Research On Functional Modified Cellulose For Adsorption And Fluorescence Detection Of Pollutants In Wastewater

Cellulose is a natural polymeric material that is a wide range of biodegradable,environmentally friendly materials.In this experiment,chemical pulp cellulose was used as raw material to prepare glutamic acid modified cellulose（GMC）,anthracene boronic acid fluorescent probe modified cellulose（FMC）and naphthalimide modified graphene oxide cellulose composite membrane（NGC membrane）.We studied the application effect of the three kinds of functional materials.The microstructures of the three materials were observed by scanning electron microscopy.Elemental analysis and infrared spectroscopy were performed before and after synthesis of the modified materials to prove the success of the synthesis reaction.In this experiment,TEMPO-oxidized cellulose（TOC）was oxidized by TEMPO/NaBr/NaClO oxidation system and its carboxyl content was 1.2mmol/g as determined by conductivity method.Under mild conditions,water-soluble 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide（EDC）asacatalyst,adding N-hydroxysuccinimide（NHS）,GMC was synthesized by amidation of the carboxyl group with glutamic acid.The effects of Cu²⁺and Hg²⁺on the adsorption were experimentally tested,and the optimum adsorption conditions were discussed.When the adsorption temperature is 65℃,the adsorption efficiency is the best.When the initial concentration of Cu²⁺and Hg²⁺is less than 50ppm,the adsorption rate can reach more than 90%.The maximum adsorption capacity of of Cu²⁺and Hg²⁺was 45 mg/g and42 mg/g respectively when the initial concentration at 200 ppm.The fitting results of the adsorption data model show that the adsorption of GMC conforms to the pseudo-second-order kinetic model and the Langmuir isothermal adsorption model.In addition,the competitive adsorption of Cu²⁺and Hg²⁺in the two ions system was studied.The results showed that compared with the single ion system,competitive adsorption was observed and the total adsorption capacity increased.Fluorescent probes have high sensitivity,fast and non-destructive fluorescence etc.,therefore,it can instantly detect the ions in the water.The method of preparing GMC is used to replace glutamic acid with anthracene boronic acid fluorescent probe to synthesize FMC.FMC is also an efficient adsorbent material,and the F^-can be simultaneously detected in water.The experimental results show that FMC has the characteristics of high sensitivity and specificity for the F^-response in water.Fluorescence intensity increases with F^-concentration.When the F^-concentration in the system is 10ppm,the fluorescence intensity at 417nm has a 13%improvement.The experiment also tested the adsorption ability of F^-,the results show that the pH value of the solution has little effect on the adsorption,adsorption cost 5-10 minutes to reach equilibrium,the adsorption capacity can reach 8 mg/g when F^-initial concentration is10 ppm.The mixed solution of alkali and urea is a green cellulose dissolving solution,and the cellulose solution prepared by dissolving the cellulose in this solvent can be used to prepare a cellulose flat membrane using a wet membrane process.Cellulose membrane and fluorescence probe can be well combined to remove and detect heavy metals in water.The effects of the addition of GO on the film formation were investigated experimentally.The contact angle measurement and BET characterization demonstrated that the incorporation of GO enhanced the hydrophilicity and specific surface area of the cellulose film.The NGC membrane prepared by combining the GO cellulose composite membrane and the naphthalimide fluorescent probe has good trapping effect on the most of heavy metal ions and is an ideal Cu²⁺detection membrane.NGC membrane itself almost has no fluorescence,after adding Cu²⁺,the fluorescence was significantly enhanced.When the concentration of Cu²⁺reached 100μM,the fluorescence emission spectra of fluorescence at 510nm increased more than 12 times.At the same time,the removal efficiency of Cu²⁺was tested.As Cu²⁺concentration increased from 10ppm to 200ppm,the removal rate of Cu²⁺by NGC was between 99%and 56%.