| The powder of polyaluminum chloride-humic acid(PACl-HA) flocs was prepared by cryo-freezing-vacuum-drying method. Then these flocs were characterized by X-ray diffractometry, FTIR spectroscopy, elementary analysis and surface area determination. The results show that these flocs are amorphous, mainly composed by elements of C, O, Al, and reserve some characteristic functional groups from PACl, HA or Kaolin. The N2 absorption-desorption data determined the microstructure of PACl-HA flocs: 130～161 m2/g of BET specific surface area, 0.38～0.52 cm3/g of BJH cumulative absorbed volume and 7.7～9.6nm of BJH desorption average pore diameter. The peak values of pore size distribution(PSD) curves were found at 8.4～11.2nm of pore diameter. The self-similar and rough surface was observed in SEM images of PACl-HA flocs. The surface fractal dimensions Ds of the flocs determined from both SEM images method and N2 absorption-desorption one were 2.03～2.26 and 2.24～2.37, respectively. The correspondent fractal scale for the former method was 23～390nm, mainly belonging to exterior surface scales, and the lowest limit of the fractal scale for the latter method was 0.2nm and fell in pore surface scales. This demonstrated that the flocs surface had multi-scale fractal properties. Furthermore, some difference was given between the pore surface fractal dimensions Ds calculated from N2 absorption data and desorption data. The calculated pore surface Ds values of much more than three through thermodynamic model had discrepancy from Sahouli et al ‘s results. |
