High efficient removal of fluoride from aqueous solution by a novel hydroxyl aluminum oxalate adsorbent

A novel adsorbent, hydroxyl aluminum oxalate (HAO), for the high efficient removal of fluoride from aqueous solution was successfully synthesized. The adsorbent was characterized and its performance in fluoride (F−) removal was evaluated for the first time. Kinetic data reveal that the F− adsorption is rapid in the beginning followed by a slower adsorption process; 75.9% adsorption can be achieved within 1 min and only 16% additional removal occurred in the following 239 min. The F− adsorption kinetics was well described by the pseudo second-order kinetic model. The calculated adsorption capacity of this adsorbent for F− by Langmuir model was 400 mg g−1 at pH 6.5, which is one of the highest capabilities of today’s materials. The thermodynamic parameters calculated from the temperature-dependent isotherms indicate that the adsorption reaction of F− on the HAO is a spontaneous process. The FT-IR spectra of HAO before and after adsorbing F− show adsorption mechanism should be hydroxyl and oxalate interchange with F−.

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