Hydrolysis, Properties And Applications Of Peach Gum Polysaccharide

Peach gum(PG), a kind of natural polysaccharide gum with poor water-solubility, is produced from the fruit and trunk of peach tree(family Rosaceae) as a consequence of physiological process and mechanical injury. However, poor performance of the crude peach gum(CPG) make it unattractive for application, and thereby causing serious waste of PG resource. In this thesis, CPG was studied as research center. The adsorption performance and hydrolysis mechanism of CPG, and the properties and applications in related fields of hydrolyzed peach gum polysaccharide(HPGP) were systematically studied. Details are as follows.(1) The dye in aqueous solution was successfully removed by using CPG as a natural adsorbent. The results showed that CPG showed high adsorption capacity and selectivity for cationic dyes(e.g., methylene blue(MB) and methyl violet(MV)) in the pH range 6-10. For MB and MV dyes, the adsorption capacity on CPG can reach as high as 298 and 277 mg/g, respectively, and meanwhile the adsorption process can reach equilibrium within 30 min. The dye adsorption process followed the pseudo-second-order kinetic model and Langmuir isotherm model. It was found that CPG could be well regenerated in acid solution. The recovered CPG still exhibited high adsorption capacity even after five cycles of desorption-adsorption.(2) The HPGP with excellent water solubility was prepared by hydrolysis of CPG at acidic condition. A hydrolysis mechanism is proposed by monitoring the hydrolysis efficiency and morphological change of CPG, and the intrinsic viscosity of resulted HPGP as a function of hydrolysis time. FTIR and ζ-potential measurements revealed that HPGP with multiple carboxylic group was negatively charged in water in the pH range 3-11. The HPGP exhibited remarkable pH and ionic strength responsibility, as proven by DLS and AFM measurements. Moreover, the layer-by-layer self-assembly experiments further confirmed that the HPGP can be utilized as an anionic polyelectrolyte. Besides, the transformation of the functional groups of HPGP using chemical modification was preliminarily studied, and the obtained results could provide scientific theory for furhter improvment of the performance of CPG.(3) A variety of inorganic nanoparticles such as silver halide nanoparticles and noble metal nanoparticles were successfully synthesized by using HPGP as stabilizer. TEM and XRD characterizations indicated that the obtained inorganic nanoparticles possess small sizes(The mean diameter of the silver halide nanoparticles and noble metal nanoparticles were 2-5 nm and 4-10 nm, respectively.), good dispersibility and high crystallinity. The organic composition and content on the surface of the inorganic nanoparticles were determined by FTIR and TGA measurements. Meanwhile, we found that the size of the noble metal nanoparticles can be easily tuned by adjusting the feeding ratio. In addition, the catalytic performance for degradation of rhodamine B and reduction of p-nitrophenol were studied by using HPGP-AgBr and HPGP-Au as catalyst, respectively. The results demonstrated that both of the HPGP-AgBr and HPGP-Au nanoparticles had high catalytic activity.