Study On Remediation Of Cadmium,lead And Copper In Water/Soil Environment By Ball Milling Calcium-based Fly Ash

With the rapid development of industrialisation,heavy metal pollution is a serious threat to the social environment and human health,and is usually difficult to manage.Adsorption and passivation remediation are the most promising remediation techniques for heavy metal pollution,as they are simple to operate and economically efficient.Most of the existing remediation materials are costly and the remediation effect needs to be improved,therefore,the search for a green,economical and efficient remediation material has become a hot topic of research.Fly ash,as a solid waste,has some adsorption potential for the heavy metals cadmium(Cd),lead(Pb)and copper(Cu),although it contains a large number of active sites such as aluminium and silicon,but the adsorption performance still needs to be further improved.Therefore,the thesis took the fly ash of Huainan power plant as the research object,and ball-milled fly ash(BMFA)and ballmilled calcium-based fly ash(Ca-FA)were prepared by mechanical ball milling.The effects of modified fly ash on the adsorption performance of Cd,Pb and Cu under the effect of initial p H,adsorbent dosage,adsorption time and initial concentration of solution were investigated,combined with SEM-EDS,XRD,FTIR and XPS were used to investigate the adsorption mechanism of Cd,Pb and Cu in water.In addition,the effect of Ca-FA as a passivating agent on the passivation of Cd,Pb and Cu contaminated soil and its effect on the structure of microbial communities was investigated by soil incubation.The main findings are as follows.(1)Mechanical ball milling can break and separate the surface of fly ash from smooth spherical glass-like particles into rough porous structures,which increases the specific surface area and significantly improves its effect on the removal of heavy metals Cd,Pb and Cu.When p H=6.0,the adsorbent dosage was 0.05 g and the initial concentration was 60 mg/L,BMFA showed the best adsorption effect on Cd,Pb and Cu,and reached saturation within 60 min,240 min and 180 min,respectively.In addition,the quasi-secondary kinetic model and the Langmuir model could better describe the adsorption process of BMFA on Cd,Pb and Cu,indicating that the adsorption of BMFA on Cd,Pb and Cu was mainly chemical,and the maximum adsorption amounts were 19.57mg/g,13.98 mg/g and 3.15 mg/g,respectively.(2)Comparing with BMFA,the removal effect of Ca-FA on Cd,Pb and Cu was significantly improved when the Ca O addition ratio was 1%,and the removal rates reached 100%,98.7% and 99.9% respectively when the initial concentration of heavy metal solution was 60 mg/L.Under the optimum conditions of adsorption p H=6.0,the amount of adsorbent was 0.05 g and the initial concentration was 60 mg/L,the adsorption of heavy metals Cd,Pb and Cu by Ca-FA saturated within 480 min,720 min and 240 min,respectively,and their maximum adsorption amounts were 54.14 mg/g,119.76 mg/g and63.48 mg/g,respectively.(3)The addition of different passivating agents(FA 1%,FA 3%,FA 5%,Ca-FA 1%,Ca-FA 3%,Ca-FA 5%)to the soil increased the p H,EC and effective state Ca content of the soil after 48 days of incubation and changed the soil physicochemical properties,resulting in a significant reduction in the effective state of the heavy metals Cd,Pb and Cu.Combined with SEM,XRD,FTIR and XPS characterisation,the passivation mechanism of Ca-FA on heavy metals Cd,Pb and Cu included physical adsorption,electrostatic adsorption,ion exchange,precipitation and ligand complexation,with the ligand complexation reaction playing a dominant role.(4)The addition of both the passivators FA and Ca-FA caused changes in the composition of the soil microbial community,increasing its diversity and relative abundance,with the passivator Ca-FA 3% treatment significantly increasing the Alpha diversity of the soil microbial community,while the Ca-FA 5% treatment differed significantly from the other treatments in terms of soil microbial community structure and had the greatest impact on the soil microbial community.Too much passivate can have a toxic effect on the soil microbial community,so the amount of Ca-FA added should be limited to 3%.p H,EC,active Ca,Cd,Pb and Cu are the factors influencing the change in soil microbial community structure between treatments,with p H and EC playing a decisive role.Figure [35] Table [16] Reference [120]...