CN108079936B - 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 lithium ion phosphate lithium ion sieve filler of light weight glass material covered by nanometer titanium dioxide. 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 the light glass material, and the adsorption capacity of the 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 glass fiber products, foam glass products, fly ash bleaching products with a density of less than 500kg/m ³ One of the beads or hollow glass microspheres. The invention adopts nano-TiO ₂ doping and coating to improve the adsorption capacity, stability and cycle life of the chromium phosphate lithium ion sieve.

Description

A kind of phosphate type 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 a filler composed of a nano-titania-coated chromium phosphate ion sieve supported on a lightweight glass material 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, 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 simple process, high recovery rate, good selectivity and environmental friendliness. The key to lithium extraction by ion sieve adsorption is to prepare a 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 leaching Li ⁺ in them with acid. Due to the size effect and sieving effect, lithium ion sieves have specific memory selectivity for Li ⁺ ions, and can separate Li ⁺ ions from other ions under 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 series lithium ion sieves, titanium series lithium ion sieves and other lithium ion sieves. The most studied precursors of manganese-based lithium ion sieves are mainly Li _1.3 Mn _1.6 O ₄ and Li _1.6 Mn _1.6 O ₄ . 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 precursors of titanium-based lithium ion sieves mainly include Li ₄ Ti ₅ O ₁₂ of spinel structure and Li ₂ TiO ₃ of monoclinic system. Compared with manganese-based lithium-ion sieves, titanium-based lithium-ion sieve adsorbents have the advantages of low dissolution loss 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) firstly 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 at 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 molar ratio of Li/Cr is too small, the adsorption capacity of lithium ions will be too small. If the molar ratio of Li/Cr is greater than 4, the adsorbent will be destroyed. structural stability. Generally, an inorganic acid aqueous solution with a pH of less than 3 is used to impregnate the precursor for delithiation to form a new phosphate-type adsorbent. The change. The deficiencies in 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 sieves are adsorption capacity, adsorption capacity stability, dissolution loss rate during recycling and regeneration, and cycle life. Lithium ion sieves are often made into granular or special-shaped packings in industrial applications to facilitate 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 by 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, resulting in its transmission. The blockage of the pores greatly reduces the adsorption capacity and adsorption rate of the formed lithium ion sieve filler. In practical applications, there is a lack of high-performance lithium ion sieve fillers with large adsorption capacity, good stability and long cycle life.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a phosphate type lithium ion sieve filler, especially the chromium phosphate ion sieve covered by nano titanium dioxide is loaded on the light glass material to form the filler, the porosity of the filler is 30%-60%, the density It 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, and the adsorption capacity of the lithium ion sieve filler It 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, powdered glass products with a density of less than 500kg/m ³ One of coal ash float beads or hollow glass microspheres.

In the present invention, the ion sieve precursor lithium chromium phosphate is a complex of chromium phosphate and lithium phosphate mLi ₃ PO ₄ ·CrPO ₄ , wherein m=1, 2, 3, and the molar ratio of Li/Cr is 3-9. The doping and cladding effects of TiO2 can stabilize the composition and structure of the formed molecular sieve even at very high Li/Cr levels, thus making it have a high theoretical adsorption capacity. After the lightweight glass material is loaded, the specific surface area of the lithium ion sieve is enlarged, and a large number of micro-channels formed on the surface provide a mass transfer channel for the adsorption and desorption of lithium ions. Better hydrophilicity, adsorption and desorption performance and anti-dissolution 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 5-15 nm. coating agent. The nano-TiO ₂ hydrosol gel solidified to form a porous film, and the existence of the coating film layer did not affect the mass transfer of lithium ions. Nano-TiO ₂ can be sintered together with light-weight glass-like materials at 300-400 ℃, and the coated lithium ion sieve is fixed, and the reduction of sintering temperature simplifies the production process and reduces the production cost. In the process of sintering heat treatment, nano- _TiO2 can be diffused and doped into lithium ion sieve molecules to improve its adsorption and desorption properties, and the lithium ions in the molecular sieve precursor can also be diffused into the nano- _TiO2 coating film. In fact, nano- _TiO2 itself It is an excellent lithium ion sieve material.

The innovative idea of coating the chromium phosphate ion sieve with nano- _{TiO 2} in the present invention is essentially different from the existing chromium phosphate ion sieve. The characteristics of the ion adsorption material not only improve the stability of the lithium chromium phosphate sieve, but also increase the adsorption capacity of the lithium ion sieve filler; at the same time, the preparation temperature of the lithium chromium phosphate sieve is reduced from above 500 ℃ by using the hydrothermal treatment method. Below 400℃, 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 a lithium chromate phosphate sieve precursor, the preparation of a nano-TiO ₂ hydrosol, and the batching of the lithium chromate phosphate sieve precursor filler. , sintering of chromium phosphate lithium ion sieve precursor filler, acid elution of chromium phosphate ion sieve precursor filler and evaluation of lithium chromium phosphate ion sieve, the specific steps are:

(1) Add 2mol/L ammonia water to the 2mol/L chromium sulfate aqueous solution until the solution is alkaline, filter and separate the generated Cr(OH) ₃ precipitate, wash the precipitate with deionized water until it does not contain sulfate ions; Add 1 mol/L lithium hydroxide aqueous solution, stir and dissolve to form a green solution; then slowly add it to the phosphoric acid aqueous solution under stirring, and immediately form the co-precipitation of Li ₃ PO ₄ and CrPO ₄ , and 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 12-16 h, concentrated, cooled and filtered to form a mLi ₃ PO ₄ ·CrPO ₄ complex, wherein m =1,2,3;

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

(3) The mLi ₃ PO ₄ · nCrPO ₄ composite was added to the nano-TiO ₂ hydrosol with a mass percentage concentration of 10% under stirring, so that the nano-TiO ₂ was coated on the surface of the lithium ion sieve precursor; The lightweight glass material is impregnated into the nano-TiO ₂ hydrosol containing lithium ion sieve precursor, and the mass ratio of the control material is: lightweight glass: precursor: nano-TiO ₂ = 1: 1.5-3: 0.3-0.5, flip light It is made of high quality glass carrier material, so that the precursor of lithium ion sieve is evenly attached to form a film, which is dried and cured at 100-150 ℃ after drying;

(4) Put it into a high-temperature furnace, heat treatment at 350-400 °C for 8-12 h, the nano-TiO ₂ -coated lithium ion sieve precursor is sintered and fixed on a light glass carrier, and the lithium chromium phosphate composite is heat-treated. During the process, a thermochemical reaction is carried out, the nano-TiO ₂ is doped into the lithium chromium phosphate molecule, and the unbound lithium is infiltrated and doped 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 packing in the adsorption tower, and spray the simulated brine containing 200mg/L lithium chloride for 4-16h to make it reach saturation adsorption, and the adsorption capacity is measured to be 15-20mg/g. The adsorption capacity also did not change significantly after 10 desorption cycles.

The adsorption capacity of the nano- _TiO2 -coated and light-weight glass-supported lithium ion sieve filler in the present invention is calculated by measuring the lithium ion concentration in simulated brine before and after adsorption by ion chromatography.

The experimental raw materials used in the present invention are chromium sulfate, titanyl sulfate, phosphoric acid, lithium hydroxide, ammonia water and lithium chloride, all of which are commercially available chemically pure reagents. The light-weight glass materials used are commercially available glass fiber, foam glass, fly ash float or hollow glass microspheres for thermal insulation and refractory materials.

The beneficial effects of the present invention are:

(1) Doping and coating with nano-TiO ₂ improves the adsorption capacity, stability and cycle life of the lithium chromium phosphate sieve;

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

Detailed ways

Example 1

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

In the 25mL of 2mol/L titanium oxysulfate aqueous solution, add 2mol/L ammoniacal liquor 50mL to make the solution alkaline, filter and separate the generated Ti(OH) Precipitation, wash the precipitation with deionized water until it does not contain _sulfate ions; Add 0.5mol/L oxalic acid aqueous solution 80mL, heat at 60-70 ℃ 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, 29.8 g of Li ₄ Cr(PO ₄ ) _2.5 composite was added to 40 g of nano-TiO ₂ hydrosol with a mass percentage concentration of 10%, and the mixture was evenly mixed so that the nano-TiO ₂ was coated on the surface of the lithium ion sieve precursor; Immerse 10 g of the cleaned glass fiber material into the nano-TiO ₂ hydrosol containing lithium ion sieve precursor, flip the glass fiber carrier material to make the lithium ion sieve precursor evenly attached to form a film, dry it at 100-150 ℃ Dry and cure. It was put into a high-temperature furnace and heat-treated at 400 °C for 8 h, and the nano- _TiO2 -coated lithium-ion sieve precursor was sintered and fixed on the glass fiber carrier. It was immersed in a 0.5 mol/L hydrochloric acid solution to desorb the lithium ions in the lithium ion sieve precursor, and then washed with deionized water to obtain 41 g of lithium ion sieve fillers coated with nano-TiO ₂ and supported by glass fibers. The lithium ion sieve packing was packed in the adsorption tower, and the simulated brine containing 200mg/L lithium chloride was sprayed for 8h to make it reach saturation adsorption. The capacity is 19 mg/g.

Example 2

To 2mol/L of chromium sulfate aqueous solution 12.5mL, add 2mol/L ammoniacal liquor 75mL to make the solution alkaline, filter and separate the generated Cr(OH ₎ Precipitation, wash the precipitation with deionized water until it does not contain sulfate ions; Add 1 mol/L lithium hydroxide aqueous solution 400 mL, stir and dissolve to form a green solution; then slowly add 2 mol/L phosphoric acid aqueous solution 100 mL under stirring, immediately form Li ₃ PO ₄ and CrPO ₄ co-precipitation, neutralize after The reaction solution was hydrothermally treated at 100-120° C. for 10 h, concentrated, cooled and filtered to obtain 23.0 g of a composite with a composition of Li ₈ Cr(PO ₄ ) _3.7 .

In the 25mL of 2mol/L titanium oxysulfate aqueous solution, add 2mol/L ammoniacal liquor 50mL to make the solution alkaline, filter and separate the generated Ti(OH) Precipitation, wash the precipitation with deionized water until it does not contain _sulfate ions; Add 0.5mol/L oxalic acid aqueous solution 80mL, heat at 60-70 ℃ 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, 23.0 g of Li ₄ Cr(PO ₄ ) _2.5 composite was added to 40 g of nano-TiO ₂ hydrosol with a mass percentage concentration of 10%, and the mixture was evenly mixed so that the nano-TiO ₂ was coated on the surface of the lithium ion sieve precursor; Immerse 10 g of cleaned fly ash float beads into the nano-TiO ₂ hydrosol containing lithium ion sieve precursor, and flip the fly ash float bead carrier material to make the lithium ion sieve precursor evenly attached to form a film, and then dried in the air. Dry and cure at 100-150°C. It was put into a high-temperature furnace and heat-treated at 400 °C for 8 h, and the nano- _TiO2 -coated lithium-ion sieve precursor was sintered and fixed on the fly ash floating bead carrier. It was immersed in 0.5mol/L hydrochloric acid solution to desorb the lithium ions in the lithium ion sieve precursor, and then washed with deionized water to obtain the lithium ion sieve fillers coated with nano-TiO ₂ and supported by fly ash float beads 34g. The lithium ion sieve packing was filled in the adsorption tower, and the simulated brine containing 200mg/L lithium chloride was sprayed for 12h to make it reach saturation adsorption. The capacity is 14.5 mg/g.

Claims (4)

1. The phosphate type lithium ion sieve filler is characterized in that the phosphate type lithium ion sieve filler is formed by loading a chromium phosphate ion sieve coated by nano titanium dioxide on a light glass material, the porosity of the filler is 30-60 percent, and the density is 400-800kg/m³The mass of the lithium ion sieve accounts for 55-65% of the mass of the filler, the mass of the nano titanium dioxide accounts for 10-15% of the mass of the filler, and the balance is the mass of the light glass material, and the adsorption capacity of the lithium ion sieve filler is 10-15 mg/g; the second nanometerThe titanium oxide is inorganic titanium salt hydrolysate with the particle size of 5-15 nm; the light glass material has a density of less than 500kg/m³The glass fiber product, the foam glass product, the fly ash floating bead or the hollow glass microsphere.

2. The phosphate-type lithium ion sieve filler of claim 1, wherein the ionic sieve precursor lithium chromium phosphate is a complex of chromium phosphate and lithium phosphate m L i₃PO₄· nCrPO₄Wherein the molar ratio of m =1, 2, 3, L i/Cr is 3-9.

3. The phosphate type lithium ion sieve filler according to claim 1, wherein the nano titanium dioxide is hydrosol prepared by hydrolysis-peptization of inorganic titanium salt, the particle size of the sol is 5-15nm, and the sol is used as a binder and a dopant of a lithium ion sieve precursor and an anti-solvent loss coating agent of the lithium ion sieve.

4. A preparation method of phosphate type lithium ion sieve filler is characterized in that the technical scheme comprises the steps of preparation of a chromium phosphate lithium ion sieve precursor and nano TiO₂The method comprises the following steps of hydrosol preparation, compounding of a chromium phosphate lithium ion sieve precursor filler, sintering of the chromium phosphate lithium ion sieve precursor filler, acid washing and lithium removing of the chromium phosphate lithium ion sieve precursor filler and evaluation of the chromium phosphate lithium ion sieve, and specifically comprises the following steps:

(1) adding 2 mol/L ammonia water into 2 mol/L chromium sulfate aqueous solution until the solution shows alkalinity, filtering and separating generated Cr (OH)₃Washing the precipitate with deionized water until the precipitate is free of sulfate ion, adding into 1 mol/L mol/mol lithium hydroxide aqueous solution, stirring to dissolve to form green solution, and slowly adding into phosphoric acid aqueous solution under stirring to form L i₃PO₄And CrPO₄The feeding molar ratio is controlled to be Cr: L i: P = 1: 4-8: 2.5-4.0, the neutralized reaction liquid is subjected to hydrothermal treatment at the temperature of 100 ℃ and 120 ℃ for 12-16h, and m L i is formed after concentration, cooling and filtration₃PO₄·CrPO₄A complex, wherein m =1, 2, 3;

(2) to 2 mol/LAdding 2 mol/L ammonia water into titanyl sulfate aqueous solution until the solution shows alkalinity, filtering and separating generated Ti (OH)₄Precipitating, washing the precipitate with deionized water until the precipitate is free of sulfate ion, adding into 0.5 mol/L mol/mol oxalic acid water solution, heating at 60-70 deg.C, and peptizing to form nanometer TiO₂The hydrosol is prepared by controlling the feeding molar ratio as follows: ti (OH)₄: oxalic acid = 1: 0.6 to 0.8 percent of the raw materials are concentrated in vacuum to obtain nano TiO with the mass percentage concentration of 10 percent₂Hydrosol with the particle size of 5-10 nm;

(3) m L i under stirring₃PO₄·CrPO₄Adding 10 percent of nano TiO into the compound by mass percentage₂In hydrosol, make nano TiO₂Coating the surface of the lithium ion sieve precursor; soaking the cleaned light glass material into nano TiO containing lithium ion sieve precursor₂In the hydrosol, the mass ratio of the materials is controlled as follows: light glass: precursor: nano TiO 2₂= 1: 1.5-3: 0.3-0.5, turning over the light glass carrier material to ensure that the lithium ion sieve precursor is uniformly attached to form a film, drying and curing at the temperature of 100 ℃ and 150 ℃;

(4) placing the mixture into a high temperature furnace, and carrying out heat treatment at the temperature of 350-400 ℃ for 8-12h to obtain nano TiO₂The coated lithium ion sieve precursor is sintered and fixed on a light glass carrier, the chromium phosphate lithium compound is subjected to thermochemical reaction in the heat treatment process, and the nano TiO₂Doping into chromium lithium phosphate molecules, and infiltrating and doping unbound lithium into nano TiO₂In the film;

(5) immersing the nano TiO into 0.5-1.0 mol/L hydrochloric acid solution to desorb lithium ions in the lithium ion sieve precursor, and then washing with deionized water to obtain nano TiO₂Coated and light glass-supported lithium ion sieve filler;

(7) filling the lithium ion sieve filler in an adsorption tower, and circularly spraying simulated brine containing 200 mg/L lithium chloride for 4-16h to achieve saturated adsorption, wherein the adsorption capacity is 15-20mg/g, and the adsorption capacity is not obviously changed after 10 times of adsorption and desorption circulation.