海藻酸钠改性纳米零价铁还原土壤中Cr(Ⅵ)

Reduction of Cr(Ⅵ)in soil using sodium alginate⁃modifiled nanoscale zerovalent iron

采用液相还原法合成纳米零价铁(NZVI)及海藻酸钠改性纳米零价铁(SA⁃NZVI)去除土壤中的水溶性Cr(VI).X射线衍射图谱(XRD)、傅里叶红外变换图谱(FTIR)表征结果显示,利用海藻酸钠(SA)对NZVI改性能有效抑制NZVI的氧化;扫描电镜(SEM)表征结果显示,SA对NZVI有较好的分散性.实验结果表明,当海藻酸钠的添加量≤0.2%时,制备得到的SA⁃NZVI对Cr(VI)的去除率随着SA负载量的增加而递增;SA添加量>0.2%时,去除率随着SA负载量的增加而下降;SA添加量为0.2%时制备得到的SA0.2⁃NZVI对Cr(VI)的去除效果最优.随着材料投加量的增加和反应时间的延长,SA0.2⁃NZVI对土壤中水溶性Cr(VI)的去除率也随之提高.酸性条件更有利于SA0.2⁃NZVI去除土壤中水溶性Cr(VI).NZVI、SA0.2⁃NZVI、SA均对土壤中水溶性Cr(VI)有去除效果,去除率依次为SA0.2⁃NZVI>NZVI>SA.当土壤中初始Cr(VI)含量为288.11 mg·kg^-1,pH=8,投加量为0.4 g·L^-1时,反应2 h后SA0.2⁃NZVI对Cr(VI)的去除率可达到98.78%.

Nanometer zero⁃valent iron(NZVI)and sodium alginate modified nanometer zero⁃valent iron(SA⁃NZVI)were synthesized by liquid phase reduction method and employed for water⁃extractable Cr(VI)removal.X⁃ray diffraction(XRD),Fourier transform infrared spectroscopy(FT⁃IR),and scanning electron microscope(SEM)were used to characterize the SA⁃NZVI.The results showed that the NZVI modified by sodium alginate(SA)effectively inhibited the oxidation of NZVI.And NZVI had good dispersion with SA application.Additionally,the removal rate of Cr(VI)was positively correlated with the low SA addition(≤0.2%,m/m),while it negatively correlated with more SA addition(>0.2%,m/m).SA⁃NZVI prepared by 0.2%SA addition showed the greatest removal of Cr(VI)from soil.Increase of SA0.2⁃NZVI dosage and reaction time improved the removal of Cr(VI).Cr(VI)removal by SA0.2⁃NZVI was favored to acidic condition.NZVI,SA0.2⁃NZVI,SA could effectively decrease the water⁃extractable Cr(VI)in soil and the removal efficiency of Cr(VI)was in the following order:SA0.2⁃NZVI>NZVI>SA.98.78%Cr(VI)could be removed by SA0.2⁃NZVI within 2 h under initial Cr concentration of 288.11 mg·kg^-1,pH=8.0,vand SA0.2⁃NZVI dosage of 0.4 g·L^-1.