| This paper studies the technology and theory of preparing of ion sieve from ocean polymetallic nodule and lithium hydroxide, and recovering of lithium by the ion sieve from complex lithium-low solution systemFirst, the studying achievement is summarized about ocean polymetallic nodule, such as formative mechanism, ore phase and application situation. At the same time, it is introduced such as development situation of lithium resource, technology of recovering lithium from Brine Lake and other unsolved-problems. After that, the research background is lodged. For the peculiar feature of ocean polymetallic nodule, it is suitable to prepare ion sieve and to recovery of lithium directly from complex lithium-low solution, which can fulfill coexploiting of ocean solid resource and brine lake resource. That has great signification for supplying a new view for resource security strategy.The paper is divided into five departments, and they are element morpha, preparing precursore, thermodynamic behaviour of elements, mechanism of forming precursore, extraction lithium from precursore and lithium absorbed by ion sieve respectively.Element morpha in ocean polymetallic nodule:By XRD, SEM, EDS, microscope and chemical extraction, the element morpha is obtained such as Mn, Fe, Cu, Co and Ni. Those elements are mainly concentrated in intermediate layer and crust layer. (1) There are four kinds of manganese compounds, which are?-MnO2, manganese-high hydrate, manganese-iron hydrate (about 10% Fe) and impurity of manganese-iron hydrate (more than 15% Fe). Most iron is at the form of amorphous goethite. About 30% iron is dip-dyed in manganese hydrate and its distribution is not average. The manganese-high hydrate is always concentrated in crust layer and impurity of manganese-iron hydrate is concentrated in intermediate layer. (3) The elements such as Cu, Co and Ni are in the form of isomorphism or colloid. Most Cu has relation with Mn, few with iron and clay,10%-20% Cu is in the form of absorption and has not relation with Mn and Fe. The element Co is mainly distributed in impurity of manganese-iron hydrate, and few Co is dip-dyed in goethite and has utter relation with iron. Almost all of Ni is enriched in manganese hydrate and has relation with manganese. (4) The element distribution feature shows that the preparing ion sieve has nature adulterated performance.Formation of precursor:(1) From the reaction between polymetallic nodule and different lithium compose and the result characterized by TG-DTG-DSC, it is shown that lithium hydroxide is suitable for preparing ion sieve. (2) By XRD technology and X Pert HighScore software, the factors is studied such as temperature, time, ratio of lithium-manganese and calefactive velocity. The suitable roasting condition is that temperature 600?700?, time 6?10 h, calefactive velocity 5?10?/min and ratio of lithium-manganese 0.5?0.8. (3) Characterized by SEM, the surface of precursor is irregular and reveals aggregate structure, and its granularity is 50?150?m. Characterized by TEM, the precursor is cubic spinel crystal, ans its cell dimension is 100?200nm. Characterized by XPS, lithium manganese spinel is also formed, and iron element enters crystal lattice.Thermodynamic of elements and mechanism of preparing precursor:(1) By thermodynamic analysis, it is possible to form the composite oxides such as MnFe2O4?CoFe2O4?NiFe2O4 and CuFe2O4. (2) The oxygen potential graph is drawn. The forming order of composite oxides is CoFe2O4?NiFe2O4?CuFe2O4?MnFe2O4 from 0?to 413?, CoFe2O4?NiFe2O4?MnFe2O4?CuFe2O4 from 413?to 520?and CoFe2O4?MnFe2O4?NiFe2O4?CuFe2O4 above 520?. (3) The mechanism of forming precursor is that when temperature is below 413?, the elements in polymetallic nodule will form composite oxides. When temperature increases to 520?, lithium hydroxide becomes liquid, gets into composite oxide cells and forms precursor.Extraction lithium from precursor:(1) The property of LiCl-HCl-H2O system is analyzed. The Eh-pH graph is drawn at 298K. The thermodynamic analysis shows that it is possible for lithium extraction. (2) The effects on the extractive lithium and resolutive manganese are examined respectively from the technological angle, such as lithium-to-manganese ratio, time, temperature, acid concentration, particle size, liquid-to-solid ratio and agitation rate. The reasonable technological condition is that time 210 min, temperature 60?, acid concentration 1.0 mol/L, particle size -400 mesh, liquid-to-solid ratio 50:1, lithium-to-manganese ratio 0.7 and agitation rate 350r/min. Under this condition, the extractive rate of lithium is up to 82.9% and the rate of resolutive manganese is equal to 5.7%. By XRD characterizing, after lithium extraction, the ion sieve still shows spinel structure, but the cell becomes small. (3) The kinetics of extractive lithium is studied and the result shows that extractive lithium process is controlled by ion diffusion and follows the "zone leaching model". The reaction activation energy is 40.3 kJ/mol. The apparent reaction order is 0.758. The kinetic mathematical model for extractive lithium process isAdsorption lithium by ion sieve:(1) The effects of time, initial lithium concentration, pH value, temperature, particle size and liquid-to-solid ratio on the lithium ion adsorbing are examined from the technological aspect. The reasonable technological conditions obtained by experiment are:room temperature, time 240 min, pH value 8.0, particle size -300 mesh, liquid-to-solid ratio 100:1. At those experiment conditions, the capacity of adsorbed lithium is up to 10.5 mg/g, and the percentage of dissolved manganese is below 0.02%. (2) The pH titration curve shows that H+ will enter the cell of ion sieve in acid washing process, and then is exchanged by Li+ in adsorption process. The static saturation adsorptive capacity is equal to 15.8 mg/g, and the dynamic saturation adsorptive capacity is equal to 17.8 mg/g. (3) The isothermal adsorption curve is similar with L2, and can be described by Langmuir equation and Freundlich equation. Calculating by Langmuir equation, the saturation adsorptive capacity is 11.4 mg/g, which is very closed to the experiment value. The?G of adsorbing process is equal to -1.08 kJ/mol, which indicates that the adsorbing process can start automatically. (4) In dynamic aspect, the adsorbing lithium process is fitted for quasi-second dynamics equation and belongs to chemical adsorption. The theory adsorption capacities are 11.2 mg/g,13.3 mg/g and 14.6 mg/g respectively at 21?,40?and 50?, which are very closed to experiment values. The activation energy is 6.92 kJ/mol. (5) The ion sieve prepared has good reusing performance. The capacity of lithium adsorbed is up to 90.1 mg/g in 15 recursions, and 200 mg/g in 30 recursions. (6) The ion sieve has great selectivity for Li+ in complex lithium-low solution system. The order of ion distribution coefficient fellows Li+>>Ca2+>Na+> Sr+> Rb+> B2+>K+>Mg2+, and it is suitable to recovery of lithium from complex solution system. (7) By XRD characterizing, after lithium adsorbed, the ion sieve still shows spinel structure, which shows the Li+ enters the lattice of manganese ores. Characterized by SEM, the surface of ion sieve is still aggregate structure. Characterized by TEM, the interplanar crystal spacing is equal to 4.69 A, which fits with the crystal spacing of first diffraction peak in XRD diagram. That is the reusing base of ion sieve. |
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