Research On The Synergistic Harmless Treatment Of Electrolytic Manganese Slag/red Mud And Its Application In Building Ceramic Tile

Electrolytic manganese residue and red mud are silicon-aluminum solid wastes produced in the process of producing metal manganese and extracting alumina,respectively.In China,the stockpile of electrolytic manganese residue has exceeded150 million tons,and the stockpile of red mud has exceeded 600 million tons.The storage of electrolytic manganese residue and red mud not only takes up a lot of land resources but also causes great pollution to the environment.In addition,open-air storage also causes the loss and waste of silicon and aluminum resources.Therefore,how to realize the safe disposal and efficient resource utilization of electrolytic manganese residue and red mud has become a hot topic for many researchers.Building ceramic bricks are ceramic products made from silicon-aluminum resources such as clay and quartz.However,the excessive exploitation of clay seriously damages land resources.In order to solve these two problems at the same time,this paper takes electrolytic manganese residue and red mud as the research object.Firstly,the electrolytic manganese residue and red mud are harmless to each other.Secondly,the waste residue（ER）after harmless treatment is used to prepare building ceramic bricks.Explore the appropriate process conditions for the mutual harmless treatment of EMR and RM.The suitable process conditions for the preparation of building ceramic tiles using harmlessly treated waste residue（ER）were studied and the sintering process and kinetic control of building ceramic tiles prepared by ER were analyzed.The effects of ZrO₂and AlF₃·3H₂O on the fracture toughness of building ceramic bricks were studied.The main results are as follows:（1）Under the suitable treatment conditions of stirring time 320 min,electrolytic manganese residue and red mud content 1:1（mass ratio）,solid-liquid ratio 1:1.4,the removal rate of ammonia nitrogen in EMR can reach 85.87%（in the form of NH₃）,and the removal rate of soluble manganese ions can reach 86.63%(solidified in the form of Mn_3.88O₇（OH）and KMn₈O₁₆).At the same time,the alkaline substances in the red mud were transformed into Na₂SO₄and Mg₃O（CO₃）₂to achieve the purpose of harmless treatment.In the process of red mud and electrolytic manganese residue mutual treatment,the kinetic process of ammonia nitrogen removal reaction and manganese ion curing reaction is controlled by membrane diffusion and chemical reaction mechanism.In addition,the treatment system can also solidify the heavy metal ions in the waste residue,so that the leaching concentrations of Cr³⁺,Cu²⁺,Ni²⁺and Zn²⁺and other heavy metal ions in the treated waste residue are 1.45 mg·L^-1,0.099 mg·L^-1,0.294 mg·L^-1and 0.449 mg·L^-1,respectively.The leaching concentration of heavy metal ions was lower than the limit concentration in Chinese standard GB5085.3-2007.（2）The suitable preparation conditions for preparing building ceramic bricks using harmlessly treated waste residue（ER）are electrolytic manganese residue-red mud content of 56%and calcination at 1150°C for 1.5 h.The variance of the verification and evaluation of the appropriate condition parameters by the response surface method is 0.9603,and the error is small.The ceramic tile prepared under suitable conditions is anorthite ceramic tile,and the content of anorthite can reach40.31%.The existence of impurity ions reduces the formation temperature of mullite,which makes mullite form at 1150°C,and the content of mullite can reach 2.58%.The close stacking of anorthite and the interspersed skeleton structure of mullite make ceramic bricks have excellent mechanical properties,and the compressive strength of ceramic bricks can reach 138.2 MPa.The sintering process of ceramic bricks is mainly divided into four stages,corresponding to the removal of free water crystal water,the dehydration of residual Al O（OH）,the crystal transformation of Al₂O₃,the formation of（Ca,Na）（Al,Si）₄O₈and Ca Al₂Si₂O₈,and the continuous formation of Ca（Al,Fe）₁₂O₁₉and mullite.Among them,stage 1 corresponds to the phase boundary chemical second-order reaction mechanism(mechanism function:F（α）=（1-α）^-1),and stage 2 corresponds to the phase boundary–controlled reaction and one-dimensional movement mechanism（mechanism function:F（α）=α）.Stage 3corresponds to the random nucleation and growth mechanism(mechanism function:F（α）=[-ln（1-α）]^1/4).Phase 4 corresponds to the Mampel power law exponential form nucleation reaction mechanism(mechanism function:F（α）=α^1/2).（3）The mechanical properties,flexural strength and fracture toughness of the ceramic bricks were 173.85 MPa,29.3 MPa and 7.72 MPa·m^1/2,respectively,when the addition of ZrO₂was 8%,the addition of AlF₃·3H₂O was 3%and the sintering temperature was 1100°C.The synergistic effect of multiple toughening mechanisms such as microcrack toughening,phase transformation toughening,particle dispersion toughening of ZrO₂and whisker toughening of AlF₃·3H₂O makes ceramic bricks have higher bending strength and more stable fracture toughness.It was found that Cr³⁺,Cu²⁺and Ni⁺were not detected in the leaching concentration of heavy metals in the ceramic bricks.The leaching concentrations of Mn²⁺and Zn²⁺were 0.403 mg·L^-1and0.15 mg·L^-1,respectively,which met the requirements of the Chinese standard GB5085.3-2007 for the limited concentration of heavy metals.The internal and external exposure indexes of the ceramic bricks are 1.2 Bq·kg^-1and 2.0 Bq·kg^-1,respectively,which can only be used for exterior decoration and other outdoor purposes.