Synthesis And Application Of Schiff Base Derivatives Of Dialdehyde Starch

Dialdehyde starch is a kind of great potential and broad promising bio-based chemicals. Base on the redox reaction mechanism,the oxidation starch selectively oxidated by periodate of stoiehiometric amount was investigated systematically in this paper.The oxidation of the products can be controlled through oxidant dosage.The relations between the oxidations and yields in the reaction process and in the optimal process conditions were studied in detail.As results,the dialdehyde contents of the products achieved 99.7%and the highest utilization percent of sodium periodate was 95.8%,while the pH was adjusted to 3.5 with dilute sulfuric acid,the reaction time was 6 hours and temperature was 25℃.The product was characterized by IR,SEM and TG analysis.Expensive sodium periodate is the bottleneck which limits the extensive production of dialdehyde starch.In this paper,the technologcial conditions were investigated to improve the utilization percent of periodate.And at the same time,chlorine oxidation method was used to periodate recovery.Al(OH)₃ was used to coprecipitate pefiodate and the periodate recovery increased by 7.9%to 98.5%.Recycle technology of starch oxidated by periodate-periodate recoveried by chlorine oxidation was established.IO₄^- and IO₃^- content were determined by the titrimetric in turn analysis and the effect of pH and Al(OH)₃ dosage was investigated to coprecipitate periodate. It was found that aluminum salt can always circulate in the recycling process by pH regulating only,and the aluminum salt and periodate double recovery cycle can achieve.A novel starch based Schiff base chelating resin,dialdehyde starch thiazole(DASAT) was designed and synthesized.The optimum synthesis conditions of DASAT prepared by DAS-50 were studied in detail and its yield and degree of substitution achieved 86.1%and 0.36.It was characterized by TLC,FT-IR spectra,SEM and TG analysis and the structure of DASAT was correct.Base on this,another five kinds of starch based Schiff base chelating resin were synthesized,and their chelating characters with various metal ions were studied. The DASAT chelating structure on Cu(â…¡)was proved through UV,TG and EPR spectroscopy.The effect factors of DASAT adsorption for Cu(â…¡)ions from aqueous solution were investigated in detail.Adsorption mainly relied on chelation effect,and achieved equilibrium at 2h.In the neutral pH range of 6～7 the adsorbent has a stable maximum binding capacity. Adsorption thermodynamic investigation demonstrated that the adsorption is endothermic and more favorable at high temperatures.The adsorption follows Langmuir adsorption equilibrium isotherm.A novel chelating resin dialdehyde starch melamine(DASME)was designed and synthesized.The effect factors of DASME adsorption for Ag(â… )ion from aqueous solution were investigated in detail.The adsorption reached equilibrium in a short time and the adsorption progress can be described by a second order kinetic reaction.The optimum pH rang was from 4 to 6.The adsorption follows Langmuir-Freundlich isotherm model.The thermodynamic investigation demonstrated the adsorption progress was exothermic and unfavorable at high temperatures.Adsorption process can be carried out spontaneously.