The Study Of Utilizing The Heavy Metal Contaminated Soils As Resource

On the base of analyzing physical and chemical properties of containing As tailings(CZ)and leaching residue(FZ)、Pb/Zn/Cd compound contaminated soil in Baiyin,gansu province(BY),such as mineral composition,tailings particle size,heavy metal content and so on,this paper had studied the preparation process of non-fired brick and non-fired ceramsite.In this paper,the mechanism of strength formation of products had been studied by XRD,SEM,EDS etc dection means.In addition,the risk of heavy metals in products were evaluated.The research results are as beiow:By researching the non-burned bricks,it was analysed the effect which are dosage of raw materials,cementing materials and types of adsorbent,grain composition,molding pressure,moisture content.Results showed that : 1)The compressive strength of non-fired brick with ordinary portland cement as cementing material is about twice that of magnesia cement.2)The best grain composition is 1-2mm:2-4mm:4-5mm=1:1:2.3)The non-fired brick was made by containing As tailings: aggregate: cement: FM=60:23:15:2 or leaching residue: aggregate: cement: FM=60:23:15:2 or baiyin contaminated soil: aggregate: cement: hydroxyapatite=60:20:15:5.molding pressure is 15 MPa,water consumption is 12%,the combination property is the best.By researching the non-fired ceramsite,it was analysed the effect which are activator,fly ash,cement,light material,adsorbent,moisture content.Results showed that : 1)Fly ash should be used calcium oxide as activating agent,BY and CZ non-fired ceramsite,fly ash:calcium oxide=9:1,FZ non-fired ceramsite,fly ash:calcium oxide=6:1.2)The non-fired ceramsite was made by containing As tailings: cement: fly ash/calcium oxide: expanded perlite: FM=54%:15%:25%:4%:2%,water consumption 17% or leaching residue: cement: fly ash/calcium oxide: expanded perlite: FM=55%:18%:20%:4%:3%,water consumption 20% or baiyin contaminated soil: cement: fly ash/calcium oxide: expanded perlite: hydroxyapatite=48%:20%:25%:2%:5%,water consumption 17%,the combination property is the best.The heavy metals in products with a modified BCR procedure were studied.It was found that the content of acid extractable and reducible heavy metals in the products was greatly reduced,were existed in the form of oxidizable and residual state.The total amount oxidizable and residual state of As、Cd、Pb、Zn are 99.8%、94.3%、99.1%、89.2%.In addition,the risk of heavy metals in products were evaluated with the Hakanson.Analysis results showed that products was not harmful to the natural,but attention should be paid to the Cd.