CN108079936A - A kind of phosphate type lithium ion sieve filler and preparation method thereof - Google Patents

Abstract

The invention relates to a phosphate-type lithium ion sieve filler, in particular to a chromium phosphate lithium ion sieve filler loaded by a light glass material coated with nano-titanium dioxide. The filler has a porosity of 30%-60% and a density of 400-800kg/ m ³ , the mass of lithium-ion sieve accounts for 55%-65% of the mass of the filler, the mass of nano-titanium dioxide accounts for 10%-15% of the mass of the filler, and the rest is the mass of light glass material. The adsorption capacity of lithium-ion sieve filler is 15-20mg/ g; the nano-titanium dioxide is prepared by the hydrolysis of inorganic titanium salt, and the particle size is 5-15nm; the light glass material is a glass fiber product, a foam glass product, a fly ash bleach with a density less than 500kg/ ^m3 One of beads or hollow glass microspheres. The invention adopts the doping and coating of nanometer _TiO2 to improve the adsorption capacity, stability and cycle life of the chromium phosphate lithium ion sieve.

Description

A kind of phosphate lithium ion sieve filler and preparation method thereof

technical field

The invention relates to a phosphate-type lithium ion sieve filler and a preparation method thereof, in particular to a lithium ion sieve filler loaded with a light glass material coated with nano-titanium dioxide and a preparation method thereof, belonging to the field of new energy and new materials.

technical background

With the rapid expansion of the lithium-containing material market and rising prices, the research on lithium sources has also expanded from traditional lithium ore extraction to the development and utilization of liquid lithium resources such as salt lake brine, seawater, and geothermal water. The ion sieve adsorption method has attracted much attention due to its advantages of simple process, high recovery rate, good selectivity and environmental friendliness. The key to extract lithium by ion sieve adsorption method is to prepare lithium ion sieve adsorbent with large adsorption capacity and good cycle performance. Lithium ion sieves are obtained by introducing template Li ⁺ into inorganic compounds, generating lithium ion sieve precursors through heat treatment, and then acid leaching Li ⁺ out of them. Due to the size effect and sieving effect, lithium ion sieve has specific memory selectivity for Li ⁺ ions, and can separate Li ⁺ ions from other ions in the coexistence of multiple ions. It is often used in lithium-rich solutions such as seawater or brine. Selective extraction of Li ⁺ .

At present, the most studied lithium-ion sieves mainly include manganese-based lithium-ion sieves, titanium-based lithium-ion sieves and other lithium-ion sieves. Li _1.3 Mn _1.6 O ₄ and Li _1.6 Mn _1.6 O ₄ are the precursors of manganese-based lithium ion sieves that have been studied more. Among them, Li _1.6 Mn _1.6 O ₄ is acid-washed to obtain MnO ₂ ·0.5H ₂ O-type lithium ion sieves. , this lithium ion sieve has the advantages of low manganese dissolution rate and good recycling performance. Common titanium-based lithium ion sieve precursors mainly include Li ₄ Ti ₅ O ₁₂ with spinel structure and Li ₂ TiO ₃ with monoclinic system. Compared with manganese-based lithium-ion sieve, titanium-based lithium-ion sieve adsorbent has the advantages of low dissolution rate, stable structure and good reusability. Other lithium ion sieves with larger lithium adsorption capacity mainly include aluminate, antimonate and phosphate types, but their research and development is not deep enough.

Japanese patent JP2001113164 (2001-04-24) first disclosed a new phosphate-type adsorbent and its preparation method. The molecular formula of the adsorbent precursor is Li ₂ Cr(PO ₄ ) _1.67 , which is heated above 500°C Lithium-containing chromium phosphate is prepared. It is preferable to control the molar ratio of Li/Cr in the molecule to 2. If the Li/Cr molar ratio is too small, the lithium ion adsorption capacity will be too small. If the Li/Cr molar ratio is greater than 4, the adsorbent will be destroyed. structural stability. Generally, the inorganic acid aqueous solution with pH less than 3 is used to impregnate the precursor for delithiation to form a new phosphate-type adsorbent. When it is applied to extract lithium from seawater, the adsorption capacity reaches 9.3mg/g, and it changes greatly with the pH of the solution. The change. The disadvantages of the prior art are that the adsorbent is in powder form, its fluidity and permeability are poor, the adsorption and desorption time is long, and the dissolution loss during recovery and regeneration is relatively large.

The main technical indicators of lithium ion sieve are adsorption capacity, adsorption capacity stability, dissolution loss rate during recovery and regeneration, and cycle life. Lithium-ion sieves are often made into granular or special-shaped fillers in industrial applications, so as to carry out continuous operation of packed towers and reduce recovery losses. At present, most of the granular or special-shaped fillers suitable for tower operation are prepared through the cross-linking of organic polymer materials. Since the organic polymer solution may enter the pores of the lithium-ion sieve during the filler molding process, causing its transmission Due to the blockage of the pores, the adsorption capacity and adsorption rate of the formed lithium-ion sieve packing are greatly reduced. In practical applications, there is a lack of high-performance lithium-ion sieve packing with large adsorption capacity, good stability and long cycle life.

Contents of the invention

The purpose of the present invention is to provide a phosphate-type lithium ion sieve filler, especially a chromium phosphate lithium ion sieve filler loaded by nano-titanium dioxide-coated light glass material, the porosity of the filler is 30%-60%, and the density is 400 -800kg/m ³ , the mass of lithium ion sieve accounts for 55%-65% of the mass of the filler, the mass of nano-titanium dioxide accounts for 10%-15% of the mass of the filler, and the rest is the mass of light glass material. The adsorption capacity of lithium ion sieve filler is 10% -15mg/g; the nano-titanium dioxide is an inorganic titanium salt hydrolyzate with a particle size of 5-15nm; the light glass material is glass fiber products, foam glass products, fly ash with a density less than 500kg/ ^m One of the floating beads or hollow glass microspheres.

In the present invention, the ion sieve precursor lithium chromium phosphate is the compound mLi ₃ PO ₄ ·CrPO ₄ of chromium phosphate and lithium phosphate, wherein, m=1, 2, 3, and the molar ratio of Li/Cr is 3-9, because The doping and coating of nano-titanium dioxide can stabilize the composition and structure of molecular sieves even under very high Li/Cr, so that it has a high theoretical adsorption capacity. After being loaded with light glass material, the specific surface area of the lithium ion sieve is enlarged, and a large number of micropores formed on the surface provide mass transfer channels for the adsorption and desorption of lithium ions. The filler molding treatment does not affect the adsorption and desorption speed, making it have Better hydrophilicity, adsorption and desorption performance and anti-solution loss ability.

In the present invention, nano-titanium dioxide is a hydrosol prepared by hydrolysis-peptization of inorganic titanium salt, and the particle size of the sol is 5-15nm. Covering agent. The nano-TiO ₂ hydrosol gel solidifies to form a porous membrane, and the existence of the coating layer does not affect the mass transfer of lithium ions. Nano TiO ₂ can be sintered with light glass materials at 300-400°C to fix the coated lithium ion sieve. The reduction of sintering temperature simplifies the production process and reduces the production cost. During the sintering heat treatment process, nano-TiO ₂ can be diffused and doped into lithium ion sieve molecules to improve its adsorption and desorption properties. Lithium ions in the molecular sieve precursor can also diffuse into the nano-TiO ₂ coating film. In fact, nano-TiO ₂ itself It is an excellent lithium ion sieve material.

The innovative idea of coating chromium phosphate ion sieve with nano-TiO ₂ in the present invention is essentially different from the existing chromium phosphate ion sieve, and fully utilizes that nano-TiO ₂ is not only a film-forming material coated with chromium phosphate ion sieve, but also a lithium ion sieve. The characteristics of ion adsorption materials not only improve the stability of chromium phosphate lithium ion sieve, but also improve the adsorption capacity of lithium ion sieve filler; at the same time, with the use of hydrothermal treatment method, the preparation temperature of chromium phosphate lithium ion sieve is reduced from above 500 ℃ Below 400°C, it has creativity and good practical value.

Another object of the present invention is to provide a method for preparing a phosphate-type lithium ion sieve filler. The technical solution includes the preparation of the chromium phosphate lithium ion sieve precursor, the preparation of nano- _TiO2 hydrosol, and the batching of the chromium phosphate lithium ion sieve precursor filler , sintering of chromium phosphate lithium ion sieve precursor filler, acid elution of lithium chromium phosphate ion sieve precursor filler and evaluation of chromium phosphate lithium ion sieve, the specific steps are:

(1) Add 2 mol/L ammonia water to 2 mol/L chromium sulfate aqueous solution until the solution becomes alkaline, filter and separate the generated Cr(OH) ₃ precipitate, wash the precipitate with deionized water until it does not contain sulfate ions; Add 1mol/L lithium hydroxide aqueous solution, stir and dissolve to form a green solution; then slowly add phosphoric acid aqueous solution under stirring, immediately form a coprecipitation of Li ₃ PO ₄ and CrPO ₄ , control the molar ratio of feeding: Cr: Li: P=1:4-8:2.5-4.0; the neutralized reaction solution was hydrothermally treated at 100-120°C for 12-16h, concentrated, cooled, and filtered to form mLi ₃ PO ₄ ·CrPO ₄ complexes, where m =1,2,3;

(2) Add 2 mol/L ammonia water to 2 mol/L titanyl sulfate aqueous solution until the solution becomes alkaline, filter and separate the formed Ti(OH) ₄ precipitate, wash the precipitate with deionized water until it does not contain sulfate ions; It is added to 0.5mol/L oxalic acid aqueous solution, heated and peptized at 60-70°C to form a nano-TiO ₂ hydrosol, and the molar ratio of the feed is controlled to be: Ti(OH) ₄ : oxalic acid=1:0.6-0.8, and concentrated in a vacuum to obtain Nano TiO ₂ hydrosol with a concentration of 10% by mass, the particle size of the sol is 5-10nm;

(3) Add the mLi ₃ PO ₄ nCrPO ₄ complex to the nano-TiO ₂ hydrosol with a concentration of 10% by mass under stirring, so that the nano-TiO ₂ is coated on the surface of the lithium ion sieve precursor; The lightweight glass material is impregnated into the nano-TiO ₂ hydrosol containing the lithium ion sieve precursor, and the mass ratio of the feed is controlled as follows: light glass: precursor: nano-TiO ₂ =1:1.5-3:0.3-0.5, and the stirring is light High-quality glass carrier material, so that the lithium-ion sieve precursor can be evenly attached to form a film, and then dried and solidified at 100-150 ° C after drying;

(4) Put it into a high-temperature furnace and heat-treat it at 350-400°C for 8-12h. The lithium-ion sieve precursor coated with nano-TiO ₂ is sintered and fixed on a light glass carrier. During the thermochemical reaction, the nano-TiO ₂ is doped into the chromium lithium phosphate molecule, and the unbound lithium is infiltrated into the nano-TiO ₂ film;

(5) Immerse it in a 0.5-1.0mol/L hydrochloric acid solution to desorb the lithium ions in the lithium-ion sieve precursor, and then wash it with deionized water to obtain nano-TiO ₂ -coated and lightweight glass-supported lithium Ion sieve packing;

(7) Fill the lithium-ion sieve filler in the adsorption tower, and spray the simulated brine containing 200mg/L lithium chloride for 4-16 hours to make it reach saturated adsorption. The measured adsorption capacity is 15-20mg/g, and the absorption The adsorption capacity did not change significantly after 10 desorption cycles.

In the present invention, the adsorption capacity of the lithium ion sieve packing coated with nanometer _TiO2 and loaded by light glass is calculated by using ion chromatography to measure the concentration of lithium ions in the simulated brine before and after adsorption.

The experimental raw materials used in the present invention are chromium sulfate, titanyl sulfate, phosphoric acid, lithium hydroxide, ammonia water and lithium chloride are commercially available chemical reagents. The light glass material used is glass fiber, foam glass, fly ash floating beads or hollow glass microspheres for thermal insulation and refractory materials available on the market.

The beneficial effects of the present invention are:

(1) The adsorption capacity, stability and cycle life of chromium phosphate lithium ion sieve are improved by nano-TiO ₂ doping and coating;

(2) The formation, sintering and molding of the chromium phosphate lithium ion sieve filler precursor are completed at 350-400°C at one time, which simplifies the process and reduces the production cost.

Detailed ways

Example 1

Add 150mL of 2mol/L ammonia water to 25mL of 2mol/L chromium sulfate aqueous solution to make the solution alkaline, filter and separate the generated Cr(OH) ₃ precipitate, wash the precipitate with deionized water until it does not contain sulfate ions; add it to 1mol/L lithium hydroxide aqueous solution 400mL, stir and dissolve to form a green solution; then slowly add 2mol/L phosphoric acid aqueous solution 125mL under stirring, immediately form a coprecipitation of Li ₃ PO ₄ and CrPO ₄ , neutralize the The reaction solution was hydrothermally treated at 100-120° C. for 12 hours, concentrated, cooled, and filtered to obtain 29.8 g of a compound with a composition of Li ₄ Cr(PO ₄ ) _2.3 .

In the titanyl sulfate aqueous solution 25mL of 2mol/L, add the ammoniacal liquor 50mL of 2mol/L to make the solution alkaline, filter and separate the Ti(OH) _{4precipitation} , clean the precipitation with deionized water to no sulfate ion; Add 0.5mol/L oxalic acid aqueous solution 80mL, heat and peptize at 60-70°C to form nano-TiO ₂ hydrosol, and vacuum concentrate to obtain 40g of nano-TiO ₂ hydrosol with a mass percentage concentration of 10%.

Under stirring, add 29.8 g of Li ₄ Cr(PO ₄ ) _2.5 composite into 40 g of nano-TiO ₂ hydrosol with a concentration of 10% by mass, and mix evenly so that nano-TiO ₂ is coated on the surface of the lithium ion sieve precursor; Immerse 10g of the cleaned glass fiber material into the nano-TiO ₂ hydrosol containing the lithium ion sieve precursor, turn over the glass fiber carrier material, so that the lithium ion sieve precursor is evenly attached to form a film, and dry it at 100-150°C Dry and solidify. It was put into a high-temperature furnace and heat-treated at 400 °C for 8 h, and the nano-TiO ₂ -coated lithium ion sieve precursor was sintered and fixed on the glass fiber support. Immerse it in a 0.5mol/L hydrochloric acid solution to desorb the lithium ions in the lithium ion sieve precursor, and then wash it with deionized water to obtain 41 g of lithium ion sieve fillers coated with nano- _TiO and supported by glass fibers. Fill the lithium-ion sieve filler in the adsorption tower, and spray the simulated brine containing 200mg/L lithium chloride for 8 hours to make it reach saturated adsorption. The measured adsorption capacity is 20mg/g, and after 10 cycles of adsorption and desorption The capacity is 19mg/g.

Example 2

Add 2mol/L ammoniacal liquor 75mL in the 2mol/L chromium sulfate aqueous solution 12.5mL to make the solution alkaline, filter and separate the Cr(OH) _{3precipitation} , clean the precipitation with deionized water to no sulfate ion; Add 1mol/L lithium hydroxide aqueous solution 400mL, stir and dissolve to form a green solution; then slowly add 2mol/L phosphoric acid aqueous solution 100mL under stirring, and immediately form a co-precipitation of Li ₃ PO ₄ and CrPO ₄ , neutralize The reaction solution was hydrothermally treated at 100-120° C. for 10 h, concentrated, cooled, and filtered to obtain 23.0 g of a compound with a composition of Li ₈ Cr(PO ₄ ) _3.7 .

In the titanyl sulfate aqueous solution 25mL of 2mol/L, add the ammoniacal liquor 50mL of 2mol/L to make the solution alkaline, filter and separate the Ti(OH) _{4precipitation} , clean the precipitation with deionized water to no sulfate ion; Add 0.5mol/L oxalic acid aqueous solution 80mL, heat and peptize at 60-70°C to form nano-TiO ₂ hydrosol, and vacuum concentrate to obtain 40g of nano-TiO ₂ hydrosol with a mass percentage concentration of 10%.

Under stirring, add 23.0 g of Li ₄ Cr(PO ₄ ) _2.5 composite into 40 g of nano-TiO ₂ hydrosol with a concentration of 10% by mass, and mix evenly so that nano-TiO ₂ is coated on the surface of the lithium ion sieve precursor; Immerse 10 g of cleaned fly ash floating beads into the nano- _TiO2 hydrosol containing the lithium ion sieve precursor, turn over the fly ash floating bead carrier material, so that the lithium ion sieve precursor is evenly attached to form a film, and after drying, place the Dry and solidify at 100-150°C. It was put into a high-temperature furnace and heat-treated at 400 °C for 8 h, and the nano-TiO ₂ -coated lithium ion sieve precursor was sintered and fixed on the fly ash floating bead carrier. Immerse it in a 0.5mol/L hydrochloric acid solution to desorb the lithium ions in the lithium-ion sieve precursor, and then wash it with deionized water to obtain a lithium-ion sieve filler coated with nano- _TiO2 and loaded with fly ash floating beads 34g. Fill the lithium-ion sieve filler in the adsorption tower, and spray the simulated brine containing 200mg/L lithium chloride for 12 hours to make it reach saturated adsorption. The measured adsorption capacity is 15mg/g, and after 10 cycles of adsorption and desorption The capacity is 14.5mg/g.

Claims (4)

1. A phosphate type lithium ion sieve filler, characterized in that the chromium phosphate ion sieve loaded by the light glass material covered by nano-titanium dioxide forms the filler, the porosity of the filler is 30%-60%, and the density is 400-800kg /m ³ , the mass of lithium ion sieve accounts for 55%-65% of the mass of the filler, the mass of nano-titanium dioxide accounts for 10%-15% of the mass of the filler, the rest is the mass of light glass material, and the adsorption capacity of lithium ion sieve filler is 10-15mg /g; the nano-titanium dioxide is an inorganic titanium salt hydrolyzate with a particle size of 5-15nm; the light glass material is glass fiber products, foam glass products, fly ash floating beads with a density less than 500kg/ ^m or one of the hollow glass microspheres. 2. The phosphate lithium ion sieve packing according to claim 1, characterized in that the ion sieve precursor lithium chromium phosphate is a composite of chromium phosphate and lithium phosphate mLi ₃ PO ₄ nCrPO ₄ , wherein m=1 , 2,3, the molar ratio of Li/Cr is 3-9. 3. The phosphate-type lithium ion sieve filler according to claim 1, characterized in that nano-titanium dioxide is a hydrosol prepared by hydrolysis-peptization of inorganic titanium salt, and the particle size of the sol is 5-15nm, as a lithium ion sieve precursor Adhesives, dopants and anti-dissolution coating agents for lithium ion sieves. 4. A preparation method for a phosphate lithium ion sieve filler, characterized in that the technical scheme includes the preparation of a chromium phosphate lithium ion sieve precursor, the preparation of nano- _TiO2 hydrosol, the batching of the chromium phosphate lithium ion sieve precursor filler, chromium phosphate The sintering of the lithium ion sieve precursor filler, the acid elution of the chromium phosphate ion sieve precursor filler and the evaluation of the chromium phosphate lithium ion sieve, the specific steps are: (1) Add 2 mol/L ammonia water to 2 mol/L chromium sulfate aqueous solution until the solution becomes alkaline, filter and separate the generated Cr(OH) ₃ precipitate, wash the precipitate with deionized water until it does not contain sulfate ions; Add 1mol/L lithium hydroxide aqueous solution, stir and dissolve to form a green solution; then slowly add phosphoric acid aqueous solution under stirring, immediately form a coprecipitation of Li ₃ PO ₄ and CrPO ₄ , control the molar ratio of feeding: Cr: Li: P=1:4-8:2.5-4.0; the neutralized reaction solution was hydrothermally treated at 100-120°C for 12-16h, concentrated, cooled, and filtered to form mLi ₃ PO ₄ ·CrPO ₄ complexes, where m =1,2,3; (2) Add 2 mol/L ammonia water to 2 mol/L titanyl sulfate aqueous solution until the solution becomes alkaline, filter and separate the formed Ti(OH) ₄ precipitate, wash the precipitate with deionized water until it does not contain sulfate ions; It is added to 0.5mol/L oxalic acid aqueous solution, heated and peptized at 60-70°C to form a nano-TiO ₂ hydrosol, and the molar ratio of the feed is controlled to be: Ti(OH) ₄ : oxalic acid=1:0.6-0.8, and concentrated in a vacuum to obtain Nano TiO ₂ hydrosol with a concentration of 10% by mass, the particle size of the sol is 5-10nm; (3) Add the mLi ₃ PO ₄ ·CrPO ₄ complex to the nano-TiO ₂ hydrosol with a mass percent concentration of 10% under stirring, so that the nano-TiO ₂ is coated on the surface of the lithium ion sieve precursor; The lightweight glass material is impregnated into the nano-TiO ₂ hydrosol containing the lithium ion sieve precursor, and the mass ratio of the feed is controlled as follows: light glass: precursor: nano-TiO ₂ =1:1.5-3:0.3-0.5, and the stirring is light High-quality glass carrier material, so that the lithium-ion sieve precursor can be evenly attached to form a film, and then dried and solidified at 100-150 ° C after drying; (4) Put it into a high-temperature furnace and heat-treat it at 350-400°C for 8-12h. The lithium-ion sieve precursor coated with nano-TiO ₂ is sintered and fixed on a light glass carrier. During the thermochemical reaction, the nano-TiO ₂ is doped into the chromium lithium phosphate molecule, and the unbound lithium is infiltrated into the nano-TiO ₂ film; (5) Immerse it in a 0.5-1.0mol/L hydrochloric acid solution to desorb the lithium ions in the lithium-ion sieve precursor, and then wash it with deionized water to obtain nano-TiO ₂ -coated and lightweight glass-supported lithium Ion sieve packing; (7) Fill the lithium-ion sieve filler in the adsorption tower, and spray the simulated brine containing 200mg/L lithium chloride for 4-16 hours to make it reach saturated adsorption. The measured adsorption capacity is 15-20mg/g, and the absorption The adsorption capacity did not change significantly after 10 desorption cycles.