Irradiation Grafting Modification Of Polyethylene Fiber/Fabric For Adsorption Of Metalions

With the rapid development of economy and massive emissions of industry wastewater,contaminations that contain heavy metals enter soil and water resulting in the more serious pollution.Meanwhile,metals in industrial wastewater are considered to be a secondary source and their position in the circumstances of growing shortage of mineral resources is becoming more and more significant.Ion exchange fiber,as a kind of new material for removing metal ions from wastwater,has received increasing attention.The current work focuses on design and synthesis of high-performance adsorbent fibers that have good adsorption selectivity and adsorption efficiency,recyclability,good chemical stability and high mechanical strength.This subject considers the representative metal,like aurum,palladium,uranium and chromium as the target metal ions.A series of adsorbent based on UHMWPE fiber and PE nonwoven fabric were developed for selective recovery of metal ions from aqueous medium via pre-radiation grafting method and subsequent chemical modification.Analytical techniques such as FTIR,TG,SEM and EDS were employed to assess the surface chemical structure,surface morphology and element composition of fibers?nonwoven fabric?before and after modification.The influence of temperature,pH,initial concentration,contact time and multi-components on the equilibrium adsorption time,adsorption capacity and selectivity of the adsorbents was investigated.Additionally,the mechanism of interaction between the adsorbent and metal ions was revealed by XPS analysis and EXAFS.These results provided some new insights into material preparation for the purification of heavy metal-contaminated effluents.The main results of this work include the following aspects:?1?A new chelating polyethylene fiber?UHMWPE-ATZ?was synthesised by the radiation-induced graft copolymerisation of glycidyl methacrylate?GMA?onto ultrahigh-molecular-weight polyethylene?UHMWPE?fibers and subsequent reaction with 4-amino-1,2,4-triazole?ATZ?.The maximum adsorption amount for Au?III?was429.4 mg/g.UHMWPE-ATZ exhibited high selectivity for Au?III?ions and can be used for separation of Au?III?in the multi-ionic aqueous system.The adsorption of Au?III?followed the pseudo-second-order kinetic model controlled by chemical adsorption.The Langmuir model could be used to evaluate the adsorption isotherm of Au?III?onto UHMWPE-ATZ fibers.In particular,this fibrous adsorbent can be regenerated by a treatment in 0.5 M of thiourea and 0.5 M H₂SO₄ solution.The high adsorption capacity can be maintained after at least five adsorption-desorption cycles.?2?Multi-carboxylic ion exchange fiber?UHMWPE-PMDA?was successfully synthesized via further chemical modification of UHMWPE-g-GMA fiber,it was applied to the selective capture of palladium ions from dilute aqueous solutions.The maximum adsorption capacities of UHMWPE-PMDA for Pd?II?in the range of pH 1to 6.Although the concentrations of coexisting ions?Cu?II?,Zn?II?,Cr?VI?,Fe?III?,and Ni?II??were much higher than that of Pd?II?in the solution,the adsorption capacity of the as-prepared adsorbent for Pd?II?was significantly greater than other metal ions.Adsorption process was better fitted by the Langmuir equation with exothermic and spontaneous behavior.Adsorption kinetics of Pd?II?onto the UHMWPE-PMDA follows a pseudo-second order kinetic model.The spectra of EXAFS indicated that O atoms of carboxyl groups directly complexed with Pd?II?ions during the adsorption of Pd?II?on UHMWPE-PMDA fibers.The eluent used for the regeneration of the adsorbent was 0.5 M HCl+0.5 M thiourea.The adsorbent was stable without loss of the adsorption capacity up to at least five cycles.?3?A functional adsorption fiber UHMWPE-AM containing oxygen and nitrogen coordination atoms for trace uranium extraction from wastewater was obtained by pre-irradiation grafting method.The adsorption efficiency is optimal at pH 4.0 and the removal rate of U?VI?reached over 99%.Adsorption kinetics of U?VI?on UHMWPE-AM was well described by the pseudo-second-order model and the adsorption equilibrium data obeyed the Langmuir model.EXAFS and SXAS analysis suggested that U?VI?was adsorbed on the fiber in the form of UO₂²⁺and N atoms mainly participated in the UHMWPE-AM complexation with U?VI?.UHMWPE-AM fiber still retained a high removal rate of the trace uranium ions from water after a long-time of acid treatment,which may be expected to reuse for several successive adsorption/desorption cycles.?4?A novel quaternary ammonium polyethylene nonwoven fabric for removing chromium ions from water was prepared by the pre-irradiation grafting process for removal of chromium ions from aqueous solution.It was showed that QAPENF has a high adsorption capacity for Cr?VI?ions over a wide pH range,and the maximum removal of Cr?VI?was 99.2%at pH 3.The dominant coordination mechanism of Cr?VI?on the QAPENF was ascribed to ion exchange combined with electrostatic interaction.The isotherm adsorption of Cr?VI?was well described by the Freundlich model.QAPENF can partially reduce Cr?VI?to less-toxic Cr?III?during the adsorption process.The excellent performance of QAPENF in collecting Cr?VI?from electroplating wastewater showed that the residual Cr?VI?concentration decreased from 350 mg/L to 2 mg/L in 48 h.QAPENF was also found to be reusable when 0.5M NaOH was utilized as the eluting agent.