A method for simultaneously recovering rare earth and mercury from mercury-containing waste fluorescent powder

Abstract

The application provides a method for simultaneously recovering rare earth and mercury from mercury-containing waste fluorescent powder, and relates to the technical field of waste fluorescent powder recovery.The method for simultaneously recovering rare earth and mercury from mercury-containing waste fluorescent powder provided by the application comprises the following steps: mixing mercury-containing waste fluorescent powder, alkali and a reducing agent, performing reduction alkali smelting roasting to obtain roasted material and mercury-containing tail gas; performing water immersion on the roasted material to obtain water immersion residue; performing acid immersion on the water immersion residue to obtain acid immersion liquid; mixing the acid immersion liquid and oxalic acid solution, performing a precipitation reaction to obtain rare earth oxalate; and performing oxidation roasting on the rare earth oxalate to obtain rare earth oxide.The method directly processes mercury-containing waste fluorescent powder by using the reduction alkali smelting mode, and can simultaneously realize the extraction of rare earth and the recovery of mercury.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste fluorescent powder recycling, and particularly relates to a method for simultaneously recycling rare earth and mercury from waste fluorescent powder containing mercury. BACKGROUND

[0002] With the development of economy and technology, the amount of discarded rare earth fluorescent lamps is increasing, and the discarded lamps belong to hazardous waste, but contain valuable rare earth resources and mercury resources. In the existing waste fluorescent powder recycling technology, direct roasting mercury removal and alkali roasting rare earth extraction are important research directions, but there are the following problems: the direct roasting method is difficult to efficiently and deeply remove complex combined mercury, and the traditional alkali roasting product is insufficient in rare earth valence state regulation, resulting in low leaching rate; the existing process of separating mercury first and then recycling rare earth has the problems of long process and low efficiency. How to realize short-process and efficient comprehensive recovery of mercury / rare earth in waste fluorescent powder is a technical bottleneck restricting the development of the field. SUMMARY

[0003] The present application aims to provide a method for simultaneously recycling rare earth and mercury from waste fluorescent powder containing mercury, which directly processes the waste fluorescent powder containing mercury by using a reduction alkali roasting method, and can simultaneously realize extraction of rare earth and recovery of mercury.

[0004] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0005] The present application provides a method for simultaneously recycling rare earth and mercury from waste fluorescent powder containing mercury, comprising the following steps:

[0006] Mixing the waste fluorescent powder containing mercury, alkali and reducing agent, and performing reduction alkali roasting to obtain roasted material and mercury-containing tail gas;

[0007] Performing water immersion on the roasted material to obtain water immersion residue;

[0008] Performing acid leaching on the water immersion residue to obtain acid leaching solution;

[0009] Mixing the acid leaching solution and oxalic acid solution, and performing precipitation reaction to obtain rare earth oxalate;

[0010] Performing oxidation roasting on the rare earth oxalate to obtain rare earth oxide.

[0011] Preferably, the waste fluorescent powder containing mercury further comprises a pretreatment before being mixed with the alkali and the reducing agent; the pretreatment comprises: screening the waste fluorescent powder containing mercury to obtain undersize; mixing the undersize and hydrochloric acid solution, and performing pre-leaching to remove red powder.

[0012] Preferably, the mass of the alkali is 20-200% of the mass of the waste fluorescent powder containing mercury.

[0013] Preferably, the mass of the reducing agent is 5-50% of the mass of the mercury-containing waste fluorescent powder.

[0014] Preferably, the reducing agent comprises one or more of lignite, biomass and urea.

[0015] Preferably, the temperature of the reducing alkali roasting is 500-1000 DEG C, and the holding time is 10-120 min.

[0016] Preferably, after obtaining the mercury-containing tail gas, the mercury-containing tail gas is condensed to obtain elemental mercury.

[0017] Preferably, the concentration of the oxalic acid solution is 40-80 g / L; and the volume ratio of the oxalic acid solution to the acid leaching solution is 1-6:10.

[0018] Preferably, the precipitation reaction is followed by aging; and the aging is performed at a pH value of 1.5-2.5.

[0019] Preferably, the oxidative roasting is microwave heating roasting, and the microwave power is 300-1000 W; and the heating time is 5-20 min.

[0020] The present application provides a method for simultaneously recovering rare earth and mercury from mercury-containing waste fluorescent powder, which comprises the following steps: mixing alkali and a reducing agent with the mercury-containing waste fluorescent powder, and performing reducing alkali roasting to convert the complex forms of blue powder and green powder in the fluorescent powder into simple and easily leachable oxides such as Tb2O3 and Ce2O3, and to convert the complex forms of mercury in the mercury-containing waste fluorescent powder into elemental mercury for removal; condensing the mercury-containing tail gas to recover the elemental mercury; quenching the roasting material with water after the reducing alkali roasting is completed, so that the material becomes more porous and fragile; and removing NaAlO2 and excess alkali through water leaching; obtaining an acid leaching solution rich in rare earth elements after acid leaching of the water leaching residue; adding oxalic acid to the acid leaching solution to precipitate the rare earth elements as rare earth oxalates; and performing oxidative roasting of the rare earth oxalates to obtain rare earth oxides.

[0021] The present application can realize the conversion and separation of complex mercury, the coupling regulation of the dissociation and valence state conversion process of rare earth fluorescent powder, and the strengthening of the reaction process. The present application can realize the deep removal of mercury, the efficient leaching of rare earth and the removal of impurities. The method provided by the present application is clean and efficient, has a short process flow, and has a high comprehensive recovery rate of resources. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application provides a process flow diagram for simultaneously recovering rare earth and mercury from mercury-containing waste fluorescent powder. DETAILED DESCRIPTION

[0023] The present application provides a method for simultaneously recovering rare earth and mercury from mercury-containing waste fluorescent powder, which comprises the following steps:

[0024] Mixing the mercury-containing waste fluorescent powder, alkali and reducing agent, carrying out reduction alkali fusion roasting to obtain roasted material and mercury-containing tail gas;

[0025] Carrying out water immersion on the roasted material to obtain water immersion residue;

[0026] Carrying out acid immersion on the water immersion residue to obtain acid immersion liquid;

[0027] Mixing the acid immersion liquid and oxalic acid solution, carrying out precipitation reaction to obtain rare earth oxalate;

[0028] Carrying out oxidation roasting on the rare earth oxalate to obtain rare earth oxide.

[0029] The mercury-containing waste fluorescent powder, alkali and reducing agent are mixed, and reduction alkali fusion roasting is carried out to obtain roasted material and mercury-containing tail gas.

[0030] In the present application, the mercury-containing waste fluorescent powder preferably further comprises a pretreatment before being mixed with alkali and reducing agent; the pretreatment preferably comprises: screening the mercury-containing waste fluorescent powder to obtain undersize; mixing the undersize and hydrochloric acid solution to carry out pre-leaching to remove red powder. In the present application, the particle size of the undersize is preferably 0.07-1 mm. The present application removes large-particle impurities such as silicon oxide by screening. In the present application, the concentration of the hydrochloric acid solution is preferably 1-5 mol / L, more preferably 4 mol / L; the liquid-solid ratio of the hydrochloric acid solution and undersize is preferably 1-5 mL: 1 g, more preferably 3 mL: 1 g. In the present application, the temperature of the pre-leaching is preferably 30-70℃, more preferably 60℃; the time of the pre-leaching is preferably 1-5 h, more preferably 4 h. The present application removes red powder by pre-leaching. In the present application, the red powder refers to yttrium oxide. In the present application, the mercury-containing waste fluorescent powder after removing red powder contains blue powder BMA and green powder CMAT.

[0031] In the present application, the mixing of the mercury-containing waste fluorescent powder, alkali and reducing agent is preferably mechanical ball milling mixing or manual stirring mixing, more preferably mechanical ball milling mixing. In the present application, the rotation speed of the mechanical ball milling mixing is preferably 200-600 r / min. In the present application, mechanical ball milling mixing can make the mixing of different components more uniform, and can especially make the specific surface area of the mercury-containing waste fluorescent powder larger and the crystal lattice have defects, which is more conducive to subsequent reduction alkali fusion roasting and leaching.

[0032] In the present application, the mass of the alkali is preferably 20-200% of the mass of the mercury-containing waste fluorescent powder, and more preferably 100%. In the present application, the alkali preferably includes one or more of sodium hydroxide, potassium hydroxide, sodium peroxide and sodium carbonate. In the present application, the mass of the reducing agent is preferably 5-50% of the mass of the mercury-containing waste fluorescent powder, and more preferably 10%. In the present application, the reducing agent preferably includes one or more of lignite, biomass and urea. In the present application, the biomass is preferably agricultural and forestry waste.

[0033] In the present application, the alkali can destroy the spinel structure of the mercury-containing waste fluorescent powder (mainly blue powder and green powder), so as to facilitate subsequent leaching. The reducing agent is added to convert high-valence rare earth oxides into low-valence oxides (Ce2O3, Tb2O3) that are easy to leach, thereby improving the leaching rate. In addition, the alkali and the reducing agent have a synergistic effect, which can convert compounds of mercury (such as mercury sulfide, mercury sulfate, mercury chloride, etc.) into mercury hydroxide through calcination, and finally decompose into elemental mercury for removal, thereby achieving deep mercury removal.

[0034] In the present application, the temperature of the reducing alkali smelting is preferably 500-1000°C, and more preferably 800°C; the holding time is preferably 10-120 min, and more preferably 60 min. In the present application, the atmosphere of the reducing alkali smelting preferably includes a nitrogen atmosphere, an argon atmosphere, a CO2 atmosphere, a CO atmosphere or a H2 atmosphere. In the present application, the gas flow rate for providing the atmosphere is preferably 5-30 mL / min, and more preferably 20 mL / min. In the present application, the reducing alkali smelting is preferably enhanced by microwave heating, and the power of the microwave is preferably 300-1000 W, and more preferably 500 W.

[0035] In the present application, after obtaining the mercury-containing tail gas, the mercury-containing tail gas is preferably condensed to obtain elemental mercury. In the present application, the method of condensation is preferably multi-stage tubular condenser condensation.

[0036] After obtaining the calcined material, the present application performs water leaching on the calcined material to obtain water leaching residue. The present application preferably quenches the calcined material while hot, and then performs water leaching. In the present application, the liquid-solid ratio of water to calcined material during water leaching is preferably 1-4 mL:1 g. In the present application, the water is preferably deionized water. In the present application, the temperature of the water leaching is preferably 20-65°C; the time of the water leaching is preferably 10-60 min. In the present application, the water leaching is preferably performed under ultrasonic conditions; the power of the ultrasonic wave is preferably 100-600 W. The present application uses ultrasonic wave to enhance the leaching and separation effect.

[0037] The present application preferably performs solid-liquid separation after the water leaching to obtain water leaching residue and water leaching liquid. The present application preferably repeats the water leaching of the obtained water leaching residue for 1-5 times, and more preferably 3 times.

[0038] After obtaining the water leaching residue, the water leaching residue is subjected to acid leaching to obtain an acid leaching solution. In the present application, the acid used in the acid leaching is a hydrochloric acid solution; the concentration of the hydrochloric acid solution is preferably 1-5 mol / L, more preferably 4 mol / L. In the present application, the liquid-solid ratio of the hydrochloric acid solution to the water leaching residue is preferably 3-10 mL:1 g, more preferably 4 mL:1 g. In the present application, the temperature of the acid leaching is preferably 30-90°C, more preferably 80°C; the time of the acid leaching is preferably 20-120 min, more preferably 1 h. In the present application, the acid leaching is preferably carried out under ultrasonic conditions; the power of the ultrasonic wave is preferably 100-600 W. The present application uses ultrasonic wave to strengthen the separation effect of leaching.

[0039] The present application preferably carries out solid-liquid separation after the acid leaching to obtain acid leaching residue and acid leaching solution.

[0040] After obtaining the acid leaching solution, the acid leaching solution and oxalic acid solution are mixed to carry out a precipitation reaction to obtain rare earth oxalate. In the present application, the concentration of the oxalic acid solution is preferably 40-80 g / L, more preferably 50 g / L; the volume ratio of the oxalic acid solution to the acid leaching solution is preferably 1-6:10, more preferably 1:2. In the present application, the temperature of the precipitation reaction is preferably 40-85°C, more preferably 80°C; the time of the precipitation reaction is preferably 10-60 min, more preferably 20 min.

[0041] In the present application, the precipitation reaction is preferably followed by aging; the aging is carried out at a pH value of 1.5-2.5, more preferably at a pH value of 2.0. In the present application, the reagent used to adjust the pH value of the aging is preferably ammonia water and hydrochloric acid solution; the concentration of the ammonia water is preferably 25 wt%; the concentration of the hydrochloric acid solution is preferably 1 mol / L. In the present application, the time of the aging is preferably 1-5 h, more preferably 2 h.

[0042] The present application preferably carries out solid-liquid separation after the aging to obtain rare earth oxalate.

[0043] After obtaining the rare earth oxalate, the rare earth oxalate is subjected to oxidative roasting to obtain rare earth oxide. In the present application, the oxidative roasting is preferably carried out by microwave heating roasting, and the microwave power is preferably 300-1000 W, more preferably 400-500 W; the heating time is preferably 5-20 min, more preferably 10 min. In the process of the oxidative roasting, the rare earth oxalate is gradually decomposed into basic carbonate and then into rare earth oxide as the temperature increases, and finally the rare earth oxide is obtained.

[0044] The present application proposes a short process method, which directly processes mercury-containing waste fluorescent powder by adopting a reducing alkali fusion method, efficiently decomposes the complex structure of rare earth fluorescent powder, and obtains low-valence rare earth oxides, which are convenient for low-acid leaching; meanwhile, through the joint action of alkali and reducing agent, complex forms of mercury are removed. As an optimization, microwave can be used to strengthen decomposition in the roasting process, and ultrasonic waves can be used to strengthen leaching separation in the leaching process. The method of the present application can simultaneously realize the extraction of rare earth and the recovery of mercury.

[0045] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0046] Embodiment 1

[0047] The method shown in Figure 1 is adopted to simultaneously recover rare earth and mercury from mercury-containing waste fluorescent powder, and the steps are as follows:

[0048] First step, sample pretreatment:

[0049] The mercury-containing waste fluorescent powder is sieved to obtain undersize material with a particle size of 0.1 mm; 100 g of the undersize material is pre-leached with a 4 mol / L hydrochloric acid solution, the leaching temperature is 60℃, the liquid-solid ratio is 3 mL:1 g, the leaching time is 4 h, and the red powder is removed.

[0050] Second step, reducing alkali fusion roasting:

[0051] The alkali and reducing agent are added to the residue after the red powder is removed to perform reducing alkali fusion roasting, and roasted material and mercury-containing tail gas are obtained; wherein the mass of the alkali is 100% of the weight of the residue, and the mass of the reducing agent is 10% of the weight of the residue; the alkali is sodium hydroxide, and the reducing agent is lignite; CO is introduced during the reducing alkali fusion roasting process, and the flow rate is 20 mL / min;

[0052] The temperature of the reducing alkali fusion roasting is 800℃, the holding time is 60 min, the roasting process adopts microwave heating, and the microwave power is 500 W;

[0053] The mercury-containing tail gas is condensed to obtain elemental mercury.

[0054] Third step, water leaching impurity removal:

[0055] The roasted material obtained in the second step is quenched while hot, deionized water is added according to a liquid-solid ratio of 4 mL:1 g, water leaching is performed at 65℃ for 10 min, after solid-liquid separation, water leaching residue and water leaching liquid are obtained, and water leaching is repeated for 3 times; ultrasonic waves are used to strengthen leaching separation during the water leaching process, and the ultrasonic wave power is 100 W.

[0056] Fourth step, acid leaching:

[0057] The water leaching residue obtained in the third step is added with hydrochloric acid solution (the concentration of the hydrochloric acid solution is 4 mol / L) according to a liquid-solid ratio of 4 mL:1 g, and is subjected to acid leaching at a temperature of 80 ℃ for 1 h. After solid-liquid separation, acid leaching residue and acid leaching solution are obtained. Ultrasonic wave is used to strengthen leaching and separation during the acid leaching process, and the ultrasonic wave power is 600 W.

[0058] Fifth step, oxalic acid precipitation:

[0059] According to a volume ratio of the acid leaching solution to the oxalic acid solution of 2:1, oxalic acid solution is added to the acid leaching solution obtained in the previous step, the concentration of the oxalic acid solution is 50 g / L, the temperature is 80 ℃, and the reaction is performed for 20 min to precipitate rare earths. After adjusting the pH value of the solution to 2.0, aging is performed for 2 h, and then solid-liquid separation is performed to obtain rare earth oxalate precipitate.

[0060] Sixth step, oxidative roasting:

[0061] The rare earth oxalate precipitate obtained in the previous step is subjected to microwave heating roasting, the microwave power is 400 W, and the heating time is 10 min to obtain rare earth oxide with a purity of 96%.

[0062] The concentration of rare earth elements in the acid leaching solution is detected, and the recovery rates of the rare earth elements are calculated as follows: Y 99%, Eu 97%, Tb 95%, Ce 98%, Gd 89%, and La 95%. The removal rate of mercury is 99.8%.

[0063] Comparative Example 1

[0064] The procedure is basically the same as that in Example 1, except that no reducing agent is added and the reaction atmosphere is not controlled to be a reducing atmosphere. The concentration of rare earth elements in the acid leaching solution is detected, and the recovery rates of the rare earth elements are calculated as follows: Y 98%, Eu 94%, Tb 90%, Ce 85%, Gd 80%, and La 40%. The removal rate of mercury is 94%.

[0065] Comparative Example 2

[0066] The simple distillation method (using a tube furnace to heat and passing nitrogen as a carrier gas) needs to be heated at 800 ℃ for 20 h to achieve the same mercury removal effect as that in Example 1.

[0067] The above only describes the preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for simultaneously recycling rare earth and mercury from mercury-containing waste fluorescent powder, comprising the following steps: mixing the mercury-containing waste fluorescent powder, alkali and reducing agent, and performing reduction alkali roasting to obtain roasted material and mercury-containing tail gas; the reducing agent comprises one or more of lignite, biomass and urea; performing water immersion on the roasted material to obtain water immersion residue; performing acid immersion on the water immersion residue to obtain acid immersion liquid; mixing the acid immersion liquid and oxalic acid solution, and performing precipitation reaction to obtain rare earth oxalate; performing oxidative roasting on the rare earth oxalate to obtain rare earth oxide; the alkali comprises one or more of sodium hydroxide, potassium hydroxide, sodium peroxide and sodium carbonate; the temperature of the reduction alkali roasting is 500-1000℃, and the holding time is 10-120 min.

2. The method of claim 1, wherein, Before the mercury-containing waste fluorescent powder is mixed with the alkali and the reducing agent, the method further comprises pretreatment; the pretreatment comprises: screening the mercury-containing waste fluorescent powder to obtain undersize; mixing the undersize and hydrochloric acid solution, and performing pre-leaching to remove red powder.

3. The method of claim 1, wherein, The mass of the alkali is 20-200% of the mass of the mercury-containing waste fluorescent powder.

4. The method of claim 1, wherein, The mass of the reducing agent is 5-50% of the mass of the mercury-containing waste fluorescent powder.

5. The method of claim 1, wherein, After the mercury-containing tail gas is obtained, the method further comprises condensing the mercury-containing tail gas to obtain elemental mercury.

6. The method of claim 1, wherein, The concentration of the oxalic acid solution is 40-80 g / L; the volume ratio of the oxalic acid solution to the acid immersion liquid is 1-6:

10.

7. The method of claim 1, wherein, The method further comprises aging after the precipitation reaction; the aging is performed under the condition that the pH value is 1.5-2.

5.

8. The method of claim 1, wherein, The oxidative roasting adopts microwave heating roasting, and the microwave power is 300-1000 W; the heating time is 5-20 min.

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