KR101910403B1 - Method for preparing hto lithium ion adsorbent and lithium ion recovery uses thereof - Google Patents

Abstract

The present invention relates to a method for producing an HTO lithium adsorbent and a lithium recovery method using the same. According to the present invention, a HTO lithium adsorbent can be produced by a relatively simple method. The lithium adsorbent produced according to the present invention exhibits high selectivity for lithium ions compared to conventional lithium adsorbents and is capable of adsorbing lithium ions in a solution at a relatively high pH and can be re-adsorbed repeatedly with the same adsorbent High adsorption ability can be maintained.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for preparing an HTO lithium adsorbent, and a method for recovering lithium using the HTO lithium adsorbent.

More particularly, the present invention relates to a method for preparing HTO (lithium hydrogen oxide) lithium adsorbent and a lithium recovery method using the HTO lithium adsorbent. More particularly, the present invention relates to an HTO lithium adsorbent which has high selectivity for lithium ion and maintains adsorbability even when repeatedly adsorbed. And a lithium recovery method using the same.

Recently, demand for lithium ion (Li ⁺ ) is increasing due to interest in green energy including electric vehicles. Saltwater lake and seawater are good sources of lithium but have difficulties in recovering lithium ions due to their various compositions. For example, not only lithium ions but also lithium ions exist in the salt water bath at a considerably high concentration. Likewise, sea water contains 2.5 x 10 ^-14 kg of lithium ions, but due to Na ⁺ , K ⁺ , Mg ²⁺ and Ca ²⁺ , the lithium ion content is diluted to 0.17 mg L ^-1 (R Chitrakar, H. Kanoh, Y. Miyai, K. Ooi et al., Ind.Eng.Chem . Res . 40: 2054-2058, 2001).

Conventional precipitation, solvent extraction and salting methods are time-consuming, require large quantities of reagents and are low throughput processes. On the other hand, lithium ion sieves (LIS) selectively adsorbing only lithium ions are in the spotlight as efficient lithium ion recovery technologies because of simple processes (L. Zhang, D. Zhou, G. He, F. Wang, J. Zhou et al., Mater. Lett . 135: 206-209, 2014, A. Hamzaoui, H. Hammi, A. M'inif et al., Russ J. Inorg. Chem. 52: 1859-1863, 2007, K. Yoshizuka, A. Kitajou, M. Holba et al., Ars Separatoria Acta 4: 78-85, 2006). A spinel type manganese based LIS such as lithium manganese oxide or LMO (ie Li _1.6 Mn _1.6 O ₄ , Li _1.33 Mn _1.67 O ₄ , LiMn ₂ O ₄ ) is capable of recovering lithium ions up to 43 mg g ^-1 X. Yang, J. Wang, P. Li, J. Yu et al., Ind. Eng. Chem. Res . 52: 11967-11973, 2013, X. Yang, H. .. Kanoh, W. Tang, K. Ooi et al, J. Mater Chem 10:.. 1903-1909, 2000, T. Wajima, K. Munakata, T. Uda et al, Plasma Fusion Res 7:. 2405021- 2405021, 2012). However, there is a concern that the long-term use of LMO results in the dissolution of LIS due to the elution of Mn ²⁺ during acid treatment (E. Saenko, G. Leont'eva, V. Vol'khin, A. Kolyshkin et al., J. Inorg. Chem . 52: 1312-1316, 2007). Therefore, research on a more stable and efficient LIS is still proceeding.

On the other hand, monoclinic lithium metatitanic acid (Li ₂ TiO ₂ ) is used as a negative electrode material in a lithium battery and as a tritium breeding material in a fusion reaction solution. Li ₂ TiO ₂ is synthesized through solid phase reaction of titanium oxide (TiO ₂ ) and lithium carbonate (Li ₂ CO ₃ ). Li ₂ TiO ₂ (LTO) has a higher extractable Li ⁺ fraction compared to LMO, which theoretically has a higher Li ⁺ adsorptivity (127 vs. 68 mg g ^-1 ) than LMO (X. Shi, Z Zhang, D. Zhou, L. Zhang, B. Chen, L. Yu et al., Trans.Nonferrous Met. Soc. China 23: 253-259, 2013).

However, research on H ₂ TiO ₃ (HTO) as an LIS has not been done yet.

Korean Patent No. 10-0972140

An object of the present invention is to provide a method for producing an HTO (titanium hydrogen oxide) lithium ion adsorbent, which has higher selectivity for lithium ion than conventional lithium ion adsorbents and maintains adsorbability even when repeatedly adsorbing, To provide a way to do that.

In order to accomplish the above object, the present invention provides a method of producing an HTO (titanium hydrogen-compound) lithium adsorbent comprising the step of dispersing an LTO (lithium titanium compound) powder in an acidic solution.

Li ⁺ and H ⁺ of LTO can be exchanged through the step of dispersing in the acidic solution.

The LTO can be synthesized by mixing anatase-type TiO ₂ and lithium carbonate (Li ₂ CO ₃ ) and then heat-treating them.

Lithium and titanium of the LTO may be configured in a molar ratio of 2: 1.

The step of dispersing in the acidic solution may be carried out at 20 to 50 ° C, preferably at 30 ° C.

The acidic solution may include at least one selected from the group consisting of HCl, H ₂ SO ₄ , H ₂ PO _4, and HNO ₃ , and may preferably include HCl or HNO ₃ .

The concentration of the acid solution may be 0.1 mol / L to 0.5 mol / L, preferably 0.2 mol / L.

After the step of dispersing in the acidic solution, the dispersion may be filtered and then washed until a neutral pH is reached.

The LTO may be Li ₂ TiO ₃ , and the HTO may be H ₂ TiO ₃ .

The present invention also provides a process for preparing HTO lithium adsorbent comprising: (a) dispersing an LTO powder in an acidic solution to produce an HTO lithium adsorbent; (b) adsorbing lithium by adding the adsorbent prepared in step (a) to a solution containing lithium; And (c) recovering lithium from the adsorbent on which lithium is adsorbed.

The acidic solution may include at least one selected from the group consisting of HCl, H ₂ SO ₄ , H ₂ PO ₄ and HNO ₃ .

The lithium-containing solution of step (b) may include at least one selected from the group consisting of saline water, seawater, and industrial wastewater.

According to the present invention, a HTO lithium adsorbent can be produced in a relatively simple manner. The lithium adsorbent produced according to the present invention exhibits high selectivity for lithium ions compared to conventional lithium adsorbents and is capable of adsorbing lithium ions in a solution at a relatively high pH and can be re-adsorbed repeatedly with the same adsorbent High adsorption ability can be maintained.

1 is an X-ray diffraction pattern of HTO adsorbing LTO, HTO and Li ⁺ .
2 is the nitrogen adsorption-desorption isotherm of the LTO and HTO powders, and the insertion degrees are the BET coordinates of LTO and HTO.
3 is a SEM image of LTO, (b) a particle size distribution of LTO, (c) an SEM image of HTO, and (d) a particle size distribution of HTO.
4 shows the Li ⁺ adsorption performance of HTO according to (a) equilibrium pH of HTO and (b) initial pH.
5 shows the Li ⁺ adsorption performance of HTO according to the S / L ratio.
6 is (a) Langmuir model coordinates and (b) Freundlich model coordinates for Li ⁺ adsorption of HTO.
FIG. 7 shows the effect of temperature on the Li ⁺ adsorption performance of HTO, and the degree of insertion shows thermodynamic coordinates.
Figure 8 is a time profile for Li ⁺ adsorption performance of HTO.
9 shows the (a) Lagergren and pseudo-secondary reaction rate models, (b) the C _e time profile and (c) the shrinkage nuclear model of Li ⁺ adsorption performance of HTO.
FIG. 10 shows (a) lithium adsorption performance and (b) Ti ⁴⁺ loss% of HTO powder in five adsorption-desorption experiments.
Figure 11 is an X-ray diffraction pattern of HTO powder after the first and fifth adsorption-desorption cycles.

Hereinafter, the present invention will be described in more detail with reference to Examples. The objects, features and advantages of the present invention will be readily understood through the following examples. The present invention is not limited to the embodiments described herein, but may be embodied in other forms. The embodiments described herein are provided to enable those skilled in the art to fully understand the spirit of the present invention. Therefore, the present invention should not be limited by the following examples.

Preparation of materials

(TiO ₂ , TiO ₂ , TiO ₂ ) of the lithium carbonate powder (Li ₂ CO ₃ , ≥98.0%) of Fluka (USA) as a precursor for the synthesis of Li ₂ TiO ₃ and the titanium oxide (IV) powder of Aldrich (USA) anatase, 99.8%) were used. Hydrochloric acid (HCl, RHM 35-37%) and nitric acid (HNO ₃ , RHM 60%) from Junsei Chemical Co., Ltd. (Japan) were prepared by depolitilizing LTO and pretreating oxides for elemental analysis (acid digestion pretreatment). Lithium chloride (LiCl, ≥98%) of lithium hydroxide (LiOH, ≥98%) and Sigma-Aldrich (Sigma-Aldrich (Mo., USA)) and Fluka (Germany) ≪ / RTI > Methylene blue dehydrate (95%) and ascorbic acid from Showa Chemical Co. Ltd. (Japan) were used to measure titanium (IV) by in-solution spectrophotometry. All chemicals were used without further purification.

Analysis method

Elemental analysis was performed with ICP-MS (Agilent 7500 series, USA). All collected liquid samples were filtered with a 0.2 μm nylon syringe filter. Portions of each sample were measured for pH using the SI Analytics pH probe (N5900A) in a TitroLine 7000 titrator (SI Analytics GmbH, Germany). Prior to ICP-MS, aliquots of the filtered sample (2 mL) was pretreated with a microwave (MARS-5 CEM, USA) digestion acid _{(60% HNO 3 3 mL)} . The digested samples were transferred-filtered in a 100 mL polypropylene scalpel and diluted with deionized water if necessary.

Example 1: Synthesis of HTO lithium adsorbent

LTO was synthesized by a known method (R. Chitrakar, Y. Makita, K. Ooi, A. Sonoda et al., Dalton Trans . 43: 8933-8939, 2014). Ana Tasman type TiO ₂ and _{Li 2 CO 3 (2: 1} Li / Ti mol ratio) mixture of and, to go from the agate mortar (agate mortar) for 20 minutes was heat-treated for 4 hours in the following, air (6 ℃ min ^{- 1} , 700 ° C). After cooling to room temperature, the LTO powder was sieved through a mortar and pestle and sieved to obtain a narrow particle size distribution (No. 200, Φ = 63 μm). The sieved LTO was dispersed in 0.2 mol L ^-1 of HCl solution (1 g L ^-1 ) at 30 ° C for 24 hours to exchange Li ⁺ and H ⁺ , and HTO was synthesized. The dispersion was vacuum filtered and washed with deionized water until a neutral pH was reached. And then dried in an oven at 30 DEG C for 12 hours to finally obtain a lithium adsorbent.

Experimental Example 1: Physical properties of HTO lithium adsorbent

1-1: Structural / morphological characterization of HTO lithium adsorbent

LTO and HTO were identified by X-ray spectroscopy (40 kV, 30 mA, 0.03 step count- ¹ , Cu Kα source, PANalytical X'pert-Pro, The Netherlands). The shapes of the two powders were observed with a scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDX, Hitachi S-3500 N, Japan). The density was measured by the pycnometer method, and the Brunauer-Emmet-Teller (BET) surface area was measured by Belsorp-mini (Bel Japan, Inc.). Nitrogen adsorption / desorption isotherms were measured in a relative pressure range between 0.01 and 1.0 ( pp _o ^-1 ). On the other hand, the pore size distribution was calculated by the Barrett-Joiner-Halenda (BJH) method.

X-ray spectroscopic analysis results are shown in Fig. The spectral peaks of HTO were similar to those of LTO, but the signals were very weak. In addition, the peak of HTO shifted slightly to the right (17.5 ° <2θ <19.0 ° and 35.0 ° <2θ <37.5 °), asymmetrically dispersed (20.5 ° <2θ <24 °) ˚ <2θ <48˚). In addition, some characteristic spectral peaks (133, 206) disappeared after acid treatment, indicating that the crystalline structure of HTO was modified. This spectral change means that H ⁺ (radius ~ 0.0012 nm) with a small radius is inserted into the empty lattice by Li ⁺ (radius ~ 0.076 nm) with large radius after extraction. The exchange of Li ⁺ and H ⁺ ion-bonded in the HTO occurs electrostatically in the lattice and consequently the crystal structure becomes narrower and smaller (G. He, L. Zhang, D. Zhou, Y. Zou, F Wang et al., Ionics 21: 2219-2226, 2015).

On the other hand, the LTO peak disappearing from the HTO peak did not appear again in the Li ⁺ adsorbed HTO. This means that Li ⁺ bonds in the LTO were irreversibly destroyed during the first acid treatment (the depolymerization process).

After acid treatment, the structural change (LTO) in LTO was confirmed by the nitrogen adsorption-desorption curve at 77 K (FIG. 2). LTO shows the adsorption-desorption isotherm of the mold while HTO is the adsorption-desorption isotherm of the mold with the H3-type hysteresis loop. The hysteresis loop of HTO appeared at pp _o ^-1 ~ 0.85, but not in LTO. This means that 16 ~ 46 nm pores were formed in the HTO according to the depolymerization process, which could be confirmed by the BJH method. An increase in the BET surface area also means that voids are formed within the HTO (18.2 m ² g ^-1 vs. 4.9 m ² g ^-1 LTO).

On the other hand, changes in particle shape after the depolymerization process could not be confirmed by SEM (FIG. 3). It was confirmed that the LTO powder prepared by the solid phase reaction contained two types of soft particles (100-300 nm) having a center diameter d ₁ = 128 nm and d ₂ = 166 nm. On the other hand, the HTO particles were found to have particles of a similar shape and size to those of LTO after the acid treatment, but they were found to have rough edges and fine cracks on the surface compared to LTO.

1-2: Confirmation of adsorption capacity of HTO lithium adsorbent

The lithium adsorption experiments were performed at least twice at 30 ℃ (303K). The typical number of equilibrium adsorption was performed by adding dry HTO ( m ) in a Li ⁺ feed sample with known volume ( V ) and Li ⁺ concentration ( C _o ). After 24 hours of incubation (175 rpm), the equilibrated samples were filtered and the pH and equilibrium Li ⁺ concentration ( C _e ) were measured. Adsorption capacity (q _e) levels were calculated with the equation (1) (J. Xiao, S. Sun, J. Wang, P. Li, J. Yu et al, Ind Eng Chem Res 52:..... 11967- Kim, WJ Chung, et al., Chem. Eng ., 280, 11973, 2013, G. Nisola, L. Limjuco, E. Vivas, C. Lawagon, MJ Park, HK Shon, N. Mittal, IW Nah, : 536-548, 2015).

(One)

Initial experiments were performed on purified LiOH with C _o = 70 mg L ^-1 (pH = 12), S / L ratio = 3.33 g L ^-1 . The pH of the solution was adjusted using 1 M HCl to obtain the pH (4-12). To determine the effect on the accumulation of H ⁺ q _e according to the Li ⁺ adsorption proceeds, the experiment was carried out using ammonium buffer solution _{0.1 M (NH 3 + NH 4} Cl) (pH = 8, 9). On the other hand, in order to observe the effect of the S / L ratio on q _e , the experiment was carried out while changing the volume of the Li ⁺ solution having pH = 11 and C _o = 70 mgL ^-1 in the fixed m = 40 mg of HTO . In addition, adsorption was performed at different temperatures (30-60 ° C) to observe the thermodynamic properties of Li ⁺ adsorption in HTO.

Whereas the absorption speed are each experiment was performed by Li ⁺ adsorption of the sample as measured by (q _t) (equation (2)) according to an attraction time period (t), before equilibrium is achieved.

(2)

Result 1: Li ⁺  Effect of initial pH on adsorption

Lithium adsorption by HTO occurs by stoichiometric exchange between H ⁺ and Li ⁺ (Equation (3)) (G. He, L. Zhang, D. Zhou, Y. Zou, F. Wang et al. , Ionics 21: 2219-2226, 2015, L. Zhang, D. Zhou, G. He, F. Wang, J. Zhou et al., Mater. Lett . 135: 206-209, 2014).

(3)

The decreasing pH due to the accumulation of H ⁺ released in the batch system is related to the content of Li ⁺ adsorbed in the HTO. However, as the H ⁺ concentration increases, the reverse reaction of equation (3) is favored and Li ⁺ adsorption is inhibited.

This aspect was clearly confirmed by the pH of the solution which was initially changed during Li ⁺ adsorption. The straight line in Figure 4a represents the expected equilibrium pH of the system when Li ⁺ adsorption did not occur (initial pH = equilibrium pH). At initial pH = 4, a high concentration of H ⁺ in aqueous solution inhibited Li ⁺ adsorption in HTO (FIG. 4b). As the initial pH increased from 4 to 11, the q _e value also increased. The difference between the theoretical line and the experimental equilibrium pH means that the ^positive reaction of equation (3) is preferred and the Li ⁺ adsorption is improved.

On the other hand, the highest q _e at pH = 11 was theoretically located below the adsorption capacity of HTO (<5 mg g ^-1 ). This means that Li ⁺ adsorption is strongly inhibited by H ⁺ accumulation at such pH conditions. In addition, q _e increased (20 mg g ^-1 ) as the initial pH increased rapidly to 12, indicating that the inhibition of Li ⁺ adsorption was attenuated. It was confirmed that the buffer can be checked with a period that is similar to q _e values at (pH = 8 and 9) within the q _e values and the initial pH = 12, and a buffer system and adsorbed Li ⁺ without H ⁺ accumulation .

Result 2: Li ⁺  Effect of S / L ratio on adsorption

An alternative to reducing the H ⁺ accumulation effect without a relatively large change in the feed stream is to reduce the S / L ratio in the system. This can be done by increasing the feed solution volume at a fixed content of HTO. As shown in FIG. 5, q _e increases as the S / L ratio decreases. According to the aspect of q _e , two regions were identified: 1 region (S / L ratio = 0.48 - 6.66) affected by Li ⁺ adsorption by H ⁺ accumulation and 2 Area (S / L < 0.48). 1 area was divided into area A where the equilibrium pH value is the lowest and area B where the equilibrium pH value gradually increases with decreasing S / L ratio.

Zone A is where the q _e value of the HTO is adjusted according to the equilibrium pH. Under these conditions, Li ⁺ adsorption occurred until a critical pH of 4 was reached. This value is similar to the pH level at which no adsorption of Li ⁺ occurs in the pH test (FIG. 4). In addition, as the S / L ratio decreased from 6.66 to 1.11, the q _e value gradually increased from 1 to 12.8 mg g ^-1 as the solution volume increased. Zone B, on the other hand, is the conversion zone where the effect of H ⁺ concentration on q _e decreases as the S / L ratio decreases from 1.11 to 0.48. In Zone B, the equilibrium pH did not reach the critical level and q _e increased to 33 mg g ^-1 .

On the other hand, the q _e value did not improve even though the solution volume increased (S / L <0.48) in the two regions. This means that maximum Li ⁺ adsorption occurs at a specific C _o . On the other hand, the gradual increase in equilibrium pH with decreasing S / L ratio was confirmed by the dilution of H ⁺ released at high solution volume. Therefore, the adsorption of Li ⁺ at high solution volumes (ie very low S / L ratios) in the two regions is sufficiently canceled by inhibiting the H ⁺ accumulation effect.

Result 3: Li ⁺  Identify Adsorption Isotherm

In order to explain the adsorption mechanism of Li ⁺ in HTO, adsorption results without the effect of pH inhibition (S / L <0.48 in two regions) were applied to Langmuir model (equation (4)) and Freundlich model (equation (5) .

(4)

(5)

Where q _m is the maximum Li ⁺ adsorptivity of HTO, K _L is a Langmuir constant, and n and K _F indicate adsorption strength and adsorption capacity at unit concentration, respectively. Experimental results show that Langmuir type (FIG. 6a) has a higher correlation with Li ⁺ adsorption than Freundlich (FIG. 6b). The Langmuir isotherm can be represented by the equilibrium parameter ( R _L ) of equation (6) and the equation calculation result ( R _L = 0.024) and the Li ⁺ adsorption in HTO are advantageous (0> R _L > 1).

(6)

The Langmuir adsorption isotherm constants (Table 1) show q _m of 34.67 mg Li ⁺ g ^-1 HTO, similar to or higher than known literature (G. He, L. Zhang, D. Zhou, Y. Zou, F. Wang et al., Ionics 21: 2219-2226, 2015, L. Zhang, D. Zhou, G. He, F. Wang, J. Zhou et al., Mater. Lett . ).

Adsorption isotherm constant of HTO Langmuir Freundlich q _m (mg g ^-One ) K _L (L mg ^-One ) r ² n K _F (Lg ^-One ) r ² 34.67 0.59 0.99 34.14 29.92 0.63

pH = 11.02; m? 40 mg; C _o = 70 mg L ^-1 ; S / L ratio = 0.48 gL ^-1

Result 4: Li ⁺  Determination of thermodynamic energy change for adsorption

The change in Gibbs energy ( G ^? ), Enthalpy ( H ^? ) And entropy ( S ^? ) Was measured as the result of obtaining at various adsorption temperatures to confirm the energy change for Li ⁺ adsorption in HTO (Equation (7) And (8). To calculate G ^θ , a dimensionless standard equilibrium constant ( K ^o ), in which the density of K _d and HTO (ρ HTO = 2336.1 ± 0.0 kg m ^-3 ) was known (Equation (9)). The values of H ^θ and S ^θ were measured by the Van Hoff equation (equation (8)), where R is the ideal gas constant (8.314 JK ^-1 mol ^-1 ) and T is the Kelvin temperature. These thermodynamic parameters were measured to confirm the viability and spontaneity of HTO in the Li ⁺ adsorption process.

(7)

(8)

(9)

It was confirmed that the q _e value increases when the adsorption temperature rises from 30 캜 to 60 캜 (Fig. 7). In addition, it was confirmed that the adsorption driving force becomes larger as G ^θ has a negative value. The increase in the absolute value of G ^θ in Table 2 means that the higher the temperature, the more favorable the Li ⁺ adsorption is and the more thermodynamically q _e increases.

Thermodynamic parameters of Li ⁺ adsorption in HTO T (占 폚) G ^θ (kJ mol ^-One ) H ^θ (kJ mol ^-One ) S ^θ (Jmol ^-One K ^-One ) 30 -18.31 6.09 80 40 -19.10 - - 50 -19.93 - - 60 -20.72 - -

pH = 11.15; m? 40 mg; C _o = 70 mg L ^-1 ; S / L ratio = 0.48 gL ^-1

The Van Hope diagram shows the negative correlation ( r ² = 0.99) between temperature and ln K ^o inter-phase linearity, which implies an endothermic adsorption process with H ^θ = 6.09 kJ mol ^-1 . Prior to adsorption, Li ⁺ must be diffused into the HTO, which is an energy-demanding stage. In addition, it was confirmed that dehydration by HT ⁺ adsorption affects the endothermic effect of adsorption process. The spontaneity of endothermic Li ⁺ adsorption can be confirmed by the increase of the affinity of HTO to S ^θ (80 Jmol ^-1 K ^-1 ) and Li ⁺ depending on the mobility of Li ⁺ in solution with temperature.

Result 5: Li ⁺  Check adsorption rate

Li ⁺ adsorption dynamics in HTO were measured to estimate the adsorption rate of Li ⁺ , which establishes the residence time required to complete the adsorption process. The velocity data is important in providing the necessary information for designing batch reactors, fixed beds or other flow through systems.

As a result of the adsorption, the amount of Li ⁺ adsorbed during the first 9 hours was increased and the equilibrium was reached from 12 hours (FIG. 8).

To explain the total adsorption rate in HTO, Lagergren (equation (10)) and pseudo-secondary-velocity equation (equation (11)) were used, where k ₁ and k ₂ are the first and second order rate constants to be.

(10)

(11)

Comparing the two equations, it was confirmed that the pseudo-second-order equation more suitably describes the adsorption results (FIG. 9A). In addition, it was confirmed that the q _e value (36.68 mg g ^-1 ) and the experimental value ( q _e = 33.67 mg g ^-1 ) were very close to each other in the pseudo-secondary-velocity-spin echo equation (Table 3).

Li ⁺ adsorption rate parameter in HTO Models Derived constants r ² Shrinking core
(a) Film diffusion control K _f = 1.24 x 10 -4 cm s ^-1 0.97 (b) Solid diffusion control D _s = 3.45 x 10 ^-4 cm ² s ^-1 0.98 (c) Chemical reaction k ₃ = 1.42 x 10 ^-2 cm min ^-1 0.99 Lagergren
(pseudo-first order) q _e = 17.92 mg g &lt; ^-1 &gt;
k ₁ = 1.69 x 10 ^-3 min ^-1 0.82 Pseudo-second order q _e = 36.68 mg g &lt; ^-1 &gt;
k ₂ = 1.79 x 10 ^-4 g mg ^-1 min ^-1 0.99

pH = 11.15; m? 40 mg; C _o = 70 mg L ^-1 ; S / L ratio = 0.48 gL ^-1

On the other hand, the Lagergren model was found to be valid only at the beginning of the reaction; In the Lagergren model, the adsorption equilibrium was found to be significantly out of reach. This confirms that the pseudo-second-order equation model is suitable for describing the overall rate of HT ⁺ Li ⁺ adsorption process.

In addition, it can be assumed that the mechanism involved in Li ⁺ adsorption in HTO occurs in three successive steps: 1) external diffusion of Li ⁺ in aqueous solution or liquid film diffusion; 2) diffusion of Li ⁺ via HTO and 3) direct adsorption of Li ^{+ on} the active site or mass action of HTO. Here, a shrinking core model was used to illustrate each step (V. Inglezakis, S. Poulopoulos et al., Adsorption, Ion Exchange and Catalysis, Design of Operations, and Environmental applications, Elsevier , UK , 2006). This model assumes that the volume ( V _o ) or radius ( r _o ) of the spherical HTO is known. The unreacted volume ( V _u ) or radius ( r _u ) inside the HTO was estimated to shrink as the Li ⁺ fills the active site on the outer surface. The shrinkage rate of the film diffusion (equation 12), solid-state diffusion (equation 13) and the Li ⁺ and for the balanced performance of HTO to form the rate of the reaction (Equation 14) for the equivalent exchange of H ⁺ Is related to the fraction adsorption of Li ⁺ ( q _t / q _e = X _B ) (Equation (15)).

(12)

(13)

(14)

(15)

The transport coefficient of Li ⁺ through the liquid film ( k _f ) can be confirmed by the equation (13) at a given Li ⁺ molar density in HTO (ρ _B = q _m × ρ _HTO ; ρ _HTO = 2.34 g cm ^-3 ) , The dispersion coefficient ( D _s ) of Li ⁺ in HTO can be confirmed by the equation (14) and the rate constant k ₃ is confirmed by the equation (15). These constants can be found through the slope in the linear coordinates of the equation. The lithium concentration ( C _A ) in the aqueous solution increased with the adsorption time. In addition, the increase in lithium concentration can be performed using the time profile of C _A through Simpson's trapezoidal method (Fig. 9b) (V. Inglezakis, S. Poulopoulos et al., Adsorption, Ion Exchange and Catalysis, Design of Operations , and Environmental applications, Elsevier , UK, 2006).

Experimental results show high linearity in all models ( r ² > 0.97) and at each slope (Fig. 9c), liquid film transport of Li ⁺ ( k _f = 1.24 x 10 ^-4 cm s ^-1 ) (3.45 x 10 &lt; ^-10 &gt; cm &lt; ² &gt; s &lt; ^-1 &gt;).

In addition, the Biot number of the adsorption system was measured to determine which mechanism controlled the process. The Biot number ( B _n ) in equation (16) represents the ratio of the internal dispersion ( D _s ) to the external resistance ( k _f ) in the system and the particle diameter of HTO is given (d = 126-165 nm).

(16)

B _n provides a measure of the superiority of surface diffusion to external diffusion. Since the measured B _n (4.5-5.9) was between 1 and 100, both mechanisms were found to be essential for the Li ⁺ adsorption process by HTO (S. Baup, C. Jaffre, D. Wolbert, A. Laplanche et al., Adsorption 6: 219-228, 2000).

Experimental Example 2: Confirmation of reusability of HTO

The reusability of HTO was confirmed by repeated adsorption and desorption experiments (S / L = 0.48 gL ^-1 , C _o = 70 mg Li ⁺ L ^-1 , 30 ° C). After adsorption, the used HTO powder was collected via filtration and regenerated by acid treatment with 0.2 M HCl at 30 ° C for 24 hours. Meanwhile, the filtered liquid samples were collected for Li ⁺ analysis using ICP-MS. The regenerated HTO was thoroughly washed with deionized water, vacuum dried and then weighed again. To repeat the cycle, the HTO was redispersed in clean Li ⁺ solution (G. Nisola, L. Limjuco, E. Vivas, C. Lawagon, MJ Park, HK Shon, N. Mittal, IW Nah, H. Kim, WJ Chung et al., Chem. Eng, J. 280: 536-548, 2015). The reusability of HTO was determined by measuring q _e , physical, structural and chemical properties after several adsorption-desorption cycles at a suitable S / L ratio (~ 0.48). Desorption of Li ⁺ and regeneration of HTO were carried out using 0.2 M HCl (1 g L ^-1 ) as a leaching solution (R. Chitrakar, Y. Makita, K. Ooi, A. Sonoda et al., Dalton Trans . 43: 8933-8939, 2014).

As a result, it was confirmed that the repetitive acid leaching process did not affect the performance of HTO (FIG. 10A). The q _e values in all cycles showed a constant performance ranging from an average of ~ 33.6 mg Li ⁺ g ^-1 .

Experimental Example 3: Structural and Chemical Stability of HTO

The structural integrity of HTO was confirmed by the SEM image of the HTO powder used during the reusability test of HTO. The particle size distribution was obtained in the selected cycle and compared with HTO before use. On the other hand, the chemical stability of the adsorbent was confirmed by quantifying the eluted titanium (Ti ⁴⁺ ) after each desorption cycle. The acid solution used to regenerate the HTO powder was recovered and filtered before Ti ⁴⁺ analysis. Titanium was quantitated by a catalytic spectroscopic method (H. Mousavi, N. Pourreza et al., J. Chinese Chem. Soc . 55: 750-754, 2008). A sample (1 mL) containing Ti ⁴⁺ was added to a mixture of 2 mL of methylene blue (0.1 mM MB) and 1 mL of acetic acid buffer (pH = 4) and then 5 mL of deionized water was added. 1 ml of ascorbic acid (20 mM) was added thereto, and after 5 minutes of reaction, adsorption was measured at 665 nm. The discoloration of the solution by ascorbic acid was catalyzed by Ti ⁴⁺ and the adsorption reduction on the blank sample was proportional to the Ti ⁴⁺ concentration. Ti ⁴⁺ was quantified using a calibration curve of the absorbance reduction for a given Ti ⁴⁺ concentration.

In addition, in order to confirm the acid resistance of HTO, the amount of Ti ⁴⁺ eluted by the HCl solution was confirmed, and it was confirmed that the long-term adsorption performance of HTO was weakened due to the loss of many Ti ⁴⁺ . However, in Fig. 10B, the loss of Ti ⁴⁺ was high only in the first cycle, and it was confirmed that the loss amount rapidly decreased from the second cycle. The loss of Ti ⁴⁺ gradually decreased with the reuse of HTO (<0.5 wt%). Other forms of LIS, such as LMO, are less stable (~ 6 wt%) in Mn ²⁺ elution and less stable in acid solution (R. Chitrakar, Y. Makita, K. Ooi, A. Sonoda et al., Bull. Chem. Soc. Jpn . 86: 850-855, 2013), the chemical resistance of HTO is superior to that of LMO. In other experiments, the XRD pattern of HTO before use and HTO after use were similar (FIG. 11). Also, no structural change could be observed in the SEM image (Fig. 12). In addition, the decrease in the particle size of the HTO used could not be confirmed. As a result, it was confirmed that HTO is very stable when applied to adsorption reaction in the long term.

Experimental Example 4: Li of HTO in a seawater desalting concentrate ⁺  Confirmation of adsorption performance

Adsorption experiments on seawater desalination concentrates were conducted to confirm the effect of competitive ions such as Na ⁺ , K ⁺ , Ca ²⁺ and Mg ²⁺ on the Li ⁺ adsorption performance of HTO. Cation concentration was analyzed using ICP-MS. The Li ⁺ adsorption capacity of HTO was confirmed by q _e , and the selectivity for Li ⁺ was confirmed by the dispersion coefficient ( K _d ), separation factor (α _M ^Li ) and concentration factor (CF). The separation factor was measured by the ratio of K _d of Li ⁺ and the separation factor of other cations was present in the feed (Equations 17 - 19) (G. Nisola, L. Limjuco, E. Vivas, C , Law Won, MJ Park, HK Shon, N. Mittal, IW Nah, H. Kim, WJ Chung et al., Chem. Eng J 280: 536-548, 2015).

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Result 1: Li due to HTO ⁺ The number of times

The ability of HTO to selectively isolate diluted Li ⁺ in other cation-rich streams was confirmed (Table 4).

The Li ⁺ adsorption capacity of HTO in the presence of other cations in seawater Cations C _o (mg L ^-One ) C _o (mmol L ^-One ) C _e (mmol g ^-One ) Li ⁺ 15.4 2.2 1.1 ± 0.01 Na ⁺ 707.9 308 307 ± 0.11 Mg ²⁺ 83.7 34.5 34.3 ± 0.06 Ca ²⁺ 15.8 3.9 3.9 ± 0.00 K ⁺ 28.0 7.1 7.1 ± 0.01 q _e x10 ^-2 (mmol g ^-One ) K _d (mL g ^-One ) alpha _M ^Li CFx10 ^-3 (L g ^-One ) 115.6 ± 0.0 970.2 1.0 520.3 42.3 ± 0.0 1.3 705.3 1.3 10.0 0.0 2.9 333.2 2.9 0.9 ± 0.0 3.5 271.6 2.4 1.1 ± 0.0 1.6 604.1 1.6

As a result, HTO most selectively adsorbed Li ⁺ : the order of q _e of all the cations was as follows: Li ⁺ > Na ⁺ > Mg ²⁺ > K ⁺ > Ca ²⁺ (FIG. This means contributing to the ion-sieving effect of the HTO lattice. In addition, it was confirmed that HTO exhibits a high selectivity for Li ⁺ over other cations due to a rather high K _d value. Also, through the value of α _M ^Li , it was confirmed that HTO can efficiently separate Li ⁺ from other cations in several experiments. Also, at the appropriate S / L ratio (0.48), Li ⁺ was enriched to CF = 500 while other cations were increased by up to 3 times compared to the initial value. This confirms that HTO can effectively capture and separate diluted Li ⁺ from the same source as actual seawater containing other cations.

Result 2: Li ⁺ Confirm the recovery action of HTO on various resources including

The effect of HTO on various types of Li ⁺ sources was confirmed by measuring q _e values in the range of C _o = 0.7-7000 mg L ^-1 . A feed sample of pH = 8 was used to identify the general characteristics of the actual stream. The samples were buffered to reproduce the system under optimal conditions, and Li ⁺ adsorption was not inhibited by the decrease in pH due to H ⁺ accumulation.

As a result of experiments, it was confirmed that C _o and q _e increase as the Li ⁺ adsorption driving force increases (FIG. 14). Compared with the theoretical performance of HTO (122.2 mg g ^-1 ), the highest q _e was 94.5 mg g ^-1 at C _o = 7000 mg g ^-1 . Considering that only 75% of the adsorbed sites occupied by H ⁺ in HTO can be exchanged with Li ⁺ , the highest achievable q _e = 95.25 mg g ^-1 was confirmed. This means that at C _o ≥ 700 mg L ^-1 , 99% of the adsorption sites are occupied by Li ⁺ in HTO.

The Langmuir constant q _m = 94.78 mg g ^-1, which is expressed as the highest value for HTO adsorption performance, is obtained when (1) the adsorption system is performed under optimal conditions, (2) ) Could be obtained when used in a Li ⁺ rich feed stream (ie high C _o ). The low q _m values obtained in the S / L ratio experiment (Table 1) were confirmed to be due to the lower C _o (70 mg L ^-1 ) of Li ⁺ adsorption driving force than C _o = 7000 mg L ^-1 .

In addition, it was confirmed that the HTO performance of the present invention exceeds that of conventional LMO and HTO (FIG. 14).

At optimal conditions, HTO can be used to recover Li ⁺ from a diluted stream (ie, seawater, wastewater, etc.) and can provide q _e values up to 13 mg g ^-1 . It has also been shown that it can be used at high Li ⁺ level resources such as saline with a C _o as high as 7000 mg L ^-1 and q _e at 94.5 mg g ^-1 .

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (12)

delete delete delete delete delete delete delete delete delete (a) preparing an HTO lithium adsorbent comprising dispersing an LTO powder in an acidic solution;
(b) adsorbing lithium by adding the adsorbent prepared in step (a) to a solution containing lithium; And
(c) recovering lithium from the adsorbent on which lithium is adsorbed,
Wherein the step (b) is carried out under the condition that the S / L ratio, which is the volume ratio of the adsorbent (S) to the solution (L) containing lithium, is less than 0.48.
The method of claim 10,
Wherein the acidic solution comprises at least one selected from the group consisting of HCl, H ₂ SO ₄ , H ₂ PO ₄ and HNO ₃ .
The method of claim 10,
Wherein the solution containing lithium in step (b) comprises at least one selected from the group consisting of saline water, seawater, and industrial wastewater.

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