Mathematical modeling of pulp washing on rotary drums and their numerical solution for various adsorption isotherms
The mechanism of the displacement washing of the bed of pulp fibers is mathematically modeled by the basic material balance equation. Linear as well as non-linear adsorption isotherms are used to describe the relationship between the concentration of the solute in the liquor and concentration of the solute on the fibers. In the present study, the numerical solutions are obtained of pulp washing model with different adsorption isotherms. For the numerical solution “pdepe” solver in MATLAB is applied on the axial domain of the system of partial differential equations. Numerical results thus obtained are compared with earlier workers analytically and numerically. The comparison shows that results are in good agreement with both analytically as well as numerically and also show the suitability of the isotherm coupling with the washing model. The technique used in the present investigation is simple, elegant and convenient for solving two point boundary value problems with varying range of parameters.
Transport of Methylene Blue Through An Organic Porous Coco Peat Medium Column
Abstract — Industries such as textile and paper that use dyes to color their final product discharge substantial volumes of highly colored water into natural water bodies. Understanding the mechanisms of dye removal from wastewater before discharge to surface waters is important since dyes may disrupt biological processes in the water environment. In this study, the feasibility of using coco peat in removal of methylene blue is demonstrated. A mathematical model describing the chemical transport and removal of Methylene Blue (MB) onto a highly organic biosorbent coco peat was solved in MATLAB using a semi-discrete finite difference with fourth order upwind differentiation. The needed parameters on adsorption of MB onto a biosorbent coco peat were obtained using batch experiment. The batch experiment indicated coco peat is a very good adsorbent of MB with a removal efficiency of 99.61%. It was also shown that the adsorption at equilibrium obeys the Langmuir isotherm with parameters such as maximum adsorption capacity, q m , and the Langmuir coefficient, K L determined for all the temperatures investigated. A column experiment was carried out to obtain effluent breakthrough curves used for calibrating the mathematical model. A linear driving force coupled with solid diffusion model was applied successfully to the experimental data to determine the three major transport parameters, axial dispersion coefficient, D L , external mass transfer coefficient, k f , and solid diffusivity, D s . The model was tested and fitted well on one experimental case with D L = 1.1304E-05 m 2 s -1 , k f = 3.6399E-04 m s -1 , D s = 3.34871E-08 m 2 s -1 (RMSE = 0.0009). The results also show that the breakthrough curves are dependent on D L and external k f , but not on D s . Keywords— Methylene Blue removal, Coco Peat absorbent, Modeling Break-through  curves
Stereoselective disposition of ibuprofen enantiomers in infants.
The pharmacokinetics of the enantiomers of ibuprofen were investigated after oral administration of a single 7.6 +/- 0.3 mg kg-1 dose of the racemate in 11 infants. Mean (+/- s.d.) half-lives were 1.6 +/- 0.5 h for S(+) and 1.5 +/- 0.5 h for R(-) and mean (+/- s.d.) AUC values were 31.5 +/- 14.3 mg l-1 h for S(+) and 36.6 +/- 13.8 mg l-1 h for R(-). Since plasma concentrations of the active S(+)-isomer were lower than those reported in adults, a higher dosage might be required in infants.