| The pollution problem of lead-zinc tailings ponds has been around for a long time,and the threat to human production,life and health has received much attention.Chemical-plant joint repair is an effective method for the repair of heavy metals.This paper mainly discusses the effect of organic and inorganic combination modifiers on the repair of lead and zinc tailings slag and the effect of Oleander on the absorption of heavy metals.Through the beaker cultivation experiment,four kinds of inorganic modifiers dolomite,calcium carbonate,sepiolite,bentonite,four kinds of organic improver mushroom residue,peat soil,wheat biochar,rice husk biochar were used to repair the lead-zinc slag.Two inorganic improvers,dolomite and calcium carbonate,and two organic improvers,peat soil and mushroom residue,were screened out.Through the beaker cultivation experiment,the repairing effect of organic and inorganic combination modifier on lead-zinc slag was studied.Through pot experiment,the effects of organic improver and inorganic improver on the content of heavy metals in lead-zinc slag and the control effect of Oleander on Pb and Zn were studied under the conditions of single application and organic and inorganic combination improvement.Finally,the best organic and inorganic combination improver(mushroom residue+calcium carbonate)and its ratio(1:1)and addition amount(10%)were selected.The experiment mainly yields the following results:I.Effect of single modifier on Pb and Zn forms and potential environmental risks in lead-zinc slag(1)Both the inorganic modifier and the organic modifier can increase the pH value of the slag to different degrees,and increase with the increase of the modifier.The pH increase of the 15%addition of calcium carbonate in the inorganic modifier is the largest.In the organic improver,the pH increase value of the wheat biochar 30%added amount is the largest.(2)The inorganic modifier can reduce the iron-manganese combined state and organic binding state of Pb and Zn in the matrix and increase the residual state.The maximum increase of Pb and Zn residual state occurred in the treatment of calcium carbonate,which were 32.81%and 42.41%,respectively.(3)The organic improver can reduce the acid extractable state of Pb and Zn in the matrix,and the order of reduction is as follows:mushroom residue>peat soil>rice husk biochar>wheat biochar,the maximum decrease is 31.12%,12.66%,respectively.(4)Correlation analysis of Pb and Zn in the slag after improved treatment showed that the modifier with extremely significant or significant increase in the residue state was dolomite,calcium carbonate in the inorganic modifier,peat soil in the organic modifier and Mushroom residue.(5)The potential environmental risk index of Pb and Zn decreased in the four inorganic modifiers.In the four organic improvement treatments,the potential environmental risk index in peat soil and wheat biochar treatment decreased,and the treatment of rice husk biochar and mushroom residue increased.II.Effect of combined improver on Pb and Zn forms and potential environmental risks in lead-zinc slag(1)The combination improver can increase the pH value of the slag to different degrees,and the combined improvement effect is superior to the M+C and N+C combination of 1:1 ratio.(2)The combination improver can increase the organic matter content in the slag,and the organic matter content of all the combinations of 1:1 ratio is significantly increased,and the best effect is the N+C combination.(3)The ratio of the combination of improver to DTPA-Pb and Zn in slag is 2:1>1:2>1:1,and the best combination for reducing DTPA-Pb content is N+C.For DTPA-Zn is M+C.(4)The combination modifiers increased the content of Pb and Zn in the residual state,and the maximum increase was 20.20%and 43.70%,respectively.The stability effect on Pb was better than M+B and N+C.The combination is opposite to Zn.In general,the stability of the 1:1 ratio of the three ratios is better.(5)Combination modifiers can reduce the potential ecological risk index of Pb and Zn in slag,and the ecological risk index of Zn decreases more than Pb.Ⅲ.Study on the phytoremediation effect of single improved lead-zinc slag(1)Both modifiers have significant effects on the pH value of the slag.The improvement effect of calcium carbonate is better than that of mushroom slag,and the increase of the modifier concentration can significantly increase the pH value in the slag.(2)The addition of two modifiers can effectively increase the organic matter content in the slag,and the increase of mushroom slag concentration has different effects on the organic matter content in the slag.The improvement effect of mushroom slag is better than that of calcium carbonate.(3)Both modifiers can effectively increase the activity of phosphatase and catalase in slag,and the effect of mushroom residue is more significant.The increase in the concentration of mushroom slag has a significant effect on the increase of phosphatase activity,and the increase in the concentration of calcium carbonate has a significant effect on the increase of catalase activity.(4)Both modifiers and their concentration increase can promote the conversion of Pb,Zn,Cu and Cd from unstable state to stable organic combined state and residual state in slag and improve the degree of stabilization.The degree of stability is Pb,Zn>Cd,Cu,and the mushroom slag effect is better than calcium carbonate.(5)Both modifiers can increase the biomass of oleander,and the effect of mushroom slag is better than that of calcium carbonate.The content and accumulation of Pb and Zn in each organ of oleander showed a trend of root>stem>leaf,and Zn was significantly higher than Pb.The addition of mushroom residue can increase the accumulation of Pb and Zn while reducing the content of Pb and Zn in each organ of oleander.(6)The two modifiers can reduce the enrichment of Pb and Zn by oleander.The increase of the modified concentration will increase the enrichment of Pb and Zn,but the effect is not significant.The improvement of calcium carbonate makes the ability of oleander to migrate Pb and Zn from the lower part to the upper part of the ground,and the migration ability to Pb is stronger than that of Zn.The effect of mushroom residue is opposite;the increase of the concentration of improver will reduce the oleander.Calcium carbonate improvement improves the transfer coefficient of oleander to Pb,and reduces the transfer coefficient of Zn.The effect of mushroom slag is opposite.Ⅳ.Study on the phytoremediation effect of combined improved lead-zinc slag(1)Both combination improvers can increase the pH value of slag to a certain extent,but the effect is not significant.The two combination modifiers have significant improvement effects on the slag structure,and the combination of mushroom slag and calcium carbonate is better than the combination of peat soil and calcium carbonate.(2)The addition of the two combination modifiers can increase the activity of phosphatase and catalase in the slag,and the effect is remarkable.The combination of mushroom slag and calcium carbonate is better than the combination of peat soil and calcium carbonate.(3)The addition of two combination modifiers can effectively reduce the Pb and Zn extracted from DTPA in slag,and the combination of mushroom slag and calcium carbonate is better than that of peat soil and calcium carbonate.The two combination modifiers are better than DTPA-Zn in reducing DTPA-Pb.(4)Both combination modifiers can promote the conversion of Pb and Zn from unstable form to stable organic combined state and residual state,and the stability of mushroom slag and calcium carbonate is better than that of peat soil and calcium carbonate.The two combination modifiers have stronger stabilization effect on Zn than Pb.(5)The two combination modifiers have significant effects on the biomass of oleander,and the improvement effect of mushroom slag and calcium carbonate combination is better than that of peat soil and calcium carbonate.The addition of two combination modifiers can reduce the content of Pb and Zn in the organs of oleander,and the content of Pb and Zn in the organs of oleander is root>stem>leaf in the treatment of the two combination modifiers.The Zn content and the cumulative amount are substantially higher than the Pb content.(6)After the combination of the two combinations,the enrichment ability of oleander to Pb and Zn decreased,and the ability of oleander to transfer Pb from the underground to the shoot was reduced.Both combination modifiers can increase the Pb and Zn transfer coefficient of oleander,and the transfer coefficient of mushroom slag and calcium carbonate combined treatment is higher than that of peat soil and mushroom residue. |
