Stabilization Of Manganese Residue And Preparation Of Porous Phosphate Materials

Huge amount of manganese residue occupies large area of land in China, causing serious environmental pollution and potential safety hazard, which not only effects people’s standard of living, but also restrains the development of electrolytic manganese industry. In this paper, the systematic properties and stabilization under weak alkaline and oxidation condition of manganese residue were investigated, furthermore, stabilized manganese residue was used to prepare porous phosphate materials by gel injection molding. The results were as follows:Manganese residue particle was small, with the average particle size of4.62μm, free water content was about35%, and crystal water was11%, so it requires dehydration treatment without high-intensity grinding. Phases of manganese residue were complicated and poor in crystal structure. The content of iron and manganese was about20%and existed in the form of goethite and manganese oxide that transformed into hematite and manganous manganic oxide respectively calcined at800℃-900℃under air atmosphere. Simulating acid rain to lixiviate manganese residue at different calcination temperature, the amount of manganese ion in the lixivium showed three stages, the measured value was about0.8%below300℃, about2%～3%at400℃～600℃, and about0%above800℃.Manganese residue was leached by simulated acid rain, the concentration of manganese ion was used to evaluate the degree of stabilization of manganese residue, the influences of alkali dosage, oxidant and oxidation time were investigated. The results indicated that using air and KMnO4as the oxidant can each effectively reduce the concentration of manganese ion in the lixivium. In the condition of alkali dosage3.0%～3.5%and oxidation time5min-30min, concentration of manganese ion in the lixivium was about30mg/L using air volume4L/min, and below1mg/L using KMnO4dosage1.2%～1.4%, and the pH of reaction liquid and lixivium was about10.0and7.0respectively. At room temperature, oxidation time within30min, and pH9-10, manganese phase transition process in the solution system was as follows: Mn2+â†'OH-Pyrochroite Mn (OH)2â†'Ox Hausmannite Mn3O4.Porosity and compressive strength were used to evaluate performance of the material, the influences of aluminum dihydrogen phosphate concentration, water-cement ratio, vesicant dosage, and curing condition were investigated. The results indicated that water-cement ratio had significant influence on material performance and should be strictly controlled within0.35～0.37; Vesicant dosage within0.5%～1%was able to improve porosity; Curing temperature could improve material porosity but reduced material strength, while curing time had the opposite effect, so curing temperature should be within150℃～250℃, and time should be1h-2h. Calcium phosphate, aluminum phosphate were the main gelling composition in the manganese residue-phosphate cementing material.