| In order to develop a lightweight,high-strength,geopolymer porous insulation material with the same duration as buildings,this article uses metakaolin as the raw material,water glass and sodium hydroxide as the alkali activator to prepare metakaolin-metakaolin porous material by physical foaming,the process parameter of geopolymer porous materials were optimized,and the effects of density and fibers(carbon fiber,basalt fiber)on the structure and properties of geopolymer porous materials were studied,the effects of adsorption time,adsorption temperature,initial concentration of methylene blue,dosage and density of geopolymer porous material on the adsorption of methylene blue were also explored.The research results are as follows:(1)When Na/Al=0.716,Si/Al=1.558,water-solid ratio=0.501,modulus of water glass=1.5,the thermal insulation performance of the prepared geopolymer porous material is greatly improved compared with the traditional cement-based porous material.Compared with the traditional foam concrete,the thermal conductivity of the300 kg/m~3 geopolymer porous material is reduced by 11%,the thermal conductivity of 400 kg/m~3 is reduced by 21%,and the thermal conductivity of 500 kg/m~3 is reduced by 14%,The thermal conductivity of 600 kg/m~3 is reduced by 10%,the thermal conductivity of 700 kg/m~3 is decreased by 18%,and the thermal conductivity of 800 kg/m~3 is decreased by 16%.As the density of the geopolymer porous material increases,the pore structure of the geopolymer porous material becomes more and more dense,and its compressive strength and thermal conductivity are gradually increasing.(2)When the density of the geopolymer porous material is 300 kg/m~3,the optimum content of carbon fiber is 2%.At this time,the prepared geopolymer porous material has the best mechanical properties and thermal insulation properties.With the increase of fiber content(carbon fiber and basalt fiber),the geopolymer porous material structure becomes more and more loose,this is because after adding optimum application rate of fiber,the matrix microstructure becomes dense,but too much fiber is added,the fibers are gathered into clusters or even clumps inside the geopolymer porous material,and the original pores are connected,so that the pore structure is uneven distributed and the pore structure becomes loose.(3)As the adsorption time increases,the adsorption rate(adsorption capacity)of the geopolymer porous material gradually increases,and the greater the dosage of the geopolymer porous material,the greater the corresponding adsorption rate(adsorption capacity).With the gradual increase of the initial concentration of methylene blue solution,the adsorption rate and adsorption capacity of the geopolymer porous material both increased first and then decreased.When the initial concentration of methylene blue was 80 mg/L,the adsorption effect of the geopolymer porous material Preferably,the adsorption rate reaches 14%and the adsorption capacity reaches 35mg/g.As the adsorption temperature increases,the adsorption rate of the geopolymer porous material increases inordinately.In addition,increasing the temperature has a great influence on the diffusion of methylene blue molecules on the external surface and internal pores of the geopolymer porous material.The adsorption of methylene blue by geopolymer porous materials is more in line with pseudo-first order kinetic,indicating that the adsorption of methylene blue by geopolymer porous materials is mainly physical adsorption;The Langmuir model can better describe the adsorption process of geopolymer porous materials to methylene blue,indicating that the adsorption process is mainly monolayer adsorption;Adsorption thermodynamic studies have found that the adsorption of methylene blue by geopolymer porous materials is a endothermic,spontaneous,and entropy-increasing process,and the temperature increase can promote the adsorption reaction. |
