Researches On Strengthen Transformation Method Of Manganese And Ammonia Nitrogen From Electrolytic Manganese Residue

Electrolytic manganese residue?EMR?is a kind of industrial solid waste with high moisture content found in filters after sulphuric acid leaching of manganese carbonate ore.At present,China's EMR have piled up to 120 million tons.Moreover,large numbers of electrolytic manganese residue leachate wastewater?EMRLW?were produced in the process of storage of EMR.A lot of easy-migrating manganese ions and ammonia nitrogen in EMR and EMRLW would pollute the surrounding when it enters the environment.Therefore,harmless disposal of EMR and EMRL has become one of the issues that concern the academia,society and industry.This paper is based on the principle of electrodynamics remediation technology,the theory of chemical process intensification,the balance principle of precipitation dissolving and the basic principle of electrocatalytic oxidation.Centre on the harmless treatment and resource utilization of manganese and ammonia nitrogen in the EMR,strengthen researches on transformation method of manganese ions and ammonia nitrogen from electrolytic manganese residue is studied.The conclusions are as follows:?1?Physicochemical properties of EMR were analyzed by XRD?XRF?FT-IR?SEM-EDS and DTA-TGA.The results shown that the EMR mainly contains SiO₂ and CaSO₄·2H₂O.Manganese and ammonia nitrogen,the main pollutants of EMR and EMRL,mainly exists in the form of MnSO₄·H₂O,?NH₄?₂SO₄,?NH₄?₂?Mg,Mn,Fe??SO₄?₂·6H₂O,and are much higher than national security standards.?2?Based on the principle of electrokinetic remediation technology,electrokinetic technology extrusion of ammonia nitrogen and manganese from EMR was carried out.The results shown that the removal efficiency of the oxidizable and residual fractions of manganese were lower than that of exchangeable and reducible fractions in the process of electrodynamics extrusion.Electrokinetic removal of manganese and ammonia nitrogen from EMR was significantly affected by the electrolyte and pretreatment solutions.Electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen removal,manganese and ammonia nitrogen in the EMR reached the regulated level after the treatment.?3?Strengthening the secondary extraction of manganese from the EMR by electric field strengthening transformation was studied.Fe³⁺was reduced to Fe²⁺,then the high-valent manganese was reduced to low-valent by Fe²⁺.The extraction efficiency ofmanganese was 96.2 %,which was 51.8 % higher than that of attained under the same conditions without an electric field and Fe²⁺.The kinetic analysis indicates that the process of extracting manganese from EMR was control by solid membrane layer diffusion,and the dynamic equation can be shown as:.?4?Based on the basic theory of process intensification,stabilization/solidification of manganese and ammonia nitrogen in EMR by low grade magnesium oxide and phosphate?P-LGMgO?was studied.The result shown that the stabilization efficiency of ammonia nitrogen and manganese were 84.0 % and 99.9 % using P-LGMgO process.Ammonia nitrogen was stabilized by struvite?NH₄MgPO₄·6H₂O?and manganese was solidified by bermanite?Mn₃?PO₄?₂?OH?₂·4H₂O?and pyrochroite?Mn?OH?₂?.The value of all the measured metals were meet the national safety standards and the concentration of ammonia nitrogen can be reduced from 504.0 mg L-1to 76.6 mg L-1.?5?According to the balance principle of precipitation dissolving,high concentrations of manganese and ammonia nitrogen removal from EMRLW was studied.The results shown that the removal efficiency of ammonia and manganese was 95.0%and 99.9 %.Manganese was first removed in the form of Mn₃?PO₄?₂·7H₂O,and then ammonia was removed in the form of NH₄MgPO₄·6H₂O.Moreover,the removal efficiency of ammonia decreased from 84% after the first cycle to 66 % after the fifth,and the removal efficiency of manganese maintained at 99.0 %.Economic evaluation revealed that the treatment cost can be reduced by 68.5 % on average by recycling the precipitates for three times.?6?Based on the basic principle of electrocatalytic oxidation,pulse electrocatalytic oxidation treatment of simulation leachate wastewater was studied.The result shown that the remaining manganese and ammonia nitrogen from simulation leachate wastewater were less than 0.2 and 0.1 mg L-1 by pulse electrocatalytic oxidation,which conformed to the national security standards.The process of electrochemical oxidation ammonia nitrogen from wastewater followed the pseudo-first-order kinetics,and the dynamic equation can be expressed as:.