Preparation Of Bentonite Composing EDTA Calcium And Its Remediation Effectiveness Of Heavy Metals In Soil Around A Lead-zinc Mining Area

Mining exploitation and utilization of bonus for economic development at the same time led to the heavy metal pollution.Heavy metal pollution is various and biotoxic synergy,when it enter the soil and water in the form of ions,with migratory and refractory characteristics,through the way of food chain eventually threaten human health,therefore,environmental heavy metal pollution remediation and treatment,avoid heavy metal pollution threaten human health is one of the focus of attention.Among them,chemical passivation remediation method is a commonly used remediation technology,mainly through adsorption,precipitation,complexion,ion exchange,red-ox and other methods to change the activities of heavy metals,so as to effectively reduce the migration ability and bio toxicity of heavy metals.Modified bentonite as a clay mineral has a good adsorption to soil heavy metals,can maintain the original soil structure,and has a certain role in restoring soil function.In this paper,bentonite composing EDTA calcium heavy metal passivation material were prepared on the basis of hydrochloric acid-modified bentonite,and the surface properties of passivation materials were analyzed by FT-IR,XRD and SEM,and studied the removal effect and adsorption mechanism of bentonite composing EDTA calcium on Cd,Pb,Cu and Zn under water environment.In Guizhou Bijie city Hezhang a lead-zinc contaminated soil as a test object,add different proportion of bentonite composing EDTA calcium treatment,study the soil cation exchange amount,heavy metal effective state and the content of each occurrence form change and the influence of soil enzyme activity,determine the best proportion,provide scientific basis for soil heavy metal remediation.The main research findings of this paper are as follows:(1)EDTA modification increases the specific surface area of bentonite,which is comparable to that of hydrochloric acid-modified bentonite;the crystal structure of EDTA-modified bentonite is not changed,and the crystal structure is stable.(2)The adsorption of Cd,Pb,Cu and Zn by bentonite composing EDTA calcium conforms to the Langmuir isotherm model and pseudo-secondary kinetic equation,which are spontaneous heat absorption reaction.The higher the temperature of the solution system,the more conducive to adsorption.The size order of heavy metal adsorption by bentonite composing EDTA calcium was Pb>Zn>Cu>Cd,and the adsorption type was mainly chemicorbent.(3)EDTA calcium-based bentonite shows a certain fixed effect on soil heavy metals.Among them,when the applied amount is 0.5%?5%,the effective state content of Cd decreases significantly,promoting the conversion of acid extractable state and reducing state to residue state,and has a better effect on the fixation of Cd.The amount of soil cation exchange decreased with the amount of bentonite composing EDTA calcium applied,but the decrease can be ignored.The activity of soil sucrase and urease with the amount of bentonite composing EDTA calcium shows a tendency to decrease first and then increase,while acid phosphatase increases with the amount,and catalase activity is significantly reduced when the amount of bentonite composing EDTA calcium exceeds 5%.In conclusion,bentonite composing EDTA calcium has a large specific surface area,stable crystal structure and characteristics-welled.It also has good adsorption properties for heavy metals,and can inhibit the activity of soil heavy metals.The effects on soil cation exchange amount and soil enzyme activity are within the acceptable range,which can be suitable for remediating heavy metal contaminated soil and has broad application prospects.