Preparation And Application Of Nanoscale Zero-Valent Iron

Nanoscale zero-valent iron?nZVI?refers to zero-valent iron particles with particle size in the range of 1 to 100 nm.Nanoscale zero-valent iron material has the characteristics of inexpensive,high reaction activity,high specific surface area and excellent adsorption and reactivity properties.The current research interest is focused on this type of material due to its excellent performances in various environmental pollutants?e.g.heavy metals,inorganic anions,radioactive elements,halogenated organic compounds,nitroaromatic compounds and endocrine-disrupting chemicals?remediation through different degradation mechanisms.Hence it has been regarded as a new material that having broad application prospect,and has has been widely studied in the field of environmental area.However,there are still some problems to be solved in practical applications,such as difficult to control the synthesis conditions,easy agglomeration and poor air stability.These factors have posed a serious challenge to the preparation and application of nanoscale zero-valent iron material.In this paper,nanoscale zero-valent iron was prepared by carbothermal method and green synthesis.The effects of surpports,loading,calcination time,calcination temperature and additives on the preparation of highly dispersed nanometer zero iron by the two methods were investigated.The prepared nanoscale zero-valent iron was used for the removal of heavy metal ions in water,and the effects of different reaction conditions on the reaction process were investigated.The results show that:the carbothermal method can not prepare highly dispersed nanoscale zero-valent iron,nZVI/AC,at relatively low temperature.The addition of KNO₃ can promote the process of carbothermal reduction and improve the product dispersion,wherein the particle size of Fe⁰ is about 50⁶0 nm.nZVI prepared by one step of green synthesis was amorphous,while two-step green synthesis,incorporated with carbothermal method,can efficiently in suit generate green surpport loaded highly dispersed nanoscale zero-valent iron,nZVI/GS,in which zero-valent iron is crystalline and pure,and the size of Fe⁰ particle is about 10¹5 nm.Nanoscale zero-valent iron has a high removal activity for heavy metal ions in water,and the reactivity to remove heavy metal ions from water was greatly affected by the reaction conditions.The removal rate of Pb???in water increased with the dosage of nZVI/AC.When solution initial pH=5⁶ and initial Pb???concentration was 300 mg·L^-1,the removal ratio can reach more than 98%if reaction at 20?for30 min.Acid or weak acid condition was favorable for nZVI/AC to remove Pb???in water.nZVI/GS can also efficiently remove heavy metal ions from water,and the removal ratio of single Pb???,Cr???or multiple heavy metal ions was close to100%under the experimental conditions.