Research On The Comprehensive Recycling And Utilization Of Ferrophosphorus Waste Residue

With the development of human society and the progress of industry,the traditional fossil energy resources are increasingly exhausted.The use of fossil energy has led to a series of environmental problems.Human beings have put forward higher requirements for energy.The new energy industry is booming in order to meet people's demand for clean,safe and sustainable energy at present and in the future.Olivine lithium iron phosphate is one of the cathode materials which used in power lithium-ion batteries.As its precursor,the preparation of iron phosphate has been widely concerned.Ferro-phosphorus is one of the by-product of producing phosphorus by electric furnace.Ferro-phosphorus has not been used effectively for a long time,due to its difficult to deal with.If it could be effectively utilized to prepare battery-grade iron phosphate,it can not only meet the requirements of the development of new energy materials,but also turn waste into a benefit.The battery grade precursor nano FePO₄ was synthesized by precipitation method.Ferro-phosphorus was used as the iron source and the phosphorus source and the ferro-phosphorus was dissolved in the mixture of nitric acid and sulfuric acid.The influence of the concentration of nitric acid,the reaction time and temperature on the dissolving rate of ferro-phosphorus were studied.The effect of the proportion of iron and phosphorus,reacting temperature and pH values on the performance of the FePO₄were also explored.The crystal morphology,structure and chemical composition of the prepared nanoscale iron phosphate were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,thermo gravimetric and differential scanning calorimetry?TG-DSC?.Experimental results show that the optimum experimental conditions for the dissolving of ferro-phosphorus are the concentration of nitric acid is1.5 mol/L,the reaction time is 4 h and the reaction temperature is 90?.The dissolving rate of the Ferro-phosphate under these conditions is 95.1%.The optimal experimental conditions for the preparation of iron phosphate are the proportion of iron and phosphorus is 1:1,the reaction temperature is 60?and the reaction pH is 1.0.XRD and SEM analysis showed that the prepared FePO₄ had high crystallinity,and regular morphology,uniform particle dispersion,its primary particle size is around 100 nm.The iron and phosphorus content test shows that the molar ratio of iron to phosphorus was 0.97.The content of impurity elements meet the requirement of battery grade FePO₄ precursor.FePO₄ was prepared under the optimum experimental conditions and LiFePO₄/C was prepared by carbon thermal process.The material has good crystallinity and excellent cycling performance.Using acid solution to treat ferro-phosphorus slag,it can dissolve ferro-phosphorus slag quickly,so that the iron and phosphorus in the waste residue can be leached maximally.Production of battery grade FePO₄ from ferro-phosphorus slag solution can not only achieve comprehensive utilization of phosphorus and iron,accomplish the aim of turning the industrial solid waste into resource,but also improve the economic benefits of enterprises.So that,both the environmental benefit and the economic benefit of enterprise have achieved win-win.