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As a new highly active adsorbent,the adsorption performance of lanthanum alginate bead has been reported.The adsorption mechanism was discussed in this study,including isotherm model fitting,XRD,FTIR spectra,SEM,EDX and Ion chromatography.The adsorption isotherm of lanthanum alginate bead fits Langmuir model well and the maximum adsorption capacity is 197.2 mg/g,which indicates the adsorbents surface is homogeneous.The lanthanum alginate bead has good hydroscopicity and the swelling rate is more than 200%.Good hydroscopicity and homogeneous surface showed the adsorbent primary condition for high activity.The XRD pattern revealed that lanthanum alginate bead changed the original crystal structure of sodium alginate and showed the amorphous nature which allows a better accessibility to fluoride and thus a better activity [1]; furthermore,La itself has a very strong affmity with F,which is another reason for the high adsorption capacity of lanthanum alginate bead.The FTIR spectra showed no obvious change at 1416 cm-1,corresponding to-COO groups,which confirmed the good skeleton structure of lanthanum alginate bead.The SEMs showed the adsorbent surface morphology before and after adsorption,the tight structure of adsorption surface was broken after adsorption.Good skeleton structure and broken surface morphology provided the conditions for solid-liquid mass transfer.Based on experiments and literatures,the adsorption mechanism was considered to be ion exchange between F and Cl or OH.It was verified form both the adsorbent and the adsorption water.EDX data showed Cl on the adsorbent surface before adsorption and there was no Cl while F occurred on the adsorbent surface after adsorption,which indicated the ion exchange between Cl and F.The water before and after adsorption were also tested by Ion chromatography owing to the limited test depth of EDX,C1 appeared in the water after adsorption while the concentration is 6.15 mg/L,which still supports the exchange between Cl and F.Meanwhile,pH of the water in the adsorption process was tested by pH meter,pH rise with the proceed of adsorption,meaning OH is increasing gradually with the reduction of F,indicated the exchange between OH and F,which was confirmed in literature [2].