Characterization Of Manganese Slag And Removal Of Manganese Ions In Waste

Due to manganese and its compounds wide application, manganese is one of the important strategic resources and basic material in China, applications of manganese and manganese compounds is very wide. While, because of lower grade of manganese resources, it is reported that producing It electrolytic manganese metal would produce 7-9t manganese slag. Moreover, most of manganese slags were improper treated, which would cause great harm to environment. Therefore, it is necessary to solve manganese slag. In this study, the manganese slag was collected from a manganese factory in Xiangxi Hunan Huayuan, the basic physical and chemical properties and toxicity evaluation of manganese slag were studied, and the extraction experiments, adsorption experiments, flocculation and sedimentation experiment were inployed. Our study would provide a theoretical guidance for treating manganese slag and extraction solution. The main results are as follows:1) The electrolytic manganese slag contented a water content of 23.00%, pH value of 5.66, and elements are more than 20. Manganese slag main phases CaSO4, CaSO4 · nH2O, Al2O3, SiO2, (NH4)2Mn2(SO4)3, Mn(O,OH)2, CaMn2O4 and MnFe2O4, etc. Manganese slag particles dispersed very messy, mainly long columnar structure, interspersed with a large number of irregular reunion-like substance.2) Comprehensive leaching toxicity and TCLP (Toxicity characteristic leaching procedure) to evaluate the Pollution Act of manganese slag, the experimental result shows that the effective content of manganese slag exceeds" Discharge standard of pollutants for municipal wastewater treatmentplant" (GB 18918-2002) (2.0mg·L-1) 200-400 times, which is indicating that manganese slag on the environment have a certain hazards.3) In the exaction experiment, the best extraction process for three extracting agents were show:for HCl, 0.5mol·L-1, solid:liquid=1:10, extraction time 24h, extraction times 3; for EDTA, 0.2mol·L-1, solid:liquid=1:10, extraction time 24h, extraction times 3; for DTPA, 0.01mol·L-1, solid:liquid=1:5, extraction time 24h, extraction times 3; three extraction of manganese slag leaching effect were:HCl (42.97%)> EDTA (24.19%)> DTPA (18.22%); optimum conditions, the three kinds of eluent through leaching manganese slag, not compared to the leaching of manganese slag, leaching toxic concentration decreases exponentially.4) In adsorption experiments, the zeolite and activated carbon were used to remove Mn ion from extraction solution. When the zeolite dosage 37.5g·L-1, pH 4, adsorption time 30min, the removal of manganese ions can be maintained at above 99%, the adsorption process followed pseudo second-order kinetic model correlation 0.99 above; Langmuir and Freundlich adsorption models could better fit manganese ions adsorbed on zeolite, relevance, were 0.97 and 0.96, the theoretical maximum adsorption capacity of 15.60mg·g-1. When activated carbon dosage 162.5g·L-1, pH 6, reaction time 30min, removal rate was 20.1%, but far less than zeolite. And proposed a pseudo second order model can better fit the dynamics of activated carbon, a correlation coefficient reached 0.98; adsorption on activated carbon and manganese can better meet the Freundlich adsorption model, a correlation coefficient of 0.97. Adsorption of zeolite is better than activated carbon.5) Using sodium peroxide to treat high concentration (189.69mg·L-1) manganese slag extracts, at the same time using sodium peroxide, ferric chloride and PAC (poly Aluminium Chloride) to treat low concentration (2mg·L-1) manganese slag extracts, found that when the dosage 62.5g·L-1, pH 6, a high concentration of manganese ion in the extraction dropped 1.71mg·L-1, less than 2.0mg·L-1, achieve " Discharge standard of pollutants for municipal wastewater treatmentplant " (GB 18918-2002); changes of manganese ion in the low concentrated extraction is not affected by the time, manganese ion removal of sodium peroxide is unaffected of pH, PAC, the optimal pH of the solution is 4, ferric chloride, pH 9, but did not reach the " Discharge standard of pollutants for municipal wastewater treatmentplant " (GB 5749-2006) (0.1mg·L-1); sodium peroxide, ferric chloride, aluminum chloride and manganese in water samples with low concentrations of manganese removal with increasing dosage but reduced the impact of time and a three-caught from the reaction; sodium peroxide for the removal of manganese from the effect of initial pH value; PAC removal rate increases with pH and then decreased, the optimum pH of 4; ferric chloride removal rate with increasing pH Cheng rises upward trend, an optimum pH of 9; sodium peroxide and the two flocculants composite added:2.5 g·L-1 sodium peroxide+1.0 g·L-1 of ferric chloride,2.5 g·L-1 carbonate peroxide sodium+1.0 g·L-1 PAC,5.0 g·L-1 sodium peroxide+1.0 g·L-1 of ferric chloride,10.0 g·L-1 sodium peroxide+1.0 g·L-1 of ferric chloride removal efficiency up to 100%.