Preparation method of ferrous oxalate

Abstract

The invention discloses a preparation method of ferrous oxalate, and belongs to the field of cyanidation tailing resource utilization, and the method comprises the following steps: preparing ferrous oxalate by using ferric oxalate prepared from a cyanidation tailing leachate as a raw material; wherein the cyanidation tailing leaching solution is a leaching solution generated in a cyanidation tailing iron removal process; according to the method, the ferric oxalate prepared from the cyanidation tailing leachate is used as a raw material to prepare the ferrous oxalate, the ferric oxalate plays a role in providing a Fe < 3 + > source and C2O4 < 2-> precipitation ions in the preparation process of the ferrous oxalate, and an inorganic iron source and a precipitator oxalic acid or oxalate do not need to be purchased in the preparation process, so that the preparation cost of the ferrous oxalate is relatively low; the preparation process is simple, high-salinity wastewater is not generated, and the method is a clean technology for preparing ferrous oxalate; secondly, the prepared ferrous oxalate does not contain Cl <-> or SO4 < 2->, and the product quality is high; according to the method, ferric oxalate prepared from the cyanidation tailing leachate is used as a raw material to prepare oxalic acid, and diversified utilization of iron in the cyanidation tailings is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of resource utilization of iron in cyanide tailings, and particularly relates to a method for preparing ferrous oxalate. Background Art

[0002] Ferrous oxalate is an important chemical product, mainly used as a photographic developer, an analytical reagent, a raw material for producing iron supplements in the pharmaceutical industry, a raw material for manufacturing green pigments in the dye industry, a plant growth regulator or a trace element fertilizer in agriculture, and a precipitant for divalent metals in the preparation industry of nanomaterials. In addition, battery-grade ferrous oxalate can also be used as an iron source raw material for the positive electrode material lithium iron phosphate of the battery.

[0003] Currently, ferrous oxalate is mainly prepared by the precipitation method, and there are also research reports on preparing ferrous oxalate by mechanical grinding method, agar medium gel method and photochemical method; among them, when preparing ferrous oxalate by the precipitation method and the mechanical grinding method, the iron source is Fe 2+ inorganic iron salts, such as ferrous sulfate and ferrous chloride, and the precipitants are oxalic acid, sodium oxalate or ammonium oxalate. High-salt wastewater containing SO 4 2- or Cl - will be generated during the preparation process, polluting the environment and requiring desalination treatment. The photochemical precipitation method uses a solution containing iron oxalate complex as the raw material to prepare ferrous oxalate under visible light or ultraviolet light irradiation. The preparation process will oxidize and consume C 2 O 4 2- and the power consumption of the photocatalysis process is large and the production cost is high; therefore, it is urgent to develop a method for preparing ferrous oxalate with less environmental pollution, low energy consumption and low production cost. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention provides a method for preparing ferrous oxalate to solve the technical problems of large environmental pollution, high energy consumption and high production cost in the traditional preparation process of ferrous oxalate.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a method for preparing ferrous oxalate, which uses the ferric oxalate salt prepared from the cyanide tailings leachate as the raw material to prepare ferrous oxalate; wherein, the cyanide tailings leachate is the leachate generated during the process of removing iron and enriching gold from cyanide tailings.

[0006] Further, the process of using the ferric oxalate salt prepared from the cyanide tailings leachate as the raw material to prepare ferrous oxalate includes: Dissolving the ferric oxalate salt in water to obtain a raw material solution; A reducing agent is added to the raw material liquid, and a stirring reduction reaction is carried out. After the reaction ends, liquid-solid separation is carried out to obtain a reduction product and a reduced liquid; wherein, the reduction product is ferrous oxalate; An antisolvent is added to the reduced liquid, and antisolvent crystallization is carried out to obtain an antisolvent crystallization liquid; Liquid-solid separation is carried out on the antisolvent crystallization liquid to obtain oxalate crystals and a crystallization mother liquor; Rectification treatment is carried out on the crystallization mother liquor to obtain a top product and a bottom product.

[0007] Furthermore, the reducing agent is vitamin C; the ferric oxalate salt is ammonium ferric oxalate or sodium ferric oxalate.

[0008] Furthermore, during the process of adding a reducing agent to the raw material liquid and carrying out a stirring reduction reaction, the reduction temperature is 75-95 °C, the reduction time is 20-60 min, and the stirring speed is 0-200 r / min.

[0009] Furthermore, the antisolvent is absolute ethanol.

[0010] Furthermore, the temperature of antisolvent crystallization is 10-20 °C.

[0011] Furthermore, the top product is gaseous absolute ethanol; the bottom product is 2,3-diketo-L-gulonic acid.

[0012] Furthermore, the oxalate crystals are sodium oxalate or ammonium oxalate.

[0013] Furthermore, the preparation process of the ferric oxalate salt prepared from the cyanidation tailing leaching solution is as follows: The cyanidation tailing leaching solution is evaporated, concentrated, cooled and crystallized, redissolved, secondarily evaporated, secondarily concentrated, and secondarily cooled and crystallized to obtain the ferric oxalate salt.

[0014] Furthermore, the mass-volume ratio of the ferric oxalate salt to water in the raw material liquid is 5 g:(40-80) mL.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The preparation method of ferrous oxalate provided by the present invention uses the ferric oxalate salt prepared from the cyanidation tailing leaching solution as a raw material, and ferrous oxalate is prepared by reducing the ferric oxalate salt with a reducing agent; wherein, using the ferric oxalate salt prepared from the cyanidation tailing leaching solution as a raw material can simultaneously provide Fe 3+ source and C 2 O 4 2-Precipitating ions eliminates the need to newly purchase inorganic iron salts and precipitants, and there is no need to separately add a precipitant, which makes the preparation cost of ferrous oxalate relatively low, and at the same time realizes the diversified utilization of iron in cyanidation tailings. Secondly, the equipment and operation process in the preparation process are simple, and no high-salt wastewater is generated, which is a clean technology for preparing ferrous oxalate. In addition, the prepared ferrous oxalate does not contain Cl - or SO 4 2- , and the product quality is high.

[0016] Furthermore, recovering oxalates and 2,3-diketo-L-gulonic acid from the reduced solution regenerates the iron-removing reagents ammonium oxalate or sodium oxalate, which can reduce the reagent cost in the iron-removing process of cyanidation tailings, and 2,3-diketo-L-gulonic acid is also an important chemical product. By rectifying the crystallization mother liquor, the recovery of the antisolvent is realized, reducing the preparation cost of ferrous oxalate. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is the morphology diagram of the ferrous oxalate prepared in Examples 1-4; among them, Figure 1 a is the morphology diagram of the ferrous oxalate prepared at a stirring speed of 200 r / min, Figure 1 b is the morphology diagram of the ferrous oxalate prepared at a stirring speed of 100 r / min, Figure 1 c is the morphology diagram of the ferrous oxalate prepared at a stirring speed of 150 r / min, Figure 1 d is the morphology diagram of the ferrous oxalate prepared at a stirring speed of 0 r / min; Figure 2 It is the morphology diagram of the ferrous oxalate prepared in Examples 5-8; among them, Figure 2 a is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 75 °C, Figure 2 b is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 80 °C, Figure 2 c is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 85 °C, Figure 2 d is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 95 °C; Figure 3 It is the morphology diagram of the ferrous oxalate prepared in Examples 9-12; among them, Figure 3Figure a shows the morphology of ferrous oxalate prepared with the mass-volume ratio of ammonium ferric oxalate to water being 5 g:40 mL. Figure 3 Figure b shows the morphology of ferrous oxalate prepared with the mass-volume ratio of ammonium ferric oxalate to water being 5 g:50 mL. Figure 3 Figure c shows the morphology of ferrous oxalate prepared with the mass-volume ratio of ammonium ferric oxalate to water being 5 g:70 mL. Figure 3 Figure d shows the morphology of ferrous oxalate prepared with the mass-volume ratio of ammonium ferric oxalate to water being 5 g:80 mL.

[0019] Figure 4 They are the morphology diagrams of ferrous oxalate prepared in Examples 1, 18 - 19. Among them, Figure 4 Figure a shows the morphology of ferrous oxalate prepared with a reduction time of 60 min. Figure 4 Figure b shows the morphology of ferrous oxalate prepared with a reduction time of 20 min. Figure 4 Figure c shows the morphology of ferrous oxalate prepared with a reduction time of 40 min.

[0020] Figure 5 They are the morphology diagrams of ferrous oxalate prepared in Examples 1, 21 - 23. Among them, Figure 5 Figure a shows the morphology of ferrous oxalate prepared at a pH of 2.85. Figure 5 Figure b shows the morphology of ferrous oxalate prepared at a pH of 3.70. Figure 5 Figure c shows the morphology of ferrous oxalate prepared at a pH of 4.70. Figure 5 Figure d shows the morphology of ferrous oxalate prepared at a pH of 5.80. Detailed implementation manners

[0021] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer and more understandable, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope protected by this application.

[0022] The present invention provides a method for preparing ferrous oxalate, which uses the ferric oxalate salt prepared from the cyanide tailing leaching solution as the raw material to prepare ferrous oxalate. Among them, the cyanide tailing leaching solution is the leaching solution generated during the process of removing iron and enriching gold from cyanide tailings. The ferric oxalate salt is ammonium ferric oxalate or sodium ferric oxalate, and vitamin C is used as the reducing agent.

[0023] Specifically, the method for preparing ferrous oxalate includes the following steps: Step 1: Evaporate, concentrate, cool and crystallize, redissolve, secondarily evaporate, secondarily concentrate, and secondarily cool and crystallize the cyanidation tailing leachate to obtain ferric oxalate salt; wherein, the ferric oxalate salt is ammonium ferric oxalate or sodium ferric oxalate; dissolve the ferric oxalate salt in water to obtain a raw material solution; wherein, the mass-volume ratio of the ferric oxalate salt to water in the raw material solution is 5 g:(40 - 80) mL.

[0024] Step 2: Add vitamin C to the raw material solution and carry out a stirring reduction reaction. After the reaction ends, perform liquid-solid separation to obtain a reduction product and a reduced solution; wherein, the mass ratio of vitamin C to ferric oxalate salt is 5 g:(0.6 - 0.8) g; the reduction temperature is 75 - 95 °C, the reduction time is 20 - 60 min, the stirring speed is 0 - 200 r / min, and the pH is 2.85 - 5.80; the reduction product is ferrous oxalate, and the components of the reduced solution include oxalate and 2,3-diketogulonic acid.

[0025] Step 3: Add absolute ethanol as a salting-out agent to the reduced solution and carry out salting-out crystallization to obtain a salting-out crystallization solution; wherein, the temperature of the salting-out crystallization is 10 - 20 °C.

[0026] Step 4: Perform liquid-solid separation on the salting-out crystallization solution to obtain oxalate crystals and a crystallization mother liquor; wherein, the oxalate crystals are ammonium oxalate or sodium oxalate, and the components of the salting-out solution include absolute ethanol and 2,3-diketogulonic acid.

[0027] Step 5: Carry out rectification treatment on the crystallization mother liquor to obtain a top product and a bottom product; wherein, the top product is gaseous absolute ethanol; the bottom product is 2,3-diketogulonic acid.

[0028] Preparation principle: For the preparation method of ferrous oxalate described in the present invention, the leachate generated during the iron removal process of cyanidation tailings is evaporated, concentrated, crystallized, redissolved, secondarily evaporated, secondarily concentrated, and secondarily cooled and crystallized to obtain ferric oxalate salt. Using the ferric oxalate salt prepared from the cyanidation tailings leachate as the iron source and vitamin C as the reducing agent, the strong reducibility of vitamin C is utilized to reduce the Fe 2 O 4 2- complexed with C 3+ to Fe 2+ , and release the C 3+ complexed with Fe 2 O 4 2- , and Fe 2+ reacts with the released C 2 O 4 2-The reaction produces ferrous oxalate; among them, ferric oxalate plays a role in providing Fe 3+ source and C 2 O 4 2- precipitation ions.

[0029] Specifically, using ferric oxalate as the iron source, in the process of preparing ferrous oxalate by reducing 1 mol of ferric oxalate with 1 mol of vitamin C, 3 mol of C 2 O 4 2- is released, among which 1 mol of C 2 O 4 2- participates in the reaction of forming ferrous oxalate with Fe 2+ ; 2 mol of C 2 O 4 2- exists in the reduced solution in the form of oxalate; the oxidation product of vitamin C reducing ferric oxalate is mainly 2,3-diketogulonic acid; by carrying out fractional crystallization and rectification treatment on the reduced solution, the recovery of oxalate and 2,3-diketogulonic acid from the reduced solution is realized; among them, the recovery of oxalate regenerates the iron removal reagent, reducing the reagent cost in the iron removal process of cyanide tailings, and 2,3-diketogulonic acid is also an important chemical product; moreover, rectifying the crystallization mother liquor can also recover the precipitating agent anhydrous ethanol, further reducing the preparation cost of ferrous oxalate.

[0030] In the present invention, using the ferric oxalate prepared from the cyanide tailings leaching solution as the source of Fe 3+ source and C 2 O 4 2- makes it unnecessary to purchase inorganic iron sources and precipitating agents such as oxalic acid or oxalate during the preparation of ferrous oxalate, effectively reducing the preparation cost of ferrous oxalate; the equipment and operation process in the preparation process are simple, and no high-salt wastewater is generated, and the prepared ferrous oxalate does not contain Cl - or SO 4 2- , and the product quality is high; in addition, using ferric oxalate as the raw material and reducing it with vitamin C to prepare ferrous oxalate solves the problem that the ferric oxalate prepared from the cyanide tailings leaching solution has a large output and limited market application, and opens up a new way for the diversified utilization of iron resources in cyanide tailings.

[0031] Example 1 This Example 1 provides a method for preparing ferrous oxalate, including the following steps: Step 1: Evaporate, concentrate, cool and crystallize the leaching solution of cyanide tailings, redissolve it, perform secondary evaporation, secondary concentration, and secondary cooling crystallization to obtain ammonium ferric oxalate; add 5 g of ammonium ferric oxalate to 60 mL of water and stir to dissolve to obtain the raw material solution.

[0032] Step 2: Add 0.75 g of vitamin C to the raw material solution, carry out a stirring reduction reaction at 90 °C for 60 min, perform liquid-solid separation after the reaction to obtain the reduction product and the reduced solution; among them, the stirring speed is 200 r / min; the pH is 2.85; the reduction product is ferrous oxalate, and the components of the reduced solution include ammonium oxalate and 2,3-diketo-L-gulonic acid.

[0033] Step 3: Add absolute ethanol as a salting-out agent to the reduced solution, carry out salting-out crystallization at 10 °C to obtain the salting-out crystallization solution.

[0034] Step 4: Perform liquid-solid separation on the salting-out crystallization solution to obtain ammonium oxalate crystals and the crystallization mother liquor; among them, the components of the salting-out solution include absolute ethanol and 2,3-diketo-L-gulonic acid.

[0035] Step 5: Perform rectification treatment on the crystallization mother liquor to obtain the top product and the bottom product; among them, the top temperature is 79 °C, and the top product is gaseous absolute ethanol; the bottom temperature is 105 °C, and the bottom product is 2,3-diketo-L-gulonic acid.

[0036] Example 2 The difference between Example 2 and the above Example 1 is that the stirring speed in Step 2 is 100 r / min; the others are the same as those in Example 1 and will not be repeated here.

[0037] Example 3 The difference between Example 3 and the above Example 1 is that the stirring speed in Step 2 is 150 r / min; the others are the same as those in Example 1 and will not be repeated here.

[0038] Example 4 The difference between Example 4 and the above Example 1 is that the stirring speed in Step 2 is 0 r / min; the others are the same as those in Example 1 and will not be repeated here.

[0039] Example 5 The difference between Example 5 and the above Example 1 is that the reduction temperature in Step 2 is 75 °C; the others are the same as those in Example 1 and will not be repeated here.

[0040] Example 6 The difference between Example 6 and the above Example 1 is that the reduction temperature in Step 2 is 80 °C; the others are the same as those in Example 1 and will not be repeated here.

[0041] Example 7 Example 7 is different from Example 1 above in that the reduction temperature in Step 2 is 85°C; the others are the same as those in Example 1 and will not be repeated here.

[0042] Example 8 Example 8 is different from Example 1 above in that the reduction temperature in Step 2 is 95°C; the others are the same as those in Example 1 and will not be repeated here.

[0043] Example 9 Example 9 is different from Example 1 above in that in Step 1, the raw material liquid is obtained by adding 5 g of ammonium ferric oxalate to 40 mL of water and stirring to dissolve; the others are the same as those in Example 1 and will not be repeated here.

[0044] Example 10 Example 10 is different from Example 1 above in that in Step 1, the raw material liquid is obtained by adding 5 g of ammonium ferric oxalate to 50 mL of water and stirring to dissolve; the others are the same as those in Example 1 and will not be repeated here.

[0045] Example 11 Example 11 is different from Example 1 above in that in Step 1, the raw material liquid is obtained by adding 5 g of ammonium ferric oxalate to 70 mL of water and stirring to dissolve; the others are the same as those in Example 1 and will not be repeated here.

[0046] Example 12 Example 12 is different from Example 1 above in that in Step 1, the raw material liquid is obtained by adding 5 g of ammonium ferric oxalate to 80 mL of water and stirring to dissolve; the others are the same as those in Example 1 and will not be repeated here.

[0047] Example 13 Example 13 is different from Example 1 above in that the mass of vitamin C in Step 2 is 0.60 g, and the others are the same as those in Example 1 and will not be repeated here; among them, the precipitation rate of iron in this Example 13 is 66.64%.

[0048] Example 14 Example 14 is different from Example 1 above in that the mass of vitamin C in Step 2 is 0.80 g, and the others are the same as those in Example 1 and will not be repeated here; among them, the precipitation rate of iron in this Example 13 is 96.02%.

[0049] Example 15 Example 15 is different from Example 1 above in that the temperature of fractional crystallization by antisolvent in Step 3 is 10°C; the others are the same as those in Example 1 and will not be repeated here.

[0050] Example 16 Example 16 The difference from Example 1 above is that the temperature of antisolvent crystallization in step 3 is 15°C; others are the same as those in Example 1 and will not be repeated here.

[0051] Example 17 Example 17 The difference from Example 1 above is that the temperature of antisolvent crystallization in step 3 is 20°C; others are the same as those in Example 1 and will not be repeated here.

[0052] Example 18 Example 18 The difference from Example 1 above is that the reduction time in step 2 is 20 min; others are the same as those in Example 1 and will not be repeated here; among them, the precipitation rate of iron in this Example 18 is 88.01%.

[0053] Example 19 Example 19 The difference from Example 1 above is that the reduction time in step 2 is 40 min; others are the same as those in Example 1 and will not be repeated here; among them, the precipitation rate of iron in this Example 19 is 96.00%.

[0054] Example 20 Example 20 The difference from Example 1 above is that ammonium ferric oxalate in step 1 is sodium ferric oxalate; others are the same as those in Example 1 and will not be repeated here.

[0055] Example 21 Example 21 The difference from Example 1 above is that the pH in step 2 is 3.70; others are the same as those in Example 1 and will not be repeated here.

[0056] Example 22 Example 22 The difference from Example 1 above is that the pH in step 2 is 4.70; others are the same as those in Example 1 and will not be repeated here.

[0057] Example 23 Example 23 The difference from Example 1 above is that the pH in step 2 is 5.80; others are the same as those in Example 1 and will not be repeated here.

[0058] As shown in the Figure 1 attachment, the Figure 1 morphology diagrams of ferrous oxalate prepared in Examples 1-4 are given; among them, Figure 1 a is the morphology diagram of ferrous oxalate prepared at a stirring speed of 200 r / min, Figure 1 b is the morphology diagram of ferrous oxalate prepared at a stirring speed of 100 r / min, Figure 1 c is the morphology diagram of ferrous oxalate prepared at a stirring speed of 150 r / min, Figure 1 d is the morphology diagram of ferrous oxalate prepared at a stirring speed of 0 r / min; from theFigure 1 It can be seen that when preparing ferrous oxalate without stirring, short and thick hexagonal prism-shaped ferrous oxalate is obtained; as the stirring speed increases, the ferrous oxalate becomes longer radially, then shorter and thinner. This is because the greater the stirring speed, the faster the reaction rate between C 2 O 4 2- and Fe 2+ , the number of ferrous oxalate crystal nuclei formed in a unit space increases, so the particle size of the prepared ferrous oxalate becomes smaller.

[0059] As shown in the appendix Figure 2 , the appendix Figure 2 shows the morphology diagrams of the ferrous oxalate prepared in Examples 5 - 8; among them, Figure 2 a is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 75 °C, Figure 2 b is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 80 °C, Figure 2 c is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 85 °C, Figure 2 d is the morphology diagram of the ferrous oxalate prepared at a reduction temperature of 95 °C; it can be seen from the appendix Figure 2 that the higher the reduction temperature, the larger the particle size, but the agglomeration phenomenon is alleviated. This is because although the reaction rate between C 2 O 4 2- and Fe 3+ increases, the number of ferrous oxalate crystal nuclei generated increases, that is, the rate of forming crystal nuclei is large, but the growth rate of ferrous oxalate is greater than its nucleation rate, so the particle size of ferrous oxalate becomes larger.

[0060] As shown in the appendix Figure 3 , the appendix Figure 3 shows the morphology diagrams of the ferrous oxalate prepared in Examples 9 - 12; among them, Figure 3 a is the morphology diagram of the ferrous oxalate prepared when the mass-volume ratio of ammonium ferric oxalate to water is 5 g:40 mL, Figure 3 b is the morphology diagram of the ferrous oxalate prepared when the mass-volume ratio of ammonium ferric oxalate to water is 5 g:50 mL, Figure 3 c is the morphology diagram of the ferrous oxalate prepared when the mass-volume ratio of ammonium ferric oxalate to water is 5 g:70 mL, Figure 3 d is the morphology diagram of the ferrous oxalate prepared when the mass-volume ratio of ammonium ferric oxalate to water is 5 g:80 mL; it can be seen from the appendix Figure 3 that the smaller the mass-volume ratio of ammonium ferric oxalate to water, the lower the concentration of (Fe 3+ ) TOT in the raw material liquid, the fewer the number of ferrous oxalate crystal nuclei formed in a unit space, and the crystal growth rate of ferrous oxalate is greater than its nucleation rate, so the particle size of the prepared ferrous oxalate becomes larger.

[0061] As shown in the Figure 4 accompanying Figure 4 drawings, the morphology diagrams of ferrous oxalate prepared in Examples 1, 18 - 19 are given; among them, Figure 4 a is the morphology diagram of ferrous oxalate prepared with a reduction time of 60 min, Figure 4 b is the morphology diagram of ferrous oxalate prepared with a reduction time of 20 min, Figure 4 c is the morphology diagram of ferrous oxalate prepared with a reduction time of 40 min; it can be seen from the Figure 4 accompanying drawings that the shorter the reduction time, the fewer the number of ferrous oxalate crystal nuclei formed, so the agglomeration of the prepared ferrous oxalate particles is less; as the reduction time is prolonged, ascorbic acid is more fully reduced, the number of ferrous oxalate crystal nuclei formed increases, the particle size of ferrous oxalate becomes smaller, the specific surface area is large, and the agglomeration phenomenon is serious; but further prolonging the reduction time, the ferrous oxalate crystal nuclei grow and the particle size becomes larger.

[0062] As shown in the Figure 5 accompanying Figure 5 drawings, the morphology diagrams of ferrous oxalate prepared in Examples 1, 21 - 23 are given; among them, Figure 5 a is the morphology diagram of ferrous oxalate prepared at a pH of 2.85, Figure 5 b is the morphology diagram of ferrous oxalate prepared at a pH of 3.70, Figure 5 c is the morphology diagram of ferrous oxalate prepared at a pH of 4.70; Figure 5 d is the morphology diagram of ferrous oxalate prepared at a pH of 5.80; it can be seen from the Figure 5 accompanying drawings that the larger the initial pH, the more ferrous oxalate crystal nuclei are formed, the smaller the particle size, the larger the specific surface area, the stronger the surface activity of ferrous oxalate, and the more serious the agglomeration phenomenon.

[0063] In the present invention, ammonium ferrioxalate or sodium ferrioxalate prepared from the leaching solution of cyanide tailings is used to replace the traditional inorganic Fe 2+ or Fe 3+ iron source and the precipitants oxalic acid, ammonium oxalate or sodium oxalate, and vitamin C is used to reduce ammonium ferrioxalate or sodium ferrioxalate prepared from the leaching solution of cyanide tailings to prepare ferrous oxalate; among them, the strong reducibility of vitamin C is used to reduce the Fe 2 complexed with C 4 2- in ammonium ferrioxalate to 3+ Fe 2+ , and Fe 2+ then reacts with the released C 2 O 4 2- to generate ferrous oxalate; ammonium ferrioxalate plays a role in providing the Fe 3+ source and C 2 O 42- Function of the precipitating ion; using ferric oxalate as the Fe 3+ source, and reducing Fe in ferric oxalate with vitamin C 3+ in the process of preparing ferrous oxalate, releasing C 3+ complexed with Fe 2 O 4 2- ; among them, C 2 O 4 2- In addition to participating in the reaction of forming ferrous oxalate with Fe 2+ it also exists in the reduced solution in the form of oxalate.

[0064] The preparation method of ferrous oxalate described in the present invention has a simple preparation process and does not require the purchase of inorganic Fe 2+ or Fe 3+ source and precipitants such as oxalic acid, ammonium oxalate or sodium oxalate, reducing the preparation cost of ferrous oxalate, and not generating high-salt wastewater, which is a clean technology for preparing ferrous oxalate; and the prepared ferrous oxalate does not contain Cl - or SO 4 2- , with high product quality; recovering ammonium oxalate or sodium oxalate and 2,3-diketo-L-guluronic acid from the reduced solution, the recovery of ammonium oxalate or sodium oxalate regenerates the iron-removing reagents ammonium oxalate or sodium oxalate, reducing the reagent cost in the iron-removing process of cyanide tailings, and 2,3-diketo-L-guluronic acid is also an important chemical product; the recovery of the antisolvent absolute ethanol also reduces the preparation cost of ferrous oxalate.

[0065] The above embodiments are only one of the implementation manners capable of implementing the technical solution of the present invention. The scope of protection required by the present invention is not only limited by this embodiment, but also includes any changes, substitutions and other implementation manners that are easily conceivable by those skilled in the art within the technical scope disclosed by the present invention.

Claims

1. A method for preparing ferrous oxalate, characterized in that: Ferrous oxalate is prepared using ferric oxalate prepared from cyanide tailings leaching solution as a raw material; wherein the cyanide tailings leaching solution is the leaching solution produced in the process of removing iron and enriching gold from the cyanide tailings.

2. A method for preparing ferrous oxalate according to claim 1, characterized in that, The process of preparing ferrous oxalate using ferric oxalate prepared from cyanide tailings leaching solution as raw material includes: Dissolving ferric oxalate in water to obtain a raw material solution; Adding a reducing agent to the raw material liquid, performing a stirring reduction reaction, and performing liquid-solid separation after the reaction is completed to obtain a reduction product and a reduced liquid; wherein the reduction product is ferrous oxalate; adding a dissolving agent to the reduced liquid to perform dissolving and crystallizing to obtain a dissolving and crystallizing liquid; Performing liquid-solid separation on the precipitated crystallization liquid to obtain oxalate crystals and crystallization mother liquor; The crystallization mother liquor is subjected to rectification treatment to obtain a tower top product and a tower bottom product.

3. A method for preparing ferrous oxalate according to claim 2, characterized in that, The reducing agent is vitamin C; the ferric oxalate is ammonium ferric oxalate or sodium ferric oxalate.

4. A method for preparing ferrous oxalate according to claim 2, characterized in that, A reducing agent is added to the raw material liquid, and during the stirring reduction reaction, the reduction temperature is 75-95° C., the reduction time is 20-60 min, and the stirring speed is 0-200 r / min.

5. A method for preparing ferrous oxalate according to claim 2, characterized in that, The solvent is anhydrous ethanol.

6. The method for preparing ferrous oxalate according to claim 5, characterized in that: The temperature of dissolution crystallization is 10-20°C.

7. The method for preparing ferrous oxalate according to claim 5, characterized in that: The top product is gaseous anhydrous ethanol; the bottom product is 2,3-diketo-L-gulonic acid.

8. A method for preparing ferrous oxalate according to claim 2, characterized in that, Oxalate crystals are sodium oxalate or ammonium oxalate.

9. A method for preparing ferrous oxalate according to claim 2, characterized in that, The preparation process of ferric oxalate from cyanide tailings leaching solution is as follows: The cyanide tailings leaching solution is evaporated, concentrated, cooled and crystallized, redissolved, evaporated twice, concentrated twice, and cooled and crystallized twice to obtain ferric oxalate.

10. The method for preparing ferrous oxalate according to claim 2, characterized in that: The mass volume ratio of ferric oxalate to water in the raw material solution is 5g:(40-80)mL.

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