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Defluorination Techniques: Past, Present and Future Prospective
Khatkar Rahul,Nagpal Suman 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.3
Fluoride ions are commonly found in minerals like mica, fl uorapatite, muscovite, topaz, biotite, sellaite, cryolite, muscovite, and fl uorspar. However, the presence of fl uoride in groundwater has become a concern due to its contamination by wastewater from coal thermal power stations, aluminium smelters, electroplating-based industries, and glass and ceramic manufacturing facilities. While low fl uoride consumption has some health benefi ts, excessive intake can lead to serious health issues such as crippling skeletal fl uorosis, Alzheimer’s syndrome, carcinogenic eff ects, infertility, and thyroid disorders. To address these chronic health impacts, there has been signifi cant research to fi nd out sustainable and highly effi cient methods for fl uoride removal. This review paper overviews various defl uorination techniques, such as precipitation and coagulation, ion exchange, electrodialysis or reverse osmosis (RO), nano-fi ltration, adsorption, with their various advantages and drawbacks. The present review aims to provide insight knowledge of importance of fl uoride, its toxicity issues and their available removal strategies and their limitations. This will help the researchers in developing cost-eff ective, environmentally friendly, and convenient techniques for defl uorination in diff erent matrices. The paper encourages scientists to work towards achieving reliable and eco-friendly defl uorination methods for future application.
Sarita Khatkar,Arun Nanda,S. H. Ansari 한국생약학회 2017 Natural Product Sciences Vol.23 No.2
The optimization and microwave assisted extraction of stem bark of Terminalia arjuna, quantitative estimation of the marker compounds arjunic acid and arjunolic acid using HPTLC and the evaluation of free radical scavenging activity has been performed in this study. The central composite design was used for optimization and the values of parameters for optimized batch of microwave assisted extraction were 1000 W (Power), 3 minutes (Time) and 1/120 (Solid/solvent ratio). The solvent system to carry out the HPTLC was toluene: acetic acid: ethyl acetate (5: 5: 0.5) and quantitative estimation was done using standard equations obtained from the marker compounds. The in-vitro free radical scavenging activity was performed spectrophotometrically using ascorbic acid as standard. The value of estimated percentage yield of arjunic acid and arjunolic acid was 1.42% and 1.52% which upon experimentation was obtained as 1.38% and 1.51% respectively. The DPPH assay of the different batches of microwave assisted extraction and marker compounds taken suggested that the marker compounds arjunic acid and the arjunolic acid were responsible for the free radical scavenging activity as the batch having the maximum percentage yield of the marker compounds showed best free radical scavenging effect as compared to standard ascorbic acid. The IC50 value of the optimized batch was found to be 24.72 while that of the standard ascorbic acid was 29.83. Hence, the yield of arjunic acid and arjunolic acid has direct correlation with the free radical scavenging activity of stem bark extract of Terminalia arjuna and have potential to serve as active lead compounds for free radical scavenging activity.
Synthesis by Using the Combustion Method and Photoluminescence of SrZnO2 :Tb3+ Nanophosphors
Satyender Pal khatkar,Sang Do Han,Chi Hwan Han,Dinesh Kumar,Gaytri Sharma,Vinod Bala Taxak 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
SrZnO2:Tb3+ nanocrystals were synthesized by using a combustion route with metal nitrates as precursors and urea as a fuel in a furnace preheated to 500 C. The nanocrystals obtained through combustion synthesis were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The nanocrystals had sizes from 27 nm to 43 nm. The nanocrystals prepared under an UV source revealed green luminescence that was attributed to transitions from the 5D4 excited state to the 7FJ (J = 3 . 6) ground state of Tb3+ ions. The predominant green color from the magnetic dipole transition 5D4 ! 7F5 of Tb3+ was located at 545 nm. In addition, the dependence of the luminescence intensity on the Tb3+ concentrations and effect of heat treatment on the size of the nanocrystals are discussed. The intensity of the 5D4 emission increases with increasing sintering temperature while that of the 5D3 emission decreases.own
Synthesis and luminescent properties of CaIn2O4:xTb nanocrystals
S.P. Khatkar,Sang Do Han,V.B. Taxak,Gaytri Sharma Dinesh Kumar,Dinesh Kumar 한국물리학회 2006 Current Applied Physics Vol.6 No.1l
Terbium-activated CaIn2O4:xTb (x = 0.12%, 0.5%, 1.0% and 2%) nanocrystals have been produced by combustion synthesis usingglycine as a fuel in a preheated furnace at 500.C. The nanocrystals obtained were characterized by scanning electron microscopyand X-ray diraction (XRD) techniques. The prepared nanocrystals under a UV source revealed green luminescence that was attributedto the transition from5D4 excited state to7F5 ground state of Tb3+ ions. In addition, the dependence of the luminescence intensity onTb3+ concentration and eect of glycine to nitrate ratio on the particle size of the nanocrystals have also been discussed.
Characteristic white light emission via down-conversion SrGdAlO4:Dy3+ nanophosphor
Anju Hooda,S.P. Khatkar,Avni Khatkar,Sangeeta Chahar,Sushma Devi,Jyoti Dalal,V.B. Taxak 한국물리학회 2019 Current Applied Physics Vol.19 No.4
An efficient and cost-effective technique, solution combustion synthesis was used to synthesize Dy3+ doped SrGdAlO4 nanophosphor utilizing urea as a suitable fuel. The tetragonal phase and nano-crystallinity of the synthesized phosphor belonging to I4/mmm space group was confirmed by powder X-ray diffraction (PXRD) and transmission electron microscope (TEM) technique respectively. Various crystal structure parameters and refined atomic positions of host matrix and SrGd0.95Dy0.05AlO4 nanophosphor were determined by Rietveld refinement. The two intense bands i.e. blue and yellow bands were observed in photoluminescence emission spectrum recorded at 352 nm excitation wavelength, associated to transitions 4F9/2→6H15/2 (484 nm) and 4F9/2→6H13/2 (575 nm) respectively. Photometric characterizations revealed the emission of white color by the synthesized nanophosphor proving its wide applications in WLEDs (white light emitting diodes). Band gap values calculated using diffuse reflectance spectra (DRS) were found to vary in the range of 5.50 eV–5.59 eV for host and doped lattice system. Keeping in mind, the concentration quenching phenomenon, SrGd0.95Dy0.05AlO4 was considered as optimized nanophosphor for WLEDs.
Vinod Taxak,Satyender Pal khatkar,Sonika Singh,Sheetal Lohra,Avni Khatkar 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.3
A color tunable terbium doped GdSrAl3O7 nanophosphor has been synthesized at low temperature using solution combustion synthesis. The photoluminescent properties of nanophosphors have been explored by analyzing their excitation and emission spectra alongwith their decay curves. The emission spectra exhibit dominating green light at 544 nm due to 5D4→7F5 transition of Tb3+ ions in GdSrAl3O7 on excitation by UV light of 239 nm. Furthermore, the luminescence in Gd(1-x)SrAl3O7: xTb3+ nanophosphors shifted from blue to green color by properly tuning the concentration of terbium ions. Decay curves indicate that non-radiative cross-relaxation is primarily responsible for concentration quenching phenomenon in the GdSrAl3O7 host. X-ray diffraction (XRD) analysis confirmed that single tetragonal phased nanophosphor could be readily obtained at low temperature 550°C. The smooth surfaced nanocrystals with particle size of 45 - 50 nm have also been examined by transmission electron microscopy (TEM). All these features augmented the probability of GdSrAl3O7: Tb3+ nanophosphor for potential applications in optical devices.