| , known as the best lithium adsorbent because of the best adsorption property among the manganese base lithium ionic sieve. It was obtained by pickling the spinel Li1.6Mn1.6O4. It was studied that a new synthesis method of lithium manganese oxide Li1.6Mn1.6O4in this thesis. The preparation technology of adsorbent MnO2·0.5H2O and the adsorption property to Li+were also studied.The preparation technology of MnO2·0.5H2O had been optimized: the Mn2O3was obtained by roasting electrolytic manganese dioxide at680℃, then a pure Li1.6Mn1.6O4was prepared by calcinating orthorhombic LiMnO2at410℃for4h, which was synthesized by using a hydrothermal reaction using with LiOH and Mn2O3as the selected starting reagents at210℃for10h. After the Li1.6Mn1.6O4had been leached with diluted hydrochloric acid, an ion-sieve for lithium (MnO2·0.5H2O) was obtained.The ratio of extracted lithium is above90%and the loss ratio of dissolved Mn is under2.5%in the pickling process. The results show that the adsorption capacity of Li ion increases with the increasing of the temperature and the pH of the solution. The maximum uptake of lithium from brine was27.15mg/g at50℃. The adsorption rate of lithium from brine was over99%under certain conditions in brine. The adsorption and desorption capacity were still more than21mg/g after10cycles. There was a remarkable effect for seperation between Li+and other ions in the brine, such as Mg2+、K+、Na+etc. The seperation coefficient was above50, which showed that this adsorbent had a great selectivity to Li+. Physical and chemical analysis showed that the prepared adsorbent had a great chemical and structural stability. The mechanisms of adsorption and desorption were ion-exchange reaction.To adapt to the industry practice, the synthesis and properties of porous granular adsorbent had been studied:a porous granular adsorbent was prepared using poly-(vinyl chloride) as a binder, which was mixed and kneaded sufficiently with Li1.6Mn1.6O4, porous agent KC1, surfactant and organic solvent N, N-dimethylformamide. A certain size of granule was obtained after spreading, drying and shearing, and then it was treated with a diluted HCl solution to obtain the porous granular adsorbent. The experimental results showed that the pickling reaction reached balance after2hours’leaching, the ratio of extracted Li was above85%, and the adsorption capacity of the granular adsorbent reduced, compared with the powdery adsorbent.Pore structure and specific surface analysing and batch tests showed that the high adsorption capacity were based on the pores which had the good wettability with brine. The adsorption capacity of granular adsobent which had be wetted by water increased with the contact time, stirring speed and diluted times increasing, the adsorption capacity was15.90mg/g at30℃for10h. The adsorption capacity could be at26.27mg/g when the brine was diluted about1.5times, at which time the surface tension, density and viscosity of brine were reduced sharply. The adsorption capacity was still above12.50mg/g after14cycles, the capacity reduced few. The studies of adsorption dynamics and isotherm showed that the adsorption process in brine were so complexity that they were cannot be simulated by any single theoretical model.Dynamic adsorption was studied, the results from the continuous pillar operation showed that the breakthrough capacity, adsorption speed and utilization ratio of granular adsorbent increased with a more slow flow rate and a more dulite brine, and a later breakthrough point appeared. Most of the foreign ions were washed out after water washing, and little enter into the stripping liquid. The desorption process reacted quickly, and almost all the lithium were desorbed. A highly pure LiCl solution was obtained. The purpose of seperating and riching lithium from brine had been achieved. |
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