Research On Electrochemical Recovery Process Of Waste Phosphoric Acid Etching Solution In Photoelectric Industry

In the liquid crystal display processing industry,a large amount of aluminum etching waste acid is generated during the production process,and such waste acid is generated in the wet etching process.Among them,are abundant renewable phosphoric acid resources which have high recycling value.At the same time,they are also a type of hazardous waste to be treated urgently.Direct discharge will cause great harm to the environment and is also a waste of resources.In order to treat and recycle this kind of waste acid,this thesis uses electrochemical technology to process the nitric acid and acetic acid impurities in the waste acid to purify and recover the phosphoric acid.The preliminary research is carried out and the technical and economic schemes for applying the technology to actual production are evaluated.According to the results of electrochemical experiments,the best combination of catalytic electrodes is Ir/Ta-Ti mesh electrode for anode and Pt-carbon cloth electrode for cathode;In the diaphragm-free electrolytic reactor,monitor changes of various parameters in the electrolytic reaction when change the current density and water flow rate,parameters include:the removal rate of nitric acid and acetic acid,the ammonia nitrogen generation rate of by-products,and the space-time yield of the electrode.According to the experiment,it showed that the comprehensive removal rate of HNO₃ and acetic acid is the highest at the current density of 21.25 m A/cm² and the flow rate of 2.11L/h for the waste aluminum etching solution with an initial nitric acid concentration of 49g/L and an acetic acid concentration up to 703g/L.The removal rate of HNO₃ by electrolysis in 10h was 51.1%,and the removal rate of acetic acid was 50.2%.At this time,the average space-time yield of cathodic reduction of nitric acid was 0.112 g/L*h*cm²,and the average space-time yield of anodic oxidation of acetic acid was 4.395 g./L*h*cm².In a diaphragm-type electrolytic reactor,for a waste aluminum etching solution with an initial nitric acid concentration of up to 28 g/L and an acetic acid concentration of up to 255 g/L,at a current density of 30.25 m A/cm²,the HNO₃ removal rate for 4 hours of electrolysis is 45.0%.The removal rate of acetic acid is 23.0%,and the concentration of ammonium ions accumulated in the system is less than that of diaphragmless electrolysis.However,as the flow rate increases,the efficiency of removing nitric acid by the diaphragm electrolyzer decreases continuously,and the acetic acid removal rate is the higest when the flow rate is 2.11L/h.The space-time yield of HNO₃ and acetic acid for diaphragm electrolyzers increases with the increase of current density,and decreases gradually with the increase of flow velocity.The process of electroreduction and denitrification of nitric acid in the two reactors is more consistent with the first-order reaction kinetics,and the correlation R² is greater than 0.8500.The economic analysis and the establishment of system dynamic economic model simulation for the industrialization of the purification of phosphoric acid from the electrolytic removal of miscellaneous waste aluminum etching solution and the establishment of a system dynamic economic model simulation.Compared with the existing traditional process,the electrolytic recycling resource treatment waste liquid process is environmentally friendly,taking into account the utilization of phosphoric acid resources and Protect the advantages of the environment and make policy recommendations for the development of the park based on the model.