CN103343234B - Method for preparing neodymium and iron oxides by using neodymium iron boron oil sludge through regeneration and co-precipitation - Google Patents

Abstract

The invention relates to a method for preparing neodymium and iron oxides by using neodymium iron boron oil sludge through regeneration and co-precipitation, belonging to the field of recycling of neodymium iron boron oil sludge. The method comprises the following steps of: adding hydrogen peroxide to oxidize a pickling liquid of the neodymium iron boron oil sludge, adjusting the PH value, adding a proper amount of sodium hydroxide, ammonium hydroxide or sodium oxalate precipitating agent at one step, preserving the heat of 60-100 DEG C for a period of time, centrifuging a sediment, drying, and roasting at high temperature to obtain a mixture of the neodymium and iron oxides. The method is short in operation process, simple in operation and capable of avoiding using a great deal of reagents.

Description

A method for preparing neodymium-iron oxides by regeneration co-precipitation of neodymium-iron-boron oil sludge

technical field

The invention relates to a method for preparing regenerated NdFeB sludge by one-step co-precipitation of NdFe alloy and NdFe oxide, which belongs to the recycling and utilization of NdFeB sludge.

Background technique

Today, one out of every six new technologies is related to rare earths, which fully demonstrates the role and status of rare earths in new technologies. Rare earth is an important strategic resource in the 21st century and the "monosodium glutamate" of modern industry. The reason why rare earth elements are called "strategic elements in the 21st century" is because they have special physical and chemical properties that other elements do not have. Many new rare earth materials made based on these characteristics have excellent performance and are widely used, and are widely used in electronic information, communication technology, automobile manufacturing, energy, aerospace and other fields. Rare earths have been hailed as "material vitamins" and "treasure house of high-tech and functional materials in the 21st century".

As rare earth elements are scarce and expensive important strategic resources, comprehensive recovery of valuable elements in waste is a very valuable work; reasonable recovery of rare earth elements can not only save and protect natural resources, reduce costs and improve economic benefits, but also benefit all domestic industries. The long-term and stable development of the field is also conducive to the recycling of rare earth elements and the sustainable development of the country.

As for NdFeB, which is rich in rare earth element NdFeB, it is naturally very important for the recovery and regeneration of NdFeB. The magnetic energy product of iron-boron magnets is 240-440kJ/m ³ , known as the contemporary "king of permanent magnets", and it is the permanent magnet material with the highest comprehensive performance known so far. Compared with traditional magnets, the magnetic energy product of rare earth permanent magnet materials is 4 to 10 times higher, and other magnetic properties are also much higher than traditional magnets; while the magnetic energy product of NdFeB permanent magnet materials is even higher than that of traditional magnetic materials. 8 to 10 times.

There are many processes for recycling NdFeB waste, such as acid-soluble precipitation process, double-salt conversion process, hydrochloric acid excellent dissolution process, etc. Some traditional recycling methods are listed below:

Based on the above current rare earth recovery methods, although these processes can regain rare earths, there are still many problems: first of all, from the results, the circular chain of the above processes does not form a real cycle, and the products obtained by these processes are only Rare earth oxides are not made into industrial products that can be used directly. Moreover, if rare earth oxides are to be purified into high-purity single rare earths that can be directly used in industry, dozens of stages of extraction processes are required, and the extraction agents are very expensive, and the social benefits are significantly reduced. Secondly, from the perspective of economic benefits, in addition to the above-mentioned extraction process that consumes a large amount of acid solution, time and expensive extraction agents when purifying high-purity single rare earths, the ordinary acid-soluble precipitation method needs to carry out secondary extraction of rare earths when recovering rare earths. Secondary precipitation, which not only has a long process, high investment, but also low recovery rate, and the economic benefit is obviously very low; while in the process of extracting rare earths by the full extraction method, although the process has a high purity of rare earths when recovering rare earths, and Higher purity cobalt can be obtained, but its complex chemical process and high cost make this method unacceptable for industrial production from the beginning. Thirdly, from the perspective of energy conservation and environmental protection, whether it is the hydrochloric acid optimal solution method, the total extraction method or the sulfuric acid double salt precipitation method, they will form a large amount of acid-base waste liquid and toxic and harmful gases in the recovery of rare earths. Only in the extraction process, because of the need for higher liquid-to-liquid ratio and better stripping effect, the acid consumption is more than 10 times the normal stoichiometric amount, and the acid-base waste liquid formed in these processes is very high at the end of the process. Difficult to deal with; not only that, the sulfuric acid double salt precipitation method will produce SO ₂ and H ₂ S gases that are very harmful to the human body during the iron recovery process.

Contents of the invention

The present invention aims at the above-mentioned problems, and adopts a one-step Nd-Fe co-precipitation method instead of only selectively precipitating Nd to recover the valuable elements in the acid-dissolved solution. This method recovers NdFeB at the same time, the process is short, and the valuable elements are not wasted, and it can be used to synthesize NdFeB magnetic powder to realize real recycling, so this method has good economical practicability.

A method for preparing neodymium-iron oxides by regenerating co-precipitation of NdFeB oil sludge, characterized in that it comprises the following steps: adding hydrogen peroxide to the acid immersion solution of NdFeB oil sludge for oxidation, adjusting the pH value, and adding an appropriate amount of sodium hydroxide once , ammonia water or sodium oxalate precipitant, after a period of time of heat preservation at a temperature of 60-100°C, the precipitate is centrifuged and dried, and roasted at a high temperature to obtain a mixture of neodymium-iron oxides.

The technical scheme formulated by the present invention further preferably comprises the following steps:

(1) When sodium hydroxide is used as the precipitant for one-step co-precipitation, the best conditions for co-precipitation are: after acid-dissolving and filtering the NdFeB sludge, add excess mass concentration of 30% hydrogen peroxide to the filtrate for oxidation and keep stirring; In order to prevent the formation of ferric hydroxide colloid, choose to adjust the PH value first and then keep warm. Therefore, first adjust the PH value to 4~9 (preferably PH=7~9), then control the reaction temperature to 60~100℃, and add 1mol/L The sodium hydroxide solution was reacted under stirring conditions for 60mins. Finally, the precipitate was centrifugally dried and placed in a box furnace, and roasted at T=400-600°C for 90mins; the preferred dosage of sodium hydroxide solution was Boron sludge corresponds to 30ml of sodium hydroxide solution.

(2) When ammonia water is used as the precipitant for one-step co-precipitation, the best conditions for co-precipitation are: after acid-dissolving and filtering the NdFeB sludge, the filtrate is oxidized with excess mass concentration of 30% hydrogen peroxide and kept stirring, adding 30% Ammonia water until the pH of the precipitated solution is adjusted to 8~10 (preferably PH=5.5~7.5), then the reaction temperature is controlled at 60~100°C, and the reaction is left to stand for 60mins. Finally, the precipitate is centrifuged and dried and placed in a box furnace , baked at T=400～600℃ for 90mins.

(3) When sodium oxalate is used as the precipitant for one-step co-precipitation, the best condition for co-precipitation is: after the NdFeB oil sludge is acid-dissolved and filtered, the filtrate is oxidized with excess mass concentration of 30% hydrogen peroxide and kept stirring, for To prevent the formation of ferric hydroxide colloid, choose to adjust the pH value first and then keep warm. Therefore, first adjust the pH to 1-3, then control the reaction temperature to 60-100°C, and add hot 0.1mol/L sodium oxalate solution at a temperature of 35-50°C and allow it to react for 60mins under stirring. Finally, after centrifuging and drying the precipitate, put it in a box furnace, and bake it at T=600-800°C for 90mins. Preferably, every 5g of NdFeB sludge corresponds to 300ml of sodium oxalate solution.

The solid-to-liquid ratio during the acid-dissolving process of the above-mentioned NdFeB sludge is (1g): (10-15ml).

The mass content of iron and neodymium in the product obtained in the present invention is respectively: 47.89% to 63.44%, and 18.10% to 34.51%, which are basically consistent with the mass ratio of iron and neodymium in raw materials.

The beneficial effects of the present invention are:

(1) NdFe can be co-precipitated in one step, the operation process is short, the operation is simple, and the use of large-scale reagents is avoided;

(2) The effects of sodium hydroxide, ammonia water and sodium oxalate on the co-precipitation of iron and neodymium in one-step method were discussed, among which the co-precipitation effect of sodium oxalate was better, the impurity content was low, and the powder particles were uniform;

(3) Provide favorable conditions for the subsequent preparation of NdFeB regenerated magnetic powder, realize the industrial cycle chain, and lay a good foundation for "urban mines".

Description of drawings

Fig. 1 is the XRD spectrum of the neodymium-iron oxide that obtains under different pH values when using NaOH as precipitating agent in embodiment 1;

Fig. 2 is the XRD spectrum of the neodymium-iron oxide obtained at different pH values when using ammonia as a precipitating agent in embodiment 2;

Fig. 3 is the XRD spectrum of the neodymium-iron oxide obtained in Example 3 using sodium oxalate as a precipitating agent.

Detailed ways

The present invention will be further described below in conjunction with examples, but the present invention is not limited to following examples. The following hydrogen peroxide is hydrogen peroxide with a mass concentration of 30%.

Example 1:

First, take 5g of NdFeB oil sludge, add 60ml of 4mol/L hydrochloric acid to the waste, and after fully dissolving, add excess hydrogen peroxide to the filtrate and stir for 10min. Then, adjust the pH values to 4, 7, and 9 by adding ammonia water at a volume ratio of 1:1, and place the filtrate in a collector heating stirrer, control the reaction temperature at 70°C, and slowly add 1 mol/L of hydrogen Sodium oxide 30ml and let it react in the mixer for 60mins. Finally, after centrifuging and drying the precipitate, put it in a box furnace, and bake it at T=400°C for 90mins to obtain the mixed oxide of neodymium iron. Through XRD, XRF and other testing methods, we obtained the following results:

Compare the phase and element content of the Nd-Fe mixed oxide obtained by adding sodium hydroxide and roasting at the pH value of 4, 7, and 9, and analyze and discuss:

Table 1-1 XRF results of oxides obtained by roasting at different pH values when NaOH was used as the precipitant (%)

Through the comparison of the above results, it is considered that pH 7-9 is an ideal range of pH value selection for the one-step precipitation method, and its impurity content and types are low, and the recovery rate is also high through the conversion of recovery volume.

Example 2

First, take 5g of NdFeB oil sludge, add 60ml of 4mol/L hydrochloric acid to the waste, and after fully dissolving, add excess hydrogen peroxide to the filtrate and stir for 10min. Then, the filtrate was placed in a collector heating agitator, the reaction temperature was controlled at 70°C, 30% ammonia water was slowly added to adjust the pH value to 5.5, 7.5, and it was allowed to react in the agitator for 60mins. Finally, after centrifuging and drying the precipitate, put it in a box furnace, and bake it at T=400°C for 90mins to obtain the mixed oxide of neodymium iron. Through XRD, XRF and other testing methods, the following results were obtained:

Compare the phase and element content of the product obtained by adding ammonia water for precipitation and roasting when the pH value is 5.5 and 7.5, and analyze and discuss:

Table 1-2 XRF results of products roasted at different pH values with ammonia water as the precipitant (%)

It can be seen from Figure 2 that when ammonia water is used as the precipitating agent, there is only a ferric oxide phase but no neodymium oxide phase in the XRD spectrum; and the peak intensity of ferric oxide is very low. However, the XRF results (Table 1-2) show that neodymium element is precipitated in the precipitate, and the proportion in the precipitate is not low, reaching 20.13% and 18.10% at pH=5.5 and pH=7.5 respectively . The content of impurity elements such as Al, Si, Zn, Ca and P is also very low. The method of precipitating iron ions and neodymium ions in one step with ammonia water can obtain better elemental composition.

Example 3

First, take 5g of NdFeB oil sludge, add 60ml of 4mol/L hydrochloric acid to the waste, and after fully dissolving, add excess hydrogen peroxide to the filtrate and stir for 10min. Then, the pH value was adjusted to be 2 by adding 1:1 ammonia water, and the filtrate was placed in a collector heating stirrer, and the reaction temperature was controlled to be 70°C, and 300ml of hot 0.1mol/L sodium oxalate solution was slowly added and allowed to It was reacted in the mixer for 60mins. Finally, after centrifuging and drying the precipitate, put it in a box furnace, and bake it at T=800°C for 90mins to obtain the mixed oxide of neodymium and iron. Through XRD, XRF and other testing methods, we obtained the following results:

Table 1-3 XRF results of Nd-Fe mixed oxides calcined with sodium oxalate as precipitant (%)

It can be seen from Figure 3 that the phase spectrum line of the precipitate obtained by burning at 800°C has the smallest peak width at half maximum, the highest intensity, and the least influence of the impurity background, so we can see that the crystallinity of the precipitate at this time is the best . The XRF results in Table 1-3 show that the yield of rare earth elements is also high, with neodymium reaching 34.51% and praseodymium reaching 10.87%.

By one-step precipitation by adding sodium oxalate, a precipitate with uniform particles and good crystallinity can be obtained. And the impurity content is less; sodium ions and chloride ions can be removed by cleaning during the experiment. Using sodium oxalate as co-precipitant can better precipitate Nd ³⁺ and Fe ³⁺ at one time, and the ratio is closer to the material ratio of NdFeB; it can provide convenient conditions for subsequent ball milling.

Claims (3)

1. A method for preparing neodymium-iron oxides by regeneration co-precipitation of Nd-Fe-B oil sludge is characterized in that it comprises the following steps: after adding hydrogen peroxide to the acid immersion solution of Nd-Fe-B oil sludge for oxidation, adjusting the pH value, adding sodium hydroxide once 1. Ammonia water or sodium oxalate precipitating agent. After keeping warm for a period of time at a temperature of 60-100 ° C, the precipitate is centrifuged and dried, and roasted at a high temperature to obtain neodymium iron oxide; When sodium hydroxide is used as the precipitant for one-step co-precipitation, the co-precipitation conditions are as follows: after the NdFeB sludge is acid-dissolved and filtered, the filtrate is oxidized with excess mass concentration of 30% hydrogen peroxide and kept stirring; first adjust the pH value and then For heat preservation, first adjust the pH=4~9, then control the reaction temperature at 60~100°C, and add 1mol/L sodium hydroxide solution to react for 60mins under stirring conditions, and finally, centrifuge and dry the precipitate and place it in a box In the furnace, bake at T=400～600℃ for 90mins; When ammonia water is used as the precipitant for one-step co-precipitation, the co-precipitation conditions are as follows: after the NdFeB sludge is acid-dissolved and filtered, the filtrate is oxidized with excess mass concentration of 30% hydrogen peroxide and kept stirring, and 30% ammonia water is added until the precipitation is adjusted. Solution pH=5.5-7.5, then control the reaction temperature at 60-100°C, let stand for 60mins, finally, centrifuge and dry the precipitate, put it in a box furnace, and bake it at T=400-600°C for 90mins; When sodium oxalate is used as the precipitant for one-step co-precipitation, the co-precipitation conditions are as follows: after the NdFeB oil sludge is acid-dissolved and filtered, the filtrate is oxidized with excess mass concentration of 30% hydrogen peroxide and kept stirring, in order to prevent ferric hydroxide colloid Formation, choose to adjust the pH value first and then keep warm, therefore, first adjust the pH=1~3, then control the reaction temperature to 60~100°C, and add hot 0.1mol/L sodium oxalate solution with a temperature of 35-50°C and Allow it to react under stirring for 60 mins; finally, place the precipitate in a box furnace after being centrifuged and dried for 90 mins at T=600-800°C. 2. according to the method for claim 1, it is characterized in that, adjust pH=7～9 when using sodium hydroxide as the precipitation agent of one-step co-precipitation. 3. according to the method for claim 1, it is characterized in that, the solid-to-liquid ratio is (1g): (10-15ml) in the process of NdFeB sludge acid dissolution.