Application Of PPy/TiO₂ Photocatalytic Microbial Fuel Cells In Cobalt Recovery

As the main component of the cathode material for waste lithium batteries,cobalt is widely used in electronic products such as new energy vehicles,mobile phones,and computers.Thinking of the scarcity of cobalt resources,the rate of consumption and the environmental pollution caused by the disposal of cobalt-containing products,the recovery of cobalt from waste cobalt products has become the focus of attention in the world today.Traditional recycling methods mainly include chemical,physical,biological and electrochemical methods.These methods have many drawbacks such as high energy consumption and secondary pollution.In recent years,the bioelectrochemical system has shown obvious advantages in the treatment of heavy metals and organic wastewater.The electricity-producing microorganisms degrade organic wastewater,which can not only reduce the concentration of organic matter,but also generate a certain amount of electric energy,and rely on the oxidation-reduction capacity of the cathode to recover heavy metals,treat waste with waste,and realize the recycling of resources.Bioelectrochemical systems are mainly divided into microbial fuel cell(MFC)and microbial electrolysis cell(MEC).At present,many researchers have successfully realized the recovery of cobalt using the bioelectrochemical coupling system,but due to problems such as over-potential,the recovery rate and processing rate of cathode cobalt are not ideal.Therefore,it is necessary to study a new type of bioelectrochemical system to achieve efficient removal of Co(?).The photocatalytic microbial fuel cell converts light energy and chemical energy in wastewater into electrical energy at the same time to improve the battery's power generation performance.Based on this,this paper constructs photocatalytic MFC and photocatalytic MEC to explore the influencing factors of the system and the recovery of cathode cobalt,in order to improve the battery's power generation capacity and heavy metal recovery capacity.The main conclusions are as follows:(1)Construct a photocatalytic MFC,and explore the influence of factors such as the ratio of excess sludge and nutrient solution,electrode spacing,catholyte pH value and external resistance on the photocatalytic MFC power generation performance and wastewater treatment effect.It was found that a smaller electrode spacing and catholyte pH value can improve the battery's power generation capacity;too large or too small external resistance is not conducive to battery power generation;when the ratio of excess sludge to nutrient solution is 1:1,the battery has the best power generation capacity.The maximum open circuit voltage is 0.661V,and the maximum power density is 6337.5 m W/m²,which are 1.27 and1.76 times that of the photocatalytic MFC without nutrient solution.(2)Use the reduction ability of the photocatalytic MFC cathode to leaching Co(?)from Li Co O2,the influence of factors such as electrode material,light conditions,electrode plate area and cathode electron acceptor dosage on the electricity generation performance and Co(?)leaching effect was explored.It is found that when the electrode pitch is 1cm and the catholyte pH is 2.0,the maximum power density of the photocatalytic MFC and the leaching rate of Co(?)are 8554.3 m W/m² and 43.7%,respectively,which are 1.87 and 1.81 times of the traditional MFC;changing the doping amount of PPy,the leaching rate of Co(?)increased to 49.9%;the size of the plate area and the dosage of lithium cobalt oxide have a great influence on the battery's electricity production and the leaching of Co(?).(3)The photocatalytic MEC is driven by the photocatalytic MFC,changing the photocatalytic MEC plate area and catholyte Co Cl2 ion concentration and other factors to explore the effect of reducing Co(?)in catholyte to elemental Co.It was found that the removal rate of Co(?)by photocatalytic MEC was increased by 29%compared with traditional MEC,and the maximum power density was increased by 32%;the lower the concentration of CoCl₂ ion concentration,the better the removal effect of Co(?),and the maximum removal rate was 91.5%;Using the stabilized power supply to directly drive the photocatalytic MEC,the removal rate of Co(?)exceeds 99%.The photocatalytic MFC-MEC system has a low removal rate of Co(?)in the actual waste lithium battery LiCoO₂.The total removal rate from Co(?)to Co is only 24.0%.