Electron donor concentration

Since anaerobic azo dye reduction is an oxidation-reduction reaction, a liable electron donor is essential to achieve effective color removal rates. It is known that most of the bond reductions occurred during active bacterial growth [48], Therefore, anaerobic azo dye reduction is extremely depended on the type of primary electron donor. It was reported that ethanol, glucose, H2/CO2, and formate are effective electron donors contrarily, acetate and other volatile fatty acids are normally known as poor electron donors [42, 49, 50]. So far, because of the substrate itself or the microorganisms involved, with some primary substrates better color removal rates have been obtained, but with others no effective decolorization have been observed [31]. Electron donor concentration is also important to achieve... 

If the surface complex is the chromophore, then the photochemical reductive dissolution occurs as a unimolecular process alternatively, if the bulk iron(III)(hydr)-oxide is the chromophore, then it is a bimolecular process. Irrespective of whether the surface complex or the bulk iron(IIl)(hydr)oxide acts as the chromophore, the rate of dissolved iron(II) formation depends on the surface concentration of the specifically adsorbed electron donor e.g. compare Eqs. (10.11) and (10.18). It has been shown experimentally with various electron donors that the rate of dissolved iron(II) formation under the influence of light is a Langmuir-type function of the dissolved electron donor concentration (Waite, 1986). 

One such set of circumstances is when it is possible, upon raising the electron donor concentration, to change the rate law from (62) to (61), indicating that kinetic control passes from forward electron transfer to bond breaking according to (63). The passage across the mixed kinetics region... 

Figure 12. Electrical conductivity as a function of relative electron (donor) concentration in P doped Si to illustrate the metal-nonmetal transition at 0 K. The relative P density is varied by changing nc with uniaxial stress on a single sample. The open circles are extrapolated to T = 0 K (from Thomas33).

The potential at which, under equilibrium conditions, the charge density is equal to zero is called the flat-band potential. An increase in electron donor concentration results in a decrease in the concentration of holes emd an increase in the concentration of conduction-band electrons. 

Thus, just as with the IB systems, the polymerization experiments with St included the investigation of the effect of time, temperature, electron donor concentration ([ED]), solvent polarity, Friedel-Crafts acid concentration ([MtX ]), and aging on polymerization rate (conversion), molecular weight, and molecular weight distribution. The experimental conditions together with the raw data are shown in Tables 12-19 in the Appendix. 

Figure 7. Decay of electron donor concentration as measured at pH 4.8 and as calculated by numerical simulation with dependence on n. Experimental signal-same conditions as in Figure 4. Because the concentration of silver ions after the puke is smaller than that of hydroquinone, the ordinate of the experimental plot is (OD-OD j/ODt=o- Numbers next to simulation curves correspond to n. The value of Is 2.25 X JO mol The best adjustment unth numerical simula-...

Figure 8. Decay of electron donor concentration as measured at pH 4.8 and as calculated by numerical simulation of dependence on (Same conditions as in...

The reaction order of propagation in respect of the Friedel-Crafts acid has been determined. Figure 18A shows the corresponding plot of In [kpNjJ vs In [TiClJ. The plot is linear with a slope close to unity indicating first order behavior. The figure also contains a second plot In (kpN) vs In ([TiCl ] — [TEA]), i.e., the Friedel-Crafts add concentration minus the electron donor concentration. This plot is also linear with a slope of close to unity suggesting first order behavior. 

After entrapment in DEAE-cellulose, the PSII activity of a chloroplast suspension was assayed as DCIP photoreduction with water as the electron donor. Concentration of reduced DCIP in the effluent increased rapidly after the onset of illumination, reaching a plateau after 10 min. The maximum level was sustained for 2h. Then, the activity decreased during continuous operation, reaching 50% of the initial activity after 4.5h. This decline seemed to be mainly due to a decrease in the activity of the chloroplasts, not the desorption of chloroplasts during operation. ... 

The biofilm subsists on the oxidation of an organic substrate, S (mM), which is delivered to the biofilm matrix via diffusive mass transport. The substrate is supplied at a constant concentration to a large, well-mixed anodic chamber. This allowed us to assume that the bulk concentration of substrate is constant because of the size of the chamber and the relatively slow consumption rate of substrate by the biofilm. The concentration at the biofilm surface is equal to the bulk concentration because of mixing in the anodic chamber and because of simplification of the model. The substrate utilization rate is controlled by both the substrate (electron donor) concentration and the eleetron acceptor concentration, through multiplicative Monod substrate utilization equations [37, 38]. Equations 9.1 and 9.2 simply state that the biofilm can only metabolize in the presence of both an electron donor and an electron acceptor. The lack of either one prevents biofilm metabolic activity. In our model, we assume that there are two possible electron transfer pathways thus, there are two substrate utilization equations. For diffusion-based EET, substrate utilization is given by ... 

Equations 9.3 and 9.4 ensure q will never exceed q. Furthermore, the ratio will not deviate from qy jq, which is determined by the relative availability of mediators or a conduction pathway, even if qy + q does exceed Thus, when EET is a mixture of diffusion-based and conduction-based mechanisms, the EET mechanism percentages will not be a function of substrate (electron donor) concentration. The overall substrate reaction rate due to metabolism, (mol m s ), is given by ... 

When conductivity is high, the upper biofilm layer near the aqueous phase boundary of a conductive biofilm can be active, even when the base is limited by a low electron donor concentration ... 

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