Citric acid is the most widely used organic acid in the field of foods and beverages as an acidulant as well as in pharmaceutical and chemical products. Generally, surface or submerged fungal fermentation mainly with aspergillus niger is utilized for citric acid production. However, the submerged fermentation method is the most used method for citric acid production.1,2 The method of calcium sa...

Convergent radial flow tracer tests have a complex spatial nonaxial transport structure caused by the flow in the vicinity of the injection well and its finite mixing volume. The formulation of the boundary value problem, and especially the treatment of the boundary conditions at the injection well, is nontrivial. Hodgkinson and Lever [1983], Moench [1989, 1991], and Welty and Gelhar [1994] hav...

An approximate analytical solution to the advection-dispersion equation was derived to describe solute transport during spherical-flow conditions in single-well push-pull tests. The spherical-flow case may be applicable to aquifer tests conducted in packed intervals or partially penetrating wells. Using results of two-dimensional numerical simulations, we briefly illustrate the applicability of...

Geochemical heterogeneities may cause spatial variations in virus inactivation rates resulting from interactions with minerals leading to differences in natural disinfection capacity within an aquifer. Column studies investigating the interaction of the bacteriophage H40/1 with natural sands sampled from the Kappelen test site (Kappelen), Bern, Switzerland indicated that inactivation rates are ...

Modeling the contaminant transport process in soils requires the solute transport parameters. Displacement experiments were carried out on soil columns (Sand – Silt – Clay) by injecting a solution of 0.8 M KCl in a steady state. Breakthrough curves are symmetrical, characteristics of an equilibrium solute transport. The hydrodynamic dispersion coefficients were estimated by optimizing the measu...

22 23 Prediction of breakthrough curves for continuous sorption characterization is generally 24 performed by means of simple and simplified equations. These expressions hardly have 25 any physical meaning and, besides, do not allow extrapolation. A novel and simple 26 approach, based on unsteady state mass balances, is presented herein for the simulation 27 of the adsorption of Cr(III) ions fr...

The main objective of this research is stability determination of activated carbon adsorbent at fixed bed adsorption column for desulfurization of diesel fuel by mathematical modeling. This model is based on mass balances. Equations that are the outcome of mass balances are known as the second degree of partial differential equations, and they must be solved together simultaneously...

Adsorption of gold cyanide on three types of Activated Carbons (ACs) has been investigated in batch and column adsorption conditions. Applied ACs have been derived from different crops precursors i.e., coconut shell (CAC), peach stone (PAC), and walnut shell (WAC). As peach stone and walnut shells are abundant agricultural residues in Iran, the activated carbons produced from these precurso...

We present a methodology for calculating the conditional temporal moments of kinetically sorbing solutes based on the conditional temporal moments of non-reactive tracers. The methodology is based on a Lagrangian description of solute transport in heterogeneous media, and it can be applied to a large variety of flow configurations and mass-transfer ratelimited processes. A stochastic approach i...