Method for efficiently and synergistically purifying multiple metals in wet-process phosphoric acid

Abstract

The invention relates to a method for efficiently and synergistically purifying multiple metals in wet-process phosphoric acid, which comprises the following steps: (1) adding an inorganic sulfide accounting for 0.05-0.40% of the mass of wet-process phosphoric acid slurry into the wet-process phosphoric acid slurry, and reacting for 30-60 minutes at the temperature of 80-85 DEG C and the stirring speed of 100-200 r / min; (2) pumping the reacted slurry into a filter, adding an organic sulfide accounting for 0.05-0.20% of the mass of the wet-process phosphoric acid slurry at the front end of a pump, and reacting for 10-90 seconds under the conditions that the temperature is 70-80 DEG C and the rotating speed of the pump is 900-1500 r / min; and (3) filtering to obtain dilute phosphoric acid, and aging, concentrating and aging the dilute phosphoric acid to obtain the finished product concentrated phosphoric acid. The sulfide and dithiophosphate synergistic process is adopted, the reaction time with organic sulfide is shortened to the second level, the defect that in the prior art, the efficiency of a single cadmium removal agent is low is overcome, multi-metal ions such as arsenic, cadmium and copper are synchronously removed, the removal rate reaches up to 98% or above, and the cadmium removal treatment cost of per ton of phosphoric acid is greatly reduced.

Description

Technical Field

[0001] This invention relates to a method for efficient and synergistic purification of multiple metals in wet-process phosphoric acid, belonging to the field of wet-process phosphoric acid purification. Background Technology

[0002] Wet-process phosphoric acid is an important intermediate in the preparation of high-purity phosphate products and is widely used in pharmaceuticals, chemicals, and electronics. However, wet-process phosphoric acid contains various impurity ions, such as arsenic, cadmium, and copper, which seriously affect the purity and quality of the phosphoric acid. Currently, to address the problem of purifying arsenic, cadmium, and copper ions in wet-process phosphoric acid, most commonly sodium butadiene black reagent is used for cadmium removal, achieving an efficiency of over 90%. However, this requires a large dosage, the removal effect is unstable, and coexisting ions such as arsenic, copper, and iron ions can further affect the removal efficiency. Furthermore, traditional treatment methods often result in high phosphoric acid costs, reaching 150-200 yuan / ton, which is insufficient to meet the growing industrial demand.

[0003] With the development of technology, the demand for high-purity phosphoric acid is increasing, and the demand for industrial phosphoric acid and phosphates is constantly growing. To meet this demand, there is an urgent need to develop an efficient, low-cost, and widely applicable arsenic removal method to solve the problems of large amounts of arsenic removal agents, low arsenic removal efficiency, and high costs in wet-process phosphoric acid production. At the same time, the removal of other metal ions also needs to be considered to improve the overall purity and quality of phosphoric acid.

[0004] Therefore, developing a method to simultaneously and efficiently remove multiple metal ions such as arsenic, cadmium, and copper from wet-process phosphoric acid, thereby reducing processing costs and improving efficiency, has significant practical importance and application value. This will not only improve the purity and quality of phosphoric acid but also meet the growing industrial demand, providing a new direction for the development of wet-process phosphoric acid purification technology. Several invention patents already exist regarding solutions to the problem of removing arsenic, cadmium, and copper ions from wet-process phosphoric acid. For example: CN115893343A discloses a method for removing arsenic from wet-process phosphoric acid. This method involves adding a hydrocarbon-based dithiolated or trithiolated derivative to wet-process phosphoric acid under acidic conditions and reacting with stirring for 15-60 minutes. After standing, the mixture is filtered, and the filtrate is used to obtain the arsenic-removed phosphoric acid. This method utilizes dithiolated or trithiolated derivatives as the arsenic removal raw material, and can simultaneously remove other metals while removing arsenic. However, this method lacks improvements in expanding the adsorption range and stability of impurity ions in multi-metal mesoporous phosphate adsorbents.

[0005] CN117098722A discloses a method for recovering and utilizing residual acid in the wet purification process for producing phosphoric acid. The method includes: removing sulfur, fluorine, arsenic, and metals from the residual acid to be treated, obtaining pretreated acid; pre-neutralizing the pretreated acid, followed by purification, to obtain a purified liquid and precipitates containing iron, aluminum, and magnesium; and distilling the purified liquid to obtain industrial-grade phosphoric acid. This method can effectively recover and utilize phosphorus resources from the residual acid, and the obtained industrial-grade phosphoric acid can be used as a raw material to prepare battery-grade phosphates. However, this method lacks optimization of process parameters for desulfurization, defluorination, dearsenic removal, and demetallization in the process of removing sulfur, fluorine, arsenic, and metals from the residual acid to improve the removal efficiency and reduce the content of impurity ions.

[0006] The existing technology has the following drawbacks: 1. Currently, the most commonly used cadmium removal agent for purifying wet-process phosphoric acid is sodium butadiene black powder. Although the cadmium removal efficiency can reach more than 90%, the required amount of agent is large, the removal effect is unstable, and the coexisting arsenic and copper ions will affect the cadmium removal effect, resulting in the cost of treating phosphoric acid as high as 150-200 yuan / ton. 2. In the existing technology, there is a lack of a method that can simultaneously and efficiently remove multiple metal ions such as arsenic, cadmium, and copper from wet-process phosphoric acid, making it difficult to effectively improve the overall purity and quality of phosphoric acid; 3. In existing purification processes, the synergistic effect of sulfides and dithiophosphates is not fully utilized, and the synergistic effect of the two reagents is not fully exerted, resulting in unsatisfactory purification effect. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a wet process for purifying metal phosphates. This invention employs a synergistic process of sulfides and dithiophosphates to achieve the simultaneous removal of multiple metal ions such as arsenic, cadmium, and copper. It overcomes the low efficiency of single cadmium removal agents in existing technologies, achieving a removal rate of over 98% for metal ions such as arsenic, cadmium, and copper. This significantly improves purification efficiency, solves the problem of coexisting ions affecting cadmium removal in existing technologies, greatly reduces the cost per ton of phosphoric acid, and has good economic benefits. The reaction time with organic sulfides is shortened to the second level.

[0008] The conventional wet-process phosphoric acid production process is roughly divided into the following steps: phosphate rock pretreatment, phosphate rock decomposition (sulfuric acid and phosphate rock powder are stirred and reacted at 80-85℃ for 30-60 minutes to obtain wet-process acid slurry), filtration to obtain dilute phosphoric acid (pump speed is 900-1500 r / min, temperature is 70-80℃), dilute phosphoric acid aging, dilute phosphoric acid concentration, and concentrated phosphoric acid aging to obtain the finished concentrated phosphoric acid.

[0009] The present invention adopts the following technical solution: A method for efficient and synergistic purification of multiple metals in wet-process phosphoric acid, characterized by the following steps: (1) Add 0.05%-0.40% of inorganic sulfide by weight of wet phosphoric acid slurry to wet phosphoric acid slurry and react for 30-60 minutes at 80-85℃ and 100-200 r / min stirring rate; (2) Pump the slurry after reaction into a filter, add 0.05%-0.20% organic sulfide of wet phosphoric acid slurry at the front end of the pump, and react for 10-90 seconds at 70-80℃ and pump speed of 900-1500 r / min. (3) The dilute phosphoric acid is obtained by filtration. After aging, concentration and aging, the dilute phosphoric acid is used to obtain the finished concentrated phosphoric acid.

[0010] The inorganic sulfide is one or a mixture of two or more of sodium hydrosulfide, sodium sulfide, ferrous sulfide, and hydrogen sulfide. The amount of the inorganic sulfide added is 0.15%-0.20%.

[0011] The organic sulfide is one or a mixture of two or more of dialkyl dithiophosphate, dialkyl dithiophosphite, and dialkyl dithiophosphate, and the amount of organic sulfide added is 0.08%-0.10%.

[0012] The organic sulfide is one or a mixture of two or more of sodium dibutyl dithiophosphate, sodium dibutyl dithiophosphoric acid, dioctyl dithiophosphate, zinc dihexadecanophosphate, or calcium didodecyl dithiophosphate.

[0013] After adopting this solution, the arsenic content, cadmium content, and copper content in the finished concentrated phosphoric acid are ≤3ppm, ≤3ppm, and ≤1ppm, with a comprehensive metal removal rate of ≥98%.

[0014] Compared with existing technologies, this invention provides a method for efficient and synergistic purification of multiple metals in wet-process phosphoric acid, which has the following beneficial effects: 1. This invention employs a synergistic process of sulfide and dithiophosphate. Through the reaction of sulfide with copper and arsenic ions in phosphoric acid under strongly acidic conditions, copper sulfide and arsenic sulfide precipitates are generated. Then, dithiophosphate is added to react with cadmium in phosphoric acid to generate cadmium dithiophosphate precipitate. This achieves the simultaneous removal of multiple metal ions such as arsenic, cadmium, and copper, overcoming the shortcomings of low efficiency of single cadmium removal agents in existing technologies. 2. The synergistic process of this invention can thoroughly purify arsenic, cadmium, and copper ions in phosphoric acid, with a removal rate of over 98%, significantly improving purification efficiency and solving the problem of coexisting ions affecting cadmium removal efficiency in existing technologies; 3. The method of the present invention has a stable cadmium removal effect and is not affected by ions such as arsenic, copper, and iron, thus overcoming the shortcomings of the existing technology where the coexistence of multiple ions leads to unstable removal effect; 4. The processing method of the present invention significantly reduces the cost of phosphoric acid, with a processing fee of only about 50-70 yuan / ton, which significantly reduces the cost of traditional processing methods and has good economic benefits. Detailed Implementation

[0015] The present invention will be clearly and completely described below with reference to embodiments, so as to fully understand the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0016] Example 1: A wet-process phosphoric acid slurry with an arsenic content of 25 ppm, a cadmium content of 20 ppm, and a copper content of 40 ppm was prepared. 0.15% sodium hydrosulfide (by weight of the wet-process phosphoric acid slurry) was added, and the mixture was stirred at 85℃ and 200 r / min for 30 min. After the reaction, the slurry was pumped into a filter. 0.10% sodium dibutyldithiophosphate (by weight of the wet-process phosphoric acid slurry) was added to the front end of the pump, and the mixture was reacted at 70℃ and 1500 r / min for 10 s. After the reaction was complete, the mixture was filtered to obtain purified dilute phosphoric acid. The dilute phosphoric acid was then aged, concentrated, and aged again to obtain the final concentrated phosphoric acid. The purified dilute phosphoric acid was found to contain 0.08 ppm arsenic (99.68% removal rate), 0.32 ppm cadmium (98.40% removal rate), and 0.01 ppm copper (99.98% removal rate).

[0017] Example 2: A wet-process phosphoric acid slurry with an arsenic content of 20 ppm, a cadmium content of 15 ppm, and a copper content of 30 ppm was prepared. 0.05% sodium sulfide (by weight of the wet-process phosphoric acid slurry) was added, and the mixture was stirred at 80℃ and 100 r / min for 60 min. After the reaction, the slurry was pumped into a filter. 0.05% sodium dibutyldithiophosphate (by weight of the wet-process phosphoric acid slurry) was added to the front end of the pump. The mixture was reacted at 75℃ and 1000 r / min for 60 s. After the reaction was complete, the mixture was filtered to obtain purified dilute phosphoric acid. The dilute phosphoric acid was then aged, concentrated, and aged again to obtain the final concentrated phosphoric acid. The purified dilute phosphoric acid was found to contain 0.01 ppm arsenic (99.95% removal rate), 0.21 ppm cadmium (98.60% removal rate), and 0.01 ppm copper (99.97% removal rate).

[0018] Example 3: A wet-process phosphoric acid slurry with an arsenic content of 40 ppm, a cadmium content of 32 ppm, and a copper content of 65 ppm was prepared. 0.40% (by weight) of ferrous sulfide was added to the slurry, and the mixture was stirred at 82℃ and 150 r / min for 45 min. After the reaction, the slurry was pumped into a filter. 0.08% (by weight) of dioctyl dithiophosphoric acid was added to the front end of the pump, and the mixture was reacted at 73℃ and 1200 r / min for 30 s. After the reaction was complete, the mixture was filtered to obtain purified dilute phosphoric acid. The dilute phosphoric acid was then aged, concentrated, and aged again to obtain the final concentrated phosphoric acid. The purified dilute phosphoric acid was found to contain 0.04 ppm arsenic (99.90% removal rate), 0.11 ppm cadmium (99.66% removal rate), and 0.01 ppm copper (99.98% removal rate).

[0019] Example 4: A wet-process phosphoric acid slurry with an arsenic content of 50 ppm, a cadmium content of 40 ppm, and a copper content of 100 ppm was prepared. Sodium hydrosulfide at 0.20% of the wet-process phosphoric acid slurry mass was added, and the mixture was stirred at 85℃ and 120 r / min for 50 min. After the reaction, the slurry was pumped into a filter. Zinc dihexyl dithiophosphate at 0.20% of the wet-process phosphoric acid slurry mass was added at the front end of the pump. The mixture was reacted at 80℃ and 900 r / min for 90 s. After the reaction was complete, the mixture was filtered to obtain purified dilute phosphoric acid. The dilute phosphoric acid was then aged, concentrated, and aged again to obtain the final concentrated phosphoric acid. The purified dilute phosphoric acid was found to contain 0.13 ppm arsenic (99.74% removal rate), 0.25 ppm cadmium (99.38% removal rate), and 0.01 ppm copper (99.99% removal rate).

[0020] Example 5: A wet-process phosphoric acid slurry with an arsenic content of 60 ppm, a cadmium content of 45 ppm, and a copper content of 90 ppm was prepared. 0.40% (by weight) of hydrogen sulfide was introduced into the slurry, and the mixture was stirred at 85°C and 180 r / min for 40 min. After the reaction, the slurry was pumped into a filter. 0.20% (by weight) of didodecyl dithiophosphate was added to the front end of the pump, and the mixture was reacted at 78°C and 1300 r / min for 15 s. After the reaction was complete, the mixture was filtered to obtain purified dilute phosphoric acid. The dilute phosphoric acid was then aged, concentrated, and aged again to obtain the final concentrated phosphoric acid. The purified dilute phosphoric acid was found to contain 0.38 ppm arsenic (99.37% removal rate), 0.58 ppm cadmium (98.71% removal rate), and 0.01 ppm copper (99.99% removal rate).

Claims

1. A method for efficient and synergistic purification of multiple metals in wet-process phosphoric acid, characterized in that... Includes the following steps: (1) Add 0.05%-0.40% of inorganic sulfide by weight of wet phosphoric acid slurry to wet phosphoric acid slurry and react for 30-60 minutes at 80-85℃ and 100-200 r / min stirring rate; (2) Pump the slurry after reaction into a filter, add 0.05%-0.20% organic sulfide of wet phosphoric acid slurry at the front end of the pump, and react for 10-90 seconds at 70-80℃ and pump speed of 900-1500 r / min. (3) The dilute phosphoric acid is obtained by filtration. After aging, concentration and aging, the dilute phosphoric acid is used to obtain the finished concentrated phosphoric acid.

2. The method for efficient synergistic purification of multiple metals in wet-process phosphoric acid according to claim 1, characterized in that: The inorganic sulfide is one or a mixture of two or more of sodium hydrosulfide, sodium sulfide, ferrous sulfide, and hydrogen sulfide. The amount of the inorganic sulfide added is 0.15%-0.20%.

3. The method for efficient synergistic purification of multiple metals in wet-process phosphoric acid according to claim 1, characterized in that: The organic sulfide is one or a mixture of two or more of dialkyl dithiophosphate, dialkyl dithiophosphite, and dialkyl dithiophosphoric acid; the amount of organic sulfide added is 0.08%-0.10%.

4. The method for efficient synergistic purification of multiple metals in wet-process phosphoric acid according to claim 1, characterized in that: The organic sulfide is one or a mixture of two or more of sodium dibutyl dithiophosphate, sodium dibutyl dithiophosphoric acid, dioctyl dithiophosphate, zinc dihexadecanophosphate, or calcium didodecyl dithiophosphate.