Method for recycling magnesium-containing wastewater of sulfuric acid roasted ore

Abstract

The invention relates to a method for recycling magnesium-containing wastewater of sulfuric acid roasted ore, which comprises the following steps: adding a calcium chloride solution into magnesium-containing extraction wastewater to carry out a first precipitation reaction to obtain a calcium sulfate byproduct and a magnesium chloride recovery solution; adding calcium oxide or calcium hydroxide into part of the magnesium chloride recovery liquid to carry out a second precipitation reaction, and reusing the obtained calcium chloride solution in the first precipitation reaction; the sulfuric acid rare earth roasted ore and the residual magnesium chloride recovery liquid are mixed, subjected to size mixing and leached, magnesium-containing alkaline matter is added into obtained rare earth leaching liquid for neutralization, and neutralized rare earth leaching liquid is obtained; adding a magnesium-containing alkaline substance into the organic extraction agent to obtain a saponification extraction agent; mixing the neutralized rare earth leachate with a saponification extraction agent, and extracting to obtain extraction wastewater; magnesium-containing extraction wastewater obtained after oil removal is returned to the first precipitation reaction; the extraction wastewater can be recycled to the sulfuric acid roasted ore water leaching process, waste residue discharge is reduced, water recycling is achieved, and the resource recovery rate of sulfate radicals, magnesium and calcium is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth smelting and separation technology and industrial environmental protection technology, and in particular relates to a method for recycling magnesium-containing waste water from sulfuric acid roasting ore. Background Art

[0002] Rare earth is a general term for 17 elements, including 15 lanthanide elements and yttrium and scandium in the third subgroup of the sixth period of the periodic table. At present, the separation and purification of rare earth elements mainly adopts extraction separation technology, and the extraction capacity of rare earth is inversely proportional to the cube of the equilibrium acidity of the water phase. In order to improve the production efficiency of rare earth separation, the extractant must first be saponified with ammonia water or liquid alkali, and then the saponified extractant and the rare earth solution are subjected to extraction reaction to generate a rare earth-containing loaded organic phase and extraction wastewater. The saponification extraction process will produce a large amount of high-salt wastewater such as ammonium chloride and sodium chloride. There is still no efficient treatment method for this type of high-salt wastewater. Most of them are treated by evaporation and crystallization processes with extremely high energy consumption, which requires enterprises to pay high governance costs and also causes serious pollution to the ecological environment. Therefore, it is necessary to develop a green and environmentally friendly saponification and rare earth extraction process. This leads to the recycling process of Ca and Mg leaching and saponification.

[0003] Roasting with concentrated sulfuric acid is mainly used to decompose Bayan Obo rare earth concentrate, and can also be used for the decomposition and recovery of fluorocarbon cerium ore, monazite, xenotime and some waste materials. After intensive roasting with concentrated sulfuric acid, it is leached with water. Most of the rare earths enter the water phase in the form of sulfates. At the same time, impurity ions such as calcium, magnesium, thorium, iron, and manganese also enter the water infusion in the form of sulfates. It is usually neutralized to a pH value of about 4.5 to remove thorium and iron. Because potassium, sodium, ammonium, etc. will form complex salt precipitation with rare earth sulfate, calcium and magnesium oxides or hydroxides are often used as neutralizers. Calcium neutralization will form calcium sulfate precipitation, which will increase the loss of organic phase and reduce the yield of rare earths in the subsequent contact process with organic extractants, so magnesium oxide is often used for neutralization and impurity removal. The filtrate obtained by filtration after neutralization is called qualified water infusion, and the filter residue is water infusion residue and stored as waste residue. The water infusion uses solvent extraction to separate rare earth elements. Magnesium oxide is usually used as a saponifying agent, and the rare earth ions in the water extract are exchanged with the magnesium ions in the saponified P507 to obtain an organic phase loaded with rare earths and an extraction wastewater mainly containing magnesium sulfate.

[0004] Currently, the most commonly used magnesium sulfate extraction wastewater treatment process is the lime neutralization method. This method adds lime to the wastewater to generate a large amount of magnesium hydroxide and calcium sulfate mixture as solid waste. The precipitated water can be recycled for roasting and leaching. This method achieves water reuse, but ignores the recovery of magnesium resources, and produces a large amount of high-impurity calcium sulfate slag that cannot be used.

[0005] In order to realize the recycling of calcium and magnesium wastewater, Chinese patents CN201811185096 and CN201811185133 disclose a comprehensive utilization method of magnesium and / or calcium waste liquid in the rare earth smelting and separation process. Magnesium and / or calcium waste liquid is pyrolyzed to obtain magnesium oxide and / or calcium oxide solid and hydrogen chloride gas. The obtained hydrogen chloride gas is used for acid dissolution of rare earth ores or rare earth extraction and separation, and the obtained magnesium oxide and / or calcium oxide are directly returned for rare earth precipitation. However, this method is recycled by thermal decomposition, which consumes a lot of energy and causes waste of water resources. In addition, hydrogen chloride gas is highly corrosive and has high requirements for equipment.

[0006] In order to improve the utilization rate of water, there is also a method of using CaO saponification extraction to produce CaCl2 extraction wastewater and CaCl2 liquid for water leaching of sulfuric acid roasted ore, such as the rare earth leaching and leaching water recycling method of sulfuric acid roasted rare earth concentrate disclosed in Chinese patent CN201410538625. This method can realize the recycling of wastewater, and there is no wastewater discharge in the process, but the CaCl2 liquid forms calcium sulfate precipitation in the water leaching process of sulfuric acid roasted ore and enters the waste residue, and the amount of calcium sulfate slag is large and not recovered. In the treatment method of sulfuric acid rare earth roasted ore disclosed in Chinese patent CN202011376494, rare earth chloride is used to leach sulfuric acid roasted ore, and calcium chloride is added to the leaching solution to precipitate calcium sulfate solid and rare earth chloride solution. Calcium sulfate can be recycled to reduce the amount of water leaching residue, but the calcium sulfate slag in this method is generated in the rare earth solution, and the precipitation will cause a large rare earth entrainment loss.

[0007] In order to improve the utilization rate of Mg resources and solve the circulation problem of roasting ore water leaching solution and extraction wastewater, methods of magnesium bicarbonate water leaching, saponification and precipitation have emerged, but these methods all require CO2 for carbonization circulation, and calcium sulfate recovery is more difficult, such as Chinese patent CN201210137935.

[0008] In order to realize the recycling of Mg, Chinese patent CN202310927695 discloses a process for treating rare earth magnesium sulfate soap wastewater and recycling magnesium resources, which uses ammonia water and CO2 to generate ammonium bicarbonate in a carbonization reactor, and then adds magnesium sulfate wastewater for double decomposition reaction. The basic magnesium carbonate produced is used as an extraction saponifier, and the ammonium sulfate solution is concentrated and crystallized by MVR. This method realizes the reuse of water and magnesium, but both carbonization and MVR concentration are complicated and energy-intensive.

[0009] In order to recycle the Mg resources in the solution, there is also a method for preparing magnesium hydroxide by precipitation using ammonia water. Chinese patents CN2008100103356, CN2008100103360, and CN2008100103341 disclose continuous preparation methods for preparing high-purity magnesium hydroxide using ammonia, liquid ammonia, and atomized ammonia water as precipitants; but more are methods for preparing magnesium hydroxide and calcium sulfate using the brine lime method, such as the process for producing high-purity magnesium hydroxide using the brine lime method disclosed in Chinese patent 2009100209745, in which lime solution is added to brine for precipitation to obtain magnesium hydroxide; such as the method for preparing high-purity magnesium hydroxide and co-producing nano-calcium carbonate using salt lake brine disclosed in Chinese patent 2011102466182, in which lime milk is added to brine for precipitation to obtain magnesium hydroxide.

[0010] The rare earth extraction wastewater recovery process draws on the operation of the brine lime method. Chinese patent CN201911075270 discloses that the magnesium chloride extraction wastewater is added with lime slurry to prepare calcium chloride solution and magnesium hydroxide filter cake, and calcium chloride is pyrolyzed and carbonized at high temperature to obtain calcium carbonate. This method can remove calcium chloride from high-salinity wastewater, but the recovery cost is high.

[0011] The use of brine lime method, calcium / magnesium saponification and water leaching liquid circulation is also one of the ways to achieve wastewater circulation and magnesium resource utilization. For example, Chinese patent CN201610225278 discloses a process for the treatment and recycling of rare earth industrial wastewater, which uses magnesium sulfate wastewater as raw material, adds a precipitant to remove sulfate, and uses quicklime, slaked lime or calcium chloride to recover magnesium to obtain magnesium hydroxide products and calcium chloride solutions. Magnesium hydroxide products can be used for extractant saponification, and calcium chloride solutions can be used for leaching of rare earth roasted ores. The biggest problem with this process is that calcium chloride solution is used to leach sulfuric acid roasted rare earth ores. The leaching process produces a large amount of calcium sulfate slag together with water leaching waste slag, which leads to a significant increase in the amount of waste slag, a decrease in the rare earth leaching rate, and the inability to recycle calcium sulfate. Another example is the Chinese patent CN201810545486, which discloses a method for leaching rare earth sulfate roasted ore with magnesium chloride solution in a cycle. The sulphuric acid roasted ore and magnesium chloride recovery solution are mixed for leaching. After the water leaching solution is extracted and transformed, rare earth chloride solution and magnesium sulfate wastewater are obtained; the magnesium sulfate wastewater is adjusted to pH value with alkali and mixed with calcium chloride recovery solution, and calcium sulfate dihydrate and magnesium chloride are formed after precipitation and filtration; the magnesium chloride solution is circulated to leach the roasted ore, the high-concentration magnesium chloride solution is concentrated and crystallized, and the magnesium chloride crystal byproduct is washed and recovered with distilled water; the distilled water and magnesium chloride recovery solution are continued to be used to leach rare earth roasted ore. This method recovers calcium sulfate and magnesium chloride, but magnesium chloride is obtained by concentrated crystallization, which consumes a lot of energy. The reason why magnesium chloride needs to be concentrated is that calcium chloride aqueous solution is added to the process, which increases the volume of the circulating liquid and requires concentration to reduce the amount of water. The source of calcium chloride in the scheme is calcium chloride saponification wastewater produced by rare earth extraction and separation, or calcium chloride wastewater produced by ammonium chloride lime emulsification. It can be seen that calcium chloride saponification wastewater is produced during the extraction and separation. The addition of this calcium chloride wastewater to the magnesium chloride circulation process causes the volume to increase continuously and must be concentrated. Summary of the invention

[0012] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for recycling magnesium-containing wastewater from sulfuric acid roasting ore, which recycles the magnesium sulfate wastewater obtained by saponification extraction of magnesium-containing alkaline substances into the water leaching process of the sulfuric acid roasting ore, reduces waste residue discharge, realizes the recycling of water, and improves the resource recovery rate of sulfate, magnesium and calcium.

[0013] To achieve the above purpose, the technical solution adopted by the present invention is: a method for recycling magnesium-containing wastewater from sulfuric acid roasting ore, the method comprising the following steps:

[0014] S1, adding calcium chloride solution to magnesium-containing extraction wastewater to carry out a first precipitation reaction, and separating the solid and liquid to obtain a calcium sulfate byproduct and a magnesium chloride recovery liquid;

[0015] S2, taking part of the magnesium chloride recovery liquid, adding powder or slurry containing calcium oxide or calcium hydroxide to carry out a second precipitation reaction, and separating the solid and liquid to obtain a magnesium-containing alkaline substance precipitate and a calcium chloride solution, and the calcium chloride solution is reused in step S1;

[0016] S3, taking concentrated sulfuric acid and rare earth ore roasted ore formed by roasting, mixing with the remaining magnesium chloride recovery liquid to prepare slurry for leaching, and after the leaching is completed, filtering and washing to obtain water leaching residue and rare earth leaching liquid;

[0017] S4, adding magnesium-containing alkaline substances to the rare earth leachate for neutralization, filtering to remove impurities, and obtaining a neutralized rare earth leachate;

[0018] S5, adding the magnesium-containing alkaline substance to the organic extractant for saponification to obtain a saponified extractant;

[0019] S6, mixing the neutralized rare earth leaching solution with the saponification extractant, performing extraction and separation to obtain extraction wastewater;

[0020] S7, removing the oily organic matter carried by the extraction wastewater, and returning the magnesium-containing extraction wastewater after oil removal to step S1.

[0021] Further, in step S1, the CaO in the magnesium chloride recovery solution is less than 10 g / L, SO4 2- <10g / L.

[0022] Furthermore, the magnesium oxide content in the calcium sulfate byproduct is less than 1%, and the whiteness is greater than 50.

[0023] Furthermore, in step S2, the endpoint pH value of the second precipitation reaction is controlled to be 9-12.

[0024] Further, in step S2, the magnesium-containing alkaline substance precipitate passes through a thickener or a cyclone separator to separate calcium impurities therein to obtain a magnesium-containing alkaline substance solid.

[0025] Further, in step S3, the rare earth ore is one or more of monazite, xenotime and bastnaesite.

[0026] Furthermore, the content of REO in the rare earth leaching solution in step S3 is 20-55 g / L.

[0027] Furthermore, in step S4, when the rare earth leachate is neutralized by adding the magnesium-containing alkaline substance, the pH value of the rare earth leachate is adjusted to 3-5, and the impurities are removed by filtration to obtain the neutralized rare earth leachate.

[0028] Further, in step S4, the magnesium-containing alkaline substance is one or more of magnesium oxide and magnesium hydroxide.

[0029] Furthermore, the magnesium-containing alkaline substance is a magnesium-containing alkaline substance solid obtained by recovering the magnesium-containing alkaline substance through precipitation in step S2.

[0030] Further, in step S5, the organic extractant is at least one of P507, P204, and C272.

[0031] Further, in step S7, the extraction wastewater is passed through a grease trap and / or inclined plate sedimentation and / or flotation and / or a coalescence separation device to remove oil organic matter carried over during extraction and separation, thereby obtaining magnesium-containing extraction wastewater.

[0032] The beneficial effects of the present invention are as follows: a method for recycling magnesium-containing wastewater of sulfuric acid roasted ore provided by the present invention comprises the following steps: adding a calcium chloride solution to magnesium-containing extraction wastewater for a first precipitation reaction, and performing solid-liquid separation to obtain a calcium sulfate byproduct and a magnesium chloride recovery liquid; taking part of the magnesium chloride recovery liquid, adding a powder or slurry containing calcium oxide or calcium hydroxide for a second precipitation reaction, and performing solid-liquid separation to obtain a magnesium-containing alkaline substance precipitate and a calcium chloride solution, and the calcium chloride solution is reused in the first precipitation reaction; taking a rare earth roasted ore formed by roasting concentrated sulfuric acid and rare earth ore, and mixing the rare earth roasted ore with the remaining magnesium chloride recovery liquid for slurry preparation and leaching, and after the leaching is completed, Filter and wash to obtain water leaching residue and rare earth leaching solution; add magnesium-containing alkaline substances to the rare earth leaching solution for neutralization, filter to remove impurities, and obtain neutralized rare earth leaching solution; add magnesium-containing alkaline substances to the organic extractant for saponification to obtain a saponified extractant; mix the neutralized rare earth leaching solution with the saponified extractant, perform extraction and separation, and obtain extraction wastewater; remove oil organic matter entrained in the extraction wastewater, and return the magnesium-containing extraction wastewater after oil removal to the first precipitation reaction; realize the recycling of extraction wastewater to the sulfuric acid roasting ore water leaching process, reduce waste residue discharge, and realize the recycling of water, and improve the resource recovery rate of sulfate, magnesium, and calcium. The beneficial effects of the present invention are specifically embodied in:

[0033] (1) Recycling the magnesium-containing wastewater from the sulfuric acid roasting ore to the water leaching process of the sulfuric acid roasting ore, realizing the recycling of water and not discharging high-salt wastewater;

[0034] (2) Using a circulating calcium chloride solution to recover sulfate in wastewater, calcium sulfate is separated from water leaching residue and neutralization residue, and the residue is recovered as a by-product separately, which improves the utilization rate of sulfate and reduces the discharge of waste residue;

[0035] (3) Using lime to recover magnesium resources in wastewater, high-quality magnesium-containing alkaline substances are prepared at low cost. The impurity calcium content is low, and the magnesium-containing alkaline substances can be used for neutralization of water leaching liquid or as extraction saponifiers, and react with organic extractants to obtain saponification extractants, which reduces the cost of magnesium saponifiers and improves the resource recovery rate of Mg;

[0036] (4) Using magnesium chloride solution to leach sulfuric acid roasted ore increases the rare earth concentration of the water solution;

[0037] (5) The entire process does not involve complex, high-energy-consuming equipment such as evaporation concentration, thermal decomposition, MVR, and carbonization towers. The production process is simple, the equipment value is low, and the production process cost is reduced while the energy consumption is also low. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic flow chart of a method for recycling magnesium-containing wastewater from sulfuric acid roasting ore according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be further clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] The present embodiment provides a method for recycling magnesium-containing wastewater from sulfuric acid roasting ore, which uses magnesium sulfate wastewater obtained by saponification extraction of magnesium hydroxide as a raw material, adds a cyclically prepared CaCl2 solution to obtain calcium sulfate solid recovery, and converts the solution into magnesium chloride; a part of the obtained magnesium chloride solution is used as a water soak of the sulfuric acid roasting ore to obtain rare earth sulfate as an extraction raw material; another part of the magnesium chloride solution is added with lime precipitation to obtain a calcium chloride solution and a magnesium-containing alkaline substance precipitate; calcium chloride is circulated to prepare calcium sulfate, and the magnesium-containing alkaline substance solid obtained after the magnesium-containing alkaline substance precipitate is removed and impurities are removed is used as an extraction saponifier.

[0041] The method provided in this embodiment recycles the extraction wastewater to the sulfuric acid roasting ore leaching process, realizes the recycling of water, and does not discharge the extraction high-salt wastewater; wherein, the sulfate ions in the wastewater are recovered by circulating calcium chloride solution, and the calcium sulfate by-product is recovered, thereby improving the utilization rate of the sulfate ions and reducing the discharge of waste residues; the magnesium resources in the wastewater are recovered by lime, and magnesium hydroxide is prepared at low cost for use as an extraction saponifier.

[0042] like Figure 1 As shown, an embodiment of the present invention provides a method for recycling magnesium-containing wastewater from sulfuric acid roasting ore, the method comprising the following steps:

[0043] S1, adding calcium chloride solution to magnesium-containing extraction wastewater to carry out a first precipitation reaction, and separating the solid and liquid to obtain a calcium sulfate byproduct and a magnesium chloride recovery liquid;

[0044] Among them, the ratio of the amount of calcium chloride solution added to the magnesium sulfate in the magnesium-containing extraction wastewater meets the following conditions: Ca 2+ With SO42- The molar ratio is 0.9-1.1:1.0.

[0045] Specifically, in step S1, the CaO in the magnesium chloride recovery solution is less than 10 g / L, SO4 2- <10g / L.

[0046] Specifically, since the magnesium-containing extraction wastewater contains residual oil phase, the directly prepared calcium sulfate is yellowish with a whiteness of 30-40, and the calcium sulfate byproduct obtained by precipitation after oil removal has increased whiteness. The magnesium oxide content in the calcium sulfate byproduct is less than 1%, and the whiteness is >50.

[0047] S2, taking part of the magnesium chloride recovery liquid, adding powder or slurry containing calcium oxide or calcium hydroxide to carry out a second precipitation reaction, and separating the solid and liquid to obtain a magnesium-containing alkaline substance precipitate and a calcium chloride solution, and the calcium chloride solution is reused in step S1;

[0048] The added amount of calcium oxide or calcium hydroxide powder or slurry and the ratio of magnesium chloride in the partial magnesium chloride recovery liquid meet the following conditions: the molar ratio of Ca to Mg is 0.9-1.1:1.0.

[0049] Optionally, the portion of magnesium chloride recovery liquid in step S2 is 20-80% of the magnesium chloride recovery liquid.

[0050] Specifically, in step S2, the endpoint pH value of the second precipitation reaction is controlled to be 9-12.

[0051] Optionally, in step S2, the magnesium-containing alkaline substance precipitate is passed through a thickener or a cyclone separator to separate a small amount of calcium impurities therein to obtain a magnesium-containing alkaline substance solid.

[0052] S3, taking concentrated sulfuric acid and rare earth ore roasted ore formed by roasting, mixing with the remaining magnesium chloride recovery liquid to prepare slurry for leaching, and after the leaching is completed, filtering and washing to obtain water leaching residue and rare earth leaching liquid;

[0053] Optionally, in step S3, the rare earth mineral is one or more of monazite, xenotime and bastnaesite.

[0054] In a specific embodiment, the volume ratio of the residual magnesium chloride recovery liquid to the rare earth roasted ore is 10:1.

[0055] Optionally, the content of REO (rare earth oxide) in the rare earth leaching solution in step S3 is 20-55 g / L.

[0056] S4, adding magnesium-containing alkaline substances to the rare earth leachate for neutralization, filtering to remove impurities, and obtaining a neutralized rare earth leachate;

[0057] Optionally, when the rare earth leachate is neutralized by adding the magnesium-containing alkaline substance in step S4, the pH value of the rare earth leachate is adjusted back to 3-5, and the impurities are removed by filtration to obtain the neutralized rare earth leachate.

[0058] Optionally, in step S4, the magnesium-containing alkaline substance is one or more of magnesium oxide, magnesium hydroxide, basic magnesium chloride, and basic magnesium sulfate. The magnesium hydroxide is preferably the magnesium-containing alkaline substance solid recovered by precipitation of the magnesium-containing alkaline substance in step S2. When the recovered magnesium-containing alkaline substance solid is insufficient, commercially available magnesium oxide or magnesium hydroxide is used to supplement it.

[0059] S5, adding the magnesium-containing alkaline substance to the organic extractant for saponification to obtain a saponified extractant;

[0060] Optionally, in step S5, the organic extractant is at least one of P507, P204, and C272. Among them, P507 is a commercially available extractant 2-ethylhexyl phosphate, P204 is a commercially available extractant di(2-ethylhexyl) phosphate, and C272 is a commercially available extractant bis(2,4,4-trimethylpentyl)phosphonic acid.

[0061] In a specific embodiment, the magnesium-containing alkaline substance is added to the organic extractant to carry out a saponification reaction until the saponification value reaches 0.54, thereby obtaining a saponified extractant.

[0062] S6, mixing the neutralized rare earth leaching solution with the saponification extractant, performing extraction and separation to obtain extraction wastewater and an organic phase loaded with rare earth;

[0063] In a specific embodiment, the saponification value of the saponification extractant is 0.54, the charge number of the rare earth ion is 3, and the molar ratio of the rare earth molar amount of the rare earth leaching solution to the saponification value of the saponification extractant is 1:3 to achieve charge balance.

[0064] S7, removing the oily organic matter carried by the extraction wastewater, and returning the magnesium-containing extraction wastewater obtained after oil removal to step S1.

[0065] Optionally, in step S7, the extraction wastewater is passed through a grease trap and / or inclined plate sedimentation and / or flotation and / or coagulation separation equipment to remove oil organic matter entrained during extraction and separation to obtain magnesium-containing extraction wastewater.

[0066] By adopting a method for recycling magnesium-containing wastewater of a sulfuric acid roasting ore provided in this embodiment, the extraction wastewater can be recycled to the water leaching process of the sulfuric acid roasting ore, realizing the recycling of water, and not discharging the extraction high-salt wastewater. This embodiment adopts a circulating calcium chloride solution to recover sulfate in the wastewater, and recovers it as a calcium sulfate byproduct, which improves the utilization rate of sulfate while also reducing the discharge of waste residue. Moreover, this embodiment uses lime to recover magnesium resources in the wastewater, and prepares high-quality magnesium-containing alkaline substances at low cost for use as extraction saponifiers, which react with organic extractants to obtain saponification extractants, reducing the cost of magnesium saponifiers. It can be seen that the method provided in this embodiment recycles the extraction wastewater to the water leaching process of the sulfuric acid roasting ore, reduces waste residue discharge, and realizes the recycling of water at the same time, improving the resource recovery rate of sulfate, magnesium, and calcium.

[0067] The specific implementation modes of the present invention are further described below through examples.

[0068] Example 1: Treatment of magnesium-containing extraction wastewater by recycling magnesium-containing wastewater from sulfuric acid roasted ore and preparing a saponification extractant

[0069] (1) 1L magnesium-containing extraction wastewater, with MgO content of 45g / L, SO4 2- The content is 52g / L; 0.9L 0.6mol / L CaCl2 solution is added at room temperature at 30℃ for the first precipitation reaction, and the generated calcium sulfate precipitate is filtered and washed to obtain a calcium sulfate byproduct, in which the MgO content is 0.5% and the whiteness is 75; the magnesium chloride recovery liquid obtained has a Mg content of 0.58mol / L, a CaO content of 2g / L, and SO4 2- The content is 3.6g / L.

[0070] (2) taking 50% of the magnesium chloride recovery liquid and adding lime powder solid to a pH value of 11.5 for a second precipitation reaction, the obtained CaCl2 solution has a Ca content of 0.56 mol / L and a Mg content of 0.5 g / L, which is reused in step (1); the obtained magnesium hydroxide precipitate is filtered and washed to obtain magnesium hydroxide solid.

[0071] (3) The remaining 50% of the magnesium chloride recovery liquid is used to leach the sulfuric acid roasted ore to obtain a rare earth water extract containing 35 g / L of rare earth; solid magnesium hydroxide is added to obtain a neutralized rare earth water extract.

[0072] (4) Add solid magnesium hydroxide to the organic extractant P507, and mix and react until the saponification value reaches 0.54 to obtain a saponified extractant.

[0073] (5) Mixing the saponified extractant with the neutralized rare earth water extract to obtain extraction wastewater and an organic phase loaded with rare earths; removing the oily organic matter entrained in the extraction wastewater through a grease trap, and repeating the cyclic process of steps (1) to (5) for the obtained magnesium-containing extraction wastewater.

[0074] The method described in the present invention is not limited to the specific embodiments described. The above embodiments are only examples of the present invention. The present invention can also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described embodiments should be regarded as illustrative rather than restrictive in any respect. The scope of the present invention should be described by the attached claims, and any changes equivalent to the intent and scope of the claims should also be included in the scope of the present invention.

Claims

1. A method for recycling magnesium-containing wastewater from sulfuric acid roasting ore, characterized in that: The method comprises the following steps: S1, adding calcium chloride solution to magnesium-containing extraction wastewater to carry out a first precipitation reaction, and separating the solid and liquid to obtain a calcium sulfate byproduct and a magnesium chloride recovery liquid; S2, taking part of the magnesium chloride recovery liquid, adding powder or slurry containing calcium oxide or calcium hydroxide to carry out a second precipitation reaction, and separating the solid and liquid to obtain a magnesium-containing alkaline substance precipitate and a calcium chloride solution, and the calcium chloride solution is reused in step S1; S3, taking concentrated sulfuric acid and rare earth ore roasted ore formed by roasting, mixing with the remaining magnesium chloride recovery liquid to prepare slurry for leaching, and after the leaching is completed, filtering and washing to obtain water leaching residue and rare earth leaching liquid; S4, adding magnesium-containing alkaline substances to the rare earth leachate for neutralization, filtering to remove impurities, and obtaining a neutralized rare earth leachate; S5, adding the magnesium-containing alkaline substance to the organic extractant for saponification to obtain a saponified extractant; S6, mixing the neutralized rare earth leaching solution with the saponification extractant, performing extraction and separation to obtain extraction wastewater; S7, removing the oily organic matter carried by the extraction wastewater, and returning the magnesium-containing extraction wastewater after oil removal to step S1.

2. A method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: The CaO in the magnesium chloride recovery solution in step S1 is less than 10 g / L, SO4 2- <10g / L.

3. A method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: The magnesium oxide content in the calcium sulfate byproduct is less than 1%, and the whiteness is greater than 50.

4. The method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: In step S2, the endpoint pH value of the second precipitation reaction is controlled to be 9-12.

5. The method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: In step S2, the magnesium-containing alkaline substance precipitate passes through a thickener or a cyclone separator to separate calcium impurities therein to obtain a magnesium-containing alkaline substance solid.

6. The method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: In step S3, the rare earth ore is one or more of monazite, xenotime and bastnaesite.

7. The method for recycling magnesium-containing wastewater from sulfuric acid roasting of ore according to claim 1, characterized in that: The content of REO in the rare earth leaching solution in step S3 is 20-55 g / L.

8. The method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: In step S4, when the rare earth leachate is neutralized by adding the magnesium-containing alkaline substance, the pH value of the rare earth leachate is adjusted to 3-5, and the impurities are removed by filtration to obtain the neutralized rare earth leachate.

9. The method for recycling magnesium-containing wastewater from a sulfuric acid roasted ore according to claim 1, characterized in that: In step S4, the magnesium-containing alkaline substance is one or more of magnesium oxide, magnesium hydroxide, basic magnesium chloride, and basic magnesium sulfate.

10. The method for recycling magnesium-containing wastewater from sulfuric acid roasting of ore according to claim 9, characterized in that: The magnesium-containing alkaline substance is the magnesium-containing alkaline substance solid obtained by recovering the magnesium-containing alkaline substance precipitation in step S2.

11. A method for recycling magnesium-containing wastewater from sulfuric acid roasting of ore according to any one of claims 1 to 10, characterized in that: In step S5, the organic extractant is at least one of P507, P204, and C272.

12. The method for recycling magnesium-containing wastewater from sulfuric acid roasting of ore according to claim 11, characterized in that: In step S7, the extraction wastewater is passed through a grease trap and / or inclined plate sedimentation and / or flotation and / or a coalescence separation device to remove oily organic matter carried over during extraction and separation, thereby obtaining magnesium-containing extraction wastewater.

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