Acidic Cation-exchange Resin Research Articles

Sorption of Lanthanum(III) and Neodymium(III) from Concentrated Phosphoric Acid by Strongly Acidic Cation Exchange Resin (SQS-6)

The feasibility of using a macroporous strongly acidic cation exchange resin (SQS-6) as an adsorbent for lanthanum(III) and neodymium(III) from phosphoric acid medium, >4.0 M, was administered using batch and column techniques. Different parameters affecting the sorption of these metal ions such as v/m ratio, acid concentration and the metal ion concentration were separately investigated. The results indicated that the sorption process is relatively fast, reaching equilibrium state within 10 min. Influence of temperature on the equilibrium distribution values was also studied to evaluate the changes in standard thermodynamic quantities where the results indicated that the sorption is endothermic and the process is spontaneous associated with increasing the randomness of the system. The adsorption results of the studied metal ions were found to obey Langmuir isotherm model over the entire studied concentration range. The recovery of La(III) and Nd(III) from the loaded resin was performed with 1.0 M citric acid at pH 4.0. The breakthrough capacity of La(III) and Nd(III) was found to be 33.55 and 17.30 mg/g, respectively. The experimental data resulting from column technique were followed Thomas and Yoon-Nelson models.

Superhigh adsorption of nickel from electroplating wastewater by raw and calcined electroplating sludge waste

Abstract Both the raw electroplating sludge (RES) waste and the calcined electroplating sludge (CES) were utilized to adsorb nickel from the real electroplating wastewater. The CES was obtained via calcination treatment at 500 °C, and the CES and RES were characterized by X-ray fluorescence (XRF), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffraction (XRD). Adsorption isotherm results showed that the maximum adsorption capacities of Ni2+ on the CES and RES were 163.6 and 210.9 mg/g according to the Langmuir fitting, respectively. In the real nickel-containing wastewater treatment, the RES exhibited much higher adsorption capacity for Ni2+ than commonly used adsorbents including coal-based activated carbon (CAC), strong acid cation-exchange resin (D001), weak acid cation-exchange resin (D113) and amino carboxylic acid chelating resin (D463). The adsorption mechanisms of Ni2+ on the RES and CES mainly included ion exchange and surface complexation. The large amount of Ca2+ in the adsorbents played an important role in the adsorption of Ni2+ via cation exchange, and the hydroxyl and carboxyl groups on the adsorbent were also responsible for Ni2+ adsorption. Therefore, the electroplating sludge waste is an efficient adsorbent for Ni2+ removal from high concentrations of nickel-containing electroplating wastewater. This study provides a new method for the utilization of electroplating sludge as efficient adsorbents before being treated as hazardous waste, showing the feasible concept of disposal waste with waste.

Studies on active aromatic constituents from rhizomes of Sophora tonkinensis

Aromatic constituents from rhizomes of Sophora tonkinensis were purified by extensive chromatographic techniques including column chromatography over macroporous resin,MCI,silica gel,weak acid cation exchange resin,Sephadex LH-20,ODS,and semi-preparative HPLC. Twelve aromatic compounds were isolated and identified from the water aqueous extract of the rhizomes of S.tonkinensis. Their structures were elucidated as 4-( 3-hydroxypropyl) phenol( 1),( ±)-4-( 2-hydroxypropyl) phenol( 2),benzamide( 3),( ±)-3-( p-methoxyphenyl)-1,2-propanediol( 4),4-methoxybenzamide( 5),3-hydroxy-1-( 4-hydroxy-3-methoxyphenyl) propan-1-one( 6),tyrosol( 7),( ±)-2,3-dihydroxypropyl benzoate( 8),vanillin alcohol( 9),7,3'-dihydroxy-8,4'-dimethoxyisoflavone( 10),7,4'-dihydroxy-3'-methoxyisoflavone( 11),and 7,3'-dihydroxy-5'-methoxyisoflavone( 12). Compounds 1-9 were firstly isolated from the Sophora genus. Compounds 4,5,10 and 11 can remarkably protect Hep G2 cell against APAP-induced damage at the concentration of 10 μmol·L-1. Compounds 1-12 exhibited no significant activities on the assays of inhibition of LPS-induced NO production in RAW cell lines and NF-κB inhibition.

Study on Methyl Esterification of Salicylic Acid Using an Intensified Fixed Bed Reactor

Abstract Methyl esterification of salicylic acid catalyzed by strong acidic cation exchange resin NKC-9 was carried out on an intensified fixed bed reactor (IFBR) to investigate the effects of different parameters and the results showed that the optimal conditions were as follows: circulation speed is 1.5 L· h−1, catalyst loading is 20 %, initial mole ratio of salicylic acid and methanol is 1:6 and reaction temperature is 343.15 K. The thermodynamics for the methyl esterification of salicylic acid have been studied to obtain the equilibrium constant from the experimental data at different temperature. PH, E-R and LHHW models were used to correlate the kinetic data in the temperature range from 328.15 to 348.15 K. The calculated value is in good agreement with experimental value, indicating that all the models can be used to accurately describe the process of the methyl esterification of salicylic acid.

Rapid Separation and Precise Determination of Strontium Isotopic from Geological Samples with High Rubidium/Strontium Ratios

Abstract In the isotopic measurement of strontium (Sr) of geological samples with high rubidium (Rb)/Sr ratios, it is difficult to completely remove the isobaric interference of Rb on Sr isotopic analysis by a single separation and purification using traditional strong acid cation exchange resin. Actually, one purification procedure performed twice is necessary to eliminate the interference of 87Rb on the testing of 87Sr/86Sr. Although the purification procedure can ensure a good effect on the separation and purification of Sr, the process is tedious and time-consuming, which is not suitable for simultaneous separation and purification of Sr from large quantity of geological samples with high Rb/Sr ratios. In this study, the conventional two-stage separation process was optimized, and an experimental method for rapid separation of Sr from geological samples with high Rb/Sr ratios was established. In this method, the Sr solution after purified by AG50 resin was directly added to a new AG50 resin to purify Rb and Sr again. The whole separation process would be accomplished quickly and efficiently. The method combined with highly sensitive thermal ionization mass spectrometer (TIMS) technique was completely satisfied in high precision determination of 87Sr/86Sr isotope ratio in the samples with high Rb/Sr ratios. Through the application of the novel separation method with a large number of geological samples with high Rb/Sr ratios, it was proved that the experimental process was stable and reliable and showed crucial application value.

Kinetics study on esterification of acrylic acid and ethanol over acidic cation-exchange resin beads Amberlyst 35

Abstract The heterogeneous kinetics and adsorption behavior for the esterification of acrylic acid and ethanol were studied by using a fixed-bed reactor over an acidic cation-exchange resin beads, Amberlyst 35. The reaction experiments were conducted at 318.15 K–348.15 K under atmospheric pressure. The influences of molar ratios of ethanol to acrylic acid in the feed (θBo) and the mass transfer resistances on the kinetic behavior were also investigated. The experimental results show that the equilibrium conversion of acrylic acid increases with increasing reaction temperature and θBo. Moreover, the adsorption experiments were also made to determine the relative adsorption strengths among the reacting species. The results reveal that the magnitude of adsorption strengths obeyed the sequence of water > acrylic acid > ethanol > ethyl acrylate. The kinetic data obtained from the present study were correlated with the ideal-quasi-homogeneous (IQH), the non-ideal-quasi-homogeneous (NIQH), the Langmuir-Hinshelwood-Hougen-Waston (LHHW), the Eley-Rideal (ER) models, the modified LHHW (M-LHHW) and the modified ER (M-ER). The best-fitted values of the kinetic parameters were reported. The correlated results indicated that the M-LHHW model provides the best representation for this reaction system.

An Isolated Method and Assignment for Critical Impurities in Semi-Synthetic Process of Arbekacin Sulfate.

Four potential process related impurities were detected during the impurity profiling study of a semi-synthetic aminoglycoside antibiotic, arbekacin. The current preparation process from 3',4'-didehydro-dibekacin easily generates the specific impurities with similar structures to arbekacin that makes hard to separate and identify the residues. HPLC-ELSD and column chromatography loading weakly acidic cation exchange resin were used for the detection and isolation of these process impurities. Based on the synthesis and spectral data (ESI-MS/MS, 1H NMR, 13C NMR and 2D-NMR), the structures of these impurities were characterized as dibekacin, 3-N-γ-aminohydroxybutyric (AHB)-dibekacin, 3''-N-AHB-dibekacin and 1,3-N,N-di-AHB-dibekacin. The characterization of these impurities is discussed in detail and our current efforts may help to develop a general strategy for isolation and identification of aminoglycoside products.

Effectiveness of Ionic Polymer Soil Stabilizers on Warm Frozen Soil

Warm frozen soil has characteristics such as low shear strength and high compressibility. To improve its mechanical strength, the ionic polymer soil stabilizers (IPSS): named XRH stabilizer and acid cation exchange resin (CER) were adopted for reinforcing the warm frozen soil from the Beiluhe region of the Qinghai-Tibetan Plateau. To evaluate the effects of IPSS on warm frozen soil and analyze the mechanisms responsible, measurements were made of the physical, chemical and mechanical properties of warm frozen soil, both untreated and following treatment with IPSS. The addition of IPSS to the soil resulted in a significant decrease in the plasticity index, freezing temperature, and cation-exchange capacity of soil. The warm frozen soil were reinforced with XRH and CER, the cohesion increased by 87.9% and 43.1%, respectively, and the compressibility decreased by 44.5% and 41.1%, respectively. The trends of mechanical strength and unfrozen water content of reinforced warm frozen soil were the same, with extreme values being observed in response to treatment with an IPSS content of about 1% (optimal proportion). In addition, the curing mechanism of IPSS on warm frozen soil was analyzed. Overall, applying IPSS to the soil was an effective and feasible measure for reinforcing a warm frozen soil foundation.

Simple Synthesis and Characterization of Hexagonal and Ordered Al–MCM–41 from Natural Perlite

Silica reagents are expensive and toxic for use in the synthesis of mesoporous silica materials. It is imperative to take an interest in green silicon sources. In this paper, we report the synthesis of hexagonal and ordered aluminum-containing mesoporous silica materials (Al–MCM–41) from natural perlite mineral without addition of silica or aluminum reagents. A pretreatment process involving acid leaching, alkali leaching, and strongly acidic cation exchange resins treatment was critical to obtain silicon and aluminum sources from natural perlite mineral. The Al–MCM–41 material was synthesized via a hydrothermal reaction with hexadecyl trimethyl ammonium bromide (CTAB) as the template and subsequent calcination. The resulting mesophase had a hexagonal and ordered mesoporous structure, confirmed by small-angle X-ray diffraction (SAXRD) and transmission electron microscopy (TEM). Al–MCM–41 material had a high Brunauer–Emmet–Teller (BET) surface area of 1024 m2/g, pore volume of 0.72 cm3/g and an average pore diameter of 2.8 nm with a pore size distribution centered at 2.5 nm. The thermal behavior of the as-synthesized samples during calcination was investigated by thermogravimetry (TG) and differential thermogravimetry (DTG) analysis. The Al–MCM–41 material showed a negative surface charge in aqueous solution with the pH value ranging from 2 to 13. The variations of chemical structures from natural perlite to Al–MCM–41 were traced by wide-angle X-ray diffraction (WAXRD) and Fourier-transform infrared spectroscopy (FTIR). A proposed mechanism for the synthesis of hexagonal and ordered mesoporous silica materials from natural perlite is discussed.

Removal of hexavalent chromium in soil by lignin-based weakly acidic cation exchange resin

Abstract The adsorption of Cr(VI) from soil onto lignin-based weakly acidic cation exchange resin (LBR) has been investigated. Lignin is a three-dimensional amorphous polymer composed of methoxylated phenylpropane units. The unique structure and chemical properties render the lignin suitable for the remediation of hexavalent chromium in the soil. Soil column leaching experiments were conducted to optimize the adsorption conditions. The effects of contact time, pH, adsorbent dosage and temperature on the adsorption of Cr(VI) onto the LBR have been investigated. Experiment data were then correlated with Freundlich and Langmuir isotherms. The Langmuir isotherm model fits the experimental data better than the Freundlich isotherm. It was found that the LBR has a high adsorption capability for Cr(VI) (3.95 mg·g−1) with a removal rate of 91.9%. Thus, LBR can serve as a good absorbent for the reduction of the concentration of Cr(VI) in soil.

Selective Separation of Radium and Actinium from Bulk Thorium Target Material

A complete scheme for the selective separation of actinium and radium isotopes from bulk 232Th target material will be presented. The process may be applicable to the production of 225Ac and 227Ac via proton spallation on thorium targets. Thorium metal is dissolved in sulfuric acid with small amounts of HF. Actinium and radium are retained on cation exchange resin from the sulfate medium, while neutral and anionic thorium sulfate complexes are rejected. Targeting the minor components (Ac,Ra) allows use of much smaller chromatographic columns than traditional nitrate based systems which target the bulk thorium. Additionally, the primary separation is performed from 0.1M Th, 0.6M sulfate, pH 1-2 instead of the more corrosive 3-8M HNO3 typically employed in solvent extraction or anion exchange based thorium separations. Actinium and radium are recovered from the cation exchange resin in a small volume of 5M HNO3 and directly purified via extraction chromatography with UTEVA and DGA resins without feed adjustment or evaporation. The radium fraction can be further processed following ingrowth of 225Ac from 225Ra to produce additional 225Ac free from any potential 227Ac impurity. The flowsheet has been tested at the Canadian Nuclear Laboratory (CNL) on 25 gram solid thorium targets irradiated at Fermi Lab. -Bond, A.H., Horwitz, E.P., McAlister, D.R., 2006. A Multicolumn Selectivity Inversion Generator for the Production of High Purity Actinium-225 for Use in Therapeutic Nuclear Medicine, United States patent number 7,087,206. (Licensed to NorthStar Medical Radioisotopes) -D.R. McAlister, E.P. Horwitz, “Selective Separation of Radium and Actinium from Bulk Thorium Target Material on Strong Acid Cation Exchange Resin from Sulfate Media,” Applied Radiation and Isotopes, 140, 18-23 (2018).

Studies on Epoxidised Castor Oil as Co-Plasticizer with Epoxidised Soyabean Oil for PVC Processing

An acidic cation exchange resin has been used to prepare epoxidised castor oil (ECO) which was used as a co-plasticizer with epoxidised soyabean oil (ESBO) for processing polyvinyl chloride (PVC). The structure of ECO was confirmed and its physico chemical properties were evaluated. PVC/(ESBO&ECO) blends were prepared by melt mixing and compression molded into sheets. The specimens were evaluated for tensile properties, impact strength and hardness. While the tensile strength did not vary much, the elongation reduced with the replacement of ESBO with ECO. Dynamic mechanical studies revealed that the glass transition temperature increased with incorporation of ECO, however, the storage modulus was not altered much. Replacing 20% of ESBO with ECO resulted in blends with desired thermal and mechanical properties without affecting the processability of PVC.

Highly ordered and hexagonal mesoporous silica materials with large specific surface from natural rectorite mineral

Highly ordered and hexagonal mesoporous silica materials containing aluminum were successfully synthesized from natural rectorite mineral via a novel strategy. Silicon and aluminum sources were obtained from rectorite mineral by a pretreatment method involving acid leaching, alkali leaching and strongly acidic cation exchange resins (SACERs) treating, followed by a hydrothermal reaction with hexadecyl trimethyl ammonium bromide (CTAB) as template and subsequent calcination to prepare Al-MCM-41. More importantly, Wide angle X-ray diffraction (WAXRD), fourier transform infrared spectroscopy (FT-IR) and solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR) results indicated that acid treatment did not destroy the structure of natural rectorite. Unlike other silicate minerals, natural rectorite failed to provide suitable silicon sources because of residual hydroxide from alkali leaching process. In this paper, SACERs instead of inorganic acids were adopted to neutralize residual hydroxide, which avoided excessive inorganic anions to hinder the synthesis of Al-MCM-41 by a hydrothermal reaction. The final Al-MCM-41 products were amorphous SiO2, with a surface area of 1032 m2/g, pore volume of 0.97 cm3/g and an average pore diameter of 2.6 nm. A proposed mechanism for synthesizing mesoporous silica from natural rectorite was suggested.

Adsorption of rare earth elements by strong acid cation exchange resin thermodynamics, characteristics and kinetics

The equilibrium and kinetic characteristics of rare earths adsorption process using the strong acid macro reticular resin Dowex 50X8 from El-Erediya chloride liqueurs have been determined. The adsorption parameters including pH, contact time, temperature, resin to aqueous ratio and rare earths initial concentration in aqueous have been optimized. The practical adsorption capacity of rare earths upon the resin under the optimum conditions has been found to attain 80 mg/g which matches with Langmuir theoretical capacity. The physical parameters including the adsorption kinetics, the isotherm models and the thermodynamic data have also been determined. The adsorption process has been found to agree with both the pseudo second order reaction, the Langmuir isotherm and confirms with the concept of the matrix diffusion controls. A successful preconcentration process for the rare earths content was done with a preconcentration factor of about 42.33. Considerable rare earths cake was precipitated from the chloride eluate solutions using oxalic acid.

Continuous synthesis of isobornyl acetate catalyzed by a strong acid cation exchange resin in an oscillatory flow reactor

Recently, the application of continuous reaction technology for the production of fine chemicals has expanded significantly. Despite the increasing interest in continuous flow manufacturing, most industries continue to use multipurpose batch or semi-batch reactors. In this work, the utilization of a continuous oscillatory flow reactor(OFR) for heterogeneous catalysis is demonstrated by conducting a typical acetylation reaction (the acetylation of camphene) Parallel experiments was also performed in a batch stirred tank reactor (BSTR), and the results were compared with those obtained in the OFR. The temperature inside the OFR was uniform than that inside the BSTR, and the residence time distribution in the former system was close to that in a plug flow reactor. In addition, the OFR exhibited higher reaction rate and selectivity values than those obtained for the BSTR. Although the liquid was refreshed faster inside the OFR and no polymer residue was formed on the catalyst surface, its application required the screening of catalysts grains, which increased the probability of surface cracking. The OFR for continuous flow catalysis can serve as a promising starting point in the development of new, low-cost, and more efficient reactors for the synthesis of pharmaceuticals and other fine chemicals.

Sugarcane bagasse mild alkaline fractionation and production of purified fractions by pulse chromatography with water

Sugarcane bagasse (SCB) was treated under mild alkaline conditions (solid:liquid ratio of 1:20 (w/v), 1.5% NaOH (w/v), 60 °C, 6 h) to fractionate the lignocellulose in order to produce a typical mild alkaline extract from a lignocellulosic biomass. The solid residue was enriched in cellulose, while the SCB alkaline extract contained lignin and hemicelluloses, but also inorganic salts, five phenolic monomers and acetic acid. After concentration of the alkaline extract by evaporation, low pressure chromatography with water as eluent was performed to produce purified fractions. Two different strong acid cation (SAC) exchange resins were tested: one gel-type resin and one macroporous-type resin. The lignin and hemicelluloses were separated from the inorganic salts by the gel-type SAC exchange resin. On this resin, the phenolic monomers were partitioned regarding the presence or absence in their structure of a carboxyl group. On the macroporous-type SAC exchange resin, the largest sugar oligomers and lignin oligomers were obtained in a fraction free of inorganic salts, phenolic monomers and acetic acid.

Removal of Ionic Liquids from Oil Sands Processing Solution by Ion-Exchange Resin

Ionic liquids (ILs) have been reported to be good process aids for enhanced bitumen recovery from oil sands. However, after the extraction, some ionic liquids are left in the residual solids or solutions. Herein, a washing–ion exchange combined method has been designed for the removal of two imidazolium-based ILs, ([Bmim][BF4] and [Emim][BF4]), from residual sands after ILs-enhanced solvent extraction of oil sands. This process was conducted as two steps: water washing of the residual solids to remove ILs into aqueous solution; adsorption and desorption of ILs from the solution by the sulfonic acid cation-exchange resin (Amberlite IR 120Na). Surface characterization showed that the hydrophilic ionic liquids could be completely removed from the solid surfaces by 3 times of water washing. The ionic liquids solution was treated by the ion-exchange resin. Results showed that more than 95% of [Bmim][BF4] and 90% of [Emim][BF4] could be adsorbed by the resins at 20 °C with contact time of 30 min. The effects of some typical coexisted chemicals and minerals, such as salinity, kaolinite (Al4[Si4O10](OH)8), and silica (SiO2), in the solution on the adsorption of ionic liquids have also been investigated. Results showed that both kaolinite and SiO2 exerted a slight effect on the uptake of [Bmim][BF4]. However, it was observed that increasing the ionic strength of the solution by adding salts would deteriorate the adsorption of [Bmim]+ on the resin. The adsorption behaviors of two ILs fit well with the Sips model, suggesting the heterogeneous adsorption of ionic liquids onto resin. The adsorption of ionic liquids onto Amberlite IR 120Na resin was found to be pseudo-second-order adsorption. The regeneration tests showed stable performance of ion-exchange resins over three adsorption–desorption cycles.

Single injection ion-exclusion/cation-exchange chromatography for simultaneous determination of organic/inorganic anions, inorganic cations, and ethanol in beer samples

Multicomponent simultaneous analysis is important for management programs, which are required in beer industries because the beer constituents measure by combining several methods in the present. In response to a requirement, our research group developed single sample injection ion chromatography systems, which comprise ion-exclusion/cation-exchange chromatography (IEC/CEC) and post-column derivatization and show promise for simultaneously determining concentrations of organic and inorganic species and alcohol commonly found in beer. Optimal chromatographic resolutions for determining 17 different species in beer samples by IEC/CEC were obtained on a H+-formed weakly acidic cation-exchange resin column with an eluent comprising 2 mM phthalic acid and 1 mM 18-crown-6. Consequently, the usefulness of developed method for monitoring beer samples was demonstrated in terms of beneficial information such as dependency of K+ concentration on the malt amount, influences of organic anion concentrations on different types of bottling methods, and validation of ethanol concentrations displayed in the ingredient table.

Sorption of Fluoride Ions by Iron Oxyhydrate Fixed on the Carriers Part I. Organic Carriers

The possibility of using an inorganic sorbent of iron oxyhydrate (IOH) for the removal of F– ions from process solutions of zinc production is considered. The synthesis method of IOH is chosen. The results of scanning electron microscopy and X-ray phase analysis are presented. The possibility in principle of using ion-exchange resins as carriers modified by IOH is considered. The formation of an active substance on anion-exchange and cation-exchange resins is investigated. It is shown that the strongest composite sorbents are formed when using strong acidic cation-exchange resins with sulfonate groups. The method of IOH incorporation into the structure of carrier materials and the formation of composite sorbents is described. The KU-2×8 cation exchanger is recommended as the composite basis. To form IOH crystals of the β-modification distributed over the ion-exchanger grain bulk, iron-saturated cation exchangers are held in the sodium chloride solution with a concentration of 2.5 g/dm3 for 24 h at 85°C. Anion exchangers are held in the iron(III) sulfate solution with the sodium chloride additive for 24 h at t = 85°C. Herewith, the formation of IOH films on the surface of sorbent grains is observed. The fluorine was sorbed in a static mode from a model solution with the concentration of F– = 100 mg/dm3 at t = 60°C. The sorption on the AV-17×8 anion exchanger is performed at t = 20°C. Adsorbed fluorine is desorbed by the 0.1 M NaOH solution at t = 60°C for 2 h. The synthesized KU-2×8-IOH composite sorbent has a capacity of 0.7–1.1 mg/g with respect to fluorine and can be regenerated with the formation of easily utilizable fluorine-containing eluate.

Application of ion-exchange resin as solid acid for buffer-free production of γ-aminobutyric acid using Enterococcus faecium cells

In this study, ion-exchange resin was applied as solid acid catalyst for the γ-aminobutyric acid (GABA) production using a strain of Enterococcus faecium (GZ2) by whole-cell bioconversion. It was observed that the accumulated GABA resulted in the inhibition of the bioconversion activity. To improve the productivity, a cation-exchange resin-based in situ product removal (ISPR) approach was developed. Three cation-exchange resins were tested to select a suitable adsorbent used in the bioconversion. The strong acidic cation-exchange resin IRP-69 exhibited the highest GABA production and remained helpful in reducing the free GABA concentration in the reaction solution. Compared to the bioconversion in sodium acetate buffer, the GABA production, with the addition of resin, was significantly improved by 2.12-fold. Furthermore, a fed-batch bioconversion strategy with the feeding of L-monosodium glutamate (L-MSG) was tested. The maximum production of GABA, 406.1 mM, was achieved after 12 h reaction with an initial substrate concentration of 200 mM, and a triple feeding of 100 mM L-MSG afterwards at 4 h, 6 h and 8 h. The result shows that the operation of bioconversion reaction in a feeding substrate batch mode is an effective approach to improve the efficiency and productivity of GABA.