Kinetics of the extraction of uranium(VI) from nitric acid solutions with bis(2-ethylhexyl)phosphoric acid

Abstract

A transfer cell of constant interfacial area was utilized to measure initial rates of the extraction and the stripping with aqueous phases containing 0.1114 mol/dm3 of nitric acid and up to 0.0267 mol/dm3 of uranium and kerosene diluted organic phases containing 0.01265-0.0894 mol/dm3 of dimeric HDEHP and up to 0.00963 mol/dm3 of uranium. The extraction rate is one-half order with respect

Mass-Transfer Characteristics of a Membrane Permeation Cell and Its Application to the Kinetic Studies of Solvent Extraction

“…This conclusion is reached by comparing the resistance of chemical reaction at the interface to that in aqueous stagnant layer, if the chemical reactions in both sites obey Eigen's mechanism. From the nature of D2EHPA such as interfacial activity and extremely low aqueous solubility, in the present work, the formation of VIV-D2EHPA complex is considered to be interfacial, as has been accepted by most researchers (Batrakova et al, 1989;Huang and Huang, 1988;Ihm et al, 1988; Juang and Chang, 1993;Kunaev et al, 1984; Miyake et al, 1990;Svendsen et al, 1990).…”

“…Regarding reactions by eqs 16a, 16b, 16f, and 16g as fast steps and reactions by eqs 16c-16e as slow steps (Huang and Huang, 1988;Kunaev et al, 1984), we obtain the forward reaction rate by eq 9. (18) Similarly, from eq 10 the backward reaction rate is Rb…”

“…These techniques include a dispersed-phase contactor with centrifuge (AKUFVE flow system and the like), a stirred transfer cell (Lewis cell), a diaphragm cell, single-drop and growing-drop columns, and a laminar liquid jet. Of these the stirred transfer cell where two liquid layers are individually stirred appears to be simplest and easiest to operate (Huang andHuang, 1988, Ihm et al, 1988; Juang and Chang, 1993;Komasawa et al, 1980; Miyake et al, 1990;Svendsen et al, 1990). However, it must be modified to improve bulk mixing or maintain constant interfacial area or to achieve forced convections to the interface.…”

Mechanism of Photoreductive Stripping of Iron(III) in a Liquid−Liquid Extraction System and Its Application for a Hydrometallurgical Process

“…The iron(III)−extractant complex is found to be excited in the organic phase and to be donated an electron from the water at the aqueous/organic interface. Assuming the extractant to exist as a monomeric species at the interface, as was found in the case of D2EHPA, the elementary reaction of eq 7 can be expressed in more detail as eqs 9−14 If the rate-determining step is the photochemical reduction of iron(III) as shown by eq 13, the overall reaction rate equation can be expressed by eq 15…”

Evaluation of plutonium(IV) extraction rate between nitric acid and tri‐n‐butylphosphate solution using a glass chip microchannel

“…In these cases, mixing is rapid, so relative reaction rates can be identified. However, the data are device specific, and the interfacial area is unknown and unpredictable . The single‐drop method and Lewis cell technique are primarily used to measure extraction rates across liquid–liquid interfaces .…”