http://localhost:8080/xmlui/handle/123456789/7468 2026-04-30T10:54:36Z http://localhost:8080/xmlui/handle/123456789/8154 Synthesis of hydroxyapatite nanorods for application in water defluoridation and optimization of process variables: Advantage of ultrasonication with precipitation method over conventional method Mehta, Dhiraj; Mondal, Poonam; Saharan, Virendra Kumar; George, Suja This research work presents the synthesis of hydroxyapatite (Hap) nanorods for defluoridation of drinking water by using both conventional (CM) and ultrasonication with precipitation (USPM) methods. Calcium nitrate was reacted with potassium phosphate in presence of ammonia for controlled pH to synthesize Hap nanorods, which was characterized using FTIR, XRD, SEM, TG-DTA, and TEM/EDS for determining its phase composition, structural and thermal decomposition behavior. When USPM method was used for synthesis, the yield of the Hap nanorods was improved from 83.24 ± 1.0% to 90.2 ± 1.0%, and complete phase transformation occurred with formation of elongated Hap nanorods. Effects of process parameters such as solution pH, contact time and adsorbent dose were studied through response surface methodology (RSM). A simple quadratic model was developed using Central Composite Design (CCD) and optimum parameters for fluoride adsorption process were determined to be pH 7, contact time 3 h and adsorbent dose 7 g/L for maximum removal capacity. Fluoride removal efficiency was predicted to be 93.64% which was very close to the experimental value obtained at 92.86% using ultrasonically prepared Hap. Fluoride adsorption isotherms fitted the Freundlich isotherm with an adsorption capacity of 1.49 mg/g, while the kinetic studies revealed that the process followed pseudo-second order model. The treated water quality parameters such as residual fluoride, calcium leached, total hardness and alkalinity was investigated, and it was observed that all these parameters were within the permissible limits as per WHO and BIS standards. 2016-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/8153 Defluoridation studies with synthesized magnesium-incorporated hydroxyapatite and parameter optimization using response surface methodology Mondal, Poonam; Mehta, Dhiraj; George, Suja The severe impact of consumption of excess fluoride on human health has raised concerns for development of reliable materials for defluoridation of drinking water. This study deals with the synthesis of magnesium-incorporated hydroxyapatite (M-i-HAP) and evaluation of its defluoridation potential. Characterization studies revealed the bonding patterns, phase characteristics, and other microstructural details of the adsorbent synthesized, and the surface area was found to be 46.62 m2/g. Response surface methodology was used for optimization of fluoride adsorption on the adsorbent and development of the predictive model. The optimum conditions evaluated using central composite statistical design for fluoride removal were found to be 303 K, pH 7, 180 min contact time, and 10 g/L of M-i-HAP for treating fluoride solution of 10 mg/L. At these conditions, the actual removal experimentally achieved was 94.5% which was very close to the maximum removal predicted by the model (94.60%). The process followed pseudo-second-order kinetic model and the adsorption mechanism can be described by Langmuir isotherm with an adsorption capacity of 1.16 mg/g. The adsorbent was regenerated 91% using 0.1 M NaOH solution. Drinking water quality was assessed for various parameters and the treated water was found to be fit for consumption with all parameters such as pH, total dissolved solids, total hardness, alkalinity, and turbidity within permissible limit as per World Health Organization and Bureau of Indian Standards (BIS) guidelines. 2016-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/8132 Stochastic hygro-thermo-mechanically induced nonlinear static analysis of piezoelectric elastically support sandwich plate using secant function based shear deformation theory (SFSDT) Lal, Achchhe; Kulkarni, Nikhil M.; Siddaramaiah, Vijayakumari H. The second order statistics of transverse nonlinear central deflection of elastically supported piezoelectric laminated composite sandwich plate (ESPLCSP) subjected to hygro-thermo-mechanical loading using micromechanical approach is evaluated in this paper. System randomness as micro-level material properties of fiber and matrix, material properties of piezoelectric, laminate thickness, lamination angle, foundation parameters, and load intensity are taken as independent random variables. The mechanical loading is taken as uniformly distributed and sinusoidal loadings. The secant function based shear deformation theory (SFSDT) with von-Karman nonlinearity is used for basic formulation. The elastic and hygrothermal properties of the composite material are considered to be dependent on temperature and moisture concentration have been evaluated utilized micromechanical modeling. A Newton–Raphson method based on C0 nonlinear finite element method combined with mean centered second order perturbation technique (SOPT) proposed by present authors for the composite plate is extended for sandwich composite plate. The effect of random system properties with changing the plate geometry, stacking sequences, support conditions, foundation parameters, piezoelectric layers, fiber volume fraction and temperature, and moisture distribution on ESPLCSP is presented. The performance of proposed approach is validated through comparison with those available in the literature and independent Monte Carlo simulation (MCS). 2016-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/8128 Nano Mullite Bonded Refractory Castable Composition for High Temperature Applications Singh, Akhilesh Kumar; Sarkar, Ritwik Development of high pure alumina castable is studied by using synthesized mullite sol as the sole binder. Mullite sol is prepared by wet chemical route and is characterized by its solid content, particle size, thermal analysis, phase development with temperature, microstructure, etc. This sol is used at two different percentages in high alumina castable compositions with two different particle size distribution patterns. Conventional castable processing is done on the compositions and the characterizations are done after heat treatment at three different temperatures. Finally, the best composition is also compared with the commercially available silica sol containing high alumina castable with similar particle size distribution. Considerably improved hot strength, high corrosion resistance and flexural strength (hot modulus of rupture) are obtained for the mullite sol containing composition but with relatively lower thermal shock resistance. 2016-08-01T00:00:00Z