| In this paper, the preparation process of magnetic materials CoNi ferrites with good quality was investigated, in which spent Li-ion batteries and spent nickel metal hydride batteries are used as raw materials. This study is carried out according to the chemical reaction and magnetic theory, using the spectrum method and micro technique, and utilizing the knowledge of chemical technology, chemical reaction engineering, structural chemistry, chemical thermodynamics and environmental engineering. We studied the optimum dissolution conditions of spent Li-ion batteries and spent nickel metal hydride batteries. Meanwhile we discussed the effects of technical parameters on the microstructure and magnetic properties of the product via different methods such as sol-gel method, hydrothermal method and microwave hydrothermal method. Thus, we chose the optimal technical route and technical parameters of preparing CoNi ferrites from spent Li-ion batteries and spent nickel metal hydride batteries. all the studies were characterized by technique of TG/DSC, XRD, IR, SEM, TEM and VSM. On the other hand, the comparative research of three methods is done with crystallinity, micro morphology and magnetic property, and the relationship between microstructure and magnetic property are primarily discussed. The results are shown as below:1. The optimum dissolution conditions of spent Li-ion batteries in sulfuric acids are as follows: the initial concentration of sulfuric acid with 3 mol/l, the sulfuric acid/sample ratio with 13, the dissolution temperature with 65℃ and the initial concentration of H2O2 with 3.5wt%, The sequence according to the effect of the extraction results is as follows:The initial concentration of H2O2 > the initial concentration of sulfuric acid > the dissolution temperature > the sulfuric acid/sample ratio. The addition of H2O2 was used as oxidizing agent to the solution can make the dissolution ratio of spent nickel metal hydride batteries in sulfuric acids increase.The optimum dissolution conditions of spent nickel metal hydride batteries in sulfuric acids are as follows: the initial concentration of sulfuric acid with 2.5 mol/l, the sulfuric acid/sample ratio with 11, the dissolution temperature with 65℃ and the initial concentration of H2O2 with 3wt%, The sequence according to the effect of the extraction results is as follows:The initial concentration of H2O2 > the dissolution temperature > the initial concentration of sulfuric acid > the sulfuric acid/sample ratio.2. Spent Li-ion batteries and nickel metal hydride were used as source materials to prepare nanoparticles of CoNi ferrite with spinel structure by hydrothermal method. The optimum preparing conditions are as follows: pH value with 11, hydrothermal temperature with 160℃, and the hydrothermal time with 6h. The particle size of CoNi ferrite with optimum preparing conditions is about 50 nm. The magnetic properties of CoNi ferrite with optimum preparing conditions are: saturation magnetization Ms=54.037emu/g, remanent magnetization Mr=19.402 emu/g, coercive force Hc=1055.8 G.3. Spent Li-ion batteries and nickel metal hydride were used as source materials to prepare nanoparticles of CoNi ferrite with spinel structure by sol gel method using citric acid as gelata. The results showed that the optimum preparing conditions are as follows: citric acid/metals ratio with 1.0:1.0(mol); pH value with 7.0; the sintering temperature with 650℃ and the sintering time with 2h. The particle size increases with raising sintering temperature and prolonging sintering time. The values of Ms, Mr and Hcincrease with increasing nanoparticle size. Spent Li-ion batteries and nickel metal hydride were used as source materials to prepare nanoparticles of CoNi ferrite with spinel structure by sol gel method using tartaric acid as gelata. The results showed that the optimum preparing conditions are as follows: citric acid/metals ratio with 1.2:1.0(mol); pH value with 5.5; the sintering temperature with 650℃ and the sintering time with 2h. The magnetic properties of CoNi ferrite by sol gel method with optimum preparing conditions are: saturation magnetization Ms=54.037emu/g, remanent magnetization Mr=19.402, coercive force Hc=1055.8 G. Tartaric acid is better than citric acid when they are used as gelata for getting pure phase CoNi ferrite with good crystallinity and slightly agglomerated. The mechanism of preparation CoNi ferrite from calcining the dried gels and the mechanism of the calcining temperature affecting CoNi ferrite were studied; the reasons of the magnetic properties of CoNi ferrite were superior to the traditional magnetic material Co ferrite.4. Spent Li-ion batteries and nickel metal hydride were used as source materials to prepare nanoparticles of CoNi ferrite with spinel structure by microwave hydrothermal method. The optimum preparing conditions are as follows: pH value with 10, microwave hydrothermal temperature with 120℃, and the microwave hydrothermal time with 1.5h. The magnetic properties of CoNi ferrite with optimum preparing conditions are: saturation magnetization Ms=67.134 emu/g, remanent magnetization Mr=16.305 emu/g, coercive force Hc=681.80 G.5. The comparative research of hydrothermal method, sol-gel method and microwave hydrothermal method is done with crystallinity, micro morphology and magnetic property.The X-ray diffraction peak of CoNi ferrite by sol-gel method is strongest, crystallinity is best, and particle size is biggest. The products by sol-gel method are severely agglomerated, because of the high temperature calcination. The saturation magnetization of CoNi ferrite by sol-gel method is lowest, but the remanent magnetization and coercive force are highest. The products by microwave hydrothermal method have the smallest particle size, the best magnetic property, the highest saturation magnetization, but the lowest remanent magnetization and coercive force. CoNi ferrite prepared through hydrothermal process is more suitable to the industrialization production of recycling spent Li-ion batteries and nickel metal hydride batteries.The innovations of this study are as follows: the recycling batteries are combining the spent Li-ion batteries and spent nickel metal hydride batteries, the recycling products are no longer simple metals or their oxides, but magnetic materials with high potential economy value—CoNi ferrite, this method omitted sophisticated separating process, the technology is more simple, and the cost of the production can be reduced by a large scale; The mechanisms of preparation CoNi ferrite from calcining the dried gels and the calcining temperature affecting the magnetic properties of CoNi ferrite were studied, the relationship between particle size and magnetic properties was found.This dissertation not only provides basic data for the industrial production of recycling spent Li-ion batteries and nickel metal hydride batteries, but also explores a new way for the recycling of other batteries. The study is of deep theoretical significance and good application foreground. It is very important for environmental protection, and is believed to bring both economic and social benefits to us. |
PDF Full Text Request