CN112939132B - Method for recovering strontium and thorium in wastewater through aqueous two-phase step-by-step extraction - Google Patents
Method for recovering strontium and thorium in wastewater through aqueous two-phase step-by-step extraction Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
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- C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
- C22B60/02—Obtaining thorium, uranium, or other actinides
- C22B60/0291—Obtaining thorium, uranium, or other actinides obtaining thorium
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- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
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Abstract
The invention discloses a method for recovering strontium and thorium in wastewater by aqueous two-phase stepwise extraction, which comprises the following steps: under the condition of enough halogenated salt, strontium and halide ions are subjected to complexation to generate an anion association complex, under the action of a controlled pH value and a certain concentration of salting-out agent, the phase is separated from polyethylene glycol, strontium and polyethylene glycol are distributed to an upper layer, and thorium and the salting-out agent stay at a lower layer. The strontium-polyethylene glycol phase at the upper layer can be subjected to back extraction to obtain strontium by adjusting the pH value, the thorium-rich phase at the lower layer is continuously coupled by azochlorophosphine III under the controlled pH value, and is distributed to the upper layer with the polyethylene glycol under the action of a salting-out agent, the extracted thorium and the extracted polyethylene glycol are subjected to back extraction by adjusting the pH value to obtain recovered thorium, and the salting-out agent is arranged at the lower layer. The method has simple steps, the used reagent is non-toxic and harmless, the extraction amount of strontium and thorium is large, the efficiency is high, the method is hardly influenced by the equal organic matter or ion strength, and the extracted strontium or thorium can be recovered by back extraction of 100 percent of strontium or thorium by adjusting the pH value; the extractant can be recovered after extraction, and no secondary pollution is caused.
Description
Technical Field
The invention relates to the technical field of nuclide pollution control, in particular to a method for extracting and recovering strontium and thorium in wastewater by steps through aqueous two phases.
Background
From uraniumStrontium and thorium generated by mine mining smelting wastewater or a uranium-rich nuclear power plant are radioactive pollutants, and can spontaneously emit certain rays to harm human bodies and other organisms. Wherein strontium has 5 isotopes: strontium-84 ( 84 Sr), strontium-86 ( 86 Sr), strontium-87 ( 87 Sr), strontium-88 ( 88 Sr and strontium-90: (Sr) 90 Sr) in which 90 Sr is radioactive, is the product of radioactive decay of uranium-235, and is also one of the fission products of nuclear reactors. Its half-life is long (T1/2 ═ 28a), and it emits beta rays. Is often used as a beta-ray source. The nuclear industry, nuclear accidents often cause radioactive contamination of the environmental strontium. According to the Japanese media report, about 150 liters of radioactive substance-containing wastewater flows into the sea in the event of water leakage at the wastewater treatment facility of the first nuclear power plant in Fudao in 2011, wherein 90 The concentration of Sr is 300 ten thousand times the legal concentration standard. Due to its chemical nature and Ca 2+ Are relatively similar and therefore radioactive 90 Sr easily accumulates in the bones of the organism and thus produces long-term beta-ray irradiation to the organism. Due to long life, high solubility and biotoxicity, radioactivity 90 Sr can lead to cancer after entering human body. Thus comprising 90 The treatment and disposal of Sr wastewater is of particular concern. The nuclear industry often produces 90 Radioactive Sr waste water, nuclide before discharge 90 Effective removal of Sr is extremely important for environmental sustainable development and for ensuring human health. But in waste water 90 The removal of Sr is often interfered by other coexisting ions, and the effective selective removal is realized 90 Sr remains a difficult problem. The development of the strontium-containing wastewater purification technology and principle research is a hot spot of the current research and a problem to be solved urgently in practical engineering.
Thorium is another radioactive metal element, which can be bombarded by neutrons to obtain uranium-233, so that it is a potential nuclear fuel. Thorium is relatively active in chemical properties, insoluble in dilute acid and hydrofluoric acid, and soluble in fuming hydrochloric acid, sulfuric acid and aqua regia. The nitric acid passivates the thorium. Caustic has no effect on it. It can react with halogen, sulfur and nitrogen at high temperature. Natural thorium is all 232Th, and its half-life is about 1.4X 10 10 And (5) year. Thorium is an octostone element, the compound is mainly in 4 valence state and can be hydrolyzed into precipitate in aqueous solutionCan precipitate at a low pH, and can react with Fe (OH) 3 And Al (OH) 3 Precipitates form, which are chemically similar to zirconium, hafnium. Except inert gases, thorium can react with almost all nonmetallic elements to generate a binary compound; when heated, quickly oxidize and glow. Thorium is a highly toxic element. In the development and utilization of rare earth resources, radioactive thorium is redistributed in a water body. The main pollution source is waste water generated in rare earth processing enterprises and mineral exploitation. In addition, thorium can be brought into an environmental water body by the drip washing of rainwater on tailing and waste residue stacking places. In an inner Mongolia autonomous region of a rare earth resource development area in China, because the treatment of waste residues of rare earth resources and the development and utilization of resources are not carried out simultaneously, a large amount of thorium waste residues are generated, the soil pollution area reaches up to 7.33 square kilometers, the concentration is higher than the soil background value of China 294.6%, the baotou city thorium radiation reaches 1.87mSv to human bodies and is higher than 25% of the national average level, which is 6 times of the world level, and the method has great harm to the human bodies. After wind and rain, a large amount of thorium enters a water body, osteoporosis can be caused after polluted water is drunk for a long time, and the osteoporosis is serious because the artificial people who develop the thorium in the Baotou city drink enough water on construction sites and are radiated in the long term, and the whole body is fractured when the artificial people fall down.
The treatment measures for the strontium and thorium pollution in the water body can be mainly summarized into two main types: the first category is that strontium or thorium in a dissolved state in wastewater is converted into insoluble heavy metal compounds, and the insoluble heavy metal compounds are removed from the wastewater by a precipitation and floatation method, and specific methods include a neutralization method, a sulfuration method, a reduction method, an oxidation method, an ion exchange method, an ion floatation method, an electrolysis method and the like. And the second method is to concentrate and separate strontium or thorium in the sewage under the condition of not changing the chemical form of the strontium or thorium, and the specific methods include a reverse osmosis method, an electrodialysis method, an evaporation concentration method and the like. A novel technology exists in China, namely a novel technology which is low in cost, high in efficiency and good in selectivity, namely an emulsion liquid membrane technology is used for recovering strontium or thorium elements in a water body, the recovery rate is up to 90%, but the technology is not mature and can only be used for low-concentration strontium or thorium wastewater, and the treatment effect in the high-concentration strontium or thorium wastewater is extremely poor. In view of the above, there are still some difficulties in the treatment of high concentrations of strontium and thorium, and further research is still needed.
The extraction method mainly utilizes the difference of the solubility of solute in the solvents which are not mutually soluble, and uses one solvent to extract thorium from the waste water formed by the other solvent. Among the methods, the extraction method has obvious advantages, including simple process design and operation, low separation cost, good selective separation performance, no influence of organic matters or ionic strength, high separation speed, capability of recovering reagents and thorium, less secondary pollution and the like.
The double aqueous phase extraction system formed by the polyethylene glycol and the salt can obtain element separation with high yield and high purity under mild conditions. The technology is applied to separation and enrichment of persistent pollutants in environments such as Tl, Pu, U, Rb, Cs, Li, K, Sr and the like (CN111719046A, CN110656247A, CN104498739A, CN108330298A and CN 108031288A). The systems mostly adopt arsine azo and chlorophosphine azo color-developing agents, ion associations which are insoluble in water and soluble in organic solvents are generated by association of heavy metal complex anions and color-developing agent cations, and then the ion associations are extracted into a polyalcohol phase, and when a target element is separated, an extracting agent is recycled, so that the generation of secondary pollution is avoided, therefore, if the system is applied to separation and enrichment of strontium and thorium, the problem of radioactive wastewater containing strontium or thorium is effectively solved.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a method which is environment-friendly, convenient and low in cost and can effectively separate and recover strontium and thorium in wastewater. According to the invention, according to different complexing abilities of strontium ions or thorium ions and different complexing agents, a two-aqueous-phase system is respectively formed by adding polyethylene glycol/sodium citrate, and salt ions capture water molecules originally combined with organic polyethylene glycol to release polyethylene glycol molecules by utilizing the hydration action of salt, so that polyethylene glycol-aqueous two phases with clear interfaces are formed step by step. In the invention, sodium citrate is preferred to replace the traditional sulfate, carbonate or phosphate is taken as a salting-out substance, and the problem that strontium sulfate, strontium carbonate, strontium phosphate or thorium carbonate is difficult to recover due to precipitation is avoided. Sr in the invention 2+ And I-junctionTo form [ SrI ] 4 ] 2- The complex anion can directly generate an ionic association compound [ SrI ] with protonated polyethylene glycol 4 ] 2- ·2[PEG-OH 2 ] + And Th 4+ Is coupled with azo chlorophosphine III to form ionic associated compound Th 4+ -A 4- The association complex has stronger hydrophobicity and is respectively distributed to the upper layer with the polyethylene glycol. [ SrI ] distributed to the upper layer 4 ] 2- ·2[PEG-OH 2 ] + Or Th 4+ -A 4- And recovering strontium or thorium under a certain acidity, wherein the used polyethylene glycol and salting-out agent can be recovered. The method avoids using an organic solvent with higher toxicity, and has certain reference value for researching separation, enrichment, recovery and determination of the radionuclides strontium and thorium with long service life, high solubility and biotoxicity.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for extracting and recovering strontium and thorium in wastewater step by using double aqueous phases comprises the following steps:
(1) adding a coordination agent halogenated salt, a salting-out agent citrate and an extracting agent polyethylene glycol into the wastewater containing strontium and thorium, and uniformly mixing, wherein the molar concentration of the coordination agent halogenated salt in the mixed solution is 0.6-0.8 mol/L, and the mass fraction of the salting-out agent sodium citrate is 10-25%; the mass fraction of the extractant polyethylene glycol is 10 percent; adjusting the pH value of the mixed solution to 4-7, and carrying out phase separation to obtain an upper phase rich in strontium and polyethylene glycol and a lower phase containing thorium and a salting-out agent;
(2) taking the upper phase obtained in the step (1), adjusting the pH value to 1-4 to split the phases, wherein the upper phase is recyclable polyethylene glycol, and the lower phase is strontium obtained by back extraction;
(3) taking the lower phase obtained in the step (1), adding an azo chlorophosphine III coupling agent accounting for 0.0024-0.036% of the mass fraction of the lower phase and polyethylene glycol with the mass equal to that of the polyethylene glycol added in the step (1), uniformly mixing, adjusting the pH to 5-8 to separate the phases, wherein the upper phase is a thorium-azo chlorophosphine III-polyethylene glycol-containing mixture, and the lower phase is a salting-out agent;
(4) taking the upper phase obtained in the step (3), adjusting the pH value to 1-4 to split the phase, wherein the upper phase is a mixture of azochlorophosphine III coupling agent and polyethylene glycol; the lower layer is thorium obtained by back extraction.
Preferably, the concentration of strontium and the concentration of thorium in the wastewater are respectively within 10 mg/L.
Preferably, the organic matter coexisting in the wastewater comprises Humic Acid (HA), Citric Acid (CA) and oxalic acid (OX), and the coexisting homoion comprises Na + 、NH 4 + 、Mg 2+ 、Ca 2+ 。
Preferably, the complexing agent halogenated salt is one or a combination of sodium chloride, sodium bromide and sodium iodide.
Preferably, the salting-out agent citrate is one or a combination of sodium citrate, potassium citrate or ammonium citrate.
Preferably, the extractant polyethylene glycol is one or a combination of polyethylene glycol 400, polyethylene glycol 1000, polyethylene glycol 4000 and polyethylene glycol 6000.
Preferably, 0.5mol/L hydrochloric acid or sodium hydroxide solution is used for pH adjustment in step (1) and step (3).
Preferably, 2mol/L hydrochloric acid is used for pH adjustment in the step (2) and the step (4).
Preferably, the complexing agent is sodium iodide, and the molar concentration of the complexing agent in the mixed solution is 0.6 mol/L; the salting-out agent citrate accounts for 12% of the mixed solution by mass; the extractant is polyethylene glycol 6000; the mass fraction of the azo-chloro-phosphine III coupling agent is 0.03%.
Preferably, the polyethylene glycol in the steps (2) and (4) is concentrated and regenerated; and (4) recovering the salting-out agent in the step (3) through evaporation and crystallization.
The method can detect the concentration of strontium or thorium in different solutions by adopting a flame method atomic absorption spectrometry or an ultraviolet-visible spectrophotometer, and can calculate the extraction rate and the back extraction rate of strontium according to a formula. The extraction rate or the back extraction rate is calculated as formula E (%) ═ C 0 -C t )*100/C 0 Wherein, C 0 Initial concentration, mg/L; c t The lower layer concentration after extraction equilibrium, mg/L.
The specific reaction formula of the extraction and the back extraction is,
under a certain acidity, strontium in the water body is neutralized with I - Coordination occurs to form SrI 4 2- And, by PEG extraction:
the reaction of the extracted strontium for recovery through back extraction is as follows:
thorium in the water body is coupled with azoarsine III under certain acidity to generate Th 4+ -A 4- And extraction with polyethylene glycol:
under the action of certain acidity, extracted thorium (IV) enters the lower aqueous phase again for separation, and the extractant stays in the organic phase to realize regeneration.
Compared with the prior art, the invention has the following beneficial effects:
1. the one-time extraction rate is high and quick;
2. the method is suitable for extracting the mixed wastewater containing strontium and thorium with high concentration, and has large extraction amount of strontium or thorium;
3. the method for extracting strontium and thorium step by step is not influenced by organic matters or same ions with equal mass;
4. the extractant can be regenerated and used;
5. without secondary pollution.
Drawings
FIG. 1 is a flow chart of a method for recovering strontium and thorium in wastewater by aqueous two-phase step-by-step extraction;
FIG. 2 shows the measurement of Sr in the present invention by atomic absorption spectroscopy 2+ A schematic diagram of (a);
FIG. 3 shows the determination of Th by a spectrophotometer according to the present invention 4+ Schematic representation of (a).
Detailed Description
To better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples.
The invention discloses a method for recovering strontium and thorium in wastewater by aqueous two-phase step-by-step extraction, which is shown in a schematic process diagram in figure 1 and comprises the following steps:
(1) adding a coordination agent halogenated salt, a salting-out agent citrate and an extracting agent polyethylene glycol into the wastewater containing strontium and thorium, and uniformly mixing, wherein the molar concentration of the coordination agent halogenated salt in the mixed solution is 0.6-0.8 mol/L, and the mass fraction of the salting-out agent sodium citrate is 10-25%; the mass fraction of the extractant polyethylene glycol is 10 percent; adjusting the pH value of the mixed solution to 4-7, and carrying out phase separation to obtain an upper phase rich in strontium and polyethylene glycol and a lower phase containing thorium and a salting-out agent;
(2) taking the upper phase obtained in the step (1), adjusting the pH value to 1-4 to split the phase, wherein the upper phase is recyclable polyethylene glycol, and the lower phase is back-extracted strontium;
(3) taking the lower phase obtained in the step (1), adding an azo-chlorophosphine III coupling agent accounting for 0.0024-0.036% of the mass fraction of the lower phase and polyethylene glycol (new polyethylene glycol or polyethylene glycol recovered in the step (2)) with the same mass as the polyethylene glycol added in the step (1), uniformly mixing, adjusting the pH to 5-8 to separate phases, wherein the upper phase is a thorium-azo-chlorophosphine III-polyethylene glycol mixture, and the lower phase is a salting-out agent;
(4) taking the upper phase obtained in the step (3), adjusting the pH value to 1-4 to split the phase, wherein the upper phase is a mixture of azochlorophosphine III coupling agent and polyethylene glycol; the lower layer is thorium obtained by back extraction.
Example 1: establishment of two-aqueous phase system
Respectively taking 30mL of water into 4 centrifuge tubes, adding polyethylene glycol (polyethylene glycol 400, polyethylene glycol 1000, polyethylene glycol 4000 and polyethylene glycol 6000 are respectively added into the 4 centrifuge tubes), then adding citrate (the used citrate is one or a combination of sodium citrate, potassium citrate or ammonium citrate), uniformly mixing (the mass fraction of the polyethylene glycol in the mixed solution is 10%, and the mass fraction of the citrate is 10-25%), and inspecting the phase separation behavior. The results show that 10% by mass of polyethylene glycol 6000 phase separates most easily with 12% by mass of citrate.
Example 2
Based on example 1, the strontium and thorium containing smelting wastewater from a certain Guangdong Shaokou mining plant (the concentrations of strontium and thorium in the wastewater are respectively within 10mg/L, Humic Acid (HA), Citric Acid (CA) and oxalic acid (OX) are coexistent organic matters in the wastewater, and Na is coexistent homoion + 、NH 4 + 、Mg 2+ 、Ca 2+ The following examples all use this wastewater) extraction experiments:
respectively putting 30mL of wastewater into 3 centrifuge tubes (pH of the wastewater is 5-8), respectively adding polyethylene glycol 6000, citrate and halogenated salt (one or a combination of sodium chloride, sodium bromide and sodium iodide) into each centrifuge tube, uniformly mixing (the mass fraction of the polyethylene glycol in the mixed solution is 10%, the mass fraction of the citrate is 12%, and the molar concentration of the halogenated salt is 0.6-0.8 mol/L), and inspecting the influence of the halogenated salt serving as a complexing agent on strontium ion extraction. The result shows that 0.6-0.8 mol/L sodium iodide is most beneficial to extraction of strontium ions under the same addition amount, and 0.6mol/L sodium iodide is preferably used as a complexing agent.
Example 3
On the basis of example 2, an extraction experiment of strontium-and thorium-containing smelting wastewater of a certain mining plant of Guangdong Shaoguan:
respectively putting 30mL of wastewater into 3 centrifuge tubes, respectively adding polyethylene glycol 6000, citrate and sodium iodide into each centrifuge tube, uniformly mixing (the mass fraction of the polyethylene glycol in the mixed solution is 10%, the mass fraction of the citrate is 12%, and the molar concentration of the sodium iodide is 0.6mol/L), and inspecting the influence of acidity on strontium ion extraction. The results show that under the same conditions, extraction of strontium ions is favored most when the pH is 6-7, and extraction of thorium ions under the same conditions is negligible.
Example 4
On the basis of example 3, after extraction, the phases are separated, the strontium ions and the polyethylene glycol are in the upper phase, and the thorium and the salting-out agent are in the lower phase. And (3) carrying out strontium back extraction on the upper phase liquid, and investigating the influence of acidity on the strontium back extraction. As a result, it was found that the pH was controlled by adding 2mol/L dilute sulfuric acid, dilute nitric acid, and dilute hydrochloric acid, and that dilute nitric acid or dilute hydrochloric acid is preferable because strontium ions are precipitated by sulfate groups. At pH 2, strontium re-entering the lower phase is maximized and recovered by concentration, while polyethylene glycol remaining in the upper phase is also recovered.
Example 5
On the basis of example 4, thorium and a salting-out agent in the lower phase were subjected to aqueous two-phase extraction, and an azochlorophosphine III coupling agent and polyethylene glycol were added (the amount of polyethylene glycol added here was the same as that added in example 3, and new polyethylene glycol or polyethylene glycol recovered in example 4 was used) to examine the effect of the azoarsine III coupling agent on thorium ion extraction. The result shows that 0.03 percent of azoarsine III accounts for the mass fraction of the lower phase, which is beneficial to the extraction of thorium, and 0.03 percent of azoarsine III is preferably used as a coupling agent.
Example 6
In addition to example 5, thorium and a salting-out agent in the lower phase were subjected to aqueous two-phase extraction, and a chlorophosphine iii coupling agent (accounting for 0.03% by mass of the lower phase) and polyethylene glycol (the amount of polyethylene glycol added here was equal to the amount of polyethylene glycol added in example 3, and new polyethylene glycol or polyethylene glycol recovered in example 4 was used) were added to examine the effect of pH on the extraction of thorium ions. The result shows that the extraction of thorium is facilitated when the pH is 5-6, thorium ions, azoarsine III and polyethylene glycol are distributed to an upper phase, and a salting-out agent stays in a lower phase and can be recovered through concentration.
Example 7
On the basis of example 6, thorium in the upper phase was back-extracted, and the influence of acidity on the back-extracted thorium was examined. The results show that when the pH is regulated by adding 2mol/L dilute sulfuric acid, dilute nitric acid and dilute hydrochloric acid, the thorium which enters the lower water phase again is concentrated and recovered to the maximum extent when the pH is 1, and the polyethylene glycol which stays at the upper layer is also recovered.
Therefore, the extraction optimization result of the strontium-and thorium-containing smelting wastewater of a certain mining plant of Guangdong Shaoshaguan is as follows:
(1) taking 30mL of wastewater, putting the wastewater into a centrifuge tube (pH is 5-8), adding polyethylene glycol 6000, citrate and sodium iodide (the mass fraction of the polyethylene glycol in the mixed solution is 10%, the mass fraction of the citrate is 12%, and the molar concentration of the sodium iodide is 0.6mol/L), regulating the pH to be 6-7, shaking up, layering, and obtaining the extraction rate of 99% strontium in the upper layer without extracting thorium ions. (2) The back extraction conditions of the upper strontium layer are as follows: the pH value is regulated to 2 by using 2mol/L dilute nitric acid or dilute hydrochloric acid, strontium ions enter a lower layer water system to be recovered, and polyethylene glycol staying at an upper layer can also be recovered. (3) Adding arsine III (accounting for 0.03 percent of the mass fraction of the lower phase) and polyethylene glycol (the amount of the added polyethylene glycol is equal to that of the polyethylene glycol added in the step (1), and the polyethylene glycol can be used for new extraction or the polyethylene glycol recovered in the step (2)) into thorium-containing wastewater in the lower layer to perform two-phase extraction, distributing thorium-arsine III and polyethylene glycol in the upper layer, regulating the pH value to be 1 by using 2mol/L dilute sulfuric acid, dilute nitric acid or dilute hydrochloric acid, allowing thorium ions to enter a lower layer water system to be recovered, and recovering the polyethylene glycol staying in the upper layer.
Example 8: optimization of extraction equilibration time
(1) Taking 30mL of wastewater into a centrifuge tube (pH is 5-8), adding polyethylene glycol 6000, citrate and sodium iodide (the mass fraction of polyethylene glycol in the mixed solution is 10%, the mass fraction of citrate is 12% and the molar concentration of sodium iodide is 0.6mol/L), regulating and controlling the pH to be 6-7, shaking up, examining the layering time (5min, 10min, 15min, 20min and 25min), finding that the layering is not obvious before 10min, obtaining clear double water phases at 15min, obtaining the extraction rate of 99% strontium in the upper layer and not extracting thorium ions. (2) The back extraction condition of the upper strontium layer is that 2mol/L dilute nitric acid or dilute hydrochloric acid is used for regulating and controlling the pH value to be 2, strontium ions enter the lower water system for recovery, the layering time (5-25min) is considered similarly, 15min clear phase separation is obtained, and the polyethylene glycol staying on the upper layer is recovered. (3) Similarly, adding arsine III (accounting for 0.03 percent of the mass fraction of the lower phase) and polyethylene glycol (the amount of the added polyethylene glycol is equal to that of the polyethylene glycol added in the step (1), and new polyethylene glycol can be used, or the polyethylene glycol recovered in the step (2)) into thorium-arsine III and polyethylene glycol in the lower layer to perform aqueous two-phase extraction, distributing thorium-arsine III and polyethylene glycol in the upper layer after 15min, regulating the pH value of the upper layer to be 1 by using 2mol/L dilute sulfuric acid, dilute nitric acid or dilute hydrochloric acid, allowing thorium ions to enter a lower-layer water system after 15min to be recovered, and recovering the polyethylene glycol staying in the upper layer.
Example 9
(1) Taking 30mL of wastewater in a centrifuge tube (pH is 5-8), wherein the interfering ions contain 10mg/L of Na + 、NH 4 + 、Mg 2+ 、Ca 2+ (the influence of interfering ions is shown in table 1), adding polyethylene glycol 6000, citrate and sodium iodide (the mass fraction of polyethylene glycol in the mixed solution is 10%, the mass fraction of citrate is 12% and the molar concentration of sodium iodide is 0.6mol/L), adjusting the pH to 6-7, shaking up, layering for 15min, and still obtaining the extraction rate of 97% strontium in the upper layer without extracting thorium ions. (2) The back extraction conditions of the upper strontium layer are as follows: the pH value is regulated to 2 by using 2mol/L dilute nitric acid or dilute hydrochloric acid, strontium ions enter a lower layer water system to be recovered, and polyethylene glycol staying at an upper layer can also be recovered. (3) Adding arsine III (accounting for 0.03 percent of the mass fraction of the lower phase) and polyethylene glycol (the amount of the added polyethylene glycol is equal to that of the polyethylene glycol added in the step (1), and new polyethylene glycol or the polyethylene glycol recovered in the step (2)) into thorium-arsine III and polyethylene glycol in the lower layer to perform aqueous two-phase extraction, distributing thorium-arsine III and polyethylene glycol in the upper layer after 15min, still obtaining 96 percent extraction rate, then regulating the pH value to be 1 by using 2mol/L dilute sulfuric acid, dilute nitric acid or dilute hydrochloric acid, enabling thorium ions to enter a lower layer water system to be recovered, and recovering the polyethylene glycol staying in the upper layer.
TABLE 1 Effect of interfering ions
Table 1 shows sodium citrate-I - Arsenazo III-polyethylene glycolThe alcohol system being able to convert Sr 2+ Or Th 4+ With Na + ，NH 4 + ，Mg 2+ ，Ca 2+ Good separation is obtained.
Example 10
Taking 30mL of wastewater into a centrifuge tube (pH is 5-8), adding Humus (HA) which interferes with organic matters by 10mg/L, diethyltriaminepentaacetic acid (DTPA), Citric Acid (CA), oxalic acid (OX) and Ethylene Diamine Tetraacetic Acid (EDTA) (the influence of the organic matters is shown in table 2), adding polyethylene glycol 6000, citrate and sodium iodide (the mass fraction of the polyethylene glycol in a mixed solution is 10%, the mass fraction of the citrate is 12% and the molar concentration of the sodium iodide is 0.6mol/L), regulating and controlling the pH to be 6-7, shaking up, layering for 15min, obtaining the extraction rate of 86% strontium in the upper layer, and not extracting thorium ions. (2) The back extraction conditions of the upper strontium layer are as follows: the pH value is regulated to 2 by using 2mol/L dilute nitric acid or dilute hydrochloric acid, strontium ions enter a lower layer water system to be recovered, and polyethylene glycol staying at an upper layer can also be recovered. (3) Adding arsine III (accounting for 0.03 percent of the mass fraction of the lower phase) and polyethylene glycol (the amount of the added polyethylene glycol is equal to that of the polyethylene glycol added in the step (1), and new polyethylene glycol or the polyethylene glycol recovered in the step (2)) into thorium-arsine III and polyethylene glycol in the lower layer to perform aqueous two-phase extraction, distributing thorium-arsine III and polyethylene glycol in the upper layer after 15min, still obtaining an extraction rate of 87 percent, then regulating the pH value to be 1 by using 2mol/L dilute sulfuric acid, dilute nitric acid or dilute hydrochloric acid, enabling thorium ions to enter a lower-layer water system to be recovered, and recovering the polyethylene glycol staying in the upper layer.
TABLE 2 Effect of organic matter
Table 2 shows sodium citrate-I - The azo arsine III-polyethylene glycol system can make Sr 2+ /Th 4+ Can be well separated from Humus (HA), diethyltriaminepentaacetic acid (DTPA), Citric Acid (CA), oxalic acid (OX) and ethylenediaminetetraacetic acid (EDTA).
The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles and embodiments of the present invention are explained herein by using specific examples, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention; meanwhile, for a person skilled in the art, according to the embodiments of the present invention, there may be variations in the specific implementation manners and application ranges, and in summary, the content of the present description should not be construed as a limitation to the present invention.
Claims (10)
1. A method for extracting and recovering strontium and thorium in wastewater step by using double aqueous phases is characterized by comprising the following steps:
(1) adding a coordination agent halogenated salt, a salting-out agent citrate and an extracting agent polyethylene glycol into the wastewater containing strontium and thorium, and uniformly mixing, wherein the molar concentration of the coordination agent halogenated salt in the mixed solution is 0.6-0.8 mol/L, and the mass fraction of the salting-out agent sodium citrate is 10-25%; the mass fraction of the extractant polyethylene glycol is 10 percent; adjusting the pH value of the mixed solution to 4-7, and carrying out phase separation to obtain an upper phase rich in strontium and polyethylene glycol and a lower phase containing thorium and a salting-out agent;
(2) taking the upper phase obtained in the step (1), adjusting the pH value to 1-4 to split the phase, wherein the upper phase is recyclable polyethylene glycol, and the lower phase is back-extracted strontium;
(3) taking the lower phase obtained in the step (1), adding an azo chlorophosphine III coupling agent accounting for 0.0024-0.036% of the mass fraction of the lower phase and polyethylene glycol with the mass equal to that of the polyethylene glycol added in the step (1), uniformly mixing, adjusting the pH to 5-8 to separate the phases, wherein the upper phase is a thorium-azo chlorophosphine III-polyethylene glycol-containing mixture, and the lower phase is a salting-out agent;
(4) taking the upper phase obtained in the step (3), adjusting the pH value to 1-4 to split the phase, wherein the upper phase is a mixture of azochlorophosphine III coupling agent and polyethylene glycol; the lower layer is thorium obtained by back extraction.
2. The method for recycling strontium and thorium in wastewater through aqueous two-phase fractional extraction according to claim 1, wherein the concentrations of strontium and thorium in the wastewater are respectively within 10 mg/L.
3. The method for recovering strontium and thorium in wastewater by aqueous two-phase fractional extraction according to claim 1, wherein the organic matters coexisting in the wastewater comprise Humic Acid (HA), Citric Acid (CA) and oxalic acid (OX), and the coexisting same ions comprise Na + 、NH 4 + 、Mg 2+ 、Ca 2+ 。
4. The method for recovering strontium and thorium in wastewater by aqueous two-phase fractional extraction as claimed in claim 1, wherein the complexing agent halogenated salt is one or a combination of sodium chloride, sodium bromide and sodium iodide.
5. The method for recovering strontium and thorium in wastewater by aqueous two-phase fractional extraction as claimed in claim 1, wherein the salting-out agent citrate is one or a combination of sodium citrate, potassium citrate or ammonium citrate.
6. The method for extracting and recovering strontium and thorium in wastewater by aqueous two-phase step-by-step according to claim 1, wherein the extractant polyethylene glycol is one or a combination of polyethylene glycol 400, polyethylene glycol 1000, polyethylene glycol 4000 and polyethylene glycol 6000.
7. The method for recovering strontium and thorium in wastewater by aqueous two-phase fractional extraction according to claim 1, wherein 0.5mol/L hydrochloric acid or sodium hydroxide solution is used for pH adjustment in the steps (1) and (3).
8. The method for recovering strontium and thorium in wastewater by aqueous two-phase fractional extraction according to claim 1, wherein 2mol/L hydrochloric acid is used for pH adjustment in the steps (2) and (4).
9. The method for recovering strontium and thorium in wastewater through aqueous two-phase fractional extraction according to claim 1, wherein the complexing agent is sodium iodide, and the molar concentration of the sodium iodide in the mixed solution is 0.6 mol/L; the salting-out agent citrate accounts for 12% of the mixed solution by mass; the extractant is polyethylene glycol 6000; the mass fraction of the azo-chloro-phosphine III coupling agent is 0.03%.
10. The method for recovering strontium and thorium in wastewater by aqueous two-phase fractional extraction according to claim 1, wherein the polyethylene glycol in the steps (2) and (4) is concentrated and regenerated; and (4) recovering the salting-out agent in the step (3) through evaporation and crystallization.
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| US5948263A (en) * | 1997-06-11 | 1999-09-07 | The United States Of America As Represented By The United States Department Of Energy | Method for separating water soluble organics from a process stream by aqueous biphasic extraction |
| CN101529528A (en) * | 2006-10-23 | 2009-09-09 | 法国原子能委员会 | Grouped separation of actinides from a highly acidic aqueous composition a solvating extractant in a salting medium |
| JP2014034718A (en) * | 2012-08-09 | 2014-02-24 | Sumitomo Heavy Ind Ltd | Recovery method of rare-earth element |
| CN106048266A (en) * | 2016-07-18 | 2016-10-26 | 北京大学 | Method for separating and concentrating trace amounts of uranium from large amounts of thorium |
| CN109628759A (en) * | 2019-01-14 | 2019-04-16 | 兰州大学 | A method of extraction strontium |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5948263A (en) * | 1997-06-11 | 1999-09-07 | The United States Of America As Represented By The United States Department Of Energy | Method for separating water soluble organics from a process stream by aqueous biphasic extraction |
| CN101529528A (en) * | 2006-10-23 | 2009-09-09 | 法国原子能委员会 | Grouped separation of actinides from a highly acidic aqueous composition a solvating extractant in a salting medium |
| JP2014034718A (en) * | 2012-08-09 | 2014-02-24 | Sumitomo Heavy Ind Ltd | Recovery method of rare-earth element |
| CN106048266A (en) * | 2016-07-18 | 2016-10-26 | 北京大学 | Method for separating and concentrating trace amounts of uranium from large amounts of thorium |
| CN109628759A (en) * | 2019-01-14 | 2019-04-16 | 兰州大学 | A method of extraction strontium |
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