Layered Double Hydroxide and Its Calcined Product for Fluoride Removal from Groundwater of Ethiopian Rift Valley

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• 作者：Meseret Dessalegne ; Feleke Zewge ; Numa Pfenninger…
• 关键词：Layered double hydroxide ; Calcined layered double hydroxide ; Fluoride ; Adsorption ; Column system ; Groundwater
• 刊名：Water, Air, and Soil Pollution
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：227
• 期：10
• 全文大小：1,595 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Environment
  Environment
  Atmospheric Protection, Air Quality Control and Air Pollution
  Waste Water Technology, Water Pollution Control, Water Management and Aquatic Pollution
  Terrestrial Pollution
  Hydrogeology
  
• 出版者：Springer Netherlands
• ISSN：1573-2932
• 卷排序：227

文摘

In this study, batch experiments have been carried out to investigate the mechanism of fluoride uptake by layered double hydroxide (LDH) and calcined layered double hydroxide (CLDH). Furthermore, practical use of these synthetic minerals was studied in continuous mini-column experiments. In these column studies, groundwater from Ethiopia was tested. LDH and CLDH were synthesized with Mg/Al mole ratio of 2. From batch experimental study, LDH and CLDH have shown maximum removal capacity of 84 and 222 mg F−/g from aqueous solution, respectively. It was observed that fluoride removal was pH dependent with favorable pH range of 5–7 (max. at pH 6). The mechanism of removal is suggested to be ion exchange for LDH and a memory effect followed by surface precipitation reaction for CLDH. The presence of other anions lowered defluoridation capacity of LDH in the order of PO₄3− > SO₄2− > NO₃− ≈ Cl−. From continuous experiments at 1 mM NaHCO₃, LDH showed maximum defluoridation capacity of 1.3 mg/g and CLDH up to 20 mg/g. It was also observed that increase of bicarbonate concentration to 10 mM lowered the fluoride uptake capacity of CLDH to 4 mg/g. The presence of 1 mM H₄SiO₄ further reduced fluoride uptake capacity to 3 mg/g. CLDH column tested with groundwater from the Rift Valley with 10.5 mg F−/L has shown maximum removal capacity of 2.2 mg F−/g. Regeneration of this column indicated that CLDH has a good potential to be re-used.