Papers by Author: Kang Sup Chung

Abstract: Ion-sieve type manganese oxide spinels for the selective adsorption of lithium(Li) from seawater were prepared and their properties were examined. LiM0.5Mn1.5O4 (M=Mg, Zn) precursors, in which part of manganese(Mn) was substituted with magnesium(Mg) or zinc(Zn), were synthesized through the solid-state reaction. The adsorbents, HM0.5Mn1.5O4 (M=Mg, Zn) were derived from LiM0.5Mn1.5O4 (M=Mg, Zn) by acid treatment. The optimum acid treatment was obtained at hydrochloric acid concentration of 0.5M and 0.3M for LiMg0.5Mn1.5O4 and LiZn0.5Mn1.5O4 precursors, respectively. Both cases required thrice-conducted acid treatments for the best results. The adsorption of Li by HMg0.5Mn1.5O4 and HZn0.5Mn1.5O4 adsorbents followed the Freundlich equation and the maximum adsorption of Li in artificial seawater was 30.3 mg/g and 33.1 mg/g, respectively. The adsorption efficiency of Li by HMg0.5Mn1.5O4 and HZn0.5Mn1.5O4 adsorbents in artificial seawater, in which Li concentration was adjusted to 0.2 mg/L, was as high as 88% and 89%.

Abstract: A direct analytical technique was developed and tested for correct estimation of recovery of Eco-elements such as Li, B, Br, in the seawater, and three processed seawaters from Hanjoo Co. Ltd. The reliability of recovery technique and the correct estimation of total recoveries become a major interest before the launch of pilot plant. High matrix solutions are frequently affected in analyte response during instrumental analysis as the concentration of major component changed drastically. To overcome such a complication during standard sample preparation and a better application in pilot plant, a modified matrix matching standard addition method was developed and the reliability was checked. The detection limit of elements in several seawaters analyzed by applying the modified matrix matching standard addition method were 0.144 – 0.258-g/dm3 for lithium, 0.0.013 – 0.18mg/dm3 for boron, and 4.23 – 17.8mg/dm3 for bromine. The instrumental analysis was carried by AAS for lithium and ICP-AES for boron and bromine.

Abstract: Adsorbing and salvaging extremely small quantities of lithium ion, high-performance ion-exchange type lithium ion adsorbent was prepared through the ion-sieve formation method. The method uses acid treatment after the synthesis of spinel-structured nano-Li_1.33Mn_1.67O₄ precursor through the tartaric acid gel process. It has good selectivity and high efficiency in adsorbing lithium ion in seawater. The generated adsorbent showed a 28.2 mg/g lithium uptake from artificial seawater. This adsorbent further showed a difference reproducibility that was lower than 10% when subjected to five cycles of adsorption and desorption experiments.