Modified Sepiolite On Pb-contaminated Soil Passivation Repair Effect Research

As a kind of clay mineral,Sepiolite is characterized by its low price and easy exploitation.It can be used to control water weight metal pollution and soil heavy metal pollution.It is often used as a passivator in heavy metal sorbents in water and in situ passivation repair of soils.However,the shortcomings of natural sepiolite,such as low load capacity and small metal binding constant,limit the adsorption properties of sepiolite on heavy metals.Proper treatment of sepiolite can improve its adsorption and complexing ability to heavy metals.In this study,natural sepiolite was used as raw material,and modified sepiolite was prepared by using ferrous sulfate,thioglycolic acid and heat treatment.Analysis of the characterization of modified sepiolite,and study on the adsorption characteristics of sea blisters on Pb²⁺in solution.The modified sepiolite and natural sepiolite were used as passivation repairing agents for Pb-contaminated soil.The BCR continuous extraction method and DTPA extraction method were used to determine the distribution of Pb in various forms and the content of available Pb in soil.The effects of sepiolite on Pb form distribution and plant availability Pb in Pb-contaminated soil were studied to analyze the passivation effect of sepiolite on Pb in target contaminated soil.The results show:?1?The specific surface area of sepiolite is F-SEP>Q-SEP>R-SEP>SEP,and the surface structure of Q-SEP and F-SEP and Q-SEP is broken,showing the accumulation of bundle structure.The surfaces of R-SEP and SEP are relatively smooth.The surface adsorbed water of F-SEP,Q-SEP and R-SEP is reduced relative to SEP.?2?The adsorption amount of Pb²⁺by sepiolite increased with the initial concentration and time of Pb²⁺solution,and it was close to equilibrium at 120min.Among them,F-SEP has the highest adsorption rate for Pb²⁺,followed by R-SEP and SEP.At the same initial concentration,the adsorption amount of sepiolite to Pb²⁺was:F-SEP>R-SEP>Q-SEP>SEP.The Langmuir isotherm adsorption model and quasi-secondary kinetic model can better reflect the adsorption of Pb²⁺by sepiolite.The adsorption of Pb²⁺by sepiolite is monolayer adsorption.?3?The pH value and cation exchange amount of the soil added with sepiolite increased,and the soil organic carbon content did not change significantly.The content of acid extracted Pb and reducible Pb in soil decreased,and the content of acid extracted Pb in soil treated by 15%Q-SEP decreased the most.There is a significant increase in the Pb content in the residual state.The migration ability of Pb in the soil of four sepiolites is represented by Q-SEP<R-SEP<F-SEP<SEP.?4?Sepiolite reduced the available Pb content in Pb-contaminated soil,and the soil available Pb content decreased by 15%Q-SEP.The passivation effect of sepiolite on acidic soil is better than that of alkaline soil.The soil available Pb,acid extracted Pb and oxidizable Pb were significantly negatively correlated with soil pH,and positively correlated with residual Pb.Soil pH was an important factor affecting the effect of sepiolite on Pb passivation.The increase in pH has a positive effect on the passivation effect of Pb.