Study On The Preparation And Adsorption Properties Of Sepiolite-based Foamed Concrete

Nowadays,the ever-increasing energy crisis drives the society to develop energy conservation products.Foam concrete has received much attention as a energy-saving and environmentally-friendly product for construction industry due to its unique properties such as low density,heat preservation and insulation,and sound insulation.In recent years,it has been widely used in energy conservation for buildings.As a natural mineral material,sepiolite has the characteristics of large specific surface area,strong adsorption performance,high temperature resistance,etc..Thus,to enhance the physical properties of foam concrete,sepiolite has been employed to prepare composite foam concrete.The effect of addition of sepiolite on the physical properties of foam concrete has been investigated.The results show that the rheological behavior of the foam concrete can be improved by the addition of sepiolite.Besides,the sepiolite foam concrete exhibits remarkable adsorption properties towards indoor air pollution and heavy metal ions.This paper focuses on the activation treatment of sepiolite,the design of the mix ratio of foamed concrete,and the adsorption properties of the foam concrete.The main contents and conclusions of the paper are as follows:1)Raw sepiolite contains a small amount of impurities,and the pores are easily blocked,resulting in a low specific surface area and low adsorption capacity.Therefore,this paper uses a simple and easy low-temperature heat treatment process to activate the sepiolite.The heat-treatment increases the specific surface area of sepiolite by eliminating the adsorbed water molecules.XRD,SEM and BET analysis results show that the optimized heat treatment temperature is 300℃.The specific surface area of sepiolite after treatment at this temperature increases without significant changes in morphology.2)Three variables including sepiolite content,water-cement ratio,and activation temperature of sepiolite were used to optimize the mix ratio of sepiolite foamed concrete.The dry density,volumetric water absorption,and volumetric water absorption rate,the 7-day compressive strength and thermal conductivity of the foam concrete were verified.The optimized mix ratio design of sepiolite foamed concrete is as follows:sepiolite content is 40%of the material,water-cement ratio is 1.The effect of adding sepiolite on the thermal insulation performance of foamed concrete was characterized.The infrared thermal image shows that the heat conduction rate of sepiolite foamed concrete is lower than that of ordinary foamed concrete,indicating that the sepiolite foamed concrete has better thermal insulation properties.3)In this paper,the common indoor pollutant gases such as formaldehyde and ammonia are selected to study the gas adsorption behavior of sepiolite foamed concrete.The results indicate that the sepiolite foamed concrete has a strong adsorption effect on the two toxic gases.The saturated adsorption capacity for formaldehyde is 10.7 mg/g,and the saturated adsorption capacity for ammonia is 2.37 mg/g.Sepiolite foamed concrete can purify indoor air by adsorbing toxic and harmful gases,which is of great significance to environmental protection.4)The ion adsorption test for sepiolite foamed concrete metal was designed.The order of the adsorption effect of five metal ions from strong to weak is:Mn²⁺>Cd²⁺>Cr³⁺>As³⁺>Pb²⁺.Because sepiolite has metal ion exchange capacity,sepiolite foamed concrete has a strong enrichment effect on heavy metal ions,and can play a role in purifying sewage.In the process of adsorbing heavy metal ions,the sepiolite foamed concrete does not collapse and damage its internal structure,and can be recycled after adsorption.