Dyeing pore model

The pore model of dyeing was first suggested for dyeing cellulose fibers in the thirties... 

The physical stmcture of fibres, such as cellulose, greatly influences the dye sorption process. The accessible volume of fibre to dye is generally termed the internal accessible volume (V), which represents the internal void space, or pores, within a fibre. In thermodynamics of sorption, V is referred to as the volume of the internal phase per kilogram of dry fibre (Lkg" ). Determination of the internal volume of fibre greatly influences the calculation of standard affinity associated with sorption (-A[x°). It has been shown that V can be determined based on a two-phase dye sorption model, expressed in a hnear logarithmic form, according to a trial-and-error procedure. """ The uniform presentation of dye Uquor to the textile material is of obvious importance. 

Two models are generally used to describe the diffusion of dyes into fibres. The first is the pore model, in which the movement of dissolved dyes is described as diffusion into the pores of fibres that are filled with water. In this model, the diffusion coefficients strongly depend on the number and size of pores in the fibre at fixed dyeing conditions. The assumption for the apphcability of this model is that the pores of the substrate are large in comparison to the molecular dimensions of the dye molecules, and that the pore network is accessible to the dyes. ... 

The pore model is mainly adopted for the diffusion of dyes into hydrophilic fibres from an aqueous solution in which fibres swell markedly. Therefore it is presumed that water-filled channels of the fibres provide a transfer route for dye molecules to reach their adsorption sites. However, Peters and Ingamells concluded that the pore model in its entirety cannot be accepted. The free volume mechanism mainly dominates when hydrophobic fibres are dyed. 

The figure legend reads Model of the unidirectional diffusion of dye between coupled oligodendrocytes and astrocytes, based on differences in connection pore diameter. Like a fish in a fish trap, dye molecules (black circles) can pass from an astrocyte to an oligodendrocyte (A) but not back in the other direction (B). ... 

In all these experimental models, the MTX effect could be divided in three phases (1) a rapidly developing Ca conductance through NSCC (2) uptake of vital dyes (ethidium, YO-PRO and POPO-3) and Fura-2 loss via a cytolitic-oncotic pore (COP) and (3) a secondaiy phase of vital dye uptake and Fura loss in which membrane permeability to larger molecules like LDH enzyme occurs. Fig. 4.4 shows permeability changes in a population study of bovine aortic endothehal cells (BAECs) treated with 0.3 nM MTX. Two phases of ethidium bromide uptake may be observed (steps 2 and 3 of the death process), the second phase correlating in time with LDH release (step 3 of death process). 

The set of equations formed by fheseequations is then solved numerically. Such models have been used extensively to describe breakthrough curves onto activated carbon of mono-component solutions of metal ions, micro-organic compounds or dyes [20-22], Some studies have demonstrated that they could be used to model binary namic adsorption [23] but they may not be applied in the case of complex multi-solute solutions. In addition, they do not take into account the pore characteristics of activated carbon materials, which are known to influence strongly the adsorption of micro-orgaiucs. In these cases, statistical tools like neural networks may be used in order to introduce such parameters as explicative variables. 

Chitosan/kaohn/nanosized Y-Fe Oj composites were prepared by a micro emulsion process and characterized by TEM, SEM, and WAXRD. Many pores and pleats were visible on the surface of the composites and provided a good condition for dye adsorption. Methyl orange was selected as a model anionic azo dye to examine the adsorption behavior of the composites. About 71% of methyl orange was adsorbed within 180 min, from 20 mg/1 at ph 6 by 1.0 g/1 adsorbent dosage. The composites can... 

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