The Preparation Of Cassava Starch Microspheres And Reasearch Its Structure And Performance

Starch microspheres is a new kind of functional polymer materials which are widely application in biomaterials. However, magnetic starch microspheres which has magnetic responsivability, biocompatibility and non-toixc belongs to starch microspheres.In this work, cassava starch microspheres (CSMs) and magnetic cassava starch microspheres (MCSMs) were prepared by inverse emulsion method with cassava starch (CS) and made by ourselves of nano-particles of surface-modification iron oxide (MIO) as raw materials, using Span-80and Tween-80as emulsifier, N,N’-methylenebisacrylamide (MBAA) as cross-linker, ammonium persulfate as initiator. The main researchful contents are as follows:(1) The effects of mass fraction of starch solution, volume ratio of oil to water, concentration of cross-linker, concentration of emulsifier and initiator on average diameter (I) of CSMs were investigated respectively. The effects of mass fraction of starch solution, mass ratio of CS to MIO, volume ratio of oil to water, reaction time and temperature on I and iron oxide content(W) of MCSMs were investigated. The structures of CSMs and MCSMs were characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Biological microscope (BM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravimetric (TG), Simultaneous thermal analysis (STA) and Vibrating sample magnetometer (VSM). The reaction mechanism of the preparation of MCSMs was discussed.(3) The isotherm adsorption and its model of CSMs and MCSMs in585mg·L-1NaCl water solution of carmine were studied respectively. The experiment results were as follows:(1) The optimization combination of the preparation of CSMs are as follows:mass fraction of starch solution,8.0wt.%; volume ratio of oil to water,10.0:1.0; concentration of cross-linker,1.0wt.%; concentration of emulsifier,12.0wt.%and concentration of initiator,0.8wt.%. The I values of CSMs is16.3μm at above conditions. Based on the I as target, the optimization combination of the preparation of CSMs are as follows:mass fraction of starch solution,8.0wt.%; mass ratio of CS to MIO,13.33:1; volume ratio of oil to water,8.0:1.0; reaction time,2h; reaction temperature,60℃. The I and W of MCSMs at above conditions are13.6μm and7.1%, respectively. However, based on the W as target, the optimization combination of the preparation of MCSMs are as follows:mass fraction of starch solution,10.0wt.%; mass ratio of CS to MIO,6.67:1; volume ratio of oil to water,10.0:1.0; reaction time,3h; reaction temperature,60℃. The I and W of MCSMs at above conditions are20.9μm and10.76%, respectively.(2) The results show that CSMs are found to have a porous and like honeycomb of its contour, and the adsorption peak at1553cm-1in FTIR ascribed to the crosslinked reaction between CS and MBAA. In addition, the cystallinity of CSMs is lower than that of CS. Furthermore, thermal stability of CSMs is lower than those of CS. However, the surface of MCSMs have uneven and roughness, possessed core-shell structure because iron oxide is successfully embedded into starch shell; the crystalline of MCSMs decreased with the crosslinked-embedded reaction occurring at not only loose amorphous of CS but crystalline regions; the thermal stability of MCSMs is a little lower than that of CS. Meanwhile, MCSMs have better magnetic response, which its saturation magnetization strength and magnetic susceptibility are7.07emu/g and3.005×10-6emu/Oe, respectively. However, based on the research of precedessor, the reaction mechanism of the preparation of MCSMs fits radical polymerization.(3) The adsorption carmine process of CSMs and MCSMs fits Langmuir isotherm adsorption. The adsorption enthalpy change, free energy change, and entropy of CSMs and MCSMs are31.58KJ·mol-1,-3.72KJ·mol-1,118.47J·mol-1·K-1and30.24KJ·mol-1,-2.3KJ·mol-1,109.21J·mol-1·K-1, respectively. The findings indicated that the adsorption process of CSMs and MCSMs is an endothermal, disorder, and spontaneous physical adsorption.