Effect Of Ligands On Cu(?)of Polymer-based Hydrous Ferric Oxide Nanocomposites:Behavior And Mechnism

Nano-Fe(?)-encapsulated hybrid adsorbents were synthesized by incorporating HFO nanoparticles within two polymer supports(negatively charged PS-and neutral PS0)based on wet impregnation.The resultant hybrid adsorbents combine excellent mechanical strength and flow characteristics of polymeric resins with specific adsorption affinity of HFO toward target pollutants.Herein,the effect of sulfate on Cu(II)adsorption to polymer-based hydrous ferric oxide nanocomposites was examined,and the underlying mechanism was probed with the aid of X-ray photoelectron spectroscopy.In addition,surface complex modeling(SCM)was employed to describe the adsorption process,and column adsorption as well as the mathematically modeling was further conducted to examine the role of sulfate.On the other side,the effect of oxalate on the dissolution of the immobilized HFO inside polymer was investigated to understand the stability of the nanocomposites for practical application.Cu(?)adsorption onto the bare HFO was promoted obviously in the presence of sulfate.However,the effect of sulfate on Cu(?)sorption to HFO nanocomposites was largely dependent on the surface properties of the hosts.An evident increase of Cu(?)adsorption in sulfate was observed for hybrid HFO-PS0 binding neutral chloromethyl groups.But for HFO-PS-,it exhibited an apparent decrease in Cu sorption when Na2SO4 was added.It was attributed to the competing effect of Na+ and the Cu-SO4 complexation in solution.By contrast,the adsorbed Cu(?)was increased by introducing sulfate in the background Ca2+,because sulfate was allowed to access to the loaded HFO nanoparticles due to the screening of the sulfonate groups caused by Ca ions.XPS spectra demonstrated that the formation of Cu-SO4 ternary complexes play a dominant role in enhanced Cu adsorption on both bulky HFO and the hybrid HFO sorbents in the presence of sulfate.Based on the macroscopic experimental data,the Constant Capacitance Model(CCM)was developed to describe the adsorption edges in the presence of sulfate successfully.The modeling results obtained under varying Cu/Fe ratios further proved the applicability of CCM model.In addition,the weak site density decreases from 20%Fe of bare HFO to 5%Fe after being immobilized,possibly related to pore blockage.The formation of Cu-SO4 ternary complexes on the surface of HFO nanocomposites was demonstrated by surface complex modeling.Effect of sulfate on Cu(?)adsorption by HFO composites was examined in column runs.The presence of sulfate in solution significantly improved the effective treatment volume by HFO-PS0.The influence of flow rate,inlet concentration,and column length on breakthrough curves was investigated and fitted by Adams-Bohart,Clark,Thomas,BDST models.Thomas model seems be the most suitable one to predict breakthrough curves,and the rate constant kTh,and adsorption capacity qTh shows linear relation with flow rate,KTh=6.17×10-4v-4.63×10-3,qTh=-5.62v+5.093.Besides,a linear relation was obtained between the breakthrough time and column length in the sulfate systems based on the BDST model,implying it could be used to predict the breakthrough time for Cu(II)sorption onto hybrid sorbent.Effect of oxalate on the dissolution of HFO nanocomposites was investigated to understand their stability for practical application.As compared to the bare HFO,the dissolution rate was considerably slower for the composites,which is consistent with the slower oxalate adsorption by the composites.PS-binding sulfonate groups was more favorable than PS0 binding choromethyl groups for HFO dispersion,resulting in higher oxalate uptake and faster dissolution rate of HFO-PS-than HFO-PS0.The initial HFO dissolution rate of the composites in 0.1 M KNO3 systems was apparently greater than that in 0.01 M KNO3 systems,whereas insignificant effect of ionic strength was imposed on the bare HFO.In the presence of visible light irradiation,an obvious photochemical reduction of Fe(?)into Fe(?)was observed for the bare HFO,which greatly promoted the iron leaching from solid to solution.However,such photoreduction was weakened for both nanocomposites because the solid polymers keep the inside HFO nanoparticles from light irradiation.