Method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste

Abstract

The invention belongs to the technical field of waste recovery, and discloses a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, which comprises the following steps: mixing the tungsten-containing waste, the scheelite smelting slag containing calcium phosphate and sodium salt, roasting to obtain a roasted material, leaching the roasted material with water to obtain a sodium phosphate solution and water leaching slag, and the water leaching residues are subjected to alkaline leaching, and then a sodium tungstate solution and alkaline leaching residues are obtained. The invention further comprises application of the sodium phosphate solution to scheelite decomposition. According to the method, phosphorus in the scheelite smelting slag and tungsten in the tungsten-containing waste can be efficiently recycled while the low cost, the minimum environmental pollution and the operation convenience are kept, and therefore cyclic utilization and sustainable development of resources are powerfully promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of waste recycling, and in particular relates to a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste. Background Art

[0002] Tungsten is a rare and precious metal element, widely used in cemented carbide, special steel, electronic components and other fields. By recycling tungsten-containing waste, tungsten resources can be effectively extracted, thereby saving primary tungsten resources and reducing the demand for tungsten mining. Phosphorus is an important chemical raw material, which is widely used in agriculture, food, medicine, electronics and other fields. By recycling phosphorus in scheelite smelting slag, it is not only possible to reduce the mining of primary phosphate ore, but also to reduce production costs and improve the economic benefits of enterprises.

[0003] In the prior art, the method of using calcium salts (calcium carbonate, calcium hydroxide, calcium chloride) to recover tungsten-containing waste can effectively convert waste into calcium tungstate, but the subsequent hydrochloric acid decomposition step to obtain tungstic acid, and then the whole process of ammonia dissolution and other subsequent processing to make tungsten products is quite lengthy. In this process, the consumption of calcium salts is quite considerable, which increases the production cost. More importantly, hydrochloric acid, as a volatile acid, may not only cause the risk of environmental pollution during use, but also poses a severe challenge to production equipment due to its strong corrosiveness, forcing the equipment maintenance standards and operating requirements to be improved accordingly. On the other hand, the prior art also attempts to calcine tungsten-containing waste at high temperature (the temperature must reach or exceed 800°C), then add sodium salts (such as sodium carbonate, sodium hydroxide or sodium peroxide) to mix with the calcined materials to form a melt, and then pour the melt into a water leaching tank for leaching to obtain a sodium tungstate solution. However, this process is an intermittent high-temperature operation, which is not only easy to cause furnace stagnation inside the equipment, affecting production efficiency, but also has extremely high energy consumption, and the safety hazards during operation cannot be ignored, and the risk factor is significantly increased.

[0004] In addition, the existing technology for recovering phosphorus from scheelite smelting slag often adopts the principle of strong acid to weak acid, mixing scheelite slag with sulfuric acid to produce dilute phosphoric acid and calcium sulfate slag, which is cumbersome to operate and requires many supporting equipment.

[0005] Therefore, there is an urgent need to develop an efficient, clean and low-cost method for recycling tungsten and phosphorus from waste materials, so as to achieve the goal of secondary efficient recycling of tungsten and phosphorus resources. Summary of the invention

[0006] The purpose of the present invention is to provide a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, which can achieve efficient recovery of phosphorus in scheelite smelting slag and tungsten in tungsten-containing waste while maintaining low cost, minimizing environmental pollution and simplicity of operation, thereby effectively promoting the recycling and sustainable development of resources.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0009] The tungsten-containing waste material and the scheelite smelting slag containing calcium phosphate are mixed with sodium salt and roasted to obtain a roasted material, the roasted material is water-leached to obtain a sodium phosphate solution and water-leached slag, and the water-leached slag is alkali-leached to obtain a sodium tungstate solution and alkali-leached slag.

[0010] In some embodiments, the tungsten-containing waste includes, by mass percentage, 40% to 98% tungsten, 1% to 6% carbon, and 1% to 3% silicon.

[0011] In some embodiments, the scheelite smelting slag is obtained by decomposing scheelite through sodium phosphate, and the mass content of calcium phosphate in the scheelite smelting slag is 25% to 75%.

[0012] In some embodiments, the sodium salt is at least one of sodium carbonate, sodium chloride, and sodium sulfate.

[0013] In some embodiments, the added amount of calcium phosphate and sodium salt is 1 to 2 times the theoretical amount, and the theoretical amount of calcium phosphate and sodium salt is calculated based on the amount of silicon contained in the tungsten-containing waste and the molar ratio of calcium phosphate, silicon and sodium is 1:3:6.

[0014] In some embodiments, the calcination temperature is 200-400° C., and the calcination time is 1-3 hours.

[0015] In some embodiments, the water immersion operation is to immerse the roasted material in water at 80° C. to 100° C. for 1 to 2 hours at a solid-liquid mass ratio of 1:(1 to 2) and then perform solid-liquid separation.

[0016] In some embodiments, the alkali leaching operation is to place the obtained water-leached residue in an alkali solution at 80° C. to 100° C. at a solid-liquid mass ratio of 1:(1-2) for leaching.

[0017] Preferably, the alkali solution in the alkali leaching operation is at least one of a sodium hydroxide solution or a sodium carbonate solution, and the amount of sodium-containing substance added to the alkali solution is 1 to 2 times the theoretical amount. The theoretical amount of sodium-containing substance in the alkali solution is calculated based on the amount of tungsten contained in the tungsten-containing waste and in accordance with the molar ratio of tungsten to sodium of 1:2.

[0018] In some embodiments, the method further comprises using the sodium phosphate solution to decompose scheelite.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] The present invention combines tungsten-containing waste with scheelite slag containing calcium phosphate, and in the presence of sodium salt, after roasting and leaching treatment, realizes comprehensive and efficient recovery of tungsten and phosphorus, and the final phosphorus recovery rate can reach up to 99.31%, and the tungsten recovery rate can reach up to 99.63%, and the recovered phosphorus can be used for decomposing scheelite; at the same time, the present invention utilizes calcium phosphate and sodium salt to react with silicon and tungsten carbide in the tungsten-containing waste, and the reaction process has no furnace agglomeration phenomenon, and can avoid the tungsten-containing waste from forming a multi-component complex solid solution phase due to the influence of silicon during the roasting process, thereby affecting the leaching of tungsten. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow chart for the comprehensive recovery of tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste materials according to the present invention. DETAILED DESCRIPTION

[0022] The present invention provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, such as Figure 1 As shown, the following steps are included:

[0023] The tungsten-containing waste material and the scheelite smelting slag containing calcium phosphate are mixed with sodium salt and roasted to obtain a roasted material, the roasted material is water-leached to obtain a sodium phosphate solution and water-leached slag, and the water-leached slag is alkali-leached to obtain a sodium tungstate solution and alkali-leached slag.

[0024] Specifically, tungsten-containing waste containing 40% to 98% tungsten, 1% to 6% carbon, and 1% to 3% silicon by mass, scheelite smelting slag with a calcium phosphate mass content of 25% to 75%, and sodium salt are mixed, roasted at 200 to 400° C. for 1 to 3 hours, and then the roasted material is placed in water at 80° C. to 100° C. for 1 to 2 hours at a solid-liquid mass ratio of 1: (1 to 2), and then solid-liquid separation is performed to obtain sodium phosphate solution and water-leached residue, and then the water-leached residue is placed in at least one alkaline solution of sodium hydroxide solution or sodium carbonate solution at 80° C. to 100° C. at a solid-liquid mass ratio of 1: (1 to 2) for leaching. Sodium tungstate solution and alkali leaching residue are obtained, wherein the addition amount of calcium phosphate and sodium salt is 1 to 2 times of the theoretical amount respectively, and the theoretical amount of calcium phosphate and sodium salt is calculated based on the amount of silicon contained in the tungsten-containing waste and the molar ratio of calcium phosphate, silicon and sodium is 1:3:6; the alkali solution in the alkali leaching operation is at least one of sodium hydroxide solution or sodium carbonate solution, and the addition amount of sodium-containing substance in the alkali solution is 1 to 2 times of the theoretical amount, preferably 1.2 times, and the theoretical amount of sodium-containing substance in the alkali solution is calculated based on the amount of tungsten contained in the tungsten-containing waste and the molar ratio of tungsten to sodium is 1:2.

[0025] It should be noted that calcium phosphate is used to provide calcium ions to combine with silicon, and phosphate is combined with sodium ions to form calcium silicate and sodium phosphate, so as to avoid the formation of low-melting-point sticky substances such as sodium silicate and sodium tungstate to wrap the material or stick to the furnace wall, to avoid the formation of agglomerates that affect the further oxidation of tungsten-containing waste and cause furnace agglomeration, and at the same time, to avoid the formation of multi-component complex solid solution phases such as Fe(Al,Cu,Ti,Co)O*xSiO2*yWO3 due to the influence of silicon during the roasting process of tungsten-containing waste, which affects the leaching of tungsten.

[0026] It should be noted that although tungsten-containing waste and calcium phosphate-containing scheelite slag can react with sodium salt at room temperature, the reaction power is insufficient at room temperature, and the higher the temperature, the more thorough the reaction. When a certain temperature is reached, the reaction efficiency has reached the top value and will no longer increase, so 200-400°C is selected.

[0027] The present invention also includes using the sodium phosphate solution for decomposing scheelite, and the specific operation is: adding the sodium phosphate solution to scheelite, wherein the amount of sodium phosphate added is 1.3 times the theoretical amount required for the reaction of calcium tungstate and sodium phosphate to generate calcium phosphate and sodium tungstate, and reacting for 2 hours at a temperature not lower than 160°C.

[0028] In the present invention, unless otherwise specified, the contents of all substances mentioned refer to their mass percentages.

[0029] The calculation method of phosphorus leaching rate, tungsten recovery rate and scheelite decomposition rate in the present invention is as follows:

[0030] Phosphorus leaching rate (%) = phosphorus content in the sodium phosphate solution obtained after water leaching (%) × weight of the sodium phosphate solution obtained after water leaching (g) ÷ (phosphorus content of the used scheelite slag (%) × weight of the used scheelite slag (g))

[0031] Tungsten recovery rate (%) = tungsten content in sodium tungstate solution obtained after alkali leaching (%) × weight of sodium tungstate solution obtained after alkali leaching (g) ÷ (tungsten content in tungsten-containing waste used (%) × weight of tungsten-containing waste used (g))

[0032] Scheelite decomposition rate (%) = 100% - tungsten content of decomposition residue (%) × decomposition residue amount (g) ÷ (tungsten content in the used scheelite (%) × weight of the used scheelite (g))

[0033] The present invention is further described in detail in conjunction with specific embodiments. The following embodiments can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0034] Embodiment 1:

[0035] This embodiment provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0036] (1) Take 300 g of tungsten-containing waste (tungsten content of 79%, carbon content of 6%, silicon content of 3%), add calcium phosphate and sodium carbonate at twice the theoretical amount, take 88.57 g of scheelite slag (calcium phosphate content of 75%), and mix 68.14 g of sodium carbonate with the tungsten-containing waste;

[0037] (2) After mixing, the mixture was calcined at 400°C for 3 hours, but the process was not completed;

[0038] (3) The roasted material was immersed in hot water at 80°C for 1 hour at a solid-liquid mass ratio of 1:2. The solid-liquid separation resulted in a leachate and a leachate residue. The phosphorus leaching rate was 99.31% based on the phosphorus concentration of the solution. The leachate was returned for the decomposition of scheelite, and the decomposition rate of scheelite was 99.19%, with no abnormality in the decomposition.

[0039] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 0.76% tungsten and the tungsten recovery rate is 99.63%.

[0040] Embodiment 2:

[0041] This embodiment provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0042] (1) Take 300 g of tungsten-containing waste (tungsten content of 98%, carbon content of 1%, silicon content of 1%), add calcium phosphate and sodium carbonate at 1 times the theoretical amount, take 44.29 g of scheelite slag (calcium phosphate content of 25%), and mix 11.36 g of sodium carbonate with the tungsten-containing waste;

[0043] (2) After mixing, the mixture was calcined at 200°C for 1 hour, but the process was not completed;

[0044] (3) The roasted material was immersed in hot water at 80°C for 1 hour at a solid-liquid mass ratio of 1:2. The solid-liquid separation resulted in a leachate and a leachate residue. The phosphorus leaching rate was 97.51% based on the phosphorus concentration of the solution. The leachate was returned for the decomposition of scheelite, and the decomposition rate of scheelite was 99.33%, with no abnormality in the decomposition.

[0045] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 2.16% tungsten, and the tungsten recovery rate is 98.63%.

[0046] Embodiment 3:

[0047] This embodiment provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0048] (1) Take 300 g of tungsten-containing waste (tungsten content of 40%, carbon content of 6%, silicon content of 3%), add calcium phosphate and sodium carbonate at twice the theoretical amount, take 88.57 g of scheelite slag (calcium phosphate content of 75%), and mix 68.14 g of sodium carbonate with the tungsten-containing waste;

[0049] (2) After mixing, the mixture was calcined at 400°C for 3 hours, but the process was not completed;

[0050] (3) The roasted material was immersed in hot water at 80°C for 1 hour at a solid-liquid mass ratio of 1:2. The solid-liquid separation resulted in a leachate and a leachate residue. The phosphorus leaching rate was 99.26% based on the phosphorus concentration of the solution. The leachate was returned for the decomposition of scheelite. The decomposition rate of scheelite was 99.27%, and there was no abnormality in the decomposition.

[0051] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 0.81% tungsten and the tungsten recovery rate is 99.59%.

[0052] Embodiment 4:

[0053] This embodiment provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0054] (1) Take 300 g of tungsten-containing waste (tungsten content of 68%, carbon content of 6%, silicon content of 3%), add 1.5 times the theoretical amount of calcium phosphate and sodium carbonate, take 66.43 g of scheelite slag (calcium phosphate content of 75%), and mix 51.11 g of sodium carbonate with the tungsten-containing waste;

[0055] (2) After mixing, the mixture was calcined at 300°C for 2 hours, but the process was not completed;

[0056] (3) The roasted material was immersed in hot water at 80°C for 1 hour at a solid-liquid mass ratio of 1:2. The solid-liquid separation resulted in a leachate and a leachate residue. The phosphorus leaching rate was 99.11% based on the phosphorus concentration of the solution. The leachate was returned for the decomposition of scheelite, and the decomposition rate of scheelite was 99.23%, with no abnormality in the decomposition.

[0057] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 1.16% tungsten and the tungsten recovery rate is 99.29%.

[0058] Embodiment 5:

[0059] This embodiment provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0060] (1) Take 300 g of tungsten-containing waste (tungsten content of 58%, carbon content of 3%, silicon content of 1.5%), add calcium phosphate and sodium carbonate at twice the theoretical amount, take 66.43 g of scheelite slag (calcium phosphate content of 50%), and mix 34.07 g of sodium carbonate with the tungsten-containing waste;

[0061] (2) After mixing, the mixture was calcined at 200°C for 3 hours, but the process was not completed;

[0062] (3) The roasted material was immersed in hot water at 80°C for 1 hour at a solid-liquid mass ratio of 1:2. The solid-liquid separation resulted in a leachate and a leachate residue. The phosphorus leaching rate was 98.21% based on the phosphorus concentration of the solution. The leachate was returned for the decomposition of scheelite, and the decomposition rate of scheelite was 99.26%, with no abnormality in the decomposition.

[0063] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 1.56% tungsten, and the tungsten recovery rate is 99.03%.

[0064] Embodiment 6:

[0065] Compared with Example 1, calcium phosphate and sodium carbonate were added at 1 times the theoretical amount, 44.29 g of scheelite slag (calcium phosphate content 75%) and 34.07 g of sodium carbonate were mixed with tungsten-containing waste, and other conditions remained unchanged. The phosphorus leaching rate was measured to be 98.43%, the residual slag contained 2.18% tungsten, and the tungsten recovery rate was 98.88%.

[0066] Embodiment 7:

[0067] Compared with Example 1, calcium phosphate and sodium carbonate were added at 1.5 times the theoretical amount, 66.43 g of scheelite slag (calcium phosphate content 75%) and 51.11 g of sodium carbonate were mixed with tungsten-containing waste, and other conditions remained unchanged. The phosphorus leaching rate was measured to be 99.01%, the residual slag contained 1.88% tungsten, and the tungsten recovery rate was 99.21%.

[0068] Comparative Example 1:

[0069] This comparative example provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0070] (1) Take 300 g of tungsten-containing waste (tungsten mass content of 79%, carbon mass content of 6%, silicon mass content of 3%), add calcium phosphate at twice the theoretical amount, and take 88.57 g of scheelite slag (calcium phosphate content of 75%) and mix it with the tungsten-containing waste;

[0071] (2) After mixing, the mixture was calcined at 400°C for 3 hours, but the process was not completed;

[0072] (3) the roasted material was placed in 80° C. hot water for immersion for 1 hour at a solid-liquid mass ratio of 1:2, and the solid-liquid separation was performed to obtain a leachate and a leached residue. According to the phosphorus concentration of the solution, the phosphorus leaching rate was measured to be 0%;

[0073] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 21.36% tungsten, and the tungsten recovery rate is 81.03%.

[0074] Comparative Example 2:

[0075] This comparative example provides a method for comprehensively recovering tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, comprising the following steps:

[0076] (1) 300 g of tungsten-containing waste (tungsten mass content: 79%, carbon mass content: 6%, silicon mass content: 3%) was taken, sodium carbonate was added at twice the theoretical amount, and 68.14 g of sodium carbonate was mixed with the tungsten-containing waste;

[0077] (2) After mixing, the mixture was calcined at 400°C for 3 hours, and a calcination occurred during the process;

[0078] (3) the roasted material was placed in 80° C. hot water for immersion for 1 hour at a solid-liquid mass ratio of 1:2, and the solid-liquid separation was performed to obtain a leachate and a leached residue. According to the phosphorus concentration of the solution, the phosphorus leaching rate was measured to be 0%;

[0079] (4) The water-leached residue obtained in step (3) is leached with sodium hydroxide solution at a solid-liquid mass ratio of 1:2 at a temperature of 80° C., and the amount of sodium hydroxide added is 1.2 times the theoretical amount. After leaching, the solid and liquid are separated to obtain a sodium tungstate solution and an alkaline leached residue. The alkaline leached residue is dried, weighed, and analyzed for residual tungsten content. The residual residue contains 11.76% tungsten and the tungsten recovery rate is 91.33%.

[0080] Comparative Example 3:

[0081] Compared with Example 1, calcium phosphate and sodium carbonate were added at 0.5 times the theoretical amount, 22.14 g of scheelite slag (calcium phosphate content 75%) and 17.04 g of sodium carbonate were mixed with tungsten-containing waste, and other conditions remained unchanged. The phosphorus leaching rate was measured to be 83.17%, the residual slag contained 21.83% tungsten, and the tungsten recovery rate was 87.97%.

[0082] Comparative Example 4:

[0083] Compared with Example 1, calcium phosphate and sodium carbonate were added at 2.5 times the theoretical amount, 110.71 g of scheelite slag (calcium phosphate content 75%) and 85.18 g of sodium carbonate were mixed with tungsten-containing waste, and other conditions remained unchanged. The phosphorus leaching rate was measured to be 99.25%, the residual slag contained 2.18% tungsten, and the tungsten recovery rate was 98.88%.

[0084] Comparative Example 5:

[0085] Compared with Example 1, the amount of sodium hydroxide added was 0.8 times the theoretical amount, and other conditions remained unchanged. The residual slag was measured to contain 3.28% tungsten, and the tungsten recovery rate was 98.63%.

[0086] Comparative Example 6:

[0087] Compared with Example 1, the amount of sodium hydroxide added was 1 times the theoretical amount, and other conditions remained unchanged. The residual slag was measured to contain 1.05% tungsten, and the tungsten recovery rate was 99.44%.

[0088] Comparative Example 7:

[0089] Compared with Example 1, the amount of sodium hydroxide added was twice the theoretical amount, and other conditions remained unchanged. The residual slag was measured to contain 0.73% tungsten and the tungsten recovery rate was 99.64%.

[0090] Comparative Example 8:

[0091] Compared with Example 1, the amount of sodium hydroxide added was 2.5 times the theoretical amount, and other conditions remained unchanged. The residual slag was measured to contain 0.73% tungsten and the tungsten recovery rate was 99.64%.

[0092] From the comparison results of the phosphorus leaching rate and the tungsten recovery rate in Example 1, Comparative Examples 1 and 2, it can be seen that when no sodium carbonate or scheelite slag is added, the phosphorus leaching rate is 0%, and the tungsten recovery rates are 81.03% and 91.33%, respectively. When sodium carbonate and scheelite slag are added at the same time, the phosphorus leaching rate can reach 99.31%, and the tungsten recovery rate can reach 99.63%, indicating that the use of sodium carbonate and scheelite slag together can not only achieve phosphorus leaching, but also improve the tungsten recovery rate.

[0093] From the comparison results of phosphorus leaching rate and tungsten recovery rate in Example 1, Example 6, Example 7 and Comparative Example 3 and Comparative Example 4, it can be seen that when the amount of sodium carbonate and calcium phosphate (derived from scheelite slag) added is 0.5 times the theoretical amount, the phosphorus leaching rate and tungsten recovery rate are both lower than 90%, while when the addition amount is 1 times the theoretical amount, the phosphorus leaching rate can reach 98.43%, and the tungsten recovery rate can reach 98.88%. And with the increase of the addition amount, the phosphorus leaching rate and tungsten recovery rate are improved. When the addition amount is 2 times the theoretical amount, the phosphorus leaching rate can reach 99.31%, and the tungsten recovery rate can reach 99.63%. However, when the addition amount is further increased to 2.5 times the theoretical amount, the phosphorus leaching rate is reduced to 99.25%, and the tungsten recovery rate is reduced to 98.88%. Taking into account the effective utilization of resources, the optimal addition amount of sodium carbonate and calcium phosphate (derived from scheelite slag) in this application is 1 to 2 times the theoretical amount.

[0094] From the comparison results of the tungsten recovery rates in Example 1 and Comparative Examples 5 to 8, it can be seen that when the amount of sodium hydroxide added is 1 times the theoretical amount, the tungsten recovery rate can be increased to more than 99%, and as the alkalinity increases, the rising trend of the tungsten recovery rate slows down until it remains unchanged. Therefore, the present application selects the amount of sodium hydroxide added to be 1 to 2 times the theoretical amount, preferably 1.2 times.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for comprehensive recovery of tungsten and phosphorus from scheelite smelting slag and tungsten-containing waste, characterized in that: The following steps are involved: The tungsten-containing waste material and the scheelite smelting slag containing calcium phosphate are mixed with sodium salt and roasted to obtain a roasted material, the roasted material is water-leached to obtain a sodium phosphate solution and water-leached slag, and the water-leached slag is alkali-leached to obtain a sodium tungstate solution and alkali-leached slag.

2. The method according to claim 1, characterized in that Calculated by mass percentage, the tungsten-containing waste includes 40% to 98% tungsten, 1% to 6% carbon, and 1% to 3% silicon.

3. The method according to claim 1, characterized in that The scheelite smelting slag is obtained by decomposing scheelite through sodium phosphate, and the mass content of calcium phosphate in the scheelite smelting slag is 25% to 75%.

4. The method according to claim 1, characterized in that: The sodium salt is at least one of sodium carbonate, sodium chloride and sodium sulfate.

5. The method according to claim 1, characterized in that The added amount of calcium phosphate and sodium salt is 1 to 2 times of the theoretical amount respectively. The theoretical amount of calcium phosphate and sodium salt is calculated based on the amount of silicon contained in the tungsten-containing waste and the molar ratio of calcium phosphate, silicon and sodium is 1:3:

6.

6. The method according to claim 1, characterized in that The calcination temperature is 200-400° C., and the calcination time is 1-3 hours.

7. The method according to claim 1, characterized in that The water immersion operation is to immerse the roasted material in water at 80° C. to 100° C. for 1 to 2 hours at a solid-liquid mass ratio of 1:(1 to 2) and then perform solid-liquid separation.

8. The method according to claim 1, characterized in that The alkali leaching operation is to place the obtained water-leached residue in an alkali solution at 80° C. to 100° C. for leaching at a solid-liquid mass ratio of 1:(1-2).

9. The method according to claim 1 or 8, characterized in that: The alkali solution in the alkali leaching operation is at least one of a sodium hydroxide solution or a sodium carbonate solution. The amount of sodium-containing substance added to the alkali solution is 1 to 2 times the theoretical amount. The theoretical amount of sodium-containing substance in the alkali solution is calculated based on the amount of tungsten contained in the tungsten-containing waste and follows the molar ratio of tungsten to sodium of 1:

2.

10. The method according to claim 1, characterized in that The method further comprises using the sodium phosphate solution to decompose scheelite.

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