What Is Lithium Withdrawal?
Lithium extraction from seawater is a technology for extracting elemental lithium from seawater. The coexistence of elemental lithium with sodium and magnesium makes the extraction technology more difficult. Many countries are engaged in research on the technology of extracting lithium from seawater. At present, solvent extraction and adsorbent methods are mainly used in the research of seawater lithium extraction. Since the lithium concentration in seawater is only 0.17mg · L -1 , the method of extracting lithium from seawater with low lithium concentration is considered to be the most promising method for extracting lithium from seawater.
- Lithium has different chemical and physical properties from other metal elements and has a wide range of uses. At present, the annual consumption of lithium products in the world is about 300,000 tons, and it continues to grow at a rate of 7% to 11% per year. However, the total amount of terrestrial lithium resources identified worldwide is 13.76 million tons, which is far from meeting the long-term lithium market demand. The amount of lithium in seawater is huge, more than 10,000 times the total amount of lithium on land. Industrial developed countries such as Japan and the United States have been engaged in research on lithium extraction from seawater for many years, and have made certain progress: some domestic researchers have also engaged in research in this field. In order to avoid the recurrence of lithium lagging in salt lake brines in China in terms of lithium extraction from seawater, and to meet the strong demand for lithium in China and the world in the future, we should pay great attention to lithium extraction in seawater and start research in this field as soon as possible And continue to increase efforts.
- At present, solvent extraction and adsorbent methods are mainly used in the research of seawater lithium extraction. As the lithium concentration in seawater is only 0.17mg · L -1 , so the method of extracting lithium from seawater with low lithium concentration is considered to be the most promising method for lithium extraction from seawater [1]
- At present, the research on lithium extractants and extraction systems has mainly focused on four aspects: alcohols and ketones, alkyl phosphines and phosphonates, mixed ion extractants, and crown ethers, among which crown ethers Most concerned. Crown ethers combine electrostatic forces with anions that match the radius of the ions and the cavity, which can cause huge differences in the stability constants of cation complexes of different radii. Due to the different pore sizes of various crown ethers, the ions that can be accommodated are selective. Crown ether extractants with strong selectivity to lithium are mainly carboxylic crown ethers and crown ether phosphonic acid lipids. The most suitable crown ether ring is 14 crown4. From the perspective of the actual lithium extraction process, the solvent extraction method is suitable for aqueous solutions with high lithium concentration. The concentration of lithium in seawater is very low, which needs to be concentrated and takes time and effort, so it is not suitable for large-scale industrial development.
- The adsorption-ion exchange method has a simple process, high recovery rate, and good selectivity. It is particularly suitable for the extraction of lithium from low-grade seawater. It is considered to be the most promising seawater lithium extraction method. The key to this method is to find the right sorbent. Adsorbents can be divided into organic adsorbents and inorganic adsorbents. Organic adsorbents have low selectivity for lithium and should not be used. Inorganic adsorbents have high selectivity for lithium, especially those with specific memory effects. Ion sieve adsorbent, especially effective for this method [2]