研究报告

  • 刘畅,马杰,王龙,陈雅丽,翁莉萍,李永涛.孔隙堵塞效应降低生物质炭-磁铁矿混合物对镉的吸附能力[J].环境科学学报,2021,41(10):4140-4149

  • 孔隙堵塞效应降低生物质炭-磁铁矿混合物对镉的吸附能力
  • The pore blocking effect decreases the cadmium adsorption onto biochar-magnetite complex
  • 基金项目:国家自然科学基金(No.41701262);国家重点研发计划(No.2017YFD0801003);河南农业大学科技创新基金项目(No.KJCX2020A18)
  • 作者
  • 单位
  • 刘畅
  • 农业农村部环境保护科研监测所, 农产品质量安全环境因子控制重点实验室, 天津 300191
  • 马杰
  • 农业农村部环境保护科研监测所, 农产品质量安全环境因子控制重点实验室, 天津 300191
  • 王龙
  • 河南农业大学资源与环境学院, 郑州 450002
  • 陈雅丽
  • 农业农村部环境保护科研监测所, 农产品质量安全环境因子控制重点实验室, 天津 300191
  • 翁莉萍
  • 农业农村部环境保护科研监测所, 农产品质量安全环境因子控制重点实验室, 天津 300191
  • 李永涛
  • 1. 农业农村部环境保护科研监测所, 农产品质量安全环境因子控制重点实验室, 天津 300191;2. 华南农业大学资源环境学院, 广州 510642
  • 摘要:利用吸附实验,通过吸附等温模型,研究了磁铁矿、生物质炭和生物质炭-磁铁矿混合物对Cd的吸附能力;在此基础上,使用X射线光电子能谱(XPS)和BCR连续提取法对吸附介质上Cd的结合形态进行分析.Langmuir和Freundlich两种吸附等温模型拟合结果表明,无论单一的磁铁矿和生物质炭或是二者的混合物对Cd的吸附均为单层吸附.磁铁矿和生物质炭对Cd单独吸附的吸附量分别为18.9、14.0 mg·kg-1,而生物质炭-磁铁矿混合物对Cd的吸附量为12.0 mg·kg-1,低于其单独吸附Cd的吸附能力.当加入胡敏酸(HA)时,磁铁矿和生物质炭对Cd的吸附量分别为23.0、14.7 mg·kg-1,混合物对Cd的吸附量为13.3 mg·kg-1,混合后材料对Cd的吸附能力均降低.粒径、孔隙度和形貌表征结果显示,生物质炭粒径(10~100 μm)远大于磁铁矿粒径(1~10 μm),混合后部分磁铁矿纳米颗粒堵塞生物质炭的微孔,使混合后材料孔隙度明显降低(88.5%~74.5%),从而导致混合材料吸附能力下降.XPS分析中,与磁铁矿混合或加入HA都对生物质炭表面C—O官能团含量有影响,从而影响吸附效果.从XPS结果还可以看出,吸附后的Cd全部以Cd2+形式存在,BCR连续提取也证明吸附剂上的Cd主要以可交换态存在.磁铁矿和生物质炭除去Cd主要依赖表面吸附、络合及共沉淀.吸附的Cd较不稳定,随着环境变化容易发生解吸作用,重新释放到环境中.
  • Abstract:The cadmium (Cd) adsorption onto magnetite, biochar, and biochar-magnetite mixtures were studied using adsorption isothermal models by adsorption experiments. Moreover, the fractions of adsorbed Cd on the adsorbing material were analyzed using the X ray photoelectron spectrum (XPS) and extracted by BCR sequential extraction. Langmuir and Freundlich adsorption isothermal model fitting results showed that the Cd adsorption onto magnetite, biochar, and their mixture were monolayer adsorption. The adsorption amount of Cd onto magnetite and biochar were 18.9 mg·kg-1 and 14.0 mg·kg-1, respectively, higher than that of biochar-magnetite (12.0 mg·kg-1). In the presence of humic acid (HA), the adsorption amount of Cd onto magnetite, biochar, and biochar-magnetite were 23.0 mg·kg-1, 14.7 mg·kg-1, and 13.3 mg·kg-1, respectively, showing that HA enhanced Cd adsorption. The particle size of biochar (10~100 μm) is much larger than that of magnetite (1~10 μm), thus, some magnetite nanoparticles blocked the micropores of biochar after mixing, which obviously reduced the porosity of the mixed material (88.5% to 74.5%), causing a decrease in the adsorption capacity of the mixture. The results of the XPS showed that mixing with magnetite or adding HA changed the content of C-O functional groups on biochar surface. After adsorption, the Cd was in the form of Cd2+, and the BCR results further indicated that the Cd was mainly existed as exchangeable fraction. Removal of Cd by magnetite and biochar mainly depended on surface adsorption, complexation, and co-precipitation, however, the adsorbed Cd was unstable and easy to be released back to the environment.

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