Radiation Modification Of Polyethylene Fiber/Nonwoven Fabric For Adsorption Of Uranyl And Platinum Ions

The enrichment and recovery of rare metal ions from aqueous solution have been one of the research hotspots and key issues.On the one hand,the decreasing mineral reserves and increasing demand of precious metals have promoted the recycling of secondary metal resources;On the other hand,heavy metal ions in industrial wastewater needed to be separated reasonably to avoid harming the ecological environment and human health.Polymer fibrous adsorbent has become one of the promising adsorbents due to its excellent adsorption ability,mechanical properties and operability.Uranyl ions and platinum ions were used as representative target metal ions in this work.Based on substrates including ultra-high molecular weight polyethylene(UHMWPE)fibers and polyethylene-coated polypropylene skin-core(PE/PP)non-woven fabrics,two kinds of polymer adsorbents with good enrichment capacity to specific metals were synthesized by radiation-induced graft polymerization(RIGP)and subsequent chemical modification.The element composition,chemical structure,surface morphology and adsorption capacity of the adsorbents were investigated in this work.The main results are as follows:(1)A functional chelating fiber(UHMWPE-AO)was synthesized by pre-radiation grafting of acrylonitrile(AN)and methacrylic acid(MAA)onto UHMWPE fiber with following amidoximation and KOH treatment,for the purpose of removing uranium from aqueous solution containing fluorine and uranyl ions.The chemical structure,elemental composition and micromorphology of the pristine and modified UHMWPE fibers were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and scanning electron microscope(SEM),and the results showed that UHMWPE-AO fiber was successfully synthesized.The effects of initial uranium concentration,contact time,and dosage of UHMWPE-AO fibers were investigated by static adsorption experiment in the simulated wastewater.The results showed that the UHMWPE-AO fiber has good affinity with uranyl ions and the adsorption capacity can reach 152 mg/g.The sorption data was in accordance with the pseudo-second-order kinetic model and Langmuir isothermal adsorption model,which indicated the mechanisms of monolayer chemisorption.The concentration of uranyl ions in simulated wastewater can decrease from 40 mg/L to 16 ?g/L after sorption by 2 g/L adsorbent,which was in line with Chinese uranium-containing wastewater discharge standards(the uranium content should less than 50 ?g/L).(2)Multi-amino ion exchange non-woven fabric(PE/PP-PEI)was synthesized by radiation-induced grafting of glycidyl methacrylate(GMA)onto PE/PP non-woven fabric and the subsequent modification with polyethyleneimine(PEI)for recovering platinum from aqueous solution.Characterization methods including FTIR,XPS,SEM,EDS and thermogravimetric analysis(TG)were used to investigate the chemical structure,elemental composition,surface morphology and thermal stability of the pristine and modified PE/PP non-woven fabric.The effects of initial pH,initial platinum concentration,adsorption time,co-existing metal ions,and amount of adsorbent on the platinum adsorption performance were investigated by static adsorption experiments.The results showed that the adsorbent has similar and high adsorption capacity for platinum ions between pH range of 3 to 6;The pseudo-second-order kinetic model and Langmuir isothermal adsorption model can better describe the adsorption of platinum ions by PE/PP-PEI non-woven fabric,and the adsorption capacity can reach 485 mg/g;The modified non-woven fabric had better adsorption selectivity for platinum ions in the coexistence of multiple metal ions including Ni(?),Cu(?),Co(?),Mg(?),Pb(?)and Zn(?);The platinum concentration can reduce from 105.04 mg/L to 5.12 mg/L with the removal rate reaches 95.13% by using 2 g/L adsorbent.The PE/PP-PEI non-woven fabric had good recovery capacity for platinum in Pt-Ni/C catalyst.