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The adsorption capacities of new biomaterials derived
from lemon leaf (Citrus sp.) toward
fluoride ions have been explored by varying different physicochemical
parameters such as pH, initial concentration, adsorbent dose, contact time,
stirring rate and temperature. The entire study was done through batch process.
Maximum fluoride adsorption of 96.9% - 98.8% was achieved with an initial concentration
of 10 mg/L. Langmuir isotherm model well expressed fluoride ad- sorption
onto LLD-1, LLD-2 and LLD-3. According to correlation coefficient, the fluoride
adsorption onto these 3 ad- sorbents was correlated well with
pseudo-second-order kinetic model. From thermodynamic study, the spontaneous
nature and feasibility of the adsorption process with negative enthalpy (ΔH0)
value also supported the exothermic nature were shown. The rate
of fluoride adsorption was mathematically described as a function of
experimental parameters and was modeled through Box-Behnken (Response surface
methodology). The results showed that the responses of fluoride adsorption
were significantly affected by the quadratic term of pH, initial concentration,
contact time and temperature and the statistical analysis was performed by
ANOVA which indicated good correlation of experimental parameters.
An initial value problem concerning the motion of an incompressible, electrically conducting, viscoelastic Oldroyd-B fluid bounded by an infinite rigid non-conducting plate is solved. The unsteady motion is generated impulsively from rest in the fluid due to half rectified sine pulses subjected on the plate in its own plane in presence of an external magnetic field. It is assumed that no external electric field is acting on the system and the magnetic Reynolds number is very small. The operational method is used to obtain exact solutions for the fluid velocity and the shear stress on the wall. Quantitative analysis of the results is presented with a view to disclose the simultaneous effects of the external magnetic field and the fluid elasticity on the flow and the wall shear stress for different periods of pulsation of the plate. It is also shown that the classical and hydromagnetic Rayleigh solutions appear as the limiting cases of the present analysis.