@article { ISI:000257637000008, title = {Adsorption of fluoride ions by Zn-Al layered double hydroxides}, journal = {Applied Clay Science}, volume = {40}, number = {1-4}, year = {2008}, month = {JUN}, pages = {54-62}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Zn-Al layered double hydroxides (LDHs) with different molar ratios Zn/Al (0, 0.17, 0.34, 0.97, 3.47, proportional to) were prepared by the co-precipitation of chlorides, characterized and evaluated for their fluoride adsorption at room temperature from aqueous solutions. The fluoride adsorption of the as-synthesized LDHs was influenced by the chemical composition of the LDHs and ZA-11 (Zn/Al = 0.97) had the highest capacity for fluoride adsorption (1.14-4.16 mg/g). The adsorption increased after calcination of the LDH up to 500 degrees C. The equilibrium data were fitted to the Freundlich, Langmuir, and Temkin equations. The kinetics of fluoride adsorption followed the pseudo-second order model. (C) 2007 Elsevier B.V All rights reserved.

}, keywords = {Adsorption, Anionic clay, Fluoride, Layered double hydroxide}, issn = {0169-1317}, doi = {10.1016/j.clay.2007.07.004}, author = {Mandal, Sujata and Mayadevi, S.} } @article { ISI:000257474100021, title = {Cellulose supported layered double hydroxides for the adsorption of fluoride from aqueous solution}, journal = {Chemosphere}, volume = {72}, number = {6}, year = {2008}, month = {JUN}, pages = {995-998}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Cellulose supported layered double hydroxides (CSLDHs) were synthesized and tested for adsorption of fluoride in aqueous medium. Three samples of cellulose supported LDHs were synthesized by varying the LDH loading on cellulose. The raw cellulose, unsupported LDH and cellulose supported LDHs were characterized by XRD, SEM and BET surface area. Batch adsorption as well as fixed-bed column experiments were performed for determining the fluoride adsorption characteristics of CSLDHs. The fluoride adsorption properties of CSLDHs were found to be superior to that of reported adsorbents, including activated alumina and carbon nanotubes. Defluoridation capacity of the CSLDHs was 2-4 times higher than that of unsupported LDH. The cellulose supported LDH, CSLDH-50, having an LDH loading of 27\% showed maximum fluoride uptake capacity (5.29 mg g(-1) of CSLDH, 25.18 mg g(-1) of LDH) in fixed-bed column study. (C) 2008 Elsevier Ltd. All rights reserved.

}, keywords = {Adsorption, cellulose, Fluoride, Layered double hydroxide}, issn = {0045-6535}, doi = {10.1016/j.chemosphere.2008.03.053}, author = {Mandal, Sujata and Mayadevi, S.} } @article { ISI:000268053200010, title = {Isothermal crystallization and melting behavior of polypropylene/layered double hydroxide nanocomposites}, journal = {Thermochimica Acta}, volume = {491}, number = {1-2}, year = {2009}, month = {JUL}, pages = {63-70}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The effect of layered double hydroxide (LDH) nanolayers on the crystallization behavior of polypropylene (PP) was studied based on the preparation of nanocomposites by a melt intercalation method. The isothermal crystallization kinetics and subsequent melting behavior of PP/LDH hybrids were studied with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). Studies revealed that the LDH promoted heterogeneous nucleation, accelerating the crystallization of PR The Avrami equation successfully describes the isothermal crystallization kinetics of PP/LDH hybrids and signifies heterogeneous nucleation in crystal growth of PR The varying values of Avrami exponent (n) and half crystallization time (t(1/2)) of PP and PP/LDH hybrids describes overall crystallization behavior. The crystallite size (D(hkl)) and distribution of different crystallites in PP varied in presence of LDH. A significant increase in melting temperature is observed for PP/LDH hybrids. The POM showed that smaller and less perfect crystals were formed in nanocomposites because of molecular interaction between PP chains and LDH. The value of fold surface free energy (sigma(e)) of PP chains decreased with increasing LDH content. Finally, the overall results signify that LDH at nanometer level acted as nucleating agent and accelerate the overall crystallization process of PR (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Isothermal crystallization, Layered double hydroxide, Melting behavior, Polypropylene nanocomposites}, issn = {0040-6031}, doi = {10.1016/j.tca.2009.03.002}, author = {Lonkar, Sunil P. and Singh, R. P.} } @article { ISI:000264434000020, title = {Preparation and nonisothermal crystallization behavior of polypropylene/layered double hydroxide nanocomposites}, journal = {Polymer}, volume = {50}, number = {6}, year = {2009}, month = {MAR}, pages = {1505-1515}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Polypropylene (PP)/layered double hydroxide (LDH) nanocomposites were prepared via melt intercalation using dodecyl sulfate anion modified LDH and maleated PP as compatibilizing agent. Evidently the interlayer anions in LDH galleries react with maleic anhydride groups of PP-g-MA and lead to a finer dispersion of individual LDH layers in the PP matrix. The nanostructure was characterized by XRD and TEM; the examinations confirmed the nanocomposite formation with exfoliated/intercalated layered double hydroxides well distributed in the PP matrix. The nonisothermal crystallization behavior of resulting nanocomposites was extensively studied using differential scanning calorimetry (DSC) technique at various cooling rates. In nonisothermal crystallization kinetics, the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the Avrami analysis and Jeziorny method well define the crystallization behavior of PP/LDH nanocomposite. Combined Avrami and Ozawa analysis (Liu model) also found useful. The results revealed that very small amounts of LDH (1\%) could accelerate the crystallization process relative to the pure PP and increase in the crystallization rates was attributed to the nucleating effect of the nanoparticles. Polarized optical microscopy (POM) observations also support the DSC results. The effective crystallization activation energy was estimated as a function of the relative degree of crystallinity using the isoconversional analysis. Overall, results indicated that the LDH particles in nanometer size might act as nucleating agent and distinctly change the type of nucleation, growth and geometry of PP crystals. (C) 2009 Elsevier Ltd. All rights reserved.

}, keywords = {Layered double hydroxide, Nonisothermal crystallization kinetics, Polypropylene nanocomposites}, issn = {0032-3861}, doi = {10.1016/j.polymer.2009.01.031}, author = {Lonkar, Sunil P. and Morlat-Therias, Sandrine and Caperaa, N. and Leroux, Fabrice and Gardette, Jean Luc and Singh, R. P.} } @article {46052, title = {[MoS4](2-)-Intercalated NiCo-layered double hydroxide nanospikes: an efficiently synergized material for urine to direct H-2 generation}, journal = {ACS Applied Materials \& Interfaces}, volume = {11}, year = {2019}, month = {JUL }, pages = {25917-25927}, type = {Article}, abstract = {

Substituting the energy-uphill water oxidation half-cell with readily oxidizable urea-rich urine, a ground-breaking bridge is constructed, combining the energy-efficient hydrogen generation and environmental 6 protection. Hence, designing a robust multifunctional electrocatalyst is desirable for widespread implementation of this waste to fuel technology. In this context, here, we report a simple tuning of the electrocatalytically favorable characteristics of NiCo-layered double hydroxide by introducing [MoS4]2- in its interlayer space. The [MoS4]{\textquoteright} insertion as well as its effect on the electronic structure tuning is thoroughly studied via X-ray photoelectron spectroscopy in combination with electrochemical analysis. This insertion induces overall electronic structure tuning of the hydroxide layer in such a way that the designed catalyst exhibited favorable kinetics toward all the required reactions of hydrogen generation. This is why our homemade catalyst, when utilized both as a cathode and anode to fabricate a urea electrolyzer, required a mere X1.37 V cell potential to generate sufficient H2 by reaching the benchmark 10 mA cm-2 in 1 M KOH/0.33 M urea along with long-lasting catalytic efficiency. Other indispensable reason of selecting [MoS4]2- is its high-valent nature making the catalyst highly selective and insensitive to common catalyst-poisoning toxins of urine. This is experimentally supported by performing the real urine electrolysis, where the nanospike-covered Ni foam-based catalyst showed a performance similar to that of synthetic urea, offering its industrial value. Other intuition of selecting [MoS4]2- was to provide a ligand-based mechanism for hydrogen evolution half-cell [hydrogen evolution reaction (HER)] to preclude the HER-competing oxygen reduction. Another crucial point of our work is its potential to avoid the mixing of two explosive product gases, that is, H2 and O-2.

}, keywords = {hydrogen evolution reaction, Layered double hydroxide, nickel oxyhydroxide, sewage denitrification, urea oxidation reaction, urine/urea electrolysis}, issn = {1944-8244}, doi = {10.1021/acsami.9b06545}, author = {Nadeema, Ayasha and Kashyap, Varchaswal and Gururaj, Rakshitha and Kurungot, Sreekumar} } @article {49063, title = {Synthetic layered double hydroxide on biodegradable support: an efficient adsorbent for defluoridation of water}, journal = {Indian Journal of Chemical Technology }, volume = {31}, year = {2024}, month = {JAN}, pages = {152-161}, type = {Article}, abstract = {

Fluoride concentrations in drinking water above permissible levels and incidences of fluorosis among people have been reported from many parts of the world including India. Low-cost and biodegradable adsorbents are the preferred choice for the removal of fluoride from an aqueous medium. In the present study, zinc-aluminium layered double hydroxide (LDH) supported on sugarcane bagasse (raw and acid-treated) has been synthesized, characterized, and investigated for the defluoridation of water. The SEM micrographs of the supported adsorbents show good dispersion of the LDH particles on the support material. The defluoridation capacity of the LDH is enhanced by supporting it on bagasse. The adsorption capacity of supported adsorbents increased by 3-fold than the unsupported LDH adsorbent. The adsorption data have been well fitted to the Freundlich isotherm model indicating physical and multi-layer adsorption. The maximum fluoride adsorption capacity has been found to be 8.85 mg/g with 76.3\% fluoride removal when the initial fluoride concentration is 11-12 mg/L. The pseudo-second-order kinetic model has been found suitable to explain the fluoride adsorption kinetics on the supported LDH adsorbents. The present study reveals that the bagasse-supported LDH adsorbent has a high potential for defluoridation of water.

}, keywords = {adsorption kinetics, Fluoride adsorption, Layered double hydroxide, Sugarcane bagasse}, issn = {0971-457X}, doi = {10.56042/ijct.v31i1.7611}, author = {Mayadevi, S. and Kirandas, M. D. and Manilal, A. M. and Roshini, N. and Mandal, Sujata} } @article {49710, title = {Enhanced electrocatalytic performances of NiCr layered double hydroxides by oxalate intercalation in anion exchange membrane water electrolysis}, journal = {ACS Applied Materials \& Interfaces}, volume = {17}, year = {2025}, month = {JUN}, pages = {37863-37878}, type = {Article}, abstract = {

Layered double hydroxides (LDHs) have attracted much attention these days in the field of water electrolysis due to easy modulation in their layered structure and properties. Herein, NiCr-LDH has been developed, and its interlayer spacing has been considerably increased by oxalate intercalation. Such increased interlayer spacing allows easy access of hydroxides to a large number of electroactive sites and thereby boosts the electrocatalytic performances both for oxygen and hydrogen evolution reactions. Being very active toward both the electrocatalytic reactions, the oxalate-intercalated NiCr-LDH was further explored in an alkaline anion exchange membrane water electrolyzer (AEMWE), achieving 800 mA cm-2 at 1.88 V cell voltage at an operating temperature of 60 degrees C. In fact, the electrolyzer efficiency has been determined to be as high as 69.66\%, and the calculated H2 production cost was found to be \$0.97 per gasoline-gallon equivalent, which is well below the targeted cost by the Department of Energy, USA. The electrocatalyst was also examined in harsh alkaline media, like highly saline or seawater, which also indicated its ability to carry out sustainable seawater electrolysis, restricting chlorides to a great extent. Interestingly, post-electrolysis characterization reveals the fact that oxalate decomposition aided carbonate formation within interlayers of NiCr-LDH, and high affinity toward hydroxides is responsible for restricting chlorides during the electrolysis process, apart from the great electrocatalytic activity.

}, keywords = {Anion exchange, hydrogen production, interlayerspacing, Layered double hydroxide, Sustainable, water electrolyzer}, issn = {1944-8244}, doi = {10.1021/acsami.5c04189}, author = {Pal, Santanu and Sinha, Nibedita and Das, Chandni and Chauhan, Inderjeet and Ahmed, Tanbir and Roy, Poulomi} }