Study On The Coupled Migration Characteristics Of Suspended Particles With Wide Gradation And Heavy Metals In Porous Media

The study of the coupled migration characteristics of suspended particles and heavy metal ions is of great significance for the treatment of heavy metal pollutants.In this paper,three different seepage velocities(0.087cm/s,0.173cm/s,0.260cm/s),two kinds of silicon powder with wide particle ranges(the particle size range is 30-2000 nm,2-70?m,and the corresponding median particle size is 227 nm,13.24?m),three concentrations of silicon powder suspension(0.5mg/m L,1mg/m L,2mg/m L)and three concentrations of copper ion solution(100?g/L,200?g/L,400?g/L)are considered to study the impact on the migration process and migration distance.The results are now listed as follows:(1)With the increase of seepage velocity,the relative peak concentration of silicon powder and heavy metals has been increased,and the increase of silicon powder with a small particle size range is obviously larger.The pore volume of silicon powder beginning to appear in the effluent and reaching a relative stability is advanced,while the pore volume of the heavy metal in the effluent reaching a relative stability remains approximately unchanged.With the increase of the seepage velocity,the residual silicon powder concentration and average particle size of the silicon powder with a large particle size range decrease at the migration entrance,and the residual heavy metal concentration also decreases,but the residual silicon powder concentration and the average particle size increase at the longer migration distance,the concentration of residual heavy metals also increases.However,the residual concentration of silicon powder and heavy metals of silicon powder in a small particle size range are reduced at any migration distance,but the median particle size of the silicon powder is approximately unchanged.Therefore,the average migration distance of silicon powder and heavy metals will increase with the increase of seepage velocity.(2)For silicon powder with a large particle size range,the relative peak concentration of the effluent silicon powder and heavy metals is lower.By comparing the situation of the injected solution without silicon powder,it is found that the silicon powder in a large particle size range acts as an inhibitory effect on the migration of heavy metals as a whole,while the silicon powder in a small particle size range acts as a promotive effect as a whole.For the silicon powder with a large particle size range,the residual concentrations of silicon powder and heavy metals at different cross sections are higher,and it will plummet at the migration entrance.As the migration distance increases,the median particle size of silicon powder with a large particle size range continues to decrease,while the median particle size of silicon powder with a small particle size range is approximately unchanged.Therefore,for the silicon powder with a large particle size range,the average migration distance for the silicon powder and the heavy metal is smaller,and there is a large amount of deposition at the migration entrance,while for the silicon powder with a small particle size range,the average migration distance for the silicon powder and the heavy metal is larger and it is more evenly distributed at each migration distance.(3)As the concentration of silicon powder solution increases,the pore volume of the appearance of silicon powder in the seepage fluid advances,and for the silicon powder with a small particle size range,the relative peak concentration of the silicon powder and heavy metals will increase.But for the silicon powder with a large particle size range,the relative peak concentration of the effluent silicon powder will first increase and then decrease,and the relative peak concentration of heavy metals will decrease all the time.As the concentration of injected silicon powder increases,the residual concentration of silicon powder and heavy metals at each migration distance will increase.But for silicon powder with a large particle size range,the median particle size of silicon powder at each cross-section will decrease,while for silicon powder with a small particle size range,the median particle size of the silicon powder at each cross-section remains unchanged.This indicates that the increase in the concentration of silicon powder will reduce the average migration distance of silicon powder with a large particle size range,while the average migration distance of silicon powder with a small particle size range remains approximately unchanged.In addition,by comparing the group without adding silicon powder,it can be found that the presence of silicon powder can increase the average migration distance of heavy metals,and the higher the concentration of silicon powder,the stronger the promotive effect.(4)With the increase of the concentration of injected heavy metals,the relative peak concentration of silicon powder in the effluent will decrease,and the suppressive effect of silicon powder with a large particle size range is greater.The relative peak concentration of heavy metals ions in the effluent will increase,the promotive effect of silicon powder with a large particle size range is weaker.The change of heavy metal concentration can hardly affect the residual concentration and median particle size of silicon powder at each migration distance,but the residual concentration of heavy metal will increase at each migration distance.Therefore,the increase of the concentration of injected heavy metals will hardly affect the average migration distance of silicon powder,but will increase the average migration distance of heavy metals.