| Until the end of 2013, processing rate of municipal sewage had reached 75.21 % in our country. The government put forward the requirement that the average processing rate of municipal sewage should reach 80% up to the year of 2015, of which 85% should be reached in big cites and 70% should be reached in small and mid-sized cities. The processing rate of municipal sewage increases, which results in the increasing amount of sludge. Therefore, sludge treatment and disposal will become an important and serious problem recently.As we know, floccuant conditioning is the key process during sludge dewatering. However, conventional flocculants for sludge treatment are no longer sufficient because of the increases in the volume of generated sludge and the deterioration of characteristics of the sludge. Therefore, the development of a sludge flocculant with high flocculation efficiency and the ability to be widely applied has become an urgent task. Amphoteric sludge flocculant, has both the characteristics of anionic polymer and cationic polymer flocculants, so it has some merits:improving the size of sludge floc, decreasing the percentage of moisture of sludge and the wide p H effective range in sludge dewatering, especially applying to the sludge with deterioration of characteristics that is not satisfactorily treated by conventional cationic polymer flocculants. Since the 1990 s, the research and development of amphoteric polymer flocculants has been more and more active and commercial value has been taken advatange of in foreign countries. While in our country, development of related fields has been still in experimental stage. The industrial product we made still had some technical problems, such as low molecular weight, uncontrolled molecular structure, weak in stability and solubility etc.In this study, a novel amphoteric terpolymer PADA was synthesized by acrylamide(AM), acryloyloxyethyl trimethyl ammonium chloride(DAC) and 2-acrylamido-2-methyl-propane sulfonate(AMPS) in aqueous solution, using a complex initiators composed of redox initiator and azo initiator. The influences of monomer molar ratio, reaction temperature, concentration of initiator and reaction p H on the intrisnsic viscosity, water content(WC) and specific resistance to filtration(SRF) were investigated using single factor experiments associated with RSM, so that the optimal conditions were found.The ingredient of product was characterized by FT-IR and 1H NMR, which confirmed that PADA was composed of quaternary ammonium group, sulfonate group, and amide group. TGA indicated that it has thermodynamic stability. TEM pictucre showed the high resolution of it.The reaction dynamic equation was calculated using Capillary expansion method: pR =kIc0.58Mc1.46, the apparent activation energy was 57.69 k J/mol.The application to sludge dewatering of municipal sewage treatment by PADA has been carried out compared with cationic polymer PAD. The result showed that the PADA was a ideal flocculant with better hydrolysis stability, wider p H effective range, faster filtrating speed, lower optimal dosages and moisture percentage of sludge.Subsequently, to analyze the effects of characteristics of PADA on sludge flocs, the morphology, fractal dimension and physicochemical properties of sludge flocs flocculated by PADA with different ionic degree and molecular weight were investigated.Meawhile, the correlation of flocs properties and dewatering efficience was statistically analyzed trough Pearson equation. Finally, mechanism and model of sludge dewatering with PADA has been put up based on the said research. |
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