Adsorption Of Heavy Metals And PFCS On Cotton Based Adsorbents Prepared By Surface-initiated Atom Transfer Radical Polymerization (SI-ATRP)

Polymer adsorption materials are an important branch of functionalpolymer materials, they are of great significance in the theoretical andapplied research. Heavy metals and perfluorinated compounds (PFCs)which are difficult to biodegradation, do great harm to human health andliving environment. Therefore, preparing adsorption materials foradsorbing heavy metal ions and special organic molecules attracts moreand more attention, and is gradually becoming one of the hotPots.Preparation of efficient adsorbents is very important in the field ofsorption, and surface modification can significantly increase the sorptioncapacity of adsorbents. Atom transfer radical polymerization (ATRP)provides an effective method to synthesis controlled structure and newfunctionalized polymer materials. This paper prepared aminated cotton,cotton-g-P(AA-Na)and quaterized cotton via the surface initiated ATRP(SI-ATRP) reaction. The preparation conditions of the adsorbents were optimized, and the material characterizations were conducted. The threeadsorbents were applied to removal of heavy metals and PFCs fromaqueous solution, and the sorption properties and mechanisms werestudied. The main conclusions of this paper were listed below:(1) Successfully prepared the aminated cotton and Cotton-g-P(AA-Na)via SI-ATRP,and optimized the preparation conditions, including theATRP and aminization reaction time. The SEM, FTIR and XPS analysisesproved that the amine and carboxyl groups were grafted on the cottonsurface successfully.(2) The sorption behaviors including sorption kinetics, isotherms andpH effect were investigated. The sorption equilibrium of Cu(Ⅱ) and Pb(Ⅱ)was achieved within1h on the P(AA-Na)-grafted cotton, much fasterthan8h on the aminated cotton. According to the Langmuir fitting, themaximum sorption capacities of Cu(Ⅱ) and Pb(Ⅱ) on the aminated cottonwere2.52and1.1mmol.g^-1, respectively, and on the Cotton-g-P(AA-Na)were2.45and2.44mmol.g^-1, respectively, higher than many adsorbentsreported in the literature. The sorption of Cu(Ⅱ) and Pb(Ⅱ) on aminatedcotton and Cotton-g-P(AA-Na) was pH-dependent, and the sorptioncapacities both increased with the increasing solution pH.(3) Successfully prepared quaterized cotton via SI-ATRP, andoptimized the ATRP reaction time. The sorption equilibriums of PFOS and PFOA were achieved at4h and12h, respectively, much faster thanthat of porous adsorbents. The obtained maximum sorption capacities ofPFOS and PFOA on the quaternized cotton at pH5.0were3.3and3.1mmol.g^-1, respectively. Additionally, solution pH in the range of5-10hadlittle effect on their sorption.(4) SEM, FTIR and XPS analysises proved that the-(CH₃)₂N⁺groupswere successfully grafted on the cotton surface. XPS spectra confirmedthat-(CH₃)₂N⁺groups on the quaterized cotton surface were responsiblefor the enhanced sorption of PFOS and PFOA via ion exchange.