• 关键词：聚合氯化铁-腐殖酸(PACl-HA)絮体  元素组成  特征官能团  晶体结构  絮体干燥样品表面与孔表面  分形  尺度范围

• 基金项目：国家自然科学基金资助项目(No.20407004,No.50578012,No50178009);霍英东青年教师基金资助项目(No.91078);北京林业大学研究生基金资助项目(No.05jj006)

• 王毅力
• 北京林业大学资源与环境学院环境科学学科, 省部共建森林培育与保护教育部重点实验室, 北京 100083

• 石宝友
• 中国科学院生态环境研究中心环境水质学国家重点实验室, 北京 100085

• 杜白雨
• 北京林业大学资源与环境学院环境科学学科, 省部共建森林培育与保护教育部重点实验室, 北京 100083

• 刘杰
• 北京林业大学资源与环境学院环境科学学科, 省部共建森林培育与保护教育部重点实验室, 北京 100083

• 摘要：采用低温急速冷冻-真空干燥技术制备了PFC-HA絮体的粉末样品,研究了这些样品的物理与分形特征.结果表明,PFC-HA絮体具有晶体结构,SEM图象中有方块状形体;絮体主要组成元素为C、O、Fe,所含的特征官能团保留了絮体组成原料的一些特征;絮体的干燥样品的BET比表面积为51～92m²·g^-1,BJH累积吸附孔体积为0.0638～0.108cm³·g^-1,BJH脱附平均孔径为3.53～4.60nm,PSD峰值对应孔径3.9nm(4^#样品还有另外一个PSD峰值53.2nm).PFC-HA絮体的干燥样品具有自相似性的粗糙表面,呈现多尺度分形特征;图象法确定的表面分形维数D_s值远低于N₂吸附/脱附等温线法确定的结果,分别为2.14～2.22、2.90～2.96;前者的分形尺度大约处于23～390nm之间,主要属于絮体干燥样品的外表面尺度,后者的分形特征尺度区间的下限大约为0.2nm,属于孔表面尺度,因此,PFC-HA絮体干燥样品的表面粗糙度主要集中于孔表面.另外,对同一絮体,N2吸附法和脱附法确定的孔表面分形维数基本相同.通过热力学模型计算出的4^#样品的D_s值接近于FHH理论计算出的结果,但分形尺度的区间变小了.

• Abstract：The primary objective of this paper was to investigate the fractal characteristics of polyferric chloride-humic acid (PFC-HA) flocs. The powder of PFC-HA flocs was prepared by cryo-freeze-vacuum-dried method, which was characterized by SEM, XRD, FTIR, elemental analysis and surface area measurement. The results showed that the flocs were mainly constituted by elements of C, O, Fe, and some characteristic functional groups from PFC, HA or Kaolin were reserved. XRD patterns proved that PFC-HA flocs contained crystalline matters, which exhibited block structures in SEM images. The microstructure of cryofixation-vacuum-freeze-dried PFC-HA flocs was investigated by N₂ absorption-desorption method: 51～92 m²·g^-1 of BET specific surface area, 0.0638～0.108 cm³·g^-1 of BJH cumulative absorbed volume and 3.53～4.60nm of BJH desorption average pore diameter. The peak values of pore size distribution (PSD) curves were found at 3.9nm (pore diameter), but an extra peak value was found for sample 4^# at 53.2nm. The self-similar and rough surface was observed in SEM images of freeze-dried PFC-HA flocs. The surface fractal dimensions D_s of the flocs determined from SEM images and N₂ absorption-desorption method were 2.14～2.22 and 2.90～2.96, respectively. The corresponding fractal scale for the former method was 23～390nm, which was mainly attributed to the exterior surface scales, and the lowest limit of the fractal scale for the latter method was 0.2nm, which fell in the pore surface scales. It demonstrated that the surface of cryofixation-vacuum-freeze-dried flocs had multi-scale fractal properties; the wall of pores was very rough and possessed big space-filling capability, which contributed to the main roughness of the surface of freeze-dried PFC-HA flocs. Furthermore, the pore surface fractal dimensions D_s calculated from N₂ absorption and desorption data had little difference. For samples 1, 2 and 3^#, the much higher pore surface D_s values calculated through thermodynamic model had discrepancy from Sahouli et al's results. However, for sample 4^#, the pore surface D_s value calculated by thermodynamic model was very close to that by FHH theory, only with smaller fractal scale range.

• Key words：polyferric chloride-humic acid(PFC-HA) flocs  composition  characteristic functional groups  crystal structure  cryofixation-vacuum-freeze-dried floc surface and pore surface  fractal  range scale

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