阅读说明：本技术 一种污泥基生物碳-锰渣复合催化剂及其制备方法和应用 (Sludge-based biological carbon-manganese slag composite catalyst and preparation method and application thereof ) 是由 贺治国 李梦珂 钟慧 胡亮 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种污泥基生物碳-锰渣复合催化剂及其制备方法和应用。污泥基生物碳-锰渣复合催化剂的制备过程为：在碱性溶液中,先加入污泥和电解锰渣进行改性反应I,再加入酸性溶液进行改性反应II,改性反应II完成后,进行固液分离,所得固体产物在无氧条件下进行热解,即得。所得复合催化剂具有较好的导电性和较强的吸附能力以及较高的催化活性,能快速、高效活化双氧水或过硫酸盐等产生自由基以降解水体或土壤中的有机污染物,且该复合催化剂的制备以固体废弃物为原料,成本低,制备过程简单,具有较好生产和应用前景。(The invention discloses a sludge-based biochar-manganese slag composite catalyst and a preparation method and application thereof. The preparation process of the sludge-based biochar-manganese slag composite catalyst comprises the following steps: adding sludge and electrolytic manganese slag into an alkaline solution to perform a modification reaction I, adding an acidic solution to perform a modification reaction II, performing solid-liquid separation after the modification reaction II is finished, and pyrolyzing the obtained solid product under an oxygen-free condition to obtain the manganese-rich organic carbon nano tube. The obtained composite catalyst has good electrical conductivity, strong adsorption capacity and high catalytic activity, can quickly and efficiently activate hydrogen peroxide or persulfate and the like to generate free radicals to degrade organic pollutants in water or soil, and the preparation of the composite catalyst takes solid wastes as raw materials, has low cost and simple preparation process, and has good production and application prospects.)

1. A preparation method of a sludge-based biological carbon-manganese slag composite catalyst is characterized by comprising the following steps: adding sludge and electrolytic manganese slag into an alkaline solution to perform a modification reaction I, adding an acidic solution to perform a modification reaction II, performing solid-liquid separation after the modification reaction II is finished, and pyrolyzing the obtained solid under an oxygen-free condition to obtain the manganese-containing organic silicon dioxide composite material.

2. The preparation method of the sludge-based biochar-manganese slag composite catalyst according to claim 1 is characterized by comprising the following steps: the concentration of the alkaline solution is 0.4-0.6M; the alkaline solution is at least one of a sodium carbonate solution, a potassium carbonate solution, a sodium hydroxide solution and a potassium hydroxide solution.

3. The preparation method of the sludge-based biochar-manganese slag composite catalyst according to claim 1 is characterized by comprising the following steps: the weight percentage of the sludge and the electrolytic manganese slag is 60-80 percent and 40-20 percent.

4. The preparation method of the sludge-based biochar-manganese slag composite catalyst according to claim 1 is characterized by comprising the following steps: the conditions of the modification reaction I are as follows: the temperature is room temperature, and the time is 20-40 min.

5. The preparation method of the sludge-based biochar-manganese slag composite catalyst according to claim 1 is characterized by comprising the following steps: the adding amount of the acid solution is controlled to control the acid concentration in the reaction system to be 0.2-0.4M; the acid solution is at least one of sulfuric acid solution, hydrochloric acid solution and nitric acid solution.

6. The preparation method of the sludge-based biochar-manganese slag composite catalyst according to claim 1 is characterized by comprising the following steps: the conditions of the modification reaction II are as follows: the temperature is room temperature, and the time is 10-20 min.

7. The preparation method of the sludge-based biochar-manganese slag composite catalyst according to claim 1 is characterized by comprising the following steps: the pyrolysis conditions are as follows: the temperature is 600-800 ℃, and the time is 90-120 min.

8. A sludge-based biological carbon-manganese slag composite catalyst is characterized in that: the preparation method of any one of claims 1 to 7.

9. The application of the sludge-based biochar-manganese slag composite catalyst as recited in claim 8, wherein: the catalyst is used for catalytically activating hydrogen peroxide and/or persulfate to oxidize and degrade organic pollutants in water or soil.

10. The application of the sludge-based biological carbon-manganese slag composite catalyst according to claim 6 is characterized in that:

the organic pollutants comprise at least one of antibiotics, dyes, flotation agents, herbicides and polychlorinated biphenyl; the pH range of the water body or the soil is 3-11.

Technical Field

The invention relates to a catalytic material, in particular to a sludge-based biochar-manganese slag composite catalyst, a method for preparing the sludge-based biochar-manganese slag composite catalyst by activating, modifying and calcining sludge and electrolytic manganese slag, and application of the sludge-based biochar-manganese slag composite catalyst in catalyzing and activating hydrogen peroxide and/or persulfate to oxidize and degrade organic pollutants in water or soil, and belongs to the technical field of solid waste resource utilization.

Background

The Advanced Oxidation Processes (AOPs) can generate high Reactive Oxygen Species (ROS), can efficiently and quickly remove the organic pollution difficult to degrade, and has the advantages of simple operation and high stability. At present, researches show that low-cost, high-efficiency and environment-friendly catalysts of carbon-based or metal-based AOPs (argon oxygen decarburization) can be obtained by using activated sludge, agricultural solid wastes (straws, sawdust and the like), metallurgical slag or mineral-based materials, and although the low-cost catalysts can effectively remove pollutants, the low-cost catalysts still have the defects of difficult avoidance of the inhibition effect generated by heavy metal ions and interference ion influence when the low-cost catalysts are used for treating actual organic pollution, and the requirements on pH are strict.

At present, some documents report that the removal capacity of pollutants can be remarkably improved by using a metal/carbon composite material, for example, a biochar/nano-alumina composite material can be used for efficiently removing methylene blue in a water body (Chemical Engineering Journal,226(2013)286 plus 292). Research has been conducted on a biochar-supported red mud catalyst (Journal of Hazardous Materials 408 (2021)) 124802 prepared by a simple mixing method by using red mud and coconut shell as raw Materials, wherein the catalyst can effectively degrade acid orange and malachite green, but Fe in the composite material prepared by the method⁰Only distributed on the surface of the biochar and easy to generate Fe⁰Oxidation under natural conditions and iron leaching during application.

Disclosure of Invention

Aiming at the problems in the prior art, the first purpose of the invention is to provide a sludge-based biochar-manganese slag composite catalyst, which has a high catalytic activity effect on the decomposition of hydrogen peroxide or persulfate and can promote the efficient oxidative degradation of organic pollutants by hydrogen peroxide or persulfate.

The second purpose of the invention is to provide a preparation method of the sludge-based biochar-manganese slag composite catalyst, which takes sludge and electrolytic manganese slag as raw materials, has low cost and simple preparation process and is beneficial to large-scale production.

The third purpose of the invention is to provide an application of the sludge-based biochar-manganese slag composite catalyst, the sludge-based biochar-manganese slag composite catalyst is applied to catalyzing hydrogen peroxide or persulfate to carry out oxidative degradation on organic polluted wastewater containing antibiotics, dyes or flotation reagents or organic polluted soil containing herbicides and pesticides, the rapid and efficient degradation of organic pollutants which are difficult to degrade in the wastewater or the soil can be realized, the composite catalyst has a wide pH range, shows high catalytic activity at room temperature, and is beneficial to large-scale popularization and application.

In order to realize the technical purpose, the invention provides a preparation method of a sludge-based biochar-manganese slag composite catalyst, which comprises the steps of firstly adding sludge and electrolytic manganese slag into an alkaline solution to carry out a modification reaction I, then adding an acidic solution to carry out a modification reaction II, carrying out solid-liquid separation after the modification reaction II is finished, and carrying out pyrolysis on the obtained solid under an oxygen-free condition to obtain the catalyst.

The technical scheme of the invention takes sludge and electrolytic manganese slag as raw materials, the sludge contains abundant biomass and mainly provides a carbon source and a nitrogen source, and the raw material of the electrolytic manganese slag contains transition metal elements such as iron, manganese and the like. But most of useful components in the sludge and the electrolytic manganese slag are embedded and are difficult to be effectively utilized, the technical scheme of the invention firstly utilizes alkaline solution to treat the sludge and the electrolytic manganese slag, silicate minerals and aluminate minerals in raw materials can be partially dissolved under alkaline conditions, the porosity of the raw materials is greatly improved, more active sites can be exposed, on the basis, acid solution is further adopted for treatment, oxides such as calcium, magnesium, potassium and the like coated on the surfaces of the useful metal minerals can be removed by utilizing the acid solution, so that more metal elements with catalytic activity are exposed, the activity of the metal oxides can be improved, the modified raw materials are subjected to high-temperature pyrolysis treatment, organic matters are fully converted into carbon matrixes, in the high-temperature pyrolysis process, the iron elements can be aggregated and coated by generated carbon in the form of iron particles, the manganese element and the nitrogen element are uniformly distributed on the surface of the carbon substrate. The transition metal such as iron and manganese is embedded on the carbon matrix, so that diffused carbon atoms are favorably transferred to a two-dimensional plane of the graphite phase, the graphite phase of the carbon matrix is improved, and the transition metal has excellent electron donating capability and can improve the conductivity of the biochar. In addition, graphite nitrogen, which has a high electronegativity, can attract electrons from neighboring carbon atoms to form positively charged carbon, and these activated carbon atoms can interact with an oxidizing agent to further form highly active complexes on the surface. Therefore, the sludge-based biochar-manganese slag composite catalyst prepared by the invention has higher catalytic activity on oxidative degradation of organic pollutants by hydrogen peroxide or persulfate.

As a preferable scheme, the concentration of the alkaline solution is 0.4-0.6M; the alkaline solution can adopt conventional inorganic base in the prior art, and specifically can be at least one of sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution and potassium hydroxide solution. The alkali solution is controlled within a proper concentration, so that a part of aluminosilicate minerals can be properly dissolved to play a role in improving porosity, and excessive concentration can cause excessive dissolution of aluminosilicate.

As a preferable scheme, the weight percentage of the sludge and the electrolytic manganese slag is 60-80% and 40-20%. If the proportion of the manganese slag is too high, the adsorption capacity of the composite material is reduced, and the degradation capacity of the composite material is further reduced, and if the proportion of the manganese slag is too low, the content of the transition metal element is insufficient, and the synergistic effect is difficult to achieve.

As a preferred embodiment, the modification reaction I is performed under the following conditions: the temperature is room temperature, and the time is 20-40 min. If the modification reaction time is too short, it is difficult to increase the porosity, and if the modification reaction time progresses, excessive dissolution of the aluminosilicate mineral is caused.

As a preferable scheme, the adding amount of the acidic solution is controlled to control the acid concentration in the reaction system to be 0.2-0.4M; the acid solution may be inorganic acid which is conventional in the prior art, and specifically may be at least one of a sulfuric acid solution, a hydrochloric acid solution, and a nitric acid solution. If the concentration of the acidic solution is too low, impurities are difficult to be effectively removed, the active material is difficult to be sufficiently exposed, and if the concentration of the acidic solution is too high, dissolution loss of the active material is caused.

As a preferred embodiment, the conditions of the modification reaction II are: the temperature is room temperature, and the time is 10-20 min. If the reaction time is too long, the leaching of iron and manganese in the electrolytic manganese slag is serious, and if the reaction time is insufficient, impurity components coated on the surfaces of sludge and manganese slag particles cannot be removed.

As a preferred embodiment, the pyrolysis conditions are: the temperature is 600-800 ℃, and the time is 90-120 min. If the temperature is too low, Fe cannot be generated⁰The carbon substrate can not be graphitized effectively, the temperature is too high, the heat energy consumption is large, and the cost is high; if the reaction time is too short, the iron element can not be agglomerated to generate zero-valent iron particles, and if the reaction time is too long, the heat energy is increased, and the cost is increased. The further preferable pyrolysis temperature is 700-800 ℃.

The sludge and the electrolytic manganese slag are pretreated firstly as follows: cleaning and drying with water, and sieving with a 150-200 mesh sieve.

The invention also provides a sludge-based biochar-manganese slag composite catalyst which is obtained by the preparation method.

The invention also provides application of the sludge-based biochar-manganese slag composite catalyst, which is used for catalytically activating hydrogen peroxide and/or persulfate to oxidize and degrade organic pollutants in water or soil.

The hydrogen peroxide related by the invention is common commercial industrial hydrogen peroxide, and the mass percentage concentration is 30%. The persulfate is selected from potassium monopersulfate and/or potassium peroxodisulfate.

As a preferred embodiment, the organic contaminant includes at least one of an antibiotic, an organic dye, a flotation agent, a herbicide, polychlorinated biphenyl. Generally, organic pollutants in water include antibiotics, dyes, beneficiation flotation agents, and the like. The organic pollutants for the soil comprise herbicides, polychlorinated biphenyl and the like. More specifically, antibiotics are specifically described as norfloxacin, bisphenol a, roxarsone, and the like. The organic dye is selected from malachite green, acid orange, etc. The flotation agent is specifically selected from second oil, benzohydroxamic acid, etc., the herbicide mainly refers to atrazine, and the polychlorinated biphenyl is specifically selected from dichlorobiphenyl, trichlorobiphenyl, etc.

As a preferable scheme, the pH environment of the water body or the soil is 3-11. The modified electrolytic manganese dioxide waste residue catalyst has better catalytic activity in a wide pH range, and solves the problem that H needs to be activated under an acidic condition₂O₂Such as the soil containing the beneficiation reagent is usually alkaline, and the H can be directly activated under alkaline conditions by using the catalyst without adjusting the pH₂O₂。

As a preferable scheme, the addition concentration of the sludge-based biochar-manganese slag composite catalyst in the organic wastewater is 0.4-0.8 g/L, and the concentration in the organic polluted soil is 20-30 g/kg; the addition concentration of the hydrogen peroxide and/or the persulfate in the organic wastewater is 0.2-0.6 g/L, and the addition concentration in the organic polluted soil is 1.5-4.0 g/kg. The specific addition amount of the sludge-based biological carbon-manganese residue composite catalyst is properly adjusted according to the content of organic pollutants in soil or water.

As a preferred scheme, the organic wastewater contains one or more of antibiotics, organic dyes and flotation reagents; the soil organic contaminant comprises a herbicide or polychlorinated biphenyl. Generally, the concentration of the antibiotic is 10-40 mg/L, the concentration of the dye is 80-100 mg/L, the concentration of COD in the mineral processing wastewater is 180-270 mg/L, the concentration of the herbicide is 5-10 mg/L, and the concentration of the polychlorinated biphenyl is 10-20 mg/kg. For the organic wastewater within the concentration range, a sludge-based biological carbon-manganese residue composite catalyst is adopted, wherein the addition concentration of the sludge-based biological carbon-manganese residue composite catalyst in the organic wastewater is 0.4-0.8 g/L, and the concentration of the sludge-based biological carbon-manganese residue composite catalyst in the organic polluted soil is 20-30 g/kg; the adding concentration of hydrogen peroxide and/or persulfate in the organic wastewater is 0.2-0.6 g/L, and the adding concentration in the organic polluted soil is 1.5-4.0 g/kg; within 60-90 min, the removal rate of antibiotics is 80-90%, the removal rate of dyes is 90-95%, the removal rate of COD (chemical oxygen demand) of beneficiation wastewater reaches 55-85%, within 200-400 min, the removal rate of herbicides is 85-90%, and the removal rate of polychlorinated biphenyl is 80-88%.

The invention provides a preparation method of a sludge-based biochar-manganese slag composite catalyst, which comprises the following steps:

step 1) washing sludge and electrolytic manganese residues with water for 1-2 times respectively, drying for 4-6 h at 40-55 ℃, sieving the dried waste residues with a 150-200-mesh sieve, and collecting the sludge and the manganese residues under the sieve for later use;

step 2) adding the undersize sludge and manganese slag obtained in the step 1) into 0.4-0.6M potassium carbonate solution, sodium hydroxide solution or potassium hydroxide solution according to the mass percent of 60-80% and 40-20%, and reacting for 20-40 min; adding a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution into the solution, controlling the acid concentration in the solution system to be 0.2-0.4M, and continuing to react for 10-20 min;

and 3) carrying out suction filtration on the solution obtained after the reaction in the step 2), wherein the obtained filter residue is the precursor of the metal-carbon catalyst.

Step 4) pyrolyzing the precursor obtained in the step 3) in a nitrogen or argon atmosphere at the pyrolysis temperature of 600-800 ℃ for 90-120 min;

the process of using the sludge-based biological carbon-manganese residue composite catalyst to remove the flotation reagent in the beneficiation wastewater comprises the following steps: the sludge-based biological carbon-manganese slag composite catalyst is added into the wastewater according to the proportion of 0.6-1.2 g/L, meanwhile, the adding amount of the oxidant is 0.2-0.8 g/L, the pH value of the wastewater is 3-11, and the reaction is carried out at room temperature. The content of antibiotics in the wastewater is 10-40 mg/L, the concentration of dye is 80-100 mg/L, and the concentration of COD in the mineral processing wastewater is 180-270 mg/L; the concentration of the sludge-based biochar-manganese residue composite catalyst in the organic polluted soil is 20-30 g/kg, the adding concentration of the oxidant is 1.5-4.0 g/kg, the concentration of the herbicide in the soil is 5-10 mg/L, and the concentration of the polychlorinated biphenyl is 10-20 mg/kg. The degradation reaction time is 60-120 min, the removal rate of antibiotics is 80-90%, the removal rate of dye is 90-95%, the removal rate of COD in the mineral processing wastewater is 55-85%, the removal rate of herbicide is 85-90% within 200-400 min, and the removal rate of polychlorinated biphenyl is 80-88%.

Compared with the prior art, the invention has the following advantages:

1) the preparation method of the sludge-based biochar-manganese slag composite catalyst provided by the invention uses sludge and manganese slag as main raw materials, is cheap and easy to obtain, realizes resource utilization of two solid wastes, is simple and convenient in preparation process and controllable in reaction conditions, can be obtained by one-pot modification at room temperature and then high-temperature pyrolysis, and is beneficial to industrial production.

2) The sludge-based biochar-manganese slag composite catalyst has high catalytic activity, can be used as a high-grade oxidation catalyst for catalytically activating oxidants such as hydrogen peroxide, persulfate and the like to efficiently and rapidly oxidize and degrade refractory organic pollutants, and has good application prospect.

3) The sludge-based biochar-manganese slag composite catalyst can be used for catalyzing decomposition of hydrogen peroxide or persulfate and the like to efficiently and quickly oxidize and degrade organic matters in wastewater (containing antibiotics, dyes and flotation reagents) and soil (containing herbicides or polychlorinated biphenyl), and shows high catalytic activity to the hydrogen peroxide within a wide pH range (3.0-11).

Drawings

Fig. 1 is a SEM comparison of sludge-based biocarbon-manganese slag composite catalysts prepared at different pyrolysis temperatures, with the pores gradually becoming larger and uniform as the temperature increases (600, 700, 800 ℃ in sequence from left to right).

FIG. 2 is HRTEM and mapping images of the mud-based biochar-manganese slag composite catalyst prepared at the pyrolysis temperature of 800 ℃; it can be seen that iron particles are encapsulated within the carbon matrix (a, b, c, f), while manganese (g), nitrogen (e) are uniformly distributed on the carbon.

FIG. 3 is a comparative XRD plot of sludge and electrolytic manganese residues and a sludge-based biochar-manganese residue composite catalyst; the sludge is mainly formed by quartz, nacrite and muscovite phases, and the manganese slag is mainly formed by quartz and gypsum; after the sludge and the manganese slag are compounded, the gypsum phase disappears and obvious Fe appears⁰And of graphitic carbonA peak; at too low a temperature (400 ℃ C.) without Fe⁰And a peak of graphitic carbon appears.

FIG. 4 is a graph comparing the degradation efficiency of the sludge-based biocarbon-manganese slag composite catalyst prepared in example 1 at different pyrolysis temperatures in combination with a peroxydisulfate system for hydroxamic acid; the result shows that the composite catalyst shows excellent removal effect on the p-hydroximic acid, and the catalytic activity of the sludge biochar and the manganese slag which are not compounded is low, which shows that the sludge and the manganese slag are compounded to have synergistic effect.

FIG. 5 is a comparison graph of the removal of several typical organic pollutants by the sludge-based biochar-manganese slag composite catalyst prepared by pyrolysis at 800 ℃ in combination with a peroxymonosulfate system in example 1, and the results show that the catalyst can effectively remove antibiotics, dyes and organic matters of beneficiation wastewater.

FIG. 6 is a graph comparing the degradation of hydroxamic acid in the sludge-based biochar-manganese slag composite catalyst prepared in example 4 in combination with a hydrogen peroxide system at different pH values; the degradation efficiency decreased with increasing pH, and the removal rate of the simulated benzohydroxamic acid was still 71.6% at pH 11.

FIG. 7 is a graph showing the effect of the sludge-based biochar-manganese slag composite catalyst prepared in example 5 in degrading organic matters in polychlorinated biphenyl-contaminated soil in combination with a hydrogen peroxide solution system; the result shows that the degradation system can effectively remove the polychlorinated biphenyl in the soil.

Detailed Description

The following examples are intended to illustrate the invention in further detail without limiting the scope of the invention as claimed.

Example 1

Preparing a sludge-based biochar-manganese slag composite catalyst: respectively washing sludge (fresh wet sludge from a Changsha city Mingshan-alkan sewage treatment plant) and electrolytic manganese slag (from Huntan electrochemical technology Co., Ltd.) with water for 1 time, drying at 50 deg.C for 4h, sieving the dried sludge and manganese slag with 150 mesh sieve, and collecting undersize particles. Weighing 4g of sludge and 1.5g of manganese slag respectively, placing the sludge and the manganese slag in 100mL of 0.5M potassium carbonate solution, reacting for 30min, adding nitric acid to enable the concentration of the nitric acid to be 0.4M in a reaction system, continuing to react for 10min, performing suction filtration by using a 0.45-micrometer water-based filter membrane, respectively cleaning filter residues by using ethanol and deionized water, drying, respectively pyrolyzing the obtained precursors at 600, 700 and 800 ℃ for 2h in a nitrogen protection atmosphere respectively, and obtaining composite materials, namely composite catalyst-600, composite catalyst-700 and composite catalyst-800 respectively. In addition, the sludge without combination and the electrolytic manganese slag (the sludge under the screen and the manganese slag) are pyrolyzed at 800 ℃ to prepare sludge biochar-800 and manganese slag-800 which are used for comparison experiments.

Adding 50mg of each of the three composite catalysts into 50mL of 20mg/L benzohydroxamic acid simulated organic wastewater (pH is 6.04), stirring for 60min to reach adsorption-desorption equilibrium, adding 2mL of 10g/L potassium peroxodisulfate, and continuing stirring at room temperature for 60 min. Under the same experimental conditions and parameters, the composite catalyst is changed into biochar-800 and manganese slag-800 for experiment. After the degradation reaction was completed, the degradation rates of the benzalhydroxamic acid in the water samples of the composite catalyst-600, the composite catalyst-700 and the composite catalyst-800 reaction systems were measured to be 78.4%, 83.7% and 89.9%, while the degradation rates of the benzalhydroxamic acid in the water samples of the biochar-800 and manganese slag-800 reaction systems were measured to be 60.5% and 33.4%, respectively, as shown in fig. 4.

Example 2

Selecting the composite catalyst-800 prepared in example 1 as a catalyst, adding 50mg of the composite catalyst-800 into 100mL of simulated mineral processing wastewater respectively containing 20mg/L of norfloxacin, bisphenol a and roxarsone, 100mg/L of simulated dye wastewater of malachite green and acid orange, and 50mg/L of simulated mineral processing wastewater of oil II and butylamine black, after 60min of adsorption time, 2mL of potassium monopersulfate with the concentration of 10g/L is counted, after reaction is continued for 60min, the degradation rates of the catalytic system on norfloxacin (pH 8.04), bisphenol a (pH 7.65), roxarsone (pH 4.51), malachite green (pH 2.87), acid orange (pH 2.56) are respectively measured to be 82.4%, 90.2%, 93.2%, 94.6% and 95.3%, the degradation rates on oil II (pH 5.38), the simulated mineral processing wastewater with the pH 15.79% of black and the removal rate on butylamine black (COD is respectively 74.79%, see fig. 5.

Example 3

Preparing a sludge-based biochar-manganese slag composite catalyst: washing sludge and electrolytic manganese slag with water for 1 time respectively, drying at 50 ℃ for 5 hours, sieving the dried sludge and manganese slag with a 200-mesh sieve, collecting undersize particles, and preparing different composite catalysts respectively. Catalyst 1: weighing 4g of sludge and 1.2g of manganese slag, placing the sludge and the manganese slag in 100mL of 0.45M potassium carbonate solution, reacting for 35min, performing suction filtration by using a 0.45-micron water-based filter membrane, respectively cleaning filter residues by using ethanol and deionized water, and drying to obtain a precursor 1; catalyst 2: weighing 4g of sludge and 1.2g of manganese slag, placing the sludge and the manganese slag into 100mL of nitric acid solution with the concentration of 0.4M, reacting for 15min, performing suction filtration by using a water system filter membrane with the thickness of 0.45 mu M, respectively cleaning filter residues by using ethanol and deionized water, and drying to obtain a precursor 2; catalyst 3: weighing 4g of sludge and 1.2g of manganese slag, placing the sludge and the manganese slag into 100mL of 0.45M potassium carbonate solution, reacting for 35min, adding nitric acid to enable the concentration of the nitric acid in the solution to be 0.4M, continuing to react for 15min, performing suction filtration by using a 0.45-micron water-based filter membrane, respectively cleaning filter residues by using ethanol and deionized water, and drying to obtain a precursor 3; catalyst 4: weighing 4g of sludge and 1.2g of manganese slag, placing the sludge and the manganese slag into 100mL of aqueous solution, stirring for 50min, performing suction filtration by using a 0.45-micrometer water system filter membrane, respectively cleaning filter residues by using ethanol and deionized water, and drying to obtain a precursor 4. And pyrolyzing the four prepared precursors for 2h at 800 ℃ in the nitrogen protection atmosphere respectively to obtain composite materials of a composite catalyst-1, a composite catalyst-2, a composite catalyst-3 and a composite catalyst-4 respectively.

100mg of each of the 4 composite catalysts were added to 100mL of 20mg/L hydroxamic acid-simulated organic wastewater (pH 6.04), and stirred for 60min to reach adsorption-desorption equilibrium, 2mL of 10g/L potassium persulfate was added, and stirring was continued at room temperature for 60 min. After the degradation reaction, the degradation rates of the benzohydroxamic acid in the water samples of the reaction systems of the composite catalyst-1, the composite catalyst-2, the composite catalyst-3 and the composite catalyst-4 are respectively 60.7%, 72.5%, 88.7% and 31.6%.

Example 4

Preparing a sludge-based biochar-manganese slag composite catalyst: and (3) respectively washing the sludge and the electrolytic manganese slag with water for 2 times, drying for 5 hours at the temperature of 60 ℃, respectively sieving the dried sludge and the manganese slag with 200-mesh sieves, and collecting undersize particles. Respectively weighing 4g of sludge and 1.0g of manganese slag, placing the sludge and the manganese slag into 100mL of 0.4M sodium carbonate solution, reacting for 40min, adding hydrochloric acid to enable the concentration of the hydrochloric acid to be 0.3M in a reaction system, continuing to react for 20min, performing suction filtration by using a 0.45-micrometer water system filter membrane, respectively cleaning filter residues by using ethanol and deionized water, drying, and pyrolyzing the obtained precursor at 800 ℃ for 90min under the argon protection atmosphere to obtain the sludge-based biochar-manganese slag composite catalyst.

30mg of sludge-based biochar-manganese slag composite catalyst is added into 50mL of the composite catalyst with pH values of 3.0, 5.0, 7.0, 9.0 and 11(pH value is HNO₃And NaOH) is added into the simulated ore dressing wastewater of the benzohydroxamic acid with the concentration of 20mg/L, 80 mu L of hydrogen peroxide with the mass fraction of 30 percent is respectively added after stirring for 60min to reach adsorption-desorption balance, and the stirring reaction is continued for 60min at room temperature. After completion of the catalytic reaction, the degradation rates of benzohydroxamic acid were measured to be 90.7%, 89.2%, 81.8%, 79.6% and 71.6%, respectively, as shown in fig. 6.

Example 5

The water quality conditions of the actual pharmaceutical wastewater, dye wastewater and mineral processing wastewater are shown in tables 1-3:

TABLE 1 pharmaceutical wastewater sample Properties

TABLE 2 characteristics of dye wastewater samples

Parameter(s)	pH	COD(mg/L)	BOD5(mg/L)	Acid orange (mg/L)	Color intensity
						Content (wt.)	10	335	94	60	Deep to

TABLE 3 characteristics of beneficiation wastewater samples

Parameter(s)	pH	COD	Na(mg/g)	K(mg/g)	Si(mg/g)	S(mg/g)
							Content (wt.)	11.37	203	275	20.6	51	211

Washing dry sludge for 2 times, sieving with a 200-mesh sieve, sieving electrolytic manganese slag with a 150-mesh sieve, respectively weighing sludge 4g below the sieve and manganese slag 0.5g below the sieve, placing in 100mL of 0.35M potassium carbonate solution, reacting for 30min, adding hydrochloric acid to make the concentration of the hydrochloric acid in the reaction system be 0.4M, continuing to react for 10min, performing suction filtration with a 0.45-micron water-based filter membrane, respectively cleaning the filter residue with ethanol and deionized water, drying, pyrolyzing the obtained precursor at 800 ℃ for 2h under the nitrogen protection atmosphere to obtain a sludge-based biochar-manganese slag composite catalyst, and keeping for later use

Respectively adding 20mg of the prepared sludge-based biochar-manganese slag composite catalyst into 200mL of pharmaceutical wastewater, dye wastewater and mineral processing wastewater, stirring for 60min, then adding 90 mu L of hydrogen peroxide with the mass fraction of 30%, and stirring and reacting for 90min at room temperature. After the catalytic reaction is finished, the residual contents of bisphenol A and norfloxacin in the pharmaceutical wastewater are respectively 47.4 mu g/L and 77.2 mu g/L, the residual content of acid orange in the dye wastewater is 1.5mg/L, and the residual COD concentration of the mineral processing wastewater is 55.8 mg/L.

Example 6

The soil containing polychlorinated biphenyl was obtained from a certain smelter in Tanzhou city, and the soil texture was as shown in Table 4:

parameter(s)	pH	Organic carbon content (%)	Dichlorobiphenyl (mg/kg)	Trichlorobiphenyl (mg/kg)
					Content (wt.)	8.33	3.22	13.8	10.4

Selecting the sludge-based biochar-manganese slag composite catalyst prepared in the example 4 as a catalyst, weighing about 5g of soil, adding 10mL of water, then adding 0.25g of the catalyst, uniformly stirring, adding 2.5mL of hydrogen peroxide with the mass fraction of 30%, continuously stirring for 300min, collecting the reacted soil, extracting with acetone, and determining the mass of the residual dichlorobiphenyl and trichlorobiphenyl to be 2.48mg/kg and 1.97mg/kg respectively through gas chromatography-mass spectrometry.