A cementing filling agent and a cementing filling method

Abstract

The invention discloses a cementing filler and a cementing filling method, and relates to the field of biomineralization technology. The cementing filler comprises a phytic acid hydrolysate, ammonia water and a MgCl2 solution; the phytic acid hydrolysate is obtained by catalyzing and hydrolyzing phytic acid with phytase. The invention utilizes phytase to catalyze the hydrolysis of an organic phosphorus substrate, quickly releases inorganic phosphate ions, and generates magnesium ammonium phosphate precipitation with ammonium ions and magnesium chloride under alkaline conditions. In this process, the generation of magnesium ammonium phosphate requires a weak alkaline environment, so an appropriate amount of ammonia water is used to maintain the weak alkaline environment, and ammonium ions can also be provided to generate magnesium ammonium phosphate. Compared with traditional cement-based cementing filling materials, the cementing filling material formed by the method avoids high energy consumption, high emissions and high alkaline environment, and meets the requirements of low carbon and environmental protection; at the same time, compared with MICP and EICP technologies, it avoids the problems of biological safety and poor stability of cementing filling materials, and meets the requirements of mine filling.

Description

Technical Field

[0001] The invention relates to the technical field of biomineralization, in particular to a cementing filler and a cementing filling method. Background Art

[0002] Large-scale underground coal mining will lead to problems such as overburden breakage, surface subsidence, groundwater system damage, and environmental pollution caused by tailings ponds. Backfill mining, as a green mining technology, is one of the important technical means to reduce the disturbance of mining to the overlying rock and environmental pollution, reduce the management cost of tailings ponds, and improve the safety and efficiency of underground mining. It has been widely used around the world. Cementing backfilling technology is one of the commonly used backfilling mining technologies. It is a backfilling mining method that mixes mining waste such as gangue, fly ash, and tailings aggregates from concentrators with cement-based binders to make a binder slurry, which is then transported to the underground for filling through a filling pipeline. At present, the binder widely used in mines is silicate cement or cement-based materials, but there are shortcomings such as high energy consumption, high emissions, and high alkaline environment in the production process, and the cementing cost accounts for a high proportion. For example, filling a large amount of silicate cement into the well will increase the alkalinity of groundwater, causing groundwater pollution; the increase in transportation distance will cause the cementitious slurry to settle and separate during transportation, causing serious pipe blockage problems; at the same time, the production of silicate cement will inevitably produce carbon emissions, causing greenhouse gas emissions pollution. Therefore, it is necessary to study new non-cement-based filling materials and supporting technologies that can replace silicate cement.

[0003] Microbial mineralization studies have shown that under specific environmental and nutritional conditions, some specific microorganisms (urease bacteria) in the natural environment can produce highly active urease through metabolism, and urease can decompose urea into NH4 through catalysis. + and CO3 2- ,CO3 2- By combining with Ca in the filling body or external Ca source 2+ Combined with other materials, CaCO3 crystal precipitation with cementing ability is generated, which can replace the binder of traditional filling materials. The technology of using microbial mineralization to promote carbonate crystallization, thereby achieving specific functions such as cementation and solidification of filling bodies, is called Microbial Induced Carbonate Precipitation (MICP) technology. MICP technology can generate a large amount of calcium carbonate precipitation in a short period of time. It has the advantages of high efficiency, low energy consumption, sustainable development, and no pollution to the environment. Therefore, it has attracted much attention from scholars at home and abroad. However, MICP technology usually requires a series of processes such as bacterial cultivation, preservation, and activation. This process requires providing culture fluid, oxygen, temperature, humidity, pH and other conditions suitable for bacterial growth in a strict sterile environment. This will inevitably increase the corresponding time and cost, and it is difficult to meet the requirements at the actual engineering site.

[0004] In recent years, studies have found that some beans, melons and other plant seeds also contain abundant urease. Therefore, based on the MICP technology, the plant-derived urease-induced carbonate precipitation (EICP) technology was proposed. This can avoid the time and cost of microbial cultivation, and there is no need to consider the interference of external environmental factors in the growth and division of microorganisms. It does not have biosafety risks and improves the efficiency of urease extraction. Compared with the MICP technology, the EICP technology selects free urease as a catalyst, eliminating the process of cultivating microorganisms and avoiding the problem of biosafety. In addition, the size of free urease is smaller than that of microbial cells, which is more conducive to penetration into the filling material. However, most mine wastewater exists in the form of acidic wastewater, but for MICP and EICP technologies, the long-term stability of heavy metal carbonate products under acidic conditions is poor, and the risk of heavy metal dissolution is high. In addition, the strength of carbonate precipitation cemented filling materials is low (generally less than 2MPa), which is difficult to meet the filling requirements. At the same time, the process also produces harmful byproducts NH4 + and NH3. There is sufficient literature to show that the stability of heavy metal phosphate minerals under acidic conditions is better than that of carbonate minerals, and the risk of heavy metal dissolution is lower. Therefore, it is feasible and safe to use heavy metal phosphate minerals as a binder for filling materials. Summary of the invention

[0005] The purpose of the present invention is to provide a cementitious filling agent and a cementitious filling method to solve the problems existing in the above-mentioned prior art. The method can replace the silicate cement filling method, avoid high energy consumption, high emissions and high alkalinity environment, meet the requirements of low carbon and environmental protection, and at the same time, the cementitious filling material formed by it has high stability and can meet the requirements of mine filling.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a cementing filler, comprising phytic acid enzymatic hydrolyzate, ammonia water and MgCl2 solution;

[0008] The phytic acid enzymatic hydrolyzate is obtained by catalyzing and hydrolyzing phytic acid with phytase.

[0009] Furthermore, the phytase is 3-phytase, 6-phytase or orthophosphate monoacyl hydrolase.

[0010] Furthermore, the mass ratio of phosphoric acid in the phytate hydrolyzate, NH3 in the ammonia water and MgCl2 in the MgCl2 solution is 1:1:1.

[0011] Furthermore, the concentrations of the phosphoric acid, the NH3 and the MgCl2 are all 0.5-1.5 mg / L.

[0012] Furthermore, the temperature of the catalytic hydrolysis is 35°C.

[0013] Furthermore, the catalytic hydrolysis time is 8 hours.

[0014] The present invention also provides application of the above-mentioned cementing filler in cementing and filling operations in mining.

[0015] The present invention also provides a cementing and filling method, comprising the steps of sequentially injecting phytic acid enzymatic hydrolyzate, ammonia water and MgCl2 solution into aggregate pores for cementing and curing;

[0016] The phytic acid enzymatic hydrolyzate is obtained by catalyzing and hydrolyzing phytic acid with phytase.

[0017] Furthermore, the particle size of the aggregate is 100-200 meshes.

[0018] Furthermore, the mass ratio of phosphoric acid in the phytate hydrolyzate, NH3 in the ammonia water and MgCl2 in the MgCl2 solution is 1:1:1.

[0019] The present invention discloses the following technical effects:

[0020] The present invention develops a new cementitious filling method, which uses phytase to catalyze the hydrolysis of organic phosphorus substrates, quickly releases inorganic phosphate ions, and generates magnesium ammonium phosphate (MgNH4PO4·6H2O) precipitation with ammonium ions and magnesium chloride under alkaline conditions. In this process, the formation of magnesium ammonium phosphate requires a weak alkaline environment. Therefore, an appropriate amount of ammonia water is used to maintain the weak alkaline environment, and ammonium ions can also be provided to generate magnesium ammonium phosphate. Compared with traditional cement-based cementitious filling materials, the cementitious filling materials formed by this method avoid high energy consumption, high emissions and high alkaline environments, and meet low-carbon and environmental protection requirements; at the same time, compared with MICP and EICP technologies, it avoids problems such as biosafety and poor stability of cementitious filling materials, and meets mine filling requirements. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0023] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0024] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0025] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0026] The strength of carbonate precipitation cemented filling materials is low (generally less than 2MPa), which is difficult to meet the filling requirements. At the same time, the process also produces harmful byproducts NH4 + and NH3. There is sufficient evidence to show that the stability of heavy metal phosphate minerals under acidic conditions is better than that of carbonate minerals, and the risk of heavy metal dissolution is lower. Therefore, using heavy metal phosphate minerals as a binder for filling materials has certain feasibility and safety. Based on this, the present invention proposes a phytase-induced phosphate precipitation (Phytase Induces Ihosphate Irecipitation, PIPP) cementing filling technology. This technology uses phytase to catalyze the hydrolysis of organic phosphorus substrates, quickly release inorganic phosphate ions, and generate magnesium ammonium phosphate (MgNH4PO4·6H2O) precipitates with ammonium ions and magnesium chloride under alkaline conditions. In this process, the formation of magnesium ammonium phosphate requires a weak alkaline environment. Therefore, an appropriate amount of ammonia water is used to maintain a weak alkaline environment. At the same time, ammonium ions can also be provided to generate magnesium ammonium phosphate.

[0027] Phytic acid (also known as inositol hexaphosphate), molecular formula C6H 18 O 24 P6 is an organophosphorus compound extracted from plant seeds. Phytases (phytases) can catalyze the removal of phosphate groups from phytate. The phytase used in the following examples is 3-phytase, and 6-phytase, orthophosphate monoacyl hydrolase or other phytases that can hydrolyze phosphate groups can also be used.

[0028] Example 1 Enzymatic Phosphate (Pi) Release Experiment

[0029] The determination of Pi release is to study the efficiency of phytase-induced Pi release, which is an important part of the PIPP process. The concentrations of phytic acid and phytase and the hydrolysis temperature and hydrolysis time are important influencing factors. 100 mL of phytase solutions of different concentrations (phytase concentrations are 0.5, 1.0, and 1.5 mg / L) were added to 100 mL of phytic acid solutions of different concentrations (phytic acid volume fractions are 0.2%, 0.4%, and 0.6%), respectively, and catalytic hydrolysis was performed at different temperatures (25, 30, and 35°C). After 2, 4, 8, 12, 20, 28, 36, and 48 hours, 1 mL of the reaction solution was taken to determine the free phosphate content of each group. All experimental groups were repeated 3 times, and significant data of P≤0.05 were obtained.

[0030] The experimental results showed that the optimal experimental conditions were: 100 mL of 0.5 mg / L phytase solution was added to 100 mL of 0.2% phytic acid solution and catalytic hydrolysis was performed at 35°C. Under the optimal experimental conditions, the free phosphate content could reach 0.42 mg / L after catalytic hydrolysis for 8 hours.

[0031] Under the above optimal experimental conditions, the free phosphate content of each group was measured after 2, 4, 8, 12, 20, 28, 36 and 48 hours. The results are shown in Table 1.

[0032] Table 1 Detection results of free phosphate content at different times under optimal experimental conditions

[0033] Hydrolysis time (h) 2 4 8 12 20 28 36 48 Phosphoric acid content (mg / L) 0.14 0.32 0.42 0.44 0.45 0.46 0.47 0.47

[0034] Example 2 Induced phosphate precipitation experiment

[0035] The enzymatic hydrolysate used in this experiment was obtained by hydrolyzing for 8 h under the optimal conditions of the enzymatic Pi release experiment in Example 1. After concentration, the phosphoric acid content was adjusted to 0.5 mg / L, 1.0 mg / L and 1.5 mg / L, respectively.

[0036] The phosphate precipitation was determined to investigate the efficiency of phytase-induced magnesium ammonium phosphate precipitation, which is the key to biomineralization cementation. 3- NH4 + Mg 2+ Concentration, dosage ratio and mineralization time are important influencing factors.

[0037] Experiment 1: Add 100 mL of 0.5 mg / L ammonia water and 100 mL of 0.5 mg / L MgCl2 solution into 100 mL of 0.5 mg / L enzymatic hydrolyzate, and carry out mineralization reaction at 35°C to generate magnesium ammonium phosphate precipitate.

[0038] Experiment 2: 100 mL of 1.0 mg / L ammonia water and 100 mL of 1.0 mg / L MgCl2 solution were added to 100 mL of 1.0 mg / L enzymatic hydrolyzate, and the mineralization reaction was carried out at 35°C to generate magnesium ammonium phosphate precipitate.

[0039] Experiment 3: 100 mL of 1.5 mg / L ammonia water and 100 mL of 1.5 mg / L MgCl2 solution were added to 100 mL of 1.5 mg / L enzymatic hydrolyzate, and the mineralization reaction was carried out at 35°C to generate magnesium ammonium phosphate precipitate.

[0040] The amount of magnesium ammonium phosphate precipitate generated in each experimental group was measured after 2, 4, 8, 12, 20, 28, 36 and 48 hours. All experimental groups were repeated 3 times, and significant data with P ≤ 0.05 were obtained.

[0041] The method for measuring the amount of magnesium ammonium phosphate generated is as follows: most of the magnesium ammonium phosphate precipitate generated in the above reaction process will sink to the bottom of the test tube, and a small part will adhere to the inner wall of the test tube. After the reaction is completed, use quantitative filter paper to filter the solution and precipitate in the test tube, rinse the test tube twice with distilled water and filter, then mark the filter paper and test tube accordingly and put them into a constant temperature oven for drying. After drying, weigh the total mass and record it as W1, then rinse the inner wall of the test tube and the filter paper with dilute hydrochloric acid until the precipitate disappears, rinse twice with distilled water, put the corresponding marked filter paper and test tube back into the constant temperature oven for drying, weigh the total mass after drying and record it as W2, W=W1-W2 is the mass of magnesium ammonium phosphate precipitate generated in the test tube.

[0042] The test results of the amount of magnesium ammonium phosphate precipitate generated at different mineralization times are shown in Table 2. The results show that when 100 mL of 0.5 mg / L ammonia water and 100 mL of 0.5 mg / L MgCl2 solution are added to 100 mL of 0.5 mg / L enzymatic hydrolyzate and mineralized at 35°C for 8 hours, the amount of magnesium ammonium phosphate precipitate generated can reach 5.29 g.

[0043] Table 2 Detection results of the amount of magnesium ammonium phosphate precipitation at different mineralization times

[0044]

[0045] Example 3 Preparation experiment of cementitious filling material

[0046] The enzymatic hydrolysate used in this experiment was the enzymatic hydrolysate obtained by hydrolysis for 8 h under the optimal conditions of the enzymatic Pi release experiment in Example 1. After concentration treatment, the phosphoric acid content was adjusted to 1.5 mg / L.

[0047] The cementing filling material was prepared by the infusion method, and its strength was measured. Coal gangue aggregate with a particle size of 100-200 mesh was loaded into a 50mm×100mm mold. Two layers of gauze were used as filter sheets at both ends of the mold. Grouting ports and slurry outlets were set. Enzyme hydrolysate (1.5mg / L), 1.5mg / L ammonia water and 1.5mg / L MgCl2 solution were poured into the mold from the grouting ports in sequence through a peristaltic pump. The volume ratio of enzymatic hydrolysate, ammonia water and MgCl2 solution was 1:1:1. In order to ensure uniform distribution of consolidated magnesium ammonium phosphate, the positions of the slurry inlet and slurry outlet were interchanged after each batch of infusion was completed. Then the next batch of infusion was carried out. After the infusion was completed, it was cured at 35℃ for a period of time (2, 3, 4, 5, 6, 7, 14 and 28d), and the mold was removed and dried to obtain standard specimens. The unconfined compressive strength of the materials in each experimental group was measured respectively. All experimental groups were repeated 3 times, and significant data with P ≤ 0.05 were obtained.

[0048] The unconfined compressive strength is tested using a pressure testing machine. The operating steps are as follows: demould and dry the standard cementitious filling material specimen, grind the surfaces at both ends to form a specimen with a diameter and height of 5 cm and 10 cm respectively, place it on a computer-controlled universal testing machine, and perform an unconfined compressive strength test. The loading speed is 2 mm / min, record the maximum pressure value F when the specimen is destroyed, and calculate the unconfined compressive strength of the specimen.

[0049] The unconfined compressive strength test results of different curing times are shown in Table 3. The results show that after the pouring is completed and cured at 35℃ for 7 days, the unconfined compressive strength of the standard sample reaches 2.71MPa.

[0050] Table 3 Unconfined compressive strength test results of Example 3 at different curing times

[0051] Curing time (d) 2 3 4 5 6 7 14 28 Unconfined compressive strength (MPa) 1.05 1.21 1.84 2.10 2.32 2.71 2.74 2.75

[0052] Comparative Example 1

[0053] The coal gangue aggregate with a particle size of 100-200 mesh was loaded into a 50mm×100mm mold. Two layers of gauze were used as filters at both ends of the mold. Grouting ports and slurry outlets were set. Urease solution (1.5mg / L), 1.5mg / L urea and 1.5mg / L MgCl2 solution were poured into the mold from the grouting ports in a volume ratio of 1:1:1 by a peristaltic pump. In order to ensure the uniform distribution of consolidated calcium carbonate precipitation, the positions of the slurry inlet and slurry outlet were swapped after each batch of pouring. The next batch of pouring was then carried out. After the pouring was completed, it was cured at 35℃ for a period of time (2, 3, 4, 5, 6, 7, 14 and 28d), and the mold was removed and dried to obtain standard specimens. The unconfined compressive strength of the materials in each experimental group was measured respectively. The results are shown in Table 4. All experimental groups were repeated 3 times, and significant data of P≤0.05 were obtained. The results show that the strength did not reach 2MPa using EICP technology.

[0054] Table 4 Unconfined compressive strength test results of comparative example 1 at different curing times

[0055] Curing time (d) 2 3 4 5 6 7 14 28 Unconfined compressive strength (MPa) 0.45 0.55 0.70 0.82 0.90 0.98 1.00 1.05

[0056] Comparative Example 2

[0057] Same as Example 3, the only difference is that the enzymatic hydrolysate of Example 3 is replaced by a phosphoric acid aqueous solution with a concentration of 1.5 mg / L. The unconfined compressive strength test results of different curing times are shown in Table 5. The results show that the unconfined compressive strength is reduced when the phosphoric acid aqueous solution is used for cementation and curing relative to the enzymatic hydrolysate of Example 3. The present invention speculates that the phosphoinositide produced by enzymatic hydrolysis may play an unknown role, and further expansion research on this role can be carried out in the later stage.

[0058] Table 5 Unconfined compressive strength test results of comparative example 2 at different curing times

[0059] Curing time (d) 2 3 4 5 6 7 14 28 Unconfined compressive strength (MPa) 0.85 1.00 1.24 1.43 1.56 1.86 1.92 1.95

[0060] Example 4 Stability test of cementitious filling material

[0061] The stability test determines the amount of heavy metal dissolution from cementitious filling materials, and is to study the ability of cementitious filling materials to fix heavy metal ions in coal gangue aggregates under acidic conditions.

[0062] The solidified cementitious filling material specimens (obtained after curing for 7 days in Example 3) were leached under different pH solution conditions. 2+The content of Pb was 0.75 mg / L. The different pH solutions were adjusted with 0.1 mol / L HCl and NaOH. Before the specimen was demoulded, 500 mL of solutions with pH values ​​of 4.00, 5.00 and 6.00 were injected from the top of the mold at a flow rate of 3 mL / min. In addition, the direct leaching of coal gangue aggregate was used as a control to determine the heavy metal ion Pb in the leaching solution. 2+ The results are shown in Table 6. The results show that the heavy metal ion Pb can be released by the cementation and curing method of the present invention. 2+ The leaching concentration dropped from 0.75 mg / L to below 0.05 mg / L.

[0063] Table 6 Heavy metal ion Pb at different pH 2+ The release amount

[0064]

[0065] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cementing filler, characterized in that: It includes phytic acid enzymatic hydrolysate, ammonia water and MgCl2 solution; The phytic acid enzymatic hydrolysate is obtained by catalyzing and hydrolyzing phytic acid using phytase; The phytase is 3-phytase, 6-phytase or orthophosphate monoester hydrolase; The mass ratio of phosphoric acid in the phytic acid hydrolyzate, NH3 in the ammonia water and MgCl2 in the MgCl2 solution is 1:1:1; The concentrations of the phosphoric acid, the NH 3 and the MgCl 2 are all 0.5-1.5 mg / L.

2. The cementing filler according to claim 1, characterized in that: The temperature of the catalytic hydrolysis is 35°C.

3. The cementing filler according to claim 1, characterized in that: The catalytic hydrolysis time is 8 hours.

4. Use of the cementing filling agent as described in any one of claims 1 to 3 in cementing filling operations in mining.

5. A method for cementing and filling using the cementing filler according to any one of claims 1 to 3, characterized in that: The method comprises the steps of sequentially injecting phytic acid enzymatic hydrolyzate, ammonia water and MgCl2 solution into aggregate pores for cementation and curing.

6. The cementing filling method according to claim 5, characterized in that: The particle size of the aggregate is 100-200 meshes.

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