Extraction Of Chitosan From Maggot Shell And Preparation Of CS/TiO₂/PVDF Blended Ultrafiltration Membrane

Ultrafiltration technology is widely used in many fields as an efficient separation method.Polyvinylidene fluoride?PVDF?has the advantages of high mechanical strength,good chemical stability,etc,which is the most commonly used ultrafiltration membrane material.However,the serious hydrophobicity of PVDF severely limits the development of PVDF in membrane materials.At present,PVDF modified materials are mainly divided into organic materials and inorganic materials,but each has certain limitations.At present,the method of improving the comprehensive performance of the membrane by combining the organic and inorganic materials has become a research hotspot for the study of membrane modification.In this paper,chitin was extracted from the maggot shell by acid-base method,and chitosan was prepared by removing the acetyl group of chitin in lye method.According to the ash content,nitrogen content,molecular structure and microstructure of chitin,the ash content of chitin was 0.997%and the nitrogen content was5.829g/100g.The degree of deacetylation,molecular structure,viscosity,element content,acid insolubles and microstructure of chitosan were characterized.The deacetylation reaction was finally determined by a two-step method,and the degree of deacetylation of chitosan prepared was 92.2%.The viscosity is 922.3cm³/g,the acid insoluble matter is?1.0%,and the element containing no arsenic or lead has reached the national standard.Nano-titanium dioxide?TiO₂?and extracted chitosan?CS?were blended with PVDF,and the TiO₂/PVDF and CS/PVDF ultrafiltration membrane was prepared by immersion precipitation phase transfer method.The effects of different TiO₂ and CS contents on the microstructure and properties of TiO₂/PVDF and CS/PVDF blend films were investigated.The results show that when 1.0wt%nano-titanium dioxide is added,the water flux can reach 678.9 L·m^-2·h^-1,and the rejection rate is 78.5%and the water contact angle is 67.2°.The overall performance of CS/PVDF membrane was the best when 0.2wt%chitosan was used.The water flux was 510.9 L·m^-2·h^-1,the interception rate was 83.2%,and the water contact angle was 69.7°.Using PVP and LiCl as additives,nano-titanium dioxide,chitosan and PVDF were blended to prepare CS/TiO₂/PVDF blended ultrafiltration membrane,which was tested by water flux,SEM test and recovery rate.The properties of the ultrafiltration membrane such as permeability and antifouling properties and the microstructure of the membrane were characterized.The results show that when the fixed CS content is0.2wt%,the TiO₂ doping amount is 1wt%,and the water flux can reach 694.4L·m^-2·h^-1,and the rejection rate is 82.8%.The contact angle is 64.5°.