The Technology And Final Product Research Of Geopolymer Solidified With Heavy Metal

Geopolymer is a new kind of inorganic polymer, the molecularity of which consists of Si O Al which mainly connected by electrovalent bond and covalent bond, because its cage shape like zeolite, be able to solidify heavy metal ion effectively. As compared with traditional cement, it has merits such as high intensity, low leaching rate of deleterious substance, excellent sulfate resistance capability and antacid capabilityThe modification methods of main raw materials of geopolymer were studied in the dissertation, the molecule structure of metakaolin and it's chemistry character were also analyzed. It was studied the effect of raw material, quantity of alkaline activator, amount of water and reaction temperature on geopolymerization reaction, it is concluded that the molar ratio of n(SiO₂)/n(Al₂O₃) should be 4.0-4.5, and n(Na₂O)/n(SiO₂) should be 0.29-0.31 when the intensity of geopolymer is high, the average 7 days compressive intensity is over 30Mpa; when the solid-to-water ratio is about 0.32, the mixture of metakaolin and alkaline activator have good fluidity and viscosity, the module is smooth and has excellent intensity; furthermore, geopolymer module has high compressive intensity if the temperature is about 30°C.Investigation on geopolymeric reaction with blast furnace slag(BFS) were carried out, the result shows that BFS could enter into geopolymeric reaction, it's compressive intensity could be more than 9MPa when the addition of BFS is reach to 50%.It is also studied how geopolymer solidify heavy metal ion and heavy metal waste(chromium residue). It shows that the solidification efficiency of Pb2+, Cu2+, Cd2+ are more than 99.7%. The solidification efficiency of Cd2+ is highest among these ions, almost approach 99.9%¹00%, and the compressive intensity of geopolymer is quite high.The compressive intensity of geopolymer with chromium residue is quite high, it's 7 days compressive intensity is over 35MPa when the content is 30%. The solidification efficiency of total Cr is high, and the leaching toxicity of total Cr is less than national standard. However, the leaching toxicity of Cr(VI) is fairly high, Cr(VI) has a excess leaching toxicity than national standard. Whereas once slag is added to geopolymeric reaction, the solidification effect of chromium residue by geopolymer is improved obviously, the leaching toxicity of total Cr and Cr(VI) are far less thannational standard when the addition of chromium residue is 30% and slag is 40-60%. Sulfate resistance experiment indicate that geopolymer has excellent sulfate resistance capability after it solidify heavy metal, it is able to keep stable under sulfate environments and its sulfate resistance coefficient could reach 1.025;it is also proved to be good antacid capability, and the compressive intensity loss is only 1.3% when attacked by acid solution(pH=l,3,4,5) for 28d.In order to investigate the final product structure after geopolymer solidify heavy metal, the geopolymer and the waste form of cement are analyzed by X-ray, SEM from physical and chemical angle.