Efficient removal of fluoride from drinking water using well-dispersed monetite bundles inlaid in chitosan beads

• The well-dispersed monetite bundles inlaid in chitosan beads were prepared.
• Chitosan-Ca(II) complex was used as the calcium precursor in preparation.
• It shows a relative high adsorption capacity of 50.01 mg/g for F− removal.
• It can efficiently remove fluoride in a wide pH range from 3 to 12.

Calcium-based mineral has been widely applied for fluoride adsorption to avoid potential health risks of metal leaching, but the relatively lower adsorption capacity is the major drawback of these adsorbents. Thus, in this study, the well-dispersed monetite bundles inlaid in chitosan beads (MONs@CS) were explored by using chitosan-Ca(II) complex as the calcium precursor, and the applicability of this novel adsorbent was evaluated. The sorption of fluoride ions to MONs@CS agreed well to the Langmuir adsorption model with a high maximum adsorption capacity of 50.01 mg/g, which was higher than most of the reported calcium-based adsorbents. This adsorbent could maintain high defluorination efficiency in a wide pH range from 3 to 12. The common coexisting anions almost had no negative effect on the F− adsorption and its high defluorination efficiency of real water samples suggest that this adsorbent is suitable for fluoride removal from drinking water. Further, the possible mechanism for fluoride removal by MONs@CS was proposed, which the ion exchange played a leading role in defluorination and the pre-protonated amine groups of chitosan matrix could be assisted to adsorb F− through the electrostatic interactions under acidic condition and could provide buffering capacity for MONs@CS beads under alkaline conditions.

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