Citric acid concentrations 358

Time, h DO, mgT-1 Citric acid concentration, gT-1 Cell dry weight, gT-1 Sugar concentration, gT-1... 

Citric acid concentration (%) pH Reducing sugars (%) Non-reducing sugars (%)... 

The design chosen is a full factorial 2 with two levels of each of the three factors, acetic acid concentration, methanol concentration and citric acid concentration. The low ( —) and high ( + ) levels of each are shown in Table I. 

A full factorial 2 design allows the study of three main factors and their interactions to be carried out in eight experiments or runs. The first requirement is to set out the experimental design matrix. This is shown in Table 2. A is the molar concentration of the acetic acid, M is the methanol concentration, %v/v, and C is the citric acid concentration, g All combinations are covered in eight experimental runs. Note that this is not the order in which they are performed. These should be carried out in a random sequence. There will be a value of the CRF for each run. 

What is clear without the further aid of statistics is that the methanol concentration is the most important factor. Equally, it is clear that the citric acid concentration is not significant nor are three of the four interactions. Are the methanol concentration main effect and/or the interaction between the methanol and citric acid concentrations significant One way forward is to plot the data from Table 6 on normal probability paper. If all these data are insignificant then they will lie on a straight line. If values are observed that are a long way off the line it is likely that the effects or interactions are significant. 

If the exercise is repeated for the methanol-citric acid concentration interaction, MC, the plot in Figure 15 results. Here the lines are clearly non-parallel and support the view that this interaction may well be analytically significant. 

To illustrate the variation in composition of an aqueous solution of a polyprotic weak acid species, it is useful to plot a species distribution curve such as the one for citric acid shown in Figure 20-1. The parameter plotted versus pH for each species is a, the fraction of the total citric acid concentration in the form of a particular species. 

Figure 12. Effect of ascorbic and citric acid concentration (added post-droning) and frozen storage on TEA values of MDFM (Series III). Key , control , dip treatment only, no postaeboning additions (dip consists of 0.5% ascorbic acid, 0.5% citric acid, 0.2% KENA, 0.05% Na2EDTA) M, 0.1% ascorbic acid, 0.1% citric acid + others O, 0.3% ascorbic acid, 0.3% citric acid + others A, 0.5% ascorbic acid, 0.5% citric acid + others , Freez-Gard. (Reproduced, with permission, from Ref. 470. Copyright 1977, Institute of Food Technologists.)...

Other changes in the extractability of the actinides are performed using complexing agents. The distribution coefficients of Pu(lV) with various citric acid concentrations is demonstrated for the system TBP/HNO3 in table 3 and figure 3. The range of the HNO concentrations corresponds to that of the waste effluents from the coextraction steps of the THOREX-process. 

Several examples of the applications of SLMs in the removal of antibiotics from wastewater are shown below. Kawasaki et al. [154] studied the application of the flat-sheet SLM in the removal of erythromycin A from aqueous matrices. The feed phase consisted of citric acid (concentration = 0.025 mol dm 3), boric acid (concentration = 0.100 mol dnr- j, and sodium phosphate (concentration = 0.050 mol dm ). The SLM was prepared from PTFE flat sheet porous with 1-decanol as the diluent. 

Earlier studies [24,25] have shown that in addition to the concentration of organic species, temperature is the most significant variable controlling the kinetics of the citric acid-H20 system. Cody et al. [25] further show that for a given citric acid concentration, the system exhibits a very complex behavior at high P and T. These studies have described the behavior of the system under hydrothermal conditions in detail and have formed the basis for interpretation of these diamond cell experiments. In this study, we have used in-situ Raman... 

PHEMA into an SBF solution. At the higher released citric acid concentrations, the formation of calcium citrate crystals can bring about a depletion of the calcium ion concentration in the SBF solution, so less calcium phosphate will precipitate onto the polymer. At lower citric acid concentrations, the inhibition effect of citrate anions on formation of calcium phosphates has been attributed to the complex equilibria between calcium, citrate and phosphate ions (27-29). Precipitated calcium phosphates may undergo dissolution via surface exchange between phosphate and citrate ions (calcium citrate is much more soluble than calcium phosphate). 

The use of ILMs for the separation of fermentation products such as acetic and citric acid has been recently reported by several investigators. Kuo and Gregor (40) and Klani et al. (41 ) used immobilized liquid membranes to extract acetic acid from aqueous solutions. While Kuo and Gregor (40) did demonstrate the concept of facilitated transport of acetic acid, the permeation rates they reported were quite low. Babcock et al. ( ) reported the extraction of citric acid from actual fermentation broth. The effects of temperature, agent-solution composition, and citric acid concentration on transport rates were investigated. 

The rate of oxidation of dtric add by Ce(IV) in sulfuric acid has been reported by Tripathi et al. (1980). The reaction rate dependence on the concentration of the dtric acid indicates very weak precursor complex formation, if any (i.e. the reaction is very nearly first-order in citric acid concentration). The authors propose that Ce(S04)2 retards the rate of oxidation and Ce(S04) is the most reactive ceric species. It is interesting to note that citric acid, which might be considered the strongest com-plexant of the acids reported here, does not form a precursor complex in sulfuric acid while the keto acids apparently do. 

Data are in Table 13-3. Note A similar scheme is used commercially for citric acid concentration using a more selective solvent. 

Citric acid, concentrated 200 93 Methyl isobutyl ketone 60 16... 

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