Study On The Physicochemical And Fractal Properties Flocs Formed By The Coagulation Of Poly-ferric Chloride(PFC) And Humic Acid(HA)

In this thesis,the morphology of flocs,being formed by reaction between poly-ferric chloride(PFC) and humic acid(HA) during the coagulation process, were observed with scanning microscope(SEM) and CCD photo, and their physicochemical properties were also analyzed with FTIR. Furthermore, the fractal characteristics of these flocs formed under different conditions were studied.The optimum dosages determined by coagulation beaker test of HA water with TOC of 4.79 mg.L^-1 as follows: 0.4095 mmol.L^-1 (as Fe³⁺) is for HA water with pH=9.0, 0.2535 mmol.L^-1 for HA water with pH=7.0 and pH=5.0.The FTIR spectrum showed that the specific functions in the PFC-HA flocs, being prepared by cryofixation-vaccum-freeze-drying technique, reserved some ones of PFC and HA. The microstructure of these powders was investigated by N₂ adsorption-desorption method. The order of BETspecific surface areas is following pH 7.0flocs>pH5.0flocs>pH 9.0flocs. Both the accumulation pore volume and average pore diameter decrease with pH increase of of HA water. The pore surface fractal dimensions calculated by FHH fractal model with adsorption data and desorption data had some differences, which maybe result from different process used in D_s calculation. Moreover, there are great differences between the values of D_s calculated through FHH fractal model and thermodynamic model, and the latter D_s values were greater than three and could not give meaning for fractal.The PFC-HA flocs images were taken by in-situ CCD system. The largest flocs were found at flocculated HA water with original pH 9.0, and the least ones with original pH 5.0. The mass fractal dimension values of PFC-HA flocs calculated with sedimentation rates method is 1.3-2.0. The calculated D_f values using Logan equation were greater than the ones using Allen equation, and the values based on the relation between effective density and maximum diameter were also greater than the ones between effective density and equivalent circle diameter. The highest values of D_f were found on flocs formed in HA water with original pH 7.0,the second highest values in HA water with original pH 5.0, and the minimum D_f were in HA water with original pH9.0.The fractal dimensions calculated by image methods for flocs formed under different conditions showed that there was less remarkable response to the change of dosage and flocculation time between values of the one-dimension (D₁) fractal dimensions and two-dimension (D₂) fractal dimensions of same flocs.