Abstract-Textile effluent is rich in hydrolyzed dyes that need to be removed. This study presents an evaluation of the potential of the enzyme horseradish peroxidase to remove the hydrolyzed dyes Reactive Blue 21 (RB 21) and Reactive Red 195 (RR 195) from cotton fiber and the effluent of the dyeing process. The parameters pH, dye concentration and temperature were evaluated to determine the optimal conditions to remove the dyes. The studies of removal of the dyeing effluent led to an increase of degradation for all tested colors. The use of the enzyme horseradish peroxidase as a biocatalyst can be a viable technological alternative to remove some hydrolyzed dyes.

Abstract Natural convection in superimposed layers of fluids heated from below is commonly observed in many industrial and natural situations, such as crystal growth, co-extrusion processes and atmospheric flow. The stability analysis of this system reveals a complex dynamic behavior, including the potential multiplicity of stationary states and occurrence of periodic regimes. In this study, a linear stability analysis (LSA) was performed to determine the onset of natural convection as a function of imposed boundary conditions, geometrical configuration and specific perturbations. To investigate the effects of the non-linear terms neglected in LSA, a direct simulation of the full nonlinear problem was performed using computational fluid dynamics (CFD) techniques. The numerical simulation results show an excellent agreement with the LSA results near the onset of convection and an increase in the deviation as the Rayleigh number increases above the critical value.

In this paper, the volume averaging transport equations of two reactive processes in porous media are presented. The porous media are characterized by different length scales and the information describing the mass transfer mechanisms is transferred hierarchically between scales by applying the volume averaging method. This development provides the theoretical definition of effective transport coefficients, which can be predicted through solution of the closure problems. The theoretical calculation of effective diffusion tensors of the species in the particle pores is presented. Two closure problems are deduced through mathematical formulation of two different scales: microporous (process 1) and macroporous (process 2). In order to solve these closure problems, the volume finite method is used as the numerical methodology. Good agreement is verified between the numerical solutions obtained in this study and the data found in the literature for the closure problems considered.