Intensified reactive extraction of 4-hydroxypyridine with di(2-ethylhexyl) phosphoric acid in 1-octanol by using tributyl phosphate

The efficient separation of amphoteric organic compounds from dilute solutions is of great importance in the industrial field. In the present work, the reactive extractions of 4-hydroxypyridine(4-HP) with tributyl phosphate(TBP), di(2-ethylhexyl) phosphoric acid(D2EHPA) and TBP + D2EHPA dissolved in 1-octanol were investigated, respectively. The influences of the initial concentrations of TBP, D2EHPA and TBP + D2EHPA on distribution ratio(D) were discussed, as well as the reactive extraction mechanism were proposed. The obvious intensification effect was observed when the mixture of TBP and D2EHPA was used as extractant. The best extraction conditions were found to be of the molar ratio of D2EHPA and TBP at 2:1 and the equilibrium aqueous pH at 3.50-4.50. D values increased with the increase of the total concentration of TBP and D2EHPA in 1-octanol. Especially, the analysis on the extraction mechanisms clearly indicate(i) TBP in 1-octanol shows negligible reactive extraction toward 4-HP,(ii) D2EHPA in 1-octanol exhibits moderate extraction effect by forming 4-HP:D2EHPA(1:1) and 4-HP:2D2EHPA(1:2) type complexes, while(iii) D2EHPA in TBP/1-octanol demonstrates the maximum distribution ratio with the 4-HP:D2EHPA(1:1) type complex domination. The discussion provides new insights on the mechanism and opens a new way for the intensified extraction of amphoteric organic compounds by using the mixture of multiple extractants in the diluent.

Adsorption mechanism of mixed salicylhydroxamic acid and tributyl phosphate collectors in fine cassiterite electro-flotation system

Two reagents including salicylhydroxamic acid(SHA) and tributyl phosphate(TBP) were tested as collectors either separately or together for electro-flotation of fine cassiterite(<10 μm).Subsequently,the flotation mechanism of the fine cassiterite was investigated by adsorbance determination,electrophoretic mobility measurements and Fourier transform infra-red(FT-IR) spectrum checking.Results of the flotation experiments show that with SHA as a collector,the collecting performance is remarkably impacted by the pulp pH value as the floatability of cassiterite varies sharply when the pH changes,and flotation with SHA gives distinct maximum at about pH 6.5.Additionally,the floatability of cassiterite is determined by using SHA and TBP as collectors.The range of pulp pH for good floatability is broadened in the presence of TBP as auxiliary collector,and the utilization of TBP improves the recovery of cassiterite modestly.Moreover,the optimum pH value for cassiterite flotation is associated with adsorbance.The results of FT-IR spectrum and the electrophoretic mobility measurements indicate that the adsorption interaction between the collectors and the cassiterite is dominantly a kind of chemical bonding in the form of one or two cycle chelate rings due to the coordination of carbonyl group,hydroxamate and P=O group to the metal tin atoms,where the oxygen atoms contained in carbonyl group,hydroxamate and P=O group of the polar groups have the stereo conditions to form five-membered rings.In addition,the adsorption interactions of SHA and TBP on the surfaces of cassiterite are also dominated by means of hydrogen bonds.

A Study on Stoichiometry of Complexes of Tributyl Phosphate and Methyl Isobutyl Ketone with Lithium in the Presence of FeCl_3

To study the characteristic of liquid-liquid extraction equilibrium of lithium from brine sources, the complexes formed from tributyl phosphate （TBP） and methyl isobutyl ketone （MIBK） with lithium were investi- gated using FeCl3 as coextracting agent. Liquid-liquid extraction reaction mechanisms were proposed and the stoichiometry of tetrachloroferrate（III） complex with lithium was obtained by regressing the experimental data. It is found that the stoichiometry of tetrachloroferrate（III） to lithium in the complex is 1 ： 1 with either TBP or MIBK as extractant in kerosene. The stoichiometry of the complex of TBP with Li was 1 ： 1 and that of MIBK with Li was 2 ： 1. The formed complexes of TBP and MIBK with lithium are determined to be LiFeCla-TBP and LiFeC14.2MIBK, respectively, according to the rule of neutralization.

Extraction of cerium(Ⅳ) using tributyl phosphate impregnated resin from nitric acid medium

Tributyl phosphate （TBP） solvent was used for impregnation into Amberlite XAD-16 nonionic polymeric resin beads using the wet method to prepare solvent impregnated resin （SIR）. Undiluted TBP in a ratio to the resin support （volume to mass） of 6.0 at room temperature （RT） in 24 h was impregnated the resin with a mass ratio of 1.944, while the prepared gross sample of SIR at the ratio of solvent to resin of 3.0 was impregnated with a mass ratio of 1.88. Cerium（Ⅳ） oxide concentrate, prepared from crude Egyptian monazite sand, containing 37% cerium, 1.6% thorium and about 40% the other trivalent rare earth oxides, was used to prepare cerium（Ⅳ） nitrate solution for extraction using the prepared SIR. The impregnated resin was satisfactory for Ce（Ⅳ） extraction from nitric acid medium at room temperature. Cerium loading capacity of the impregnated resin reached 95.6% of the calculated theoretical capacity （173 g/kg （Ce/SIR）） under the conditions of 51.57 g/L cerium and 2.48 g/L thorium, 5.0 mol/L free nitric acid, solution to resin ratio of 10.0 and contacting the phases for 5.0 min. The loading capacity reached 98.75% when cerium concentration was increased to 91.43 g/L under the same conditions.

Solvent extraction mechanism and precipitation stripping of bismuth(Ⅲ) in hydrochloric acid medium by tributyl phosphate

Tributyl phosphate(TBP) was employed for the Bi(Ⅲ) extraction from hydrochloric acid medium.The effects of extraction time and material concentration were examined.The replacement mechanism between the anion(Cl^-) and TBP was proposed for extraction.The results show the species extracted into the organic phase were found to be mainly BiCl_3·x TBP(x=2 or 3).Thermodynamic parameters of the extraction reaction were obtained from the thermodynamics analysis,which illustrates that higher temperatures show a negative effect on the extraction.Extraction isotherm was obtained with 2.16 mol/L TBP for a typical solution containing 0.1 mol/L of bismuth and 1.0 mol/L of hydrochloric acid.About 98.5 % of bismuth has been extracted from the leaching solution under the optimum condition.Moreover,oxalate was explored as a precipitation stripping agent for BiCl_3·x TBP(x=2 or 3) complexes,by which Bi(Ⅲ) was stripped in the form of Bi_2(C_2O_4)_3·7H_2O.A stripping efficiency of 99.3% was obtained in only one stage at the phase ratio of 1 and TBP also could be recycled.Therefore,the method is an efficient,effective and highly selective approach to extract Bi(Ⅲ) and to recover metal bismuth.

Ion-pair induced solvent extraction of lithium(Ⅰ)from acidic chloride solutions with tributyl phosphate

Lithium(Li)is an important energy metal in the 21st century.However,the selective recovery of Li is still a big challenge,especially from acidic solutions with multiple metal ions existence.Herein we report a new ion pair induced mechanism for selectively extracting Li^(+)from acidic chloride solutions by tributyl phosphate(TBP).It is shown that the acidity and the chloride ions in the aqueous phase have great effects on the extraction of Li^(+).The FT-IR,UV-Vis and ESI-MS experiments provide solid evidence for the formation of ion-pair complex[Li(TBP)_n(H_(2)O)_(m)]^(+)[FeCl_(4)]^(-)(n-1,2,3;m-0,1)in the organic phase,which brings about the effective and efficient extraction of Li^(+).This mechanism can overcome the Hofmeister bias and allow for the selective extraction of Li^(+) from the extremely hydrophilic chlorides.It has also been proved that the loaded Li in TBP can be effectively stripped by concentrated HCl solution with a Li/Fe separation factor>500.The understanding of the ion-pair transport mechanism is helpful for optimizing the recovery process or further advancing more efficient recovery techniques for Li from acidic liquor.

Extraction of germanium(IV) from acid leaching solution with mixtures of P204 and TBP

Solvent extraction experiments were conducted from acidic solutions containing germanium（IV） and other metal ions, such as Ga3＋, Fe3＋, Zn2＋ and Fe2＋ in hydrometallurgical process of zinc. The purpose of this work was to enhance the efficiency of the extraction and stripping processes and the selectivity of germanium and other metals, while making the method as simple as possible. Germanium was recovered from sulfuric acid, using di-（2-ethylhexyl） phosphoric acid （P2O4） as an extractant, tributyl phosphate （TBP） as modifier diluted in sulfonate kerosene and stripped by NaOH aqueous solution. Extraction studies were carried out under different acid concentrations and solvent concentrations, and optimized conditions were determined. The numbers of stages required for extraction and stripping of metal ions were determined from the McCabe-Thiele plot. The results show that the extracting and stripping efficiencies are 94.3% and 100%, respectively, through two-stage extraction and two-stage strip. Moreover, the synergistic effect of TBP on the system P2O4/kerosense/Ge4＋ is revealed with respect to the extraction of germanium.

Extraction of Aminobenzoic Acid with TOA and TBP

A series of extraction equilibrium experiments for aminobenzoic acid were carried out. Tri n octylamine (TOA) and tributyl phosphate (TBP) were selected as complexing agents. 1 Octanol and kerosene were selected as diluents. The effects of extractant concentration and pH on the distribution ratio were discussed in detail. It was found that there are ion pair association and hydrogen bond complexing in the extraction. Expressions of the equilibrium distribution for different solvent systems are proposed. The precision of the models is satisfactoy.