Preparation Of Heavy Metal Adsorption Materials By Radiation-modified Ultra-high Molecular Weight Polyethylene

The vigorous development of new energy makes the demand for heavy metal resources in industrial production increase day by day.Heavy metals such as copper（Cu）,cobalt（Co）and nickel（Ni）are toxic and non-biodegradable,which can cause pollution to water,soil and even the whole biosphere.Hence separation of heavy metals in industrial waste is very important for the environment and human health.Moreover the decreasing reserves in natural minerals also gradually promote the secondary recycling of heavy metal resources.Modified polymer fiber adsorbent has a broad development prospect in the treatment of industrial wastewater containing heavy metal ions due to its simple preparation,good mechanical properties,excellent adsorption capacity and regeneration capacity.In this study,functional groups are introduced onto ultra-high molecular weight polyethylene（UHMWPE）fiber by radiation grafting and chemical modification to produce the efficient polymer adsorbent.The adsorption of Cu（II）/Co（II）/Ni（II）ions common in industrial wastewater was studied.The main contents are as follows:The monomer（AA、AM or AN）is separately grafted onto the UHMWPE fiber by⁶⁰Co-γray-induced co-irradiation grafting or pre-irradiation grafting.The binary monomer（AA and AM）is grafted on the UHMWPE fiber by co-mixed grafting or secondary grafting.The monomer grafted fiber was characterized by SEM,FTIR,XPS and DSC.Through batch experiments under the conditions of irradiation dose,reaction time,monomer concentration,polymerization inhibitor dosage and reaction temperature,the maximum grafting rate of AA、AM and AN onto UHMWPE fiber was respectively 500%,86%and 7%.The grafting rate by co-mixed grafting AA and AM was much lower than the maximum grafting rate,instead the grafting rate by secondary grafting AA and AM was greatly improved compared with the maximum grafting rate.The AA and AM were successively grafted onto UHMWPE fiber by secondary grafting,then the amide group on fibers was oximized,so that the chelating fiber（UHMWPE-HO）containing oxime and carboxylation was prepared.UHMWPE-HO was characterized by SEM,FTIR and TGA.The influence of p H value,adsorption time,starting concentration,elution cycles and adsorbent dosage on the heavy metal adsorption was investigated in Cu（II）/Co（II）/Ni（II）-contained wastewater.The results show that the adsorption capacity of the UHMWPE-HO fiber to Cu（II）,Co（II）and Ni（II）ions was 318mg/g,165mg/g and 140mg/g.The time-dependent change of adsorption was more closely matched with pseudo-second-order kinetic model,while starting concentration-dependent change of adsorption was more consistent with Langmuir isothermal adsorption model.The above proves that adsorption on fibers was a monolayer adsorption dominated by chemical adsorption.The removal rate of Cu（II）,Co（II）and Ni（II）ions was respectively 99.5%,40.5%and 43.5%in simulated mixed heavy metal ions with 3g/L adsorbent.The AA and AM are successively grafted onto UHMWPE fiber,then the amide group on fibers was converted to dithiocarboxylic,so that the chelating fiber（UHMWPE-DTAM）containing dithiocarboxylic and carboxylation was prepared.UHMWPE-DTAM fiber was characterized by SEM,FTIR and XPS.The influence of p H value,adsorption time,starting concentration,elution cycles and adsorbent dosage on the heavy metal adsorption was investigated in Cu（II）-contained wastewater.The results show that the adsorption capacity of UHMWPE-DTAM fiber to Cu（II）ions can reach 285mg/g.The time-dependent change of adsorption was more closely matched with pseudo-second-order kinetic model,while starting concentration-dependent change of adsorption was more consistent with Langmuir isothermal adsorption model.The above proves that adsorption on fibers was a monolayer adsorption dominated by chemical adsorption.The removal rate of 500mg/L Cu（II）ion solution was 98.2%with 4g/L adsorbent.