CN107099301B - Phosphorus-rich biological coke and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the field of polluted soil remediation, and particularly discloses a phosphorus-rich biological coke and a preparation method and application thereof, wherein biomass particles are used as raw materials, and the phosphorus-rich biological coke is obtained by carrying out phosphorus-rich and carbonization treatment, wherein the phosphorus-rich treatment is to dip the biomass particles/biological coke and a phosphorus-containing compound solution according to a set mass ratio for a preset time and then carry out dehydration and drying to obtain the phosphorus-rich biomass particles/phosphorus-rich biological coke; and the carbonization treatment comprises the steps of heating the biomass particles/the phosphorus-rich biomass particles in a pyrolysis furnace with a mixed atmosphere of nitrogen and carbon dioxide to a preset temperature according to a set heating rate, keeping the temperature for a preset time, and cooling the temperature to room temperature to obtain the biological coke/the phosphorus-rich biological coke. The phosphorus-rich biological coke prepared by the invention can be used as a soil conditioner and a repairing agent, has a good repairing effect on heavy metal contaminated soil, and has the advantages of simplicity, convenience, practicability, high efficiency and durability.

Description

A kind of phosphorus-enriched biocoke and its preparation method and application

technical field

The invention belongs to the field of contaminated soil remediation, and more particularly, relates to a phosphorus-rich biocoke and a preparation method and application thereof.

Background technique

According to the "National Soil Pollution Survey Bulletin" released in 2014, the overall situation of China's soil environment is not optimistic. The national soil pollution exceeding rate is 16.1%, of which 20 million hectares of land contaminated by heavy metals and more than 700,000 hectares of severely polluted land. 130,000 hectares of land had to be abandoned due to excessive cadmium content. Faced with the severe situation of soil pollution, on May 28, 2016, the State Council issued the Action Plan for the Prevention and Control of Soil Pollution, which clearly pointed out that it would comprehensively strengthen supervision and law enforcement, clarify the focus of supervision, and focus on monitoring cadmium, mercury, arsenic, lead, and cadmium in soil. Heavy metals such as chromium and organic pollutants such as polycyclic aromatic hydrocarbons and petroleum hydrocarbons, and focus on supervising non-ferrous metal mining and dressing, non-ferrous metal smelting, oil exploration, petroleum processing, chemical industry, coking, electroplating, tanning and other industries to ensure smooth soil pollution prevention and control. Finish. It can be seen that the treatment and restoration of heavy metal-contaminated soil is an urgent problem that needs to be solved, and the task is arduous and long way to go.

Currently, commonly used soil remediation agents include lime, zeolite, sea chlorite, iron-containing oxide materials, compost, steel slag, apatite and phosphate fertilizers. For the existing soil remediation agents, either in terms of economy, or in terms of environmental protection, or in terms of effectiveness, there are some defects in one way or another. For example, although phosphorus-containing minerals and compounds are cheap and have good remediation effects, the application of excessive phosphorus to the soil will bring many environmental problems, such as the whereabouts of phosphorus in the soil, the effect of excessive dissolved phosphorus on arsenic, Desorption of pollutants such as chromium, etc.

In recent years, biocoke has attracted extensive attention due to its wide source of raw materials, renewable resources, low production cost, ecological safety, no pollution, and large-scale promotion. The most potential environmental functional material. However, the pore structure and surface chemical properties of biocoke prepared only by simple pyrolysis are not outstanding in the adsorption and immobilization of heavy metals, which hinders its promotion as a soil remediation agent.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides a phosphorus-rich biocoke and a preparation method thereof and application in soil remediation, which grafts phosphorus-containing functional groups with fixed heavy metals to the surface of the biocoke with a porous structure , in order to prepare and obtain phosphorus-rich biocoke which can be used as soil conditioner and remediation agent and has good remediation effect on heavy metal polluted soil, which has the advantages of simplicity, efficiency and durability.

In order to achieve the above object, according to one aspect of the present invention, a preparation method of phosphorus-rich biocoke is proposed, which uses biomass particles as raw materials, firstly performs phosphorus-rich treatment to obtain phosphorus-rich biomass particles, and then processes the phosphorus-rich biomass particles. The biomass particles are carbonized to obtain the desired phosphorus-rich biocoke, or the biomass particles are first carbonized to obtain biocoke, and then the phosphorus-rich biocoke is subjected to phosphorus-rich treatment to obtain phosphorus-rich biocoke; wherein, the phosphorus-rich biocoke The treatment is to dehydrate and dry the biomass particles/biocoke and the phosphorus-containing compound solution according to a set mass ratio for a predetermined time to obtain phosphorus-rich biomass particles/phosphorus-rich biocoke; the carbonization treatment is to dehydrate the biomass particles/rich The phosphorus biomass particles are heated to a preset temperature at a set heating rate in a pyrolysis furnace with a mixed atmosphere of nitrogen and carbon dioxide, maintained for a predetermined time, and then cooled to room temperature to obtain biocoke/phosphorus-enriched biocoke.

Through the above scheme of the present invention, the phosphorus-containing functional group with immobilized heavy metals is effectively grafted to the surface of the biocoke with porous structure, so that when the phosphorus-rich biocoke is used to treat polluted soil, the phosphorus-containing functional group can effectively adsorb and fix the phosphorus in the soil. The ability of biocoke to absorb and fix heavy metals is further increased; at the same time, after biocoke is loaded with phosphorus-containing groups, it can be used as organic carbon fertilizer and organic phosphorus fertilizer to improve soil performance.

As a further preference, the biomass particles are one or several mixtures of agricultural waste, forestry waste, algae, sludge, and domestic waste. By using the above-mentioned wastes as raw materials for biomass preparation, the invention can realize the utilization of wastes while saving costs, and at the same time ensure that the prepared phosphorus-rich biocokes are returned to the soil from the soil as a soil remediation agent, and are used in the soil Pollution control, do not cause secondary pollution of soil.

As a further preference, the phosphorus-containing compound solution is one of H ₃ PO ₄ solution, K ₃ PO ₄ solution, (NH ₄ ) ₃ PO ₄ solution, KH ₂ PO ₄ solution, and NH ₄ H ₂ PO ₄ solution or several mixed solutions. In the present invention, the above solution is selected to realize the effective grafting of phosphorus-containing groups with a strong effect of fixing heavy metals on the surface of biocoke.

As a further preference, the phosphate ion concentration of the phosphorus-containing compound solution is 1mol/L-10mol/L, the mass mixing ratio of the phosphorus-containing compound solution and biomass particles/biocoke is 10:1-1:1, and the immersion The time is 2h-6h. In the present invention, the above-mentioned ion concentration, mass ratio and immersion time can be used to realize more effective grafting of phosphorus-containing groups on the surface of biocoke.

As a further preference, the particle size of the biomass particles ranges from 1 mm to 10 mm. In the present invention, when the particle size of the biomass particles is within the above range, a better phosphating reaction of the biocoke can be achieved, and continuous production is ensured.

As a further preference, the volume concentration of carbon dioxide in the mixed gas in the furnace is 10%-50%. At this volume concentration, the improvement of the pore structure of biocoke can be effectively ensured, and the mass transfer in the process of adsorbing and immobilizing heavy metals can be promoted.

As a further preference, the predetermined temperature is 500°C-1000°C, the heating rate is 5°C/min-20°C/min, and the time for maintaining the preset temperature is 0.5h-2h. Under the carbonization process parameters, the volatile components can be fully extracted in the biocoke preparation process, and the pore development of the biocoke can be promoted.

According to another aspect of the present invention, a phosphorus-rich biocoke is provided, which is prepared by the method.

According to another aspect of the present invention, an application of the phosphorus-rich biocoke in soil remediation is provided.

In general, compared with the prior art, the above technical solutions conceived by the present invention mainly have the following technical advantages: the present invention utilizes biomass to prepare phosphorus-rich biocoke and applies it to soil remediation, and innovatively combines The advantages of phosphorus-containing compounds and minerals in remediating heavy metal-contaminated soil and the advantages of biocoke porosity and environmental friendliness, "grafting" phosphorus-containing functional groups with fixed heavy metals to the porous structure of biocoke surface, increasing biocoke adsorption and immobilization Heavy metal capacity, innovating soil pollution control technology, providing technical measures for biomass resource utilization, realizing the organic combination of renewable resources development and utilization in environmental pollution control, and having huge social and economic benefits, and the present invention is a kind of The method is simple, efficient, durable and free from secondary pollution to remediate contaminated soil.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as there is no conflict with each other.

The present invention provides a method for preparing phosphorus-rich biocoke, which can be prepared in the following two ways. One is to use biomass particles as raw materials, first perform phosphorus-rich treatment to obtain phosphorus-rich biomass particles, and then process the phosphorus-rich biomass particles. The required phosphorus-rich biocoke is obtained by carbonizing the biomass particles; the other is to first carbonize the biomass particles to obtain the biocoke, and then subject the biocoke to the phosphorus-rich treatment to obtain the phosphorus-rich biocoke. The treatment sequence of carbonization treatment and carbonization treatment does not affect the acquisition of phosphorus-rich biocoke as the final treatment product, so it can be operated according to actual needs.

Wherein, when the biomass particles are subjected to phosphorus-enriching treatment, the biomass particles and the phosphorus-containing compound solution are immersed in a set mass ratio for a predetermined period of time, and then dehydrated and dried to obtain phosphorus-rich biomass particles; when the biocoke is subjected to phosphorus-rich treatment , is to dehydrate and dry the biocoke and phosphorus-containing compound solution according to the set mass ratio for a predetermined time to obtain phosphorus-rich biocoke.

When the biomass particles are carbonized, the biomass particles are heated to a preset temperature at a set heating rate in a pyrolysis furnace with a mixed atmosphere of nitrogen and carbon dioxide, kept for a predetermined time, and then cooled to room temperature to obtain Biocoke; when carbonizing phosphorus-rich biomass particles, the phosphorus-rich biomass particles are heated to a preset temperature at a set heating rate in a pyrolysis furnace with a mixed atmosphere of nitrogen and carbon dioxide, and then heated to a preset temperature at the pre-heating rate. The temperature was maintained for a predetermined time and then cooled to room temperature to obtain phosphorus-rich biocoke.

Preferably, the biomass particles are biomass particles made from one or more mixtures of agricultural wastes, forestry wastes, algae, sludge, and household garbage, and the particle size of the biomass particles is preferably in the range of 1 mm to 1 mm. 10mm.

Preferably, the phosphorus-containing compound solution is one or a mixture of H ₃ PO ₄ solution, K ₃ PO ₄ solution, (NH ₄ ) ₃ PO ₄ solution, KH ₂ PO ₄ solution, and NH ₄ H ₂ PO ₄ solution solution. The phosphate ion concentration of the phosphorus-containing compound solution is preferably set to 1mol/L-10mol/L, and the mass ratio of the phosphorus-containing compound solution to the biomass particles, or the mass ratio of the phosphorus-containing compound solution to the biocoke is preferably set to be 10:1-1:1, the immersion time is preferably set to 2h-6h.

Further, in order to improve the pore structure of biocoke, the volume concentration of carbon dioxide in the mixed gas in the furnace is 10%-50%.

Further preferably, the preset temperature is 500°C-1000°C, the heating rate is 5°C/min-20°C/min, and the time for maintaining the preset temperature is 0.5h-2h. Under the carbonization treatment parameters, the preparation of biocoke is guaranteed. During the process, the volatiles are fully extracted, which promotes the development of biocoke pores.

The phosphorus-rich biocoke prepared by the method not only has the characteristics of organic carbon fertilizer and organic phosphorus fertilizer, but also has the characteristics of porous structure and rich phosphorus heteroatom groups on the surface, and can be used as soil conditioner and repair agent to prevent heavy metal pollution. The soil is repaired in situ. For example, the phosphorus-rich biocoke prepared by the method of the present invention is used as a soil remediation agent. According to the soil pollution degree, the reasonable amount of phosphorus-rich biocoke applied per mu is 100kg/mu-1000kg/mu, and the soil effusion is discharged. Ensure that the soil is in a dry state, mix the phosphorus-rich biochar into the soil ploughing layer through rotary tillage or rake, and the mixing depth does not exceed the depth of the plant root system. Carry out random sampling inspection to ensure that the volume ratio of phosphorus-rich biocoke to soil is within the pre-calculated volume ratio range, and at the same time, randomly check the concentration of bioavailable heavy metals in the remediation soil after half a year to ensure that its concentration is within the national standard range.

The present invention will be further described in detail below through specific embodiments.

Example 1

Using one of agricultural wastes, forestry wastes, algae, sludge and domestic waste as raw materials to prepare biomass particles with a particle size of 1 mm, the biomass particles are mixed with H3PO4 solution (phosphate ion concentration is 1mol/L). ) mixed in a ratio of 1:1, soaked for 6 hours, then dehydrated and dried to obtain phosphorus-rich biomass particles, and then pyrolyzed the phosphorus-rich biomass particles in a mixed atmosphere of nitrogen and carbon dioxide (volume concentration of carbon dioxide is 10%). For carbonization in the furnace, the temperature is first heated to 1000°C at a heating rate of 20°C/min, then kept at 1000°C for 0.5 hours, and finally cooled to room temperature under air cooling to obtain the desired phosphorus-rich biocoke.

Example 2

Using the mixture of agricultural waste, algae and sludge as raw materials to prepare biomass particles with a particle size of 10mm, the biomass particles and phosphorus-containing compound solution (specifically, the mixed solution of K3PO4 solution and (NH4)3PO4 solution, the mixing ratio No limitation, ensure that the concentration of phosphate ions is 10mol/L) after mixing at a ratio of 1:10, soak for 2 hours, then dehydrate and dry to obtain phosphorus-rich biomass particles, and then put phosphorus-rich biomass particles in nitrogen and nitrogen. Carbonization in a pyrolysis furnace with a carbon dioxide mixed atmosphere (volume concentration of carbon dioxide is 50%), firstly heated to 500 °C at a heating rate of 5 °C/min, then kept at 500 °C for 2 hours, and finally cooled under water cooling conditions To room temperature, the desired phosphorus-rich biocoke was obtained.

Example 3

Biomass particles with a particle size of 5 mm are prepared from the mixture of agricultural waste, sludge and domestic waste as raw materials, and the biomass particles are carbonized in a pyrolysis furnace with a mixed atmosphere of nitrogen and carbon dioxide (the volume concentration of carbon dioxide is 20%). First, the temperature was raised to 800°C at a heating rate of 10°C/min, then kept at 800°C for 1 hour and then cooled to room temperature under air cooling to obtain biocoke; 5mol/L) in a ratio of 1:5, immersed for 4 hours, and then dehydrated and dried to obtain the desired phosphorus-rich biocoke.

Example 4

Using sludge as raw material to prepare biomass particles with a particle size of 8 mm, the biomass particles are carbonized in a pyrolysis furnace with a mixed atmosphere of nitrogen and carbon dioxide (the volume concentration of carbon dioxide is 30%), and the heating rate is first 15 ° C/min. The temperature was raised to 600°C, then kept at 600°C for 1.5 hours, and then cooled to room temperature under water cooling to obtain biocoke; then biocoke and K3PO4 solution (phosphate ion concentration of 8mol/L) were 1:3. After mixing in proportions, soak for 3 hours, and then dehydrate and dry to obtain the desired phosphorus-rich biocoke.

Example 5

The phosphorus-rich biocoke prepared in Examples 1-4 was used as a soil conditioner and a remediation agent to carry out in-situ restoration of heavy metal-contaminated soil. According to the soil pollution degree, the amount of phosphorus-rich biocoke reasonably applied per mu was 100kg/mu-1000kg/mu. Mu, drain the soil effusion to ensure that the soil is in a dry state, and mix the phosphorus-rich biochar into the soil ploughing layer by rotary tillage or raking, and the mixing depth does not exceed the depth of the plant root system. Mix evenly, and conduct random sampling inspection of the soil to ensure that the volume ratio of phosphorus-rich biocoke to soil is within the pre-calculated volume ratio range. At the same time, after half a year, the concentration of bioavailable heavy metal arsenic in the soil is 0.2-1.0ppm. , copper is 35-50ppm, lead is 0.2-1.0ppm, chromium is 2.0-10ppm, cobalt is 1.0-4.0ppm, nickel is 1.0-4.0ppm, cadmium is 0.1ppm, mercury is 0.02ppm, the concentrations are all in the national regulations Within the standard range, it shows that the phosphorus-rich biocoke prepared by the present invention has an effective improvement effect on heavy metal polluted soil.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (7)

1. an application of phosphorus-enriched biocoke in heavy metal contaminated soil remediation, is characterized in that, the preparation method of described phosphorus-enriched biocoke is as follows: take biomass particle as raw material first biomass particle is nitrogen and carbon dioxide in mixed atmosphere In the pyrolysis furnace, after heating up to a preset temperature at a set heating rate, keeping it for a predetermined time and then cooling to room temperature to obtain biocoke, and then immersing the biocoke and phosphorus-containing compound solution for a predetermined time at a set mass ratio and then dehydrating drying to obtain phosphorus-rich biocoke; in this way, the phosphorus-containing functional groups with fixed heavy metals are effectively grafted to the surface of the biocoke with porous structure, so that when the phosphorus-rich biocoke is used as a soil conditioner and a remediation agent for soil treatment, the Phosphorus-containing functional groups effectively adsorb and fix heavy metals in soil, increasing the ability of biocoke to adsorb and fix heavy metals, and biocoke loaded with phosphorus-containing groups simultaneously improves soil performance as organic carbon fertilizer and organic phosphorus fertilizer. 2 . The application according to claim 1 , wherein the biomass particles are one or more mixtures of agricultural waste, forestry waste, algae, sludge, and domestic waste. 3 . 3. The application according to claim 1, wherein the phosphorus-containing compound solution is H ₃ PO ₄ solution, K ₃ PO ₄ solution, (NH ₄ ) ₃ PO ₄ solution, KH ₂ PO ₄ solution, NH One or several mixed solutions of ₄ H ₂ PO ₄ solutions. 4. the application according to any one of claim 1-3 is characterized in that, the phosphate ion concentration of described phosphorus-containing compound solution is 1mol/L-10mol/L, and the quality of phosphorus-containing compound solution and biocoke The mixing ratio is 10:1-1:1, and the immersion time is 2h-6h. 5. The application according to claim 1, wherein the biomass particle size ranges from 1 mm to 10 mm. 6 . The application according to claim 1 , wherein the volume concentration of carbon dioxide in the mixed gas in the furnace is 10%-50%. 7 . 7. The application according to claim 1, wherein the preset temperature is 500°C-1000°C, the heating rate is 5°C/min-20°C/min, and the time for maintaining the preset temperature is 0.5h-2h .