Extraction kinetics of lithium ions by N,N-bis(2-ethylhexyl)acetamide from simulated brine using rising single drop method

doi:10.1016/j.hydromet.2015.11.002

Hydrometallurgy

Volume 160, March 2016, Pages 1-5

https://doi.org/10.1016/j.hydromet.2015.11.002 Get rights and content

Highlights

•
The extraction kinetics of lithium by N523 from salt lake brine was investigated by rising single drop method.
•
The extraction process is controlled by the diffusion.
•
The chemical reaction takes place at the interfacial area.
•
The mechanism of the lithium extraction with N523 is revealed.

Abstract

Recovery of lithium ions from salt lake brine is becoming more important because of the rapid increase in projected demand for lithium resources. N,N-bis(2-ethylhexyl)acetamide (N523) is a newly developed extractant that presents good lithium extraction ability and selectivity. In this study, the kinetics and mechanism of lithium ion extraction with N523 in kerosene at 298.15 K were investigated using the rising single drop method. Results showed that the extraction process is controlled by diffusion and that the chemical reaction occurs at the interfacial area.

Introduction

Lithium is a crucial resource that is used in batteries, medicines, light aircraft alloys, and thermonuclear fusion reactors (Lemaire et al., 2014, David et al., 2014, Lin et al., 2014, Pratima and Pandey, 2014, Somrani et al., 2013). The demand for lithium resources is estimated to rapidly increase in the near future. Therefore, substantial efforts have been given to the development of lithium recovery technologies from various sources, such as seawater, ore, and salt lake (Sun et al., 2014, James and Palmer, 2000). Among the developed methodologies for lithium recovery, solvent extraction from salt lake brine has attracted considerable interest because more than 80% of lithium resources in China are present in the form of salt lake brine (Sun et al., 2011), which has a high Mg/Li ratio (Zhao et al., 2013).

Extractants with high selectivity toward lithium ions in salt lake brine has been investigated, including several new substances such as 2,6-Dimethyl-4-heptanone (DIBK) (Neilli et al., 1970), N,N-bis(1-methyl heptyl)acetamide (N503) (Xu, 1979), and butyl acetate (BA) (Li et al., 2014), which are considered to be promising lithium-selective extractants. A new extractant, N,N-bis(2-ethylhexyl)acetamide (N523), has been recently proposed. To separate lithium and magnesium effectively from salt lake brine and to increase the extraction rate of lithium, we built a N523-sulfonated kerosene extraction system (Li et al., 2014, Shi et al., 2013). By using this system, the rate of extracting lithium from salt lake brine can exceed 96% (Shi et al., 2013). Moreover, the impurity content is extremely low in the strip liquor (Shi et al., 2013). However, regardless of the applied extractant, the chemical reaction scheme, mechanism, and mass-transfer models in the extraction process should be studied (Tokerman et al., 2014, Xiong et al., 2010).

The kinetics of metal extraction is complicated because both chemical reaction and diffusion are involved in a heterogeneous system. However, elucidation of the kinetic behavior of an extraction system is important because of their influence on economic parameters, such as equipment model, and extraction reaction temperature and residence time. Hence, several techniques to study the kinetics of metal extraction have been developed over the years, including Lewis cell (Yang et al., 2013, Xiong et al., 2006), rotating diffusion cell (Meng et al., 1996), stirred tank AKUFVE, Kenics mixer (Horner et al., 1980), and the single drop technique (Biswas and Hayat, 2002, Wang et al., 2010). Among the available techniques, the reliable and simple rising single drop method (Zhou et al., 1983, Gai et al., 1986) is considered a promising method.

In the present work, lithium extraction kinetics by N523-sulfonated kerosene extraction system was studied using the rising single drop method. The effects of different parameters, such as interfacial area, column height, temperature, and concentrations of Fe^3 +, Li⁺, and N523 on the kinetics of extraction were investigated. A mechanism was proposed to explain the obtained results.

Section snippets

Materials and conditions

The new extractant, N523, was prepared by Shanghai Institute of Organic Chemistry of the Chinese Academy of Sciences. The structure of N523 is shown in Fig. 1. Sulfonated kerosene was bought from a local market. (Its density is 0.81 g/cm³, the flash point is below 60 °C and the percent aromatic is below 10%.) All other chemicals were of analytical reagent grade.

A stock solution of the aqueous phase containing 3.50 mol/L MgCl₂, 0.05 mol/L HCl, and 1.40 mol/L LiCl was prepared by mixing appropriate

Effect of interfacial area on extraction kinetics

In the kinetic study, the effect of interfacial area on extraction rate can be treated as one of the most important criteria in determining the chemical reaction occurring in the bulk phase or at the interface. If the reaction occurred in the bulk phase, then the initial rate would be independent of interfacial area; otherwise, the rate would depend on interfacial area (Wang et al., 2013).

The effect of interfacial area on the extraction rate of lithium was investigated. As shown in Fig. 3, the

Conclusion

The kinetics and mechanism for the extraction of lithium from salt lake brine with N523 in kerosene was investigated at 298.15 K by using single rising drop method. On the basis of the results, the following conclusions can be drawn:

(1)
The extraction process is controlled by diffusion, and the chemical reaction occurs at the interfacial area.
(2)
The mechanism of lithium extraction with N523 can be treated as follows: the species Mg(FeCl₄)₂ ⋅ nN523 in the loaded organic phase separates into Mg^2 +, FeCl₄⁻,

Acknowledgment

This work was financially supported by the Qinghai Province Department of Finance Project (2011-G-206A) and the CAS Key Deployment Project, “Number of Strategic Elements Extracted from Salt Lake” (KGZD_EW_604). The authors are grateful for the Shanghai Institute of Organic Chemistry for glassware preparation.

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View full text

Extraction kinetics of lithium ions by N,N-bis(2-ethylhexyl)acetamide from simulated brine using rising single drop method

Highlights

Abstract

Introduction

Section snippets

Materials and conditions

Effect of interfacial area on extraction kinetics

Conclusion

Acknowledgment

Hydrometallurgy

Chem. Geol.

Hydrometallurgy

Hydrometallurgy

Desalination

Sep. Purif. Technol.

Hydrometallurgy

J. Inorg. Nucl. Chem.

Hydrometallurgy

Hydrometallurgy

Hydrometallurgy

Hydrometallurgy

Phase field kinetics of lithium electrodeposits

J. Power Sources