scholarly journals Mass Transfer Studies on Adsorption of Phenol from Wastewater UsingLantana camara, Forest Waste

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
C. R. Girish ◽  
V. Ramachandra Murty
Keyword(s):  
Mass Transfer ◽  
Lantana Camara ◽  
Model Parameters ◽  
External Mass Transfer ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Forest Waste ◽  
Mass Transfer Studies ◽  
Rate Limiting

Adsorption is one of the important treatment methods for the removal of pollutants from wastewater. The determination of rate controlling step in the process is important in the design of the process. Therefore, in the present work, mass transfer studies were done to evaluate the rate-limiting step in the adsorption of phenol from aqueous solution ontoLantana camara. Different mass transfer models were used to find the rate-limiting step and also to find the values of external mass transfer coefficient and diffusion coefficient. The Biot number was found to investigate the importance of external mass transfer to intraparticle diffusion. From the various models studied and the Biot numbers obtained, it was found that the adsorption onLantana camarawas controlled by film diffusion. The sensitivity analysis was performed to study the significance of the model parameters on the adsorption process.

scholarly journals DETERMINATION OF l-HISTIDINE IN NANOGRAM AMOUNTS AND THE QUESTION OF ITS OCCURRENCE IN MAST CELLS

1972 ◽  
Vol 20 (11) ◽  
pp. 917-922 ◽  
Author(s):  
DAVID I. WILKINSON ◽  
DAVID GLICK
Keyword(s):  
Mast Cells ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Peritoneal Mast Cells ◽  
Before And After ◽  
Chromatographic Detection ◽  
Rat Peritoneal Mast Cells ◽  
Rate Limiting

In an attempt to clarify the question of whether histidine is stored in the mast cell for coversion to histamine or whether the rate of conversion is rapid enough to prevent accumulation of histidine so that the rate-limiting step is the histidine uptake, it was found that no histidine was demonstrable in rat peritoneal mast cells by either quantitative analysis or paper chromatographic detection. Microadaptation of Hassall's method, based on conversion of l-histidine by histidase to urocanic acid and measurement of the latter by its absorbance at 277 nm, was made to permit determination of histidine in nanogram amounts in the presence of histamine. This adaptation was found reliable when compared with the o-phthalaldehyde method in estimation of l-histidine in serum and in insulin hydrolysate, and then it was applied to analysis of mast cells before and after l-histidine uptake in vitro. The adaptation should be generally useful in microanalysis of l-histidine in histologically and cytologically defined samples.

Determination of the Isotope Effect of the Enzymatic Oxidation of (R)Carnitine by Displacement of the Equilibrium via Mass Action

1975 ◽  
Vol 30 (7-8) ◽  
pp. 438-441
Author(s):  
Klaus Brendel ◽  
Rubin Bressler ◽  
Miguel A. Alizade
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Isotope Effect ◽  
Mass Action ◽  
Enzymatic Oxidation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Different Temperatures ◽  
Acid Hydrochloride ◽  
Rate Limiting

Abstract An isotope effect of the dehydrogenation of (R) Carnitine [(R) 3-hydroxy-4-trimethylamino-butyric acid hydrochloride] catalyzed by (R) carnitine dehydrogenase [(R) carnitine: NAD oxido-reductase E.C. 1.1.1.108] from Pseudomonas aeruginosa was measured at different temperatures. It was found that k1H/k3H does not vary greatly with changes of temperature. The value of 3 for k1H/k3H measured at small initial conversions strongly indicated that the rate limiting step of the oxidation of (R) carnitine is the cleavage of the C-H bond at C3.

scholarly journals Probing Differences in Mass-Transfer Coefficients in Beaker and Stirrer Digestion Systems and the USP Dissolution Apparatus 2 Using Benzoic Acid Tablets

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2168
Author(s):  
Timothy A. G. Langrish ◽  
Chao Zhong ◽  
Lizhe Sun
Keyword(s):  
Mass Transfer ◽  
Benzoic Acid ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
External Mass Transfer ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Rate Limiting Step ◽  
Dissolution Apparatus ◽  
Rate Limiting

Measurements of external mass-transfer coefficients for dissolution have been made with benzoic acid tablets with a diameter of 13 mm and approximately 3 mm thick, using two different dissolution systems. One system has been a beaker with a platform for the tablet and either 80 mL or 120 mL of water, with three different types of stirrers, and the other has been a USP dissolution apparatus 2 (paddle) with either 200 mL or 900 mL water. Various stirring speeds have also been used in the different pieces of equipment. The same mass-transfer coefficient may potentially be obtained from the same tablet by adjusting the operating conditions in the two different devices. The ranges of the external mass-transfer coefficients measured in both devices overlapped significantly, with the range being 0.193–4.48 × 10−5 m s−1 in the beaker and stirrer system and 0.222–3.45 × 10−5 m s−1 in the USP dissolution apparatus 2. Dimensional analysis of the results, using Sherwood and Reynolds numbers, shows that the Ranz–Marshall correlation provides a lower bound for estimates of the Sherwood numbers measured experimentally. Calculations of time constants for mass transfer suggest that mass transfer may be a rate-limiting step for dissolution and food digestion under some circumstances. The range of mass-transfer coefficients measured here is representative of other measurements from the literature, and the use of the Ranz–Marshall correlation supports the suggestion that this range of values should be generally expected in most situations.

scholarly journals Mechanism of Up-regulation of Starch Synthesis in Mature Leaves of Transgenic Apple Trees with Decreased Sorbitol Synthesis

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1009D-1009
Author(s):  
Rui Zhou ◽  
Lailiang Cheng ◽  
Abhaya Dandekar
Keyword(s):  
Transgenic Plants ◽  
Starch Synthesis ◽  
Redox Status ◽  
Mature Leaves ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Transgenic Apple ◽  
Hexose Phosphates

The reaction catalyzed by ADP-glucose pyrophosphorylase (AGPase) to form ADP-glucose is a regulatory and rate-limiting step in starch synthesis in plants. In response to decreased sorbitol synthesis, starch synthesis was up-regulated in the transgenic apple plants. In this study, we examined both redox and metabolite regulation of AGPase to understand the mechanism responsible for the up-regulation of starch synthesis. No difference in the monomerization/dimerization of apple leaf AGPase small subunits was observed between the transgenic plants and the untransformed control. NADP-dependent malate dehydrogenase, indicative of chloroplastic redox status, did not show significant change in the transgenic plants either. Determination of key metabolites with nonaqueous fractionation indicated that concentrations of hexose phosphates (mainly glucose-6-phosphate and fructose-6-phosphate) were higher in both the cytosol and chloroplasts of the transgenic plants than in the control, whereas 3-phosphoglycerate (PGA) concentration in the chloroplast was not higher in the transgenic plants. We conclude that accumulation of hexose-phosphates results in a decrease in inorganic phosphate (Pi) concentration and an increase in PGA/Pi ratio in the chloroplast, leading to up-regulation of starch synthesis via activating AGPase.

scholarly journals Sensitivity analysis for an elemental sulfur-based two-step denitrification model

2018 ◽  
Vol 78 (6) ◽  
pp. 1296-1303 ◽  
Author(s):  
A. Kostrytsia ◽  
S. Papirio ◽  
M. R. Mattei ◽  
L. Frunzo ◽  
P. N. L. Lens ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Elemental Sulfur ◽  
Kinetic Constant ◽  
Specific Area ◽  
Maximum Growth ◽  
Model Parameters ◽  
Model Stability ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Abstract A local sensitivity analysis was performed for a chemically synthesized elemental sulfur (S0)-based two-step denitrification model, accounting for nitrite (NO2−) accumulation, biomass growth and S0 hydrolysis. The sensitivity analysis was aimed at verifying the model stability, understanding the model structure and individuating the model parameters to be further optimized. The mass specific area of the sulfur particles (a*) and hydrolysis kinetic constant (k1) were identified as the dominant parameters on the model outputs, i.e. nitrate (NO3−), NO2− and sulfate (SO42−) concentrations, confirming that the microbially catalyzed S0 hydrolysis is the rate-limiting step during S0-driven denitrification. Additionally, the maximum growth rates of the denitrifying biomass on NO3− and NO2− were detected as the most sensitive kinetic parameters.

Determination of the rate-limiting step(s) in the biosynthetic pathways leading to penicillin and cephalosporin

1992 ◽  
Vol 10 (3-4) ◽  
pp. 157-163 ◽  
Author(s):  
John J. Usher ◽  
Doris W. Hughes ◽  
Mary Ann Lewis ◽  
Shu-Jen D. Chiang
Keyword(s):  
Biosynthetic Pathways ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
Sign in / Sign up

Export Citation Format

Share Document