Iron Ion And Formaldehyde Double Crosslinked Multifunctional And Environmentally Friendly Poly Tannic Acid In One Pot Synthesis And Removal Of Pollutants In Wastewater

In recent years,with the rapid development of urban industrialization,more and more pollutants are discharged into the water environment,thus causing serious water pollution problems.At present,the adsorption method is one of the most popular methods to control water pollution.Adsorption technology can be used to effectively treat the pollutant with low concentration,high toxicity and high dispersion in aqueous solution.Environmental functional materials have been widely concerned by people for a long time.They have unique physical,chemical,mechanical and biological properties as well as excellent environmental purification effects.Tannic acid?TA?is a kind of polyphenols,which is widely found in the leaves of plants and the pods of some plants.Tannic acid contains many active functional groups such as hydroxyl and phenolic hydroxyl,which have good adsorption capacity for heavy metal ions.Due to the instability of the polymer formed by the cross-linking of iron ions and tannic acid,formaldehyde was added as the cross-linking agent to improve its stability.At the same time,cysteine was introduced to enrich its functional groups,and Fe³⁺-TA-HCHO polymer was prepared under weak alkaline conditions.Methylene blue,sunset yellow,Pb²⁺,Hg²⁺,AsO₃^2-and Cr₂O₇^2-were selected as target pollutants to test the adsorption performance of tannic acid polymers.?1?The adsorption behavior of Fe³⁺-TA-HCHO polymer on the cation pollutants methylene blue,Pb²⁺and Hg²⁺,as well as the anionic pollutants sunset yellow and AsO₃^2-was investigated.The experimental results showed that the Fe³⁺-TA-HCHO polymer showed good selective adsorption for cationic pollutants and almost no adsorption for anionic pollutants within the pH range studied.Adsorption kinetics experiments showed that the adsorption process of tannic acid polymer on methylene blue,Pb²⁺and Hg²⁺was in line with pseudo-second-order kinetic equation.The adsorption thermodynamics experiments showed that the adsorption process of polymer Fe³⁺-TA-HCHO on these three cationic pollutants was consistent with Langmuir isothermal adsorption model.The maximum saturated adsorption capacities of the three pollutants were 143,819.7 and 699.3 mg/g,respectively.Therefore,Fe³⁺-TA-HCHO polymer has great potential in sewage treatment.?2?The in situ reduction and adsorption behaviors of Fe³⁺-TA-HCHO polymer to Cr₂O₇^2-were investigated.The results showed that the adsorption of Cr₂O₇^2-by tannic acid polymer conformed to pseudo second order kinetic equation and Langmuir equation.The maximum saturation adsorption capacity was 212.8 mg/g.According to the XPS data analysis,Cr₂O₇^2-was first reduced to Cr³⁺by Fe³⁺-TA-HCHO polymer,and then adsorbed by it.In conclusion,Fe³⁺-TA-HCHO polymer has important application value in the removal of heavy metals and organic pollutants.