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Arsenate Adsorption By Hydrous Ferric Oxide Nanoparticles Embedded In Cross-linked Anion Exchanger:Effect Of The Host Pore Structure

Posted on:2017-09-13Degree:MasterType:Thesis
Country:ChinaCandidate:H C LiFull Text:PDF
GTID:2491304838473434Subject:Environmental Engineering
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Excessive arsenic in water remains a great concern for people all over the world.Nanoscale ferric oxides(NFO)have attracted increasing attention due to their huge surface area and high affinity to arsenic.However,the ultrafine nature hindered the practical application of NFO severely.It is promising to prepare NFO composite by means of loading NFO into porous carriers.Macroporous anion exchangers were one of the most popular carriers due to their high chemical stability,desirable mechanical strength and ideal hydraulics performance.Besides,charged property of exchanger would pre-concentrate anionic contaminants within solid phase because of Donnan effect.Recently,increasing interests have arisen concerning the effect of the pore size of porous host on the morphology,chemical property and adsorption performance of the confined nanoparticles.However,few studies have systematically elucidated the effect of the host pore structure on the surface chemical properties of the confined nanoparticles and the arsenate adsorption performance by the composite.In this study,three anion-exchanger(NS)with different pore structure were fabricated via post-cross-linking reaction followed by amination reaction.Afterwards,three composite adsorbents(HFO-NS)were synthesized via in-situ confined growth of hydrous ferric oxide(HFO)nanoparticles within corresponding NS.The effect of the host pore structure on the morphology,particle size,as well as the surface chemical properties of the confined HFO nanoparticles and the arsenate adsorption performance by the HFO-NS composites were systematically investigated under different solution conditions.The size of HFO nanoparticles can be regulated by tailoring the pore structure of NS host.With the decrease in the average pore size of the NS hosts from 38.7 to 9.2 nm,the mean diameter of the confined HFO nanoparticles was lessened from 31.4 to 11.6 nm,while the density of active surface sites was increased due to size-dependent effect which result to the enhanced adsorption of As(V)over a wide pH(from 3 to 10)as well as in the presence of different competing anions(Cl-,NO3-,SO42-and HCO3-,0-800 mg/L;PO43-,0-10 mg/L).In addition,the fixedbed working capacity increased from 2200 to 2950 bed volumes(BV)owing to the size confinement effect,which did not have adverse effect on the desorption of As(V)as the cumulative desorption efficiency reached 94%with 10 BV of binary solution(5%NaOH+5%NaCl)for all the three adsorbents.Therefore,this study provided a promising strategy to regulate the size of the nanoparticles and improve the reactivity of composite.
Keywords/Search Tags:Arsenic contaminant, nanocomposite, hydrated ferric oxide, size confinement effect, ion exchanger
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