摘要
采用液相还原法制备了纳米铁,并用X射线衍射仪(XRD)、扫描电镜(SEM)对其晶体结构、形貌特征进行了表征.以Cr(Ⅵ)为模拟污染物,中压汞灯作为光源,考察了不同投加量、不同pH值等条件下光照对纳米铁还原Cr(Ⅵ)的影响.结果表明:制备的纳米铁具有很高的反应活性,粒径约为7.6nm,呈球形,可在空气中自燃.在25℃、Cr(Ⅵ)浓度为20mg/L、pH=7±0.5,加入0.1g的纳米铁,光照60min后Cr(Ⅵ)的还原率达到62.3%,而无光照时Cr(Ⅵ)的还原率仅为27.6%,说明光照对Cr(Ⅵ)的还原具有明显的促进作用.当纳米铁投加量较大时,纳米铁对Cr(Ⅵ)的还原速率大于光照对其产生的影响.反应液pH值对Cr(Ⅵ)还原速率的影响较光照对其产生的影响显著.在紫外光的照射下,纳米铁中电荷可能在诱导下作受迫振荡,与吸附分子发生电荷传递是光照促进纳米铁还原Cr(Ⅵ)的主要原因.
Nanoscale zero-valent iron （NZVI） was synthesized in aqueous solutions by reduction of Fe3＋with NaBH4. The crystal structure and morphology features of the samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, respectively. The reduction rate of the Cr（Ⅵ） was investigated to understand the effect of irradiation of medium pressure mercury lamp on reduction of Cr（Ⅵ） with NZVI, and the effects of irradiation under the conditions of different dosages and pH values. The experimental result showed that nano iron has high reaction activity, and its particle size was about 7.6nm and spontaneously flammable in air. With the initial Cr（Ⅵ） concentration of 20mg/L, pH=7±0.5 and a temperature of 25℃ and NZVI dosage of 0.1g, the reduction rate of Cr（Ⅵ） reached 62.3% under the action of irradiation for 60 minutes while it was only 27.6%without irradiation. The irradiation process played a role in promoting the reduction efficiency of Cr（Ⅵ） at less dosage of NZVI but the effect of reducing action was greater than that of irradiation when the dosage of NZVI was enough. The pH value had a more obvious effect than the irradiation on removal rate of Cr（Ⅵ）. The charge in nano iron may be oscillated by the irradiation of ultraviolet light and transferd to the adsorbed molecular, which explained the irradiation promoted reduction of nano iron Cr （VI）.
出处
《中国环境科学》
EI
CAS
CSCD
北大核心
2014年第10期2562-2567,共6页
China Environmental Science
基金
国家自然科学基金资助项目(51268026,51068016)
关键词
纳米铁
光照
CR(VI)
还原
nanoscale zero-valent iron （NZVI）~ irradiatiom Cr（VI）
reduction
