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Enhanced fluoride removal by La-doped Li/Al layered double hydroxides
Jianguo Cai1, Xin Zhao2, Yanyang Zhang1
1State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China; Research Center for Environmental Nanotechnology (ReCENT), Nanjing University, Nanjing 210023, China.
Journal of Colloid and Interface Science
|September 18, 2017
Summary
Lanthanum-doped lithium/aluminum layered double hydroxide (LDH) effectively removes fluoride from water. This La-doped LDH shows superior fluoride adsorption capacity and can be regenerated for reuse.
Area of Science:
- Materials Science
- Environmental Science
- Chemistry
Background:
- Fluoride contamination in drinking water poses significant health risks.
- Conventional water treatment methods for fluoride removal can be inefficient or costly.
- Layered double hydroxides (LDHs) show promise as adsorbents for water remediation.
Purpose of the Study:
- To develop and evaluate lanthanum (La) intercalated lithium/aluminum layered double hydroxide (Li/Al-LDH) for efficient water defluoridation.
- To compare the fluoride adsorption performance of La-doped Li/Al-LDH with unmodified Li/Al-LDH and activated alumina.
- To elucidate the adsorption mechanism and assess the reusability of the developed adsorbent.
Main Methods:
- Synthesis of La intercalated Li/Al-LDH.
- Batch adsorption experiments to test fluoride removal efficiency across a pH range of 5-9.
- Kinetic and isotherm studies using pseudo-second order and Freundlich models, respectively.
- Analysis of competing ion effects.
- Characterization using X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transform Infrared Spectroscopy (FTIR).
- Regeneration studies using alkaline solutions.
Main Results:
- La-doped Li/Al-LDH demonstrated significantly higher fluoride adsorption capacity compared to Li/Al-LDH and activated alumina.
- Optimal fluoride adsorption was observed in the pH range of 5-9.
- Adsorption kinetics followed a pseudo-second order model, and adsorption equilibrium was described by the Freundlich model.
- XPS and FTIR analysis indicated the involvement of La and Al in fluoride adsorption, with chloride replacement by fluoride occurring.
- The adsorbent was successfully regenerated using an alkaline solution (pH 12) for cyclic adsorption runs.
Conclusions:
- La-doped Li/Al-LDH is a highly effective adsorbent for fluoride removal from water.
- The material exhibits excellent adsorption capacity, favorable kinetics, and good reusability.
- The study provides insights into the mechanism of fluoride adsorption by La-doped LDH, highlighting the role of La and Al.
- La-doped Li/Al-LDH presents a promising solution for efficient and sustainable water defluoridation.
