Preparation And Effect Of Acid Modified Attapuligite Heavy Metal Immobilizing Agents

Soil is the main natural resource for human survival,and is an important part of human ecological environment.With the rapid development of industry and agriculture,heavy metal pollution in soil plant environment system is becoming more and more serious.In recent years,whether in China or in the world,how to control and reduce the pollution and harm of heavy metals in the environment has become an increasingly prominent problem.In this paper 49 kinds of acid modified attapulgite immobilizing agents were prepared on using attapulgite as raw materials,according to the different acid modification time of 12 h,24 h,36 h,48 h,72 h,96 h and 108 h,different H₂SO₄ volume fraction of 2.5%,5%,7.5%,10%,12.5%,15%,20%.Five kinds of optimum acid modified attapulgite heavy metal immobilizing agents were selected by using heavy metal contaminated soil immobilization treatment and heavy metal enrichment experiment of maize plants.By the immobilization treatment of heavy metal contaminated soil,the passivation effect of acid modified attapulgite immobilizing agents on heavy metals in contaminated soil was analyzed.It is of great significance to study on immobilization remediation technology for heavy metal contaminated soil,it provides the basis for heavy metal remediation in large scale soil.And it provides a new approach to the development and application of products of local mineral resources.?1?The acid soluble state concentration of Cu,Cr,Zn and Ni of heavy metals decreased with the increase of acid treated H₂SO₄ volume fraction at first,and then increased.The acid soluble state concentration of Cu,Cr,Zn and Ni of heavy metals decreased with the increase of the acid modified time at first,and then increased.?2?Maize enrichment contents of heavy metal Cu,Cr,Zn,and Ni were significantly affected by different H₂SO₄ volume fraction.And maize enrichment contents of heavy metal Cu,Cr,Zn,and Ni were significantly affected by different acid modification time.?3?Five kinds of acid modified attapulgite S45,S54,S55,S56,S65 were selected.Acid modification conditions: H₂SO₄ volume fraction were 10%,12.5%,12.5%,12.5% and 15%,respectively.And acid modification time were 72 h,48 h,72 h,96 h,72 h,respectively.?4?The pH value of the heavy metal contaminated soil decreased with the increasing of the amount of immobilizing agents,but the pH value were lower than those in control group.The EC value of immobilization treatment groups were higher than those of the control group,the EC value of heavy metal contaminated soil increased with the increasing of the amount of immobilizing agents.?5?Water extractable contents of heavy metal Cu,Zn and Ni in contaminated soil decreased with the increasing of the amount of immobilizing agents.And they were significantly affected by different amount of immobilizing agents.When water extractable contents of heavy metal Cu,Zn and Ni reached their minima,they were 47.69%,63.17%,83.65% lower their control groups,respectively.?6?DTPA extractable contents of heavy metal Cu,Zn and Ni in contaminated soil decreased with the increasing of the amount of immobilizing agents.And they were significantly affected by different amount of immobilizing agents.When DTPA extractable contents of heavy metal Cu,Zn and Ni reached their minima,they were 23.31%,45.93%,61.45% lower their control groups,respectively.?7?With the increasing of the amount of immobilizing agents,acid soluble state Cu and reduced state Cu decreased,while oxidation state Cu and residual state Cu increased significantly.With the increasing of the amount of immobilizing agents,acid soluble state Zn and oxidation state Zn decreased,reduced state Zn and the residual state Zn increased significantly.With the increasing of the amount of immobilizing agents,acid soluble state Ni decreased,reduced state Ni,oxidation state Ni and residual state Ni increased significantly.The mobility of heavy metals was Cu>Zn>Ni.The mobility of heavy metals Cu,Zn and Ni in contaminated soil gradually decreased with the increasing of the amount of immobilizing agents.And mobility of heavy metals Cu,Zn and Ni were significantly affected by different amount of immobilizing agents.