失效动力锂离子电池再利用和有用金属回收技术研究

动力锂离子电池以其贮电能力大、充放电速度快等优点被广泛应用在电动汽车上,近年来失效电动汽车动力锂离子电池报废量不断增加,但未得到有效处理回收,造成了巨大的资源浪费和环境污染.失效电池还有80％左右的容量可以使用,可以在场地车或者储能电站进行再利用,以达到材料和电池的最大利用率;同时电池中含有多种有用金属（如Co,Al,Ni,Li等）且相对含量较高,极具回收价值.针对失效动力锂离子电池的再利用和有用金属的各种回收方法进行了评述.     

黄钠铁矾法氧化去除废锂电池硫酸浸出液中的铁

废锂电池中含有的Co、Ni和Cu等金属具有回收价值,Fe的存在降低了有价金属的回收效率。为去除废锂电池硫酸浸出液中的Fe,采用黄钠铁矾法分别以氯酸钠和过氧化氢作为氧化剂氧化除Fe,并优化了过氧化氢作为氧化剂的除Fe工艺参数。实验结果表明:过氧化氢作为氧化剂的除Fe效果好于氯酸钠;在n(H2O2)∶n(Fe)=0.5、初始溶液pH为1.8、终点pH为2.5、反应时间为2.0 h、搅拌速率为500 r/min的最佳工艺条件下,初始ρ(Fe)为0.212g/L的硫酸浸出液经除Fe处理后ρ(Fe)小于0.004 g/L,Fe去除率达98.0%,Co、Ni和Cu的损失率分别为1.04%、2.17%和1.41%。     

Single-phase and two-phase anaerobic digestion of fruit and vegetable waste: Comparison of start-up,reactor stability and process performance

Single-phase and two-phase digestion of fruit and vegetable waste were studied to compare reactor start-up, reactor stability and performance (methane yield, volatile solids reduction and energy yield). The single-phase reactor (SPR) was a conventional reactor operated at a low loading rate (maximum of 3.5 kg VS/m³ d), while the two-phase system consisted of an acidification reactor (TPAR) and a methanogenic reactor (TPMR). The TPAR was inoculated with methanogenic sludge similar to the SPR, but was operated with step-wise increase in the loading rate and with total recirculation of reactor solids to convert it into acidification sludge. Before each feeding, part of the sludge from TPAR was centrifuged, the centrifuge liquid (solubilized products) was fed to the TPMR and centrifuged solids were recycled back to the reactor. Single-phase digestion produced a methane yield of 0.45 m³ CH₄/kg VS fed and VS removal of 83%. The TPAR shifted to acidification mode at an OLR of 10.0 kg VS/m³ d and then achieved stable performance at 7.0 kg VS/m³ d and pH 5.5–6.2, with very high substrate solubilization rate and a methane yield of 0.30 m³ CH₄/kg COD fed. The two-phase process was capable of high VS reduction, but material and energy balance showed that the single-phase process was superior in terms of volumetric methane production and energy yield by 33%. The lower energy yield of the two-phase system was due to the loss of energy during hydrolysis in the TPAR and the deficit in methane production in the TPMR attributed to COD loss due to biomass synthesis and adsorption of hard COD onto the flocs. These results including the complicated operational procedure of the two-phase process and the economic factors suggested that the single-phase process could be the preferred system for FVW.