Study On The Adsorption Of Heavy Metal Elements By Functional UHMWPE Fiber

The large-scale mining,smelting and use of mineral resources have caused a large amount of industrial wastewater to be discharged into the environment,polluting water sources and soil,and increasing harm to ecosystems.In addition,mineral resources are non-renewable resources,and are increasingly scarce,and the importance of extracting and recovering metal resources from wastewater is becoming increasingly prominent.The treatment of wastewater containing metal ions can not only protect the environment but also improve the utilization of resources.The adsorption method is a widely used method for extracting metal ions from wastewater.The key lies in the development of suitable adsorption materials.As a new type of adsorption material,polymer adsorption fiber has the characteristics of good mechanical properties,wear resistance,corrosion resistance,and easy regeneration.It has attracted increasing attention in the application of metal ions in wastewater treatment.The development and preparation of high-performance fibers with good adsorption properties,high mechanical strength,high selectivity and good stability are current research goals.In this thesis,gold,chromium and uranium ions in typical wastewater were selected as the treatment objects,and ultra-high molecular weight polyethylene?UHMWPE?fiber was used as the substrate to prepare fiber adsorption materials with functional groups by radiation grafting technology.The static adsorption method was used to evaluate the influence of the pH value of the solution,initial metal ion concentration,and adsorption time on the adsorption performance of the fiber adsorption material.X-ray absorption fine structure?XAFS?spectroscopy,synchrotron radiation Fourier transform infrared?SR-FTIR?spectroscopy and other analytical methods were used to study the interaction mechanism between fiber materials and metal ions in the adsorption process at the molecular/atomic scale.The research results of this paper can provide theoretical guidance for the design and improvement of polymer adsorbent materials,and also provide a new way for the treatment of wastewater containing uranium and other metal ions.The main research contents of the thesis are as follows.Preparation of amidoxime modified ultra-high molecular weight polyethylene fiber?UHMWPE-g-PAO?and 4-amino-1,2,4-triazole modified ultra-high molecular weight polyethylene fiber?UHMWPE-g-?GMA-ATZ??using radiation grafting technology.The adsorption properties of two fibers for Au???in aqueous solution were discussed.The study found that the pH value of the solution has a great influence on the adsorption of Au ions.When the pH value of 1⁴,UHMWPE-g-PAO fiber has higher adsorption efficiency for Au???.At pH=3,the adsorption efficiency reached 98.7%and the adsorption process was consistent with the Langmuir and Freundlich adsorption isotherm models.Compared with the research results of Au?III?adsorption by UHMWPE-g-?GMA-ATZ?fiber,it is shown that UHMWPE-g-PAO achieves higher adsorption efficiency in a wider range of pH value,and at the optimal pH value,UHMWPE-g-PAO fiber can achieve the same adsorption efficiency for higher concentrations of Au?III?.The analysis results of XANES and FTIR indicate that the adsorption mechanism of Au???by the two fibers is based on the reaction of Au???with reducing groups during the adsorption process,which is reduced to gold element and loaded on the fiber.Through fiber sintering,gold recovery is achieved.UHMWPE-g-PAO fiber was used to study the adsorption of Cr???in solution.The results show that UHMWPE-g-PAO has a good adsorption effect on Cr???under strong acidic conditions.At pH=2,the maximum adsorption capacity of Cr???reached 246 mg/g.The fiber exhibits good adsorption selectivity for chromium in wastewater,and is hardly affected by metal cations such as Ni?II?,Cu?II?and Zn?II?.XANES analysis results show that UHMWPE-g-PAO has a good reduction ability for Cr???,and the chromium form on the fiber is mainly Cr???.EXAFS and FTIR results show that during the adsorption process,Cr???reacts with the amino group in the amidoxime group on the fiber and is reduced to Cr???.Then,Cr???complexes with the nitrogen and oxygen atoms in the two amidoxime groups and the oxygen atoms in the two water molecules to form the octahedral structure.UHMWPE-g-PAO fiber was used for the adsorption study of U?VI?in uranyl nitrate?UO₂?NO₃?₂·6H₂O?solution.The results show that the adsorption efficiency has a strong correlation with the pH value of the solution and the coordination structure of U?VI?changes with the pH value.At pH=4,the fiber has the best adsorption performance for U???,and the maximum adsorption capacity is about 186.7 mg/g.Fiber has a high adsorption selectivity for uranium in uranium mine wastewater and is basically not affected by iron,titanium,aluminum,chromium,gold,manganese and other metal ions.XANES,EXAFS and FTIR analysis results show that U?VI?is in the form of UO₂²⁺complexed with the N of the amino group and O of the hydroxyl group in amidoxime group and water molecules to form a stable structure.