Preparation And Photodegradation Performance Of Polyvinyl Alcohol Phytate(PPVA)and Its Silver Salt

The polyhydric high molecular compounds include natural extraction and artificial synthesis.Most of the polyhydroxy polymer compounds have poor solubility,such as po-lyvinyl alcohol,cellulose,and starch.Although some of them can be dissolved,their slow speed,especially the dissolution of cellulose has always been a hot and difficult problem.With the advancement of science and technology and the increasing demand for renewable new materials in various countries,natural polyhydroxy polymer compounds such as starch and cellulose have become the best raw materials.Therefore,it has become the consensus of the people to modify polyvinyl alcohol,cellulose,starch,and other polyhydroxy poly-mer compounds and improve their water solubility to increase their added value.The ex-isting dissolving technology also has the disadvantages of serious environmental pollution,high energy consumption and high production cost.So its modification has always been a research hotspot in various countries.Phytic acid is a compound containing polyphosphoric acid groups.In the process of phosphorylation,Phytic acid is a compound containing a po-lyphosphoric acid group.During the phosphorylation process,since the side chains of po-lyvinyl alcohol,starch,and cellulose all contain hydroxyl functional groups,esterification reaction can occur with the phosphate group in phytic acid.The modification changes the molecular structure of the polymer,intramolecular and intermolecular interactions,and changes the solubility of the polymer.Photocatalytic oxidation technology has many advantages,such as mild reaction conditions,fast reaction speed,non-selective oxidation,and the ability to completely mineralize organics into CO2 and H2O.Therefore,photocatalytic oxidation technology has been widely used in wastewater treatment.Among the modified catalysts,Ag3PO4 is favored because of its small band gap,high photocatalytic activity and high quantum yield.However,its poor stability,high cost,and other defects caused by its photo-corrosion problems limit its further application.Based on the above two points,the main contents of the work are as follows:Phytic acid modified polyhydroxy polymer,to improve its solubility properties,and the use of the synthesized PPVA to prepare its silver salt(PPVA-Ag),and its use in photo-oxidation degradation dye wastewater research.The main research work and conclusions are as follows:(1)Exploring the synthetic route of the experiment,using phytic acid to modify PVA,successfully synthesized polyvinyl alcohol phytate.The structure of the product was represented by 31P-NMR,FT-IR and TG.The phosphate group was identified in the product.The morphology of the polymer was characterized by SEM and TEM.The results showed that the polymer was a porous spherical material.The effects of different reaction conditions on the esterification reaction were explored through single-factor experiments.Based on the results,an orthogonal experiment was designed to obtain the best combination of the highest degree of esterification of the synthetic polymer.The results were as follows:PVA 0.8 g,phytic acid dosage 14 mL,the amount of urea 5 g,the amount of dicyandiamide 2 g,the reaction temperature of 110?,the reaction time 2 h,the highest degree of esterification of the product was 85.56%.The results of orthogonal experiment were analyzed very poorly and intuitively.The influence of various factors on the esterification degree of the reaction product was obtained as follows:temperature>dicyandiamide content>urea content>phytic acid dosage;the deviation analysis results were consistent with the visual analysis.(2)PPVA-Ag photocatalyst was successfully prepared by precipitation method.The molecular structure and morphology of the sample were characterized by FT-IR,SEM and TEM.The results showed that the polymer contained phosphate groups and was a porous spherical material.The optical properties of the catalyst were characterized by UV-vis DRS.It shows that the main absorption band of the catalyst is the ultraviolet region,but there is also some absorption in the visible region;this is used to photodegrade rhodamine B simulated wastewater.The experimental results show that under simulated visible light,PPVA-Ag photocatalyst can completely degrade 50 mg/L rhodamine B at 21 min,and the TOC removal rate reaches 66.05%.Free radical capture experiments show that hydroxyl radicals is the main active species for photocatalytic degradation of rhodamine B,and the possible photocatalytic mechanism is discussed.In addition,The PPVA-Ag photocatalyst has high stability,and its photodegradation performance remains above 90%after 4 cycles.(3)Starch phytate and cellulose phytate were prepared using the optimal combination of synthetic polyvinyl alcohol phytate;the molecular structure and thermal stability of the polymer were characterized by FT-IR,31P-NMR and TG.The results show that the polymer contains phosphate groups,indicating successful synthesis of the target product.The este-rification degree and solubility of the product were analyzed.The results showed that the esterification degree of the starch phytate was 79.42%,the solubility was 18.3 g;the esteri-fication degree of the cellulose phytate was 73.57%,and the solubility was 16.8 g.