Study On The Treatment Method Of Ammonia-nitrogen From Electrolytic Manganese Residue Leachate

Harmless treatment and utilization of electrolytic metal manganese residue?EMR?are crucial to electrolytic metal manganese industry.The ammonia-nitrogen double salt in EMR gradually dissolved in the natural precipitation during the storage process,forming the leachate contained the manganese ion and ammonia nitrogen,which have potential danger to environment.Therefore,it is crucial to change the phase of ammonia-nitrogen complex salt in the EMR and shorten the ammonia leaching period and harmless treatment.In this project,physicochemical properties of EMR,and ammonia rapid extraction and effective removal methods were researched.Three aspects for the projectare shown as follows:?1?The influence of different leaching methods on the physicochemical properties of EMR was carried out.The results showed that an double layer formed by a large number of conductive ions in the manganese slag slurry under electric field was conductive to the dissolution of ammonia-nitrogen double salts containing Mn²⁺,Ca²⁺and Mg²⁺in the EMR.?2?Pulsed electrochemical oxidation was used to treat low concentration of ammonia nitrogen in EMR leachate for the first time.The ammonia removal efficiency was around 85.01%by pulsed electrolysis under the conditions of Cl^-?NH₄⁺moral ratio of 0.96,current density of 70 mA/cm²,initial pH of 9,pulse frequency of 5000 Hz,duty cycle of 50%.Compared with direct-current electrolysis,the ammonia removal rate was increased by 16.10%and the energy consumption was saved 20.72%under the same conditions.That is,the dosage of chlorine ion and energy consumption were decreased by pulse electrolysis,when dealing with the same concentration of ammonia-nitrogen solution.The ammonia removal process by pulse and direct electrolysis followed pseudo first-order kinetics,and the dynamic equations could be expressed as v=-_dt^dc=kj^1.770C_C²._l⁵-⁸⁷C_NH4^-0.8+⁹⁴ and v=-_dt^dc=kj^2.181C_C²._l⁹-²⁷C_NH4^-0.7+⁸⁷,respectively.In addition,it was indicated that the coexisting cations in manganese leachate could inhibite the ammonia removal efficiency to a certain extent.?3?Electrochemical combined with third pole adsorption was used to treat low concentration of ammonia nitrogen in EMR leachate.The effects of particle electrode dosage and coexisting cation species on the treatment of ammonia nitrogen were investigated.The result showed that the ammonia-nitrogen removal efficiency was improved significantly by particle electrodes,while the coexistent cation species had a little effect on the ammonia-nitrogen removal rate.The ammonia was completely removed in 240 min at particle electrode dosage of 100 g.The natural clinoptilolite acted as a particle electrode in the reaction system.One was the ammonia removal in the solution by the particle electrode adsorption,which was consistent with the Freundlich adsorption isothermal model;the other was ammonia oxidation to nitrogen by the active intermediates?·OH and H₂O₂?on the particle electrode surface under the electric field.