Phosphoric acid distribution ratios

Figure 19 presents the curves for phosphoric acid distribution between water (pure solution) and extractants comprising a quaternary amine and a sulfonic acid. The extraction is proportional to the concentration of the active components and decreases slightly on elevation of the temperature. The distribution curves show that these extractants, found suitable for sulfuric acid extraction, are not sufficiently basic for the extraction of HsPO i, which is a much weaker acid (free acid concentrations of about 6 M are required to reach loading of 1 mole of acid per mole of amine). An extractant comprising a long-chain tertiary amine (trilauryl amine, TLA, Alamine 304, produced by Henkel) and a-bromolauric acid (ABL, Miles Yeda) was tested. The distribution curves for phosphoric acid extraction from pure solutions are shown in Fig. 20. The extraction is proportional to the concentration of the active components and depends on the temperature. Note that whereas the extraction decreases on elevation of the temperature at the lower concentration range, it increases with temperature at concentration ranges at which the H PO /amine molar ratio is greater than one. Similar reverses in the effects of various parameters at about stoichiometric extraction were noted in the past. They are explained by shifting from the ion-pair formation mechanism to the H-bonding one [58,59].

During development of the Truex process, various monofunctional organophosphorus reagents [e.g., TBP DBBP (dibutylbutylphosphonate) HDEHP (di-(2-ethylhexyl)phosphoric acid)] were considered for removal of alpha-emitters from HNO3 waste solutions. Two typical flow sheets for the use of HDEHP and TBP are shown in Fig. 12.14. Because of the poor performance of these two extractants, the processes were complicated. Distribution ratios... 

The catalyst is sometimes diluted with charcoal in the ratio of 1 1 to 2 1 of catalyst to charcoal (21). The charcoal acts as an adsorbent for the phosphoric acid released under operating conditions and distributes the acid over a larger portion of the bed. The phosphoric acid acts as the actual catalytic agent. 

We hydrolyzed ATP and ADP in 1 N and 0.1 N HC1 and in buffered solutions at pH 4j nd 8 in which the hydrolysis medium was variously enriched in °0 to either 10% or 20%. To assess the isotopic enrichment of each such solution for use in the nucleotide hydrolysis experiments, we hydrolyzed PCI, in the solution, esterified the resultant phosphoric acid/inorganic phosphate (P.) by reaction with diazomethane, and determined the isotopic distribution of the trimethyl phosphate (TMPO) by mass spectrometry. The 1 N and 0.1 N HC1 hydrolyses were allowed to proceed for 45 min and 10 hr, respectively, at 70, insuring complete conversion of ATP into AMP + 2P. The pH 8 hydrolyses were allowed to proceed for 36 hr at 70 to a point (20-25% completion) at which the ratio of ADP to AMP established that 96% and 4%, respectively, of the P. released had arisen by the primary and secondary hydrolysis steps, namely, ATP ADP + P. and ADP " AMP + P. 0The pH 4 hydrolyses were allowed to proceed for 24 hr, also at 70, to 40% completion. 

Figure 5. Distribution coefficients of U (VI) between 5M aqueous phosphoric acid and mixture of HDEHDTP and neutral oxygen donors in solution in do-decane as a function of the reagent concentration ratio (1) 0.5M (HDEHDTP + POX 11), (2) 0.5M (HDEHDTP + TOPO), (3) 0.5M (HDEHDTP + TBP).

Figure 3. Distribution ratios of dibutyl phosphoric acid (HDBP), monobutyl phosphoric acid (H2MBP), phosphoric acid (HsPOk), dodecyl sulfuric acid (DSA), and diethylenetriaminetetraacetic acid (H5DTPA) vs. aqueous HN03 concentration organic phase = 2-ethyl-l-hexanol T = 25° and 50°C.

Alumina can be treated with phosphoric acid to produce the same effect, and as more phosphate is added, the MI sensitivity grows. Even silica can be impregnated with phosphoric acid, or a phosphate, to increase its sensitivity [332,640,641], Figure 165 shows the extreme change in polymer MW distribution that can be caused by 1-hexene addition to the reactor. There is a strong shift to the low-MW region. The degree of the shift is dependent on the amount of phosphate in the support. The catalyst with a P/Al atomic ratio of 0.9 produced a major shift, whereas the shift from the catalyst with a P/Al ratio of 0.2 was more like that of Cr/silica. 

In previous sections, it was explained how different precursors can be used to produce activated carbons and the type of porosity developed depending on the type of activation method applied. Thus, thermal activation imrmally yields adsorbents with a medium to liigh adsorption capacity, a medium micropore size distribution and no mesopore formation (except in the case of high bum-off ratios, where micropores may be of a large size). Phosphoric acid activation yields a carbon with a higher adsorption capacity than thermal activation and a wider micropore size distribution (even in the low mesopore range), whereas KOH yields extremely narrow microporous carbons. 

On the other hand, Dyrssen and Liem (1960) report (table 7) greater variation in both distribution ratios [for americium and europium extraction by dibutyl phosphoric acid (HDBP)] and in separation factors as a function of diluent. The separation factors and distribution coefficients are correlated (more or less consistently) inversely with the distribution ratio of the extractant between the phases. In this system, the largest separation factors are observed in n-hexane, chloroform, and carbon tetrachloride. Diluents capable of direct coordination (i.e., those possessing potential oxygen-donor atoms) are correlated with reduced distribution ratios and separation factors. The observations of greater separation factors in non-complexing diluents suggest that more effective separation is observed when the inner-coordination sphere of the hydrophobic complex is not disturbed. 

There are two apparent artifacts in this correlation. First, one would not expect based on these arguments that the acidic phosphoric acid esters HDOP, HDBP, and HDEH P (bars U, V, and W) would demonstrate as great a selectivity for europium as is observed. Similarly, there is no apparent reason for the enhanced selectivity demonstrated by 100% TBP for americium for extraction from 13 M HNOj (bar G). In the case of the phosphoric-acid extractants, the apparent anomaly is a manifestation of the steep slope of the linear relationship between distribution ratios and atomic number (cation radii) as shown in figs. 4 and 5, and a mismatch of the ionic radii of americium and europium. It is generally believed that the cation radius of americium is more nearly comparable to that of promethium or neodymium than europium (see table 1). The logSi J calculated from the the same data is —0.35. 

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