Recovery Of Cobalt From Spent Lithium Batteries And Its Photocatalytic Degradation Of Ciprofloxacin Doped With TiO₂ Materials

Spent lithium-ion batteries contain a large amount of valuable metals(such as Co,Ni,Li,etc.).Taking appropriate methods to recover metal resources from spent lithium-ion batteries cannot only solve the problem of environmental pollution,but also realize recycling of waste resources.In this paper,to recover cobalt from spent lithium-ion batteries,the hydrometallurgy was used.For the recovered anode material and mixed materials(contained anode and cathode materials),the leaching solution was taken by the H₂SO₄-H₂O₂system.Two extractants(Methyl trioctyl ammonium chloride and Cyanex272)were used to recover cobalt from the two leaching solutions.The effects of chloride ions concentration,saponification rate,extractant concentration,phase ratio and p H on the recovery of cobalt were investigated.For the recovery of Co in the cathode material,the first-stage extraction rate of Cyanex272 for cobalt under the best conditions is 99.99%,and the extraction rate of Li is4.96%.With 0.2 mol/LH₂SO₄,the ratio of stripping is O/A=1/2,the cobalt stripping rate reaches 99.99%;TOMAC's primary extraction rate for cobalt is 98.97%,and the Li extraction rate is 3.77%.With 0.05 mol/LH₂SO₄and the stripping phase ratio(O/A)=1/2,the cobalt stripping rate reaches 99.95%,and Li⁺is not detected in the stripping solution.For the recovery of Co in the mixed electrode material,under the optimal conditions,the first-stage extraction rate of Co by the extractant TOMAC is 98.05%,and the loss rate of Ni is0.86%.Using pure water for stripping,the stripping rate reaches 97.06%.The primary extraction rate of cobalt by Cyanex272 was 98.38%,and the loss rate of Ni was 2.28%.Using0.2 mol/LH₂SO₄to strip Co²⁺from the organic phase,the rate of stripping reached 99.99%,and no Ni²⁺was detected in the stripping solution.After extracting and separating cobalt and lithium with Cyanex272,the cobalt sulfate solution(Co²⁺8.773 g/L)obtained by stripping was used as the doping ion source to prepare TC samples with different cobalt doping ratios.The Co²⁺doping in TiO₂greatly enhance the visible light responsive ability,physical adsorption property,and the photogenerated electron-hole pair separation efficiency for the TC samples.All the degradation rates of ciprofloxacin over the TC samples exceed 90%under 60min UV-Vis-NIR light irradiation,and within Vis-NIR light irradiation of 180min,the degradation rates for the optimum TC samples also reach 90%,which are much higher than those of pure TiO₂,since more holes and superoxide(O₂^·—)radicals are generated on the TC samples.According to the intermediate products produced from the photodegradation of ciprofloxacin,the main degradation pathway belongs to the oxidation reactions of its piperazine ring.The excellent photocatalytic performance of the TC samples for the degradation of ciprofloxacin proves that it is feasible to use the Co component from the spent lithium-ion batteries as the metal dopant of photocatalysts.