A method for recovering phosphorus from acetylene chemical industry phosphorus-containing sludge to prepare vivianite

Abstract

The application discloses a method for preparing vivianite by recovering phosphorus from acetylene chemical phosphorus-containing sludge, which comprises the following steps: firstly, drying, crushing and screening the acetylene chemical phosphorus-containing sludge to obtain a powder, mixing the powder with hydrochloric acid to perform acid leaching and dissolve out phosphorus, and performing solid-liquid separation to obtain a phosphorus-containing leaching solution; adding alkali to adjust the pH to strong alkalinity to precipitate and remove impurities such as iron, adjusting the supernatant to neutral after centrifugal impurity removal, adding EDTA to complex and shield residual impurities, and obtaining a high-purity iron-free phosphorus-containing solution; taking the solution as a phosphorus source, adding ferrous chloride as an iron source, adding ascorbic acid, constructing an anaerobic reduction environment by passing nitrogen, and performing sealed stirring reaction and standing aging, and then performing solid-liquid separation and drying to obtain a vivianite product. The product has high purity, good crystallinity and uniform morphology, can be used as a lithium iron phosphate precursor, realizes reduction and harmless high-value conversion of phosphorus-containing solid waste, and provides a feasible and efficient path for resource utilization of acetylene chemical phosphorus-containing solid waste and low-cost green preparation of new energy materials.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization and phosphorus recovery technology, and in particular to a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare lapis lazuli. Background Technology

[0002] With the continuous expansion of my country's calcium carbide acetylene-based polyvinyl chloride (PVC) industry, the acetylene purification process generates a large amount of high-concentration phosphorus-containing wastewater. After deep treatment by Fenton oxidation, this wastewater produces a large amount of phosphorus-containing sludge as a byproduct. This sludge has a complex composition, is rich in bound phosphates, and also contains small amounts of heavy metals, organic impurities, and trace amounts of primary metal ions, classifying it as hazardous solid waste.

[0003] Currently, most companies dispose of this type of sludge by entrusting landfill or incineration, which is not only costly but also poses a risk of soil and groundwater pollution caused by leaching of phosphates and heavy metals. At the same time, a large amount of scarce phosphorus resources in the sludge are directly discarded, resulting in serious waste of resources.

[0004] Against the backdrop of increasingly depleted global phosphate rock resources and the continuous enhancement of the strategic value of phosphate resources, recovering phosphorus from industrial phosphorus-containing solid waste and transforming it into high-value-added products has become an important direction for developing a circular economy and ensuring resource security.

[0005] Phosphorus-containing sludge from acetylene chemical production is rich in phosphorus resources and has extremely high recycling value, but existing technologies for preparing lapis lazuli from sludge have a core shortcoming:

[0006] Traditional processes directly utilize sludge leachate to synthesize products, failing to completely remove primary iron impurities from the sludge. Primary iron has problems such as unstable valence state, impurity doping, and uncontrollable proportions, which can easily trigger side reactions and generate impurity phases such as iron phosphate and iron hydroxide, severely reducing the purity, crystallinity, and stability of lapis lazuli products.

[0007] Meanwhile, conventional acid leaching process parameters lack targeted optimization, resulting in unstable phosphorus leaching efficiency, incomplete removal of impurities, and the final recovered products are mostly low-grade mixtures with extremely low added value, which cannot meet the application standards of new energy materials or high-end slow-release fertilizers.

[0008] Blue iron ore It is a precursor for preparing lithium iron phosphate, the cathode material for lithium-ion batteries. The purity and crystal integrity of the raw materials directly determine the core performance of the battery, such as cycle life and energy density.

[0009] Currently, there are reports on technologies for recovering phosphorus from municipal or industrial sludge to prepare lapis lazuli, but these technologies generally rely on the primary iron source in the sludge. They suffer from fatal flaws such as severe impurity interference, uncontrollable iron-phosphorus ratio, low product purity, and numerous crystal defects. The prepared lapis lazuli has high impurity content and unstable quality, which completely fails to meet the stringent access standards for new energy battery materials. The process controllability and industrialization value are extremely low. There is currently no high-quality preparation process for new energy-grade materials that "completely removes primary impurity iron + precisely matches external iron" for phosphorus-containing sludge from acetylene chemical plants.

[0010] Therefore, in order to solve the above-mentioned technical problems, a phosphorus-containing sludge resource utilization technology that can completely avoid the interference of primary iron impurities, achieve product purity that meets the new energy level, and has stable and easily scaled-up process is provided. This technology is of great practical significance for promoting the green transformation of the calcium carbide PVC industry, realizing the high-value transformation of solid waste into high-end new energy materials, and reducing the production cost of new energy materials. Summary of the Invention

[0011] In view of this, the present invention provides a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare lapis lazuli. Through core innovative processes such as optimized acid leaching, two-stage deep iron and impurity removal purification, and precise external iron control and directional crystallization, the method completely solves the industry pain points of traditional processes, such as interference from primary iron impurities, low product purity, and unstable quality, and achieves efficient conversion of hazardous phosphorus-containing solid waste into high-purity, high-value-added lapis lazuli products.

[0012] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0013] A method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite includes the following steps:

[0014] (1) Sludge pretreatment: The phosphorus-containing sludge from acetylene chemical industry is dried, crushed, and sieved to obtain uniform sludge powder;

[0015] (2) Hydrochloric acid leaching for phosphorus extraction: The sludge powder and hydrochloric acid solution are mixed at a liquid-solid ratio and stirred at a constant temperature to carry out the acid leaching reaction, so that the bound phosphorus in the sludge is fully dissolved.

[0016] After the reaction was completed, the solid and liquid were separated, and the supernatant was collected to obtain a phosphorus-containing leachate;

[0017] (3) Purification of leachate to remove iron and impurities: Add alkaline solution to phosphorus-containing leachate to adjust pH to strong alkalinity, thoroughly precipitate and remove primary iron and other impurity metal ions from leachate, centrifuge to remove hydroxide precipitate, adjust pH of supernatant to neutral, add EDTA complexing agent and stir until completely dissolved, shield residual trace impurity ions, and obtain iron-free high-purity purified phosphorus-containing solution.

[0018] (4) Directed synthesis of blue iron ore: using purified iron-free phosphorus-containing liquid as phosphorus source and ferrous chloride as iron source, ascorbic acid and ferrous chloride are added to the system in sequence, and high-purity nitrogen is introduced to construct an anaerobic environment. After sealing, the reaction is stirred and allowed to stand for aging. After solid-liquid separation, the solid is dried to obtain blue iron ore product.

[0019] Preferably, in step (1), the sludge drying temperature is 60~80℃, and the particle size after sieving is 100~200 mesh.

[0020] Preferably, in step (2), the concentration of hydrochloric acid solution is 0.5~1.5 mol / L, the liquid-solid ratio is 20:1~80:1mL / g, the acid leaching reaction time is 1~6 h, and the reaction is carried out at room temperature.

[0021] Preferably, in step (3), sodium hydroxide solution is used to adjust the pH, first adjusting it to strong alkalinity to completely remove primary iron and metallic impurities, and then adjusting it back to neutral.

[0022] Preferably, in step (3), the final concentration of EDTA in the system is 5~25 mmol / L.

[0023] Preferably, in step (3), the final concentration of EDTA in the system is 20 mmol / L.

[0024] Preferably, in step (4), the amount of exogenous ferrous chloride added is based on an iron-phosphorus molar ratio of 1.5~1.8:1, the amount of ascorbic acid is 10~15 g / L, the nitrogen purging time is 2~5 min, and the settling time is 3~6 h.

[0025] Preferably, in step (4), the iron-phosphorus molar ratio is 1.5~1.8:1, and the standing time is 5~8 h.

[0026] Preferably, in step (4), the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000 r / min and a centrifugation time of 5 min, and the solid drying method is freeze drying.

[0027] The present invention achieves the following technical effects compared to the prior art:

[0028] This invention addresses the treatment of phosphorus-containing sludge from the acetylene chemical industry in the calcium carbide-based PVC production process, and offers significant advantages over existing technologies:

[0029] First, the process concept is unique. It adopts a new approach of "first shielding the original iron and metal impurities in the sludge and then precisely adding ferrous iron from the outside". Combined with two-stage deep purification of strong alkali precipitation and EDTA complexation, it avoids the formation of iron phosphate and iron oxide impurities from the source. The resulting blue iron ore crystal phase is relatively pure and has high crystallinity. It completely solves the problems of impurity interference and unstable product quality in traditional processes, and the product purity is higher.

[0030] Secondly, it has achieved efficient recovery of phosphorus and full utilization of solid waste components. The hydrochloric acid leaching process has been optimized for phosphorus-containing sludge in acetylene chemical industry, which can efficiently dissociate bound phosphorus and achieve a higher phosphorus leaching rate. The residue after acid leaching has fewer impurities and can be further processed into building materials and adsorbents, realizing the tiered resource utilization and harmless disposal of phosphorus-containing hazardous waste.

[0031] Third, the process parameters are highly controllable, which can realize the high value of the product. This invention uses impurity-free purified phosphorus liquid as raw material. By precisely controlling the iron-phosphorus ratio and anaerobic reduction environment from the outside, it can directionally synthesize high-purity blue iron ore with uniform morphology and few crystal defects, which fully meets the stringent index requirements of lithium iron phosphate precursor for lithium batteries and greatly improves the economic value of solid waste resource utilization.

[0032] Fourth, the process conditions are mild and easy to promote industrially. The entire process of this invention adopts normal temperature and pressure reaction, the required equipment is simple, the reagent cost is low, there is no secondary pollution, the operation process is simple, and it can be implemented on a large scale. It provides a mature and feasible technical solution for the high-value treatment of phosphorus-containing hazardous waste in the calcium carbide PVC industry. Attached Figure Description

[0033] Figure 1 XRD pattern of vivianite product prepared according to the present invention;

[0034] Figure 2 This is a bar chart showing the effect of EDTA dosage on phosphorus concentration in the leachate in this invention.

[0035] Figure 3 Multi-scale SEM morphology images of the finished vivianite product prepared for this invention;

[0036] Figure 4 EDS energy spectrum of the finished blue iron ore product prepared according to the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite, comprising the following steps:

[0039] (1) Sludge pretreatment: The phosphorus-containing sludge from acetylene chemical industry is dried, crushed, and sieved to obtain uniform sludge powder;

[0040] (2) Hydrochloric acid leaching for phosphorus extraction: The sludge powder and hydrochloric acid solution are mixed at a liquid-solid ratio and stirred at a constant temperature to carry out the acid leaching reaction, so that the bound phosphorus in the sludge is fully dissolved.

[0041] After the reaction was completed, the solid and liquid were separated, and the supernatant was collected to obtain a phosphorus-containing leachate;

[0042] (3) Purification of leachate to remove iron and impurities: Add alkaline solution to phosphorus-containing leachate to adjust pH to strong alkalinity, thoroughly precipitate and remove primary iron and other impurity metal ions from leachate, centrifuge to remove hydroxide precipitate, adjust pH of supernatant to neutral, add EDTA complexing agent and stir until completely dissolved, shield residual trace impurity ions, and obtain iron-free high-purity purified phosphorus-containing solution.

[0043] (4) Directed synthesis of blue iron ore: using purified iron-free phosphorus-containing liquid as phosphorus source and ferrous chloride as iron source, ascorbic acid and ferrous chloride are added to the system in sequence, and high-purity nitrogen is introduced to construct an anaerobic environment. After sealing, the reaction is stirred and allowed to stand for aging. After solid-liquid separation, the solid is dried to obtain blue iron ore product.

[0044] In step (1), the sludge drying temperature is 60~80℃, and the particle size after sieving is 100~200 mesh.

[0045] In step (2), the concentration of hydrochloric acid solution is 0.5~1.5 mol / L, the liquid-solid ratio is 20:1~80:1 mL / g, the acid leaching reaction time is 1~6 h, and the reaction is carried out at room temperature.

[0046] In step (3), sodium hydroxide solution is used to adjust the pH. First, it is adjusted to strong alkalinity to completely remove primary iron and metal impurities, and then it is adjusted back to neutral.

[0047] In step (3), the final concentration of EDTA in the system is 5~25 mmol / L.

[0048] In step (3), the final concentration of EDTA in the system is 20 mmol / L.

[0049] In step (4), the amount of exogenous ferrous chloride added is based on an iron-phosphorus molar ratio of 1.5~1.8:1, the amount of ascorbic acid is 10~15 g / L, the nitrogen purging time is 2~5 min, and the settling time is 3~6 h.

[0050] In step (4), the iron-phosphorus molar ratio is 1.5~1.8:1, and the standing time is 5~8 h.

[0051] In step (4), the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000 r / min and a centrifugation time of 5 min. The solid drying method is freeze drying.

[0052] The reagents and instruments used in the following examples are all commercially available conventional products. Unless otherwise specified, they are performed according to conventional experimental conditions in the field.

[0053] Example 1:

[0054] This embodiment discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite. The specific steps are as follows:

[0055] (1) Sludge pretreatment: Phosphorus-containing sludge from an acetylene chemical enterprise in Xinjiang was taken, dried in an oven at 60℃ to constant weight, and then crushed and passed through a 100-mesh sieve to obtain sludge powder;

[0056] Tests showed that the sludge was rich in phosphorus and did not exhibit high iron enrichment, thus possessing excellent phosphorus recovery value.

[0057] (2) Hydrochloric acid leaching for phosphorus extraction: Weigh 1 g of sludge powder and place it in a beaker. Add 80 mL of 1 mol / L hydrochloric acid solution (liquid-solid ratio 80:1 mL / g) and stir magnetically at 300 r / min for 6 h at room temperature.

[0058] After the reaction is complete, centrifuge at 8000 r / min for 5 min and take the supernatant as the phosphorus-containing leachate.

[0059] The phosphorus leaching rate was determined to be 78.03% under these conditions.

[0060] (3) Deep iron and impurity removal and purification of leachate: Add 10 mol / L sodium hydroxide solution to the above phosphorus-containing leachate, adjust the pH to 14.0, stir for 30 min and then centrifuge to completely remove the original iron and various metal hydroxide precipitates from the sludge;

[0061] Adjust the pH of the supernatant to 7.0 with dilute hydrochloric acid, add 0.117 g EDTA (final system concentration 20 mmol / L), and stir until completely dissolved to deeply shield residual trace impurities, thus obtaining iron-free, high-purity purified phosphorus-containing solution.

[0062] (4) Directed synthesis of blue iron ore: Using purified iron-free phosphorus-containing liquid as the phosphorus source, 1 g of ascorbic acid was added and stirred to dissolve. Ferrous chloride was added precisely at an iron-phosphorus molar ratio of 1.5:1. Solids are the sole source of iron;

[0063] After complete dissolution, transfer to a serum bottle, purge with high-purity nitrogen for 2 min, quickly tighten the cap to seal and create an anaerobic environment, stir magnetically for 30 min and then let stand to precipitate for 6 h.

[0064] After the reaction was completed, the sample was centrifuged at 8000 r / min for 5 min, the solid precipitate was collected, and the product was obtained by freeze drying.

[0065] XRD characterization revealed that the main phase of the product was ferrous phosphate octahydrate. It is highly compatible with the standard card, has no impurity phase peaks caused by any primary iron impurities, and has excellent crystallinity;

[0066] SEM observation showed that the product was a plate-shaped crystal with uniform morphology and complete structure, with a lateral size of up to several micrometers. The purity and uniformity of the product were significantly better than those of products processed by traditional methods.

[0067] Example 2:

[0068] This embodiment discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite. The specific steps are as follows:

[0069] (1) Sludge pretreatment: Phosphorus-containing sludge from an acetylene chemical enterprise in Xinjiang was taken, dried in an oven at 60℃ to constant weight, and then crushed and passed through a 100-mesh sieve to obtain sludge powder;

[0070] Tests showed that the sludge was rich in phosphorus and did not exhibit high iron enrichment, thus possessing excellent phosphorus recovery value.

[0071] (2) Hydrochloric acid leaching for phosphorus extraction: Weigh 1 g of sludge powder and place it in a beaker. Add 80 mL of 0.5 mol / L hydrochloric acid solution (liquid-solid ratio 80:1 mL / g) and stir magnetically at 300 r / min for 6 h at room temperature.

[0072] After the reaction is complete, centrifuge at 8000 r / min for 5 min and take the supernatant as the phosphorus-containing leachate.

[0073] The phosphorus leaching rate was determined to be 72.15% under these conditions.

[0074] (3) Deep iron and impurity removal and purification of leachate: Add 10 mol / L sodium hydroxide solution to the above phosphorus-containing leachate, adjust the pH to 14.0, stir for 30 min and then centrifuge to completely remove the original iron and various metal hydroxide precipitates from the sludge;

[0075] Adjust the pH of the supernatant to 7.0 with dilute hydrochloric acid, add 0.117 g EDTA (final system concentration 20 mmol / L), and stir until completely dissolved to deeply shield residual trace impurities, thus obtaining iron-free, high-purity purified phosphorus-containing solution.

[0076] (4) Directed synthesis of blue iron ore: Using purified iron-free phosphorus-containing liquid as the phosphorus source, 1 g of ascorbic acid was added and stirred to dissolve. Ferrous chloride was added precisely at an iron-phosphorus molar ratio of 1.5:1. Solids are the sole source of iron;

[0077] After complete dissolution, transfer to a serum bottle, purge with high-purity nitrogen for 2 min, quickly tighten the cap to seal and create an anaerobic environment, stir magnetically for 30 min and then let stand to precipitate for 8 h.

[0078] After the reaction was completed, the sample was centrifuged at 8000 r / min for 5 min, the solid precipitate was collected, and the product was obtained by freeze drying.

[0079] XRD characterization revealed that the main phase of the product was ferrous phosphate octahydrate. It closely matches the standard card, has no impurity peaks caused by any primary iron impurities, and has a crystallinity slightly lower than that of Example 1. However, the product quality is still far superior to that of products produced by traditional processes.

[0080] Example 3:

[0081] This embodiment discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite. The specific steps are as follows:

[0082] (1) Sludge pretreatment: Phosphorus-containing sludge from an acetylene chemical enterprise in Xinjiang was taken, dried in an oven at 60℃ to constant weight, and then crushed and passed through a 100-mesh sieve to obtain sludge powder;

[0083] Tests showed that the sludge was rich in phosphorus and did not exhibit high iron enrichment, thus possessing excellent phosphorus recovery value.

[0084] (2) Hydrochloric acid leaching for phosphorus extraction: Weigh 1 g of sludge powder and place it in a beaker. Add 80 mL of 1.5 mol / L hydrochloric acid solution (liquid-solid ratio 80:1 mL / g) and stir magnetically at 300 r / min for 6 h at room temperature.

[0085] After the reaction is complete, centrifuge at 8000 r / min for 5 min and take the supernatant as the phosphorus-containing leachate.

[0086] The phosphorus leaching rate was determined to be 70.28% under these conditions.

[0087] (3) Deep iron and impurity removal and purification of leachate: Add 10 mol / L sodium hydroxide solution to the above phosphorus-containing leachate, adjust the pH to 14.0, stir for 30 min and then centrifuge to completely remove the original iron and various metal hydroxide precipitates from the sludge;

[0088] Adjust the pH of the supernatant to 7.0 with dilute hydrochloric acid, add 0.117 g EDTA (final system concentration 20 mmol / L), and stir until completely dissolved to deeply shield residual trace impurities, thus obtaining iron-free, high-purity purified phosphorus-containing solution.

[0089] (4) Directed synthesis of blue iron ore: Using purified iron-free phosphorus-containing liquid as the phosphorus source, 1 g of ascorbic acid was added and stirred to dissolve. Ferrous chloride was added precisely at an iron-phosphorus molar ratio of 1.5:1. Solids are the sole source of iron;

[0090] After complete dissolution, transfer to a serum bottle, purge with high-purity nitrogen for 2 min, quickly tighten the cap to seal and create an anaerobic environment, stir magnetically for 30 min and then let stand to precipitate for 8 h.

[0091] After the reaction was completed, the sample was centrifuged at 8000 r / min for 5 min, the solid precipitate was collected, and the product was obtained by freeze drying.

[0092] XRD characterization revealed that the main phase of the product was ferrous phosphate octahydrate. The final blue iron ore product had a slightly higher impurity content and contained trace amounts of iron phosphate impurities.

[0093] Example 4:

[0094] This embodiment discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite. The specific steps are as follows:

[0095] (1) Sludge pretreatment: Phosphorus-containing sludge from an acetylene chemical enterprise in Xinjiang was taken, dried in an oven at 60℃ to constant weight, and then crushed and passed through a 100-mesh sieve to obtain sludge powder;

[0096] Tests showed that the sludge was rich in phosphorus and did not exhibit high iron enrichment, thus possessing excellent phosphorus recovery value.

[0097] (2) Hydrochloric acid leaching for phosphorus extraction: Weigh 1 g of sludge powder and place it in a beaker. Add 80 mL of 1 mol / L hydrochloric acid solution (liquid-solid ratio 40:1 mL / g) and stir magnetically at 300 r / min for 6 h at room temperature.

[0098] After the reaction is complete, centrifuge at 8000 r / min for 5 min and take the supernatant as the phosphorus-containing leachate.

[0099] The phosphorus leaching rate was determined to be 45.11% under these conditions.

[0100] (3) Deep iron and impurity removal and purification of leachate: Add 10 mol / L sodium hydroxide solution to the above phosphorus-containing leachate, adjust the pH to 14.0, stir for 30 min and then centrifuge to completely remove the original iron and various metal hydroxide precipitates from the sludge;

[0101] Adjust the pH of the supernatant to 7.0 with dilute hydrochloric acid, add 0.117 g EDTA (final system concentration 20 mmol / L), and stir until completely dissolved to deeply shield residual trace impurities, thus obtaining iron-free, high-purity purified phosphorus-containing solution.

[0102] (4) Directed synthesis of blue iron ore: Using purified iron-free phosphorus-containing liquid as the phosphorus source, 1 g of ascorbic acid was added and stirred to dissolve. Ferrous chloride was added precisely at an iron-phosphorus molar ratio of 1.5:1. Solids are the sole source of iron;

[0103] After complete dissolution, transfer to a serum bottle, purge with high-purity nitrogen for 2 min, quickly tighten the cap to seal and create an anaerobic environment, stir magnetically for 30 min and then let stand to precipitate for 6 h.

[0104] After the reaction was completed, the sample was centrifuged at 8000 r / min for 5 min, the solid precipitate was collected, and the product was obtained by freeze drying.

[0105] Example 5:

[0106] This embodiment discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite. The specific steps are as follows:

[0107] (1) Sludge pretreatment: Phosphorus-containing sludge from an acetylene chemical enterprise in Xinjiang was taken, dried in an oven at 60℃ to constant weight, and then crushed and passed through a 100-mesh sieve to obtain sludge powder;

[0108] Tests showed that the sludge was rich in phosphorus and did not exhibit high iron enrichment, thus possessing excellent phosphorus recovery value.

[0109] (2) Hydrochloric acid leaching for phosphorus extraction: Weigh 1 g of sludge powder and place it in a beaker. Add 80 mL of 1 mol / L hydrochloric acid solution (liquid-solid ratio 80:1 mL / g) and stir magnetically at 300 r / min for 4 h at room temperature.

[0110] After the reaction is complete, centrifuge at 8000 r / min for 5 min and take the supernatant as the phosphorus-containing leachate.

[0111] The phosphorus leaching rate was determined to be 52.36% under these conditions.

[0112] (3) Deep iron and impurity removal and purification of leachate: Add 10 mol / L sodium hydroxide solution to the above phosphorus-containing leachate, adjust the pH to 14.0, stir for 30 min and then centrifuge to completely remove the original iron and various metal hydroxide precipitates from the sludge;

[0113] Adjust the pH of the supernatant to 7.0 with dilute hydrochloric acid, add 0.117 g EDTA (final system concentration 20 mmol / L), and stir until completely dissolved to deeply shield residual trace impurities, thus obtaining iron-free, high-purity purified phosphorus-containing solution.

[0114] (4) Directed synthesis of blue iron ore: Using purified iron-free phosphorus-containing liquid as the phosphorus source, 1 g of ascorbic acid was added and stirred to dissolve. Ferrous chloride was added precisely at an iron-phosphorus molar ratio of 1.5:1. Solids are the sole source of iron;

[0115] After complete dissolution, transfer to a serum bottle, purge with high-purity nitrogen for 2 min, quickly tighten the cap to seal and create an anaerobic environment, stir magnetically for 30 min and then let stand to precipitate for 8 h.

[0116] After the reaction was completed, the sample was centrifuged at 8000 r / min for 5 min, the solid precipitate was collected, and the product was obtained by freeze drying.

[0117] Example 6:

[0118] This embodiment discloses a method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite. The specific steps are as follows:

[0119] (1) Sludge pretreatment: Phosphorus-containing sludge from an acetylene chemical enterprise in Xinjiang was taken, dried in an oven at 60℃ to constant weight, and then crushed and passed through a 100-mesh sieve to obtain sludge powder;

[0120] Tests showed that the sludge was rich in phosphorus and did not exhibit high iron enrichment, thus possessing excellent phosphorus recovery value.

[0121] (2) Hydrochloric acid leaching for phosphorus extraction: Weigh 1 g of sludge powder and place it in a beaker. Add 80 mL of 1 mol / L hydrochloric acid solution (liquid-solid ratio 80:1 mL / g) and stir magnetically at 300 r / min for 6 h at room temperature.

[0122] After the reaction is complete, centrifuge at 8000 r / min for 5 min and take the supernatant as the phosphorus-containing leachate.

[0123] The phosphorus leaching rate was determined to be 78.03% under these conditions.

[0124] (3) Deep iron and impurity removal and purification of leachate: Add 10 mol / L sodium hydroxide solution to the above phosphorus-containing leachate, adjust the pH to 14.0, stir for 30 min and then centrifuge to completely remove the original iron and various metal hydroxide precipitates from the sludge;

[0125] Adjust the pH of the supernatant to 7.0 with dilute hydrochloric acid, add 0.117 g EDTA (final system concentration 15 mmol / L), and stir until completely dissolved to deeply shield residual trace impurities, thus obtaining iron-free, high-purity purified phosphorus-containing solution.

[0126] (4) Directed synthesis of blue iron ore: Using purified iron-free phosphorus-containing liquid as the phosphorus source, 1 g of ascorbic acid was added and stirred to dissolve. Ferrous chloride was added precisely at an iron-phosphorus molar ratio of 1.5:1. Solids are the sole source of iron;

[0127] After complete dissolution, transfer to a serum bottle, purge with high-purity nitrogen for 2 min, quickly tighten the cap to seal and create an anaerobic environment, stir magnetically for 30 min and then let stand to precipitate for 8 h.

[0128] After the reaction was completed, the sample was centrifuged at 8000 r / min for 5 min, the solid precipitate was collected, and the product was obtained by freeze drying.

[0129] XRD characterization revealed that the main phase of the product was ferrous phosphate octahydrate. It is highly compatible with the standard card, has no impurity phase peaks caused by any primary iron impurities, and has excellent crystallinity;

[0130] SEM observation showed that the product was a plate-shaped crystal with uniform morphology and complete structure, with a lateral size of up to several micrometers. The purity and uniformity of the product were significantly better than those of products processed by traditional methods.

[0131] The peak intensity of a small number of impurity phases in the final product increased slightly, while the main phase remained lapis lazuli, and the overall performance met the requirements for use.

[0132] Comparative Example 1:

[0133] This comparative example is basically the same as Example 1, except that:

[0134] Step (3) omits the strong alkali iron removal and EDTA deep purification processes and directly uses the original leachate to synthesize blue iron ore, utilizing the primary iron in the sludge to participate in the reaction.

[0135] The results showed that the XRD patterns of products from traditional processes exhibited obvious iron hydroxide and iron phosphate impurity peaks, weak intensity of lapis lazuli characteristic peaks, poor crystallinity, extremely low product purity, and disordered morphology, which could not meet the requirements of high-end applications. This fully verified the superiority of the process of removing primary iron and precisely blending exogenous iron in this invention.

[0136] In summary, this invention, through its original core process of complete removal of primary iron and precise control of external iron, combined with an optimized acid leaching system and deep impurity removal technology, successfully achieves high-quality recovery of phosphorus resources from phosphorus-containing sludge in acetylene chemical industry. It fundamentally solves the technical bottlenecks of impurity interference and poor product quality in traditional processes. The process is stable, controllable, green, and efficient, and the purity and added value of the product are greatly improved, demonstrating strong technological innovation and promising prospects for industrial application.

[0137] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite, characterized in that, Includes the following steps: (1) Sludge pretreatment: The phosphorus-containing sludge from acetylene chemical industry is dried, crushed, and sieved to obtain uniform sludge powder; (2) Hydrochloric acid leaching for phosphorus extraction: The sludge powder and hydrochloric acid solution are mixed at a liquid-solid ratio and stirred at a constant temperature to carry out the acid leaching reaction, so that the bound phosphorus in the sludge is fully dissolved. After the reaction was completed, the solid and liquid were separated, and the supernatant was collected to obtain a phosphorus-containing leachate; (3) Purification of leachate to remove iron and impurities: Add alkaline solution to phosphorus-containing leachate to adjust pH to strong alkalinity, thoroughly precipitate and remove primary iron and other impurity metal ions from leachate, centrifuge to remove hydroxide precipitate, adjust pH of supernatant to neutral, add EDTA complexing agent and stir until completely dissolved, shield residual trace impurity ions, and obtain iron-free high-purity purified phosphorus-containing solution. (4) Directed synthesis of blue iron ore: using purified iron-free phosphorus-containing liquid as phosphorus source and ferrous chloride as iron source, ascorbic acid and ferrous chloride are added to the system in sequence, and high-purity nitrogen is introduced to construct an anaerobic environment. After sealing, the reaction is stirred and allowed to stand for aging. After solid-liquid separation, the solid is dried to obtain blue iron ore product.

2. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare vivianite according to claim 1, characterized in that, In step (1), the sludge drying temperature is 60~80℃, and the particle size after sieving is 100~200 mesh.

3. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare vivianite according to claim 1, characterized in that, In step (2), the concentration of hydrochloric acid solution is 0.5~1.5 mol / L, the liquid-solid ratio is 20:1~80:1 mL / g, the acid leaching reaction time is 1~6 h, and the reaction is carried out at room temperature.

4. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare vivianite according to claim 1, characterized in that, In step (3), sodium hydroxide solution is used to adjust the pH. First, it is adjusted to strong alkalinity to completely remove primary iron and metallic impurities, and then it is adjusted back to neutral.

5. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite according to claim 1, characterized in that, In step (3), the final concentration of EDTA in the system is 5~25 mmol / L.

6. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare vivianite according to claim 5, characterized in that, In step (3), the final concentration of EDTA in the system is 20 mmol / L.

7. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare vivianite according to claim 1, characterized in that, In step (4), the amount of exogenous ferrous chloride added is based on an iron-phosphorus molar ratio of 1.5~1.8:1, the amount of ascorbic acid is 10~15 g / L, the nitrogen purging time is 2~5 min, and the settling time is 3~6 h.

8. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical industry to prepare vivianite according to claim 1, characterized in that, In step (4), the iron-phosphorus molar ratio is 1.5~1.8:1, and the standing time is 5~8h.

9. The method for recovering phosphorus from phosphorus-containing sludge in acetylene chemical plants to prepare vivianite according to claim 1, characterized in that, In step (4), the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000 r / min and a centrifugation time of 5 min. The solid drying method is freeze drying.

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