Preparation Of High-Purity Nano-FePO₄ And Research On Its Catalytic And Electrochemical Properties

This paper takes the hazardous solid waste phosphating slag as the research object to study the feasibility of its recycling.Phosphating slag is the by-product of chemical reaction between metal and phosphating solution surface,and the zinc-based phosphating slag mainly contains ferric phosphate（FP）,zinc phosphate,other small amounts of phosphate and impurities.The ferric phosphate with higher purity can be purified from the phosphating slag by using a suitable separation method,and then the surface morphology of the purified ferric phosphate can be modified to obtain nano-scale recrystallized ferric phosphate.In the research process,the main attempt is to use the recrystallized ferric phosphate prepared by purification and modification as the cathode material of lithium ion battery and the catalyst in photo-Fenton experiment,to find an economical way for the regeneration and utilization of phosphating slag.This paper mainly studies the feasibility of resource utilization by analyzing the elements of phosphating slag,purifying high-purity ferric phosphate,carrying out surface modification,and applying it to cathode materials and catalysts.Firstly,the zinc phosphate component is removed by ammonia complex method,then the insoluble particles are removed by screen,and finally other phosphate impurities are removed by adding acid by the traditional hydrothermal method and obtained ferric phosphate.Then,it is modified on the basis of the crudely purified ferric phosphate,and the method adopted is mainly a hydrothermal method,and the ferric phosphate is decomposed and recrystallized under the conditions of temperature and pressure.In the process,the nano-sized ferric phosphate is obtained by controlling the hydrothermal temperature,time,surfactant,solvent and other factors.Finally,the treated samples were characterized and analyzed,such as using Marvern laser particle sizer（LPS）,X-ray diffractometer（XRD）,scanning electron microscope（SEM）,infrared spectroscopy（FTIR）and so on.The results show that when the hydrothermal temperature is 145°C,the hydrothermal time is 24 h,and the dosage of SDS is 0.25 g,the surface modification of ferric phosphate is carried out by adding different modifiers,and the size of the modified ferric phosphate can reach nano-scale.When the modifier is glycerol,the particle size reaches the smallest value,the minimum value of D₁₀can be 0.013μm,and the particle size distribution range of D₉₀is 80-200 nm.When the modifier is propylene glycol,the prepared ferric phosphate has the most uniform size distribution.The particle size is 100-300 nm,and the thickness is 7-80 nm,the crystal size is calculated by XRD,the size of glycerol-modified ferric phosphate is 75.7 nm,and the size of propylene glycol-modified ferric phosphate is 83.6 nm,SEM morphology observation among them,propylene glycol has the most regular morphology and the most uniform size distribution.The nano-scale ferric phosphate prepared above was used as a catalyst to catalyze the degradation of dyes in wastewater and as a cathode material precursor to synthesize lithium ferric phosphate to study its catalytic performance.Sub-micron and nano-scale ferric phosphates are prepared by alcohol solvents of different carbon chains.The catalytic system is constructed as follows:Fe³⁺+UV+H₂O₂Fen-ton system is constructed by catalyst ferric phosphate,H₂O₂,and ultraviolet light.Then,the simulated pollutant Rhodamine B in the wastewater was degraded by the degradation method,and the amount of hydrogen peroxide in the system and the effect of different carbon chain modified ferric phosphates on the degradation of rhodamine B in the system were observed.Scanning electron microscope and other characterization methods were used to characterize it,and its performance and principle were analyzed.When the ferric phosphate material was modified with four-carbon chain butanol,the degradation rate and effect reached the best,and the degradation effect reached 97%within 40 minutes;under the same conditions,the degradation efficiency of the experimental group without catalyst was only 29.5%.Compared the two experiments,the addition of butanol-modified ferric phosphate catalyst increases the experimental rate by 67.5%,the results show that under certain and appropriate experimental conditions,ferric phosphate material can be used as a catalyst and ultraviolet light to form a photo-Fenton.The system effectively removes Rhodamine B dye in the solution,and the degradation effect can reach up to 100%,which can be used as a solution to organic wastewater.Four groups of catalysts with better degradation effect in single-carbon chain monohydric alcohol were selected as the precursors of cathode materials to synthesize composite materials,and their electrochemical properties were studied.The test results showed that the electrochemical properties of lithium ferric phosphate synthesized from butanol-modified ferric phosphate were the best.Nano-scale ferric phosphate was prepared by polyol solvent.The prepared sample ferric phosphate was used as a precursor,lithium source lithium carbonate and carbon source glucose were added,and lithium ferric phosphate was synthesized by carbothermal reduction method.The structure of the material was characterized by X-ray diffractometer（XRD）,scanning electron microscope（SEM）and other instruments,and the electrochemical properties of the material were characterized by a VERTEX.C.EIS electrochemical workstation.At the same time,the ferric phosphates modified with different alcohol solvents were compared,and the electrochemical properties of the prepared cathode material lithium ferric phosphate were analyzed.Compared with pure lithium ferric phosphate,its Electrochemical Impedance Performance（EIS）and Cyclic Voltammetry Performance（CV）are better.At the same time,its capacity still has a good capacity retention rate after repeated charging and discharging.From the experimental results,it can be shown that the modified ferric phosphate is feasible as a precursor of lithium ferric phosphate.However,due to the fact that the raw material itself contains many impurities,the prepared cathode material lithium ferric phosphate has certain It is necessary to make the particle size of the material more uniform,and at the same time,it is necessary to improve the morphology,impurity content,phosphorus-iron ratio and other factors of the material.