| Graft copolymerization of acrylamide onto maize starch and activated starch using inverse emulsion polymerization were studied. The kinetics of graft copolymerization of acrylamide onto activated starch by dry ball milling in inverse emulsion was investigated with ammonium persulfate -sodium bisulfate as initiator, and the copolymerization was used to treat the Kaolin wastewater. The main experimental content and conclusions were as follow:1) The effects of emulsifier quantity, HLB value and volume ratio of oil to water on the stable of inverse emulsion system were investigated in this paper, the optimum conditions were obtained:Span80,Tween60 and Op-10 were used as the compound emulsifier, HLB values, emulsifier quantity, and volume ratio of oil to water were 4.3-6.2,4%-8% and 1～1.6,respectively.2) Graft copolymerization of acrylamide onto maize starch in inverse emulsion system were studied. The effects of reaction time, reaction temperature, initiator concentration, the mass ratio of acrylamide monomer to starch and volume ratio of oil to water on the conversion of monomer, grafting percentage and grafting efficiency have been investigated, The optimum conditions were determined using the Response Surface Analysis, and the properties of copolymer were analyzed by FTIR, SEM and XRD. When initiator concentration was 3.451 mmol/L, reaction temperature was 50℃, the mass ratio of acrylamide monomer to starch was 1.54:1, the conversion of monomer, grafting percentage were 93.06% and 54.42%,respectively. The results showed that molecular weight of St-g-PAM was 1.07 million, acrylamide monomer was successfully grafted on to the starch molecules, the crystalline regions of starch were decreased and the crystalline regions of the starch have been converted largely into the amorphous regions.3) The activated starch were prepared by dry ball milling, and the properties of activated starch were studied. The activated starch were used as the material to synthetize the Starch-Acrylamide Copolymer in inverse emulsion with ammonium persulfate -sodium bisulfate as initiator. The effects of balling time, initiator concentration, reaction temperature, reaction time, the mass ratio of acrylamide monomer to starch and volume ratio of oil to water on grafting efficiency have been discussed. The optimum conditions were determined using the Response Surface Analysis:balling time 1.57h, [(NH4)2S2O4]=2.39mmol.L"1, [NaHSO3]=1.695m mol.L-1,the mass ratio of acrylamide monomer to starch 2.14:1 and reaction temperature 51.20℃.Under these conditions, the conversion of monomer, grafting percentage and grafting efficiency were 97.01%±0.96%,65.92%±1.06% and 85.2%±0.22%,respectively. The results showed that molecular weight of St-g-PAM was 1.949 million, ball milling can promote the molecular disorder, destroy the hydrogen bones of starch and decrease the crystallinity of starch, making the crystalline regions of starch convert largely into amorphous regions. The chemical reactivity of activate starch had been improved, and the AM monomer and initiators were accessible to enter the interior of the starch granule and more starch macroradicals could be generated to graft with the AM molecules.4) The kinetics of graft copolymerization of acrylamide onto activated starch in inverse emulsion was investigated with ammonium persulfate -sodium bisulfate as initiator. The effects on the rate of grafting such as reaction temperature, initiator concentration, starch concentration, monomer concentration and the amount of emulsifier were studied, and the reaction mechanism of grafting copolymerization were discussed from the view points of kinetics and thermodynamics. The results showed that the equation of experimental rate of grating can be expressed as Rp∝[(NH4)2S2O4)]0.571 [NaHSO3] 0.571[St]0.592 [M]118[E]0.523. The polymerization rate equation were consistent with the theoretical polymerization rate equation.5) The programs of diffusion-limited aggregation (DLA) and diffusion-limited cluster-cluster aggregation (DLCA) model were written based on MATLAB platform to used to simulate the aggregation process of flocs. The simulate results of DLA model showed that the fractal dimensions of flocs decreased from 1.77 to 1.30 using radius of gyration method, the fractal dimensions decreased with the increasing of particle number. The simulate results of DLCA model showed that fractal dimensions of flocs decreased from 1.551 to 1.341 using box-counting method. With the increasing of particle number, the number of individual particle decreased while the number of clusters increased at first and then decreased. Due to the shielding effect of the particles, simulation flocs showed inner-tenuous, external-loose and high porous structure.6) Starch-Acrylamide Copolymer (St-g-PAM) and Polyaluminum chloride (PAC) were used as the flocculants to treat the Kaolin wastewater. The effects of the amount of PAC and St-g-PAM, coagulation temperature and pH on the removal rate of turbidity, the fractal dimensions of flocs and average particles sizes of flocs were discussed. The microphotography and Image processing technology were used to analyze the results. The optimum conditions were deterimend using RSM mothed. The results showed that The structure of flocs expresses the self-similarity and randomness, which were the basic characteristic of fractal. The fractal dimension of flocs has not positive corelationship with the average size of flocs, the optimum conditions of flocculate were obtained as follow: coagulation temperature was 25℃, pH was 6.5, the dosage of PAC was 21.5mg/L and the dosage of St-g-PAM was 5mg/L, the measure values of removal rate of turbidity, average size of flocs and fractal dimension were 98.02%,0.109mm and 1.624. |
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