The Synthesis Of Novel Polyacrylonitrile Chelatingcolor Fibers And Their Application In Rapid Detection Of Heavy Metals In Agricultural Products

The rapid development of Science,Technology and economy promote China’s Industrial modernization process,it brings convenient city life and considerable economic benefits.However,it causes serious problems of environmental pollution and destroys our ecological environment.This causes the pollution of heavy metals.Heavy metal pollution has become a severe test in food quality and safety.The production and processing process of agricultural products are particularly affected by external environment,so heavy metal pollution in environment will easily lead to excessive heavy metals in agricultural products.In a word,we need to have an evaluation and testing of the safety of heavy metals in agricultural products.Enormous samples to be detected and low detection threshold are features of heavy metal detection in agricultural products,so it’s greatly significant to establish a fast test speed and sensitive detection method.This paper introduces commonly used detection methods for heavy metal and scope of various types of methods,describes the preparation of modified polyacrylonitrile fiber and its chelation of heavy metals.We aimed at establishing a new method to detect heavy metal quickly by polyacrylonitrile chelating color fiber.We used polyacrylonitrile fiber as substrate materials to modify chemically.After the chemical modification,it was applied to heavy metal adsorption and desorption experiments,and we could use FT-IR and SEM to explore its adsorption mechanism.Screening out chelating fibers which have efficient,specific and adsorptive property and grafting metal indicator which could respond quickly to changes in the concentration of heavy metals,a new heavy metal discoloration fiber was synthetized and it was used for rapid detection of heavy metals in agricultural products.The main contents and experimental results are as follows:1.Using polyacrylonitrile fiber as substrate materials to modify chemically and grafting eleven kinds of organic ligands containing different functional groups,we could screen out four chelating fiber AHTF,IAHF,AMTF and ABDF with high conversion rate according to the size of the conversion rate from 11 synthetic fibers.Using EA to explore further how the three factors of solvent varieties,synthetic temperature and molar ratio had influence on the AHTF,IAHF,AMTF,ABDF conversion rate,we could determine the optimal synthesis process.The conversion rate of chelating fiber AHTF,IAHF,AMTF and ABDF were respectively 44.32%,40.64%,36.87%and 30.38%,functional group content are 4.40mmol/g,3.42mmol/g,3.50mmol/g and 2.93mmol/g.Using FT-IR and SEM to analyze the synthetic route of chelating fibers,we could reckon that polyacrylonitrile fibers can go on addition reaction by pro-cyano-active functional groups on its molecular structure and organic heterocyclic ligand which carries amino group.The reaction only had bond breaking and no atoms loss,which met the requirement of green chemistry.2.Chelating fiber adsorption capacity to six common heavy metal ions in agricultural products was studied,and the adsorption capacity of two chelating fiber AHTF and IAHT to Hg(Ⅱ)were further screened out,and the focus were adsorption and desorption processes.The experiments of Static adsorption and desorption showed that AHTF and IAHF possess a strong selective adsorption capacity to Hg(Ⅱ),and optimum adsorption pH were respectively 6.5 and 5.5,and adsorption capability were 183.7 mg/g and 198.3mg/g.The experiments also indicated that 3 mol/L HNO3 was able to completely desorbed chelating fiber AHTF which adsorbed Hg(Ⅱ),and 3 mol/L HCl could completely desorb chelating fiber IAHF which adsorbed metal ions Hg(Ⅱ).Adsorption kinetics fully illustrated that chelating fiber AHTF and IAHF had a faster speed of adsorption,and fiber reuseexperiments fully described chelate fibers had well renewable capacity.Using TGA and SEM to characterize polyacrylonitrile chelating fiber IAHF and AHTF,we could demonstrate that chelating fiber could adsorb Hg(Ⅱ).The result of TGA also indicated that IAHF and AHTF had good stability.3.A metal indicator was grafted to chelating fiber AHTF and IAHF via Mannich reaction to prepare color fiber AHTF-PAR and IAHF-PAR which respond rapidly to heavy metal and applied them to rapid detection of trace heavy metals in agricultural products.The experiment proved that color fiber had high stability and a good chromogenic effect over a wide pH range.Using Adobe Photoshop CC software eyedropper tool to create standard shade guide of different gradient Hg(Ⅱ)concentration,which measured the content of Hg(Ⅱ)in four categories of agricultural products,and this method basically accorded with the test result of ICP-AES.