| The harmless treatment and resource utilization of electrolytic manganese residue(EMR)as the final solution has become a consensus in the industry.In view of the characteristics of fine particle size,poor mechanical properties and excessive heavy metal content of the EMR,based on reactive magnesia(r-Mg O)carbonizing solidification technology and microbial technology,this paper proposes the microbial solidification and remediation technology of the EMR with r-Mg O,which can not only repair heavy metals,but also improve mechanical properties.The research results provide theoretical support for microbial solidification and remediation technology of the EMR with r-Mg O,and have important scientific significance and application prospect for promoting the resource utilization of the EMR.The main contents and research results of this paper are as follows:(1)The effects of various factors on microbial solidification and remediation technology of the EMR with r-Mg O were researched,and the mechanism of remediation and solidification was clarified.The effects of the content of reactive magnesia and urea,initial moisture content and age were studied.Combined with biochemical reaction and test analysis,the mechanism of heavy metal remediation and strength improvement was clarified.The results show that the mechanical properties of EMR can be improved and the damage of heavy metals can be reduced after solidifying and remediating by microbial technology with r-Mg O.With the increase of age and reactive magnesia content,the strength of solidified EMR gradually increases.With the increase of urea content and initial moisture content,the strength of solidified EMR first increases and then decreases,and the optimal urea concentration and initial moisture content exist.Reactive magnesia is hydrated to produce magnesium hydroxide,and carbonic acid generated by microbial hydrolysis of urea is further carbonized to generate carbonated products such as Nesquehonite,cementing particles and filling pores,improving strength and increasing the difficulty of heavy metal leaching.The exchangeable heavy metals react with magnesium hydroxide to form hydroxides,which in turn produce more stable carbonate.(2)The mechanical properties of remediated and solidified EMR,such as strength and deformation,are researched.Five different concentrations of r-Mg O(0%,5%,10%,15%,20%)are selected to carry out the triaxial consolidation and drainage tests.The strength and deformation characteristics of remediated and solidified EMR were analyzed.The results show that the stress and strain of remediated and solidified EMR show strain softening property,which can be roughly divided into four stages: elastic growth stage,plastic strengthening stage,failure deformation stage and residual strength stage.The volumetric deformation is characterized by shear contraction and then dilatancy.With the increase of r-Mg O content,the peak deviatoric stress and residual deviatoric stress increase,and the dilatancy increase.The internal friction Angle increases exponentially with the increase of r-Mg O content,and the cohesion increases linearly with the increase of r-Mg O content.An empirical formula for strength prediction was given.(3)The dry-wet cycle durability of remediated and solidified EMR was researched.Eight dry and wet cycle tests were carried out on the remediated and solidified EMR with different r-Mg O content(0%,5%,10%,15%,20%).The effects of dry-wet cycle times and r-Mg O content on the dry-wet cycle durability were studied and analyzed.The results show that the dry-wet cycle durability of EMR is significantly improved after remediating and solidifying.With the increase of dry-wet cycles and the decrease of r-Mg O content,the mass and dry density of remediated and solidified EMR decreased,and the strength remained high after dry-wet cycles.The leaching concentration of remediation heavy metal Mn was kept at a low level,showing good dry-wet cycle durability. |
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