Adsorption And Desorption Of Mn²⁺ In Leachate From Manganese Residue

Mn2+ ions in leachate from manganese residue may infiltrate into the soil, underground water and surface water system, which could be huge potential hazard to the surrounding environment and people. It needs reasonable treatment. Fluidized bed combustion fly ash(FBCF) used to be a kind of construction material and its chemical contents is similar to the coal fly ash. The adsorption ability of sample after modified treatment is strengthened and can be used as a low-price adsorbent.On the foundation of experiment on the chemical content, micro structure and leaching pattern of Mn2+ in manganese residue, the manganese residue is not a kind of hazardous waste. The best modified parameters were as below:The ratio of modified agent with rawnaterial was 1:2, grinding time was 60 min and grinding speed was 525r/min. The micro structure, particle size and specific area of modified sample were different from the raw sample. The adsorption capacity was raised from 5.50mg/g to 12.93mg/g and adsorption ratio was raised from 13.75% to 32.33%.Meanwhile, the adsorption experiment was carried out and the optimal parameters were 35℃, pH6.5 and adsorbent ratio 15g/L. Four adsorption kinetics and two adsorption isotherms were fitted with the adsorption process. It turned out that the adsorption process was endothermic and spontaneous which was suited to the Elovich kinetic and Langmuir isotherm. The mechanism of it could be a monolayer adsorption.The desorption experiment was carried out and focused on the effect by concentration and temperature. It turns out that the 0.5mol/L and 35℃ were optimal parameters in desorption experiment. The highest desorption capacity was 9.36mg/g and desorption ratio was 96.01%. The analysis of two samples demonstrated that the complexation between anions and Mn+ located in active position on modified sample which leads to the desorption process. The mechanisms of adsorption and desorption are physical adsorption and chemical adsorption.The modified FBCF is a effective and low price adsorbent which can also be regenerated by the citric acid. The technique will be utilized in low concentration heavy metal wastewater treatment and beneficial for the environment.