KINETICS OF PHENOL EXTRACTION FROM AQUEOUS PHASE BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

The kinetics of the extraction of phenol from the aqueous phase by sulfuric acid salts of trioctylamine (TOA salts) in kerosene and the stripping of phenol from the organic phase by sodium hydroxide solution were studied using a constant interfacial area cell. Measurements of the extraction and stripping rates were made by measuring the time-dependent phenol concentrations in the aqueous phase. It is found that the extraction rate of phenol is strongly dependent on the initial concentration of phenol in the aqueous phase and on the initial concentration of TOA salts in the organic solvent. However, the effect of the total sulfate concentration and the acidic concentration on the extraction rate are not significant. The stripping rate is only a function of the initial concentration of phenol in the TOA salt-organic phase. By analyzing the experimental data, it was recognized that the extraction of phenol occurs at the interface, rather than in the bulk of the solution. The diffusion resistance, rather than the resistance of chemical reaction, is the rate-controlling step for the phenol extraction. Based on the experimental data, simple expressions of the extraction rate and stripping rate of phenol were obtained.     

Extraction of Platinum(IV) with Trioctylamine and its Application to Liquid Membrane Transport

Abstract

The extraction and stripping behavior of platinum(IV) between trioctylamine (TOA) in kerosene and different aqueous media has been investigated. Perchlorate anion was found to be most effective for the stripping of platinum under acidic and neutral conditions. The transport of platinum was performed through a supported liquid membrane (SLM) impregnated with TOA as a mobile carrier. Platinum was almost quantitatively transported from the hydrochloric acid solution to the stripping solutions containing perchlorate anion against its large concentration gradient without accumulation in the liquid membrane layer. The transport behavior of platinum was greatly improved by the addition of 1-octanol in SLM, and the permeation rate was mainly controlled by diffusion in the aqueous boundary layer.     

EXTRACTION EQUILIBRIUM OF PHENOL BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

An investigation was undertaken involving the extraction equilibrium of phenol from an aqueous solution using trioctylamine sulfate salt (TOA salt)/trioctylamine (TOA) as the extractant. The purpose of using trioctylamine as the organic solvent is to increase the total capability of phenol extraction as well as to avoid the use of other organic solvents. In order to prevent the formation of a second phase from the reaction of trioctylamine and sulfuric acid, 1-octanol in an appropriate amount was added to make the organic solution homogeneous. Equilibrium distribution coefficients (K_d) in the extraction of phenol by TOA salt/TOA were measured for various operating conditions. The equilibrium distribution coefficient of phenol (K_d) between two phases decreased with increasing the initial concentration of phenol, thereby decreasing the initial concentration of sulfuric acid, and subsequently increasing the volume ratio of aqueous phase to organic phase. We recommended that the extraction is carried out at low temperature. A higher value of K_d up to 800 was obtained in using trioctylamine sulfate/trioctylamine as the extractant for equal volume ratio of aqueous phase to organic phase.     

EXTRACTION MECHANISM OF PHENOL BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

In the present study, the extraction mechanism of phenol from an aqueous solution by sulfuric acid salts of trioctylamine (TOA salts) was investigated. Based on the experimental evidence that the affinity of sulfuric acid and amine is greater than that of phenol and amine, the procedure of the extraction mechanism is assumed to involve two independent steps, i.e., trioctylamine (TOA) is first reacted with sulfuric acid to form TOA salts and phenol is extracted from the aqueous phase by TOA salts. The Wilson model, which accounts for the reaction of trioctylamine and sulfuric acid to form different kinds of TOA-salts, is employed to predict the extraction of phenol in the present study. The number of water molecules in the neighborhood of the different TOA-salts, which directly reflects the extraction capability of phenol, was determined. This prediction from the Wilson model is fairly consistent with the experimental data.     

MODEL OF CHEMICAL REACTION EQUILIBRIUM OF SULFURIC ACID SALTS OF TRIOCTYLAMINE

The chemical reaction of trioctylamine (TOA) and sulfuric acid in organic solvent/aqueous solution was carried out. TOA salt products of various kinds were obtained based on different conditions of operation and organic solvents. An equilibrium model, based on the chemical reaction of sulfuric acid and trioctylamine, is proposed. The equilibrium constants of various reactions of trioctylamine and sulfuric acid were searched by means of the modified LETAGROP-DISTR computer program, from which the sum of the least-square error of the extraction of sulfuric acid per unit concentration of TOA salts was minimized. The corresponding concentration profiles of the various main products as a function of the activity of sulfuric acid in the aqueous solution were also obtained. The activity coefficient of the sulfuric acid in the aqueous phase and the density of the aqueous solution of sulfuric acid were considered in order to evaluate the activity of the sulfuric acid in the aqueous solution more accurately. The results obtained from the proposed model are consistent with that of Wilson's published model.     

磷酸三丁酯/煤油支撑液膜体系中苯酚的传质分离

研究了苯酚在以多孔聚丙烯平板膜(Celgard2500)为支撑体、磷酸三丁酯(TBP)为膜载体和煤油为膜溶剂的支撑液膜体系中的传质过程;用传统萃取法测定了TBP/煤油体系中苯酚络合物摩尔比为1∶1,同时得到25.0℃萃取平衡常数为96.72;考察了原料相pH值、初始质量浓度、膜二侧转速、载体浓度和反萃取相碱浓度对苯酚传质的影响,确定了该体系分离苯酚的最佳条件:原料相pH<9,苯酚初始质量浓度<1 000 mg/L,膜二侧转速>300 r/m in,载体浓度为0.55 mol/L,反萃取相碱浓度0.10 mol/L;根据双膜理论提出苯酚的传质动力学方程,采用直线斜率法计算了苯酚在TBP/煤油支撑液膜体系中的扩散层厚度和膜内扩散系数,计算结果表明动力学方程计算值能较好地与实验值吻合,平均相对误差在2%以内。     

Performance of hollow fiber supported liquid membrane on the extraction of mercury(II) ions

The extraction and recovery or stripping of mercury ions from chloride media using microporous hydrophobic hollow fiber supported liquid membranes (HFSLM) has been studied. Tri-n-octylamine (TOA) dissolved in kerosene was used as an extractant. Sodium hydroxide was used as a stripping solution. The transport system was studied as a function of several variables: the concentration of hydrochloric acid in the feed solution, the concentration of TOA in the liquid membrane, the concentration of sodium hydroxide in the stripping solution, the concentration of mercury ions in the feed solution and the flow rates of both feed and stripping solutions. The results indicated that the maximum percentages of the extraction and recovery of mercury ions of 100% and 97% were achieved at the concentration of hydrochloric acid in the feed solution of 0.1 mol/l, the concentration of TOA at 3% v/v, the concentration of sodium hydroxide at 0.5 mol/l and the flow rates of the feed and stripping solutions of 100 ml/min. However, the concentration of mercury ions from 1–100 ppm in the feed solution had no effect on the percentages of extraction and recovery of mercury ions. Thus, these results have identified that the hollow fiber supported liquid membrane process has high efficiency on both the extraction and recovery of mercury (II) ions. Moreover, the mass transfer coefficients of the aqueous phase (k _i ) and membrane or organic phase (k _m ) were calculated. The mass transfer coefficients of the aqueous phase and organic phase are 0.42 and 1.67 cm/s, respectively. The mass transfer coefficient of the organic phase is higher than that of the aqueous phase. Therefore, the mass transfer controlling step is the diffusion of the mercury ions through the film layer between the feed solution and the liquid membrane.     

复合体系下磷酸和硫酸的萃取动力学

为了深入了解萃取过程的机理和动力学特征,采用了恒界面池法研究了复合体系下磷酸和硫酸的萃取动力学,分别考察了比界面积、初始水相中磷酸浓度、初始水相中硫酸浓度对磷酸、硫酸萃取速率的影响,并提出了60℃下硫酸-磷酸复合体系中萃取磷酸和硫酸的动力学方程。实验结果表明:磷酸和硫酸的萃取速率随着比界面积增大而减小,随着初始水相中磷酸浓度的升高而逐步增加;初始水相中硫酸浓度的增大也有利于提高磷酸和硫酸的萃取速率。并研究了在60℃硫酸-磷酸复合体系中,磷酸和硫酸的萃取动力学方程,并用工业原料磷酸对萃取动力学进行了验证,表明拟合所得的方程计算的磷酸和硫酸萃取速率和实际测得的值相近。     

Transport of Palladium(II) through Trioctylamine Liquid Membrane

Abstract

The permeation behavior of palladium(II) through a supported liquid membrane (SLM) impregnated with trioctylamine (TOA) in kerosene has been investigated. By selecting perchloric or nitric acid as a stripping agent, Pd(II) was transported through the SLM containing 0.5 M TOA and 20% 1-octanol without remaining in the liquid membrane. The permeation rate (k _{f. obs}) of Pd(II) for HNO₃ was faster than that for HClO₄. Palladium(II) was concentrated across the SLM from the 0.5 M CHI solution into the HClO₄ or HNO₃ solution.     

Back Extraction of HCl from TOA Dissolved in N-Octanol by Aqueous Ammonia in a Microchannel Device

To recover the extractant in the preparation of KH₂PO₄ using the extraction method, studies for the back extraction of HCl by aqueous ammonia from TOA (trioctylamine) dissolved in n-octanol were conducted. First, the reaction of HCl back extraction from TOA in n-octanol with aqueous ammonia was examined in shaking flasks and the equilibrium of this reaction was validated. The equilibrium constant of the stripping reaction was determined in the temperature range of 297.7-318.2 K and the reaction enthalpy was found to be -17.8 kJ/mol indicating that the stripping reaction was exothermic. Then kinetic experiments were performed in a microchannel device with the elimination of mass transfer limitations, as demonstrated by the experimental results. A kinetic model was established to obtain the forward and backward interfacial reaction rate constants with the help of the obtained equilibrium constant of the stripping reaction. This model described the measured data well and predicted correctly the change of HCl concentration in the oil phase along with the residence time in our experiments. Furthermore, the activation energy for the forward (8.21 kJ/mol) and backward (26.0 kJ/mol) reaction was determined and subsequently the forward and backward interfacial reaction rate constants were determined in the temperature range of 298.7-313.2 K.     

Extraction and separation of HCl and Rh(III) with trioctylamine

In this paper the use of trioctylamine (TOA) to extract HCl from Rh(III)-containing solutions generated by a supported liquid membrane (SLM) process is investigated. TOA was found to extract HCl readily (in a single contact of 3 min duration) at a molar ratio [HCl]/[TOA] equal to one. For each mole of HCl extracted an equivalent amount of H₂O was found to be extracted as well. As far as Rh(III) extraction of TOA is concerned this was found to depend on the age of the solution and the Cl⁻ concentration. Prolonged aging (accelerated by heating) or [Cl⁻]⩾3 M was found to completely suppress the extraction of Rh(III) by TOA. The chloride ion concentration effect was attrib-uted to Le Chatelier's principle while the aging effect was attributed to the aquation/conversion of the extractable RhCl₆³⁻ complexes to RhCl₅(H₂O)²⁻. The aquation reaction was studied with UV–Visible spectroscopy in an effort to substantiate the solvent extraction (SX) results. On the basis of the findings of this work a combined SLM/SX process flowsheet is proposed according to which the Rh(III) and HCl co-transported through the supported liquid membrane are co-extracted by TOA and subsequently separated by differential stripping; Rh(III) with 0·5 M HCl/3 M Cl⁻ medium and HCl with NAOH.     

Separation of Zinc Ions from an Acidic Mine Drainage using a Stirred Transfer Cell–Type Emulsion Liquid Membrane Contactor

Abstract

This is a report on the separation and recovery of zinc ions from an acidic mine drainage using a stirred transfer cell‐type emulsion liquid membrane contactor. Di(2‐ethylhexyl) phosphoric acid was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. A study was made of the effect on the extraction extent and initial extraction rate of the following variables: pH and initial metal concentration of the feed phase, carrier content in the organic solution, a stripping agent concentration in the receiving phase, and stirring speed in the transfer cell. The content of sulfuric acid as a stripping agent did not show in the studied range any significant influence on metal permeation through the SLM, although a minimum hydrogen ion concentration of 100 g/L is suggested in the internal aqueous solution to ensure an acidity gradient between both aqueous phases to promote the permeation of metal ions toward the strip liquor. Results show that using a pH of 4.0 in the feed acid solution, a concentration of 3% w/w_o of phosphoric carrier in the organic phase and a H₂SO₄ content of 100 g/L in the strip liquor, the extent and rate of extraction through the liquid membrane can be highly favored, pointing to the potential of this method for extracting heavy metals from many kinds of dilute aqueous solutions.     

Equilibrium and kinetic studies on the extraction and stripping of uranium(VI) from nitric acid medium into tri-phenylphosphine oxide using a single drop column technique

Equilibrium and kinetic studies have been carried out on the extraction of uranium(VI) from aqueous nitrate medium into tri-phenylphosphine oxide (TPPO). It was found that uranium extraction by TPPO was suitable in toluene as diluent than cyclohexane and chloroform. Kinetic studies were carried out using a single drop column method. Reaction orders were determined with respect to uranium and nitric acid concentrations in the aqueous phase and TPPO concentrations in the organic phase. It was found that the extraction kinetics could be explained in terms of an aqueous phase interfacial reaction accompanied by diffusion through the interface. Sodium hydroxide solution is suitable for stripping uranium from TPPO in toluene.     

Separation of Precious Metals through a Trioctylamine Liquid Membrane

Abstract

The extraction behavior of precious metals (PMs) from HCl media has been studied using trioctylamine (TOA) in kerosene. The extraction sequence of PMs was found to be Au(III) > Pd(II), Pt(IV), Ir(IV) > Ir(III). Ru. Transport of PMs was performed through a supported liquid membrane (SLM) impregnated with TOA as a mobile carrier from the HCl feed solution into the HClO₄ or HNO₃ product solution. Selective transport; and recovery of PMs from certain mixtures were accomplished across the TOA-SLM on the basis of differences in extraction equilibria and kinetics.     

Iridium(IV) Transport across Trioctylamine Supported Liquid Membrane

Abstract

Transport behavior of iridium through a supported liquid membrane (SLM) was investigated using trioctylamine (TOA) as a mobile carrier. Iridium(IV) was almost quantitatively extracted with TOA in kerosene from a low HCl solution, and extracted Ir(IV) was stripped with an HClO₄ or HNO₃ solution. Based on the extraction and stripping data, transport of Ir(IV) through a TOA-SLM was performed. Iridium(IV) in the feed solution with low HCl concentration was effectively transported into the HClO₄ or the HNO₃ product solution. Iridium(IV) was recovered and concentrated in the 1 M HClO₄ product solution by reducing the volume of strip solution relative to the volume of feed solution, yielding a sufficient enrichment factor.     

Extraction and pertraction of phenol through bulk liquid membranes

The extraction and pertraction of phenol through a bulk liquid membrane (BLM) with Cyanex^® 923, Amberlite^® LA‐2 and trioctylamine (TOA) as carriers were studied. Cyanex^® 923 was selected as the best carrier for pertraction. The distribution coefficient of phenol for solvents with carrier and pure n‐alkanes, the individual mass‐transfer coefficient at the extraction interface and the initial flux of phenol through the extraction interface (J_Fo) decreased in the order: Cyanex^® 923 > Amberlite^® LA‐2 > TOA ? pure n‐alkanes. The opposite order was observed for the value of the mass‐transfer coefficient in BLM and the maximum flux of phenol through the stripping interface (J_Rmax). At constant driving forces the maximum fluxes through the extraction and stripping interfaces were similar when amine carriers were used. However, J_Rmax was lower than J_Fo for Cyanex^® 923. Although the kinetics of stripping was the rate‐determining step, the flux of phenol was significantly higher than in pertraction with amine carriers. The adsorption of the carrier at aqueous phase/membrane interfaces was probably responsible for the rapid and slow transfer of phenol through the extraction and stripping interface, respectively. Copyright © 2004 Society of Chemical Industry     

Selective Transport of Bismuth Ions through Supported Liquid Membrane

A new supported liquid membrane (SLM) system was prepared for the selective transport of bismuth ions from the aqueous feed into the aqueous permeate phase. The support of the SLM was a thin porous polypropylene or polyvinylidene fluoride membrane impregnated with diisooctyldithiophosphinic acid (Cyanex 301) as mobile carrier in 4‐chloroacetophenon as organic solvent. Cyanex 301 acts as a highly selective carrier for the uphill transport of bismuth ions through the SLM. In the presence of HNO₃ as a metal ion acceptor in the strip solution, the transport of bismuth ions into the strip side reached 70 % of the initial feed concentration after 3.5 hours. The selectivity and efficiency of bismuth transport from aqueous solutions containing different mixtures of cations were investigated. In the presence of P₂O₇^2– ions as suitable masking agent in the feed solution, the interfering effects of other cations were completely eliminated. The selective transport of bismuth through SLM is superior to liquid‐liquid extraction or through bulk liquid membranes. This is due to the high efficiency. The SLM reduces the solvent requirements, combines extraction and stripping operations in a single process and allows the use of highly selective extractants. The system may be applied to samples containing very low bismuth concentrations.     

Effect of ph on the extraction characteristics of succinic acid and the stability of colloidal liquid aphrons

Predispersed solvent extraction (PDSE) by colloidal liquid aphrons (CLAs) was used for the extraction of succinic acid from aqueous solution. The loading values for succinic acid in PDSE by CLAs increased with increasing pH values in aqueous phase. This was due to increasing of the concentration of the undissociated succinic acid. The extractability of PDSE was higher than that of conventional contacting type extraction because of the interaction between factant and acid molecule. The stability of CLAs increased with increasing of the pH values in aqueous phase and decreasing of trioctylamine (TOA) concentration in organic phase. However, the structure of CLAs was stable at all the pH range except very low pH condition. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University.     

Extraction of Chloride Ions from Zinc-Bearing Waste Lixivium by Trioctyl Amine (TOA)

This paper presents research on separating Cl^? from zinc-bearing waste lixivium by using trioctylamine as an extractant, 2-octanol as a solvent, and sulfonated kerosene as a diluent. The effects of trioctylamine concentration, organic/aqueous phase ratio, extracting stages, and waste lixivium pH were investigated, and the process of stripping was also discussed. The optimal conditions were achieved. The extraction efficiency, separation factor, and stripping efficiency were calculated with optimal values of 99.47%, 595, and 99.99%, respectively. Besides, the extractant regenerated after stripping was observed without the emulsifying phenomenon. The mechanism of extraction and stripping was also discussed.     

Cobalt removal from waste‐water by means of supported liquid membranes

BACKGROUND: Supported liquid membranes (SLM) are an alternative technique to remove and recover metals from diluted process solutions and waste‐water. In the present work, the removal of Co(II) from a synthetic CoSO₄ solution containing initial amounts of cobalt(II) in the range 100–200 ppm (0.1–0.2 g dm^?3) has been studied on a pilot scale. By performing batch equilibrium experiments, the optimal settings, i.e. the composition of the organic phase, the pH of the feed, the type and concentration of the stripping agent were determined. RESULTS: It is shown that the equilibrium characteristics of a synergistic extractant mixture containing di‐2‐ethyl‐hexylphosphoric acid (D2EHPA) and 5‐dodecylsalicylaldoxime (LIX 860‐I) are superior to D2EHPA. Both hydrochloric acid and sulfuric acid have been evaluated as stripping solutions in liquid–liquid extraction tests and as the receiving phase in a SLM configuration. Although equilibrium tests showed no difference in stripping characteristics between both chemicals, it was observed that in a SLM configuration the stability of the system when hydrochloric acid is used is poor. With a commercially available SLM module (Liqui‐Cel Extra‐Flow 4 × 28) having a surface area of 19 m², a steady Co(II) flux of 0.140 gm^?2h^?1 has been obtained at influent concentrations of cobalt between 100 and 200 ppm with 3 mol dm^?3 sulfuric acid as stripping phase. CONCLUSIONS: The results obtained show that a supported liquid membrane containing a synergistic mixture of LIX 860‐I and D2EHPA gives the possibility of recovering cobalt from dilute solutions. Copyright © 2008 Society of Chemical Industry