Preparation Of Different Molecular Weight Alginate Derivatives Delivery System And Its Release Pesticide Properties

With the development of agriculture science, pesticide was used in the field of agriculture more and more widely, as well as the environment impact of it is more seriously.That how to improve the utilization and persistence of pesticides has become the focus required for the research of new controlled release system of pesticide. The goal of this study is the preparing of controlled release pesticide carrier materials and improving the behavior of controlled release of pesticides, which regard polysaccharide polymers alginate emulsions and composite hydrogel as pesticide carrier materials.The effect of nano-TiO2 particles on the degradation of sodium alginate (NaAlg) by different photo-Fenton system was evaluated. And the degradation kinetics model of sodium alginate was investigated. The structure and performance of degraded NaAlg were characterized by Fourier transform infrared (FTIR), 1H NMR spectroscopy, X-ray diffraction analyses (XRD). Experimental results suggest that the reaction order of NaAlg degradation (n) is 0.51 and the extent of photocatalytic degradation can increase with the loading of TiO2 nanoparticles. Under the sono-photo-Fenton system of the degradation of NaAlg, the extent of degradation has been enhanced, which seems to be synergistic between ultrasound and ultraviolet irradiation with TiO2 nanoparticles. With the increase of the TiO2 concentration, the degradation rate constant decreases, and the synergy effect increases, and then it decreases with the concentration of TiO2 increases, at last, the synergy effect can strengthen with the increase of the catalyst concentration. The FT-IR and 1H NMR spectra results indicate that the C2-C3 bond in the structure of NaAlg is broken and intra-molecular esters are formed during the degradation process. In general,the sono-photo-Fenton process with TiO2 nanoparticles could provide an efficient way to degrade the NaAlg to low-molecular-weight.Poly-mannuronic acid was prepared by micro-wave assisted heating acid extraction from brown seaweeds. Using the response surface method to optimize the extraction of polymannuronic acid, and the interaction among the various factors was also analyzed. By the model analysis, the order of the factors influence effect was: Acid concentration >Temperature > Time. And the better conditions of the extraction of polymannuronic acid were temperature 80.5?, reaction time 4.06h and sulfuic acid concentration 17.65g/L.Under actual test conditions the yield of polymannuronic acid reached 18.2%, which was consistent with the predictive value of the model. Amphoteric polymannuronic acid(Ugi-PM) was prepared by Ugi reaction, which is the hydrophobic alkyl chain was grafted onto the polysaccharide carboxyl group. The stabilized emulsions of Ugi-PM were prepared by high speed shear emulsification method, and investigated the effect of the concentration of Ugi-PM on the stability of emulsion and the controlled release behavior of pesticide. The FT-IR, 1H NMR spectra and thermal gravimetric results indicate that Ugi-PM was synthesized successfully,and element analysis showed that the grafting ratio of Ugi-PM was 17.59%. By the stability test of emulsion, the results show that the concentration of Ugi-PM has a certain influence on the stability of emulsions. With the concentration of Ugi-PM in emulsions increase, the stability of emulsion increased, when the concentration of Ugi-PM was 0.5wt%, the stability of emulsion reached the best. While,at high concentration of Ugi-PM, the stability of emulsion was decreased, due to the polymer can cause the effect of bridging flocculation between emulsions droplets. And the controlled release of pesticide increase with the stability of emulsion increase.In this study, a novel series of composite hydrogels, which composed of sodium alginate (Alg), acrylamide and sodium montmorillonite (MMT), were synthesized by free-radical copolymerizations reaction and ionically crosslinked. The FT-IR and thermal gravimetric results indicate that the covalently crosslinked formed between polyacrylamide(PAA) and alginate, to forming ionically and covalently crosslinked networks hydrogel.Moreover, MMT was interspersed in the network of hydrogel, and forming the physical interlacing between the polymers chains and MMT clay lamellae. The results of XRD and TEM show that the chains of polymer have been successfully interspersed into the lamellae of MMT, leading to MMT lamellae separation and the interplanar distances increased. The microstructure analysis by SEM indicated that the internal pore structure of hydrogel matrix has been changed with the increase of MMT content, and the swelling degree decrease. Experimental results show that the process of swelling of composite hydrogel is belonging to Fickian diffusion. With the content of MMT increase, the swelling degree of hydrogel decrease. Due to MMT interspersed into the network of hydrogel which limits the swelling and extension of the molecular structure of polymer chains, leading to the swelling degree of composite hydrogel decrease significantly. Furthermore, with the increases of MMT contents, the diffusion resistance of drug from the hydrogel network increases, so that have the better effect on controlled release for pesticide.