Study On The Preparation And Properties Of Fly Ash/Electrolytic Manganese Slag Geopolymer Materials

Recently,geopolymer as a hot topic research of new green cementitious materials in the world.It has the advantages of rapid hardening,high strength,good corrosion resistance,easy accessible raw materials,simple process,energy saving and environmental protection,etc.At the same time,its unique three-dimensional network structure has good solidification effect on heavy metals.Many industrial wastes containing aluminosilicate minerals can be used as raw materials for geopolymer,because the main raw materials of geopolymer are aluminosilicate minerals and alkali activator.There are a large number of fly ash and electrolytic manganese slag containing heavy metals without effective treatment in China.The massive accumulation of fly ash and electrolytic manganese slag have caused great harm to air,water and soil.This work was aimed at the problems of the serious pollution of fly ash,electrolytic manganese slag and heavy metals,fly ash and electrolytic manganese slag were used to prepare geopolymer materials.Through the solidification and adsorption of heavy metals of geopolymer porous materials prepared by fly ash,achieved the effective utilization of reduction,harmless and resource of fly ash and electrolytic manganese slag.This study had great significance to the economic,social and environmental aspects.In this paper,mainly research on the influence factors of the mechanical properties of fly ash geopolymer materials and the solidification effects of Mn²⁺,Cd²⁺,Pb²⁺and Cr³⁺.The process parameters of preparing geopolymer by electrolytic manganese slag and fly ash and the influence of the amount of electrolytic manganese slag on the properties of geopolymer.The effect of the preparation processes on the porous material of fly ash.The adsorption effect of porous material of fly ash on Cu²⁺.The structure,morphology and toxic leaching of the samples were characterized by XRD,FTIR,SEM-EDS and ICP-AES.The main research results were showed as follow:The compressive strength of the geopolymer on 28-day prepared by the fly ash under the optimum technological parameters was 44.1 MPa.The solidification rate of 1wt%-3wt%Mn²⁺,Cd²⁺,Pb²⁺and Cr³⁺by fly ash geopolymer reached more than 99.9%,and the solidification effect of heavy metals was Pb²⁺>Cr³⁺>Cd²⁺>Mn²⁺.The compressive strength of 1.5wt%Pb²⁺sample on 28-day was 49.34 MPa,and the compressive strength of all solidified bodies was above 20 MPa.The results of XRD,FTIR and SEM showed that the phase and corresponding characteristic peaks of fly ash geopolymer before and after solidification were changed,and the samples have dense microstructure,but the morphology were different.When the content of electrolytic manganese slag was 30%,the compressive and flexural strength of the electrolytic manganese slag-fly ash geopolymer sample on 28-day were 43.46 MPa and 9.92 MPa,respectively.When the content of electrolytic manganese slag was more than 30%,the compressive strength of the samples was above 15 MPa.XRD,FTIR and SEM analysis showed that there were some aluminosilicate minerals containing heavy metal ions,and Si-O-T（T=Si or Al）peaks were shifted in the reaction products,and the microstructure of all samples were relatively dense.The results of EDS and toxic leaching showed that the heavy metal ions in the electrolytic manganese slag was effectively solidified.The compressive strength of the porous material prepared by fly ash,alkali activator,H₂O₂ and N16 foam stabilizer under the best technological conditions was 0.73 MPa,volume density was 0.46 g/cm³,the porosity was high and the pore size distribution was relatively even.The porous material of fly ash geopolymer can effectively adsorb Cu²⁺.The removal rate of Cu²⁺was 85%in the Cu²⁺solution of 200 g/L under the conditions of solid-liquid ratio of 5 g/L and pH=6.The adsorption isotherm conformed to the Langmuir isotherm model and the mass transfer process was consistent with the pseudo-second-order kinetic model.