Tri-n-butyl Phosphate Concentration Research Articles

The occurrence and removal of organophosphate ester flame retardants/plasticizers in a municipal wastewater treatment plant in the Pearl River Delta, China

The occurrence, distribution and main removal pathway of seven widely used organophosphate esters (OPs) in a municipal wastewater treatment plant (WWTP) located in the Pearl River Delta were investigated. Their daily discharge load into the Pearl River via effluent was also estimated. All the target analytes were detected in wastewater, suspended particle and dewatered sludge, with tri-n-butyl phosphate (TBP) and tris(2-butoxyethyl) phosphate (TBEP) as the main components. The total concentrations of TBP and TBEP were 21271.8 ng L−1 and 4349.4 ng L−1, 3105.1 ng L−1 and 494.5 ng L−1 in influent wastewater and final effluent, respectively. These results indicated that non-chlorinated OPs were removed efficiently in the WWTP, while chlorinated OPs passed through the WWTP unchanged due to their resistance to current wastewater treatment technology. Approximate 91.4 g of non-chlorinated OPs and 23.4 g of chlorinated OPs per day were discharged into the Pearl River via effluent, 2.4 g of non-chlorinated OPs and 0.6 g of chlorinated OPs entered the environment following sludge disposal.

Kinetics of Lithium Extraction with Tri-n-butyl Phosphate from Salt Lake Brine by a Single Drop Method

Abstract The recovery of lithium resources from salt lake brine has become more and more important. Tri-n-butyl phosphate (TBP) is the most common extractant and has good ability to selectively extract lithium, thus, basic research on it should be carried out. In this study, the kinetics of lithium extraction by TBP in salt lake brine was investigated at 298.15 K via a single rising drop technique. Parameters affecting the mass transfer mechanism, including the interfacial area, lithium concentration, iron concentration, TBP concentration, and temperature were studied. According to this research, we found that the process of extraction is controlled by the diffusion and the chemical reaction occurs at the interfacial area. The mechanism of the lithium extraction with TBP is revealed.

Computational study of molecular structure and self-association of tri-n-butyl phosphates in n-dodecane.

Tri-n-butyl phosphate (TBP) is an important extractant used in the solvent extraction process for recovering uranium and plutonium from used nuclear fuel. An atomistic molecular dynamics study was used to understand the fundamental molecular-level behavior of extracting agents in solution. Atomistic parametrization was carried out using the AMBER force field to model the TBP molecule and n-dodecane molecule, a commonly used organic solvent. Validation of the optimized force field was accomplished through various thermophysical properties of pure TBP and pure n-dodecane in the bulk liquid phase. The mass density, dipole moment, self-diffusion coefficient, and heat of vaporization were calculated from our simulations and compared favorably with experimental values. The molecular structure of TBPs in n-dodecane at a dilute TBP concentration was examined based on radial distribution functions. 1D and 2D potential mean force studies were carried out to establish the criteria for identifying TBP aggregates. The dimerization constant of TBP in the TBP/n-dodecane mixture was also obtained and matched the experimental value.

Compositional Characterization of Organic Phases after the Phase Splitting in the Extraction of Th(NO3)4 by 1.1 M Tri-n-butyl phosphate/n-Alkane

Third phase formation in the extraction of Th(IV) by 1.1 M solutions of tri-n-butyl phosphate (TBP) in n-decane and n-hexadecane from Th(NO3)4 solution in 1 M HNO3 has been investigated as a function of equilibrium aqueous phase Th(IV) concentration ([Th(IV)]aq,eq) to estimate the concentrations of Th(NO3)4, HNO3, and TBP in the third phase (TP) and the diluent-rich phase (DP). In this connection, new methods for the estimation of TBP in the organic phases after the phase splitting have been developed by exploiting the linear relationships of the density and refractive index of the solvent, the limiting organic concentration (LOC) for the third phase formation in the extraction of Th(IV) from solution with near-zero free acidity with TBP concentration in the solvent. TBP concentrations estimated by the above-mentioned methods have been validated by nitric acid (8 M) equilibration method. Experimental values for the concentration of TBP in the TP and DP for 1.1 M TBP/n-alkane–Th(NO3)4/1 M HNO3 systems have been compared with the values computed based on a model proposed earlier. In addition, the density of organic phases and the ratio of the volume of the DP to that of the TP have been measured for the above-mentioned systems as a function of [Th(IV)]aq,eq at 303 K.

Extraction of rare earth ions by tri-n-butylphosphate/phosphonium ionic liquids and the feasibility of recovery by direct electrodeposition

As the preliminary experiments for development of the recycling process to recovery of rare earths (REs) composed of Nd–Fe–B magnets by direct electrodeposition from an organic phase after extraction procedures, solvent extraction of RE such as Pr, Nd and Dy by tri-n-butylphosphate (TBP) with ionic liquids (ILs) were performed. Triethyl-pentyl-phosphonium bis(trifluoromethyl-sulfonyl)amide ([P2225][TFSA]), which is beneficial as an electrolyte for electrodeposition of electrochemically negative metals such as REs were employed as the IL. It was revealed that the extraction performance of RE(III) was enhanced significantly in TBP with [P2225][TFSA] when extraction of RE ions was carried out from an aqueous phase including TFSA− anions. Considering that the extraction mechanism was supposed to the cation-exchange of the IL with solvating the RE3+ cations by TFSA− anions, the mechanism was investigated by variation of concentrations of TBP, TFSA− anions in the aqueous phase and [P2225][TFSA]. As the results, the stoichiometry of both TBP and TFSA− anions in this IL extraction system with RE(III) was determined to be 3:1. According to UV–Vis–NIR spectroscopic analysis, the complexation of RE(III) extracted by TBP with [P2225][TFSA] was altered due to the coordination of TBP to RE(III). Estimation of the number of the TFSA− anion solvated to the centered Nd3+ cation in TBP with [P2225][TFSA] by Raman spectroscopy resulted in the centered Nd3+ cation solvated by three TFSA− anions and this result was consistent with the extraction mechanism analysis. From the electrochemical analysis, the extracted [Nd(TBP)3]3+ complex in TBP/[P2225][TFSA] was reduced to the following reaction: [Nd(TBP)3]3++3e−→Nd(0)+3TBP at −2.4V. The direct electrodeposition of the extracted [Nd(TBP)3]3+ in TBP/[P2225][TFSA] was carried out using a three-electrode system at 373K. The chemical bonding energy of Nd electrodeposits was investigated by XPS and the middle layer of electrodeposits was the metallic state, while a part of the top surface was the oxidation state.

Solvent extraction of tellurium from chloride solutions using tri-n-butyl phosphate: conditions and thermodynamic data.

The extractive separation of tellurium (IV) from hydrochloric acid media with tri-n-butyl phosphate (TBP) in kerosene was investigated. The dependence on the extraction of tellurium species, concentrations of tellurium and TBP, extraction time and stage, organic/aqueous ratio, and interferences from coexist metallic ions were examined and are discussed. Besides, the stripping agent and stripping time were also studied. It was found that the extraction reaction corresponds to the neutral complex formation mechanism and the extracted species is TeCl4 ·3TBP and that the extraction process is exothermic. The thermodynamic parameters of enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) of the extraction process were evaluated at −26.2 kJ·mol−1, −65.6 J·mol−1 ·K−1, and −7.0 kJ·mol−1, respectively at 293 K.

Tuning the Extractive Properties of Purex Solvent using Room Temperature Ionic Liquid

An Aliquat-336 based ionic liquid, namely, tri-n-octylmethylammonium bis(2-ethylhexyl)phosphate ([A3636]+[DEHP]−) was prepared and studied for the extraction of U(VI), Pu(IV), and Am(III) from nitric acid medium. Since the ionic liquid, [A336]+[DEHP]− was miscible in n-dodecane (n-DD), the extraction of these actinides in the PUREX solvent, 1.1 M tri-n-butylphosphate (TBP) in n-dodecane (n-DD), was investigated in the presence of small concentrations of ionic liquid. The distribution ratio of U(VI) and Am(III) in 0.03 M [A336]+[DEHP]−/n-DD decreased with increase in the concentration of nitric acid; whereas the extraction of Pu(IV) initially increased, it reached a maximum at 4 M nitric acid followed by the decrease. The extraction of actinides in ionic liquid medium decreased in the order Pu(IV) > U(VI) >> Am(III), indicating the feasibility of modifying the extractive properties of TBP/n-DD to favor Pu(IV) extraction. Therefore, the extraction of Pu(IV) in a solution of TBP – [A336]+[DEHP]− in n-DD was also studied. The distribution ratio of Pu(IV) increased with increase in the concentration of ionic liquid and decrease in the concentration of TBP in organic phase. The distribution ratio of Pu(IV) determined in the presence of small concentration of ionic liquid in 1.1 M TBP/n-DD was always much higher than that observed in 1.1 M TBP/n-DD. In contrast to this, the distribution ratio of U(VI) decreased by the addition of ionic liquid and Am(III) was inextractable even in the presence of ionic liquid.

Reactive Extraction of o-, m-, and p-Chlorophenol from Aqueous Solution Using Tri-n-butyl Phosphate in Kerosene

Reactive extractions of o-, m-, and p-chlorophenol (o-, m-, and p-CP) from aqueous solutions using tri-n-butyl phosphate (TBP) dissolved in kerosene were studied. The influences of equilibrium aqueous pH (pHeq) and initial TBP concentrations on distribution ratio (D) were discussed. Effective extractions of CP were observed only under pHeq lower than 7.0. D values increased with the increase of initial TBP concentration. TBP mainly reacted with the neutral form of CP by forming 1:1 (TBP:CP) complex through a hydrogen-bond between phosphoryl in TBP and hydroxyl in CP. The apparent reaction extraction equilibrium constant (K) for o-, m-, and p-CP was found in good linear relationship with the addition of dissociation constant (pKa) and the hydrophobic parameter (Log P) of CP, namely, log K = −0.1171 × pKa + 0.0680 × Log P + 2.5848, suggesting pKa plays a much more important role that affects K than Log P. Back-extraction experiments supported > 95 % CP could be recovered using 0.5 mol·L–1 NaOH as stripping ...

Equilibrium Study on Reactive Extraction of Lactic Acid with Tri-n – Butyl Phosphate in n - Hexane

Extraction of carboxylic acids from dilute aqueous solution using traditional solvents such as ketones, alcohols, ethers, and ester is inefficient because the distribution ratio is rather low. Reactive extraction which exploits reversible chemical complexation is an effective separation process for extraction of carboxylic acids from aqueous streams such as fermentation broths and wastewaters. In the extraction process, selection of the solvent is an important aspect to be considered. Considering its solubility in water, cost and availability, tri-n-butyl phosphate (TBP) seems to be an attractive solvent for the extraction of lactic acid from aqueous solution. The purpose of this experiment is to study the equilibrium of the reactive extraction of lactic acid in aqueous solution with TBP in n-hexane. The parameters studied in this experiment were initial concentration of lactic acid in the aqueous phase, TBP concentration in n-hexane phase, and the extraction temperature. The experiments at ambient temperature were carried out using a separatory funnel, while the experiments at other than ambient temperature were carried out using erlenmeyer flask and water bath shaker to adjust the temperature. In this experiment, the initial concentration of lactic acid was varied from 0.1 to 0.5 gmol/dm3. The range of initial TBP concentrations in n-hexane was 0.1 to 1.0 gmol/dm3 and the extraction temperature range was 283 to 313 K. The experimental results showed that the higher the initial concentration of lactic acid in aqueous solution, the higher the distribution ratio for a fixed TBP concentration and extraction temperature. For a fixed initial concentration of lactic acid in aqueous solution and extraction temperature, the distribution ratio of lactic acid is increased by increasing TBP concentration. The overall equilibrium constants (Kpq) for the experiments using TBP concentration ranging from 0.1 to 1.0 gmol/dm3 at the extraction temperature of 293 K are calculated to be 0.0668 to 0.5144. Kpq for the experiments at the temperature ranging from 283 to 313 K at the initial concentration of lactic acid of 0.2 gmol/L are found to be 0.0122 to 0.8856. The Kpq as a function of temperature (T) in K can be expressed as ln Kpq = 10,596/T - 38.08 with sum of square of error of 0.14.

Recovery of Golden yellow and Cibacron LSG dyes from aqueous solution by bulk liquid membrane technique

Tri-n-butyl phosphate (TBP) was used as carrier for the transport of Golden yellow and Cibacron LSG dyes through a hexane bulk liquid membrane. The transport efficiency of dyes by TBP was investigated under various experimental conditions such as pH of the feed phase (dyes solution), concentration of the receiving phase (NaOH solution), concentration of TBP in membrane, rate of stirring, effect of transport time, type of solvent, dye concentration in feed phase, effect of temperature.. The maximum transport dyes occurs at ratio of 1:1 TBP-hexane At pH 3.0 0.1 (feed phase) the transport dyes decreased. At high stirring speed (300 rpm) the dyes transport from the feed phase to the strip phase was completed within 60 minutes at <TEX>$27^{\circ}C$</TEX>. Under optimum conditions: Feed phase 100 mg/L dyes solution at pH 1.0 0.1, receiving phase 0.1 mol/L NaOH solution, membrane phase 1:1 TBP-hexane , Stirring speed 300 rpm and temperature <TEX>$27^{\circ}C$</TEX>, the proposed liquid membrane was applied to recover the textile effluent.

Rapid quantification of TBP and TBP degradation product ratios by FTIR-ATR

Tri-n-butyl phosphate (TBP) is the key complexant within the plutonium and uranium reduction extraction process used to extract uranium and plutonium from used nuclear fuel. During reprocessing TBP degrades to dibutyl phosphate (DBP), butyl acid phosphate (MBP), butanol, and phosphoric acid over time. A method for rapidly monitoring TBP degradation is needed for the support of nuclear forensics. Therefore, a Fourier transform infrared spectrometry-attenuated total reflectance (FTIR-ATR) technique was developed to determine approximate peak intensity ratios of TBP and its degradation products. The technique was developed by combining variable concentrations of TBP, DBP, and MBP to simulate TBP degradation. This method is achieved by analyzing selected peak positions and peak intensity ratios of TBP and DBP at different stages of degradation. The developed technique was tested on TBP samples degraded with nitric acid. In mock degradation samples, the 1,235 cm−1 peak position shifts to 1,220 cm−1 as the concentration of TBP decreases and DBP increases. Peak intensity ratios of TBP positions at 1,279 and 1,020 cm−1 relative to DBP positions at 909 and 1,003 cm−1 demonstrate an increasing trend as the concentration of DBP increases. The same peak intensity ratios were used to analyze DBP relative to MBP whereas a decreasing trend is seen with increasing DBP concentrations. The technique developed from this study may be used as a tool to determine TBP degradation in nuclear reprocessing via a rapid FTIR-ATR measurement without gas chromatography analysis.

Effect of tri-n-butyl phosphate on physical properties of dodecane–nitric acid system

Extraction power of solvent depends upon the physical properties of the system. Tri-n-butyl phosphate (TBP) in dodecane is a versatile solvent used in the nuclear fuel reprocessing like PUREX process. The study of physical properties like density, viscosity, interfacial tension and solubility for TBP–nitric acid–dodecane system will be helpful in carrying out different extraction studies during PUREX process. Thus, physical properties like density, viscosity, interfacial tension and solubility have been measured for TBP–nitric acid–dodecane system using pycnometer, viscometer, pendant drop method and high performance liquid chromatography respectively. It has been observed that density and viscosity increases but interfacial tension and solubility decreases with the concentration of TBP in dodecane–nitric acid system. Physical properties of 30 % TBP–nitric acid–dodecane system have also been studied in detail. All these studies will also be useful in stripping out dissolved TBP from the nuclear waste.

Reactive Extraction of o-Aminophenol with Tri-n-butyl Phosphate in Different Solvents

Tri-n-butyl phosphate (TBP) is used as the extraction agent for the extraction of o-aminophenol (OAP) in active solvents and inactive solvents. The effects of aqueous solution pH, solvents, concentration of TBP, and the initial OAP concentration on distribution coefficient (D) are investigated. Results show that the neutral OAP molecule is hydrogen-bonded to TBP effectively into the organic phase, and D was maximum when the equilibrium pH was between pKa1 and pKa2. The extraction efficiency is TBP–1-octanol > TBP–kerosene > TBP–carbon tetrachloride > TBP–chloroform, when the concentration of TBP is between (0.3632 and 0.7264) mol·L–1, while the result is TBP–kerosene > TBP–1-octanol > TBP–carbon-tetrachloride > TBP–chloroform when the concentration increases [(1.0896 to 1.8159) mol·dm–3]. Fourier transform infrared spectroscopic analysis shows that the extractive behavior is controlled by hydrogen bonding. An expression for equilibrium D is proposed, and the parameters of the apparent extraction equilibri...

Equilibrium Study for the System Tri-n-butyl Phosphate, Normal Paraffin Hydrocarbon, and Nitric Acid

Tri-n-butyl phosphate (TBP) in diluent is generally used as a solvent for the extraction of fissile materials in the reprocessing of spent fuels by the PUREX process. The mutual solubility of TBP and water leads to the transfer of some finite amount of TBP into the aqueous phase. The distribution study of TBP between normal paraffin hydrocarbon (NPH) and nitric acid has been studied. Equilibrium curves have been generated for TBP in different concentrations of nitric acid and NPH. The distribution coefficient (Kd) is also calculated by measuring the concentration of associated TBP in the aqueous and organic phase. The effect of an inert diluent on the solubility of TBP in nitric acid is also studied. It has been found that the distribution coefficient value varies with the concentration of TBP, nitric acid, and NPH. Nitric acid partitioning between TBP and water has also been studied. The concentration of nitric acid in both phases was determined by the titration method. It has also been proven that the c...

Extraction studies of trivalent ions from TALSPEAK medium using phsophonic acid-TBP solvent mixture

Indigenously synthesized extractant, phenyl (octyl) phosphonic acid (POPA) in tri-n-butylphosphate (TBP) and dodecane, has been investigated for the separation of americium from trivalent lanthanides in nitric acid medium as well as diethylene triaminepentaacetic acid (DTPA) and lactic acid mixture (TALSPEAK medium). Various experimental parameters like concentration of DTPA, lactic acid, TBP, nitrate ions and pH of the aqueous feed solution have been optimized to obtain the highest separation factor between americium and europium. Bulk actinide–lanthanide separation reagent, tetra (ethylhexyl) diglycolamide (TEHDGA), was equilibrated with simulated solution of americium and lanthanides, equivalent in concentration to the reprocessing waste originating from PHWR spent fuel. DTPA/lactic acid mixture was used to strip the metal ions from the loaded organic phase and re-extracted into POPA in TBP/dodecane to evaluate the separation factor of individual lanthanides with respect to americium. Very good separation factors between americium and trivalent lanthanides were obtained.

Extraction and third phase formation behavior of Eu(III) IN CMPO–TBP extractants present in room temperature ionic liquid

The extraction behavior of europium(III) from nitric acid medium by a solution of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tri-n-butylphosphate (TBP) in the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (bmimNTf2), was studied. The distribution ratio (DEu) of Eu(III) in CMPO–TBP/bmimNTf2 was measured as a function of various parameters such as the concentrations of nitric acid, europium, CMPO, and TBP and temperature. The distribution ratio of europium increases with the increase in the concentration of nitric acid reaches a maximum value around 1M followed by decrease. Loading of europium in CMPO–TBP/bmimNTf2 increases with the increase in Eu(III) concentration without leading to the formation of third phase, which is usually observed in conventional diluents. The stoichiometry of metal–solvate in organic phase varies from 1:3 (Eu:CMPO) at trace levels to 1:1 at higher europium loadings. The viscosity of the TBP–CMPO/bmimNTf2 system at various temperatures and the enthalpy change accompanied by the extraction of europium(III) were determined and reported in this paper.

Extraction of americium(III) from nitric acid medium by CMPO-TBP extractants in ionic liquid diluent

Extraction of americium(III) from nitric acid medium by a solution of tri-n-butylphosphate (TBP) and n-oc-tyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (bmimNTf 2 ), was studied and the results were compared with that obtained with CMPO-TBP in n-doddecane (n-DD). The distribution ratio of 241 Am(III) in TBP-CMPO/bmimNTf 2 was measured as a function of various parameters such as concentrations of nitric acid, CMPO, bmimNO 3 , NaN0 3 and TBP and temperature. Remarkably large distribution ratios were observed for the extraction of americium(III) when bmimNTf 2 acted as diluent and the extraction was insignificant in the absence of CMPO. The stoichiometry of metal―solvate in organic phase was determined by the slope analysis of extraction data and it indicated the formation of 1: 3 (Am: CMPO) complex in organic phase. Viscosity of TBP-CMPO/bmimNTf 2 at various temperatures and enthalpy change accompanied by the extraction of americium(III) were determined and reported in this paper.

Use of bulk liquid membrane for the removal of chromium (VI) from aqueous acidic solution with tri-n-butyl phosphate as a carrier

Tri-n-butyl phosphate (TBP) was used as carrier for the transport of chromium (VI) through a hexane bulk liquid membrane. The transport efficiency of chromium (VI) by TBP was investigated under various experimental conditions such as pH of the feed phase (Cr (VI) solution), concentration of the receiving phase (NaOH solution), concentration of TBP in membrane, rate of stirring, effect of transport time, type of solvent, Cr (VI) concentration in feed phase, and effect of temperature. The transport efficiency increased with increasing carrier concentration from 7.5 × 10 − 2 to 2.25 × 10 − 1 mol/L. At high pH (donor phase) the transport rate of chromate ions decreased. At high stirring speed (300 rpm) the Cr (VI) transport from the feed phase to the strip phase was completed within 5 h at 27 °C. Under optimum conditions: donor phase 4.8 × 10 − 4 mol/L K 2Cr 2O 7 solution at pH 1.0 ± 0.1, acceptor phase 1.0 mol/L NaOH solution, membrane phase 2.25 × 10 − 1 mol/L, stirring speed 300 rpm, and temperature 27 °C, the flux rate was found to be 2.90 × 10 − 7 mol/m 2 s.

Parameters Influencing Third‐Phase Formation in the Extraction of Th(NO3)4 by some Trialkyl Phosphates

Third‐phase formation in the extraction of Th(IV) by trialkyl phosphates (TalP) such as tri‐n‐butyl phosphate (TBP), tri‐iso‐butyl phosphate (TiBP), tri‐sec‐butyl phosphate (TsBP), tri‐n‐amyl phosphate (TAP), tri‐2‐methylbutyl phosphate (T2MBP), tri‐iso‐amyl phosphate (TiAP), tri‐sec‐amyl phosphate (TsAP), and tri‐cyclo‐amyl phosphate (TcyAP) has been investigated under various conditions. Formation of a third phase in the extraction of Th(IV) by TBP/n‐dodecane as a function of TBP concentration at 303 K was studied. Measurements were also carried out on the extraction of Th(IV) from its solution with near‐zero free acidity by various phosphate/diluent binary solutions (1.1 M) as a function of temperature. Third‐phase formation in the extraction of Th(IV) by 1.1 M TalP in various diluents from nitric acid media has also been studied as a function of equilibrium aqueous‐phase acidity at 303 K. Empirical equations to predict limiting organic concentration with respect to various parameters for third‐phase formation in the extraction of Th(IV) by TBP and TAP from nitric acid media have been derived. Some of the above phosphates have been investigated for the distribution of Th(NO3)4 between the “diluent‐rich phase” (DP) and “third‐phase” (TP) in the extraction of Th(IV) by 1.1 M TalP in various diluents from its saturated solution with near‐zero free acidity at 303 K. Results of the above studies are presented in this paper. Based on these studies, the effects of extractant concentration, the temperature, the nature of the diluent, the equilibrium aqueous‐phase acidity, and the structure of the extractant on third‐phase formation behavior of trialkyl phosphates are described in this paper.

Solvent Extraction of Chromium(VI) with Tri-n-butyl Phosphate from Aqueous Acidic Solutions

The solvent extraction of Cr(VI) from aqueous acidic solutions by tri-n-butyl phosphate (TBP) in kerosene was investigated. HCl, H2SO4, and H3PO4 were used for the pH adjustment of the aqueous phase. The results show that the distribution coefficient exhibited a maximum when HCl was used. The distribution coefficient increased with increasing TBP concentration (from (0.2 to 3.0) mol·L-1) and decreasing pH (from 2.0 to 0). The results also show that one molecule of Cr(VI) was approximately coordinated to three TBPs in the complex. The enthalpy change of −17.4 kJ·mol-1 was determined using the van't Hoff equation, suggesting that the extraction of Cr(VI) from a HCl medium is an exothermic process. The presence of NaCl in the feed phase improved the extraction efficiency, whereas the presence of Na2SO4 or KH2PO4 has no benefit. The stripping of loaded organic and the reuse of the extractant are also discussed in this paper.