CN-121976043-A - Continuous process method for deeply removing lead from rare earth chloride solution

CN121976043ACN 121976043 ACN121976043 ACN 121976043ACN-121976043-A

Abstract

The invention relates to the technical field of waste liquid treatment, in particular to a continuous process method for deeply removing lead from a rare earth chloride solution. The method solves the problems of hydrogen sulfide dissipation, sulfide ion residue, discontinuous process and the like existing in the traditional sulfide precipitation method. The method comprises the steps of firstly adjusting the pH value of a solution to remove thorium, then enabling the solution to sequentially pass through a first fixed bed reaction column filled with surface activated porous reduced iron filler and a second collecting and polishing column filled with magnetic iron oxide collecting particles and titanium dioxide coating polishing particles under the anoxic condition to realize reduction precipitation and deep removal of lead, then removing radium through barium salt precipitation, and absorbing co-precipitated residual radioactive elements by cerium hydroxide wet glue. The process can realize whole-course continuous operation without introducing sulfide, and has the advantages of radioactive purification, high rare earth recovery rate and good process stability.

Inventors

YANG YANG
LIU WEI
HE LEI
GAO PING
Cao Shangjuan
ZHAO FEI
CHEN XING

Assignees

益阳鸿源稀土有限责任公司

Dates

Publication Date: 20260505
Application Date: 20260303

Claims (10)

1. The continuous process of deeply removing lead from chlorinated RE solution includes the following steps: (1) Regulating the pH value of the rare earth chloride solution and carrying out solid-liquid separation to remove thorium so as to obtain continuous lead-removing feed; (2) Providing a first fixed bed reaction column and a second trapping polishing column, wherein the first fixed bed reaction column is filled with surface activated porous reduced iron fixed bed filler, and the surface activated porous reduced iron fixed bed filler at least comprises reduced iron powder subjected to acid washing and weak oxidation surface activation treatment; (3) Under the anoxic control condition, the continuous lead removal feeding sequentially passes through the first fixed bed reaction column and the second trapping and polishing column in a constant temperature and constant flow mode, and solid-liquid separation is carried out on the liquid discharged from the second trapping and polishing column to obtain continuous lead removal filtrate; (4) Adding barium salt into the continuous lead-removing filtrate, mixing, adding sulfate to form barium sulfate precipitate, and performing solid-liquid separation to remove radium to obtain radium-removing liquid; (5) And adding the cerium hydroxide wet glue into the radium-removing liquid for adsorption/coprecipitation treatment and carrying out solid-liquid separation to obtain the rare earth chloride solution for deep removal of lead.
2. The continuous process method for deep lead removal by deep removal of rare earth chloride solution according to claim 1 is characterized in that ammonia water is used as a precipitant in the step (1), the mass fraction of the ammonia water is 25% -30%, the pH value of the rare earth chloride solution is adjusted to 4.8-5.2, the rare earth chloride solution is stirred for 15-30 min at 65-75 ℃, and solid-liquid separation is carried out after the ammonia water is kept stand for 20-40 min.
3. The continuous process method for deep lead removal by deep removal of rare earth chloride solution according to claim 1 is characterized in that in the step (2), the granularity of reduced iron powder is 80-120 meshes, the mass fraction of hydrogen chloride in the pickling solution is 2.8-3.2%, the mass ratio of the pickling solution to the reduced iron powder is 5.5:1-6.5:1, the pickling temperature is 48-52 ℃, the pickling stirring time is 7-9 min, the number of times of water washing after pickling is 2-4, the mass fraction of hydrogen peroxide in the weak oxidation surface activated activating solution is 0.8-1.0%, the mass ratio of the activating solution to the iron powder after pickling is 1.8:1-2.2:1, the soaking time is 0.8 min-1.2 min, and the number of times of water washing after activation is 1-3.
4. The continuous process method for deep lead removal by deep removal of rare earth chloride solution according to claim 1, wherein in the step (2), the surface activated porous reduced iron fixed bed filler is composite particles obtained by kneading and granulating surface activated porous reduced iron powder, an inorganic cementing component and bentonite, the inorganic cementing component is cerium hydroxide wet glue, and the particle size of the composite particles is 1-2 mm.
5. The continuous process method for deep lead removal by deep removal of rare earth chloride solution according to claim 4 is characterized in that the cerium hydroxide wet gel is 10% -13% of the surface activated porous reduced iron powder in mass, the bentonite is 3.5% -4.5% of the surface activated porous reduced iron powder in mass, the kneading water is 14% -18% of the surface activated porous reduced iron powder in mass, and the preparation of the cerium hydroxide wet gel comprises the steps of carrying out precipitation reaction on 8% -12% cerium chloride heptahydrate solution and 15% -20% sodium hydroxide solution in mass, wherein the precipitation reaction temperature is 20 ℃ -30 ℃, the stirring time is 5 min-15 min, and the cerium hydroxide wet gel is obtained through filtration.
6. The continuous process for deep removal of lead from a rare earth chloride solution according to claim 1, wherein in the step (2), the magnetic iron oxide trapping particles are ferroferric oxide trapping particles, and the second trapping polishing column is filled with the ferroferric oxide trapping particles first and then with the titanium dioxide coating polishing particles along the feeding direction.
7. The continuous process method for deep lead removal by deep removal of rare earth chloride solution according to claim 1, wherein the ferroferric oxide trapping particles are obtained by mixing and granulating ferroferric oxide powder and bentonite, the bentonite dosage is 8% -12% of the mass of the ferroferric oxide, the drying temperature is 110 ℃ -130 ℃ and the time is 1-3 h, the roasting temperature is 430 ℃ -470 ℃ and the time is 0.5-1.5 h, and roasting is performed in a nitrogen atmosphere.
8. The continuous process for deep lead removal by deep removal of rare earth chloride solution according to claim 1, wherein in the step (2), the average particle diameter of titanium dioxide in the titanium dioxide matrix particles is 0.1-0.3 μm, the hydrated titanium oxide nano coating is formed by acidic hydrolysis of titanium tetrachloride serving as a titanium source and impregnating of the titanium dioxide matrix particles, pH is adjusted to 2.8-3.2 in an aqueous phase by ammonia water and stirring, so that hydrated titanium oxide generated by hydrolysis is deposited on the surfaces of the titanium dioxide matrix particles, and the titanium tetrachloride amount is 30-35% of the mass of the titanium dioxide matrix particles.
9. The method for continuously removing lead from a rare earth chloride solution by deep stripping according to claim 1, wherein the oxygen deficiency control in the step (3) comprises deoxidation and gas sealing of a feed, wherein the feed tank is a heatable sealed container, deoxidized gas is nitrogen or argon, the feed temperature is 65-75 ℃, the nitrogen bubbling flow is 150-250 mL/min, the bubbling stripping time is 20-40 min, and a pipeline is kept sealed in the continuous conveying process, so that the liquid of the first fixed bed reaction column does not enter the second trapping polishing column.
10. The continuous process method for deep removal of lead from rare earth chloride solution according to claim 1, wherein in the step (3), a first fixed bed reaction column is filled with 550-650 g of the surface activated porous reduced iron fixed bed filler, a second trapping and polishing column is filled with 180-220 g of the magnetic iron oxide trapping particles and 180-220 g of the titanium dioxide coating polishing particles, the mass flow rate of continuous feeding is 40-60 g/min, and the pore diameter of a solid-liquid separation filter medium is 0.8-1.2 μm.

Description

Continuous process method for deeply removing lead from rare earth chloride solution Technical Field The invention relates to the technical field of waste liquid treatment, in particular to a continuous process method for deeply removing lead from a rare earth chloride solution. Background In the field of rare earth hydrometallurgy, the purification treatment of rare earth chloride solution is a key link, wherein the lead removal operation directly affects the purity and the radioactivity index of the final product. In the traditional industry, a sulfide precipitation method is widely adopted for removing lead, and the method relies on a sulfide reagent and lead ions to generate insoluble lead sulfide precipitate so as to realize separation. However, the limitation of the method is increasingly remarkable, firstly, hydrogen sulfide gas is easy to escape in the reaction process, so that the working environment is deteriorated, the poisoning and explosion risks exist, an exhaust gas treatment device is additionally arranged, and the operation and maintenance cost is increased. And secondly, residual sulfur ions are difficult to thoroughly remove, which can interfere with the subsequent solvent extraction process, so that organic phase emulsification or extractant poisoning is caused, and the rare earth separation efficiency is reduced. In addition, rare earth sulfide coprecipitation phenomenon is often accompanied in the lead sulfide precipitation process, and particularly, light rare earth elements are easier to form colloid precipitation, so that the loss of rare earth main components is caused, and the overall recovery rate is influenced. A further problem is the lack of process connectivity. Most of the existing sulfide precipitation methods are operated intermittently, continuous butt joint is difficult to realize with the processes of front-end pH adjustment thorium removal and rear-end radium removal, repeated transfer adjustment is needed, and therefore system flow and concentration fluctuation are frequent. This instability reduces the accuracy of lead content control, and product consistency is difficult to guarantee. Meanwhile, the frequent start and stop of the intermittent process aggravates equipment corrosion and impurity introduction risks, and is particularly remarkable in a high-temperature and high-acid environment. Another significant problem is the phenomenon of lead reversion, i.e. re-leaching of precipitated lead under oxidizing conditions, due to the local potential change caused by ferrous oxidation, which is lacking in the conventional methods. Along with the deepening of the application of rare earth materials in the high and new technical fields, the purity requirement on rare earth chloride solution is becoming severe, particularly the lead content needs to be reduced to be lower than milligram upgrading, and the existing sulfide system is difficult to realize deep removal due to the limitation of the chemical characteristics of the existing sulfide system. In addition, the demand for the synergistic removal of radioactive elements thorium and radium is increasingly outstanding, but the sulfide method cannot form synergy with the radioactive purification process, but rather the burden of radioactive waste residue treatment is aggravated by sulfur residues. Under the current technical background, development of a lead removal process which can realize whole-process continuous operation without introducing sulfide ions and also has radioactive purification becomes a bottleneck to be broken through in the rare earth industry. The improvement needs to fundamentally avoid secondary pollution, and simultaneously ensures the process stability and the rare earth recovery rate so as to meet the requirements of modern green production. Disclosure of Invention In view of the above, the invention aims to provide a continuous process method for deeply removing lead from a rare earth chloride solution, which aims to solve the problems of large environmental pollution, poor process continuity, unstable product purity and the like caused by the defects of hydrogen sulfide dissipation, interference extraction of sulfide ion residues, serious rare earth coprecipitation loss, unsmooth connection with a radioactive purification flow and the like in the lead removal process of the rare earth chloride solution in the conventional sulfide precipitation method. Based on the above purpose, the invention provides a continuous process method for deeply removing lead from rare earth chloride solution, which comprises the following steps: (1) Regulating the pH value of the rare earth chloride solution and carrying out solid-liquid separation to remove thorium so as to obtain continuous lead-removing feed; (2) Providing a first fixed bed reaction column and a second trapping polishing column, wherein the first fixed bed reaction column is filled with surface activated porous reduced iron fixed bed filler, and