| The waste H2SO4 from alkylation is generated during production of high-octane alkylation gasoline by a sulfuric acid process.Our research group has used this waste H2SO4 to prepare industrial grade magnesium sulfate heptahydrate with magnesium oxide ore as raw material,hydrogen peroxide as oxidant,and mechanical activation-assisted solid phase synthesis prepared bagasse ester as oxidation catalyst.The organic impurities in magnesium sulfate solution were oxidatively degraded and decolorized by the simulated Fenton-like reagent.Magnesium hydroxide sulfate hydrate whisker(MHSHw)is a kind of magnesium salt whisker which is relatively easy to prepare and has excellent performance.It has the function of enhancing reinforcement,fire prevention and smoke suppression.It can be used as a filling material widely used in chemical industry,mechanical electronics,etc.Based on previous studies,MHSHw were prepared by using the magnesium sulfate solution prepared with waste H2SO4 as raw material.The main research contents and results are as follows:(1)MHSHw was prepared by hydrothermal method with the magnesium sulfate solution prepared by waste H2SO4 and magnesium oxide ore as rew material.The morphology,crystal structure,and surface functional groups of the obtained products were analyzed by SEM,XRD,TG-DSC,FT-IR,and EDS,and were used as evaluation indexes.The effects of decolorization degree of magnesium sulfate solution,magnesium ion concentration in solution,hydrothermal temperature,hydrothermal time and other conditions on the preparation of MHSHw.When the process parameters are:No.2 magnesium sulfate heptahydrate(general decolorization degree),magnesium ion concentration of 1.0 mol/L,hydrothermal temperature of 180 ?,hydrothermal time of 5 h,stirring speed of 500 r/min,the 153 type MHSHw with uniform and dispersed whisker morphology and 80?120 aspect ratio was prepared.(2)Preparation of hydrophobic MHSHw by in-situ hydrophobic modification.The effects of in-situ modifier,hydrothermal temperature,and hydrothermal time on the modification were studied with liquid fatty acid(oleic acid)and solid fatty acid(palmitic acid,palmitic acid)as in-situ modifiers,and water contact angle and lipophilicity value as evaluation indicators,respectively.The mechanism of in-situ modification was preliminarily analyzed.The results showed that the MHSHw prepared by this method exhibited uniform morphology and good crystal form.The contact angle of hydrophobic modified products obviously increased,indicating that effect of in-situ hydrophobic modification was remarkable.The fatty acids did not simply attach to the whisker surface,but chemically reacted with the hydroxyl groups on the surface of the whisker to form the Mg-O-C structure.(3)Application properties of MHSHw.The composite materials were prepared with polyvinyl chloride(PVC)and the MHSHw before and after in-situ modification.The effects of the dosages of the MHSHw without and with in-situ modification on the mechanical properties,thermal properties,and flame retardancy of the composites were investigated.The results showed that the tensile strength of the composites increaseed first and then decreased with the increase of MHSHw dosage,and the bending strength increased with the increase of MHSHw dosage.When the MHSHw dosage was 15 wt%,the tensile strength and bending strength of the composite wre 40.1 MPa and 60.1 MPa,respectively,which were 52.3%and 67.7%higher than those of pure PVC.MHSHw improved the thermal properties of PVC.When the dosage of in-situ modified MHSHw as 15 wt%,the temperature of maximum weight loss rate of composites increased from 289.6 to 311.1 ?,and the residual amount of PVC increased from 10.43%to 21.81%.MHSHw effectively improved the flame retardant properties of PVC.The PVC had an oxygen index of 30.0 when no MHSHw was added,and the combustion was very fast accompanied by irritating odor smoke.After filling 20 wt%of MHSHw,the oxygen index reached 39.2,and the smoke suppression effect was remarkable. |
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