RESEARCH ON PREPARATION AND FLUORIDE REMOVAL PERFORMANCE OF LANTHANUM-MAGNESIUM-LOADED ACTIVATED ALUMINA

Lanthanum-Magnesium-loaded activated alumina prepared through impregnation was used to remove fluoride from aqueous solution． By orthogonal experiment，the paper studied effect of absorbability with La3 + /Mg2 + molar ratio，calcination temperature and calcination time． The optimum conditions were as follows: The molar ratio of La3 + to Mg2 + was 1 ∶ 2，the calcination temperature was 300 ℃，the calcination time was 2. 0 h． The influence of contact time，absorbent dosage，pH， and coexisted negative ions on fluoride adsorption were performed． Results showed that the optimum effect was contact time of 3. 0 h，absorbent dosage of 3. 6 mg /L，pH of 6 ～ 9， and the removal rate was 94. 5%． The influence of different anions on the adsorption was: CO2 － 3 ＞ SO2 － 4 ＞ Cl － ＞ NO － 3 ． Kinetic data were well described by the pseudo-second-order kinetic model． The adsorption isotherm could be well fitted by the Langmuir equation． The max adsorption capacity was 7. 663 mg /g． The results demonstrated that the adsorption process was spontaneous and endothermic．