Heavy Metal Contamination Characteristics And Remediation Technology Research Of The Smelting Slag For Lead And Zinc

With the exploitation of mineral resources and people required to improve the living environment. The smelting slag pollution to the environment has attracted humans'attention increasingly, which heavy metals smelting slag has harmful effects on the environment the most.In this paper, lead and zinc smelting slag was taken as the research object. Classified the different preparation based on the methods research the samples. The total content analysis, leaching toxicity analysis and sequential extraction procedure analysis was taken by microwave digestion system and atomic fluorescence spectrometer and other equipment in the laboratory. And by designing the electrokinetic remediation experiment, reached a certain removal ratio for various heavy metals of slag samples. It provided the theoretical basis and technical support in controlling the lead and zinc smelting slag pollution. The main contents are:Through the analysis of the total content, the five measured heavy metals of smelting slag all had very high levels. As was 13510mg/kg, Pb was 1228.05 mg/kg, and Zn was as high as 64820 mg/kg. Once this slag release to natural conditions, will cause serious hazards on the surrounding environment.In the leaching toxicity experiments, the experiment simulated scene for the industrial solid waste landfill disposal or inappropriate storage, and was subject to acid rain conditions, harmful substances infiltration and leaching, caused the pollution of groundwater. Based on the simulation scene, binding experiments on the feasibility, H₂S0₄/HNO₃ mass ratio was 2:1, liquid to solid ratio was 10:1, pH was 3.20±0.05, made the leaching toxicity of the sample to quantitative analysis, think that the slag leaching toxic is non-hazardous.Though the morphological analysis of slag samples, found that there were some differences in samples of different sampling sites of heavy metal elements Zn, Pb, Cd and As species distribution. Take the ratio to the average of the form of every elements, distribution of elements in the form of Zn was found mainly in residual and oxidizable fraction, both the total percentage of 89.71%. Distribution of elements in the form of Pb was oxidisable and reducible fraction, ratio the two fraction is 59.92%. Distribution of elements in the form of Cd was residual fractions and oxidizable fraction, ratio the two fraction reached 88.98%. The morphologies of As elements was mainly the residual fraction, the proportion of it was up to 99.56%.Through analyzing the potential ecological risk of the slag samples. Thinking that Zn and Pb had a higher relative content in the slag samples, these two elements had the ecosystem harm most. Followed by Cd, and As is almost no potential harm to the environment.According to health hazard assessment method recommended by the U.S. EPA. Calculated the each daily dose for three exposure pathway of every heavy metals. Then calculated that the total non-carcinogenic hazard index was 8.72E +07. The total carcinogenic risk index was 2.82E-15. Total non-carcinogenic hazard index was much greater than 1. the total carcinogenic risk index was much less than 10E-6. Therefore, there can be considered that it exists non-carcinogenic risk of the waste, cancer risk does not exist. through the morphological analysis experiments of this issue, we found there were some defects in the traditional method. Real direct impact on human health and the potential impact of heavy metals were less than the total amount of heavy metals impact on human health effects. The specific quantitative relationship determined by various forms accounte for the amount of the total.By designing experiment, select 30v DC voltage, removal time is 152h. The sample was repaired electrically. By analyzing the current, the variation of voltage and the electrical conductivity of remediation process, found that: (1) The current varied from small to large , reacting to 6h, the current slow declined after the highest, finally stabilized, the steady current was about 10mA. (2) The voltage of each repair area were not equal, the voltage of 1 #, 2 # Showed a slow decline from the beginning of the experiment until to the end of the experiment. 3 # was in a steady state basically. 4 #, 5 # were achieved the lowest voltage after the start of the experiment to 30h hours, Then began a regular voltage increase, the voltage was as high as 9.38v in 5 #. (3) Early in the experiment, As the electrical repair reacting, the electrical conductivity greatly improve, electrical conductivity increases rapidly. In the 18h 54h of this time, conductive properties was best, current is relatively high, repair efficiency was the best. removal efficiency of the repair experiment were calculated. It was concluded that: Zn was 29.51%, Cu was 22.97%, Pb was 20.93%, Cd was 12.87%.