Study On Modification Of Fly Ash And Its Application In Acid Mine Drainage

The mining process is accompanied by the production of acidic mine water,which usually contains a variety of heavy metal ions,such as zinc,copper and other heavy metal ions.At the same time,industrial solid waste,such as steel slag and fly ash,will be produced in the industrial production process.In this paper,industrial solid waste is used to treat acidic mine water in order to achieve the purpose of waste treatment.Modified fly ash was prepared with fly ash as active matrix and Na2CO3 as modifier by pyrometallurgical modification at 800 C.Through static adsorption experiments of FA and MFA on Cu2+ and Zn2+,the optimum adsorption conditions and adsorption properties were determined by single factor experiments:The adsorption kinetics and isothermal adsorption model of fly ash for Cu2+,Zn2+ were analyzed.The adsorption effect of FA,MFA,MFA and steel slag on Cu2+ and Zn2+ in simulated acidic mine water was studied by dynamic adsorption experiment of permeable reaction wall.In the static adsorption experiment,the single factor results show that MFA is better than FA in the treatment of simulated wastewater.For Cu2+ solution with a volume of 100mL and a concentration of 10mg/L,when the temperature was 30 C,the best conditions were:dosage of MFA was 0.2g,pH>4,reaction time 60min.At this time,the adsorption amount of MFA to Cu2+ was 4.80mg/g,and the removal rate was 96.00%.For Zn2+ solution with a volume of 100mL and a concentration of 10mg/L,when the temperature was 30 C,the best conditions were:dosage of MFA was 0.4g,pH>6,reaction time 60min.At this time,the adsorption amount of MFA to Zn2+ was 2.44mg/g,and the removal rate was 97.660%.The adsorption process of MFA to Zn2+ and Cu2+ is in accordance with the two-stage dynamic simulation,R2 is higher than 0.98 at three different temperatures,and the significance of second-order kinetics fitting is higher than that of first-order kinetics fitting and Weber-Morris internal diffusion equation fitting,and the calculated qe is close to the measured value,which indicates that the adsorption process is mainly controlled by chemical adsorption.Freundlich adsorption isothermal model and Langmuir adsorption isothermal model can fit the adsorption process of MFA to Cu2+ and Zn2+ well,but the correlation coefficient of Freundlich adsorption isothermal model is higher than that of Langmuir adsorption isothermal model at the same temperature.That is to say,the isothermal adsorption process of MFA to Cu2+ and Zn2+ is more in line with Freundlich adsorption isothermal model,which indicates that the adsorption process of MFA to Cu2+ and Zn2+ may be multi-layer adsorption.The adsorption amount increases with the increase of temperature,which indicates that the adsorption process is heat absorption reaction,and heating is beneficial to adsorption of MFA to Cu2+ and Zn2+.In the dynamic adsorption experiment of PRB,PRB operated for 19 days under the condition that the experimental temperature was 8?14? and the inlet pH was 3.The removal rate of three PRB to Cu2+ and Zn2+ was close to 100%in the running 20h,and the removal rate decreased gradually between 20?200h,and stabilized after running 200h.Among them,between 20 and 200 hours,the removal rate of Zn2+ by PRB ? with FA as filler ranged from 5.35%to 39.76%,and that of Cu2+ ranged from 48.04%to 88.91%.The removal rate of Zn2+ by PRB ? with MFA as filler ranged from 30.26%to 80.22%,and the removal rate of Cu2+ was close to 100%.The removal rates of Zn2+ and Cu2+ by PRB ? with MFA and steel slag as fillers ranged from 27.81%to 72.39%,and that of Cu2+ ranged from 98.94%to 99.99%.The removal rates of Cu2+ and Zn2+ by the three fillers are:MFA>steel slag and MFA mixture>FA.Three PRB have a certain regulating effect on the pH of wastewater,water intake pH is 3,effluent pH>6.65,simulation PRB experimental results show that modified fly ash as adsorption medium is applicable to acid mine drainage treatment.