Research Of Preparation Ang Application Of Geopolymer

Geopolymer is a kind of promising advanced inorganic material which was presented in the late 1980s. In recent years, this kind of material has been attracting great attentions. The formation process of geopolymer can be divided into four stages, i.e., dissolution of aluminium and silicon and its complex in the liquid , diffusion from the particle surface into interstitial space, concentrating and polymerization of the components by geochemical reactions to form interstitial aluminosilicate gel, and dehydration of extra water and solidification of the gel phase. The marix phase so formed in geopolymer is similar to zeolite in chemical composition and shows a three-dimensional network in physical framework acting as a structural foundation of geopolymer. It combines some characteristics of organic high polymers, cements, ceramics and it has its own unique properties which include high early strength, low shrinkage, freeze-thaw resistance, sulphate resistance and corrosion resistance. So the applications of the geopolymer are to be found in the automobile and aeronautic industries, non-ferrous foundries and metallurgy, civil engineering, environmental engineerring, plastics industries, etc.With metakaolin and industrial wastes as raw materials, the geopolymer is prepared which results from an inorganic polycondensation reaction. Synthesizing of the geopolymers is conducted between 50℃ and 100℃. And this material is used to the immobilization of Pb2+and Cr6+. The kind of raw materials and the preparation process are determined through the study. Also, the influences of the oxide mole ratios,curing temperature and the kinds of activators ,etc. on the compressive strength are considered. The results show the optimal oxide moles determined by the orthogonal erperiments as below: the mole ratio Na2O/SiO2 is 0.30,the mole ratio SiO2/Al2O3 is 3.7,and the mole ratio H2O/Na2O is 17. The 1-day compressive strength of the geopolymer with this oxide mole ratios can reach 47.19MPa. The 28-day compressive strength can reach 53.81MPa. The conclusion can be obtained that the geopolyemr reveals an amorphous microstructure through the microscopic analysis. The efficiency of the immobilization of Pb2+ by the geopolyemr with this oxide mole ratios is studied. The results show that the efficiency of the immobilization can reach above 99%, when Pb2+ added to the geopolymer is below 1% . Infrared spectrum and SEM measurements show that the immobilization of Pb2+ is occurred not only by physical encapsulation , but by chemical action.