Solidification/Stabilization Of Electrolytic Manganese Residue And Its Safty And Environment Research Of Road Fill For Application

With the rapid development of the electrolytic manganese industry,the storage of electrolytic manganese residue has become a considerable environmental issue.It not only takes up a lot of land resources,but also easily causes heavy metal pollution of soil,surface water and groundwater.Therefore,considerable efforts have been made to treat electrolytic manganese residue.This paper provides an overview of the curing/stabilization of electrolytic manganese residue and its environmental safety for road filling,as well as its environmental harmless and recycling status.The main findings are as follows.?1?The physicochemical properties of electrolytic manganese residue collected from a manganese product factory in Hunan were analyzed by moisture content measurement,specific surface area test,X-ray fluorescence spectroscopy?XRF?and leaching toxicity analysis.The main composition of manganese residue is clay mineral such as SiO₂,Al₂O₃,Fe₂O₃,CaO and MnO.The specific surface area of manganese residue is 10.06m²/g.The results of leaching toxicity showed that electrolytic manganese residue belongs to II class industrial solid waste.?2?The experiments on curing/stabilization of electrolytic manganese residue showed that the best effect was obtained under the conditions that the contents of Na₂S,quicklime,fly ash and curing agent cement were 1.25%,2.5%,3%and 12%,respectively.The leaching concentrations of Mn and Pb were 0.022 mg/L and 0.019 mg/L,respectively,which were in accordance with GB8978-1996 Class I standard and GB3838-2002 Class IV standard.When the dosage of ionic mineralizer was 3%,the leaching solutions of Mn and Pb were 0.263mg/L and 0.0385mg/L,respectively,which met the GB8978-1996 first-class standard and GB3838-2002 IV standard.?3?The mechanical properties of the manganese residue was analyzed by geotechnical experiments.The results show that the solidified/stabilized manganese residue is a high liquid limit clay with a particle size of 0.075 mm,the liquid limit of 60.3%,and the plasticity index of 31.6,which is unsuited to use as road filling without technical treatment.It is necessary to match more than 30%of sand when making road filling materials.The average permeability coefficient of the solidified/stabilized manganese residue is1.02×10^-7cm/sec,and the permeability coefficient is small.It indicated that the heavy metals in the manganese residue used as a road filling material after solidification/stabilization were not easily leached by rainwater and groundwater.As solidified/stabilized manganese residue used for road filling material,the optimum moisture content is 24.8%.The free expansion ratio of solidification/stabilizated manganese residue is 29.5%and the average of CBR_2.5 is 6.57.?3?The effect of 30-year rainfall on the leaching of manganese slag after solidification/stabilization and its long-term effect were simulated by column immersion experiment.The experimental results show that the leaching concentrations of Mn and Pb are lower than the standard value,especially when the precipitation of lead pollutants and the effect of rainfall on the leaching of manganese slag roadbed filler are both small.It is noted that the leaching concentration of Mn has increased year by year since the21st year and needs to be taken seriously.?4?The average moisture content of the backfilled manganese slag is23.54%,which is close to the optimum moisture content required by the geotechnical experiment of 24.8%.Backfilling avoids groundwater exploitation areas and groundwater utilization areas.The leaching concentrations of manganese slag Mn and Pb after backfilling are in accordance with GB8978-1996 Class I standard and GB3838-2002 Class IV standard,which can effectively control their pollution to environmental.