| In this thesis, the physicochemical characteristics of PFC-HA flocs (polyferric chloride-humic acid) formed under different flocculation conditions such as coagulation-flocculation pH, the dosage of PFC, agitation conditons etc, were studied. And the different fractal dimensions were emplyed to reveal the changes of morphology and structure of these flocs during different coagulation-flocculation conditions. The corresponding fractal dimensions were estimated by different ways, such as: one-dimensional fractal dimension D1, two-dimensional fractal dimension D2, three-dimensional fractal dimension D3, surface fractal dimensions DS and mass fractal dimensions Df. Moreover, the surface anisotropy of PFC-HA flocs was also analyzed.The flocs images with magnification of 26 to 31times were taken with a charged coupled device (CCD) sensor Their fractal dimensions based on image methods were, 0.93-1.17 for D1(lgP-lgdL), 1.42-1.72 for D2(lgA-lgdL), 1.15-1.59 for D2(lgA-lgP) 1.27-1.75 for D2'(lgA-lgP) ,2.14-2.59 for D3(lgV1-lgdL) and 2.03-2.61 for D3(lgV2-lgdL). Then D2(lgA-lgdL) of the flocs shows more remarkable response to the removal of HA, for example, at pH5.00, with the increase of PFC dosage, the particles size of flocs became smaller, but D2(lgA-lgdL) decreased at first, and then increased, fianally tended to be stable, which demonstrated the compact flocs were formed gradually, meanwhile, the better HA removal effect were found.During the coagulation-flocculation dynamic process, the fractal dimesion D2(lgA-lgdL) decreased in the high-speed mixing stage, and increased at the beginning of low-speed agitation process, then decresed for a while, these fluctuation apprears for several times. The particles size of PFC-HA flocs also fluctuated with reverse tendency to D2(lgA-lgdL). Combing the fractal dimensions with particle size at different flocculation stages could give a reseasonable explaination of coagulation-flocculation dynamic process.In addition, under the optimum agitation conditions, the smaller PFC-HA flocs were formed with average diameter of hundreds of microns and higher fractal dimensions, which indicates more compact structure for these flocs. When increasing the pH value for coaguation, the effective density of the flocs decreased all the time, while their size and the sedimentation rate increased firstly, after that, their particles size had little chang, and their sedimentation rate decreased. Especially at pH=7.00, both the sedimentation rate and mass fractal dimension Df (caculated by Lagan-Allen equation) of the formed flocs reached the maximum values, repectivley. The pore surface fractal dimension DS determined from Nitrogen adsorption isotherms and desorption ones were different, the former were 2.48-2.69, and the latter were 2.19-2.60, while the pore surface DS values based on thermodynamic model exceeded the limitation value of fractal dimension. Calculating from Nitrogen adsorption isotherms, the Ds values of these flocs powder decreased when the PFC dosages was less than 4.04×10-4mol·L-1(as Fe3+) at coagulation pH values of 5.00-7.00, and then increased with addition of PFC dosage. However, the Ds increased all the time when pH value was 8.00 or 9.00. Furthermore, the The anisotropy analysis results showed that the surface of flocs had anisotropic characteristic.The microstructure and other physicochemical characteristics of PFC-HA flocs powder prepared by cryo–freezing-vacuum-drying method were also analyzed. The results showed that PFC-HA flocs were amorphous structure, were mainly composed of C,O,Fe elements, and the specific functions of the PFC-HA flocs reserved some ones of PFC and HA. The N2 adsorption-desorption method demonstrated that specific surface areas of the vacuum-freeze-dried PFC-HA flocs, formed under different coagultion conditions, were 38.04-184.59m2·g-1, and pore volumes of them were 0.04-0.57cm3·g-1, and pore diameters for flocs were 3.72-14.67nm.
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