| Cadmium,chromium,and p-nitrophenol?4-NP?are among the 25,043 chemicals that have been registered as toxic substances by the United States Environmental Protection Agency in 1973.They have long-term threat to human health and ecological environment.Hence,the sequestration of these contaminants is extremely urgent.In this thesis,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,the obtained nZVI/SC was then sulfided by sodium sulfide to enhance the stability and reactivity of nZVI and resulted in the yeast supported sulfide-modified nanoscale zerovalent iron?S-nZVI/SC?.The application of the as-prepared S-nZVI/SC in the sequestration of Cr???and Cd???,as well as the sequestration of 4-nitrophenol?4-NP?were investigated also.The results are as follows.?1?The sequestration capability of nanozero iron for Cr???increased distinctly by sulfuration.The most effective S-nZVI/SC for Cr???sequestration was synthesized by the sulfuration of 1.40 mmol sodium sulfide.The sequestration rate of 6.00 mL 150.0 mg·L-1Cr???by 15.0 mg of S-nZVI/SC increased from 18.45%to 97.23%after the sulfuration of1.40 mmol sodium sulfide.This S-nZVI/SC can keep stable at room temperature for 5 d.?2?The sequestration efficiency of Cr???by S-nZVI/SC decreases with the increase of pH,and increases with the increase of the dosage of S-nZVI/SC,while the temperature and ionic strength have no significant effects on Cr???sequestration.The Cr???sequestration by S-nZVI/SC follows the pseudo-first-order kinetic model,25.00 mL of 5.0 mg·L-1Cr???were be removed within 15 min by 10.0 mg of S-nZVI/SC under the the condition of pH6.0 and 25?,and the rate constants kobs were 1.787±0.002 h-1?1.646±0.005 h-1 and1.155±0.008 h-11 for 10.0 mg·L-1,20.0 mg·L-1 and 25.0 mg·L-1 of Cr???with corresponding R2 of 0.8559,0.9566 and 0.9496,repectively.?3?The sequestration efficiency of nZVI/SC on Cd???increased 2.63 times after sulfuration.The Cr???sequestration rate of S-nZVI/SC increased with the increase of temperature and the dosage of S-nZVI/SC,but decreased with the initial concentration of Cd???.Cd???can be removed by S-nZVI/SC in a wide pH range,and the sequestration rate of Cd???was almost invariability within pH value form 3.0 to 9.0.The sequestration rate of5.00 ml 500.0 mg·L-1 Cd???by 15.0 mg of S-nZVI/SC increased from 82.70%to 98.08%at pH 6.0 as the temperature increasd from 25?to 45?.?4?The yeast supported nZVI can be used to sequestrate 4-NP in aqueous solution,but sulfuration showed some inhibitory effect on 4-NP sequestration.The sequestration rate of4-NP increased with the dosage of nZVI/SC,and it showed temperature depended.The maxium sequestration rate of 4-NP was obtained under 35?,with a sequestration rate of90.81%within 0.5 h when 0.042 mmol·L-1 4-NP was sequestrated by 40.0 mg of nZVI/SC at pH 4.0. |
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