CN114733897A - In-situ catalytic oxidation inactivation method for iron-sulfur oxidation acid-producing bacteria in extremely-acidified pyrite mountain soil - Google Patents

Abstract

The invention specifically relates to an in-situ catalytic oxidation inactivation method for iron-sulfur oxidation acid-producing bacteria in extremely acidified pyrite mine soil. The compound oxidizing agent is applied to the soil at a depth of 0-0.5m, and the piles are turned and mixed, sprayed with water, cured for 3-7 days, and then covered with lime to adjust the pH value of the surface layer. The invention utilizes the naturally occurring H ⁺ and Fe ²⁺ in the extremely acidic pyrite mine to catalyze the strong oxidation of hypochlorite, inactivate the iron-sulfur oxidative acid-producing microorganisms, thereby inhibiting soil acidification, and forms a covering layer to protect the lower soil to avoid Oxidative acidification. The method of the invention is simple to operate, the in-situ catalysis greatly reduces the demand for hypochlorite, greatly reduces the amount of lime compared with the simple lime covering technology, avoids the problem of soil compaction, has low input cost, good effect of inhibiting acidification, and is not easy to return to acid. , which can be used as a pretreatment step for the ecological restoration of extremely acidified pyrite mines.

Description

In situ catalytic oxidation inactivation method of iron-sulfur oxidative acid-producing bacteria in extremely acidified pyrite soil

technical field

The invention belongs to the technical field of mine ecological restoration, and in particular relates to an in-situ catalytic oxidation inactivation method for acid-producing bacteria by oxidation of iron and sulfur in extremely acidified pyrite soil.

Background technique

Acidification of mining waste is a very serious and increasingly important environmental problem in China and the world. Most non-ferrous metal ores exist as various types of metal sulfides, such as pyrite (FeS ₂ ), chalcopyrite (CuFeS ₂ ), sphalerite (ZnS), galena (PbS), arsenopyrite (FeAsS) )Wait. The sulfide in the exposed mine is oxidized and acidified under the action of air, water and microorganisms to form a high acidity (pH: 2.5-6) containing a large amount of sulfate (1000-130000mg/L) and heavy metal ions (200-2000mg/L). Leachate - Acid Mine Drainage (AMD). Once AMD occurs, process control is difficult and the treatment cost is high; it is potentially corrosive to urban drainage pipes; after entering the natural environment, it destroys the natural carbon cycle balance and seriously damages the surrounding water, soil, sedimentary systems and ecosystems.

The main source of AMD is the oxidation of sulfide minerals, especially pyrite mines. Pyrite (FeS ₂ ) is one of the main minerals that cause AMD. The generation of AMD is a combination of physicochemical and biological processes. When pyrite is exposed to the outside, preliminary chemical oxidation occurs under the combined action of oxygen and water (1); then Fe ²⁺ is further oxidized by O ₂ to Fe ³⁺ (2), resulting in Fe ^{3 +} oxide pyrite The velocity is 18-170 times that of molecular oxygen (3). Even so, the chemical oxidation process is still very slow.

FeS ₂ +7/2O ₂ +H ₂ O→Fe ²⁺ +2SO ₄ ^2- +2H ⁺ (1)

Fe ²⁺ +1/4O ₂ +H ⁺ →Fe ³⁺ +1/2H ₂ O (2)

FeS ₂ +14Fe ³⁺ +8H ₂ O→15Fe ²⁺ +2SO ₄ ^2- +16H ⁺ (3)

Geochemical studies have confirmed that the oxidation process of pyrite in nature is a slow chemical process and a fast microbial catalysis process. Under the catalysis of microorganisms, Fe ²⁺ was rapidly oxidized to Fe ³⁺ , which increased the oxidation rate of pyrite by 5 orders of magnitude. Therefore, the acidification process of _FeS2 is an indirect oxidation process mainly catalyzed by microorganisms, and the reaction rate is extremely fast. In addition, the oxidation of sulfur in pyrite also mainly depends on biological action. The abiotic oxidation of elemental sulfur in an acidic environment is inert, and microorganisms can directly use the reduced sulfur in the mine as an electron donor for growth. It produces sulfuric acid, which further acidifies the mine environment. Studies have confirmed that at pH 2 to 3, the abundance of iron-sulfur oxidation acid-producing microorganisms reaches 80% to 95%, which is the absolute dominant species in this environment. Therefore, such microorganisms not only play a crucial role in the oxidation and acidification of pyrite, but also become a key obstacle in the ecological restoration of extremely acidic pyrite.

The mechanism of action between microorganisms and pyrite can be divided into "contact" and "non-contact" mechanisms. "Contact mechanism" means that microorganisms directly adsorb on mineral surfaces through pili or secretions on their surfaces, and directly oxidize and dissolve metal sulfide lattices into metal ions and SO ₄ ^2- by means of their own enzyme system. This process can directly oxidize minerals without relying on and relying on the action of Fe ³⁺ ; the "non-contact mechanism" rapidly oxidizes Fe ²⁺ to Fe ³⁺ through free microorganisms in the catalytic system without direct contact with pyrite . Usually, these two mechanisms coexist in the oxidation process of pyrite.

Due to the strong pollution of AMD to the surrounding ecological environment, it is a worldwide problem to effectively control the acidification of pyrite waste. At present, the main methods used are physical isolation method and alkaline neutralization method. The physical isolation method is to cover one to several layers of inert materials on the surface of the acidic soil to form isolation layers such as low permeability sealing layer, moisture isolation layer, and anti-erosion layer. accomplish.

At present, the patent for soil remediation of extremely acidified mine wasteland has mainly adopted the alkaline neutralization method as the preliminary method of ecological reconstruction. Spread a layer of lime and fresh farmyard manure to balance the plants with sufficient density for 1 to 6 months. However, this method can only precipitate Fe ³⁺ by increasing the pH, thereby inhibiting part of the free iron-sulfur oxidation and acid-producing microorganisms, and has no obvious effect on the attached microorganisms; in order to control acid reflux, lime must be applied to the acidified soil for many times, and long-term application of lime Lime not only increases labor and material costs, but also causes soil compaction, accelerated soil magnesium and potassium leaching, and caused soil nutrient imbalance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of in-situ catalytic oxidation inactivation method of iron-sulfur oxidation acid-producing bacteria in extremely acidified pyrite soil in order to solve the above-mentioned problems, which can be used as a pretreatment step for ecological restoration of extremely acid pyrite mines, It avoids the phenomenon of acid reflux caused by the action of microorganisms in the subsequent ecological restoration process, thereby improving the efficiency of mine restoration and saving costs.

The object of the present invention is achieved through the following technical solutions:

A method for in-situ catalytic oxidation inactivation of iron-sulfur oxidative acid-producing bacteria in extremely acidified pyrite mine soil. The mixed oxidizing agent was applied to the soil at a depth of m, and the piles were turned and mixed, sprayed with water, cured for 3 to 7 days, and then covered with lime to adjust the pH value of the surface layer.

Wherein, the oxidizing agent is prepared by mixing 5-10 parts by weight of solid hypochlorite and 5 parts by weight of stabilizer.

Preferably, the hypochlorite solid includes sodium hypochlorite or calcium hypochlorite solid or a combination thereof, and the stabilizer is one or more mixtures of amino acid salt, polyphosphate, sodium silicate, and talc solid.

Preferably, the amount of oxidizing agent applied to the trimmed mine soil is 0.005-0.05% of the dry basis mass of the surface layer 0-0.5 m mine soil.

Preferably, the total amount of water sprayed into the trimmed mine soil is 20-30% of the dry basis mass of the mine soil.

Preferably, during the maintenance process, 0-0.5 m of soil on the surface of the mine is turned once a day, so that the porosity of the mixed soil after turning is 40-50%.

Preferably, the surface of the extremely acidified pyrite ore soil after the curing is covered with 1-2 cm of lime, and the pH of the surface soil is adjusted to 5-8, particularly preferably 6.5-8

Preferably, the extremely acidified pyrite mine is a pyrite mine with a soil pH of 1.5-3.0, and contains complex minerals of various components of phosphorus, sulfur, copper, lead, manganese and zinc.

Preferably, the content of iron-sulfur oxidizing acid-producing bacteria in the extremely acidified pyrite soil is 5×10 ³ to 1×10 ⁹ cells/g dry basis.

Preferably, the organic matter content in the extremely acidified pyrite soil is not higher than 5% of the dry basis, and the Fe ²⁺ concentration is 100-500 mg/kg.

Preferably, the surface conditioning of the extremely acidified pyrite mine soil includes removing stones, filling mining pits, and plowing the soil surface to a depth of 40-60 cm, and the corrected soil porosity is 40-50%.

The hypochlorite oxidant selected by the present invention has a high degree of adaptation to the extremely acidified mine soil environment. Low pH (1.5～3.0) can promote the growth of HOCl. A small amount of Fe ²⁺ in pyrite acts as a natural catalyst for HOCl, and a Fenton-like reaction occurs to generate reactive oxygen species. The reaction rate between Fe ²⁺ and HOCl is higher than that of Fe ^{2 +} is ₃ orders of magnitude larger than H2O2 _; no external catalyst is required.

The laboratory simulated the oxidation of FeS with an initial pH of 2.35 under A. ferrooxidans ( _Thiobacter ferrooxidans, one of the most common extreme acidophilic microorganisms in extremely acidic pyrite) as a control group; adding the present invention The extremely acidic pyrite pretreatment agent in ecological restoration was used as the experimental group. The experimental group: the initial pH was 2.35, and the pH was 2.32 after 45 days of culture; while the control group, the pH dropped to 1.82 after 45 days of culture.

The laboratory results show that 1) microorganisms are the most important factor for the continued acidification of pyrite; 2) the compound oxidizing agent can inactivate free and attached iron-sulfur oxidation and acid-producing microorganisms, greatly reducing the continued acidification of extremely acidic pyrite. possible, thus avoiding the problem of acid reflux after lime application.

Compared with the prior art, the present invention has the following beneficial effects:

(1) according to the growth characteristics of the iron-sulfur oxidizing microorganisms in the extremely acidified pyrite soil, the present invention adopts the iron-sulfur oxidizing microorganisms that are free and attached to the in-situ catalytic oxidation of hypochlorite, and solves the problem that the alkaline lime neutralization method is easy to acid reflux problem. After testing, after adding the acid mine leading agent in the present invention, both free and attached iron-sulfur oxidizing microorganisms are reduced by more than 99.9%.

(2) The present invention improves the stability of the pre-treatment agent by adding the stabilizer with the main components such as amino acid salt, polyphosphate, sodium silicate, talc, etc., avoiding stirring, spraying, temperature rise, direct sunlight Under other conditions, HOCl decomposes to ensure the effect of pretreatment agents and the safety of construction workers.

(3) The method of the present invention is simple, the in-situ catalytic oxidation effect is good, and it is especially suitable for extremely acidifying pyrite (pH 1.5-3.5); the cost is low, and no additional catalyst is needed except the basic oxidizing agent and stabilizer, which avoids the need for additional catalysts. Cost inputs and environmental pressures caused by metal ions.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments, but by no means limit the present invention.

Example 1

The implementation site is located in a pyrite acidified tailings pond. The tailings pond is typical pyrite (FeS ₂ ). An area of 100m × 50m was selected as the experimental site, and a 100m block adjacent to the experimental site was selected. An area with a size of ×50m served as its control. The original soil conditions in this area are very bad, the pH of tailings is as low as 2.52±0.45, the degree of soil acidification is very serious, and there is no plant growth in the area. The area is governed by the following method steps:

(1) Surface trimming of extremely acidified mine soil, removal of stones, and filling of mining pits.

(2) the soil surface ploughing depth is 0.5m in this test site, and the water addition amount of this batch of acidified tailings pond is calculated according to the moisture content required by the repair process to be 2500m ³ ; %～35%) 5.0 tons, and 2.5 tons of amino acid salts are mixed to obtain a compound oxidizing agent. Mix the agent with the mine soil being tumbled and spray 2500m ³ of water on the area. After 5 days of curing (mixing every day to ensure soil porosity of 40-50%), 1.5 cm of lime was covered on the soil surface, and the pH of the surface soil was adjusted to 7.02. Samples were taken to detect pH and the number of iron-sulfur acid-producing microorganisms before applying the compound agent, after curing for 5 days, and after covering with lime for half a year (covering the rainy season). The measured results are shown in Table 1.

Table 1 Comparison of indicators of extremely acidified pyrite mine soil between the control group and the experimental group

As shown in Table 1, after applying the compound oxidizing agent for 5 days, the inactivation efficiency of the iron-sulfur oxidation acid-producing microorganism was as high as 99.98%. The pH of the soil was increased to 3.02; while the pH of the control group and the acid-producing microorganisms of iron-sulfur oxidation did not change significantly during this period. After covering the two experimental areas with lime for half a year, it is necessary to explain the rainy season covered during this period. The pH of the control group dropped from 7.02 to 3.65, and the iron-sulfur oxidation acid-producing microorganisms remained at 4.5×10 ⁵ , and the phenomenon of obvious acid reflux occurred; The pH was stable at 6.98, and the iron-sulfur oxidation acid-producing microorganism was 1.5×10 ² . The experimental group stopped acidification, and no acid reflux phenomenon occurred.

Example 2

The implementation site is located in a compound iron ore acidified tailings pond, which not only contains a large amount of magnetite, but also some chalcopyrite and lead-zinc ore. An area of 80m × 50m was selected as the experimental site, and an area of 80m × 50m adjacent to the experimental site was selected as its control. The original soil conditions in this area are very bad, the pH of the tailings is as low as 3.02±0.56, the soil acidification degree is serious, and there is no plant growth in the area. The area is governed by the following method steps:

(1) Surface trimming of extremely acidified mine soil, removal of stones, and filling of mining pits.

(2) the soil surface ploughing depth is 0.5m in this experimental site, and the water addition amount of this batch of acidified tailings pond is calculated according to the moisture content required by the repair process to be 2000m ³ ; calcium hypochlorite solid (industrial grade, effective The chlorine content is 30% to 38%) 4.0 tons, and the amino acid salt is mixed with 2.0 tons to obtain a compound oxidizing agent. The agent is mixed with the mine soil being tumbled and 2000m3 ^of water is sprayed on the area. After 5 days of curing (mixing every day to ensure soil porosity of 40-50%), 1.5 cm of lime was covered on the soil surface, and the pH of the surface soil was adjusted to 7.82. Samples were taken to detect pH and the number of iron-sulfur acid-producing microorganisms before applying the compound agent, after curing for 5 days, and after covering with lime for half a year (covering the rainy season). The measured results are shown in Table 2.

Table 2 The index comparison between the control group and the experimental group in the extremely acidified pyrite mine soil

As shown in Table 2, after applying the compound oxidizing agent for 5 days, the inactivation efficiency of the iron-sulfur oxidation acid-producing microorganism was as high as 99.98%. The pH of the soil increased to 3.58; while the control group did not change significantly in pH and iron-sulfur oxidation and acid-producing microorganisms during this period. After the two experimental areas were covered with lime for half a year, it should be noted that the rainy season was covered during this period. The pH of the control group dropped from 7.82 to 3.96, and the iron-sulfur oxidation acid-producing microorganisms remained at 4.1×10 ⁵ , and an obvious acid reflux phenomenon occurred; the pH of the experimental group It was stable at 7.66, and the iron-sulfur oxidation acid-producing microorganism was 3.6×10 ² . The experimental group stopped acidification, and no acid reflux phenomenon occurred.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (10)

1. An in-situ catalytic oxidation inactivation method for iron-sulfur oxidation acid-producing bacteria in extremely acidified pyrite mountain soil is characterized in that the extremely acidified pyrite mine soil is subjected to surface finishing, an oxidation agent is compounded, the compounded oxidation agent is applied to the soil with the depth of 0-0.5 m of the finished mine soil, turning and mixing are performed, water is sprayed, maintenance is performed for 3-7 days, and then lime is covered to adjust the pH value of a surface layer;

wherein the oxidation medicament is prepared by mixing 5-10 parts by weight of hypochlorite solid and 5 parts by weight of stabilizer.

2. The method for in-situ catalytic oxidative inactivation of iron-sulfur oxidizing acid-producing bacteria in extremely acidified pyrite mountain soil as claimed in claim 1, wherein said hypochlorite solids comprise sodium hypochlorite or calcium hypochlorite solids or a combination thereof, and said stabilizer is one or more mixtures of amino acid salts, polyphosphate, sodium silicate, talc solids.

3. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria for oxidizing iron and sulfur in the extremely-acidified pyrite mountain soil according to claim 1, wherein the amount of the oxidant applied to the trimmed mine soil is 0.005-0.05% of the dry basis weight of the mine soil with the surface layer of 0-0.5 m.

4. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria for oxidizing iron and sulfur in the extremely-acidified pyrite mountain soil according to claim 1, characterized in that the total amount of water sprayed into the trimmed mine soil is 20-30% of the dry basis weight of the mine soil.

5. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria for oxidizing iron and sulfur in the extremely-acidified pyrite mountain soil as claimed in claim 1, wherein the maintenance process is performed once per day on the soil with the thickness of 0-0.5 m on the surface layer of the mine, so that the porosity of the mixed soil after pile-turning is 40-50%.

6. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria capable of oxidizing iron and sulfur in the extremely-acidified pyrite mountain soil according to claim 1, characterized in that lime with the thickness of 1-2 cm is covered on the surface of the extremely-acidified pyrite mountain soil after maintenance is completed, and the pH value of the surface soil is adjusted to 5-8.

7. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria for oxidizing iron and sulfur in the extremely-acidified pyrite mountain soil according to claim 1, wherein the extremely-acidified pyrite mine is a pyrite mountain with a soil pH of 1.5-3.0 and contains a composite mineral containing multiple components of phosphorus, sulfur, copper, lead, manganese and zinc.

8. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria for iron-sulfur oxidation in the extremely-acidified pyrite mountain soil as claimed in claim 1, wherein the content of the acid-producing bacteria for iron-sulfur oxidation in the extremely-acidified pyrite mountain soil is 5 x 10³～1×10⁹Per g of dry basis.

9. The in-situ catalytic oxidation inactivation method for the iron-sulfur oxidizing acid-producing bacteria in the extremely-acidified pyrite mountain soil as claimed in claim 1, wherein the organic matter content in the extremely-acidified pyrite mountain soil is not higher than 5% of dry basis, and Fe²⁺The concentration is 100-500 mg/kg.

10. The in-situ catalytic oxidation inactivation method for the acid-producing bacteria for oxidizing iron and sulfur in the extremely acidified pyrite hill soil as claimed in claim 1, wherein the surface modification of the extremely acidified pyrite hill soil comprises removing stones, filling mining pits, loosening soil surface to a depth of 40-60 cm, and modifying the soil porosity to 40-50%.