Consecutive Irreversible First-order Reactions Research Articles

Separation and purification of polyprenols from Ginkgo biloba L. leaves by bulk ionic liquid membrane and optimizing parameters

Polyprenols extracted from Ginkgo biloba L. leaves (GBL) are known for their biological functions (antioxidant, antimicrobial, antivirus, hepatoprotective, and antitumor properties). Nevertheless, the conventional methods of polyprenol separation lack selectivity and has a low separation efficiency. As a result, effective methods for separating and purifying polyprenols have become a major research focus in the pharmaceutical and healthy food industries. In this study, the separation and purification of GBL’s polyprenols were performed. The transport of polyprenols from GBL via a bulk liquid membrane containing AgBF4 as a carrier was examined. The optimization parameters were: 1-hexene, 308 K, 500 rpm, 1% wt %, 72 h for the stripping phase, system temperature, stirring speed, the carrier concentration in membrane phase, and transport time, respectively. Additionally, the purity of polyprenols increased from 48.2% to 78.1%, recovery was 73.5 %, and a permeability coefficient of 0.24 cm/h was obtained under these conditions. The kinetic parameters (k1, k2, tmax, Rlmax, Jfmax, Jsmax) at 308 K were determined for the interface reactions assuming two consecutive irreversible first-order reactions as: 2.36 × 10−2, 0.87 × 10−2 (h−1), 68.64 (h), 0.57, −0.47 × 10−2 (h−1) and 0.47 × 10−2 (h−1), respectively. These values indicated that the polyprenols' transport process combines two processes: complex diffusion in the membrane phase and chemical reactions at two independent and possibly different interfaces. The experiments demonstrated that the bulk liquid membrane system significantly affected the separation and enrichment of polyprenols. The study provided an effective polyprenol separation and purification approach, and the basis for potential polyprenol-based medications, cosmetics, and health products.

Kinetics of facilitated transport of Zn(II) from leach liquor of spent LTS catalyst across bulk liquid membrane

A kinetic study on facilitated transport of Zn(II) from leach liquor of spent low-temperature shift catalyst (LTS) has been investigated. Primarily, the hydrometallurgical leaching of Zn and Cu from the spent LTS catalyst was performed. Moreover, the selective transport of Zn from leach liquor was facilitated by bis (2-ethylhexyl) phosphate (HDEHP) across bulk liquid membrane. The aqueous phase pH plays an important role in the selective transport of Zn from feed to stripping phase. It was observed that more than 90% of Zn was extracted at an aqueous phase pH of 3. The kinetics of the transport was analyzed using a kinetic law of two consecutive irreversible first-order reactions. Kinetic parameters such as k1, k2, Rm, tm, and flux values were evaluated by fitting the experimental data. The order of the flux for the transport of Zn(II) in three diluents was observed as dichloromethane > chloroform > carbon tetrachloride.

Desalination using modified configuration of supported liquid membrane with enhancement of mass transfer of NaCl.

Supported liquid membranes (SLM) suffer from very slow mass transfer of the solute from the donor phase (DP) to the receptor phase (RP) through the liquid membrane (LM). In the present work, an attempt was made to accelerate the mass transfer in SLM by creating a modified configuration in which the DP and RP are made to flow either co- or counter-currently to each other. Variables, which could affect the removal of NaCl, were the volume ratio of DP to RP, type and quantity of sequestering agent (SA), presence of mobile carrier (MC), type of LM, and flow rate of DP and RP. The results showed that the higher the flow rate of DP and RP, the higher the mass transfer of NaCl. Quantity and type of SA and type of LM were prime important factors. Remarkably, the time required for transfer of NaCl from DP to RP was reduced from several hours in the case of stagnant SLM to several minutes in the present work. The mass transfer of NaCl was analysed based on kinetic laws of two consecutive irreversible first-order reactions. The values achieved establish the process is diffusion controlled, and the membrane entrance rate constants increase directly with initial concentration (Ci) and inversely with quantity of SA.

Kinetic Study of Copper(II) Simultaneous Extraction/Stripping from Aqueous Solutions by Bulk Liquid Membranes Using Coupled Transport Mechanisms

Heavy metals removal/recovery from industrial wastewater has become a prime concern for both economic and environmental reasons. This paper describes a comparative kinetic study of the removal/recovery of copper(II) from aqueous solutions by bulk liquid membrane using two types of coupled facilitated transport mechanisms and three carriers of different chemical nature: benzoylacetone, 8-hydroxyquinoline, and tri-n-octylamine. The results are analyzed by means of a kinetic model involving two consecutive irreversible first-order reactions (extraction and stripping). Rate constants and efficiencies of the extraction (k1, EE) and the stripping (k2, SE) reactions, and maximum fluxes through the membrane, were determined for the three carriers to compare their efficiency in the Cu(II) removal/recovery process. Counter-facilitated transport mechanism using benzoylacetone as carrier and protons as counterions led to higher maximum flux and higher extraction and stripping efficiencies due to the higher values of both the extraction and the stripping rate constants. Acceptable linear relationships between EE and k1, and between SE and k2, were found.

Treatment of cyanide wastewater by bulk liquid membrane using tricaprylamine as a carrier.

The transport of cyanide from wastewater through a bulk liquid membrane (BLM) containing tricaprylamine (TOA) as a carrier was studied. The effect of cyanide concentration in the feed solution, TOA concentration in the organic phase, the stirring speed, NaOH concentration in the stripping solution and temperature on cyanide transport was determined through BLM. Mass transfer of cyanide through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters (k(1), k(2), R(m)(max), t(max), J(a)(max), J(d)(max)) were also calculated. Apparently, increase in membrane entrance (k(1)) and exit rate (k(2)) constants was accompanied by a rise in temperature. The values of activation energies were obtained as 35.6 kJ/mol and 18.2 kJ/mol for removal and recovery, respectively. These values showed that both removal and recovery steps in cyanide transport is controlled by the rate of the chemical complexation reaction. The optimal reaction conditions were determined by BLM using trioctylamine as the carrier: feed phase: pH 4, carrier TOA possession ratio in organic phase: 2% (V/V), stripping phase concentration of NaOH: 1% (W/V), reaction time: 60 min, stirring speed: 250 r/min. Under the above conditions, the removal rate was up to 92.96%. The experiments demonstrated that TOA was a good carrier for cyanide transport through BLM in this study.

Kinetics of transport of sodium chloride using supported liquid pertraction

In the present work, the removal of NaCl using the present type of supported liquid membrane technique has been investigated. A simple apparatus devised and constructed was used to conduct the experiments. Various factors that would affect the progress of transport were studied and these were initial concentration (Ci) of simulated seawater in donor phase (DP), presence of mobile carrier (MC) in the liquid membrane (LM), concentration of MC in LM, presence of sequestering agent (SA) in the receptor phase (RP), and speed of stirring. The volume ratio of DP to RP was kept constant at 2:1. Type (1,2 dichloroethane (DCE)) and thickness (2 mm) of LM were kept constant. Cellophane constituted the support for the LM. The most important findings emphasized the importance of the presence of a MC in the LM to enhance mass transfer through the LM and that an optimum concentration of MC existed. Also the importance of stirring in promoting mass transfer by minimizing the boundary layer intact to the cellophane support was elucidated. The best conditions arrived at were MC = 0.0538 mol/l (mol of dibenzo-18-crown-6/l of LM), SA = 0.0617 mol/l (mol of soluble starch/l of RP), slow stirring (100 rpm) of DP, and using DCE as LM. The mass transfer of NaCl was analyzed based on kinetic laws of two consecutive irreversible first-order reactions, and kinetic parameters (k1d, k2m, k2r, Rmmax, tmax, Jdmax, Jrmax) for the transport of NaCl were investigated. The values obtained demonstrate that the process is diffusion-controlled. Results indicate that the membrane entrance and exit rate constants (k1, k2) increase directly with Ci and inversely with quantity of SA.

Bulk liquid pertraction of NaCl from aqueous solution using carrier-mediated transport

In the present work, removal of NaCl using the bulk liquid membrane (BLM) technique has been investigated, using a simple apparatus for conducting the experiments. Variables investigated were volume ratio of donor phase (DP) to receptor phase (RP), presence of sequestering agent (SA) in RP, type of organic liquid membrane (LM), quantity of mobile carrier (MC) in the LM. Stirring speed and volume of LM were kept constant at 100 rpm and 130 ml, respectively. The mass transfer of NaCl was analysed based on kinetic laws of two consecutive irreversible first-order reactions, and kinetic parameters (k1d, k2m, k2r, , tmax, , and ) for the transport of NaCl were investigated. The values obtained demonstrate that the process is diffusionally controlled. Results indicate that the membrane entrance and exit rate constants (k1, k2) increase with decreasing DP:RP ratio and with decrease in quantity of MC, and quantity of SA, and the presence of dichloroethane (DCE) is preferred to chloroform (CF) as LM.

Bulk liquid membrane extraction of silver(I) with 2-mercaptobenzothiazole as a carrier: Kinetic approach

The transport and separation of silver(I) ions across a bulk liquid membrane by 2-mercaptobenzothiazole (MBT) as carrier were investigated. The efficiency of Ag(I) transport was studied as a function of different parameters. The maximum of Ag(I) recovery was 85% in the presence of thiourea 0.1 M at pH 1, as complexing agent in the receiving phase, for a short extraction time of 4 h. A selective separation between Ag(I) and Mn(II) ions from equimolar mixture Ag–Cu–Mn solutions was performed. Besides, we have applied the kinetic model involving two consecutive irreversible first-order reactions to calculate the pseudo-first-order apparent membrane entrance and exit rate constants ke and ks, respectively. Under optimal conditions, the kinetic model curves of time dependence of silver concentrations (R) in the feed, membrane and receiving phases showed a good agreement with the experimental results. The apparent rate constants values were 6.93 × 10−3 min−1 for ke and 6.81 × 10−2 min−1 for ks. The transport of silver(I) is mainly controlled by the slow reaction of the formation of Ag–MBT complex at the membrane entrance.

Rapid transfer of methyl red using calix[6]arene as a carrier in a bulk liquid membrane

Abstract In the present investigation, a calix[6]arene-based derivative ( 1 ) is employed as a selective carrier for the efficient transport of methyl red (MR) through bulk liquid membrane (BLM). Initially, the selectivity of 1 towards MR was confirmed among different dyes, such as methyl green (MG), methyl violate (MV), methylene blue (MB), methyl orange (MO), and eosin gelblich (EG) by liquid–liquid extraction experiments. Furthermore, the effect of the initial MR concentration of salts (NaCl, Na 2 SO 4 , and Na 2 CO 3 ) and of the pH of the acceptor phase were also optimized using liquid–liquid extraction. Afterwards, the influence of basic parameters, such as carrier concentration in membrane phase, type of solvent, and stirring rate on MR transport was determined through BLM. Mass transfer of MR through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters ( k 1 , k 2 , R m max , t max , J d max , J a max ) were also calculated. Apparently, increase in membrane entrance ( k 1 ) and exit rate ( k 2 ) constants was accompanied by a rise in carrier concentration under a high stirring rate. In addition, CH 2 Cl 2 proved to be a better solvent than CHCl 3 and CCl 4 . The % transport of MR was 99% across the liquid membrane under optimized conditions. Real textile industrial wastewater samples gave also appreciable results in BLM under optimized conditions.

Cu(II) transport through soybean oil-based bulk liquid membrane: Kinetic study

Kinetic study of Cu(II) transport through a soybean oil-based bulk liquid membrane (BLM) containing di-2-ethylhexylphosphoric acid (carrier) and tributylphosphate (phase modifier) diluted in soybean oil (diluent) was conducted. Effects of initial Cu(II) concentration in the feed phase and temperature were investigated and their kinetic parameters were determined from the kinetic models of two consecutive irreversible first-order reactions. Various initial Cu(II) concentrations in the feed phase (50–500 mg/L (0.788–7.88 mM)) and temperatures (27–43 °C) were found not to affect the rate of extraction process significantly, but enhanced the rate of stripping process with decreasing initial Cu(II) concentration in the feed phase and increasing temperature. The rate-controlling steps of both extraction (diffusion-controlled) and stripping (chemical reaction-controlled) processes were determined and a plausible transport mechanism was proposed. The kinetics of Cu(II) transport through soybean oil-based BLM was then compared with that of a similar kerosene-based BLM and their extraction ( k 1) and stripping ( k 2) rate constants (soybean oil-based BLM: k 1 = 1.94 h −1, k 2 = 0.11 h −1; kerosene-based BLM: k 1 = 1.73 h −1, k 2 = 0.13 h −1) were determined. Application of soybean oil-based BLM in real industrial wastewater was also studied.

Kinetic study of chromium(VI) facilitated transport through a bulk liquid membrane using tri-n-butyl phosphate as carrier

Abstract The facilitated transport of Cr(VI) through a bulk liquid membrane (BLM) is investigated, using the commercially available solvent tri- n -butyl phosphate (TBP) as mobile carrier. The influences of the carrier concentration in the liquid membrane phase, the HCl concentration of the feed phase, and the stripping concentration on the mass transfer process are studied. The transport rate of Cr(VI) increases with increasing the TBP concentration and HCl concentration. The increasing of the stripping concentration improves the stripping process until a plateau is reached. A kinetic model is used to describe the Cr(VI) transport behavior, assuming that it obeys the kinetic laws of two consecutive irreversible first-order reactions. The experimental data fits reasonable well with the derived model. The analysis of the accumulation of Cr(VI) in the liquid membrane phase and the discussion of the rate-controlling step under different experimental conditions are carried out. The magnitude of the value of k e and k s is found to be 10 −4 –10 −5 s −1 , and is well in agreement with other studies.

Study of the kinetics of the transport of Cu(II), Cd(II) and Ni(II) ions through a liquid membrane

The coupled transport of Cu(II), Cd(II) and Ni(II) ions through a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as carrier dissolved in toluene has been studied. Once the optimal conditions of extraction of each metal were established, a comparative study of the transport kinetics for these metals was performed by means of a kinetic model involving two consecutive irreversible first-order reactions. The kinetic parameters (apparent rate constants of the metal extraction and re-extraction reactions (k(1), k(2)), the maximum reduced concentration of the metal in the liquid membrane (R(o)max), the time of the maximum value of R(o)(t(max)) and the maximum entry and exit fluxes of the metal through the liquid membrane (J(f)max and J(s)max) of the extraction and stripping reactions were evaluated and results showed good agreement between experimental data and theoretical predictions. Complete transport through the membrane took place according to the following order: Cd(II)>Cu(II)>Ni(II), with similar kinetic parameters obtained for Cu(II) and Cd(III). The transport behaviour of Ni(II) was different to that of Cu(II) and Cd(III), probably due to the different stoichiometry of the nickel complex compared to those of the other metal ions and the different chemical conditions required for its formation. The influence of the sample salinity on the transport kinetics was studied. k(1) values decreased slightly when the feed solution salinity was increased for Cu(II) and Ni(II), but not for Cd(II). Values of k(2) were practically unaffected. The proposed BLM was applied to the preconcentration and separation of metal ions (prior to their determination) in water samples with different saline matrices (CRM, river water and seawater), and good agreement with the certified values was obtained.

Facilitated transport of copper through bulk liquid membranes containing different carriers: compared kinetic study

The discharge of heavy metals into the environment is a serious problem facing numerous industries. Heavy metals tend to accumulate in living organisms causing various diseases and disorders. So the search for extraction techniques to remove those heavy metals are of increasing interest. Liquid membranes have shown great potential in this way, especially in cases where metal concentrations are relatively low and other techniques cannot be applied efficiently. A comparative kinetic study of the facilitated counter transport of copper ion through bulk liquid membranes containing D2EHPA, CYANEX 272 and LIX 984N as carriers and protons as counter ions is carried out is this paper. The transport kinetic was analysed by means of a kinetic model involving two consecutive irreversible first-order reactions. The rate constants of the extraction and stripping reactions and the maximum transport fluxes of copper(II) through the bulk liquid membrane were determined for the three carriers.

Effect of carrier type on coupled transport kinetics of thiocyanate ions through liquid membranes

Coupled transport of thiocyanate ions through a liquid membrane containing quaternary ammonium chloride salts in chloroform was examined. The influences of the carrier type in the membrane phase on the coupled transport of thiocyanate ions were investigated. The kinetics of the coupled transport were analyzed in the formalism of two consecutive irreversible first-order reactions and the kinetic parameters ( k 1 d , k 2 m , k 2 a , R m max, t max, J d max, J a max) were also calculated. For the coupled transport of thiocyanate ions, quaternary ammonium chloride salts having different carbon atom numbers ( C n ) used as carriers were found to increase thiocyanate ions transport efficiency with increasing carbon atom numbers. Tetradecyl trimethylammonium chloride (TDTMACl), hexadecyl trimethylammonium chloride (HDTMACl), and tetraoctyl ammonium chloride (TOACl) were found to be the most effective carrier types for transport of thiocyanate ions when C n is greater than 16. The activation energies for maximum membrane entrance and exit fluxes were calculated as 32.45 kJ/mol and 34.75 kJ/mol, respectively. The values of the activation energy indicate that the process is controlled by species diffusion.

Transport of metals through a liquid membrane containing calix[4]arene derivatives as carrier

Co-transport of metals (Hg2+, Pb2+, Na+) from an aqueous solution into an aqueous-receiving solution through a bulk liquid membrane containing calix[4]arene nitrile derivatives as carriers was investigated. Kinetic parameters were analyzed with consecutive irreversible first-order reactions and the effect of solvents such as CH2Cl2, CHCl3, and CCl4 was also examined. The transport rates show that both nitrile derivatives are efficient and selective for Hg(II) ions with respect to Na+ and Pb2+ ions and the dinitrile derivative is found to be a better carrier than the tetranitrile one. The membrane entrance- and exit rate-constants depend on the solvent type and are found to be in the order CH2Cl2>CHCl3>CCl4. A remarkable difference was also observed of the same order for fluxes.

Effect of kinetic synergist on transport of copper(II) through a liquid membrane containing P507 in kerosene

A new kinetic synergism system for copper(II) transport through a bulk liquid membrane containing mono(2-ethyhexyl)-2-ethyhexyl phosphate and Manoxol OT (OT) was examined. The influence of stripping agent, anion, pH in feed phase, and carrier concentration were investigated. The kinetics of Cu(II) transport could be analyzed in the formalism of two consecutive irreversible first-order reactions, considering both extraction and stripping. The pseudo-first-order apparent rate constants of interfacial reactions in membrane transport are determined by altering the temperature. The activation energy values are 38.1 kJ mol–1 for extraction and 32.8 kJ mol–1 for stripping. The experiments demonstrated that Manoxol OT is a good kinetic synergist for Cu(II) transport through liquid membranes in this study. The kinetic synergism of OT for extraction of Cu2+ ions is analyzed.Key words: copper ions, kinetic synergist, liquid membrane.

Effect of paraffin and surfactant on coupled transport of cadmium(II) ions through liquid membranes

The transport of Cd(II) ions from an aqueous feed chloride solution to an ammonium acetate stripping solution through a supported liquid membrane containing tri- n-octylamine (TOA) in xylene has been examined. The influence of stirring rate, carrier concentration, stripping agent and H + concentration in the feed solution was investigated. The transport of Cd(II) ions is coupled by the co-transport of protons. The kinetics of transport could be analyzed in the formalism of two consecutive irreversible first-order reactions, considering both extraction and stripping reactions. The pseudo-first-order rate constants of interfacial reactions in membrane transport are determined with a bulk liquid membrane based on paraffin and the surfactant Span-80. The experimental results show that the effect of paraffin or surfactant in the membrane is different for the interfacial reactions of extraction and stripping.

Kinetics of Cadmium(II) Transport through a Liquid Membrane Containing Tricapryl Amine in Xylene

Coupled transport of Cd(II) ions through a supported liquid membrane containing tricapryl amine in xylene has been examined. The influences of stirring rate, carrier concentration, stripping agent, and H+ concentration in the feed solution were investigated. The transport of Cd(II) ions is coupled by cotransport of protons. The kinetics of Cd(II) transport could be analyzed in the formalism of two consecutive irreversible first-order reactions. The pseudofirst-order apparent rate constants of interfacial reactions in membrane transport were determined with bulk liquid membrane at various temperatures. The activation energy values are 14.7 kJ·mol−1 for extraction and 12.4 kJ·mol−1 for stripping.

Use of spreadsheets in the kinetic analysis of two consecutive first-order reactions

The present author developed an expression in a previous report that could be applied to the determination of the two rate constants, k 1 and k 2, for two consecutive irreversible first-order reactions (2CIFR). This expression was solved utilizing various computer methods and rate data (which could be obtained from conversion (α) versus time ( t) curves). Thus, BASICA (IBM), Lotus spreadsheets, and the Paradox data base were employed. The usual expressions developed for 2CIFR can be converted into dimensionless parameters and variables (DPV). One investigator (to be mentioned subsequently) developed a procedure whereby these DPV could be used to solve for k 1 and k 2 in 2CIFR. His method was rather tedious in that it involved plotting, superposing, and displacement measurements. In the present paper, a Lotus spreadsheet will be utilized to analyze 2CIFR for k-values. By means of this analysis, which utilizes dimensionless variables, these k-values will be obtainable in a matter of seconds once the experimental data is provided.

Use of databases in thermal analysis. Part 6

In our previous publication (Thermochim. Acta 222 (1993) 85), a computer algorithm was devised which allowed the concurrent determination of two rate constants, k 1 and k 2, for two consecutive irreversible first-order reactions. The Paradox 3.5 database was employed, and database analyses were carried out using both theoretical and experimental data. The k values obtained were in satisfactory agreement with assumed and observed values. In all the runs made, the values of k 1 were much larger than those corresponding to k 2. The preceding algorithm, however, did not hold for cases where k 2 was greater than k 1. The aim of the present paper is to modify the preceding script so that the resulting script will be applicable to both cases, k 1 > k 2 and k 2 > k 1. Limitations of the method will be described where applicable.