CN103667716B - A kind of at C2H2O4-NH3The method simultaneously reclaiming neodymium, praseodymium, dysprosium, cobalt, ferrum under system from neodymium iron boron greasy filth - Google Patents

Abstract

_The invention discloses a method for simultaneously recovering neodymium, praseodymium, dysprosium, cobalt and iron from NdFeB oil sludge under the _{C2H2O4 - NH3} system, belonging to the technical field of NdFeB oil sludge recovery. Thermodynamic research and simulation of C ₂ H ₂ O ₄ -NH ₃ system, establishment of thermodynamic model, determination of applicable process and process parameters. And under the C ₂ H ₂ O ₄ -NH ₃ system, adjust and select the pH twice: (0.5-2.5)-9 for "combination-precipitation", which can achieve the effect of simultaneous recovery of neodymium, praseodymium, dysprosium, cobalt, and iron . This process can effectively shorten the early process exploration, simple operation, simple process, effectively reduce waste discharge, and realize the full recovery of neodymium, praseodymium, dysprosium, cobalt, and iron in NdFeB sludge. Among them, the recovery rate of neodymium>=99%; the recovery rate of praseodymium>=99%; the recovery rate of cobalt>=79%; the recovery rate of dysprosium>=99%; the recovery rate of iron>=99%.

Description

A method for simultaneously recovering neodymium, praseodymium, dysprosium, cobalt, and iron from NdFeB sludge under C2H2O4-NH3 system

technical field

_The invention relates to a method for extracting neodymium, praseodymium, dysprosium, cobalt and iron from NdFeB oil sludge under a _{C2H2O4 - NH3} system, belonging to the technical field of NdFeB oil sludge recovery.

Background technique

Since Japanese and American scientists discovered the (third-generation) rare earth permanent magnet alloy based on NdFeB almost simultaneously in 1983, its huge magnetic energy product has refreshed the existing permanent magnet material record, causing a huge market for permanent magnet materials in the world. The change. The domestic development of NdFeB is very fast, and the annual production capacity of nearly 100 enterprises in the country has reached nearly 100,000 tons. As we all know, in the production process of NdFeB materials, there are many scraps, defective products and scraps from cutting and grinding, and the total loss is as high as more than 30%. Therefore, it is important to strengthen the research and production of NdFeB waste recycling. significance.

As the technology of recovering rare earths from NdFeB waste becomes more and more mature, more and more businesses see the huge profits. According to data, in Zhejiang and Guangdong, there are thousands of large and small manufacturers recycling NdFeB waste. Among them, there are many underground black workshops without production qualifications. They only use the NdFeB waste obtained, especially the oil sludge after grinding and wire cutting, for rough oxidation and roasting, and then through acid dissolution and other processes. In order to extract the rare earth elements. Because these businesses have neither production license nor formal production process. Therefore, this method is not only a great waste of rare earth resources, but also causes huge pollution to the local environment.

For the research object of this patent, NdFeB sludge, how to re-prepare regenerated NdFeB magnetic powder from NdFeB sludge is the research core of this subject. It has been reported in the literature that someone has successfully prepared a hard magnetic phase with a magnetic product energy of up to 40KOe by using the Fe-Pr and Fe-Nd phases with a rapid quenching process. Domestic Xiao Yaofu, Zhou Shouzeng and others have successfully produced NdFeB by reduction diffusion method. In this method, NdO powder, Fe powder, and Ca powder are mixed and compacted, then reduced and diffused at 860°C-1180°C, and then formed and sintered to obtain a magnetic energy product (BH) max=200-238KJ/m ³ NdFeB alloy. Sun Guangfei and Chen Jufang also prepared NdFeB alloys by using the reduction fusion method. The reduction fusion method is to reduce neodymium chloride by metal calcium, and then fuse the reduced metal neodymium with alloying elements iron and boron under high temperature conditions to obtain NdFeB alloy. AngshumanPal, Alexander Gabay, GeorgeC.Hadjipanayis and others have prepared NdFeB alloy and Nd-rich phase by ball milling NdO powder, iron-boron alloy, calcium powder and heat treatment, and the coercive force of NdFeB alloy exceeds 12KOe. It was also successfully prepared NdFeB nanocrystals and nanosheets by adding surfactants in high energy ball milling. Therefore, the preparation of NdFeB alloys by mechanochemical synthesis is worthy of reference.

The applicant intends to use NdFeB oil sludge-physical method to separate solid-liquid phase in oil sludge-solid phase acid solution-NdFe co-precipitation-high temperature calcination-mechanochemical method to synthesize NdFeB magnetic powder process, and acid-soluble precipitation method, sulfuric acid double salt precipitation method, Compared with the separation-purification method of the total extraction method, NdFeB is prepared directly through the NdFeB sludge-physical method to separate the solid-liquid phase in the sludge-solid phase acid solution-NdFe co-precipitation-high temperature calcination-mechanochemical method to synthesize NdFeB magnetic powder The alloy method can further reduce costs, reduce complicated chemical processes, save human resources and material resources, and also reduce the discharge of waste water and liquid, and realize the recovery of all elements and a true circular economy.

NdFeB oil sludge contains five elements that can be recycled and reproduced: neodymium, praseodymium, dysprosium, cobalt, and iron. To prepare NdFeB regenerated magnetic powder, at the same time, neodymium, praseodymium, dysprosium, cobalt, and iron are precipitated at a high recovery rate to become The essential.

Contents of the invention

In this patent, the five elements of neodymium, praseodymium, dysprosium, cobalt and iron will be calculated and simulated first to establish a thermodynamic model, and the optimal process for simultaneous recovery of neodymium, praseodymium, dysprosium, cobalt and iron will be determined and optimized through the thermodynamic model and the optimum parameters of the process.

The present invention aims to establish a thermodynamic model of the five elements of neodymium, praseodymium, dysprosium, cobalt and iron under the C ₂ H ₂ O ₄ -NH ₃ system, and determine the coordination of neodymium, praseodymium, dysprosium, cobalt and iron recovery by referring to the simulation results -Precipitation process selection, through the determined process plan to simultaneously recover the compounds of the five elements of neodymium, praseodymium, dysprosium, cobalt, and iron, and the recovered products can be used for the preparation of recycled NdFeB.

The present invention determines the method for simultaneously recovering neodymium, praseodymium, dysprosium, cobalt, and iron from NdFeB oil sludge under the _{C2H2O4 - NH3} system _. The complexation reactions that may occur in the C ₂ H ₂ O ₄ -NH ₃ system and the reaction equilibrium constants, establish a thermodynamic model (preferably through MATLAB calculation software); then, determine the recovery of neodymium, praseodymium, dysprosium, and cobalt through the established thermodynamic model 1. The process of iron and the selection of parameters in the process: under the C ₂ H ₂ O ₄ -NH ₃ system, the determined process is: NdFeB sludge distillation, acid dissolution, oxidation, and complex precipitation to obtain products.

The establishment of the above thermodynamic model (that is, the thermodynamic model after precipitation equilibrium) includes the following steps: First, review the possible reactions of neodymium, praseodymium, dysprosium, cobalt, and iron under the C ₂ H ₂ O ₄ -NH ₃ system and the possible reactions of each reaction. The equilibrium constant of , the equation can be obtained from the ionization balance of water:

[H ⁺ ]=10 ^-pH (1-1)

[OH-]=Kw*10 ^pH (1-2)

In the C ₂ H ₂ O ₄ -OH system, the concentration of free metal ions in the solution is:

[Nd ³⁺ ]=min{(Kspnac/[C ₂ O ₄ ^2- ] ³ ) ^1/2 ,Kspnh/[OH ^- ] ³ }(1-3)

[Pr ³⁺ ]==min{(Ksppac/[C ₂ O ₄ ^2- ] ³ ) ^1/2 ,KsppH/[OH ^- ] ³ }(1-4)

[Dy ³⁺ ]=min{(Kspdac/[C ₂ O ₄ ^2- ] ³ ) ^1/2 ,Kspdh/[OH ^- ] ³ }(1-5)

[Fe ³⁺ ]=Kspf3h/[OH ^- ] ³ (1-6)

[Fe ²⁺ ]=min{Kspf2ac/[C ₂ O ₄ ^2- ],Kspf3h/[OH ^- ] ² }(1-7)

[Co ²⁺ ]=Kspch/[OH ^- ] ² (1-8)

[H ₂ C ₂ O ₄ ]=[C ₂ O ₄ ^2- ]+[HC ₂ O ₄ ^- ]+[C ₂ H ₂ O ₄ ](1-9)

[H ₂ C ₂ O ₄ ]=[C ₂ O ₄ ^2- ]{1+10 ^-pH /K _aac2 +10 ^-2pH /(K _aac2 *K _aac1 )}(1-10)

Since each metal ion reacts with [OH ^- ], [NH ₃ ], [C ₂ O ₄ ^2- ], the total concentration of each metal ion in the solution is obtained according to the law of conservation of mass:

[Nd]=[Nd ³⁺ ]+[Nd(OH) ²⁺ ]+[Nd(C ₂ O ₄ ) ⁺ ]+[Nd(C ₂ O ₄ ) ₂ ^- ]+

[Nd(C ₂ O ₄ ) ₃ ^3- ]

=[Nd ³⁺ ]+K _nh *[Nd ³⁺ ]*[OH-]+K _nac11 *[Nd ³⁺ ]*[C ₂ O ₄ ^2- ]

+K _nac12 *[Nd ³⁺ ]*[C ₂ O ₄ ^2- ] ² +K _nac13 *[Nd ³⁺ ]*[C ₂ O ₄ ^2- ] ³ (1-11)

[Pr]=[Pr ³⁺ ]+[Pr(OH) ²⁺ ]+[Pr(C ₂ O ₄ ) ⁺ ]+[Pr(C ₂ O ₄ ) ₂ ^- ]

+[Pr(C ₂ O ₄ ) ₃ ^3- ](1-12)

[Dy]=[Dy ³⁺ ]+[Dy(OH) ²⁺ ]+[Dy(C ₂ O ₄ ) ⁺ ]+[Dy(C ₂ O ₄ ) ₂ ^- ]+

[D _y (C ₂ O ₄ ) ₃ ^3- ](1-13)

[Fe2]=[Fe ²⁺ ]+[Fe(OH) ⁺ ]+[Fe(OH) ₂ ⁰ ]+[Fe(OH) ₃ ^- ]+[Fe(OH) ₄ ^2- ]

+[Fe(C ₂ O ₄ ) ⁰ ]+[Fe(C ₂ O ₄ ) ₂ ^2- ]+[Fe(C ₂ O ₄ ) ₃ ^4- ]+[Fe(NH ₃ ) ²⁺ ]

+[Fe(NH ₃ ) ₂ ²⁺ ]+[Fe(NH ₃ ) ₄ ²⁺ ]

=[Fe ²⁺ ]{1+K _f2h1 *[OH ^- ]+K _f2h2 *[OH ^- ] ² +K _f2h3 *[OH ^- ] ³ +K _f2h4 *[OH ^- ] ⁴

+K _nac11 *[C ₂ O ₄ ^2- ]+K _nac12 *[C ₂ O ₄ ^2- ] ² +K _nac13 *[C ₂ O ₄ ^2- ] ³

+K _f2am11 *[NH ₃ ]+K _f2am12 *[NH ₃ ] ² +K _f2am14 *[NH ₃ ] ⁴ }

(1-14)

[Fe3]=[Fe ³⁺ ]+[Fe(OH) ²⁺ ]+[Fe(OH) ₂ ⁺ ]+[Fe(OH) ₃ ⁰ ]+[Fe(OH) ₄ ^2- ]

=[Fe ³⁺ ]{1+K _f3h1 *[OH ^- ]+K _f3h2 *[OH ^- ] ² +K _f3h3 *[OH ^- ] ³ }

(1-15)

[Co]=[Co ²⁺ ]+[Co(OH) ⁺ ]+[Co(OH) ₂ ⁰ ]+[Co(OH) ₃ ^- ]+[Co(OH) ₄ ^2- ]

+2*[Co ₂ (OH) ₃ ^3- ]+4*[Co ₄ (OH) ₄ ^4- ]+[Co(NH ₃ )]

+[Co(NH ₃ ) ²⁺ ]+[Co(NH ₃ ) ₂ ²⁺ ]+[Co(NH ₃ ) ₃ ²⁺ ]+[Co(NH ₃ ) ₄ ²⁺ ]

+[Co(NH ₃ ) ₅ ²⁺ ]+[Co(NH ₃ ) ₆ ²⁺ ]

=[Co ²⁺ ]{1+K _ch1 *[OH ^- ]+K _ch2 *[OH ^- ] ² +K _ch3 *[OH ^- ] ³

+K _ch4 *[OH ^- ] ⁴ +2*K _ch21 *[Co ²⁺ ]*[OH ^- ]+4*K _ch44 *[Co ²⁺ ] ³ *[OH ^- ] ⁴

+K _cam11 *[NH ₃ ]+K _cam12 *[NH ₃ ] ² +K _cam13 *[NH ₃ ] ³

+K _cam14 *[NH ₃ ] ⁴ +K _cam15 *[NH ₃ ] ⁵ +K _cam16 *[NH ₃ ] ⁶ }(1-16)

[NH ₄ ⁺ ]=K _am *[NH ₃ ]*[H ⁺ ](1-17)

[N]=[NH ₃ ]+[NH ₄ ⁺ ]+[Fe(NH ₃ ) ²⁺ ]+[Fe(NH ₃ ) ₂ ²⁺ ]+[Fe(NH ₃ ) ₄ ²⁺

+[Co(NH ₃ )]+[Co(NH ₃ ) ²⁺ ]+[Co(NH ₃ ) ₂ ²⁺ ]+[Co(NH ₃ ) ₃ ²⁺ ]+

[Co(NH ₃ ) ₄ ²⁺ ]+[Co(NH ₃ ) ₅ ²⁺ ]+[Co(NH ₃ ) ₆ ²⁺ ](1-18)

Use the parameters in Table 1 for the above formulas (1-1)-(1-18), by changing the amount of [OH ^- ], through chemical balance, mass balance, and charge conservation to establish in C ₂ H ₂ O ₄ -NH ₃ Thermodynamic model under the system.

The optimal model is calculated by MATLAB assembly language:

x=0:0.5:14;

u=0.1

p=u./(1+10.^(1.23-x)+10.^(5.42-2.*x))

P=1./(1+10.^(9.244-x))

a=min(2*sqrt(10^(-27.68)./p.^3),10.^(20.5-3*x))

b=10.^(11.69-2.*x);

c=10.^(3.45-3.*x);

w=10.^(13.77-2*x);

e=min(2*sqrt(10^(-27.68)./p.^3),10.^(21.17-3*x));

i=min(2*sqrt(10^(-28.8)./p.^3),10.^(21.85-3*x));

j=a.*[1+10^7.21.*p+10^11.5.*p.^2+10^14.*p.^3+10.^(x-8.5)];

g=b.*[1+10^2.9.*p+10^4.52.*p.^2+10^5.22.*p.^3+10.^(x-8.44)+10.^(2* x-18.23)+10.^(3*x-32.33)+10.^(4*x-47.72)+10^1.4.*P+10^2.2.*P.^2+10^3.74.*P .^4];

h=c.*[1+10^9.4.*p+10^16.2.*p.^2+10^20.2.*p.^3+10.^(x-2.13)+10.^(2* x-6.83)+10.^(3*x-12.33)];

q=w.*(1+10.^(x-10.7)+10.^(2.*x-18.8)+10.^(3.*x-31.5)+10.^(4.*x- 45.8)+2.*10.^(x-11.3).*w+4.*10.^(4.*x-30.4).^(w.^3)+10^4.79.^p+10^ 6.7.*p.^2+10^9.7.*p.^3+10^2.11.^P+10^3.74.*P.^2+10^4.99.*P.^3+10^5.55.* P.^4+10^5.73.*P.^5+10^5.11.*P.^6);

r=e.*(1+10^7.21.*p+10^10.5.*p.^2+10^14.*p.^3+10.^(x-9.7));

l=i.*(1+10^7.21.*p+10^11.9.*p.^2+10^14.*p.^3+10.^(x-8.8));

y=log10(j);

m=log10(g);

n=log10(h);

o=log10(q)

t=log10(r)

z=log10(l)

plot(x,y,x,m,x,n,x,o,x,t,x,z)

Among them, x represents the pH value; u represents the concentration of total oxalic acid [H ₂ C ₂ O ₄ ]; _p represents the concentration of C ₂ O ₄ ^2- in the solution; a, b, c, w, e, i represent [Nd ], [Fe2], [Fe3], [Co], [Dy], [Pr] free metal ion concentration values; P represents the value of free state [NH ₃ ]; j, g, h, q, r, l respectively Represents the remaining total concentration of [Nd], [Fe2], [Fe3], [Co], [Dy], [Pr] solution; y, m, n, o, t, z respectively represent [Nd] , [Fe2], [Fe3], [Co], [Dy], [Pr] The remaining total concentration in the solution is logarithmic value with base 10.

_The present invention uses the above method to determine a method for simultaneously recovering neodymium, praseodymium, dysprosium, cobalt, and iron from NdFeB sludge under the _{C2H2O4 - NH3} system, which is characterized in that it comprises the following steps: After the iron-boron sludge is pretreated by distillation, take hydrochloric acid to dissolve the pretreated NdFeB sludge and filter it, add H ₂ O ₂ , stir and oxidize fully, add NH ₄ OH to adjust the pH=0.5-2.5, and add C ₂ After fully stirring the H ₂ O ₄ solution, NH ₄ OH was added again to adjust the pH to 9, and the obtained precipitate was filtered, washed three times, and dried to obtain a product that could be used to prepare regenerated NdFeB.

For each 5 g of the above, preferably, the NdFeB oil sludge corresponds to 75 ml of 4 mol/L hydrochloric acid, 3 ml of H ₂ O ₂ , 1 mol/L of NH ₄ OH, and 32 ml of 1 mol/L of C ₂ H ₂ O ₄ solution.

Trivalent iron ions should be selected as much as possible, and it can be seen from the model that the optimal recovery pH value of neodymium, praseodymium and dysprosium rare earth salt should be within 0.5 to 2.5, and the recovery of iron and cobalt should be at a high pH value. Therefore, this The patented design process is completed by adjusting the pH twice. The pH range for the optimal precipitation of neodymium, praseodymium, dysprosium, cobalt, and iron should be within (0.5-2.5)-9, and neodymium, praseodymium, dysprosium, cobalt, and Iron complex precipitation product. The recovery rate of neodymium>=99%; the recovery rate of praseodymium>=99%; the recovery rate of cobalt>=79%; the recovery rate of dysprosium>=99%; the recovery rate of iron>=99%.

The beneficial effects of the present invention are:

(1) It overcomes the previous complex exploration of simultaneously recovering five elements of neodymium, praseodymium, dysprosium, cobalt, and iron, and provides a simple simulation method.

(2) The valuable elements in the NdFeB oil sludge are better recovered, reducing the waste of elements; through one-time process recovery, the current situation that multiple processes are required to recover multiple elements is improved and optimized, and the operation is simple. The method works.

Description of drawings

Figure 1C ₂ H ₂ O ₄ -NH ₃ system in the neodymium, iron, cobalt, praseodymium, dysprosium concentration is affected by the change of pH value;

Figure 2C ₂ H ₂ O ₄ -NH ₃ system in the recovery of neodymium, iron, cobalt, praseodymium, dysprosium as a function of pH value.

detailed description

Below in conjunction with example the present invention is further described.

Example 1

Table 1 The main chemical reactions and equilibrium constants involved in the "C ₂ H ₂ O ₄ -NH3" system

No. Reactions logK No. Reactions logK 1 H ₂ O=H ⁺ +OH ^— logK _w =-14 25 Fe ²⁺ +4OH ^— =Fe(OH) ₄ ^2— logK _f2h4 =18.58 2 Co ²⁺ +OH ^— =Co(OH) ⁺ logK _ch1 =3.3 26 Fe ³⁺ +OH ^— =Fe(OH) ²⁺ logK _f3h1 =11.87 3 Co ²⁺ +2OH ^— =Co(OH) ₂ ⁰ logK _ch2 =9.2 27 Fe ³⁺ +2OH ^— =Fe(OH) ₂ ⁺ logK _f3h2 =21.17 4 Co ²⁺ +3OH ^— =Co(OH) ₃ ^— logK _ch3 =10.5 28 Fe ³⁺ +3OH ^— =Fe(OH) ₃ ⁰ logK _f3h3 =29.67 5 Co ²⁺ +4OH ^— =Co(OH) ₄ ^2- logK _ch4 =10.2 29 Co ²⁺ +NH ₃ =Co(NH ₃ ) ²⁺ logK _cam11 =2.11 6 2Co ²⁺ +OH ^— =Co ₂ (OH) ³⁺ logK _ch21 =2.7 30 Co ²⁺ +2NH ₃ =Co(NH ₃ ) ₂ ²⁺ logK _cam12 =3.74 7 4Co ²⁺ +4OH ^— =Co ₄ (OH) ₄ ⁴⁺ logK _ch44 =25.6 31 Co ²⁺ +3NH ₃ =Co(NH ₃ ) ₃ ²⁺ logK _cam13 =4.79 8 Fe ²⁺ +OH ^— =Fe(OH) ⁺ logK _f2h1 =5.56 32 Co ²⁺ +4NH ₃ =Co(NH ₃ ) ₄ ²⁺ logK _cam14 =5.55 9 Fe ²⁺ +2OH ^— =Fe(OH) ₂ ⁰ logK _f2h2 =9.77 33 Co ²⁺ +5NH ₃ =Co(NH ₃ ) ₅ ²⁺ logK _cam15 =5.73 10 Fe ²⁺ +3OH ^— =Fe(OH) ₃ ^— logK _f2h3 =9.67 34 Co ²⁺ +6NH ₃ =Co(NH ₃ ) ₆ ²⁺ logK _cam16 =5.11 11 Nd+OH ^— =Nd(OH) ²⁺ logK _nh =5.5 35 Fe ²⁺ +NH ₃ =Fe(NH ₃ ) ²⁺ logK _f2am11 =1.4 12 Pr+OH ^— =Pr(OH) ²⁺ logK _pH =4.3 36 Fe ²⁺ +2NH ₃ =Fe(NH ₃ ) ₂ ²⁺ logK _f2am12 =2.2 13 Dy+OH ^— =Dy(OH) ²⁺ logK _dh =5.2 37 Fe ²⁺ +4NH ₃ =Fe(NH ₃ ) ₄ ²⁺ logK _f2am13 =3.74 14 Co(OH) ₂ (s)=Co ²⁺ +2OH ^— logKspch=-14.23 38 Fe C ₂ O ₄ (s)=Fe ²⁺ +C ₂ O ₄ ^2— logKspf2ac=-6.5 15 Fe(OH) ₂ (s)=Fe ²⁺ +2OH ^— logKspf2h=-16.31 39 Fe ²⁺ +C ₂ O ₄ ^2— =Fe(C ₂ O ₄ ) ⁰ logK _f2ac11 =2.9 16 Fe(OH) ₃ (s)=Fe ³⁺ +3OH ^— logKspf3h=-38.55 40 Fe ²⁺ +2C ₂ O ^2— =Fe(C ₂ O ₄ ) ₂ ^2— logK _f2ac12 =4.52 17 Nd(OH) ₃ (s)=Nd ³⁺ +3OH ^— logKspnh=-21.49 41 Fe ²⁺ +3C ₂ O ₄ ^2- =Fe(C ₂ O ₄ ) ₃ ^4— logK _f2ac13 =5.22 18 Pr(OH) ₃ (s)=Pr ³⁺ +3OH ^— logKsppH=-21.17 42 Fe ³⁺ +C ₂ O ₄ ^2— =Fe(C ₂ O ₄ ) ⁺ logK _f3ac11 =9.4 19 Dy(OH) ₃ (s)=Dy ³⁺ +3OH ^— logKspdh=-21.85 43 Fe ³⁺ +2C ₂ O ₄ ^2— =Fe(C ₂ O ₄ ) ₂ ^— logK _f3ac12 =16.2 20 Nd+OH ^— =Nd(OH) ²⁺ logK _nh =5.5 44 Fe ³⁺ +3C ₂ O ₄ ^2- =Fe(C ₂ O ₄ ) ₃ ^3— logK _f3ac13 =20.2 twenty one NH ₃ +H ⁺ =NH ₄ ⁺ log K _am =9.246 45 H ₂ C ₂ O ₄ =H ⁺ +HC ₂ O ₄ ^— logK _ac1 =1.23 twenty two Nd ₂ (C ₂ O ₄ ) ₃ (s)=2Nd ²⁺ +3C ₂ O ₄ ^2— logKspdac=-27.68 46 HC ₂ O ₄ ^— =H ⁺ +C ₂ O ₄ ^2— logK _ac2 =-5.42 twenty three Nd ³⁺ +C ₂ O ₄ ^2— =Nd(C ₂ O ₄ ) ⁺ logK _nac11 =7.21 47 Co ²⁺ +C ₂ O ₄ ^2— =Co(C ₂ O ₄ ) ⁰ logKcac11=4.79 twenty four Nd ³⁺ +2C ₂ O ₄ ^2— =Nd(C ₂ O ₄ ) ₂ ^— logK _nac12 =11.5 48 Co ²⁺ +2C ₂ O ₄ ^2— =Co(C ₂ O ₄ ) ₂ ^2— logKcac12=6.7 25 Nd ³⁺ +3C ₂ O ₄ ^2— =Nd(C ₂ O ₄ ) ₃ ^3— logK _nac13 =17 49 Co ²⁺ +3C ₂ O ₄ ^2— =Co(C ₂ O ₄ ) ₃ ^4— logKcac13=9.7

In the theoretical part: First, check the possible reactions of neodymium, praseodymium, dysprosium, cobalt, and iron under the C ₂ H ₂ O ₄ -NH ₃ system and the equilibrium constants of each reaction, as shown in Table 1. The thermodynamic model under the C ₂ H ₂ O ₄ -NH ₃ system is established through chemical balance, mass balance and charge conservation, and the equation can be obtained from the ionization balance of water:

[H ⁺ ]=10 ^-pH (1-1)

[OH ^- ]=Kw*10 ^pH (1-2)

In the C ₂ H ₂ O ₄ -OH system, the concentration of free metal ions in the solution is:

[Nd ³⁺ ]=min{(Kspnac/[C ₂ O ₄ ^2- ] ³ ) ¹ / ² ,Kspnh/[OH ^- ] ³ }(1-3)

[Pr ³⁺ ]==min{(Ksppac/[C ₂ O ₄ ^2- ] ³ ) ^1/2 ,KsppH/[OH ^- ] ³ }(1-4)

[Dy ³⁺ ]=min{(Kspdac/[C ₂ O ₄ ^2- ] ³ ) ^1/2 ,Kspdh/[OH ^- ] ³ }(1-5)

[Fe ³⁺ ]=Kspf3h/[OH ^- ] ³ (1-6)

[Fe ²⁺ ]=min{Kspf2ac/[C ₂ O ₄ ^2- ],Kspf3h/[OH ^- ] ² }(1-7)

[Co ²⁺ ]=Kspch/[OH ^- ] ² (1-8)

[H ₂ C ₂ O ₄ ]=[C ₂ O ₄ ^2- ]+[HC ₂ O ₄ ^- ]+[C ₂ H ₂ O ₄ ](1-9)

[H ₂ C ₂ O ₄ ]=[C ₂ O ₄ ^2- ]{1+10 ^-pH /K _aac2 +10 ^-2pH /(K _aac2 *K _aac1 )}(1-10)

Since each metal ion reacts with [OH ^- ], [NH ₃ ], [C ₂ O ₄ ^2- ], the total concentration of each metal ion in the solution is obtained according to the law of conservation of mass:

[Nd]=[Nd ³⁺ ]+[Nd(OH) ²⁺ ]+[Nd(C ₂ O ₄ ) ⁺ ]+[Nd(C ₂ O ₄ ) ₂ ^- ]+

[Nd(C ₂ O ₄ ) ₃ ^3- ]

=[Nd ³⁺ ]+K _nh *[Nd ³⁺ ]*[OH-]+K _nac11 *[Nd ³⁺ ]*[C ₂ O ₄ ^2- ]

+K _nac12 *[Nd ³⁺ ]*[C ₂ O ₄ ^2- ] ² +K _nac13 *[Nd ³⁺ ]*[C ₂ O ₄ ^2- ] ³ (1-11)

[Pr]=[Pr ³⁺ ]+[Pr(OH) ²⁺ ]+[Pr(C ₂ O ₄ ) ⁺ ]+[Pr(C ₂ O ₄ ) ₂ ^- ]

+[Pr(C ₂ O ₄ ) ₃ ^3- ](1-12)

[Dy]=[Dy ³⁺ ]+[Dy(OH) ²⁺ ]+[Dy(C ₂ O ₄ ) ⁺ ]+[Dy(C ₂ O ₄ ) ₂ ^- ]+

[Dy(C ₂ O ₄ ) ₃ ^3- ](1-13)

[Fe2]=[Fe ²⁺ ]+[Fe(OH) ⁺ ]+[Fe(OH) ₂ ⁰ ]+[Fe(OH) ₃ ^- ]+[Fe(OH) ₄ ^2- ]

+[Fe(C ₂ O ₄ ) ⁰ ]+[Fe(C ₂ O ₄ ) ₂ ^2- ]+[Fe(C ₂ O ₄ ) ₃ ^4- ]+[Fe(NH ₃ ) ²⁺ ]

+[Fe(NH ₃ ) ₂ ²⁺ ]+[Fe(NH ₃ ) ₄ ²⁺ ]

=[Fe ²⁺ ]{1+K _f2h1 *[OH ^- ]+K _f2h2 *[OH ^- ] ² +K _f2h3 *[OH ^- ] ³ +K _f2h4 *[OH ^- ] ⁴

+K _nac11 *[C ₂ O ₄ ^2- ]+K _nac12 *[C ₂ O ₄ ^2- ] ² +K _nac13 *[C ₂ O ₄ ^2- ] ³

+K _f2am11 *[NH ₃ ]+K _f2am12 *[NH ₃ ] ² +K _f2am14 *[NH ₃ ] ⁴ }

(1-14)

[Fe3]=[Fe ³⁺ ]+[Fe(OH) ²⁺ ]+[Fe(OH) ₂ ⁺ ]+[Fe(OH) ₃ ⁰ ]+[Fe(OH) ₄ ^2- ]

=[Fe ³⁺ ]{1+K _f3h1 *[OH ^- ]+K _f3h2 *[OH ^- ] ² +K _f3h3 *[OH ^- ] ³ }

(1-15)

[Co]=[Co ²⁺ ]+[Co(OH) ⁺ ]+[Co(OH) ₂ ⁰ ]+[Co(OH) ₃ ^- ]+[Co(OH) ₄ ^2- ]

+2*[Co ₂ (OH) ₃ ^3- ]+4*[Co ₄ (OH) ₄ ^4- ]+[Co(NH ₃ )]

+[Co(NH ₃ ) ²⁺ ]+[Co(NH ₃ ) ₂ ²⁺ ]+[Co(NH ₃ ) ₃ ²⁺ ]+[Co(NH ₃ ) ₄ ²⁺ ]

+[Co(NH ₃ ) ₅ ²⁺ ]+[Co(NH ₃ ) ₆ ²⁺ ]

=[Co ²⁺ ]{1+K _ch1 *[OH ^- ]+K _ch2 *[OH ^- ] ² +K _ch3 *[OH ^- ] ³

+K _ch4 *[OH ^- ] ⁴ +2*K _ch21 *[Co ²⁺ ]*[OH ^- ]+4*K _ch44 *[Co ²⁺ ] ³ *[OH ^- ] ⁴

+K _cam11 *[NH ₃ ]+K _cam12 *[NH ₃ ] ² +K _cam13 *[NH ₃ ] ³

+K _cam14 *[NH ₃ ] ⁴ +K _cam15 *[NH ₃ ] ⁵ +K _cam16 *[NH ₃ ] ⁶ }(1-16)

[NH ₄ ⁺ ]=K _am *[NH ₃ ]*[H ⁺ ](1-17)

[N]=[NH ₃ ]+[NH ₄ ⁺ ]+[Fe(NH ₃ ) ²⁺ ]+[Fe(NH ₃ ) ₂ ²⁺ ]+[Fe(NH ₃ ) ₄ ²⁺

+[Co(NH ₃ )]+[Co(NH ₃ ) ²⁺ ]+[Co(NH ₃ ) ₂ ²⁺ ]+[Co(NH ₃ ) ₃ ²⁺ ]+

[Co(NH ₃ ) ₄ ²⁺ ]+[Co(NH ₃ ) ₅ ²⁺ ]+[Co(NH ₃ ) ₆ ²⁺ ](1-18)

Simultaneous formula (1-1)～(1-18), and bring the values in Table 1 into (1-1)～(1-18), which can be converted into MATLAB assembly language:

x=0:0.5:14;

u=0.1

p=u./(1+10.^(1.23-x)+10.^(5.42-2.*x))

P=1./(1+10.^(9.244-x))

a=min(2*sqrt(10^(-27.68)./p.^3),10.^(20.5-3*x))

b=10.^(11.69-2.*x);

c=10.^(3.45-3.*x);

w=10.^(13.77-2*x);

e=min(2*sqrt(10^(-27.68)./p.^3),10.^(21.17-3*x));

i=min(2*sqrt(10^(-28.8)./p.^3),10.^(21.85-3*x));

j=a.*[1+10^7.21.*p+10^11.5.*p.^2+10^14.*p.^3+10.^(x-8.5)];

g=b.*[1+10^2.9.*p+10^4.52.*p.^2+10^5.22.*p.^3+10.^(x-8.44)+10.^(2* x-18.23)+10.^(3*x-32.33)+10.^(4*x-47.72)+10^1.4.*P+10^2.2.*P.^2+10^3.74.*P .^4];

h=c.*[1+10^9.4.*p+10^16.2.*p.^2+10^20.2.*p.^3+10.^(x-2.13)+10.^(2* x-6.83)+10.^(3*x-12.33)];

q=w.*(1+10.^(x-10.7)+10.^(2.*x-18.8)+10.^(3.*x-31.5)+10.^(4.*x- 45.8)+2.*10.^(x-11.3).*w+4.*10.^(4.*x-30.4).^(w.^3)+10^4.79.^p+10^ 6.7.*p.^2+10^9.7.*p.^3+10^2.11.^P+10^3.74.*P.^2+10^4.99.*P.^3+10^5.55.* P.^4+10^5.73.*P.^5+10^5.11.*P.^6);

r=e.*(1+10^7.21.*p+10^10.5.*p.^2+10^14.*p.^3+10.^(x-9.7));

l=i.*(1+10^7.21.*p+10^11.9.*p.^2+10^14.*p.^3+10.^(x-8.8));

y=log10(j);

m=log10(g);

n=log10(h);

o=log10(q)

t=log10(r)

z=log10(l)

plot(x,y,x,m,x,n,x,o,x,t,x,z)

Among them, x represents the pH value; u represents the concentration of total oxalic acid [H ₂ C ₂ O ₄ ]; p represents the concentration of C ₂ O ₄ ^2- in the solution; a, b, c, w, e, i represent [Nd ], [Fe2], [Fe3], [Co], [Dy], [Pr] free metal ion concentration values; P represents the value of free state [NH ₃ ]; j, g, h, q, r, l respectively Represents the remaining total concentration of [Nd], [Fe2], [Fe3], [Co], [Dy], [Pr] solution; y, m, n, o, t, z respectively represent [Nd] , [Fe2], [Fe3], [Co], [Dy], [Pr] The remaining total concentration in the solution is logarithmic value with base 10. The lg[ME]-pH thermodynamic model is obtained by changing the value of pH (Figure 1).

As shown in Figure 1. According to Figure 1, it can be considered that trivalent iron ions should be selected as much as possible, and it can be seen that the optimal recovery pH value of neodymium, praseodymium and dysprosium rare earth salts should be within 0.5 to 2.5, while the recovery of iron and cobalt should be at a high pH value Therefore, the patent design process is completed by adjusting the pH twice. The pH range of the optimal precipitation of neodymium, praseodymium, dysprosium, cobalt, and iron should be within (0.5-2.5)-9, and neodymium, praseodymium, and Dysprosium, cobalt, iron complex precipitation product.

In the experimental part: take five parts of 5g NdFeB sludge for distillation pretreatment, respectively take 75ml of 4mol/L hydrochloric acid to dissolve and filter the pretreated NdFeB sludge, add 3ml content to 30%.wt After fully oxidizing the H ₂ O ₂ , add 1 mol/L NH ₄ OH to adjust the pH=0.5, and add 32ml of 1 mol/L C ₂ H ₂ O ₄ solution, stir well, add 1 mol/L NH ₄ OH to adjust the pH to 9, filter the obtained precipitate, wash it three times, and dry it to obtain a product that can be used to prepare regenerated NdFeB. Get supernatant and carry out ICP-OES test, the result obtained is as shown in Figure 2: the recovery rate of neodymium: 99%; The recovery rate of iron: 99%; The recovery rate of cobalt: 79%; The recovery rate of praseodymium For: 99%; dysprosium recovery rate: 99%.

Example 2

Table 1 The main chemical reactions and equilibrium constants involved in the "C ₂ H ₂ O ₄ -NH3" system

In the theoretical part: First, check the possible reactions of neodymium, praseodymium, dysprosium, cobalt, and iron under the C ₂ H ₂ O ₄ -NH ₃ system and the equilibrium constants of each reaction, as shown in Table 1. The thermodynamic model under the C ₂ H ₂ O ₄ -NH ₃ system is established through chemical balance, mass balance and charge conservation, as shown in Figure 1. According to Figure 1, it can be considered that trivalent iron ions should be selected as much as possible, and it can be seen that the optimal recovery pH value of neodymium, praseodymium and dysprosium rare earth salts should be within 0.5 to 2.5, while the recovery of iron and cobalt should be at a high pH value Therefore, the patent design process is completed by adjusting the pH twice. The pH range of the optimal precipitation of neodymium, praseodymium, dysprosium, cobalt, and iron should be within (0.5-2.5)-9, and neodymium, praseodymium, and Dysprosium, cobalt, iron complex precipitation product.

In the experimental part: take five parts of 5g NdFeB sludge for distillation pretreatment, respectively take 75ml of 4mol/L hydrochloric acid to dissolve and filter the pretreated NdFeB sludge, add 3ml content to 30%.wt After fully oxidizing the H ₂ O ₂ , add 1mol/L NH ₄ OH to adjust the pH=1, and add 32ml of 1mol/L C ₂ H ₂ O ₄ solution, stir well, then add 1mol/L NH ₄ OH to adjust the pH to 9, filter the obtained precipitate, wash it three times, and dry it to obtain a product that can be used to prepare regenerated NdFeB. Get supernatant and carry out ICP-OES test, the result obtained is as shown in Figure 2: the recovery rate of neodymium: 99%; The recovery rate of iron: 99%; The recovery rate of cobalt: 79%; The recovery rate of praseodymium For: 99%; dysprosium recovery rate: 99%.

Example 3

Table 1 The main chemical reactions and equilibrium constants involved in the "C ₂ H ₂ O ₄ -NH3" system

In the theoretical part: First, check the possible reactions of neodymium, praseodymium, dysprosium, cobalt, and iron under the C ₂ H ₂ O ₄ -NH ₃ system and the equilibrium constants of each reaction, as shown in Table 1. The thermodynamic model under the C ₂ H ₂ O ₄ -NH ₃ system is established through chemical balance, mass balance and charge conservation, as shown in Figure 1. According to Figure 1, it can be considered that trivalent iron ions should be selected as much as possible, and it can be seen that the optimal recovery pH value of neodymium, praseodymium and dysprosium rare earth salts should be within 0.5 to 2.5, while the recovery of iron and cobalt should be at a high pH value Therefore, the patent design process is completed by adjusting the pH twice. The pH range of the optimal precipitation of neodymium, praseodymium, dysprosium, cobalt, and iron should be within (0.5-2.5)-9, and neodymium, praseodymium, and Dysprosium, cobalt, iron complex precipitation product.

In the experimental part: take five parts of 5g NdFeB sludge for distillation pretreatment, respectively take 75ml of 4mol/L hydrochloric acid to dissolve and filter the pretreated NdFeB sludge, add 3ml content to 30%.wt After fully oxidizing the H ₂ O ₂ , add 1mol/L NH ₄ OH to adjust the pH=1.5, and add 32ml of 1mol/L C ₂ H ₂ O ₄ solution, after fully stirring, add 1mol/L NH ₄ OH to adjust the pH to 9, filter the obtained precipitate, wash it three times, and dry it to obtain a product that can be used to prepare regenerated NdFeB. Get supernatant and carry out ICP-OES test, the result obtained is as shown in Figure 2: the recovery rate of neodymium: 99%; The recovery rate of iron: 99%; The recovery rate of cobalt: 78%; The recovery rate of praseodymium For: 99%; dysprosium recovery rate: 99%.

Example 4

Table 1 The main chemical reactions and equilibrium constants involved in the "C ₂ H ₂ O ₄ -NH3" system

In the theoretical part: First, check the possible reactions of neodymium, praseodymium, dysprosium, cobalt, and iron under the C ₂ H ₂ O ₄ -NH ₃ system and the equilibrium constants of each reaction, as shown in Table 1. The thermodynamic model under the C ₂ H ₂ O ₄ -NH ₃ system is established through chemical balance, mass balance and charge conservation, as shown in Figure 1. According to Figure 1, it can be considered that trivalent iron ions should be selected as much as possible, and it can be seen that the optimal recovery pH value of neodymium, praseodymium and dysprosium rare earth salts should be within 0.5 to 2.5, while the recovery of iron and cobalt should be at a high pH value Therefore, the patent design process is completed by adjusting the pH twice. The pH range of the optimal precipitation of neodymium, praseodymium, dysprosium, cobalt, and iron should be within (0.5-2.5)-9, and neodymium, praseodymium, and Dysprosium, cobalt, iron complex precipitation product.

In the experimental part: take five parts of 5g NdFeB sludge for distillation pretreatment, respectively take 75ml of 4mol/L hydrochloric acid to dissolve and filter the pretreated NdFeB sludge, add 3ml content to 30%.wt After fully oxidizing the H ₂ O ₂ , add 1 mol/L NH ₄ OH to adjust the pH=2, and add 32ml of 1 mol/L C ₂ H ₂ O ₄ solution, after fully stirring, add 1 mol/L NH ₄ OH to adjust the pH to 9, filter the obtained precipitate, wash it three times, and dry it to obtain a product that can be used to prepare regenerated NdFeB. Get supernatant and carry out ICP-OES test, the result obtained is as shown in Figure 2: the recovery rate of neodymium: 99%; The recovery rate of iron: 99%; The recovery rate of cobalt: 85%; The recovery rate of praseodymium For: 99%; dysprosium recovery rate: 99%.

Example 5

Table 1 The main chemical reactions and equilibrium constants involved in the "C ₂ H ₂ O ₄ -NH3" system

In the theoretical part: First, check the possible reactions of neodymium, praseodymium, dysprosium, cobalt, and iron under the C ₂ H ₂ O ₄ -NH ₃ system and the equilibrium constants of each reaction, as shown in Table 1. The thermodynamic model under the C ₂ H ₂ O ₄ -NH ₃ system is established through chemical balance, mass balance and charge conservation, as shown in Figure 1. According to Figure 1, it can be considered that trivalent iron ions should be selected as much as possible, and it can be seen that the optimal recovery pH value of neodymium, praseodymium and dysprosium rare earth salts should be within 0.5 to 2.5, while the recovery of iron and cobalt should be at a high pH value Therefore, the patent design process is completed by adjusting the pH twice. The pH range of the optimal precipitation of neodymium, praseodymium, dysprosium, cobalt, and iron should be within (0.5-2.5)-9, and neodymium, praseodymium, and Dysprosium, cobalt, iron complex precipitation product.

In the experimental part: take five parts of 5g NdFeB sludge for distillation pretreatment, respectively take 75ml of 4mol/L hydrochloric acid to dissolve and filter the pretreated NdFeB sludge, add 3ml content to 30%.wt After fully oxidizing the H ₂ O ₂ , add 1 mol/L NH ₄ OH to adjust the pH=2.5, and add 32ml of 1 mol/L C ₂ H ₂ O ₄ solution, after fully stirring, add 1 mol/L NH ₄ OH to adjust the pH to 9, filter the obtained precipitate, wash it three times, and dry it to obtain a product that can be used to prepare regenerated NdFeB. Get supernatant and carry out ICP-OES test, the result obtained is as shown in Figure 2: the recovery rate of neodymium: 99%; The recovery rate of iron: 99%; The recovery rate of cobalt: 87%; The recovery rate of praseodymium For: 99%; dysprosium recovery rate: 99%.

Claims (1)

1. _A method for simultaneously recovering neodymium, praseodymium, dysprosium, cobalt, and iron from NdFeB oil sludge under _{C2H2O4 - NH3} system, is characterized in that, comprises the following steps: carrying out NdFeB oil sludge After distillation pretreatment, take hydrochloric acid to dissolve and filter the pretreated NdFeB oil sludge, add H ₂ O ₂ , stir to fully oxidize, add NH ₄ OH to adjust pH=0.5-2.5, and add C ₂ H ₂ O ₄ After the solution is fully stirred, NH ₄ OH is added again to adjust the pH to 9, and the obtained precipitate is filtered, washed three times, and dried to obtain neodymium, praseodymium, dysprosium, cobalt, and iron that can be used to prepare regenerated NdFeB; For every 5g of NdFeB sludge, 75ml of 4mol/L hydrochloric acid, 3ml of H ₂ O ₂ , 1mol/L of NH ₄ OH, and 32ml of C ₂ H ₂ O ₄ solution of 1mol/L.