| Cationic polyacrylamide(CPAM) is a widely used organic polymer flocculant, and the modification of the CPAMs can produce hydrophobically associating cationic polyacrylamide(HACPAM). HACPAM, based on the hydrophobic association action, could strengthen the interaction between polymer and the colloidal particles in sewage, which promotes the phase transformation of the flocs. So HACPAM has better flocculation performance than traditional CPAM. Besides, among various initiation methods for polymer synthesis, UV-initiated polymerization has many advantages such as low energy, short time, simple operation, etc. However, there are rare researches on the synthesis of HACPAM initiated by UV light.This paper aims to prepare a new efficient HACPAM flocculant with short polymerization time and good solubility based on the novel UV-initiated polymerization system. Besides, this paper tries to reveal the relationship between the structure of the polymer and its properties, which could provide theoretical guidance for its preparation and engineering application. Therefore, a surface-active monomer(surfmer), acryloxyethyl dimethyl benzyl ammonium chloride(AODBAC), was adopted to be copolymerized with AM to prepare HACPAM. The product was named P(AM-AODBAC)(PAA).To better understand the relationship between the polymer structure and its solution properties, a common cationic monomer, acryloyloxyethyltrimethylammonium chloride(DAC), was used to prepare another copolymer P(AM-DAC)(PAD), which was used to compare with PAA. DAC was employed in this paper because it is similar to AODBAC in structure but has less phenyl groups. According to the molecular structures of monomer AODBAC and DAC, this paper firstly compare the differences of polymer microstructure, intrinsic viscosity, dissolution time, surface morphology, thermal stability and hydrophobic association between the two copolymers, and further more compare the differences of the flocculation performance in sludge dewatering and oily wastewater treatment between the two copolymers. Besides, a comparison of flocculation performance was made between PAA and commercial flocculants to explore the market prospects of PAA. Currently, there were no report about the preparation of PAA initiated by UV light and the comparison of PAA and PAD from above mentioned aspects.The main contents and conclusions are as follows:① The monomer reactivity ratios of copolymerization systems initiated by UV-light including AM/AODBAC system and AM/DAC system were measured, and the composition curve and sequence length distribution of the two copolymers was calculated. Results showed that DAC in copolymer PAD tend to form disorder character, while AODBAC in copolymer PAA tend to form a micro-block structure. Besides, PAA has higher cationic degree and more long chain segments of cationic monomer than PAD at the same cationic monomer molar ratio, and the difference of long chain segments of cationic monomer between the two copolymers increased as the cationic monomer molar ratio increased.②In order to optimize the properties of bridging adsorption and solubility of PAA, the effect of initiator concentration, total monomer concentration, urea concentration, EDTA concentration, p H value, irradiation time,molar ratio of AODBAC and AM on intrinsic viscosity and dissolution time of PAA were investigated through single-factor experiments,and the optimized synthetic conditions were obtained. In addition,the significance of factors including molar ratio of AODBAC and AM, total monomer concentration, urea concentration and initiator concentration was analyzed through orthogonal experiment. Moreover, a series of copolymer PAD and PAA were prepared under the same synthetic condition, and the intrinsic viscosity and dissolution time of the two copolymers were compared and analyzed.③ Fourier transforms infrared spectroscopy(FTIR), magnetic resonance spectrometer(1H-NMR), scanning electron microscope(SEM) and thermal gravimetric analysis(TGA) were employed to compare the functional group structure, surface morphology, thermal stability of copolymer PAA and PAD. Results showed that the chemical structure of PAD was similar to PAA but has less a benzyl, and the microstructures of their polymer chain were different. PAA had more micropores and greater fractal dimension than PAD, which facilitated its flocculation performance. And both of the two copolymers have good thermal stability. Besides, on the basis of radical polymerization theory, the reaction mechanisms of PAA and PAD were formulated through the aggregation behavior of cationic monomers in solution before reaction, and initiation, growth, termination and transfer of the molecular chain.④The solution behavior of copolymer PAA and PAD was investigated and compared, and the results showed that PAA had strong thickening properties in aqueous solution. As the increase of AODBAC content and intrinsic viscosity of polymer, the apparent viscosity of PAA increased while the critical association concentration C* of PAA reduced. Besides, copolymer PAA showed higher hydrophobic association and salt tolerance than PAD under identical experimental conditions.⑤The copolymer PAA was used for sludge dewatering experiment, and the effect of cationic monomer molar ratio, dosage, intrinsic viscosity, p H value on the sludge dewatering performance was investigated. Meanwhile, the sludge dewatering performance of copolymer PAA and PAD at the same dosage and p H was compared. The results of sludge dewatering performance and Zeta potential showed that charge neutralization, adsorption bridging and hydrophobic association worked together to improve the sludge dewatering performance of PAA. Finally, the sludge dewatering performance of copolymer PAA was compared with those of three commercially available CPAMs, it was found that PAA was superior to commercial flocculants in both aspects of sludge dewatering performance and cost, indicating that PAA flocculant has broad application prospects for sludge dewatering.⑥The copolymer PAA was used for simulated oily wastewater treatment. The effect of coagulant dosage, intrinsic viscosity, AODBAC feed molar ratio on the oil removal efficiency was investigated. And on this basis, the oil removal efficiency combined by organic flocculant of PAA and inorganic flocculant of PAC was studied. In this process, the effect of dosage of PAA and PAC, and the order of the two regent added on the oil removal efficiency were studied. In addition, the oil removal performance of self-made PAA was compared with those of several organic flocculants in oily wastewater treatment considering two cases of with and without PAC. Results showed that the unique molecular structure of PAA made it play a great role in charge neutralization, adsorption bridging and hydrophobic association in oily wastewater process, which was conducive to strengthening its oil removal efficiency. So PAA had higher oil removal efficiency than other organic polymer flocculants in this study considering two cased of with and without PAC. Compared with PAA used alone, combination of PAA and PAC could ensure the oil removal performance, reduce the cost, increase the size and compactness of flocs, accelerate settling velocity and decrease the amount of sludge. All this indicated that self-made PAA is an efficient organic polymer flocculant, and it has good application prospects in oily wastewater treatment. |
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