关键词: 离子筛, 造粒, 交联, 吸附, 粉体, 颗粒过程

Abstract: Spherical Li₄Mn₅O₁₂ ion-sieve precusor with particle diameter about 2—3 mm was prepared with the Li₄Mn₅O₁₂ ultrafine powder synthesized by the authors' lab and the agarose granulation process. Agarose was dissolved in deionized water at 90℃. The Li₄Mn₅O₁₂ ultrafine powder was added to agarose solution and mixed uniformly. Then the mixture was dropped into cold liquid paraffin. Spherical adsorbents were obtained at the bottom of the reactor, which were filtered and cleaned by ethyl acetate, ethanol and deioned water separately. The particles were cross-linked with epichlorohydrin, and then treated with 1 mol·L^-1 HCl to obtain the spherical ion-sieve. The effects of concentration of agarose, granulation temperature, concentration of cross-link agent, and cross-link time were studied. It was found that 5% agarose solution, 90℃, epichlorohydrin concentration of 2 ml·g^-1, and cross-link time of 6 h were the best condition to prepare the spherical ion-sieve. The lithium ion adsorption capacity of the spherical ion-sieve can reach 4.25 mmol·g^-1, which is 75.6% of that of lithium ion sieve powder. The adsorption rate of the spherical ion-sieve is 1.77×10^-5 s^-1, decreasing one order magnitude compared with that of the powder (3.29×10^-4 s^-1). The equilibrium lithium adsorption capacity increases apparently with pH value, reaching 5.5 mmol·g^-1 at pH 12. The selectivity experiment shows that the prepared lithium ion-sieve presents a highly selectivity for lithium ions. The results show that the spherical ion-sieve is an attractive adsorbent for lithium extraction from brine or seawater.

Key words: ion sieve, granulation, cross-link, adsorption, powders, particulate processes