摘要
为考察Fe（Ⅲ）改性对生物质炭吸附水相中Cr（Ⅵ）的影响,采用吸附平衡试验结合Zeta电位、傅里叶变换红外光谱（FTIR）、X射线衍射法（XRD）等方法研究了Fe（Ⅲ）改性秸秆生物质炭对Cr（Ⅵ）的吸附作用及机制.结果表明,Fe（Ⅲ）通过与生物质炭表面官能团形成络合物及氢氧化铁表面沉淀的物理覆盖作用降低生物质炭表面负电荷,增加表面正电荷,从而促进生物质炭对Cr（Ⅵ）的吸附.Fe（Ⅲ）改性对花生秸秆炭吸附Cr（Ⅵ）的促进作用大于稻草炭,pH值为5.0时Fe（Ⅲ）改性分别使花生秸秆炭和稻草炭对Cr（Ⅵ）的最大吸附量提高79％和26％.在pH值为4.0～6.5范围内,生物质炭和改性生物质炭对Cr（Ⅵ）的吸附量均随悬液pH值升高而降低,Fe（Ⅲ）改性对生物质炭吸附Cr（Ⅵ）的促进作用也呈相似的变化趋势.改性生物质炭的表面负电荷随pH值升高而增加是Cr（Ⅵ）吸附量减小的主要原因.Cr（Ⅵ）可在改性生物质炭表面的同时发生静电吸附和专性吸附,Cr（Ⅵ）的专性吸附量也随pH值升高而减小.因此,改性秸秆生物质炭在酸性条件下对Cr（Ⅵ）有较高的吸附容量,可用于酸性废水中Cr（Ⅵ）的吸附和去除.
A batch experiment combined with the zeta potential,FTIR and XRD methods,was carried out to investigate adsorption of Cr （Ⅵ） by Fe （Ⅲ）-modified crop-straw biochar and its mechanism.Results show that in modification,Fe（Ⅲ） complexed with functional groups and formed a physical coverage layer of iron hydroxide precipitation on the surface of the biochar,thus lowering negative charge and increasing positive ones on the surface,and hence promoting Cr （Ⅵ） adsorption.The effect of Fe （Ⅲ） modification was more significant on peanut straw biochar than on rice straw biochar.At pH 5.0,the modification increased the maximum Cr（Ⅵ） adsorption of peanut straw-biochar and rice straw biochar by 79％ and 26％,respectively.When pH of the suspension varied in the range of 4.0-6.5,Cr（Ⅵ） adsorption of the original biochar and the Fe （Ⅲ）-modified biochars decreased with rising pH,and a similar trend was found with the effect of Fe（Ⅲ） modification on Cr（Ⅵ） adsorption of the biochars.The increase in negative charge on the surface of biochars was the main reason for the decrease in Cr（Ⅵ） adsorption with the rising pH.Electrostatic adsorption and specific adsorption of Cr（Ⅵ） occurred simultaneously on the surface of Fe（Ⅲ）-modified biochars.Meanwhile,specific adsorption of Cr（Ⅵ） also decreased with rising pH.Therefore,as Fe（Ⅲ）-modified crop straw biochars are quite high in Cr（Ⅵ） adsorption capacity under acidic conditions,they can be used as absorbents to remove Cr（Ⅵ） from acidic wastewater.
出处
《生态与农村环境学报》
CAS
CSCD
北大核心
2014年第4期500-504,共5页
Journal of Ecology and Rural Environment
基金
国家科技支撑计划(2012BAJ24B06)
