Study On The Preparation Poly Aluminum-ferric-silicate Flocculants From Fly Ash And The Treatment Of High Turbidity Water

Utilization of reclamation wastes is an important means for the sustainable development of the economy and the protection of the ecological environment. In the thesis,the study of solid excretory product,fly ash,exhausted from a thermal power plant in Baotou. By analyzing the chemical elements,its Al₂O₃ content is 27.22 percent, its Fe₂O₃ content is 9.32 percent, and its SiO₂ content is 57.88 per cent, which having the condition to extract those kinds of elements and to prepare PAFSi by adopting technology of hydrotropy and technology of acid pickling. Analysis proves that the Fe³⁺ element of fly ash is easily out in acid environment. Aluminum oxide and silicon dioxide in double salt 3 Al₂O₃·SiO₂ form. Under normal operation,they are very hard soluble in acid or alkali. In order to destroy the chemical bond, they need to added co solvent into them. First, the experiment is performed utilizing technology of hydrotropy and technology of acid pickling.This test shows that added sodium carbonate as co solvent could make leaching yield amount to 70 percent, and come to the conclusion that the better condition to make iron and aluminum up to the highest leaching yield. The best conditions were as follows: the first step, added Na₂CO₃ into fly ash and the ratio of addition is 0.5,calcined them for 1 hour in high-temperature electric resistance furnace and the calcinations is at a temperature of 900℃.The second step, stir and leach the product 1 hour at a temperature of 110℃with 4mol/l hydrochloric acid. Then,using the obtained aluminum, silicon and iron as raw material prepared PAFSi,and design an orthogonal test for the several factors during the preparation: silicon,aluminum and iron ratio,the pH of flocculants,ternperature,etc. The result of orthogonal test revealing that are better conditions of preparation,when Si:Al (mol:mol) is 1:0.5,Si:Fe (mol:mol) is 1:0.5,pH value of flocculants is 1.1,temperature is 60℃,curing time is 2 hours. Last,utilizing prepared PAFSI flocculation separately to test on kaolin and suspension,carrying out the flocculation test,determined the best conditions of flocculation: when level of diatomite use is 2g, level of flocculation use is 7.5ml,pH value of aqueous sample is 8. Something that has formed lumpy or fluffy masses, thickening, sedimentation is fast,sediment of comparatively small size,light transmittance is 79.6precent. Contrast prepared PAFSI with poly aluminums chlorides and poly ferric sulfates. This study indicated that flocculate effect of PAFSi is better than poly aluminums chlorides' and poly ferric sulfates'.