Elevated concentrations of fluoride ions (F-) in natural groundwater are a worldwide problem. Discarded oyster shells were ground to ≤100 µm particle size to produce oyster shell powder (OS). A subset of the OS was heated to produce calcined oyster shell (COS). A subset of the COS was further treated with 1 M phosphoric acid to produce phosphoric-acid-treated oyster shell (POS). OS and COS were combined with phosphoric acid (1.6 mM and 3.2 mM) to produce OS + P (oyster shell with phosphoric acid) and COS + P (calcined oyster shell with phosphoric acid). OS and COS removed 46% and 50% (10 g/L of sorbent dose) but POS, OS + P and COS + P removed 96%, 100% and 76% (1 g/L of sorbent dose) when the initial concentration of fluoride was 10 mg/L. The sorption kinetics of POS, OS + P and COS + P followed second-order reaction rates, and sorption isotherms of all sorbents were well-described by the Freundlich sorption isotherm. These results indicate that oyster shells can be an effective sorbent for fluoride removal, with the added benefit of re-use of a waste product.

中文翻译：

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改性牡蛎壳，用于去除水中的氟化物。

天然地下水中氟离子（F-）的浓度升高是一个世界性的问题。将丢弃的牡蛎壳研磨至≤100µm粒度，以生产牡蛎壳粉（OS）。加热一部分OS，以生产煅烧的牡蛎壳（COS）。用1 M磷酸进一步处理一部分COS，以生产经磷酸处理的牡蛎壳（POS）。OS和COS与磷酸（1.6 mM和3.2 mM）结合产生OS + P（带磷酸的牡蛎壳）和COS + P（带磷酸的煅烧牡蛎壳）。初始浓度时，OS和COS去除了46％和50％（10 g / L的吸附剂剂量），但是POS，OS + P和COS + P去除了96％，100％和76％（1 g / L的吸附剂剂量）氟化物的含量为10 mg / L。POS，OS + P和COS + P的吸附动力学遵循二级反应速率，Freundlich吸附等温线很好地描述了所有吸附剂的吸附等温线。这些结果表明，牡蛎壳可以是去除氟化物的有效吸附剂，并具有废物再利用的额外好处。