Preparation Of Yeast Supported Sulfide-Modified Nanoscale Iron And Its Capability For Lead(?) And Cadimum(?) Removal

The pollution of lead and cadmium in water and soil in our country is serious.Changing the occurrence form of lead and cadmium and reducing its bioavailability is one of the effective ways to control lead and cadmium pollution.In this thesis,the yeast supported nanoscale zerovalent iron(nZVI/SC)was first synthesized by the in situ reduction of ferrous by sodium borohydride with S.cerevisiae as stabilizer and dispersing agent,and then sulfided by sodium dithionite.The resulted sulfide-modified nanoscale zerovalent iron(S-nZVI/SC)was used for the removal of lead and cadmium in water and soil.The main results are as follows:(1)The sequestration capability of nanozero iron for Pb(?)increased distinctly by sulfidation.The most effective S-nZVI/SC for Pb(?)sequestration was synthesized by the sulfidatiion of 25.6 mmol sodium dithionite.The removal rate of 100.0 mg·L^-1 Pb(?)by 0.29g·L^-1 of S-nZVI/SC increased 3.5 times,with a removal amount of 261.5 mg·g^-1.Pb(?)removal was not affected by temperature and pH,but the removal amount of Pb(?)decreased with the increase of ionic strength.(2)The Cd(?)removal mount of nZVI/SC increased 30.0%after the sulfidatiion of 25.6mmol sodium dithionite.Cd(?)removal was not affected by temperature,but the removal amount of Cd(?)decreased with the increase of ionic strength.The maximium Cd(?)removal of 4.21 mg·g^-1was obtained with 20.0 mg·L^-1 Cd(?)treated by 3.0 g·L^-1 of S-nZVI/SC under the condition of pH 6.0.(3)The S-nZVI/SC treatment can effectively reduce the bioavailability of lead contaminated soil.After 60 days of co-incubation of 535.0 mg lead per kg lead contaminated soil with 2.0%S-nZVI/SC,the soil exchangeable lead fraction decrease 40.3%,while the soil reducible,oxidizable and residue lead fraction increased by 3.4%,139.2%and 37.4%,respectively.The lead activity index decreased from 13.5%to 7.4%.(4)The S-nZVI/SC treatment can effectively reduce the bioavailability of cadmium contaminated soil.After 60 days of co-incubation of 2.49 mg cadmium per kg cadmium contaminated soil with 2.0%S-nZVI/SC,the soil exchangeable cadmium fraction decreased74.4%,while the soil reducible,oxidizable and residue cadmium fraction increased by 19.2%,180.0%and 41.6%,respectively.The cadmium activity index decreased from 44.4%to 8.5%.