Removal of Phosphate from Eutrophic Lakes through Adsorption by in Situ Formation of Magnesium Hydroxide from Diatomite

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• 作者：Fazhi Xie ; Fengchang Wu ; Guijian Liu ; Yunsong Mu ; Chenglian Feng ; Huanhua Wang ; John P. Giesy
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：January 7, 2014
• 年：2014
• 卷：48
• 期：1
• 页码：582-590
• 全文大小：538K
• ISSN：1520-5851

文摘

Since in situ formation of Mg(OH)₂ can efficiently sorb phosphate (PO₄) from low concentrations in the environment, a novel dispersed magnesium oxide nanoflake-modified diatomite adsorbent (MOD) was developed for use in restoration of eutrophic lakes by removal of excess PO₄. Various adsorption conditions, such as pH, temperature and contact time were investigated. Overall, sorption capacities increased with increasing temperature and contact time, and decreased with increasing pH. Adsorption of PO₄ was well described by both the Langmuir isotherm and pseudo second-order models. Theoretical maximum sorption capacity of MOD for PO₄ was 44.44鈥?2.08 mg/g at experimental conditions. Characterization of PO₄ adsorbed to MOD by use of X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and solid state ³¹P nuclear magnetic resonance revealed that electrostatic attraction, surface complexation and chemical conversion in situ were the major forces in adsorption of PO₄. Mg(OH)₂ formed in situ had a net positive charge on the surface of the MOD that could adsorb PO₄^3- and HPO₄^2- anion to form surface complex and gradually convert to Mg₃(PO₄)₂ and MgHPO₄. Efficiency of removal of PO₄ was 90% when 300 mg MOD/L was added to eutrophic lake water. Results presented here demonstrated the potential use of the MOD for restoration of eutrophic lakes by removal of excess PO₄.