days. Wherein, the composition of the silicate bacteria liquid medium is the same as that in Example 1, and the pH value of the medium is adjusted to 7.5. (c) and (d) steps are all identical with embodiment 1. Figure 3 shows the leaching rate of heavy metals in the bioleachate of non-desiliconized fly ash and desiliconized fly ash. It can be seen that the bioleaching effect of heavy metals in fly ash after desiliconization is significantly higher than that of fly ash without desiliconization.

Table 1 Non-desiliconized fly ash, desiliconized fly ash and desiliconized fly ash after AS 3.879 bioleaching

Average value of heavy metal content in fly ash (mg/g)

Table 2 TCLP leaching toxicity of fly ash after desilication and AS 3.879 bioleaching (mg/L)

ND: not detected; NS: not listed

a Hazardous waste identification standard (leaching toxicity identification): GB 5085.3-2007

b Hazardous waste landfill pollution control standard: GB 18598-2001

Claims (5)

1. a method that improves bioleaching effect of municipal solid waste incineration flying ash is characterized in that, carries out according to the following steps:

(a) choose the good silicate bacteria slant strains of a ring activation and insert in 10～50mL seed culture medium, at 25～35 ℃, constant-temperature shaking culture 40～55h under the condition of 140～220r/min;

(b) inoculum size of above-mentioned seed liquor with 1～5% (v/v) inserted in the silicate bacteria liquid nutrient medium, the liquid amount of substratum is controlled at 15～30% (v/v) of culture vessel, at 25～35 ℃, constant-temperature shaking culture is 2～7 days under the condition of 140～220r/min.Treat that silicate bacteria wherein enters the logarithmic growth after date, add 10～30g/L flying dust, continue concussion and cultivated 5～7 days, carry out desiliconization and handle;

(c) aspergillus niger carries out slant culture with the PDA substratum, cultivates 5～7 days at 25～35 ℃, grows ripe spore, and with aseptic deionized water wash-out spore, spore suspension is counted with Hematocyte Counter, and regulates spore concentration to 1 * 10 with aseptic deionized water ⁷～2 * 10 ⁸Individual/mL;

(d) aspergillus niger spore suspension (c) is inserted in the liquid sucrose substratum, making spore concentration is 0.5～2.5 * 10 ⁷Individual/mL, constant-temperature shaking culture under 25～35 ℃, 140～220r/min condition, treated the aspergillus niger growth 2～8 days and entered to produce sour after date, the ratio that adds flying dust 10～80g in every L liquid nutrient medium adds flying dust (b) after the desiliconization, and constant temperature vibration leaching is 15～25 days under 25～35 ℃, 140～220r/min rotating speed.

2. a kind of method that improves bioleaching effect of municipal solid waste incineration flying ash according to claim 1 is characterized in that the composition of silicate bacteria seed culture medium is: sucrose 4.0～10.0g/L, yeast powder 0.5～2.0g/L, K ₂HPO ₄1.0～3.0g/L, MgSO ₄7H ₂O 0.2～0.6g/L, CaCO ₃0.1～0.2g/L, FeCl ₃6H ₂O0.005～0.010g/L, pH value 7.5～8.5.

3. a kind of method that improves bioleaching effect of municipal solid waste incineration flying ash according to claim 1, it is characterized in that, the composition of the silicate bacteria liquid nutrient medium that the biological desiliconization of flying dust is used is: sucrose 5.0～10.0g/L, yeast powder 10.0～15.0g/L, Na ₂HPO ₄1.0～3.0g/L, MgSO ₄7H ₂O 0.2～0.8g/L, FeCl ₃6H ₂O 0.005～0.010g/L, CaCO ₃0.05～0.15g/L regulates pH value to 6.0～8.0.

4. a kind of method that improves bioleaching effect of municipal solid waste incineration flying ash according to claim 1, it is characterized in that the aspergillus niger seed culture with the composition of PDA slant medium is: potato 200～400g/L, glucose 15～25g/L, agar 15～25g/L.

5. a kind of method that improves bioleaching effect of municipal solid waste incineration flying ash according to claim 1 is characterized in that the flying dust bioleaching with the composition of liquid sucrose substratum is: sucrose 100～150g/L, NaNO ₃1.0～1.5g/L, KH ₂PO ₄0.5～0.8g/L, MgSO ₄7H ₂O 0.02～0.03g/L, KCl 0.02～0.03g/L, NH ₄Cl3～5g/L.

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