| China is still in the period of the rapid development of urbanization and industrialization, and in the consumption of large amounts of mineral resources every day. After mineral separation, mineral resources produce a large amount of tailings, in recent years, serious accidents caused by Long-term tailings piled up repeatedly happened, thus make economy and the ecological environment suffered serious danger. In recent years, governments have rolled out policies about tailings utilization, minimization and harmlessness, especiallly the introduction of "tailings disposal and resource management demonstration project" project, a symbol of our country has already pay attention to tailings disposal and recycling. Currently, the exploitation of mineral resources of the tailings produced the environmental pollution problem mainly for complex multi-contamination of heavy metals. Professors at home and abroad have done a lot of research for the removal of heavy metals in contaminated soils, little research has been done into the safe disposal of heavy metal pollution in tailings. Because of its simple to operate, fast rate, high efficiency and moderate cost, the method of chemical leaching has being favored by large scholars.Regarding gold tailings selected in tailing pons of the dressing plant in Shang Luo as the objects in the study, research the best condition of the single eluent, the best eluent, the best composite eluent and the best condition of drip washing such as the best concentration, the best solid-to-liquid ratio, the best leaching time and so on, by the method of single eluent and composite eluents among HNO3, HCI, DETA and FeCl3. Using digestion method of HF+HClO4+HNO3 to measure the content of metals in tailings and analyzing the content of weak acid soluble form, reducible form, oxidizable form and residual form for metals, find the best eluent so as to realize the efficient innocent treatment to tailings. Results are as followed:The concentrations of Pb, Co, Ni, Sr, Cu and As in samples are 70.00mg/kg, 47.25mg/kg,40.9 mg/kg,315.25mg/kg,41.65mg/kg and 1930.25mg/kg respectively and the concentrations of As is 173 times higher than Shanxi background value. Pb, Ni, Cu and As in tailings exist mostly as the residual form and the content are 46.35%, 47.07%,53.43% and 73.43% respectively; the existence form of Co is mainly reducible with 32.09% and the residual form account for 31.34%and weak acid soluble form occupies 21.31% and oxidizable form holds 15.26%; the residual content of Sr is less with 5.47% and it main existence forms are weak acid soluble form and oxidizable form with 57.54% and 36.13%, respectively. Morphological analysis shows that the residue concutrations of Co and are very low, whereas the biological availability is high and the transformation ability is strong. After Pb, Ni and Co, the redidue concatration and the effective concentrations are mostly equal. The biological availability is also very high, and transformation ability is strong. meanwhile the residue conceatralim of As is very high, but the biological availability is weak, and stable.The best concentration, the best solid-to-liquid ratio, the best leaching time and the best elution times for the four single eluents to the tailing are showed as following: HNO3, 1mol/L,15:1,6h, ltime; the leaching fraction of HNO3to metals (As, Cu, Ni, Pb, Co, Sr) in the best drip washing condition are 27.77%,39.80%,24.57%,26.87%, 20.89% and 65.80%respectively. HC1,2mol/L,15:1,6h, ltime; the leaching fraction of HC1 to metals (As, Cu, Ni, Pb, Co, Sr) in the best drip washing condition are 44.23%, 45.29%,28.57%,31.54%,18.48% and 56.67% respectively. EDTA, 0.1mol/L,10:1,6h, 2times; the leaching fraction of EDTA to metals (As, Cu, Ni, Pb, Co, Sr) in the best drip washing condition are 4.31%,22.05%,9.22%,14.44%,23.61% and 42.62% respectively. FeCl3,0.5mol/L,10:1,12h,3 times; the leaching fraction of FeCl3 to metals (As, Cu, Ni, Pb, Co, Sr) in the best drip washing condition are 40.83%,68.69%, 13.64%,63.97%,51.24% and 69.36% respectively.Analysing comprehensively the leaching effect of the five composite eluents (HCl-EDTA, HNO3-EDTA, HCl-FeCl3, HNO3-FeCl3 and EDTA-FeCl3) to the six metals (As, Cu, Ni, Pb, Co and Sr) in the studied tailings, two conclusions are drew:the leaching fraction of the five composite eluents are far higher than the single eluents (HNO3, HCl, FeCl3, EDTA); the leaching fraction of the composite eluents to metals increases as the concentrations of single eluents (HNO3, HC1, FeCl3, EDTA) rise. According to the drip washing effect of the five composite eluents to heavy metals, the leaching fraction of composite eluent HCl-FeCl3 to Cu in the researched tailings is higher than other composite eluents; the leaching fraction of composite eluent HCl-FeCl3 and HNO3-FeCl3 to As in the researched tailings is slightly higher than other composite eluents; the leaching fraction of composite eluent HCl-FeCl3 and EDTA-FeCl3 to Ni in the researched tailings is a little bit higher than other composite eluents; the leaching fraction of composite eluent HCl-FeCl3 and HNO3-FeCl3 to Sr in the researched tailings is approach to and slightly higher than other composite eluents; the leaching fraction of composite eluent HCl-FeCl3, HNO3-FeCl3 and EDTA-FeCl3 to Co in the researched tailings is approach to and a little bit higher than other composite eluents; the leaching fraction of composite eluent HCl-FeCl3, HNO3-FeCl3 and EDTA-FeCl3 to Pb in the researched tailings is approach to and a little bit higher than other composite eluents. Above all, the leaching fractions for composite eluents to As, Cu, Ni, Pb, Co and Sr are far higher than single eluents. In the meantime, the drip washing effect of the composite eluent HCl-FeCl3 is better than other composite eluents. The best concentration, the best solid-to-liquid ratio, the best leaching time and the best elution times of composite HCl-FeCl3 to tailings is HCl,0.2mol/L, FeCl3, 1.0mol/L,6:1, 6h and 3times and its leaching fraction to As, Cu, Ni, Pb, Co and Sr in the best drip washing condition is 42.37%. |
PDF Full Text Request