Technology And Heavy Metal Solidification Of Glass-Ceramic From Sewage Sludge Residue By Microwave Method

The production of sewage sludge is growing with the expansion of the scale of urbanization, the pyrolysis technology is gradually becoming an important way of the sludge treatment owing to its unique advantage. However, pyrolysis gives rise to the by-products (sewage sludge residue), how to achieve the reuse and the harmless treatment of sewage sludge residue become a research hotspot. Glass-ceramics -as a new material, are widely used because of its high added value, wide range of ingredients, and the good curing effect of heavy metal. People started to investigate the glass-ceramic based on the sewage sludge ash. However, the utilization of sewage sludge ash is not high in the corresponding study, concentrated from 20% to 60%, and the heat treatment is a key factor to determine the glass-ceramic performance. It was as a focus of the study to optimize the heat treatment in order to prepare the glass-ceramics with excellent performance based on the high utilization of sewage sludge ash by the microwave methods.In this paper, the sewage sludge residue were used as the raw material to design the formula of the glass-ceramic with the good performance mixed with 79.05% sewage sludge ash at the optimal conditions of the heat treatment. The chemical composition of sewage sludge residue was analysis by XRF in this experiment, the as-quenched glass was made by the microwave melting method to determine the best conditions. As-quenched glass was tested by DTA analysis to determine the heat treatment system. The nuclear phase has little effect on the crystalline phase formation. The key study was to investigate the heat treatment of the high sewage sludge ash glass-ceramic based on the crystallization temperature and the crystallization time. The XRD and SEM analysis of the glass-ceramic were used to deterimine the crystallization type, the crystallization shape and other microstructure. Finally the TCLP methods and the five-step Tessier sequential extraction method were used to investigate the leaching toxicity and the species distribution to characterize the curing effect of the heavy metals.The results showed that the as-quenched glass was prepared by mixing with 79.05% sewage sludge residue, compared to the amount of the sludge increased by 23%, in the alumina crucibles reactor dedicating to the glass by the microwave melting. The best parameters of glass melting process: rising to 750℃at the heating rate of 50℃/min, then keeping 15min at this temperature and getting the black glass of the uniform and no cracks. It was focused on the crystallization temperature and time inorder to determine the best heat treatment. The results showed that the crystallization temperature was 1000℃for 2h, mainly the crystal phase of anorthite and diopside. The volume density of the sample was 2.7g/cm3. The water absorption was 0.025%. The acid resistance of the sample was stronger than the alkali. The microhardness was 8.25GPa. The bending strength was 70.642GPa. The prepared sample had good physical and chemical properties. The optimum condition of the heat treatment was the nucleation temperature 820℃, the nucleation time 1h, the crystallization temperature 1000℃, the crystallization time 2h to prepare the glass-ceramics based on sewage sludge residue. Finally, it showed that the leaching of heavy mentals in the glass-ceramics was lower than the national standard and the residue form was the main species, which was stable in the environmental condition, thus confirming the glass-ceraimcs based on the sewage sludge residue were applicability.