Hydrogeochemistry Of Heavy Metals Release In Coal Gangue During Dry-wetting Processes

Coal gangue that stored outdoor or for landfill will release pollutants by weathering,and seriously pollute surrounding environment.At present,there exists more leaching immersion test of heavy metals coal gangue and environmental pollution both in domestic and overseas,but less study for releasing process,leaching mechanism and the release of hydrogeochemical of heavy metals coal gangue under effect of weathering.In this paper,the researcher take the coal gangue from Liaoyuan diggings,Hancheng Shanxi Province as study object,which study the influence of dry and wet alternation test and immersion test effect to pollutants release of high-sulfur and low sulfur gangue.Adopt dry and wet alternation test,immersion test to analysis alternation of wetting and drying effect humidity change soak pH,liquid-solid ratio and redox conditions on form transformation features and pollutant release of high sulfur and low sulfur coal gangue in the dry and wet alternation process.1.Cr and Zn mainly exist in residue during coal gangue wet and dry process.In the early stage of alternation,Cd in coal gangue was mainly exist in iron manganese state and residue,and then is the organic matter-bound,after period of dry and wet alternation,Cd mainly existed in residual state.In the process of dry and wet alternation,Cu mainly exists in the organic binding state,and then is the residual state.Pb of coal gangue during the earlier stage exists in organic sulfide state and residual state,in the later circulation,the percentage of Pb exchangeable state and Fe& Mn oxide bound,organic bound and residual percentage is basically the same.2.Alternate strength increases,the Cd transformational degree from residue to exchangeable state,carbonate state,iron manganese state and organic matter shall be in higher level.Cu conversion ratio from carbonate form to exchangeable and organic carbonates is higher,more conducive to promoting the transformation of Pb from iron manganese and organic bound to carbonates,and organic to iron manganese transformation,which promote Zn transform from carbonate,iron manganese and organic fractions to exchangeable,control conversion of iron manganese and organic matter to carbonate state.Carry out alternation of drying and wetting at 10% and 50% humidity conditions,Cr transform from the residual state to exchangeable,carbonate,Fe& Mn and organic states.3.The higher the pH value,the greater the leaching solution pH value and also the higher of coal gangue leaching solution Eh value.With the increase of wet and dry cycles,the heavy metals are released continuously,and the increase of salinity leads to the increase of leaching solution mineralization.Soak solution pH=2,there is no bicarbonate in leaching solution of coal gangue low sulfur and high sulfur.Low sulfur and high sulfur coal gangue Ca2+,Mg2+ and SO42-three kinds of ions greatly influenced by soaking solution pH.When soaking solution pH=2,low sulfur and high sulfur coal gangue leaching solution concentration Cl-was significantly higher than other pH soaking concentration.The greater the liquid-solid ratio,the larger the pH value of coal gangue leaching solution,the smaller the Eh value and conductivity.Low sulfur and high sulfur coal gangue leaching solution Ca2+ and Mg2+ concentration influenced by soaking liquid solid ratio,the smaller the liquid-solid ratio,the bigger the two kinds of ion concentration.The leaching solution of high sulfur and low sulfur coal gangue pH value was lower than that of the reduction immersion environment,and the Eh value and conductivity were higher than that under the reduction condition.The change of Ca2+ concentration was greatly affected by the reduction conditions,the longer the reduction time,the greater the concentration of ions.The concentration of Cl-in Coal Gangue Leaching solution was significantly higher than that under reducing condition.4.During the alternation of wetting and drying,the concentration of Cr,Cu and Pb decreased gradually with the increase of p H,the concentration of Cd and Zn in the high sulfur and low sulfur coal gangue leaching solution gradually increased.In the alternation of wetting and drying process,the liquid-solid ratio is smaller and more beneficial to the release of Pb;in the middle-late stages dry wet alternation,the liquid-solid ratio is smaller,the concentration of low sulfur coal gangue leaching solution of Cd,Cr,Cu and Zn increased;in the late alternation of wetting and drying,liquid-solid ratio increases,coal gangue leaching solution the greater the concentration of Zn.The concentrations of Cd,Cr,Cu,Pb and Zn in the leaching solution of high sulfur and low sulfur coal gangue were not affected by the oxidation and reduction conditions.5.The results of mass balance simulation shew that the dissolution and sedimenta tion of minerals were the main hydrogeochemical effects in coal gangue water reactio n system.After the first time,the evolution of water chemical components during themixing of high sulfur coal gangue with p H=8 leaching solution,from the initial solut ion to the final solution was experienced by quartz,calcite dissolving,dolomite,pyrite,Gypsum,NaCl,kaolinite precipitation and Ca X2 / NaX cation exchange.