WO2022022090A1 - Method for recovering vivianite from sludge incineration ash - Google Patents

Abstract

The present invention relates to a method for recovering vivianite from sludge incineration ash, comprising the following steps: (1) mixing sludge incineration ash with acid liquor, heating to leach phosphorus, and then performing filtering and separating to obtain leached filtrate and leached filter residues; (2) adjusting the pH value of the leached filtrate with alkali liquor, adding an adsorbent for phosphorus adsorption, and then performing filtering and separating to obtain adsorbed filtrate and adsorbed filter residues; (3) mixing the adsorbed filter residues with alkali liquor to perform phosphorus desorption, and then performing filtering and separating to obtain desorbed filtrate and desorbed filter residues; and (4) in an anaerobic environment, adding ferrous ions into the desorbed filtrate, adjusting the pH value of the desorbed filtrate to carry out reaction, then performing filtering and separating to obtain filter residues and filtrate, and washing and drying the filter residues to obtain vivianite. Compared with the prior art, the present invention eliminates the interferences of other elements in the sludge incineration ash, obtains a high-quality vivianite product, can alleviate the problem of phosphorus resource shortage, and is simple in technological process and convenient in operation.

Description

A kind of method for recovering blue iron ore from sludge incineration ash technical field

The invention relates to the field of comprehensive utilization of solid waste resources, in particular to a method for recovering blue iron ore from sludge incineration ash.

Background technique

Phosphorus (P) is an essential element in living organisms and plays a vital role in life activities. As the global population continues to increase, so does the demand for phosphorus in agriculture and industry. However, phosphorus is a limited and non-renewable resource, about 20 million tons of phosphate rock is mined every year, and the price of phosphorus continues to rise. At the same time, the high-quality and easy-to-minable phosphate rock is gradually exhausted, and the phosphate rock with high impurities and high mining difficulty will be widely used, which will further increase the production cost of phosphorus products. According to the current rate of phosphorus exploitation and use, phosphorus resources with economic benefits of exploitation can only be maintained for about 50-100 years. Therefore, it is necessary to enhance the recycling and utilization of phosphorus resources, develop sustainable methods for recovering phosphorus resources from phosphorus-containing wastes, and make phosphorus resources circulate in a cyclic system, thereby reducing the mining of phosphorus mines.

The main disposal methods of sewage treatment plant sludge include agricultural and landscaping utilization, incineration and landfill. Direct use in agriculture is controversial because sludge collects pollutants in sewage, containing pathogens, heavy metals, and organic pollutants (eg, pharmaceuticals and personal care products). Incineration can destroy the organic pollutants present in the sludge and destroy pathogens, in this case, the sludge incineration ash is produced, which has a concentrated mineral composition, usually with a high _{P2O5 content} , mass percent content About 13.7% to 25.7%, therefore, sludge incineration ash is considered as a potential phosphorus resource. Except for P ₂ O ₅ , the main components of sludge incineration ash are SiO ₂ , CaO, Al ₂ O ₃ , Fe ₂ O ₃ , MgO, and contain toxic heavy metals such as cadmium, chromium, copper, lead, manganese, zinc, nickel. Therefore, these elements must be efficiently removed when recovering phosphorus from sludge incineration ash. At present, the commonly used sludge phosphorus recovery methods mainly include: acid/alkali leaching and precipitation, adsorption/desorption, biological leaching, supercritical extraction and thermochemical treatment, and then prepare inorganic phosphorus fertilizer, struvite and phosphoric acid. Among these methods, acid/alkali leaching and precipitation methods are widely used, by adding reagents to form insoluble phosphates, such as struvite, from phosphorus dissolved in sludge.

Vivianite (Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) is a very stable phosphorus-iron compound that occurs naturally in lake sediments, iron-rich soils and anaerobic environments. It is the basic raw material for lithium iron phosphate (LiFePO ₄ ) lithium-ion batteries; it can also be used as a slow-release phosphate fertilizer. The price of blue iron ore is as high as 51-96 euros/kg phosphorus, which is much higher than struvite (9.8 euros/kg phosphorus) and aluminum phosphate (3.4 euros/kg phosphorus). Compared with struvite, cyanite can be used in electronics industry and agriculture, with high economic value and better prospects for phosphorus recovery.

Patent CN110691758A relates to a method and system for recovering phosphate from a stream such as a waste stream, sewage or another sludge stream. The method comprises the steps of: providing an incoming stream comprising an initial amount of phosphate; dosing and/or controlling iron salts into the stream so that a precipitate is formed in the stream, wherein the precipitate contains a cyanite-like structure comprising more than 60% of the initial amount of phosphate entering the stream, and preferably further comprising the steps of: separating the cyanite-like structure from the stream; and Phosphate recovery from isolated chromite-like structures. However, this patent does not carry out enrichment and impurity removal of phosphate in the flow, and the high content of organic phosphorus in the flow cannot be converted into blue iron ore, thereby limiting the formation of blue iron ore; After all the sulfides are converted into iron sulfide, the cyanite begins to form; and the sludge needs to be kept under anaerobic or anoxic conditions for 20 to 30 days in the experiment, and the experiment takes a long time.

SUMMARY OF THE INVENTION

The purpose of this invention is to provide a kind of method of reclaiming blue iron ore from sludge incineration ash, eliminates the interference of other elements in the sludge incineration ash, obtains high-quality blue iron ore product, can alleviate the shortage problem of phosphorus resources , the process is simple and the operation is convenient.

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

A method for recycling blue iron ore from sludge incineration ash, the method comprises the following steps:

(1) leaching of sludge incineration ash: the sludge incineration ash is mixed with acid solution and heated to carry out leaching of phosphorus, and then the leaching filtrate and leaching filter residue are obtained by filtration and separation, and the leaching filter residue can be disposed as general solid waste. inversion leaching;

(2) adsorption of the leaching filtrate: adjust the pH value of the leaching filtrate with alkali liquor, then add an adsorbent to carry out the adsorption of phosphorus, and then filter and separate to obtain the adsorption filtrate and the adsorption filter residue, and the adsorption filtrate is refluxed for the leaching step;

(3) Desorption of the adsorption filter residue: the adsorption filter residue is mixed with the lye and the phosphorus is desorbed, and then the desorption filtrate and the desorption filter residue are obtained by filtration and separation;

(4) Preparation of blue iron ore: in an anaerobic environment, add ferrous ions to the desorption filtrate, and adjust the pH value of the desorption filtrate to carry out the reaction. During the reaction, nitrogen gas is continuously introduced, and then the filter residue is obtained by filtration and separation. and the filtrate, and the filter residue is washed and dried to obtain blue iron ore. Filtration and separation were carried out by vacuum filtration.

Preferably, in step (1), the acid solution is an industrial grade inorganic acid solution or an organic acid solution, and the inorganic acid solution is selected from one or more of sulfuric acid solution, hydrochloric acid solution or nitric acid solution, and the The organic acid solution is selected from one or more of a citric acid solution or an oxalic acid solution, and the concentration of the acid solution is 0.2-1 mol/L.

Preferably, in step (1), the liquid-solid ratio of the acid solution to the sludge incineration ash is 0.01-0.02 L/g, the leaching temperature is 25-55°C, and the leaching time is 0.5-2 h.

Preferably, in step (2), the adsorbent is hydrotalcite. Further preferably, the hydrotalcite is selected from one or more of industrial grade magnesium-iron hydrotalcite, magnesium-aluminum hydrotalcite, zinc-aluminum hydrotalcite, magnesium-manganese hydrotalcite or zinc-iron hydrotalcite.

Preferably, in step (2), the lye solution is an aqueous sodium hydroxide solution of technical grade, and the concentration of the aqueous sodium hydroxide solution is 0.2-0.3 mol/L.

Preferably, in step (2), stirring is performed at the same time of adsorption, the stirring speed is 150-300 r/min, and the stirring time is 3-8 h.

Preferably, in step (2), the pH value of the leaching filtrate is adjusted to 5-7, the liquid-solid ratio of the leaching filtrate and the adsorbent is 0.025-0.05L/g, the adsorption temperature is 25-35°C, and the adsorption time is 3 to 8 hours.

Preferably, in step (3), the lye solution is an aqueous sodium hydroxide solution of technical grade, and the concentration of the aqueous sodium hydroxide solution is 0.1-1 mol/L.

Preferably, in step (3), stirring is performed while desorption, the stirring speed is 300-450 r/min, and the stirring time is 12-36 h.

Preferably, in step (3), the liquid-solid ratio of the alkali solution to the adsorption filter residue is 0.1-0.2 L/g, the desorption temperature is 25-35°C, and the desorption time is 12-36 h.

Preferably, in step (3), the desorption filter residue is washed with deionized water, calcined at 300-450° C. for 2.5-3.5 h (preferably 3 h) for regeneration, and then returned to step (2) as an adsorbent for use.

Preferably, in step (4), the ferrous ion comes from one or more of ferrous chloride, crystalline hydrate of ferrous chloride, ferrous sulfate or crystalline hydrate of ferrous sulfate, preferably Crystalline hydrate of ferrous chloride. Ferrous chloride, crystalline hydrate of ferrous chloride, ferrous sulfate and crystalline hydrate of ferrous sulfate are all industrial grades.

Preferably, in step (4), sodium hydroxide solution and hydrochloric acid solution are used to adjust the pH value of the desorption filtrate. The sodium hydroxide solution is a low concentration solution with a concentration of 0.2mol/L, and the concentration of the hydrochloric acid solution is also 0.2mol/L.

Preferably, in step (4), nitrogen gas is used to create an anaerobic environment.

Preferably, in step (4), stirring is performed at the same time as the reaction, the stirring speed is 100-150 r/min, and the stirring time is 48-96 h.

Preferably, in step (4), the added molar ratio of ferrous ions to phosphorus is 1.5 to 1.6, the dosage of ferrous ions is determined according to the phosphorus concentration in the desorption filtrate, and the pH value of the desorption filtrate is adjusted to 6 ~8, the reaction temperature is 25~35°C, and the reaction time is 48~96h. The molar ratio of 1.5 to 1.6 can completely generate cyanite from phosphorus in the desorption filtrate, and a sufficient amount of iron can avoid other interference factors to interfere with the generation of cyanite. The pH value of the desorption filtrate ensures that ferrous ions Will not change to other valence states (elemental iron or ferric iron).

Preferably, in step (4), the filter residue is washed with deionized water and ethanol in sequence, and then dried under vacuum at 25-35° C. for 6-8 hours. The concentration of ethanol was 98 wt%.

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

1. The present invention proposes a process for recycling ash phosphorus from sludge incineration, adopts the method of phosphorus adsorption, phosphorus desorption and cyanite precipitation, eliminates the interference of other elements in the sludge incineration ash, and obtains high-quality cyanite The product has simple technological process and convenient operation, and the obtained blue iron ore is an important industrial raw material, which is widely used and has good market potential and significant economic and environmental benefits.

2. The hydrotalcite adsorbent can be reused after regeneration, and the regenerated hydrotalcite still has good phosphorus adsorption capacity.

3. The present invention provides a technology for preparing blue iron ore by utilizing phosphorus in sludge incineration ash, which can alleviate the shortage of phosphorus resources.

Description of drawings

Fig. 1 is the method step schematic diagram of the present invention;

FIG. 2 is a specific diagram of the method steps of the present invention.

detailed description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The reagents used in the present invention all adopt industrial grade materials.

Example 1

A method for recovering blue iron ore from sludge incineration ash, the treatment object is the sludge incineration ash of a sewage treatment plant, and X-ray fluorescence spectroscopy (XRF) detection shows that the phosphorus mass percentage content in the sludge incineration ash is 5.2 %. Phosphorus is recovered from the sludge incineration ash to prepare blue iron ore, as shown in Figures 1 and 2, and the method specifically includes the following steps:

(1) 100g of sludge incineration ash is mixed and heated with 2L of hydrochloric acid solution (0.5mol/L) (that is, the liquid-solid ratio is 0.02L/g), and at 30° C., the frequency of inversion leaching is often used with reference to the prior art. parameters, the same below) after 0.5h, the mixed solution was filtered to obtain leaching filtrate and leaching filter residue.

(2) Take 100mL of the leaching filtrate obtained in step (1) and 4g of magnesium iron hydrotalcite (that is, the liquid-solid ratio is 0.025L/g) in the reactor, and adjust the pH value of the mixed solution with 0.2mol/L sodium hydroxide solution to 5. After mechanical stirring at 150 r/min for 4 hours at 30°C (simultaneous adsorption, the same below), the mixture is filtered to obtain adsorption filtrate and adsorption filter residue.

(3) Take 2 g of the adsorption filter residue obtained in step (2) in the reactor, add 200 mL of 1 mol/L sodium hydroxide solution (that is, the liquid-solid ratio is 0.1 L/g), and at 30° C. at 300 r/min After 24 hours of mechanical stirring at the speed of rotation (desorption is carried out at the same time, the same below), the mixture is filtered to obtain desorption filtrate and desorption filter residue. The agent is returned to step (2) for use.

(4) Take 180 mL of the desorption filtrate obtained in step (3), fill it with nitrogen until the dissolved oxygen concentration (DO) is less than 2%, add a certain amount of FeCl ₂ ·4H ₂ O to make the Fe/P molar ratio 1.5, and use 0.2 mol/L hydrochloric acid solution and 0.2 mol/L sodium hydroxide solution adjust the pH value between 6-8. Mechanical stirring was carried out at a rotational speed of 100 r/min and the reaction was carried out, the reaction temperature was 30° C., the reaction time was 96 h, and nitrogen was continuously introduced into the reaction process. After the reaction is completed, filter to obtain filtrate and filter residue.

(5) The filter residue obtained in the step (4) was washed with clean water for 3 times, then washed with 98% ethanol for 3 times, and after being vacuum-dried at 30° C. for 6 to 8 hours, 0.57 g of cyanite product was obtained, and the yield of phosphorus was 78.2% (calculated based on the phosphorus content in the desorption filtrate, the same below).

The composition analysis of the leaching filtrate obtained in step (1) shows that the phosphorus concentration in the leaching filtrate is 2.49 g/L, and the phosphorus leaching rate is 95.8%.

Component analysis of the adsorption filtrate obtained in step (2) shows that the phosphorus concentration in the adsorption filtrate is 0.18 g/L, and the phosphorus adsorption rate is 88.5%.

Component analysis of the desorption filtrate obtained in step (3) shows that the phosphorus concentration in the desorption filtrate is 0.50 g/L, and the phosphorus desorption rate is 95.8%.

Example 2

A method for recovering blue iron ore from sludge incineration ash, and the treatment object is the sludge incineration ash of a sewage treatment plant. X-ray fluorescence spectroscopy (XRF) showed that the phosphorus content of the sludge incineration ash was 5.2 wt%. Recover phosphorus from the sludge incineration ash to prepare blue iron ore, which specifically includes the following steps:

(1) Mix and heat 100g of sludge incineration ash with 2L of hydrochloric acid solution (0.3mol/L) (that is, the liquid-solid ratio is 0.02L/g), and after inversion and leaching at 55°C for 0.5h, filter the mixture to obtain the leaching filtrate and leaching filter residues.

(2) Take 150mL of the leaching solution obtained in step (1), 6g of magnesium iron hydrotalcite (that is, the liquid-solid ratio is 0.025L/g) in the reactor, and adjust the pH value of the mixed solution to 5 with 0.2mol/L sodium hydroxide solution , after mechanical stirring at 150r/min for 4 hours at 30°C, the mixture was filtered to obtain adsorption filtrate and adsorption filter residue.

(3) Take 4 g of the adsorption filter residue obtained in step (2) in the reactor, add 400 mL of 1 mol/L sodium hydroxide solution (that is, the liquid-solid ratio is 0.1 L/g), and at 30° C. at 300 r/min After 24 hours of mechanical stirring at the rotational speed, the mixture was filtered to obtain desorption filtrate and desorption filter residue. The desorption filter residue was washed with deionized water, calcined at 450 ° C for 3 hours for regeneration, and then returned to step (2) as an adsorbent for use. .

(4) Take 326 mL of the desorption filtrate obtained in step (3), fill with nitrogen until DO (dissolved oxygen content)) < 2%, add a certain amount of FeCl ₂ ·4H ₂ O to make the Fe/P molar ratio 1.5, use 0.2mol/L hydrochloric acid solution and 0.2mol/L sodium hydroxide solution adjust the pH value between 6-8. The reaction was carried out at the same time with mechanical stirring at a rotational speed of 100 r/min, the reaction temperature was 30° C., the reaction time was 48 h, and nitrogen was continuously introduced into the reaction process. After the reaction is completed, filter to obtain filtrate and filter residue.

(5) The filter residue obtained in the step (4) was rinsed 3 times with clean water and then rinsed 3 times with 98% ethanol. After vacuum drying at 30° C. for 6 to 8 hours, 0.93 g of cyanite product was obtained, and the yield of phosphorus was 76.6%.

The composition analysis of the leaching filtrate obtained in step (1) shows that the phosphorus concentration in the leaching filtrate is 2.58 g/L, and the phosphorus leaching rate is 99.2%.

Component analysis of the adsorption filtrate obtained in step (2) shows that the phosphorus concentration in the adsorption filtrate is 0.23 g/L, and the phosphorus adsorption rate is 90.0%.

Component analysis of the desorption filtrate obtained in step (3) shows that the phosphorus concentration in the desorption filtrate is 0.46 g/L, and the phosphorus desorption rate is 84.5%.

Example 3

A method for recovering blue iron ore from sludge incineration ash, and the treatment object is the sludge incineration ash of a sewage treatment plant. X-ray fluorescence spectroscopy (XRF) showed that the phosphorus content of the sludge incineration ash was 5.3 wt%. Recover phosphorus from the sludge incineration ash to prepare blue iron ore, which specifically includes the following steps:

(1) Mix and heat 100 g of sludge incineration ash with 1 L of hydrochloric acid solution (0.3 mol/L) (that is, the liquid-solid ratio is 0.01 L/g), and after inverting and leaching at 55°C for 2 hours, the mixed solution is filtered to obtain the leaching filtrate and Leach filter residue.

(2) take 250mL of the leaching solution obtained in step (1), 10g of magnesium iron hydrotalcite (that is, the liquid-solid ratio is 0.025L/g) in the reactor, and adjust the pH value of the mixed solution to 6 with 0.2mol/L sodium hydroxide solution , after mechanical stirring at 250r/min for 6h at 35°C, the mixture was filtered to obtain adsorption filtrate and adsorption filter residue.

(3) Take 4 g of the adsorption filter residue obtained in step (2) in the reactor, add 800 mL of 1 mol/L sodium hydroxide solution (that is, the liquid-solid ratio is 0.2 L/g), and at 35° C. at 350 r/min After 36 hours of mechanical stirring at the rotational speed, the mixture was filtered to obtain desorption filtrate and desorption filter residue. The desorption filter residue was washed with deionized water, calcined at 300 °C for 3 hours for regeneration, and then returned to step (2) as an adsorbent for use. .

(4) Take 420 mL of the desorption filtrate obtained in step (3), fill it with nitrogen until DO (dissolved oxygen content)) <2%, add a certain amount of FeCl ₂ ·4H ₂ O to make the Fe/P molar ratio 1.6, use 0.2mol/L hydrochloric acid solution and 0.2mol/L sodium hydroxide solution adjust the pH value between 6-8. The reaction was carried out at the same time with mechanical stirring at a rotational speed of 100 r/min, the reaction temperature was 35° C., the reaction time was 96 h, and nitrogen was continuously introduced into the reaction process. After the reaction is completed, filter to obtain filtrate and filter residue.

(5) The filter residue obtained in the step (4) was rinsed 3 times with clean water and then rinsed 3 times with 98% ethanol, and after being vacuum-dried at 30° C. for 6 to 8 hours, 1.28 g of cyanite product was obtained, and the yield of phosphorus was 78.4%.

The composition analysis of the leaching filtrate obtained in step (1) shows that the phosphorus concentration in the leaching filtrate is 4.86 g/L, and the phosphorus leaching rate is 91.7%.

Component analysis of the adsorption filtrate obtained in step (2) shows that the phosphorus concentration in the adsorption filtrate is 0.17 g/L, and the phosphorus adsorption rate is 96.0%.

Component analysis of the desorption filtrate obtained in step (3) shows that the phosphorus concentration in the desorption filtrate is 0.48 g/L, and the phosphorus desorption rate is 82.3%.

Example 4

A method for recovering blue iron ore from sludge incineration ash, and the treatment object is the sludge incineration ash of a sewage treatment plant. X-ray fluorescence spectroscopy (XRF) showed that the phosphorus content of the sludge incineration ash was 5.3%. Recover phosphorus from the sludge incineration ash to prepare blue iron ore, which specifically includes the following steps:

(1) Mix and heat 100 g of sludge incineration ash with 1 L of nitric acid solution (0.6 mol/L) (that is, the liquid-solid ratio is 0.02 L/g), and after inverting and leaching at 25 ° C for 2 hours, the mixed solution is filtered to obtain the leaching filtrate and Leach filter residue.

(2) Take 250 mL of the leaching solution obtained in step (1) and 5 g of magnesium-aluminum hydrotalcite (that is, the liquid-solid ratio is 0.05 L/g) in the reactor, and adjust the pH value of the mixed solution with 0.2 mol/L sodium hydroxide solution to 7. After mechanical stirring at 300r/min for 3 hours at 25°C, filter the mixture to obtain adsorption filtrate and adsorption filter residue.

(3) Take 4 g of the adsorption filter residue obtained in step (2) in the reactor, add 800 mL of 1 mol/L sodium hydroxide solution (that is, the liquid-solid ratio is 0.2 L/g), and at 25 ° C with 450 r/min After 12 hours of mechanical stirring at the rotational speed, the mixture was filtered to obtain desorption filtrate and desorption filter residue. The desorption filter residue was washed with deionized water, calcined at 350 ° C for 2.5 hours for regeneration, and then returned to step (2) as an adsorbent for use.

(4) Take 460 mL of the desorption filtrate obtained in step (3), fill with nitrogen until DO (dissolved oxygen content)) <2%, add a certain amount of FeSO ₄ ·7H ₂ O to make the Fe/P molar ratio 1.6, use 0.2mol/L hydrochloric acid solution and 0.2mol/L sodium hydroxide solution adjust the pH value between 6-8. The reaction was carried out at the same time with mechanical stirring at a rotational speed of 100 r/min, the reaction temperature was 25° C., the reaction time was 48 h, and nitrogen was continuously introduced into the reaction process. After the reaction is completed, filter to obtain filtrate and filter residue.

(5) The filter residue obtained in step (4) is washed with clean water for 3 times, then washed with 98% ethanol for 3 times, and vacuum-dried at 25° C. for 8 hours to obtain a blue iron ore product.

Example 5

A method for recovering blue iron ore from sludge incineration ash, and the treatment object is the sludge incineration ash of a sewage treatment plant. X-ray fluorescence spectroscopy (XRF) showed that the phosphorus content of the sludge incineration ash was 5.3%. Recover phosphorus from the sludge incineration ash to prepare blue iron ore, which specifically includes the following steps:

(1) Mix and heat 100g of sludge incineration ash with 1L of sulfuric acid solution (0.3mol/L) (that is, the liquid-solid ratio is 0.02L/g), and after leaching at 35°C for 2 hours, filter the mixture to obtain the leaching filtrate and Leach filter residue.

(2) Take 250mL of the leaching solution obtained in step (1) and 5g of zinc-aluminum hydrotalcite (that is, the liquid-solid ratio is 0.05L/g) in the reactor, and adjust the pH value of the mixed solution with 0.2mol/L sodium hydroxide solution to 7. After mechanical stirring at 300r/min for 3 hours at 35°C, filter the mixture to obtain adsorption filtrate and adsorption filter residue.

(3) Take 4 g of the adsorption filter residue obtained in step (2) in the reactor, add 800 mL of 1 mol/L sodium hydroxide solution (that is, the liquid-solid ratio is 0.2 L/g), at 35 ° C with 450 r/min After 12 hours of mechanical stirring at the rotational speed, the mixture was filtered to obtain desorption filtrate and desorption filter residue. The desorption filter residue was washed with deionized water, calcined at 300 ° C for 3.5 hours for regeneration, and then returned to step (2) as an adsorbent for regeneration. use.

(4) Take 460 mL of the desorption filtrate obtained in step (3), fill it with nitrogen until DO (dissolved oxygen content)) <2%, add a certain amount of FeSO ₄ to make the Fe/P molar ratio 1.6, use 0.2 mol/L Hydrochloric acid solution and 0.2mol/L sodium hydroxide solution adjust the pH value between 6-8. The reaction was carried out simultaneously with mechanical stirring at a rotational speed of 100 r/min, the reaction temperature was 35° C., the reaction time was 48 h, and nitrogen was continuously introduced into the reaction process. After the reaction is completed, filter to obtain filtrate and filter residue.

(5) The filter residue obtained in step (4) is washed with clean water for 3 times, then washed with 98% ethanol for 3 times, and vacuum-dried at 35° C. for 6 hours to obtain a blue iron ore product.

Example 6

A method for recycling blue iron ore from sludge incineration ash, except that what is adopted in step (1) is citric acid solution, what is adopted in step (2) is magnesium-manganese hydrotalcite, and what is added in step (4) is FeCl Except for ₂ , the rest are the same as in Example 1.

Example 7

A method for recovering blue iron ore from sludge incineration ash, except that what is adopted in step (1) is oxalic acid solution, and what is adopted in step (2) is zinc-iron hydrotalcite, all the other are the same as in Example 1.

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

Claims (10)

1. A method for recovering blue iron ore from sludge incineration ash, it is characterized in that, described method comprises the following steps:

   (1) leaching of sludge incineration ash: the sludge incineration ash is mixed with acid solution and heated to carry out the leaching of phosphorus, and then the leaching filtrate and the leaching filter residue are obtained by filtration and separation;

   (2) adsorption of leaching filtrate: adjust the pH value of leaching filtrate with alkali solution, then add adsorbent to carry out phosphorus adsorption, and then filter and separate to obtain adsorption filtrate and adsorption filter residue;

   (3) Desorption of the adsorption filter residue: the adsorption filter residue is mixed with the lye and the phosphorus is desorbed, and then the desorption filtrate and the desorption filter residue are obtained by filtration and separation;

   (4) Preparation of blue iron ore: in an anaerobic environment, add ferrous ions to the desorption filtrate, and adjust the pH value of the desorption filtrate to react, and then filter and separate to obtain a filter residue and a filtrate, and the filter residue is washed and dried That is to get blue iron ore.
2. A kind of method that reclaims blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (1), described acid solution is mineral acid solution or organic acid solution, and described mineral acid The solution is selected from one or more of sulfuric acid solution, hydrochloric acid solution or nitric acid solution, and the organic acid solution is selected from one or more of citric acid solution or oxalic acid solution.
3. A kind of method for reclaiming blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (1), the liquid-solid ratio of acid solution and sludge incineration ash is 0.01～0.02L/g , the leaching temperature is 25～55℃, and the leaching time is 0.5～2h.
4. A kind of method of reclaiming blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (2), described adsorbent is hydrotalcite; Described lye is sodium hydroxide aqueous solution.
5. A kind of method of reclaiming blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (2), adjust the pH value of leaching filtrate to 5～7, leaching filtrate and adsorbent liquid The solid ratio is 0.025～0.05L/g, the adsorption temperature is 25～35℃, and the adsorption time is 3～8h;

   Stirring is carried out at the same time of adsorption, the stirring speed is 150～300r/min, and the stirring time is 3～8h.
6. A kind of method that reclaims blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (3), described lye is sodium hydroxide aqueous solution;

   The liquid-solid ratio of the alkali solution to the adsorption filter residue is 0.1～0.2L/g, the desorption temperature is 25～35℃, and the desorption time is 12～36h;

   While desorption is carried out, the stirring speed is 300～450r/min, and the stirring time is 12～36h.
7. A method for recovering blue iron ore from sludge incineration ash according to claim 1, characterized in that, in step (3), after the desorption filter residue is washed with deionized water, calcined at 300～450 ℃ for 2.5 ~3.5h for regeneration, and then returned to step (2) for use as an adsorbent.
8. A kind of method that reclaims blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (4), described ferrous ion comes from the crystal hydration of ferrous chloride, ferrous chloride one or more of ferrous sulfate, ferrous sulfate or crystalline hydrate of ferrous sulfate;

   The pH of the desorption filtrate was adjusted with sodium hydroxide solution and hydrochloric acid solution.
9. A kind of method of reclaiming blue iron ore from sludge incineration ash according to claim 1, is characterized in that, in step (4), the added molar ratio of ferrous ion and phosphorus is 1.5～1.6, adjusts desorption filtrate The pH value is 6～8, the temperature of reaction is 25～35 ℃, and the time of reaction is 48～96h;

   During the reaction, stirring is performed, the stirring speed is 100-150 r/min, and the stirring time is 48-96 h.
10. A kind of method for reclaiming blue iron ore from sludge incineration ash according to claim 1, it is characterized in that, in step (4), after filter residue is cleaned successively with deionized water and ethanol, at 25～35 ℃ Vacuum dry for 6-8h.

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