Research on the Preparation of Functional Cerasmite with Fly Ash and Sludge
|School||Anhui University of Technology|
|Keywords||swelling ceramsite fly ash sludge SEM modification|
Fly ash and sludge as two solid wastes, their emissions are increasing with the rapid development of china’s economy and seriously affect the environment. At the same time, they take up a lot of land resources. Fly ash and sludge are dull, not diluted and have a long-term potential harmfulness. From its transportion, storage and disposal of each link, they will bring many harmful effects on the environment. Especially the sludge has a lot of harmful substance, if not properly handle will cause serious environmental pollution problems.Based on the sludge from the first wastewater treatment plant and fly ash from a certain power plant of Huainan as the main raw material, sodium silicate and calcium carbonate as accessories, ceramsite were burned in the experiment research. By comparison with the inorganic composition of the raw materials and according to Reliy three-phase thermodynamic equilibrium systems, fly ash and sludge have the material basis of burned ceramsite and after adding small amounts of sodium silicate and calcium carbonate a melting point may appear between1100℃-1200℃.Through the theory, the formula screening test and the orthogonal experiment, the optimal formula and process conditions of ceramsite with different uses was obtained in the test range. The best quality ratio of ceramsite for water treatment was sludge:fly ash:sodium silicate:calcium as7:9:2:2and the optimum process conditions were preheating temperature400℃(preheating time15mins), calcination temperature1170℃and calcination time15mins. The best quality ratio of ceramsite for building material was6:10:2:2, the optimum process conditions were preheating temperature300℃(preheating time15mins), calcination temperature1170℃,calcination time20mins.The performance test results show that the loose unit weight of ceramsite in water treatment is680kg/m3, grain volume weight is1260kg/m3, bibulous rate is36%and the specific surface area is6.82m2/g. From leaching toxicity test, the ceramsite will not cause environmental pollution and water second pollution. This has to do with physical and chemical composition and the structure composition of fly ash. The loose unit weight of ceramsite for building material is760kg/m3. Grain volume weight is1260kg/m3. The compressive strength is18.2Mpa. the burned ceramsite has certain economic and environmental benefits.In order to improve the functional performance of the ceramsite, respectively for water treatment and building materials, the ceramsite was modified by different kinds of modifier. The experiments show that the best modifier used in water treatment is AlCl3and modified ceramsite is suitable for treatment of wastewater with pH value between4.5～10.0. From single factor experiment and orthogonal experiment, the best modifier for building ceramsite is Fe2O3and the best process for modification is as follows:dipping in the0.095mol/L iron hydroxide solution for12h and then calcined under the condition of500℃for15mins.Performance test results show that the saturated adsorption amount of organic matter of modified ceramsite used in the water treatment is0.2254mg/g. Organic adsorption quantity of modified ceramsite in water treatment is3.5times compared with that of the untreated ceramsite.The compressive strength of the modified ceramsite for construction is31.9Mpa. The compressive strength increased nearly one time compared with that of the unmodified ceramsite and modified ceramsite is more suitable for building materials of high strength requirement.