CN102773067B - Preparation method of selective adsorbent for magnetic cesium - Google Patents

Abstract

The invention belongs to an adsorbent preparation technology of radioactive liquid waste treatment process and in particular relates to a preparation method of a selective adsorbent for magnetic cesium. The preparation method comprises the following steps of: firstly, adding deionized water into a mixture of Ni powder and K4Fe(CN)6.3H2O to completely dissolve the K4Fe(CN)6.3H2O; then dropwise adding HCl solution into the obtained solute which is placed in thermostatic waterbath, and continuously stirring the mixture for reacting for a period of time; stilling the obtained reactant for aging for a period of time at a room temperature until a crystal structure grows completely; then washing generated sediment by deionized water until the washing liquid is colorless and transparent and the pH value is basically unchanged; and finally, drying the washed sediment at a constant temperature to constant weight to obtain the ferrous potassium nickel cyanide-nickel adsorbent. The preparation method provided by the invention has less steps and a simple process and facilitates industrial production. A better volume reduction ratio and decontamination factor can be achieved when the selective adsorbent is used for processing cesium-contained waste liquid.

Description

A kind of preparation method of magnetic caesium selective absorbent

Technical field

The invention belongs to the absorbent preparation technology in Spent Radioactive liquor treating process, be specifically related to a kind of preparation method of magnetic caesium selective absorbent.

Background technology

Along with greatly developing of China's nuclear power, will produce a large amount of low, intermediate level liquid waste.Except nuclear power operation waste liquid, in the fields such as retired decontamination, Isotope production, Application of Nuclear Technology and the scientific research of the various nuclear facilities of China, also can produce a large amount of low, intermediate level liquid waste.This wide, of a great variety, complicated component in class waste liquid source.

¹³⁷cs is as one of most important fission product nucleic, and because it has the longer half-life, branching ratio is high, and the gamma-rays (661.67keV) that energy is moderate, is widely used as various radioactive sources etc.Therefore, ¹³⁷cs is extensively present in spentnuclear fuel post processing waste liquid, nuclear power operation waste liquid, the retired waste liquid of nuclear facilities decontamination and laboratory waste liquid. ¹³⁷the top of Cs in fission product Mass Distribution curve, fission yield high (6.14%), the half-life is grown (30a).So, low, in there is higher ratio in putting waste water. ¹³⁷cs is hard γ radiation, and its energy is 661.67keV; Its 6th cycle I A family in the periodic table of elements, is easy to lose electronics, forms stable monovalent cation, is all monovalence in nearly all system, therefore, is easy to entered environment. ¹³⁷cs is medium radiotoxicity nucleic, once entered environment is large to the mankind's harm.

In order to ensure human health, Environmental security, reduction refuse volume and disposal costs, must be to containing ¹³⁷the low radioactive waste liquid of Cs is dealt carefully with.At present, mainly contain evaporation, precipitation-filtration method, ion-exchange etc. about the processing method of caesium.Ion-exchange is divided into again two kinds, inorganic ions exchange and ion exchange resin.During evaporation is processed, low level waste water is very traditional treatment process.This PROCESS FOR TREATMENT ability is large, can obtain higher decontamination factor, is generally 10 ³～10 ⁶, and have larger volume reduction ratio.External a lot of nuclear power station all adopts this processing method at present, and the most of nuclear power station of China also adopts in this method processing, low level waste water.Such as Qinshan nuclear power plant is processed land drainage, process drain by evaporation, decontamination factor is 10 ³～10 ⁴.The Qinshan second phase adopts the draining of evaporation process chemistry, and treating capacity is 3.5t/h, and decontamination factor is 10 ³.But the shortcoming of evaporation is also very obvious, mainly comprises: thermal energy consumption is large, investment and operating cost are higher; System complex, operation and maintenance requirement are high; Also there is the potential threats such as corrosion and scaling.

The precipitation method are the methods that separate for radioactivity the earliest.As far back as 1987, Schultz and Bray adopted the precipitation method to extract from the post processing waste liquid of the PUREX of Hanford factory flow process ¹³⁷cs.But the precipitation method can only be used for processing a large amount of caesiums, when pH is higher, in solution, hour, its clean effect is very poor for the amount of caesium, needs and other treatment technologies combinations carry out that the degree of depth separates and processing.Meanwhile, the method can produce a large amount of radioactivity mud, need to deal carefully with and dispose.

Ion-exchange process radioactive liquid waste have easy to operate, equipment is few, fixed investment is few, operating cost is low, can realize online and remote-controlled operation, is convenient to the advantages such as radiation protection.At present, pressurized-water reactor nuclear power plant radioactive liquid waste ion-exchange treatment is mainly used in: the aspects such as the purification of a circuit cools agent, the processing of fuel storage pool water, the processing of evaporimeter sewer, Spent Radioactive water treatment and boric acid purifying are multiplexing.Also process the precision processing of efflux afterwards as radioactive wastewater evaporation process and film simultaneously.Such as having described the Spent Radioactive water treatment process of U.S.'s boiling-water reactor and pressurized-water reactor nuclear power plant in American National Standard " light water reactor power plant Spent Radioactive water treatment system " ANSI/ANS-55.6-1993, wherein all contain ion-exchange treatment process.U.S. generation Ⅲ nuclear power unit AP1000 has adopted taking ion-exchange as main radioactive liquid handling process.In AP1000 Spent Radioactive water treatment system ion-exchange treatment flow process, be provided with deep-bed filter equipment.Deep-bed filter and ion exchange bed unit affinity, but slightly larger than ion exchange bed.Deep-bed filter is equipped with active carbon, zeolite etc., is mainly used in removing the radionuclide such as a small amount of organic matter and caesium that enters Spent Radioactive water treatment system.The granular ion exchange resin of the many employings of general ion-exchange bed fillers, but ion exchange resin has the poor shortcoming of irradiation stability, Comparatively speaking inorganic ion exchanger has selective height, irradiation stability and Heat stability is good, mechanical performance is high, the advantages such as useless exchanger after treatment can directly solidify, but, inorganic ion exchanger exists facile hydrolysis and the problem such as water-soluble also, need to solve.

Summary of the invention

The object of the invention is for containing ¹³⁷the processing problem of Cs radioactive liquid waste, provides a kind of preparation method of magnetic caesium selective absorbent, obtains a kind of not facile hydrolysis, to the selective high adsorbent of caesium.

Technical scheme of the present invention is as follows: a kind of preparation method of magnetic caesium selective absorbent, comprises the steps:

(1) to Ni powder and K ₄fe (CN) ₆3H ₂in the mixture of O, add deionized water, make K ₄fe (CN) ₆3H ₂o dissolves completely;

(2) gained dissolved matter is placed under water bath with thermostatic control, dropwise adds wherein HCl solution, and continuous stirring reaction a period of time;

(3), by gained reactant at room temperature static ageing a period of time, treat that crystalline structure growth is complete;

(4) precipitation generating with deionized water washing, until cleaning solution is water white transparency, and pH value substantially constant till;

(5) being deposited under constant temperature after washing is dried to constant weight, obtains ferrocyanide nickel potassium-nickel adsorbent.

Further, the preparation method of magnetic caesium selective absorbent as above, Ni powder and the K described in step (1) ₄fe (CN) ₆3H ₂the mass ratio of O is 1:5～1:10, and preferred value is 1:7; The amount of deionized water adding is K ₄fe (CN) ₆3H ₂20～30 times of the quality of O, preferred value is 26 times.

Further, the preparation method of magnetic caesium selective absorbent as above, the temperature of the water bath with thermostatic control described in step (2) is 95 ± 5 DEG C;

The HCl solution concentration adding in step (2) is 1.0～3.0mol/L, and preferred value is 2.4mol/L; The HCl adding is with the amount of Ni than being 2:1～4:1, and preferred value is 3:1;

In step (2), mixing speed is 600～850 revs/min, and preferred value is 750 revs/min; Reaction time is 20～40min.

Further, the preparation method of magnetic caesium selective absorbent as above, in step (3), the time of static ageing is 20～40min.

Further, the preparation method of magnetic caesium selective absorbent as above, in step (5), the temperature of freeze-day with constant temperature is 90～110 DEG C, be 10-24h drying time.

Beneficial effect of the present invention is as follows: the present invention adopts the method for the aqueous solution at the synthetic KNiFC/Ni adsorbent of combining closely by chemical bond with matrix Ni of metal Ni powder surface in situ, has following features:

1) this adsorbent is not hydrolyzed, and Cs is had very high selective.To the K of Cs _dvalue can reach 10 ⁵ml/g, and pH, Na ⁺concentration Sr ²⁺the metal ions such as concentration are all very little on its impact, work as Na ⁺when concentration is 0.1mol/L, its K _dvalue is still greater than 10 ⁴ml/g.

2) adsorption dynamics adsorption kinetics of this adsorbent is fine, and about 5minKd value is just greater than 10 ³ml/g, the about 1h of time of equilibrium adsorption.

3) this adsorbent has good radiation-resistant property.After granulation, containing the polyvinyl alcohol of the 5wt% that has an appointment, be still 25mGy/h in close rate, accumulated dose is less than in the scope of 10Gy, and Kd value does not change substantially.

4) NH ₄ ⁺the K of concentration to its absorption Cs _dvalue has larger impact, along with [NH ₄ ⁺] increase K _dvalue reduces rapidly after first increasing.As [NH ₄ ⁺when]=1.0mol/L, K _dvalue than maximum low approximately 2 magnitudes.

Preparation method's step provided by the present invention is few, and technique is simple, is convenient to suitability for industrialized production, contains caesium waste liquid can reach good volume reduction ratio and decontamination factor by this sorbent treatment.

Brief description of the drawings

Fig. 1 is preparation method's flow chart of the present invention;

Fig. 2 is Method And Principle schematic diagram of the present invention;

Fig. 3 is the chemical structural drawing of KNiFC/Ni.

Detailed description of the invention

Below in conjunction with drawings and Examples, the present invention is described in detail.

As shown in Figure 1, the preparation method of magnetic caesium selective absorbent provided by the present invention, comprises the steps:

(1) to Ni powder and K ₄fe (CN) ₆3H ₂in the mixture of O, add deionized water, make K ₄fe (CN) ₆3H ₂o dissolves completely; Ni powder and K ₄fe (CN) ₆3H ₂the mass ratio of O is 1:5～1:10, and preferred value is 1:7; The amount of deionized water adding is K ₄fe (CN) ₆3H ₂20～30 times of the quality of O, preferred value is 26 times;

(2) gained dissolved matter is placed under 95 ± 5 DEG C of waters bath with thermostatic control, dropwise adds wherein HCl solution, and continuous stirring reaction 20-40min; The HCl solution concentration adding is 1.0～3.0mol/L, and preferred value is 2.4mol/L; The HCl adding is with the amount of Ni than being 2:1～4:1, and preferred value is 3:1; Mixing speed is 600～850 revs/min, and preferred value is 750 revs/min;

(3) by room temperature static ageing 20～40min of gained reactant, treat that crystalline structure growth is complete;

(4) precipitation generating with deionized water washing, until cleaning solution is water white transparency, and pH value substantially constant till;

(5) the dry 10-24h at 90～110 DEG C that is deposited in after washing, to constant weight, is obtained to ferrocyanide nickel potassium-nickel adsorbent (representing with KNiFC/Ni).

The ionic reaction formula that the building-up process of said method relates to has:

Main reaction

${\mathrm{xNi}}_{\left(s\right)}+{2\mathrm{xH}}^{+}+\mathrm{Fe}{\left(\mathrm{CN}\right)}_6^{4-}+(4-2x)K^{+}\→K_{4-2x}{\mathrm{Ni}}_x\mathrm{Fe}{\left(\mathrm{CN}\right)}_{6\left(s\right)}+x{H}_{2\left(g\right)}---\left(1.1\right)$

Side reaction

Ni _(s)+2H ⁺→Ni _(l) ²⁺+H _2(g) (1.2)

${{\mathrm{xNi}}_{\left(l\right)}}^{2+}\mathrm{Fe}{\left(\mathrm{CN}\right)}_6^{4-}(4-2x)K^{+}\→K_{4-2x}{\mathrm{Ni}}_x\mathrm{Fe}{\left(\mathrm{CN}\right)}_{6\left(s\right)}---\left(1.3\right)$

This building-up process relates to a surface reaction, and the whole reaction mechanism mechanism of reaction is oxidation-diffusion-complexing.First, hydrochloric acid and Ni powder Surface Contact, destroy nickel metallic bond in the reaction of Ni powder body surface, forms nickel ion (non-free ion).Then, the Fe in solution (CN) ₆ ^4-and K ⁺arrive Ni powder surface from solution body through diffusion layer, with the quick complexing of nickel ion also not departing from completely, form ferrocyanide nickel potassium K on Ni powder surface _4-2xni _x[Fe (CN) ₆] (x=1-2) absorption core.The reaction of formula (1.2) and (1.3) also can occur in solution simultaneously, and nickel powder can the free Ni of oxidized formation ²⁺ion, enters solution, and forms precipitation of ferrocyanide at solution body.In order trying one's best at the synthesizing ferrous nickel potassium cyanide of nickel powder surface in situ, instead of to form precipitation in solution body, rationally to control reaction condition, make H ⁺the reaction of ion and nickel powder can not be too fast.Otherwise, Fe (CN) ₆ ^4-and K ⁺also do not diffuse to its surface, nickel has departed from matrix completely and has formed Ni freely ²⁺ion so, just can form a large amount of precipitations, and not form the compact adsorbent with Ni in solution.As shown in Figure 2, the chemical constitution of KNiFC/Ni as shown in Figure 3 for the principle that said method obtains ferrocyanide nickel potassium-nickel adsorbent (representing with KNiFC/Ni).

Distribution coefficient K _dthat a measurement KNiFC/Ni adsorbent is optionally measured Cs, K _dcomputing formula as follows:

$K_d=\frac{C_0-C_t}{C_t}\×\frac{V}{m}$

Wherein: C ₀-- ¹³⁷the initial specific activity of Cs, cpm/mL;

After Ct--adsorption equilibrium, ¹³⁷the specific activity of Cs, cpm/mL;

The volume of V--adsorbent solution, mL;

The quality of m--adsorbent, g.

Evidence, mixing speed is to K _dhave a great impact.This is because this synthetic reaction is surface reaction, stirs the path and the process that have changed effects of ion diffusion.Mixing speed increases, and thickness of diffusion layer reduces, and the diffusion velocity of nucleation ion increases, and therefore, surface forms KNiFC/Ni and increases K _dincrease.On the other hand, stir material surface is had to certain flushing action, when after the thickness of diffusion layer value of reaching capacity, flushing action is remarkable; Along with the increase of mixing speed, surface crystallization nucleation probability and Speed Reduction; Meanwhile, due to H ₃ ⁺o and K ⁺, Fe (CN) ₆ ^4-ion itself electrically, the difference of electric charge and ionic size, stir the degree difference extending influence, therefore reaction process is had a great impact K _dvalue changes can be very large.K ⁺, Fe (CN) ₆ ^4-ion be nucleation ion, the size of its concentration directly affects product composition, its Kd value of different products has very large difference, when mixing speed is 750rpm, ferrocyanide potassium concn has formed high K while being 0.09mol/L _dvalue (4.0 × 10 ⁴mL/g) product.

The reaction time major effect extent of reaction, with reaction time increase, the KNiFC/Ni obtaining is more, K _dbe worth just larger.But this reaction is DIFFUSION CONTROLLED, and chemical reaction velocity is very fast, therefore, reaction Once you begin approaches balance, K very soon _dvalue slowly increases.Be reacted to a certain degree, the reaction core on Ni powder surface is fewer and feweri, constantly rinses but stir effects on surface, and KNiFC starts to reduce.Therefore, with reaction time increase, K _dvalue first increases and then decreases.In the time of 20min and 40min, Kd value is respectively 7.5 × 10 ⁴with 1.0 × 10 ⁵mL/g, therefore, the reaction time is that 20～40min is comparatively suitable.

K ⁺the variation of ion concentration is to K _dthe impact of value is little.In the time not adding KCl, the K in this solution ⁺with Fe (NO ₃) ₆ ^4-the ratio of amount be 4:1.The K that potassium ferrocyanide itself provides ⁺ion concentration has met the required proportioning of formation KNiFC/Ni adsorbent, so, increase K ⁺the concentration of ion can not affect K yet _dvalue.

Several specific embodiments are provided below:

Embodiment 1

Accurately take a certain amount of 0.1gNi powder and 0.76gK ₄fe (CN) ₃3H ₂o, in 50mL beaker, adds 20mL deionized water by K ₄fe (CN) ₃3H ₂o dissolves completely.Then, under 95 ± 5 DEG C of water-baths, be slowly added dropwise to the HCl solution of 2mL2.4mol/L, constantly stirring reaction 30min, mixing speed is 750rpm, the about 30min of the static ageing of room temperature afterwards.Then, with the continuous washing precipitation of deionized water, until cleaning solution clear, and pH substantially constant till.Finally precipitation is placed in to 100 DEG C of freeze-day with constant temperature 20h.

Embodiment 2

Accurately take a certain amount of 0.1g Ni powder and 0.5g K ₄fe (CN) ₃3H ₂o, in 50mL beaker, adds 15mL deionized water by K ₄fe (CN) ₃3H ₂o dissolves completely.Then, under 95 ± 5 DEG C of water-baths, be slowly added dropwise to the HCl solution of 3.2mL1.0mol/L, constantly stirring reaction 20min, mixing speed is 600rpm, afterwards the static about 40min of room temperature.Then, with the continuous washing precipitation of deionized water, until cleaning solution clear, and pH substantially constant till.Finally precipitation is placed in to 90 DEG C of freeze-day with constant temperature 24h.

Embodiment 3

Accurately take a certain amount of 0.1g Ni powder and 1g K ₄fe (CN) ₃3H ₂o, in 50mL beaker, adds 20mL deionized water by K ₄fe (CN) ₃3H ₂o dissolves completely.Then, under 95 ± 5 DEG C of water-baths, be slowly added dropwise to the HCl solution of 2.2mL3.0mol/L, constantly stirring reaction 40min, mixing speed is 850rpm, afterwards the static about 20min of room temperature.Then, with the continuous washing precipitation of deionized water, until cleaning solution clear, and pH substantially constant till.Finally precipitation is placed in to 110 DEG C of freeze-day with constant temperature 10h.

Obviously, those skilled in the art can carry out various changes and modification and not depart from the spirit and scope of the present invention the present invention.Like this, if to these amendments of the present invention with within modification belongs to the scope of the claims in the present invention and equivalent technology thereof, the present invention is also intended to comprise these changes and modification interior.

Claims (10)

1. a preparation method for magnetic caesium selective absorbent, comprises the steps:

(1) to Ni powder and K ₄fe (CN) ₆3H ₂in the mixture of O, add deionized water, make K ₄fe (CN) ₆3H ₂o dissolves completely;

(2) gained dissolved matter is placed under water bath with thermostatic control, dropwise adds wherein HCl solution, and continuous stirring reaction a period of time;

(3), by gained reactant at room temperature static ageing a period of time, treat that crystalline structure growth is complete;

(4) precipitation generating with deionized water washing, until cleaning solution is water white transparency, and pH value substantially constant till;

(5) being deposited under constant temperature after washing is dried to constant weight, obtains ferrocyanide nickel potassium-nickel adsorbent.

2. the preparation method of magnetic caesium selective absorbent as claimed in claim 1, is characterized in that: Ni powder and the K described in step (1) ₄fe (CN) ₆3H ₂the mass ratio of O is 1:5～1:10, and the amount of deionized water adding is K ₄fe (CN) ₆3H ₂20～30 times of the quality of O.

3. the preparation method of magnetic caesium selective absorbent as claimed in claim 2, is characterized in that: Ni powder and the K described in step (1) ₄fe (CN) ₆3H ₂the quality of O is 1:7 than preferred value, and the amount of deionized water adding is K ₄fe (CN) ₆3H ₂26 times of the quality of O.

4. the preparation method of magnetic caesium selective absorbent as claimed in claim 1, is characterized in that: the temperature of the water bath with thermostatic control described in step (2) is 95 ± 5 DEG C.

5. the preparation method of the magnetic caesium selective absorbent as described in any one in claim 1-4, is characterized in that: the HCl solution concentration adding in step (2) is 1.0～3.0mol/L.

6. the preparation method of magnetic caesium selective absorbent as claimed in claim 5, is characterized in that: the HCl solution concentration preferred value adding in step (2) is 2.4mol/L.

7. the preparation method of magnetic caesium selective absorbent as claimed in claim 5, is characterized in that: in step (2), mixing speed is 600～850 revs/min.

8. the preparation method of magnetic caesium selective absorbent as claimed in claim 7, is characterized in that: in step (2), the reaction time is 20～40min.

9. the preparation method of magnetic caesium selective absorbent as claimed in claim 1, is characterized in that: in step (3), the time of static ageing is 20～40min.

10. the preparation method of magnetic caesium selective absorbent as claimed in claim 1, is characterized in that: in step (5), the temperature of freeze-day with constant temperature is 90～110 DEG C, and be 10-24h drying time.