Containing Heavy Metals Residue With A Sintered Brick-making Process

Various types of solid wastes are generated each year and the total amount reaches to 5.4 billion tons. Small parts of these wastes are actually treated so that hundreds of millions of tons have not been properly disposed. The atmosphere, groundwater, surface water would be polluted without the control of the wastes entering environment. Local investigation found that the total output of industrial solid waste which contained heavy metals such as Mn, Cu, Cd, Ni and piled or landfilled in the region of Zhubugang, Xiangtan City reaches to 17 million tons per year, This disposal uses a lot of soil and makes a serious problems on the local environment. Sintered bricks produced from these solid wastes is an effective way to solve the problem after detected the composition and characteristics of the solid wastes, which not only improves the local environment, but also creates some economic benefits.In this paper, the solid wastes in Xiangtan Zhubugang Industrial Park were used for sintered brick making. The feasibility of sintered bricks made from electrolytic manganese slag-shale-fly ash was proved, and the effects of proportion, sintering temperature, holding time, cooling-down method on the sintering properties of sintered bricks were examined the performance of brick and the solidification of heavy metals were analyzed by Inductively Coupled Plasma (ICP), Scanning Electron Microscope (SEM), Energy Disperse Spectroscopy (EDS), X-ray Diffraction (XRD),Thermogravimetric-Differential Thermal Analysis (TG-DTA), Flame Atomic Absorption Spectrometry (FAAS) and compressive strength testing. It was found that the optimal condition is: the ratio of manganese slag, shale and fly ash of 4:5:1, sintering temperature of 1000℃holding for 2h and natrual cooling. The compressive strength of bricks up to 22.64 MPa, met the MU20 standred of the National normal sintered brick. the Toxicity Characteristic Leaching Procedure (TCLP) result of manganese in the leaching was 0.6763 mg/L which met Chinese National Standard. Additionally, the sintering temperature was determined by testing the porosity of the brick body at different roasting temperature, it was found that the optimum sintering temperature was 1000℃when the ratio of electrolysis manganese slag, shale, and fly ash was 4:5:1.Moreover, solidification of heavy metals contained in cadmium slag, iron slag and calcium-magnesium slag were studied in this paper. Considering the properties of the brick and the solidification effect, the addition volume of cadmium slag should be less than 1%, the optimal dosage of iron slag and calcium-magnesium slag were 5% and 10%. Phase composition and morphology of the brick were analyzed by XRD and SEM, respectively. The sintering temperature range was tested after adding iron slag and calcium-magnesium slag to the mixture. It was indicated that the sintering temperature range will became narrow after the addition of iron slag, and the optimum sintering temperature was 1000℃when the dosage of iron slag was 10%; the sintering temperature would decrease significantly and the sintering temperature range was further reduced after the addition of calcium-magnesium slag, the most suitable sintering temperature was 950℃when the dosage of calcium-magnesium slag was 5%.