The Study On The Synthesis And Properties Of Electrolytic Manganese Residue And Ferronickel Slag Porous Ceramics

Electrolyt ic manganese residue?EMR?is a kind of industrial waste produced during the electrolysis of manganese metal.The large amount of EMR not only occupies land,but also pollutes the environment,which has become a major problem for electrolyt ic manganese industry and environmental protection.The ferronickel slag?FNS?is also a kind of industrial solid waste produced from the pyrometallurgical process with laterites for nickel production.It has become a difficult problem to deal with FNS,due to the large discharge and low comprehensive utilization.The utilization of EMR and FNS,on the one hand,can reduce the pollution to the environment,on the other hand,it can realize the reuse of materials which meet the requirements of sustainable development.In this paper,two kinds of industrial waste slags-EMR and FNS were used as main raw materials,metakaolin and waste glass were auxiliary raw materials,and calcium carbonate,sawdust as well as carbon powder were used as pore-forming agents to prepare porous ceramics.The porous ceramics could be used as exterior wall insulation materials.The optimal formula of porous ceramics was obtained by formula design.The results showed that the fabrication of porous ceramics by EMR and FNS is feasible.The optimal formula of EMR-based porous ceramics was 20%electrolyt ic manganese slag,70%waste glass and 10%metakaolin.With the increase of the amount of EMR,the sintered matrix becomes denser and cannot form a porous structure.The optimal formula of FNS-based porous ceramics was 30%FNS and 70%waste glass.With the increase of the amount of FNS,the sintered matrix becomes denser and cannot form a porous structure.X-ray diffraction?XRD?,comprehensive thermal analysis?TG-DSC?,field emission scanning electron microscopy?SEM?,energy spectrum?EDS?,and other analytical methods were used to study systematically the influences of sintering temperature,holding time,etc.on bulk density,compressive strength,porosity and crystal phase of porous ceramics using a single factor variable method.Under the optimal preparation conditions,the microstructure,thermal conductivity and compressive strength-thermal conductivity-bulk densit y relationship of porous ceramics were evaluated.The results showed that the sintering temperature and holding time had a significant influences on the properties of porous ceramics.When the sintering temperature is low,the porous ceramics have small pore size and uneven distribution,high bulk densit y and compressive strength,and low porosity.With the increase of the sintering temperature,the pore diameter gradually increases,the distribution becomes more uniform,the bulk density and the compressive strength decreases and the porosity increases.EMR-based porous ceramics had excellent comprehensive properties under the sintering temperature of 1020°C for 45 min,sawdust content 5%and forming pressure 5 MPa,the bulk density,compressive strength,and porosity were 600kg/m³,3.9 MPa and 77.2%,respectively.FNS-based porous ceramics had excellent comprehensive properties under the sintering temperature of 1060°C for 60 min and 45 min when sawdust and carbon powder were used as pore-forming agent?1%of content?,respectively,and forming pressure 5 MPa.The bulk density,compressive strength,and porosity were 740 kg/m³,3.01 MPa,74%,and 830 kg/m³,4.48 MPa,71.7%,respectively.XRD results showed that the phase of porous ceramics were diopside and augite,and the rest was glassy phase.SEM images showed that there are many flaky crystals in the porous ceramics.EDS results indicated the crystal is diopside,and the diopside is the source of the strength of porous ceramics.The thermal conductivit y of electrolytic manganese residue-based porous ceramics was 0.052 Wm^-1k^-1,and the thermal conductivity of ferronickel slag-based porous ceramics was 0.119 Wm^-1k^-1.With the increase of bulk density,the pore diameters decreased gradually,and the compressive strength and thermal conductivity of porous ceramics showed an upward trend.The fitting curves satisfy the expression y=y₀+A?e^R₀x?,which is in line with the exponential relation and has good correlation.