| Superabsorbent is a new type of multifunctional polymer materials with super-absorbent capacities and adsorption abilities of heavy metal ions. It has been generally applied into many fields including agriculture and soil improvement. In recent years, numerous superabsorbent literatures have been reported, however, literatures for semi-IPN(interpenetrating network structure) superabsorbent resins were less reported.The semi-IPN superabsorbent resin bear not only good biocompatibility and water retention capacity, but also prominent adsorption ability for heavy metal ions. Therefore,researches involving with semi-IPN polymers have important theoretic and practical significances.In this thesis, a new semi-IPN polymer was synthesized by a free-radical solution polymerization method using starch, polyvinylpyrrolidone(PVP) and sodium acrylate(AA) as raw materials. In this synthesis system, ammonium persulfate(APS) and N,N’-methylene-bis-acrylamide(MBA) acted as initiator and chemical cross-linking agent,respectively. The synthesis route was optimized through investigating synthesis conditions.The results presented the optimal conditions that the reaction temperature of the system was 60 oC, the added amount of PVP, starch, APS and MBA was 20%, 30%, 1.25% and0.15%, respectively, a neutralization degree was 80%. The water and salt absorption capacities of the optimized material can be improved to 2017.8 g/g distilled water and 79.0g/g NaCl aqueous solution(0.9 wt%), respectively. In addition, the material was characterized by some technologies including FTIR, SEM and DSC. FTIR spectrum showed PNaA chain had been grafted onto the starch framework. DSC agreed that the resin was provided with good thermal stability under the temperature of 221 oC. SEM showed that the resin had a large number of wrinkles contributed to improve the surface area. CT showed the resin was three-dimensional network structure. The absorption capacity of semi-IPN starch/PVP/AA superabsorbent is measured by a screen method.Absorption rate results measured with different hydrogel particle sizes exhibited that the resin with a smaller particle size possessed a faster water absorption rate. According todiffusion kinetics, the semi-IPN superabsorbent strach/PVP/AA conformed to apseudo-second order kinetic model. The resin bearing smaller particle sizes may attain an improvement in water absorption capacity. This phenomenon can be ascribed to the flexible spreading of the polymer chains in the resins with small particle sizes.Furthermore, the thermodynamic result of strach/PVP/AA adsorption to pb2+ ions complied with a Freundlich isotherm model and it was attributed to spontaneous multilayer adsorption.Some application conditions of the semi-IPN superabsorbent strach/PVP/AA,including pH range, reusability, optimum usage in soil and the anti-caking properties of water-soluble fertilizer or compound fertilize were investigated. The results illustrated that optimal pH range was 5 to 9, the resin still held good capability after repeatedly absorbing water for six times and its usage was 0.15 g/50 g. Also, the resin made a significant improvement in water retention and saturated aqueous rates compared to those of the blank sample in physiological saline and tap water. The two values ran up to 1.58 times and 3.31 times, respectively. Moreover, the semi-IPN superabsorbent strach/PVP/AA has good anti-caking properties of 60% and 84% for fertilizer and water-soluble fertilizer,respectively. |
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