Basic Research On The Application Of Phosphorus Compounds To Passivation Of Uranium And Associated Heavy Metals In Contaminated Tailing

This paper focuses on the passivation and remediation of uranium and associatedheavymetal-contaminatedsoilsbyphosphorus-containing compounds.Through greenhouse pot control experiments,nano-hydroxyapatite?NHAP?,superphosphate?SSP?and potassium dihydrogen phosphate?KH₂PO₄?are used as The experimental materials were screened for phosphate fertilizers with good uranium passivation effect.Field experiments were conducted in uranium tailings area,and high biomass uranium-enriched plants Medicago sativa L.and Rumex acetosa L.were used as test sites.Demand plants were used to analyze the effects of different types and doses of phosphorus-containing compounds on the growth and uranium enrichment characteristics of different plants under uranium and associated heavy metal stress in the tailings area,and on the effects of different chemical forms of uranium and associated heavy metals on the soil.Provide a certain reference for the treatment of radionuclides contaminated soil and environmental restoration.The main conclusions are as follows:?1?In pot experiment,adding phosphorus compounds can significantly promote the growth of plants.It is best to add SSP to promote plant growth.Compared with the control group,the addition of SSP,KH₂PO₄,and NHAP to the original polluted soil reduced the uranium content of the alfalfa by 21.16%,40.59%,and 36.61%,respectively;in the soil with a simulated U pollution amount of 25 mg·kg^-1,SSP was added.The contents of uranium in alfalfa plants were reduced by 76.68%,89.67%and 74.95%respectively by KH₂PO₄ and NHAP.Uranium contents in alfalfa plants were reduced by adding SSP,KH₂PO₄and NHAP,respectively,in simulated U-pollution levels of 50 mg·kg^-11 soil.66.33%,81.07%,86.78%.In terms of all three uranium-contaminated soils,KH₂PO₄ has the best effect on reducing uranium enrichment in plants.The three phosphorus-containingcompoundssignificantlyreducedthecontentof ion-exchanged uranium and carbonate-bound uranium in the soil,ie,the effective uranium content decreased by 94.81%to 1.92%,and the KH₂PO₄decreased most,indicating that the phosphorus-containing compounds are mainly Reduce the migration of uranium into plants by reducing the uranium content in the soil.Comparing the three concentrations,it was found that the effect of reducing uranium content in simulated uranium-contaminated soil at 25mg·kg^-11 was the best,which reduced the effective content by 64.14%.?2?In the uranium tailings field test,compared with CK,when the P application rate was 7 g/m²,the dry matter quality of alfalfa roots,stems and leaves,and whole plants reached 0.30,2.19,and 2.49 g.The increase was57.89%,217.39%,and 186.21%,respectively.At 7 g/m²,the dry weight of stems and leaves and whole plants reached 1.38 and 2.41 g^-1,respectively,an increase of 109.01%and 72.14%,respectively,compared with CK.The most obvious increase was observed.Compared with CK,the application of NHAP at a concentration of 9 g/m² reduced the uranium content by 82.93%compared to the control group.When the KH₂PO₄ dose was 5 g/m²,the plant roots,stems and leaves,and the entire uranium of the plant were used.The content of uranium was lower than that of the control group,and the uranium content decreased by71.16%,64.64%,and 72.74%,respectively.The uranium content of the plant decreased significantly after application of NHAP.When the P application rate was 7 g/m²,the root uranium content decreased significantly,and the uranium content decreased by 48.62%.Alfalfa had better manganese absorption capacity than the sour model.When NHAP was applied at 7 g/m²,the effect of inhibiting Mn uptake by the two plants was most significant,and the transfer coefficients were all greater than 1,and the transfer coefficients of the sorrel were 5 g/m²when NHAP was applied and 9 g/m² when KH₂PO₄ was applied.The TF values were 7.69 and 6.24,respectively;the effect of the two phosphorus-containing compounds on the absorption of cadmium by the sour model was KH₂PO₄>NHAP,but when the alfalfa was used,it was NHAP>KH₂PO₄,and the best when the phosphorus application was 7 g/m²;Compared with CK,when the application of NHAP was 9 g/m²,the arsenic content of alfalfa plants was the lowest,which was 77.27%lower than that of CK.When the application of KH₂PO₄ concentration was 7 g/m²,the arsenic concentration in the underground and whole plants of both plants reached.At the lowest value,TF showed different changes.The TF values of the sour models were all greater than 1,and the arsenic transport capacity was strong.The comparison of the two phosphate fertilizers showed that KH₂PO₄ was superior to NHAP in inhibiting arsenic uptake by plants.?3?Under field conditions,verification of the reduction of uranium content by two phosphorus-containing compounds is due to the fact that phosphate fertilizers reduce the content of available uranium and associated heavy metals in the soil and increase other forms that are not easily absorbed by plants.The results show that:NHAP can effectively increase the p H value of the soil in the tailings area,KH₂PO₄ reduces the p H value of the soil is not significant;when the application of KH₂PO₄ is 9 g/m²,the effective uranium content of the soil is the lowest,the average effective uranium content is reduced by 40.84%;the application of NHAP is in 7 At g/m² and 9 g/m²,the cadmium content was reduced by 0.269 mg·kg^-11 and 0.330 mg·kg^-1,respectively,compared to the control group.KH₂PO₄ had no significant effect on the effective cadmium in the soil;the application of NHAP was 5 g/m².Passivation works best.Under KH₂PO₄ treatment,the Mn forms in the soil were mainly transformed from the acid-soluble and residual state to the reducible and oxidizable state;when the KH₂PO₄ dose was 9 g/m²,the effective arsenic reached the lowest value,and the two phosphate fertilizers were found to be high.The concentration of KH₂PO₄reducestheeffectivearsenicratiobetterthanNHAP.Insummary,phosphorus-containing compounds have a good passivation effect on uranium and associated heavy metals contaminated soil in the tailings area,and can provide a reference for the treatment of radionuclides.