Method for recovering valuable metals from sulfuric acid process titanium dioxide waste acid by treating steel slag

Abstract

The invention provides a method for recovering valuable metals from sulfuric acid process titanium white waste acid through steel slag treatment. The method comprises the following steps: recovering to obtain ferrous sulfate heptahydrate crystals; s2, recovering Sc metal, and extracting the filtrate in the step S1 to obtain a first loaded organic phase and a first raffinate; the first loaded organic phase is washed with alkali liquor, and a second loaded organic phase and washing water are obtained through reverse extraction; treating the washing water to obtain titanium phosphate; back-extracting the second loaded organic phase by using alkali liquor, carrying out filter pressing to obtain crude Sc (OH) 3, and refining to obtain scandium oxide; extracting the first raffinate to obtain a third loaded organic phase and a second raffinate, pickling the third loaded organic phase, reversely extracting with ammonia water, adding phosphoric acid for reaction, and treating to obtain titanium phosphate; and steel slag is added into the second raffinate for neutralization leaching and hydrolysis vanadium precipitation, vanadium-rich slag is obtained through filtering, and then the vanadium electrolyte is prepared. According to the method, iron is separated through crystallization, scandium and titanium are separated through extraction, vanadium-rich slag is separated through neutralization and precipitation, and efficient utilization of resources is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste and waste liquid treatment, and more particularly to a method for recovering valuable metals from waste acid in the treatment of steel slag by sulfuric acid process for titanium dioxide production. Background Art

[0002] Titanium dioxide (TiO2) is widely used in many industrial productions by humans due to its excellent performance, such as pigments, ceramic opacifiers, glass soldering aids, cosmetics, plastics, inks, and rubbers. In industry, there are two methods for producing titanium dioxide: the chlorination method and the sulfuric acid method. Due to the abundant and easily available raw materials and simple process, the sulfuric acid method is adopted by many titanium dioxide enterprises.

[0003] The production process of sulfuric acid process titanium dioxide will produce waste acid containing about 20% H2SO4. In the sulfuric acid process, every 1t of titanium dioxide produced will by-product about 8t of waste sulfuric acid with a concentration of about 20%. At present, the treatment methods of titanium white waste acid mainly include the neutralization method and the comprehensive recovery method. The neutralization method is to carry out a neutralization reaction between waste acid and alkaline substances such as limestone and carbide slag to achieve the treatment purpose. This method not only cannot separate and recover sulfuric acid and many valuable metals such as scandium, vanadium, titanium, and iron in the waste acid, but also produces titanium gypsum mainly composed of calcium sulfate and other solid wastes, and large-scale adoption is not recommended.

[0004] China is rich in vanadium-titanium magnetite resources, which are mainly distributed in Panxi, Sichuan and Chengde, Hebei regions, especially the Panxi vanadium-titanium magnetite resources are the most abundant. Vanadium-containing steel slag is produced in the steel-making process of vanadium-titanium magnetite, and its main sources are two: on the one hand, a certain amount of vanadium remains in the semi-steel when vanadium is extracted from vanadium-containing hot metal by a converter. After the semi-steel is blown, vanadium is oxidized into the slag; on the other hand, when the vanadium-containing hot metal is directly blown into steel without blowing vanadium slag, vanadium is oxidized and enters the slag. The typical characteristics of vanadium-containing steel slag are high contents of CaO and iron, and low vanadium content of about 1-5% wt.

[0005] At present, the recovery of vanadium from steel slag mainly adopts the wet vanadium extraction process and the direct acid leaching vanadium extraction process. In the wet vanadium extraction process, low-valent vanadium is converted into pentavalent water-soluble vanadium-containing sodium salt through oxidative roasting, and then through processes such as leaching, vanadium precipitation, and roasting, V2O5 is obtained. In the roasting process, corrosive gases such as Cl2, SO2, and HCl are often generated, causing environmental pollution. At the same time, the roasting temperature is relatively high and the energy consumption is large. The advantage of the direct acid leaching vanadium extraction process is that the vanadium leaching rate and recovery rate are high. However, due to the high content of CaO in vanadium-containing steel slag, the acid consumption is large and the cost is high. In addition, in a strong acid solution, various components in the steel slag will be dissolved, resulting in more impurities in the leaching solution, and a suitable method still needs to be selected to purify and recover vanadium from the steel slag.

[0006] In the current research on leaching steel slag with titanium white waste acid, the sulfuric acid waste acid is neutralized by steel slag and vanadium is recovered, but more emphasis is placed on the leaching of vanadium, while less attention is paid to other metal resources such as titanium, scandium, and iron in the waste acid, making it difficult to achieve the efficient utilization of various valuable metals in titanium white waste acid and steel slag.

[0007] In view of this, the present invention is specifically proposed. Summary of the Invention

[0008] The object of the present invention is to provide a method for treating sulfuric acid process titanium white waste acid with steel slag to recover valuable metals, which uses crystallization to separate iron, extraction to separate scandium and titanium, and neutralization precipitation to separate vanadium-rich slag, so as to achieve the efficient utilization of resources.

[0009] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0010] A method for treating sulfuric acid process titanium white waste acid with steel slag to recover valuable metals, comprising the following steps:

[0011] Step S1, recovering Fe metal in sulfuric acid process titanium white waste acid: cooling and crystallizing, and filtering to obtain ferrous sulfate heptahydrate crystals;

[0012] Step S2, recovering Sc metal in the filtrate of Step S1, comprising the following steps:

[0013] Step S2.1, extracting Sc: extracting Ti and Sc in the filtrate of Step S1 to obtain a first loaded organic phase loaded with Ti and Sc and a first raffinate; Step S2.2, washing Ti: washing the first loaded organic phase with an alkaline solution to perform back-extraction to obtain a second loaded organic phase and washing water; heating, filtering, drying, and calcining the washing water to obtain titanium phosphate; Step S2.3, recovering Sc: performing back-extraction on the second loaded organic phase with an alkali solution, and obtaining crude Sc(OH)3 after pressure filtration, and refining the crude Sc(OH)3 to obtain scandium oxide;

[0014] Step S3, recovering Ti metal in the first raffinate of Step S2.1: extracting the first raffinate to obtain a third loaded organic phase and a second raffinate, pickling the third loaded organic phase, performing back-extraction with ammonia water, adding phosphoric acid for reaction, and obtaining titanium phosphate after heating, filtering, drying, and calcining;

[0015] Step S4, recovering V metal by neutralizing the second raffinate with steel slag: adding steel slag to the second raffinate for neutralization leaching to recover vanadium in the steel slag, adjusting the first leaching solution to acidic hydrolysis and vanadium precipitation with liquid alkali, filtering to obtain vanadium-rich slag, and preparing vanadium electrolyte from the vanadium-rich slag.

[0016] Further, in step S2.1, the extractant P204 + TBP + kerosene is used for multi-stage countercurrent extraction of Ti and Sc in the filtrate of step S1; in step S2.2, a Na3PO4 + H2O2 solution with a pH of 11 to 11.5 is used to wash the first loaded organic phase, with O / A = 1:1 to 1:3, and countercurrent stripping is performed multiple times.

[0017] Further, in step S3, the first raffinate is subjected to multi-stage countercurrent extraction with the extractant N1923 or the extractant N1923 + TBP + kerosene according to O / A = 1:1 to 1:3 to obtain a third loaded organic phase and a second raffinate, and the third loaded organic phase is washed with sulfuric acid with a pH of 1.5 to 2.5 in multiple stages.

[0018] Further, in step S4, steel slag is added to the second raffinate according to a solid-liquid ratio of 1:(6 to 9), and neutralization leaching is carried out for 1 to 4 h to recover vanadium in the steel slag, and the first leaching solution is adjusted to a pH of 2 to 3 with liquid alkali for hydrolysis and vanadium precipitation.

[0019] Further, in step S2.3, the refining process of crude Sc(OH)3 is as follows: the crude Sc(OH)3 is acid-dissolved, oxalic acid is added to the filtrate after filtration for scandium precipitation, and after filtration, it is washed with water to obtain scandium oxalate, and scandium oxalate is calcined to obtain scandium oxide.

[0020] Further, the crude Sc(OH)3 is acid-dissolved with nitric acid, the filtrate is heated to 70 to 100 °C after filtration, and oxalic acid 1.2 to 1.4 times the theoretical amount of scandium oxide is added for scandium precipitation, and after filtration, it is washed with pure water according to a solid-liquid ratio of 1:(1.2 to 1.5).

[0021] Further, step S4 also includes slurrying the vanadium-rich slag, adding sodium chlorate for slurrying oxidation, leaching with an alkali solution and filtering to obtain an alkali leaching solution and a leaching residue; adding sodium sulfite to the alkali leaching solution, adjusting it to acidic with sulfuric acid, and then performing extraction to obtain a fourth loaded organic phase; washing the fourth loaded organic phase loaded with vanadium with sulfuric acid, and after washing, performing back-extraction of the fourth loaded organic phase with sulfuric acid to obtain a back-vanadium solution, and after removing oil from the back-vanadium solution through resin, electrolysis is carried out to obtain a vanadium electrolyte.

[0022] Further, the leaching residue is leached with a NaOH solution for 1 to 4 h, filtered to obtain a secondary leaching solution, and NaOH is added to the secondary leaching solution for another leaching, and then it is mixed into the alkali leaching solution.

[0023] Further, the vanadium-rich slag is slurried with water at a solid-liquid ratio of 1:(1-2), and sodium chlorate 1.2-1.4 times the theoretical amounts of Fe and V is added for slurry oxidation for 0.5-1 h. Then, it is leached with NaOH solution at a solid-liquid ratio of 1:(2-4) for 1-4 h, and the alkaline leaching solution is obtained by filtration. Sodium sulfite 1.2-1.4 times the theoretical amount of V2O5 is added to the alkaline leaching solution, and after adjusting the pH to 1-1.5 with sulfuric acid, multi-stage countercurrent extraction is carried out with P204 or P204+TBP+kerosene at an O / A ratio of 3:1-1:1 to obtain the fourth loaded organic phase. The fourth loaded organic phase loaded with vanadium is washed by cross-flow with sulfuric acid at pH 1.5-2.5 at an O / A ratio of 3:1-1:1 for multiple times, and after washing, the fourth loaded organic phase is stripped by cross-flow with sulfuric acid solution at an O / A ratio of 12:1-9:1 for multiple times to obtain the vanadium-containing solution.

[0024] Further, in step S1, the spent acid from sulfuric acid process titanium dioxide is cooled by 3-9 °C for 1-7 h, and stirred at a speed of 30-60 rpm during cooling, and then ferrous sulfate heptahydrate crystals are obtained by filtration.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) The method for treating the spent acid from sulfuric acid process titanium dioxide with steel slag to recover valuable metals of the present invention uses crystallization to separate iron, extraction to separate scandium and titanium, and neutralization precipitation to separate vanadium-rich slag, and then uses the vanadium-rich slag to prepare vanadium electrolyte, which can take into account the recovery of iron, scandium, titanium, vanadium in the spent acid from titanium dioxide and vanadium in steel slag. The recovery rates of various valuable metals are high, realizing the efficient utilization of resources.

[0027] (2) The method for treating the spent acid from sulfuric acid process titanium dioxide with steel slag to recover valuable metals of the present invention first recovers iron, titanium and scandium in the spent acid from sulfuric acid process, and then uses steel slag to neutralize and treat the raffinate. The vanadium content in the spent acid from sulfuric acid process titanium dioxide is 200-300 mg / L. The present invention can simultaneously recover vanadium in the spent acid from titanium dioxide and steel slag and prepare it into vanadium electrolyte, effectively purifying and recovering vanadium from the spent acid from titanium dioxide and steel slag. The vanadium content in the vanadium electrolyte for recovering vanadium metal is high and the content of impurity elements is low, meeting the national first-class product standard, realizing the efficient recovery and utilization of valuable metals in the spent acid from sulfuric acid process and steel slag.

[0028] (3) The method for treating the spent acid from sulfuric acid process titanium dioxide with steel slag to recover valuable metals of the present invention can treat a large amount of spent acid from titanium dioxide, realizing the resource utilization of the spent acid from sulfuric acid process titanium dioxide. It can not only effectively avoid the occurrence of environmental hazard events, but also relieve the resource pressure and ensure the economic benefits of enterprises to a certain extent, which is of great significance to the sustainable and efficient development of the titanium dioxide industry.

[0029] (4) The method for treating the spent acid from sulfuric acid process titanium dioxide with steel slag to recover valuable metals of the present invention uses waste steel slag as raw material, greatly reducing the raw material cost in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Figure 1 It is a process flow diagram for recovering valuable metals from the waste acid of sulfuric acid process titanium dioxide by treating steel slag in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following will clearly and completely describe the technical solutions of the present invention in combination with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0033] A method for recovering valuable metals from the waste acid of sulfuric acid process titanium dioxide by treating steel slag includes the following steps:

[0034] Step S1: Recover Fe metal in the waste acid of sulfuric acid process titanium dioxide: Cool the waste acid of sulfuric acid process titanium dioxide by 3 - 9°C, including but not limited to 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, and the cooling time is 1 - 7h, including but not limited to 1h, 2h, 3h, 4h, 5h, 6h, 7h. While cooling, stir at a speed of 30 - 60 rpm, and the stirring speed includes but not limited to 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, and filter to obtain ferrous sulfate heptahydrate crystals;

[0035] Step S2: Recover Sc metal in the filtrate of Step S1, including the following steps:

[0036] Step S2.1: Extract Sc: Use the extractant P204 + TBP + kerosene, preferably 15% P204 + 5% TBP + 80% kerosene, and perform multi-stage countercurrent extraction on Ti and Sc in the filtrate of Step S1. The multi-stage includes but not limited to two-stage, three-stage, four-stage, five-stage, to obtain the first loaded organic phase loaded with Ti and Sc and the first raffinate. The extraction rate of Sc is 90%, and the extraction rate of Ti is more than 20%;

[0037] It should be noted that in this text, P204 is bis(2-ethylhexyl) phosphate and TBP is tributyl phosphate;

[0038] Step S2.2, washing Ti: Wash the first loaded organic phase with a Na3PO4 + H2O2 solution (nP / nTi = 2 / 1; nH2O2 / nTi = 3 / 1) with a pH of 11 to 11.5. The pH value includes but is not limited to 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, O / A = 1:1 to 1:3. O / A includes but is not limited to 1:1, 1:2, 1:3. Perform countercurrent stripping multiple times. Multiple times includes but is not limited to two, three, four, five times, to obtain a second loaded organic phase and washing water. The stripping efficiency of Ti is greater than 98%, and the stripping efficiency of Sc is less than 5%. Heat the washing water at 120 °C, filter, dry, and calcine at 450 °C to obtain titanium phosphate;

[0039] Step S2.3, recovering Sc: Use 4 mol / L NaOH to strip the second loaded organic phase. After pressure filtration, obtain crude Sc(OH)3. Dissolve the crude Sc(OH)3 with 1 mol / L nitric acid. After filtration, heat the filtrate to 70 to 100 °C, including but not limited to 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C. Add oxalic acid 1.2 to 1.4 times the theoretical amount of scandium oxide for scandium precipitation. The multiple includes but is not limited to 1.2, 1.25, 1.3, 1.35, 1.4. After filtration, wash with pure water according to a solid-liquid ratio of 1:(1.2 to 1.5). The solid-liquid ratio includes but is not limited to 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.5 to obtain scandium oxalate. Calcinate the scandium oxalate at 800 °C for 1 h to obtain scandium oxide;

[0040] Step S3, recovering Ti metal in the first raffinate: Use extractant N1923 or extractant N1923 + TBP + kerosene, preferably 20% N1923 + 5% TBP + 75% kerosene, to perform multi-stage countercurrent extraction on the first raffinate according to O / A = 1:1 to 1:3. O / A includes but is not limited to 1:1, 1:2, 1:3. Multi-stage includes but is not limited to two-stage, three-stage, four-stage, five-stage, to obtain a third loaded organic phase and a second raffinate. Wash the third loaded organic phase three times with sulfuric acid with a pH of 1.5 to 2.5. The pH value includes but is not limited to 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5. Use 1 mol / L ammonia water for stripping. Add phosphoric acid (nP / nTi = 2 / 1) to the stripping solution for reaction. After heating at 120 °C, filtering, drying, and calcining at 450 °C, obtain titanium phosphate;

[0041] It should be noted that in this text, N1923 is secondary carbon primary amine;

[0042] Step S4, neutralizing the second raffinate with steel slag and recovering V metal: Add steel slag to the second raffinate at a solid-liquid ratio of 1:(6-9). The solid-liquid ratio includes, but is not limited to, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9. Carry out neutralization leaching for 1-4 h to recover vanadium in the steel slag. The neutralization leaching time includes, but is not limited to, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, to obtain a first leaching solution with a vanadium leaching rate of 90%. Adjust the pH of the first leaching solution to 2-3 with liquid caustic soda for hydrolysis and vanadium precipitation. The pH value includes, but is not limited to, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3. The vanadium precipitation rate is 95%. Filter to obtain vanadium-rich slag (V2O5 content 10-15%);

[0043] The vanadium-rich slag is slurried with water at a solid-liquid ratio of 1:(1-2), and the solid-liquid ratio includes but is not limited to 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2. Sodium chlorate 1.2-1.4 times the theoretical amounts of Fe and V is added for slurry oxidation for 0.5-1 h. The multiple includes but is not limited to 1.2, 1.25, 1.3, 1.35, 1.4, and the slurry oxidation time includes but is not limited to 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h. It is leached with 4 mol / L NaOH at 90 °C at a solid-liquid ratio of 1:(2-4) for 1-4 h. The solid-liquid ratio includes but is not limited to 1:2, 1:2.5, 1:3, 1:3.5, 1:4, and the leaching time includes but is not limited to 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h. The alkali leaching solution is obtained by filtration; the leaching residue is leached with 5 mol / L NaOH for 1-4 h, including but not limited to 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, and the secondary leaching solution is obtained by filtration; NaOH is added to the secondary leaching solution for another leaching and mixed into the alkali leaching solution, and the leaching rate of vanadium can reach over 95%; Sodium sulfite 1.2-1.4 times the theoretical amount of V2O5 is added to the alkali leaching solution. The multiple includes but is not limited to 1.2, 1.25, 1.3, 1.35, 1.4. After adjusting the pH to 1-1.5 with sulfuric acid, the pH value includes but is not limited to 1, 1.1, 1.2, 1.3, 1.4, 1.5. Using p204 or P204+TBP+kerosene, preferably 20% P204+5% TBP+75% kerosene, multi-stage countercurrent extraction is carried out according to O / A = 3:1-1:1. O / A includes but is not limited to 3:1, 2.5:1, 2:1, 1.5:1, 1:1 to obtain the fourth loaded organic phase; the fourth loaded organic phase loaded with vanadium is washed by cross-flow with sulfuric acid at pH 1.5-2.5 according to O / A = 3:1-1:1 for multiple times. O / A includes but is not limited to 3:1, 2:1, 1:1, and the pH value includes but is not limited to 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4. Multiple times includes but is not limited to two, three, four, five times. After washing, the fourth loaded organic phase is stripped by cross-flow with 5 mol / L sulfuric acid according to O / A = 12:1-9:1 for multiple times. O / A includes but is not limited to 12:1, 11:1, 10:1, 9:1 to obtain the stripped vanadium solution. The stripped vanadium solution is electrolyzed after resin degreasing to obtain the vanadium electrolyte.

[0044] Example 1

[0045] A method for recovering valuable metals from the waste acid of sulfuric acid process titanium white in steel slag treatment, comprising the following steps:

[0046] Step S1: Recover Fe metal from the waste acid of sulfuric acid process titanium white: Cool the waste acid of sulfuric acid process titanium white by 3°C for 1 hour, and stir it at a speed of 30 rpm while cooling. Filter to obtain ferrous sulfate heptahydrate crystals.

[0047] Step S2: Recover Sc metal from the filtrate of Step S1, including the following steps:

[0048] Step S2.1: Extract Sc: Use 15% P204 + 5% TBP + 80% kerosene for three-stage countercurrent extraction of Ti and Sc in the filtrate of Step S1 to obtain the first loaded organic phase loaded with Ti and Sc and the first raffinate. The extraction rate of Sc is 90%, and the extraction rate of Ti is more than 20%.

[0049] Step S2.2: Wash Ti: Wash the first loaded organic phase with a solution of Na3PO4 + H2O2 (nP / nTi = 2 / 1; nH2O2 / nTi = 3 / 1) with a pH of 11, O / A = 1:1, and perform countercurrent stripping three times to obtain the second loaded organic phase and washing water. The stripping efficiency of Ti is greater than 98%, and the stripping efficiency of Sc is less than 5%. Heat the washing water at 120°C, filter, dry, and calcine at 450°C to obtain titanium phosphate.

[0050] Step S2.3: Recover Sc: Use 4 mol / L NaOH to strip the second loaded organic phase. After pressure filtration, obtain crude Sc(OH)3. Dissolve the crude Sc(OH)3 with 1 mol / L nitric acid. After filtration, heat the filtrate to 70°C, add oxalic acid 1.2 times the theoretical amount of scandium oxide for scandium precipitation. After filtration, wash with pure water according to a solid-liquid ratio of 1:1.2 to obtain scandium oxalate. Scandium oxalate is calcined at 800°C for 1 hour to obtain scandium oxide.

[0051] Step S3: Recover Ti metal from the first raffinate: Use N1923 to perform three-stage countercurrent extraction on the first raffinate according to O / A = 1:1 to obtain the third loaded organic phase and the second raffinate. Wash the third loaded organic phase three times with sulfuric acid with a pH of 1.5, and strip it with 1 mol / L ammonia water. The stripping solution is reacted with phosphoric acid (nP / nTi = 2 / 1), heated at 120°C, filtered, dried, and calcined at 450°C to obtain titanium phosphate.

[0052] Step S4: Neutralize the second raffinate with steel slag to recover V metal: Add steel slag to the second raffinate according to a solid-liquid ratio of 1:6, and perform neutralization leaching for 1 hour to recover vanadium in the steel slag to obtain the first leaching solution with a vanadium leaching rate of 90%. Adjust the pH of the first leaching solution to 2 with liquid caustic soda for vanadium hydrolysis precipitation, with a vanadium precipitation rate of 95%. Filter to obtain vanadium-rich slag (V2O5 content 10 - 15%).

[0053] The vanadium-rich slag is slurried with water at a solid-liquid ratio of 1:1, and sodium chlorate 1.2 times the theoretical amounts of Fe and V is added for slurry oxidation for 0.5 h. It is leached with 4 mol / L NaOH at 90 °C at a solid-liquid ratio of 1:2 for 1 h, and the alkaline leaching solution is obtained by filtration; sodium sulfite 1.2 times the theoretical amount of V2O5 is added to the alkaline leaching solution. After adjusting the pH to 1 with sulfuric acid, P204 is used for three-stage countercurrent extraction at O / A = 1.5:1 to obtain the fourth loaded organic phase; the fourth loaded organic phase loaded with vanadium is washed three times by cross-flow with sulfuric acid at pH 1.5 at O / A = 2:1. After washing, the fourth loaded organic phase is countercurrent stripped three times with 5 mol / L sulfuric acid at O / A = 10:1 to obtain a vanadium stripping solution. The vanadium stripping solution is electrolyzed after removing oil by resin to obtain a vanadium electrolyte solution.

[0054] Example 2

[0055] A method for recovering valuable metals from the waste acid of sulfuric acid process titanium dioxide using steel slag treatment, comprising the following steps:

[0056] Step S1, recovering Fe metal from the waste acid of sulfuric acid process titanium dioxide: The waste acid of sulfuric acid process titanium dioxide is cooled by 5 °C for 3 h while stirring at a speed of 40 rpm, and ferrous sulfate heptahydrate crystals are obtained by filtration;

[0057] Step S2, recovering Sc metal from the filtrate of Step S1, comprising the following steps:

[0058] Step S2.1, extracting Sc: Using 15% P204 + 5% TBP + 80% kerosene, three-stage countercurrent extraction of Ti and Sc in the filtrate of Step S1 to obtain the first loaded organic phase loaded with Ti and Sc and the first raffinate. The extraction rate of Sc is 90%, and the extraction rate of Ti is more than 20%;

[0059] Step S2.2, washing Ti: Using a solution of Na3PO4 + H2O2 (nP / nTi = 2 / 1; nH2O2 / nTi = 3 / 1) with a pH of 11.2 to wash the first loaded organic phase, and countercurrent stripping is carried out three times to obtain the second loaded organic phase and washing water. The stripping efficiency of Ti is greater than 98%, and the stripping efficiency of Sc is less than 5%; The washing water is heated at 120 °C, filtered, dried, and calcined at 450 °C to obtain titanium phosphate;

[0060] Step S2.3, recovering Sc: Using 4 mol / L NaOH to strip the second loaded organic phase, and after pressure filtration, crude Sc(OH)3 is obtained. The crude Sc(OH)3 is acid-dissolved with 1 mol / L nitric acid, and after filtration, the filtrate is heated to 80 °C, and oxalic acid 1.3 times the theoretical amount of scandium oxide is added for scandium precipitation. After filtration, it is washed with pure water at a solid-liquid ratio of 1:1.3 to obtain scandium oxalate. Scandium oxalate is calcined at 800 °C for 1 h to obtain scandium oxide;

[0061] Step S3: Recovering Ti metal from the first raffinate: The first raffinate is subjected to three-stage countercurrent extraction with 20% N1923 + 5% TBP + 75% kerosene at an O / A ratio of 1:1 to obtain the third loaded organic phase and the second raffinate. The third loaded organic phase is washed three times with sulfuric acid at pH 2 and then stripped with 1 mol / L ammonia water. The stripping solution is reacted with phosphoric acid (nP / nTi = 2 / 1), heated at 120 °C, filtered, dried, and calcined at 450 °C to obtain titanium phosphate;

[0062] Step S4: Neutralizing the second raffinate with steel slag and recovering V metal: Steel slag is added to the second raffinate at a solid-liquid ratio of 1:7, and neutralization leaching is carried out for 2 h to recover vanadium from the steel slag, obtaining a first leaching solution with a vanadium leaching rate of 90%. The pH of the first leaching solution is adjusted to 2 with liquid caustic soda for hydrolysis vanadium precipitation, and the vanadium precipitation rate is 95%. After filtration, a vanadium-rich slag (V2O5 content 10 - 15%) is obtained;

[0063] The vanadium-rich slag is slurried with water at a solid-liquid ratio of 1:1, and sodium chlorate 1.3 times the theoretical amount of Fe and V is added for slurry oxidation for 0.7 h. It is leached with 4 mol / L NaOH at 90 °C at a solid-liquid ratio of 1:3 for 2 h, and the leaching solution is filtered to obtain an alkaline leaching solution. The leaching residue is leached with 5 mol / L NaOH for 2 h, and the secondary leaching solution is filtered. The secondary leaching solution is supplemented with NaOH for re-leaching and mixed with the alkaline leaching solution. The leaching rate of vanadium after multiple leaching can reach over 95%. Sodium sulfite 1.3 times the theoretical amount of V2O5 is added to the alkaline leaching solution, and the pH is adjusted to 1.2 with sulfuric acid. Then, three-stage countercurrent extraction is carried out with 20% P204 + 5% TBP + 75% kerosene at an O / A ratio of 1.5:1 to obtain the fourth loaded organic phase. The fourth loaded organic phase loaded with vanadium is washed three times by cross-flow with sulfuric acid at pH 1.8 at an O / A ratio of 2:1. After washing, the fourth loaded organic phase is stripped three times by cross-flow with 5 mol / L sulfuric acid at an O / A ratio of 10:1 to obtain a vanadium stripping solution. The vanadium stripping solution is electrolyzed after resin degreasing to obtain vanadium electrolyte.

[0064] Example 3

[0065] A method for treating steel slag and recovering valuable metals from sulfuric acid process titanium white waste acid, comprising the following steps:

[0066] Step S1: Recovering Fe metal from sulfuric acid process titanium white waste acid: The sulfuric acid process titanium white waste acid is cooled by 7 °C for 5 h while stirring at a speed of 50 rpm, and then filtered to obtain ferrous sulfate heptahydrate crystals;

[0067] Step S2: Recovering Sc metal from the filtrate of Step S1, comprising the following steps:

[0068] Step S2.1, extraction of Sc: Use 15% P204 + 5% TBP + 80% kerosene to perform three-stage countercurrent extraction on Ti and Sc in the filtrate of Step S1 to obtain the first loaded organic phase loaded with Ti and Sc and the first raffinate. The extraction rate of Sc is 90%, and the extraction rate of Ti is over 20%;

[0069] Step S2.2, washing of Ti: Wash the first loaded organic phase with a solution of Na3PO4 + H2O2 (nP / nTi = 2 / 1; nH2O2 / nTi = 3 / 1) with a pH of 11.3 for three times of countercurrent stripping to obtain the second loaded organic phase and washing water. The stripping efficiency of Ti is greater than 98%, and the stripping efficiency of Sc is less than 5%; Heat the washing water at 120°C, filter, dry, and calcine at 450°C to obtain titanium phosphate;

[0070] Step S2.3, recovery of Sc: Use 4 mol / L NaOH to strip the second loaded organic phase, and obtain crude Sc(OH)3 after pressure filtration. Dissolve the crude Sc(OH)3 with 1 mol / L nitric acid, heat the filtrate to 90°C after filtration, add oxalic acid which is 1.3 times the theoretical amount of scandium oxide for scandium precipitation, filter, and wash with pure water according to a solid-liquid ratio of 1:1.4 to obtain scandium oxalate. Calcinate the scandium oxalate at 800°C for 1 h to obtain scandium oxide;

[0071] Step S3, recovery of Ti metal in the first raffinate: Use N1923 to perform three-stage countercurrent extraction on the first raffinate according to O / A = 1:1 to obtain the third loaded organic phase and the second raffinate. Wash the third loaded organic phase three times with sulfuric acid with a pH of 2.2, strip with 1 mol / L ammonia water, add phosphoric acid (nP / nTi = 2 / 1) to the stripping solution for reaction, heat at 120°C, filter, dry, and calcine at 450°C to obtain titanium phosphate;

[0072] Step S4, neutralize the second raffinate with steel slag to recover V metal: Add steel slag to the second raffinate according to a solid-liquid ratio of 1:8, perform neutralization leaching for 3 h to recover vanadium in the steel slag, and obtain the first leaching solution with a vanadium leaching rate of 90%; Adjust the pH of the first leaching solution to 2.5 with liquid caustic soda for vanadium hydrolysis precipitation, with a vanadium precipitation rate of 95%, and filter to obtain vanadium-rich slag (V2O5 content 10 - 15%);

[0073] Slurry the vanadium-rich slag with water at a solid-liquid ratio of 1:1.6, add sodium chlorate at 1.3 times the theoretical amounts of Fe and V, and oxidize by pulping for 0.8 h. Leach at 90 °C with 4 mol / L NaOH at a solid-liquid ratio of 1:3.5 for 3 h, and filter to obtain an alkali leaching solution; leach the leaching residue with 5 mol / L NaOH for 4 h, and filter to obtain a secondary leaching solution; add NaOH to the secondary leaching solution for another leaching, mix it into the alkali leaching solution, and the leaching rate of vanadium can reach over 95%; add sodium sulfite at 1.3 times the theoretical amount of V2O5 to the alkali leaching solution, adjust the pH to 1.4 with sulfuric acid, and then perform three-stage countercurrent extraction with p204 at O / A = 1.5:1 to obtain a fourth loaded organic phase; wash the fourth loaded organic phase loaded with vanadium three times by cross-flow with sulfuric acid at pH 2.1 at O / A = 2:1. After washing, perform three-stage cross-flow stripping on the fourth loaded organic phase with 5 mol / L sulfuric acid at O / A = 10:1 to obtain a stripped vanadium solution. After removing oil from the stripped vanadium solution with resin, perform electrolysis to obtain a vanadium electrolyte solution.

[0074] Example 4

[0075] A method for recovering valuable metals from sulfuric acid process titanium white waste acid by treating steel slag includes the following steps:

[0076] Step S1, recovering Fe metal from sulfuric acid process titanium white waste acid: Cool the sulfuric acid process titanium white waste acid by 9 °C for 7 h, and stir at a speed of 60 rpm during cooling, then filter to obtain ferrous sulfate heptahydrate crystals;

[0077] Step S2, recovering Sc metal from the filtrate of Step S1, including the following steps:

[0078] Step S2.1, extracting Sc: Use 15% P204 + 5% TBP + 80% kerosene for three-stage countercurrent extraction of Ti and Sc in the filtrate of Step S1 to obtain a first loaded organic phase loaded with Ti and Sc and a first raffinate. The extraction rate of Sc is 90%, and the extraction rate of Ti is over 20%;

[0079] Step S2.2, washing Ti: Wash the first loaded organic phase with a solution of Na3PO4 + H2O2 (nP / nTi = 2 / 1; nH2O2 / nTi = 3 / 1) with a pH of 11.5, O / A = 1:1, and perform three-stage countercurrent stripping to obtain a second loaded organic phase and washing water. The stripping efficiency of Ti is greater than 98%, and the stripping efficiency of Sc is less than 5%; Heat the washing water at 120 °C, filter, dry, and calcine at 450 °C to obtain titanium phosphate;

[0080] Step S2.3, recovering Sc: The second loaded organic phase is back-extracted with 4 mol / L NaOH, and after pressure filtration, crude Sc(OH)3 is obtained. The crude Sc(OH)3 is acid-dissolved with 1 mol / L nitric acid. After filtration, the filtrate is heated to 100 °C, and oxalic acid 1.4 times the theoretical amount of scandium oxide is added for scandium precipitation. After filtration, it is washed with pure water according to a solid-liquid ratio of 1:1.5 to obtain scandium oxalate. The scandium oxalate is calcined at 800 °C for 1 h to obtain scandium oxide;

[0081] Step S3, recovering Ti metal from the first raffinate: The first raffinate is subjected to three-stage countercurrent extraction with N1923 according to O / A = 1:1 to obtain the third loaded organic phase and the second raffinate. The third loaded organic phase is washed three times with sulfuric acid at pH 2.5 and back-extracted with 1 mol / L ammonia water. The back-extracted solution is reacted with phosphoric acid (nP / nTi = 2 / 1), heated at 120 °C, filtered, dried, and calcined at 450 °C to obtain titanium phosphate;

[0082] Step S4, neutralizing the second raffinate with steel slag to recover V metal: Steel slag is added to the second raffinate according to a solid-liquid ratio of 1:9, and neutralization leaching is carried out for 4 h to recover vanadium in the steel slag, obtaining a first leaching solution with a vanadium leaching rate of 90%; The pH of the first leaching solution is adjusted to 3 with liquid caustic soda for vanadium hydrolysis precipitation, and the vanadium precipitation rate is 95%. After filtration, a vanadium-rich slag (V2O5 content 10 - 15%) is obtained;

[0083] The vanadium-rich slag is slurried with water according to a solid-liquid ratio of 1:2, and sodium chlorate 1.4 times the theoretical amount of Fe and V is added for slurry oxidation for 1 h. It is leached with 4 mol / L NaOH at 90 °C according to a solid-liquid ratio of 1:4 for 4 h, and the alkali leaching solution is obtained by filtration; Sodium sulfite 1.4 times the theoretical amount of V2O5 is added to the alkali leaching solution, and after adjusting the pH to 1.5 with sulfuric acid, three-stage countercurrent extraction is carried out with P204 according to O / A = 1.5:1 to obtain the fourth loaded organic phase; The fourth loaded organic phase loaded with vanadium is washed three times by cross-flow with sulfuric acid at pH 2.5 according to O / A = 2:1. After washing, the fourth loaded organic phase is back-extracted three times by cross-flow with 5 mol / L sulfuric acid according to O / A = 10:1 to obtain a vanadium-containing solution. The vanadium-containing solution is electrolyzed after removing oil by resin to obtain a vanadium electrolyte.

[0084] Test example:

[0085] I. In Examples 1 - 4, the recovery rates of Fe, Sc, Ti, and V metals in sulfuric acid process titanium white waste acid and steel slag are shown in Table 1:

[0086] Among them, the recovery rate of Fe metal = the amount of separated Fe ions / the content in titanium white waste acid * 100%, the recovery rate of Sc metal = the amount of separated Sc ions / the content in titanium white waste acid * 100%, the recovery rate of Ti metal = the amount of separated Ti ions / the content in titanium white waste acid * 100%, and the recovery rate of V metal = the amount of separated V ions / the content in (titanium white waste acid + steel slag) * 100%.

[0087] Table 1 Recovery rates of Fe, Sc, Ti, and V metals in Examples 1 - 4

[0088]

[0089] As can be seen from Table 1, the present invention can take into account the recovery of iron, scandium, titanium, and vanadium in titanium white waste acid and vanadium in steel slag, and achieve the synchronous and efficient recovery of valuable metals.

[0090] Second, the final product of vanadium recovery in the present invention is vanadium electrolyte. The vanadium content and impurity conditions in the vanadium electrolyte are shown in Table 2 as follows:

[0091] Table 2 Vanadium content and impurity element content in vanadium electrolyte in Examples 1 - 4

[0092]

[0093] As can be seen from Table 2, the vanadium electrolyte in the present invention has a high vanadium content and a low impurity element content, and can meet the national first-class product standard.

Claims

1. A method for recovering valuable metals from waste acid in titanium white production by sulfuric acid method with steel slag treatment, characterized in that, It includes the following steps: Step S1: Recover Fe metal from the waste acid of sulfuric acid process titanium white: Cool and crystallize, and filter to obtain ferrous sulfate heptahydrate crystals; Step S2: Recover Sc metal from the filtrate of Step S1, including the following steps: Step S2.1: Extract Sc: Extract Ti and Sc from the filtrate of Step S1 to obtain the first loaded organic phase loaded with Ti and Sc and the first raffinate; Step S2.2: Wash Ti: Wash the first loaded organic phase with an alkaline solution for back-extraction to obtain the second loaded organic phase and washing water; Heat, filter, dry, and calcine the washing water to obtain titanium phosphate; Step S2.3: Recover Sc: Back-extract the second loaded organic phase with an alkali solution, and obtain crude Sc(OH)3 after pressure filtration, and refine the crude Sc(OH)3 to obtain scandium oxide; Step S3: Recover Ti metal from the first raffinate of Step S2.1: Extract the first raffinate to obtain the third loaded organic phase and the second raffinate, acid-wash the third loaded organic phase, back-extract with ammonia water, add phosphoric acid for reaction, and obtain titanium phosphate after heating, filtering, drying, and calcining; Step S4: Neutralize the second raffinate with steel slag to recover V metal: Add steel slag to the second raffinate for neutralization leaching to recover vanadium in the steel slag, adjust the pH of the first leaching solution to acidic hydrolysis and vanadium precipitation with liquid caustic soda, filter to obtain vanadium-rich slag, and prepare vanadium electrolyte from the vanadium-rich slag.

2. The method for recycling valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 1, characterized in that, In Step S2.1, the extractant P204 + TBP + kerosene is used for multi-stage countercurrent extraction of Ti and Sc in the filtrate of Step S1; in Step S2.2, the first loaded organic phase is washed with a Na3PO4 + H2O2 solution with a pH of 11 - 11.5, O / A = 1:1 - 1:3, and countercurrent back-extraction is performed multiple times.

3. The method for recovering valuable metals from the waste acid of sulfuric acid process titanium white by treating steel slag according to claim 1 or 2, characterized in that, In Step S3, the first raffinate is subjected to multi-stage countercurrent extraction with the extractant N1923 or the extractant N1923 + TBP + kerosene according to O / A = 1:1 - 1:3 to obtain the third loaded organic phase and the second raffinate, and the third loaded organic phase is washed with sulfuric acid with a pH of 1.5 - 2.5 multiple times.

4. The method for recovering valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 1 or 2, characterized in that, In Step S4, steel slag is added to the second raffinate according to a solid-liquid ratio of 1:(6 - 9) for neutralization leaching for 1 - 4 h to recover vanadium in the steel slag, and the pH of the first leaching solution is adjusted to 2 - 3 with liquid caustic soda for hydrolysis and vanadium precipitation.

5. The method for recovering valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 1, wherein In Step S2.3, the refining process of the crude Sc(OH)3 is as follows: Acid-dissolve the crude Sc(OH)3, add oxalic acid to the filtrate after filtration for scandium precipitation, filter and wash with water to obtain scandium oxalate, and roast the scandium oxalate to obtain scandium oxide.

6. The method for recovering valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 5, characterized in that, The crude Sc(OH)3 is acid-dissolved with nitric acid, the filtrate is heated to 70 - 100 °C after filtration, and oxalic acid 1.2 - 1.4 times the theoretical amount of scandium oxide is added for scandium precipitation, and then washed with pure water according to a solid-liquid ratio of 1:(1.2 - 1.5) after filtration.

7. The method for recycling valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 1, characterized in that, Step S4 further includes pulping the vanadium-rich slag, adding sodium chlorate for pulping oxidation, leaching with an alkali solution, filtering to obtain an alkali leaching solution and a leaching residue; adding sodium sulfite to the alkali leaching solution, adjusting to acidity with sulfuric acid, and then performing extraction to obtain a fourth loaded organic phase; washing the fourth loaded organic phase loaded with vanadium with sulfuric acid, and after washing, performing back-extraction of the fourth loaded organic phase with sulfuric acid to obtain a back-vanadium solution, and electrolyzing the back-vanadium solution after removing oil with resin to obtain a vanadium electrolyte solution.

8. The method for recovering valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 7, characterized in that, Leach the leaching residue with a NaOH solution for 1 - 4 h, filter to obtain a secondary leaching solution, add NaOH to the secondary leaching solution for another leaching, and then mix it into the alkali leaching solution.

9. The method for recycling valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 7 or 8, characterized in that, Pulp the vanadium-rich slag with water at a solid-liquid ratio of 1:(1 - 2), add sodium chlorate at 1.2 - 1.4 times the theoretical amount of Fe and V for pulping oxidation for 0.5 - 1 h, leach with a NaOH solution at a solid-liquid ratio of 1:(2 - 4) for 1 - 4 h, and filter to obtain the alkali leaching solution; add sodium sulfite at 1.2 - 1.4 times the theoretical amount of V2O5 to the alkali leaching solution, adjust the pH to 1 - 1.5 with sulfuric acid, and then perform multi-stage countercurrent extraction with P204 or P204+TBP+kerosene at O / A = 3:1 - 1:1 to obtain a fourth loaded organic phase; wash the fourth loaded organic phase loaded with vanadium multiple times by cross-flow with sulfuric acid at pH 1.5 - 2.5 at O / A = 3:1 - 1:1, and after washing, perform multi-stage cross-flow back-extraction of the fourth loaded organic phase with a sulfuric acid solution at O / A = 12:1 - 9:1 to obtain the back-vanadium solution.

10. The method for recycling valuable metals from waste acid in sulfuric acid process titanium dioxide production by treating steel slag according to claim 1, characterized in that, In step S1, cool the waste acid from titanium dioxide production by the sulfuric acid method by 3 - 9 °C for 1 - 7 h, and stir at a speed of 30 - 60 rpm while cooling, and filter to obtain the ferrous sulfate heptahydrate crystals.

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