CN108793400A - A kind of denitrogenation dephosphorizing composite material and preparation method and application - Google Patents

Abstract

The invention discloses a nitrogen and phosphorus removal composite material and its preparation method and application. The nitrogen and phosphorus removal composite material is obtained by mixing waste liquid rich in magnesium salt, calcined dolomite, desulfurized gypsum and iron sulfide. The nitrogen and phosphorus removal composite material of the present invention is used for constructing seepage dams on ditches and river courses, or for infiltration treatment of artificial wetlands. Water flows through the filter material in a filtering manner, and the material slowly releases calcium ions and hydroxyl groups, and reacts with phosphorus in the water to form hydroxyl groups. Apatite precipitation removes trace amounts of phosphorus in the water, and the concentration of phosphorus in the effluent reaches the fourth-class standard for ground water; microorganisms attached to the surface and internal pores of the material particles convert nitrate nitrogen and ammonia nitrogen into nitrogen under anoxic conditions.

Description

A kind of denitrification and dephosphorization composite material and its preparation method and application

technical field

The invention relates to a nitrogen and phosphorus removal composite material and its preparation method and application, belonging to the technical field of sewage treatment.

Background technique

With the aggravation of water pollution, eutrophication has generally occurred in surface water bodies in my country. The state has set up a major special project for water pollution control to conduct research, invested huge sums of money in the construction of urban sewage treatment facilities, and improved the treatment rate of urban domestic sewage. However, at present, the aerobic activated sludge process is generally used in the treatment of urban domestic sewage, but the concentrations of total nitrogen and total phosphorus in the effluent water of aerobic biological treatment still reach 20-35 mg/L and 0.3-3.0 mg/L respectively, which are the main factors for lake water. 10-50 times of the second standard. In many cases, it is difficult for domestic sewage to meet the national first-class A discharge standard after secondary treatment, and it is necessary to increase advanced treatment facilities to ensure that the effluent meets the standard. Even if domestic sewage treatment meets the drainage standard, for eutrophic water bodies, stricter denitrification and phosphorus removal are required to ensure the ecological environment of the water bodies. In particular, after domestic sewage treatment is used as landscape water to realize the recycling of wastewater, the secondary treatment effluent of domestic sewage treatment plants needs further denitrification and phosphorus removal to meet the application requirements of wastewater recycling.

The treatment of high-concentration phosphorus in wastewater is generally carried out by lime precipitation, iron salt precipitation or aluminum salt precipitation. The precipitated calcium phosphate has a large solubility product at a neutral pH value. Controlling a higher pH value to ensure a lower phosphorus concentration in the precipitation phosphorus removal effluent will not only cause excessive consumption of chemicals, but also cause the pH value of the effluent to be too high. Can not meet the emission requirements. Therefore, the treatment of low-concentration phosphorus with lime cannot achieve the expected effect. When the concentration of phosphorus in water is very low, iron, aluminum ions and phosphate radicals form a sol, and it is difficult to separate phosphate precipitates from water with commonly used sedimentation tanks. In order to improve the effect of precipitation phosphorus removal, it is necessary to add a precipitant far exceeding the dosage required for precipitation phosphorus, resulting in a large amount of iron and aluminum metal ions.

Many scholars at home and abroad have done research on phosphorus removal by adsorption. Commonly used phosphorus removal adsorbents mainly include zeolite, calcite, bentonite, attapulgite clay, vermiculite, red mud, fly ash and other natural minerals and solid wastes. , these materials have a certain adsorption effect on phosphorus, but the adsorption capacity is low and regeneration is difficult. In order to improve the adsorption capacity of phosphorus removal adsorbents, many scholars have carried out research on the preparation of phosphorus removal composite materials, including using organic waste as a carrier to load metal ions such as La, Ce, Fe, etc., using quartz sand, montmorillonite, attapulgite, zeolite, etc. La, Al, Fe and other minerals are used as carriers to prepare modified adsorbents, and these composite adsorbents have high phosphorus removal adsorption. According to the research results at home and abroad, the reason why the above-mentioned composite materials have better adsorption is that the surface active components of the adsorbent Fe ³⁺ , Al ³⁺ , La ³⁺ , Ce ³⁺ hydroxide and phosphate have strong chemical bonding. The adsorption materials modified with rare earth elements have high phosphorus removal efficiency, but they are expensive, and the prospect of popularization and application is not great. Inexpensive and efficient adsorbents for phosphorus removal are still to be developed.

Contents of the invention

The purpose of the present invention is to avoid the disadvantages of the above-mentioned prior art, and aims to provide a composite material for denitrification and dephosphorization and its preparation method and application.

The composite material for denitrification and dephosphorization of the invention is obtained by mixing waste liquid rich in magnesium salt, calcined dolomite, desulfurized gypsum and iron sulfide according to the proportion and then processing.

The waste liquid rich in magnesium salt includes waste liquid rich in magnesium sulfate, or waste liquid rich in magnesium sulfate and magnesium chloride; the mass concentration of magnesium ions in the waste liquid rich in magnesium salt is ≥ 1%.

The calcined dolomite is calcined at 800-1000°C until the dolomite with a dolomite mass content ≥ 90% is completely decomposed, and then decomposed into powder by adding water;

The desulfurized gypsum is a powder obtained by drying and crushing desulfurized gypsum (ie limestone-gypsum desulfurization product) through a 100-mesh sieve.

The iron sulfide is a powder obtained by crushing colloidal pyrite ore with a pyrite content greater than 70% or pyrrhotite ore with a pyrrhotite content greater than 80% and passing through a 100-mesh sieve, or obtained by mining flotation Pyrite, pyrrhotite concentrate powder, the content of harmful heavy metals is less than 0.1%.

The feed ratio of the magnesium-salt-rich waste liquid to calcined dolomite is based on the Mg in the magnesium-salt-rich waste liquid and the Ca in the calcined dolomite, and the molar ratio is 2:1-1:2; The mass ratio is 5:1-1:10; the feed ratio of iron sulfide and magnesium salt-rich waste liquid is based on S in iron sulfide and Mg in rich magnesium salt waste liquid, and the molar ratio is 2:1-1: 2.

The desulfurized gypsum in the raw material can be replaced by anhydrite that has been crushed and passed through a 100-mesh sieve.

The preparation method of the nitrogen and phosphorus removal composite material of the present invention is to mix the waste liquid rich in magnesium salt, calcined dolomite, desulfurized gypsum and iron sulfide according to the proportion, and shape it into spherical or rod-shaped particles with a diameter of 2-20mm, and then Standing reaction and solidification for 2-10 days under ambient temperature and air atmosphere, spraying water to remove dissolved salts, and obtaining granular nitrogen and phosphorus removal composite materials.

Or first convert the desulfurized gypsum into anhydrous calcium sulfate by calcining at 500-800°C, then mix the components according to the proportion, shape them into spherical or rod-shaped particles with a diameter of 2-20mm, and then heat them under ambient temperature and air atmosphere Stand for reaction and solidification for 2-10 days, spray and wash to remove dissolved salts, and obtain granular nitrogen and phosphorus removal composite materials.

The application method of the denitrification and dephosphorization composite material of the present invention is to use the denitrification and dephosphorization composite material for constructing seepage dams on ditches and river courses, or for infiltration treatment of artificial wetlands, water flows through the filter material in a filtering manner, and the material Calcium ions and hydroxyl groups are slowly released, and react with phosphorus in water to form hydroxyapatite precipitation to remove trace phosphorus in water, and the concentration of phosphorus in the effluent reaches the fourth-class standard of ground water; microorganisms attached to the surface and internal pores of material particles transform under anoxic conditions Nitrate nitrogen and ammonia nitrogen are nitrogen gas.

The beneficial effects of the nitrogen and phosphorus removal composite material of the present invention are reflected in the following aspects:

1. The components in the dolomite react with the magnesium salt solution to form new phases of gypsum and brucite, which play a role in cementation, and can easily obtain granular materials with higher strength without the need for additional binders.

2. In the material of the present invention, magnesium oxide and brucite slowly dissolve and release hydroxyl to maintain the pH value of the pore liquid between 9-10, and slowly dissolve gypsum and anhydrite to maintain a calcium ion concentration of 30-80mg/L in water, which promotes the formation of trace amounts in water. Phosphorus is fixed on the outer surface and in the inner pores of the particulate material.

3. Under anoxic conditions, microorganisms use ammonia nitrogen and iron sulfide in the material as electron donors to convert nitrate and ammonia nitrogen into nitrogen, and the new iron hydroxide has the effect of fixing phosphorus.

Detailed ways

Non-limiting examples of the invention are described below.

Example 1:

The preparation method of the nitrogen and phosphorus removal composite material in this embodiment is as follows:

1. Raw materials

Waste liquid rich in magnesium salt: choose waste liquid rich in magnesium sulfate, the mass concentration of magnesium ions is 4.5%;

Calcined dolomite: Calcine high-quality dolomite at 900°C until the dolomite is completely decomposed, then add water to digest it into powder;

Desulfurization gypsum: use desulfurization gypsum (that is, limestone-gypsum desulfurization product) as raw material, dry and pulverize the powder obtained after passing through a 100-mesh sieve;

Iron sulfide: powder obtained by crushing colloidal pyrite ore with a pyrite content of 75% and passing through a 100-mesh sieve;

2. Proportion

The feed ratio of magnesium-salt-rich waste liquid to calcined dolomite is based on Mg in magnesium-salt-rich waste liquid and Ca in calcined dolomite, the molar ratio is 1:1; the mass ratio of desulfurized gypsum to calcined dolomite is 2:1 ; Feed ratio of iron sulfide and waste liquid rich in magnesium salt is based on S in iron sulfide and Mg in waste liquid rich in magnesium salt, and the molar ratio is 2:1.

3. Preparation

Mix waste liquid rich in magnesium salt, calcined dolomite, desulfurized gypsum and iron sulfide according to the proportion, shape it into spherical or rod-shaped particles with a diameter of 2-20mm, and then stand at ambient temperature and air atmosphere for 2 days to react and consolidate , and spray water to remove dissolved salts, and obtain granular nitrogen and phosphorus removal composite materials.

4. Application

The denitrification and phosphorus removal composite material prepared in this example is used as artificial wetland filler. Water flows through the filter material in a filtering manner, and the material slowly releases calcium ions and hydroxyl groups, and reacts with phosphorus in the water to form hydroxyapatite precipitation to remove trace amounts of phosphate in the water. Phosphorus, microorganisms attached to the surface and internal pores of material particles convert nitrate nitrogen and ammonia nitrogen into nitrogen gas under anoxic conditions. The concentration of phosphorus in the effluent is less than 0.2mg/L, the concentration of ammonia nitrogen is less than 1.50mg/L, and the concentration of COD is less than 20mg/L, meeting the Class III standard for surface water bodies.

Example 2:

The preparation method of the nitrogen and phosphorus removal composite material in this embodiment is as follows:

1. Raw materials

Waste liquid rich in magnesium salt: choose waste liquid rich in magnesium sulfate, the mass concentration of magnesium ions is 3%;

Calcined dolomite: Calcine high-quality dolomite at 800-1000°C until the dolomite is completely decomposed, then add water to digest it into powder;

Desulfurization gypsum: use desulfurization gypsum (that is, limestone-gypsum desulfurization product) as raw material, dry and pulverize the powder obtained after passing through a 100-mesh sieve;

Iron sulfide: pyrrhotite concentrate powder obtained by mining flotation;

2. Proportion

The feed ratio of magnesium-salt-rich waste liquid to calcined dolomite is based on Mg in magnesium-salt-rich waste liquid and Ca in calcined dolomite, the molar ratio is 2:1; the mass ratio of desulfurized gypsum to calcined dolomite is 1:1 ; Feed ratio of iron sulfide and waste liquid rich in magnesium salt is based on S in iron sulfide and Mg in waste liquid rich in magnesium salt, and the molar ratio is 1:1.

3. Preparation

Mix waste liquid rich in magnesium salts, calcined dolomite, desulfurized gypsum and iron sulfide according to the ratio, shape them into spherical or rod-shaped particles with a diameter of 5mm, and then stand for reaction and solidification at ambient temperature and air atmosphere for 10 days, spray Washing with water removes dissolved salts, and obtains granular nitrogen and phosphorus removal composite materials.

4. Application

The denitrification and phosphorus removal composite material prepared in this example is used to construct a permeable filter material on the ditch. The material slowly releases calcium ions and hydroxyl groups, and reacts with phosphorus in water to form hydroxyapatite precipitation to remove trace amounts of phosphorus in water. The material particles Microorganisms attached to the surface and internal pores convert nitrate nitrogen and ammonia nitrogen to nitrogen gas under anoxic conditions. The concentration of phosphorus in the effluent is less than 0.2mg/L, the concentration of ammonia nitrogen is less than 1.50mg/L, and the concentration of COD is less than 20mg/L, meeting the Class III standard for surface water bodies.

Example 3:

The preparation method of the nitrogen and phosphorus removal composite material in this embodiment is as follows:

1. Raw materials

Waste liquid rich in magnesium salt: choose waste liquid rich in magnesium sulfate, the mass concentration of magnesium ions is 3%;

Calcined dolomite: Calcine high-quality dolomite at 800-1000°C until the dolomite is completely decomposed, then add water to digest it into powder;

Desulfurization gypsum: dry the desulfurization gypsum, calcine it at 500-800°C to convert it into anhydrite, and crush it through a 100-mesh sieve;

Iron sulfide: pyrrhotite concentrate powder obtained by mining flotation;

2. Proportion

The feed ratio of magnesium-salt-rich waste liquid to calcined dolomite is based on Mg in magnesium-salt-rich waste liquid and Ca in calcined dolomite, and the molar ratio is 1:2; the mass ratio of desulfurized gypsum to calcined dolomite is 1:2 ; Feed ratio of iron sulfide and waste liquid rich in magnesium salt is based on S in iron sulfide and Mg in waste liquid rich in magnesium salt, and the molar ratio is 2:1.

3. Preparation

Mix waste liquid rich in magnesium salts, calcined dolomite, desulfurized gypsum and iron sulfide according to the ratio, shape them into spherical or rod-shaped particles with a diameter of 10mm, and then stand for reaction and solidification at ambient temperature and air atmosphere for 10 days, spray Washing with water removes dissolved salts, and obtains granular nitrogen and phosphorus removal composite materials.

4. Application

The denitrification and phosphorus removal composite material prepared in this example is used to build an infiltration dam on a river surge. The material slowly releases calcium ions and hydroxyl groups, and reacts with phosphorus in water to form hydroxyapatite precipitation to remove trace amounts of phosphorus in water. The material particles Microorganisms attached to the surface and internal pores convert nitrate nitrogen and ammonia nitrogen to nitrogen gas under anoxic conditions. The concentration of phosphorus in the effluent is less than 0.2mg/L, the concentration of ammonia nitrogen is less than 1.50mg/L, and the concentration of COD is less than 20mg/L, meeting the Class III standard for surface water bodies.

Claims (7)

1. a kind of denitrogenation dephosphorizing composite material, it is characterised in that：Be by be rich in magnesium salts waste liquid, dolime, desulfurated plaster with And iron sulfide mixing post-processing obtains.

2. denitrogenation dephosphorizing composite material according to claim 1, it is characterised in that：

The magnesium salts waste liquid that is rich in includes the waste liquid rich in magnesium sulfate, or the waste liquid rich in magnesium sulfate and magnesium chloride；The richness Magnesium ion mass concentration >=1% in waste liquid containing magnesium salts；

The dolime is that the dolomite of dolomite mass content >=90% is fired to dolomite at 800-1000 DEG C It decomposes completely, water resolution is added to become powdery；

The desulfurated plaster be using desulfurated plaster as raw material, it is dry and crush sieve with 100 mesh sieve after the powder that obtains；

The iron sulfide be by pyrite content more than 70% Colloid form pyrite ore or magnetic iron ore content be more than 80% Ore reduction and the powder that sieves with 100 mesh sieve, or be pyrite, magnetic iron ore concentrate powder that mining industry flotation obtains, have The content of evil heavy metal is less than 0.1%.

3. denitrogenation dephosphorizing composite material according to claim 1 or 2, it is characterised in that：

The rate of charge rich in magnesium salts waste liquid and dolime to be rich in magnesium salts waste liquid in terms of Mg and Ca in dolime, Molar ratio is 2:1-1:2；The mass ratio of desulfurated plaster and dolime is 5:1-1:10；Iron sulfide be rich in magnesium salts waste liquid Rate of charge by S in iron sulfide with rich in Mg in magnesium salts waste liquid in terms of, molar ratio 2:1-1:2.

4. denitrogenation dephosphorizing composite material according to claim 2, it is characterised in that：

The desulfurated plaster is substituted with the anhydrite for crushing and sieving with 100 mesh sieve.

5. the preparation method of any denitrogenation dephosphorizing composite material in a kind of claim 1-4, it is characterised in that：

It will be enriched in magnesium salts waste liquid, dolime, desulfurated plaster and iron sulfide and measure mixing according to the ratio, be shaped to spherical or stick Then shape particle, diameter 2-20mm stand reaction consolidation 2-10 days, water spray elution removal under environment temperature and air atmosphere Dissolving salt obtains graininess denitrogenation dephosphorizing composite material.

6. the preparation method of any denitrogenation dephosphorizing composite material in a kind of claim 1-4, it is characterised in that：

Desulfurated plaster is calcined at 500-800 DEG C first and is changed into dead plaster, then each component is measured to mixing according to the ratio, It is shaped to spherical or rod-shpaed particle, then a diameter of 2-20mm stands reaction consolidation 2- under environment temperature and air atmosphere 10 days, water spray elution removal dissolving salt obtains graininess denitrogenation dephosphorizing composite material.

7. the application of any denitrogenation dephosphorizing composite material in a kind of claim 1-4, it is characterised in that：

The denitrogenation dephosphorizing composite material is used for the structure infiltration dam on irrigation canals and ditches, river, or at artificial swamp infiltration Reason, water flow through filtrate with filter type, and the phosphorus in material slow release calcium ion and hydroxyl, with water acts on forming hydroxyapatite It precipitates that phosphorus micro in water removal, water outlet phosphorus concentration is gone to reach four class standard of surface water body；Material granule surface and internal holes The microorganism of gap attachment converts nitrate nitrogen under anoxic conditions and ammonia nitrogen is nitrogen.