以三元锂电池回收的末端废渣为原料制备的高效核壳结构催化剂 性能及机理研究
Performance and mechanism of a core-shell catalyst prepared from the end waste of recycled ternary lithium battery
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摘要: 摘要: 随着新能源汽车的推广和普及,锂离子电池的装机量呈爆发式增长,随之而来的是大量锂电池的报废并亟待回收处理。已有锂电池回收技术提取锂、镍、钴、锰等金属后的末端废渣仍残留有一定量的过渡金属,若不加以处理处置直接丢弃到环境中会造成重金属的环境污染风险。本研究提出了一种以锂电池回收的末端废渣与三聚氰胺固体粉末混合后热解制备具有核壳结构的高性能催化剂,用于催化过硫酸盐氧化剂氧化去除有机污染物,实现其高值化再利用。对制备的催化剂和原始末端废渣均进行详细地表征,确认了新制备的催化剂具有明显的核壳结构,核为镍钴氮化物和锰氧化物,壳为厚度约为5.7-13.1 nm的石墨化碳层。以单过硫酸盐为氧化剂,对新制备的催化剂的催化性能进行了测试,发现其可高效催化单过硫酸盐降解包括苯甲酸、硝基苯、苯酚等一系列难降解有机污染物,且受环境条件的影响较纯自由基体系小。循环实验的结果表明,该材料可实现多次循环利用且催化效率基本保持稳定。对降解完成后体系中的金属离子进行测定后发现,新制备的催化剂在催化降解过程中,金属离子仅有微量溶出,而原始废渣则大量溶出金属离子,说明经三聚氰胺混合热解可有效固定废渣中的金属。此外,经淬灭实验,D2O替换和EPR测试等一系列实验,证明新催化剂催化单过硫酸盐降解有机污染物体系中硫酸根自由基和单线态氧均具有一定贡献,但还存在其他未被探明的机理Abstract: With the promotion and popularization of new energy vehicles, the installed amounts of lithium-ion batteries have exploded, followed by a large number of lithium batteries scrapped and urgently need to be recycled. There is a certain amount of transition metals in the residue after extracting lithium, nickel, cobalt, and manganese. If these residues are disposed directly into the environment without treatment, it would cause serious environmental pollution. In this study, a kind of catalyst (NCM1) with core-shell structure was prepared by mixing the residue with melamine. Both NCM1 and the original residue were fully characterized. It was confirmed that NCM1 has an obvious core-shell structure, with the core consisting of nickel-cobalt nitrite and manganese oxide, and the shell consisting of a graphitized carbon layer with a thickness of about 5.7-13.1 nm. Using peroxymonosulfate as oxidant, the catalytic performance of NCM1 was tested. It was found that NCM1 can efficiently catalyze PMS to degrade a series of organic pollutants, including benzoic acid, nitrobenzene, phenol, etc., and was slightly affected by environmental conditions than traditional free radical degradation system. Results of cyclic experiments show that NCM1 can be recycled several times with stable catalytic efficiency. Minor metal ions were dissolved after the degradation in NCM1/PMS system while a large amount of metal ions were dissolved in the original residue/PMS system, indicating that the metal ions in the residue can be effectively fixed through the mixed pyrolysis with melamine. Additionally, a series of experiments including quenching experiments, D2O replacement and EPR test proved that sulfate radical and singlet oxygen made contribution to the degradation of pollutants in the system of NCM1/PMS, but there still are unexplored mechanisms.
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Key words:
- Lithium battery recycling /
- core-shell catalyst /
- peroxymonosulfate
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