scholarly journals Water defluoridation by carbonate calcined and uncalcined Layered Double Hydroxides (LDHs)

2019 ◽  
Vol 98 ◽  
pp. 09005
Author(s):  
Elisabetta Dore ◽  
Franco Frau
Keyword(s):  
Anion Exchange ◽  
Sorption Capacity ◽  
Layered Double Hydroxides ◽  
Lamellar Structure ◽  
Ph Value ◽  
Molar Ratio ◽  
Fluoride Removal ◽  
Cationic Composition ◽  
Removal Capacity ◽  
Double Hydroxides

Carbonate Layered Double Hydroxides (LDHs) with different cationic composition and M2+/M3+ molar ratio were tested, both untreated and calcined, for water defluoridation. The defluoridation capacity of calcined LDHs, produced by intercalation during the reconstruction of lamellar structure, is more effective than the anion exchange of untreated LDHs. Among the calcined LDHs tested, that with 3Mg/(0.5Al+0.5Fe) molar ratio yields a maximum fluoride sorption capacity up to 92.3 mg/g, in spite of the high pH value (up to 12) of the experiments. After four cycles of regeneration by calcination and subsequent water defluoridation, this LDH composition maintains more than 80% of its fluoride removal capacity.

Effect of Doped Iron on Fluoride Sorption by Calcined MgAlFe-CO3 Layered Double Hydroxides

2013 ◽  
Vol 681 ◽  
pp. 21-25
Author(s):  
Yu Bing Pu ◽  
Jia Rui Wang ◽  
Hong Zheng ◽  
Peng Cai ◽  
Si Yuan Wu
Keyword(s):  
Layered Double Hydroxides ◽  
Synthetic Wastewater ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Fluoride Removal ◽  
Maximum Sorption Capacity ◽  
Fluoride Adsorption ◽  
Maximum Sorption ◽  
Co Precipitation ◽  
Double Hydroxides

A series of MgAlFe-CO3 layered double hydroxides (LDHs) were successfully prepared by co-precipitation method. With synthetic wastewater, the effect of doped iron on fluoride sorption by calcined MgAlFe-CO3 layered double hydroxides (CLDH) under different pH and contact time conditions was investigated. The sorption isotherm data were fitted well to Langmuir isotherm at 25 °C. The maximum sorption capacity of fluoride on CLDH increases first and then decreases with the increase of Fe/Al molar ratio and attains maximum of 71.94 mg/g when Fe/Al molar ratio is 1:2, although doped iron is unfavorable to the regeneration of original layered structure for CLDH after fluoride adsorption. No aluminium in the solution after fluoride adsorption was detected when Fe/Al molar ratio is equal to or larger than 1:2. The results indicate that CLDH with proper Fe/Al molar ratio is a promising candidate as an adsorbent material for fluoride removal from aqueous solutions.

scholarly journals Lysine-Functionalized Layered Double Hydroxides For The Antibiotics’ Efficient Removal: Controllable Fabrication Via BBD Model And Removing Mechanism

2021 ◽  
Author(s):  
Yuying Hu ◽  
Susu Liu ◽  
Min Qiu ◽  
Xiaohuan Zheng ◽  
Xiaoming Peng ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Adsorption Mechanism ◽  
Electrostatic Attraction ◽  
Adsorption Behavior ◽  
Molar Ratio ◽  
Order Kinetic ◽  
Efficient Removal ◽  
Adsorption Processes ◽  
Controllable Fabrication ◽  
Double Hydroxides

Abstract Ly @ FeZn layered double hydroxides (LDHs) controllable fabrication based on Box-Behnken Design (BBD) model was fabricated, and presented stable and efficient removal performance for Ciprofloxacin (CIP), Norfloxacin (NOR) and Ofloxacin (OFL) removal. It should be noted that Ly @ FeZn had different adsorption behavior towards CIP, NOR and OFL. Furthermore, the Ly @ FeZn was characterized by SEM, XRD, FT-IR and XPS. Results revealed the optimized fabrication condition (temperature of 60 °C, Fe / Zn molar ratio of 0.5 and the lysine dosage of 5.8 mmol) for the removing efficient. The highest adsorption capacity of CIP, NOR and OFL were 193.83, 190.20 and 62.12 mg/g, respectively. Adsorption kinetics of both CIP and NOR were well simulated with the pseudo-first-order kinetic model, while that of OFL was well-described by the pseudo-second-order. Moreover, the adsorption thermodynamics of CIP and NOR on Ly @ FeZn indicated that the adsorption processes were exothermal, feasible and spontaneous. It was worth noting that the adsorption mechanism of Ly @ FeZn for CIP and NOR were the synergistic reaction of electrostatic attraction, chemical bonding and flocculation. On the other side, the adsorption behavior of OFL was relatively low, and the adsorption mechanism was only electrostatic attraction.

Anion-exchange reactions of layered double hydroxides

1990 ◽  
Vol 29 (26) ◽  
pp. 5201-5207 ◽  
Author(s):  
Martina Meyn ◽  
Klaus Beneke ◽  
Gerhard Lagaly
Keyword(s):  
Anion Exchange ◽  
Layered Double Hydroxides ◽  
Exchange Reactions ◽  
Double Hydroxides

scholarly journals Potential Sustainable Slow-Release Fertilizers Obtained by Mechanochemical Activation of MgAl and MgFe Layered Double Hydroxides and K2HPO4

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 183 ◽  
Author(s):  
Roger Borges ◽  
Fernando Wypych ◽  
Elodie Petit ◽  
Claude Forano ◽  
Vanessa Prevot
Keyword(s):  
Layered Double Hydroxides ◽  
Slow Release ◽  
Mechanochemical Activation ◽  
Molar Ratio ◽  
X Ray ◽  
Dipotassium Hydrogen Phosphate ◽  
Before And After ◽  
Noticeable Improvement ◽  
Slow Release Fertilizers ◽  
Double Hydroxides

This study describes the behavior of potential slow-release fertilizers (SRF), prepared by the mechanochemical activation of calcined Mg2Al-CO3 or Mg2Fe-CO3 layered double hydroxides (LDH) mixed with dipotassium hydrogen phosphate (K2HPO4). The effects of LDH thermal treatment on P/K release behavior were investigated. Characterizations of the inorganic composites before and after release experiments combined X-Ray diffraction (XRD), Fourier-transform infra-red spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The best release profile (<75% in 28 days and at least 75% release) was obtained for MgAl/K2HPO4 (9 h milling, 2:1 molar ratio, MR). Compared to readily used K2HPO4, milling orthophosphate into LDH matrices decreases its solubility and slows down its release, with 60% and 5.4% release after 168 h for MgAl/K2HPO4 and MgFe/K2HPO4 composites, respectively. Mechanochemical addition of carboxymethylcellulose to the LDH/K2HPO4 composites leads to a noticeable improvement of P release properties.

scholarly journals Liquid phase exfoliation of carbonate-intercalated layered double hydroxides

2019 ◽  
Vol 55 (23) ◽  
pp. 3315-3318 ◽  
Author(s):  
Jose A. Carrasco ◽  
Andrew Harvey ◽  
Damien Hanlon ◽  
Vicent Lloret ◽  
Dave McAteer ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Anion Exchange ◽  
Layered Double Hydroxides ◽  
Exchange Reactions ◽  
Liquid Phase Exfoliation ◽  
Double Hydroxides

Direct exfoliation of carbonate layered double hydroxides has been achieved by using a novel horn-probe sonic tip, avoiding the development of time-consuming anion-exchange reactions.

Synthesis and Anion Exchange Chemistry of Rhombohedral Li/Al Layered Double Hydroxides

2002 ◽  
Vol 14 (1) ◽  
pp. 232-234 ◽  
Author(s):  
Andrew M. Fogg ◽  
Amal J. Freij ◽  
Gordon M. Parkinson
Keyword(s):  
Anion Exchange ◽  
Layered Double Hydroxides ◽  
Double Hydroxides

scholarly journals Curcumin Incorporation into Zn3Al Layered Double Hydroxides—Preparation, Characterization and Curcumin Release

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 244 ◽  
Author(s):  
Octavian D. Pavel ◽  
Ariana Şerban ◽  
Rodica Zăvoianu ◽  
Elena Bacalum ◽  
Ruxandra Bîrjega
Keyword(s):  
Layered Double Hydroxides ◽  
Curcuma Longa ◽  
Nano Particles ◽  
Molar Ratio ◽  
Attenuated Total Reflectance ◽  
Buffer Solutions ◽  
Ph Values ◽  
Main Crystalline Phase ◽  
Ph Increase ◽  
Double Hydroxides

Curcumin (CR) is a natural antioxidant compound extracted from Curcuma longa (turmeric). Until now, researches related to the incorporation of CR into layered double hydroxides (LDHs) were focused only on hybrid structures based on a MgxAl-LDH matrix. Our studies were extended towards the incorporation of CR in another type of LDH-matrix (Zn3Al-LDH) which could have an even more prolific effect on the antioxidant activity due to the presence of Zn. Four CR-modified Zn3Al-LDH solids were synthesized, e.g., PZn3Al-CR(Aq), PZn3Al-CR(Et), RZn3Al-CR(Aq) and RZn3Al-CR(Et) (molar ratio CR/Al = 1/10, where P and R stand for the preparation method (P = precipitation, R = reconstruction), while (Aq) and (Et) indicate the type of CR solution, aqueous or ethanolic, respectively). The samples were characterized by XRD, Attenuated Total Reflectance Fourier Transformed IR (ATR-FTIR) and diffuse reflectance (DR)-UV–Vis techniques and the CR-release was investigated in buffer solutions at different pH values (1, 2, 5, 7 and 8). XRD results indicated a layered structure for PZn3Al-CR(Aq), PZn3Al-CR(Et), RZn3Al-CR(Aq) impurified with ZnO, while RZn3Al-CR(Et) contained ZnO nano-particles as the main crystalline phase. For all samples, CR-release revealed a decreasing tendency towards the pH increase, and higher values were obtained for RZn3Al-CR(Et) and PZn3Al-CR(Et) (e.g., 45% and 25%, respectively at pH 1).

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