Magnetic Responsive ?-Cyclodextrin Organic Phosphonic Acid Inclusion Complex And Adsorption Properties Of Heavy Metals

This work has investigated the potential of cyclodextrin inclusion complex with magnetic responsivity to apply to the heavy metal removal from waste water,on the basis of previous theoretical study of cyclodextrin inclusion complex with organic phosphoric acid,this paper has discussed the practicable value of the material and looked forward to provide some theory reference toward heavy metal removal.At first,magnetic Fe3O4 nanoparticle was prepared via hydrothermal method,then Stober method was utilized to cover the nanoparticle with a silica shell for better dispersion and stability.Afterwards,the modified nanoparticle was surface amino functionalized by APTES,which was followed by the conjugation with 6-TsO-?-CD.The magnetic cyclodextrin complex with organic phosphoric acid was obtained by the inclusion process between Fe3O4@SiO2@APTES-CD and PBTCA.XRD,TGA,FTIR,SEM and TEM were used to characterize the structure and morphology.The adsorption capacities of MNP-CD-PBTCA for Hg(II)and Pb(II)were studied under different factors.For Hg(II),factors included pH,adsorbate concentration,temperature and time,the optimum condition for Hg(II)from aqueous solution is pH 4,70.00 mg·L-1 of Hg(?)concentration,55 ?,150 min of contact time with maximum adsorption capacity of 77.59 mg g-1;for Pb(II),factors included pH,adsorbent concentration,temperature and time,the optimum condition for Pb(II)from aqueous solution is pH 6,8.00 mg of MNP-CD-PBTCA,35 ?,10 min of contact time with maximum adsorption capacity of 52.25 mg·g-1.The kinetic study showed that both the two adsorption process of Hg(II)and Pb(II)well fitted Pseudo-second-order model,indicated that chemisorption dominated the two processes.In the adsorption process,Hg(II)formed two coordination compound while Pb(II)formed hexa-coordination compound with PBTCA.The intramolecular kinetic studies indicated that both two adsorption process included two stages,in first stage,heavy metal ions quickly adsorbed onto the surface of adsorbent under the driving force from high concentration gradient,with adsorption proceeded,the adsorption speed had slowed accordingly and finally attained equilibrium state,simultaneously,the phenomenon that adsorption speed of Hg(II)was slower than Pb(II)was probably due to the different coordination number of two heavy metal ions.In the investigation of thermodynamics,the adsorption process of Hg(?)fitted Langmuir model better while Pb(II)fitted Freundlich model better.All the thermodynamic parameters indicated that both adsorption processes of two heavy metals belonged to endothermic reaction,higher temperature was in favor of adsorption due to the positive value of ?H0;the increase of ?S0 indicated that the desorption of water molecules had increased the degree of disorder on adsorbent surface;the negative value of ?G0 indicated that the adsorption processes was a spontaneous process.This work has also investigated the regeneration ability of MNP-CD-PBTCA,results indicated that the adsorption efficiency still kept in 83.16%and 88.42%for Hg(?)and Pb(?),respectively;the desorption efficiency kept in 68.35%and 82.47%,respectively,which indicated that the adsorbent possessed excellent recycling value and had a better performance for Pb(?).