Preparation And Adsorption Properties Of The Chitosan-based Lead Removal Chelate Adsorbent

Two Chitosan-based lead removal chelate adsorbent were prepared by imprinting Leadions before and after modifieding magnetic crosslinking chitosan. Adsorption capacity ofLead ions adsorption onto adsorbent were studied, and the characterization were researchedby the scanning electron microscope（SEM）, Fourier transform infrared spectrometer（FT-IR）and X-ray diffraction（XRD）, respectivity. Batch adsorption experiments were performed toevaluate the adsorption mechanism, influencing factor and adsorption conditions.The resultsshowed that:（1） Firstly, preparation Pb-CS, then nano Fe3O4particles were prepared by theco-precipitation, glutaraldehyde（50%M/M） as crosslinking agent, Pb-MCS was prepared, lastthiourea as modifier, Pb-TMCS was prepared. And，Nano Fe3O4particles were prepared bythe co-precipitation, glutaraldehyde（50%M/M） as crosslinking agent, thiourea as modifier,firstly, preparation MCS, then preparation TMCS, last TMCS-Pb was prepared.（2） The morphology and characterization of Pb-TMCS, TMCS-Pb and CS were observedby SEM, the results showed that: the surface of CS were smooth and neat; but Pb-TMCSpolymers have more folds and pore.The Pb-TMCS polymers have large more area than theTMCS-Pb, indicating that large number of effective imprinting sites could be exited in thesurface to rebind the template molecules in aqueous media; Infrared spectra of Pb-TMCS wasshown that it have more-NH2and-OH than TMCS-Pb, and a characteristic adsorption peakof the Fe-O appeared in the500cm-1。 The XRD results of the magnetic particles and pureFe3O4particles were mostly coincident.Six characteristic peaks for Fe3O4（2θ=30.4°、35.6°、43.5°、53.4°、57.4°、62.7°）, were observed in Pb-TMCS and TMCS-Pb.（3） Batch adsorption experiments were performed to evaluate the best adsorptionconditions. The results showed that the maximum adsorption capacity were45.26mg/g,36.45mg/g,25.57mg/g, respectively, observed at pH5and temperature at25℃. Equilibriumadsorption was achieved within240min,240min, and120min respectively. The kinetic data could be fitted with a pseudo-second order equation, Adsorption rate constant were1.67×10^-3,0.86×10^-3, and1.22×10^-3g·mg^-1min^-1, respectively. Adsorption process could be welldescribed by Langmuir adsorption isotherms.The thermodynamic parameters of Pb-TMCS,TMCS-Pb and CS such as△H were-63.72,-22.95and-33.17kJ·mol^-1, respectively;△S were-191.48,-62.74and-94.64J·mol^-1, respectively;△G were calculated in the differenttemperature25℃,35℃and45℃, The thermodynamic parameters of Pb-TMCS were-6.659,-4.744and-2.830kJ·mol^-1,respectively; TMCS-Pb were-4.255,-3.627and-3.000kJ·mol^-1;and CS were-4.489,-3.543,-2.596kJ·mol^-1.（4）The saturation adsorption of Pb-TMCS, TMCS-Pb and CS were desorpted by0.1mol/LHCl, at45°C, desorption rate of adsorbent were90%,83%and70%, respectively.