Simultaneous removal of tetracycline and copper ions from wastewater by flow-electrode capacitive deionization.

ABSTRACTTo effectively solve the problem of tetracycline (TC) and Cu2+ contamination in wastewater, this study innovatively proposed a low-energy flow-electrode capacitive deionization (FCDI) technology to simultaneously remove TC and Cu2+ from wastewater. The removal efficiencies of TC and Cu2+ using FCDI was investigated under various voltages, electrode flow rates, influent flow rates, and electrode liquid concentrations. The results showed that the removal efficiency of TC and Cu2+ was 60.78% and 84.43%, respectively. The energy consumption for TC and Cu2+ removal was only 1.76 and 1.10 kWh kg-1, which was lower than other electrochemical systems. The ion removal performance of the FCDI system remained stable after six cycles of continuous operation. These findings demonstrated the promising potential of FCDI as an innovative technology for the simultaneous removal of TC and Cu2+, presenting a significant prospects for application in the water treatment field.

Porous biochar derived from walnut shell as an efficient adsorbent for tetracycline removal.

In this study, a high-performance porous adsorbent was prepared from biochar through a simple one-step alkali-activated pyrolysis treatment of walnut shells, and it was effective in removing tetracycline (TC). The specific surface area (SSA) of potassium hydroxide-pretreated walnut shell-derived biochar pyrolyzed at 900 °C (KWS900) increased remarkably compared to that of the pristine walnut shell and reached 1713.87 ± 37.05 m2·g-1. The maximum adsorption capacity of KWS900 toward TC was 607.00 ± 31.87 mg·g-1. The pseudo-second-order kinetic and Langmuir isotherm models were well suited to describe the TC adsorption process onto KWS900. The KWS900 exhibited high stability and reusability for TC adsorption in the presence of co-existing anions or cations over a wide pH range of 1.0-11.0. Further investigations demonstrated that the proposed adsorption mechanism involved pore filling, hydrogen bonding, π-π stacking, and electrostatic interaction. These findings provide a valuable reference for developing biochar-based adsorbents for pollutant removal.

An anode fabricated by Co electrodeposition on ZIF-8/CNTs/CF for peroxymonosulfate (PMS) activation.

A Co@ZIF-8/CNTs-CF anode for PMS activation was prepared by Co electrodeposition on carbon felt (CF) modified with ZIF-8 and carbon nanotubes (CNTs). The results showed that the fabricated Co@ZIF-8/CNTs-CF anode was an effective peroxymonosulfate (PMS) activator toward tetracycline (TC) removal. Compared with that in reaction system of bare CF anode + PMS, the reaction system of Co@ZIF-8/CNTs-CF anode + PMS exhibited 3.08 times decrease in the activation energy demanded and 4.21 times increase in the reaction rate constant (k), resulting in a kinetic favorable process of PMS activation by the Co@ZIF-8/CNTs-CF anode. The enhanced activation performance of the fabricated anode was ascribed to the high contents of the pyrrolic N and low valence state of Co in the Co@ZIF-8/CNTs-CF anode. Furthermore, the influence factors on the characteristics of transformation among the generated reactive species during the anodic PMS activation process were comprehensively investigated by the quenching experiments and the electron paramagnetic resonance (EPR) tests. The results showed that the SO4•- and reactive oxygen-containing reactive species (O2•- and 1O2) were generated during the activation of PMS by anode and became the major contributors toward TC removal. The production of 1O2 was through the dismutation of O2•-. In addition, the EPR experiments demonstrated that O2•- was generated mainly through the anodic PMS activation but the electrochemically driven molecular oxygen reduction reaction (ORR) process. The fabricated Co@ZIF-8/CNTs-CF anode for PMS activation provided a reference for the wastewater treatment based on the electrochemical advanced oxidation processes (EAOPs).

A carbon felt cathode modified by acidic oxidised carbon nanotubes for the high H2O2 generation and its application in electro-Fenton.

Herein, a carbon felt (CF) cathode modified by the acidic oxidised carbon nanotubes (OCNTs) exhibited a high yield of the H2O2 generation in electro-Fenton. Rotating disk electrode (RDE) measurements showed that the selective generation of H2O2 occurred on the CF cathode coated by OCNTs (OCNTs/CF), which was attributed to the high amount of oxygen-containing functional groups in OCNTs. Moreover, the pollutant degradation efficiency could almost reach 100% within 60 min in electro-Fenton with OCNTs/CF as the cathode. Furthermore, the pollutant removal efficiency was kept constant after five consecutive cycles, indicating the high stability of OCNTs/CF cathode. Besides, the hydrophilicity of OCNTs/CF cathode was significantly enhanced owing to the abundant oxygen-contained functional groups on the surface of the OCNTs/CF cathode, which facilitated the mass transfer between the OCNTs/CF cathode and the reactants in the bulk solution. To reveal the possible mechanism in electro-Fenton equipped with the OCNTs/CF cathode, quenching experiments and electron paramagnetic resonance (EPR) investigations were further conducted. This work provided valuable insights into the fabrication of the non-metallic cathode with a high ability towards H2O2 generation in electro-Fenton for efficient pollutant removal.

Anthraquinone acted as a catalyst for the removal of triphenylmethane dye containing tertiary amino group: Characteristics and mechanism.

Herein, we found that anthraquinone (AQ) acted as a catalyst for the rapid and effective removal of triphenylmethane dye containing tertiary amino group (TDAG). Results showed that AQ had an enhanced catalytic reactivity towards the removal of TDAG compared to hydro-quinone, which was further proved and explained using density functional theory (DFT) calculations. AQs could achieve a TDAG removal efficiency and rate of approximately 100% and 0.3583 min-1, respectively, within 20 min. Quenching experiments and electron paramagnetic resonance (EPR) tests indicated that the superoxide radical (O2•-) generated through the catalytic reduction of an oxygen molecule (O2) by AQ contributed to the effective removal of the TDAG. In addition, it was found that the electrophilic attack of the O2•- radical on the TDAG was the driving force for the dye degradation process. Decreasing the pH led to protonation of the substituted group of AG, which resulted in formation of an electron deficient center in the TDAG molecule (TDAG-EDC+) through delocalization of the π electron. Therefore, the possibility of the electrophilic attack for the dye by the negative O2•- radical was significantly enhanced. This study revealed that the H+ and the O2•- generated by the catalytic reduction of O2 have synergistic effects that led to a significant increase in the dye removal rate and efficiency, which were higher than those obtained through persulfate oxidation.

Release of Pb adsorbed on graphene oxide surfaces under conditions of Shewanella putrefaciens metabolism.

In this study, Pb(II) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens (S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide (GO) surfaces. The results showed that GO was transformed to its reduced form (r-GO) by bacteria, and this process induced the release of Pb(II) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(II) was stably dispersed in solution in the form of a Pb(II)-extracellular polymer substance (EPS) complex, while another portion of Pb(II) released from GO-Pb(II) was observed as lead phosphate hydroxide (Pb10(PO4)6(OH)2) precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris (OD) and elevated the content of dispersible Pb(II) in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.

Anthraquinone (AQS)/polyaniline (PANI) modified carbon felt (CF) cathode for selective H2O2 generation and efficient pollutant removal in electro-Fenton.

A novel binder-free anthraquinone (AQS)/polyaniline (PANI) modified carbon felt (CF) cathode for selective H2O2 generation and efficient pollutant removal in electro-Fenton was fabricated by CV electro-deposition method. AQS, the oxygen reduction reaction (ORR) catalyst, was immobilized by the PANI film, which contributed to the obtained high stability of the AQS/PANI@CF cathode. The concentration of the electro-generated H2O2 on AQS/PANI@CF cathode (83.3 µmol L-1) was about 10 times higher than that of the bare CF cathode. And the high yield of H2O2 was attributed to the catalytic reduction of O2 by AQS to generate more superoxide radical (O2•-), which combined with H+ to form H2O2. Additionally, the rhodamine B (RhB) degradation efficiency reached 98.8% within 60 min with the AQS/PANI@CF served as the cathode with high stability and good repeatability. The main generated reactive radicals were determined by the quenching experiments and the electron paramagnetic resonance (EPR) tests. Besides, a plausible mechanism of the AQS/PANI@CF cathode applied electro-Fenton process was proposed. This work provided a reliable reference for the subsequent investigations of the binder-free cathode with high performance and stability.

The critical contribution of oxidation debris on the acidic properties of graphene oxide in an aqueous solution.

The contribution of oxidation debris (OD) to the acidity of graphene oxide (GO) was investigated in this study. With Na2CO3 as the titrator base, the Boehm titration results showed that the total acidity of GO in an aqueous solution decreased from 9.72 to 2.74 mmol g-1 after a thorough removal of OD and that the total acidity of OD was 26.45 mmol g-1. Thermogravimetric analyses showed that the mass ratios of OD and residual graphene sheets (named bwGO) were ∼26 % and ∼73 % of the whole pristine GO, respectively. Based on the quantitative relationships between the mass ratio and acid site density, it was concluded that the total acidity of GO was equal to the sum of the acidity from bwGO and the OD contained in GO. Under alkaline conditions, the splitting and stripping of OD was attributed to the combined effect of the cleavage of H-bonds by nucleophilic attack from OH- and the electrostatic repulsion due to the ionization of carboxylic acids, in which the former became dominant when the pH shifted to neutral and weakly acidic. This study provides an explanation for the origin of GO acidity in aqueous solutions and highlights the role of OD in the chemistry of GO.

Solvent dispersion triggered the formation of NiFe-gel as an efficient electrocatalyst for enhancing the oxygen evolution reaction.

The inexpensive metal-based electrocatalysts with large surface areas are in high demand to overcome the sluggish kinetics of the anodic oxygen evolution reaction (OER) in electrocatalytic water splitting. Here we report that a series of NiFe based gels were prepared by a solvent dispersion triggered gelation method, where Ni2Fe-gel exhibits a specific surface area of 216.9 m2 g-1, and a low overpotential of 245 mV at 10 mA cm-2 in an alkaline electrolyte.

The critical role of oxidative debris in the adsorption and desorption of Pb(II) to graphene oxides under alkaline groundwater conditions.

The application of graphene oxide (GO) and its derivatives as adsorbents to remove heavy metal contaminants from industrial wastewaters has attracted increasing attention worldwide. Here, we investigated the role of oxidative debris (OD) on GO surfaces in the adsorption of Pb(II) under natural conditions. OD attached to GO surfaces can be removed under alkaline conditions, and plays a critical role in the adsorption of Pb(II) by GO. Specifically, the maximum adsorption capacity of Pb(II) on GO decreased from 926.50 to 357.64 mg·g-1 after OD removal. Under simulated natural alkaline groundwater conditions, some adsorbed Pb(II) was released with OD that was stripped from spent GO adsorbents (i.e., GO-Pb(II)). Further, batch experiments indicated that 1.30-1.43% of adsorbed Pb(II) could stably disperse in water as dissolved PbCO3 and OD-Pb(II) complexes, at a pH of ~8.3. The stripping and dissociation of OD under alkaline conditions promoted the mobility of Pb(II) on GO adsorbents. This study enhances our understanding of heavy metal transport in natural alkaline groundwater environments that contain GO particles.

Enhanced extracellular electron transfer between Shewanella putrefaciens and carbon felt electrode modified by bio-reduced graphene oxide.

Extracellular electron transfer (EET) is a governing factor for the electrochemical performance of a bioelectrochemical system (BES) such as the microbial fuel cell (MFC). Herein, an in situ method to fabricate a bio-reduced graphene oxide (GO) (br-GO) modified carbon felt electrode to increase EET was developed. GO (0.5mgmL-1) was spiked into the anode chamber in a three-electrode BES and was transformed to br-GO with a self-assembled three-dimensional (3D) structure. The response of the br-GO modified electrode potential to the attached population of Shewanella putrefaciens increased from 0.071V to 0.517V (vs Ag/AgCl). Meanwhile, br-GO modification resulted a significant enhancement in the total amount of extracellular electrons transferred between the modified electrode and microbe. The process of br-GO modification lowered the charge transfer resistance of the electrode and enhanced the EET. The modified electrode was further employed as an anode in the MFC, and consequently, the power density of the MFC was significantly enhanced. The current study not only gives a simple and effective way for improving the EET with br-GO fabrication, but also provides a strategy to enhance the power density of the MFC.

Release and transport of Pb(II) adsorbed on graphene oxide under alkaline conditions in a saturated sand column.

The use of graphene oxide (GO) adsorbents to remove Pb(II) from wastewater has attracted lots of attention, but the release of Pb(II) from Pb-laden GO in alkaline groundwater requires further investigation. The current research demonstrated that oxidative debris (OD) could be stripped gradually from the surfaces of GO in 0.01-1.0 M NaHCO3 solutions although the stripping kinetic process was very slow. Accompanied with OD detachment from GO, 5.47%-23.45% adsorbed Pb(II) on spent GO (i.e. GO-Pb(II)) was released in the form of an OD-Pb(II) complex under 0.01-1.0 M NaHCO3 conditions. OD-Pb(II) could disperse steadily in water even at pH > 7.0. The deposition and detachment of the OD in the quartz sand media were markedly affected by the ion strength of the solution, and the greater mobility of OD than GO improved the transport of OD-Pb(II) through a saturated sand column. Our results provide valuable information about the characteristics and mechanism of transport of adsorbed heavy metals on GO nanomaterials in the aqueous environment and the possible environmental risks when spent GO-based heavy mental adsorbents are discharged into natural groundwater systems.

Fate of adsorbed Pb(II) on graphene oxide under variable redox potential controlled by electrochemical method.

Lead removal using graphene oxide (GO) and GO based adsorbents has attracted increasing attention worldwide, whereas the potential release of previously adsorbed Pb(II) from GO surfaces induced by exposure to variable redox conditions is presently underappreciated. The current study revealed that reduction of GO to r-GO (the reduced form) was coupled with a decrease of oxygen-containing groups (OCGs) under reductive potential, and the maximum adsorption capacity of GO for Pb(II) decreased from 931.66 to 714.78 mg g-1 after electrochemical reduction. The release of adsorbed Pb(II) from GO-Pb(II) increased gradually when the potential dropped from 0 to -600 mV. The content of released Pb(II) decreased when the potential reached -700 mV because of the reduction of Pb(II) to insoluble Pb(0). Cyclic voltammetry (CV) analysis demonstrated that there are three reductive potentials, e.g. -760, -400, and -120 mV, related to the reduction of OCGs. X-ray photoelectron spectroscopy indicated that the reducing sequence of three OCGs, namely C-O, CO and OCO groups, depended on the applied potential. This application of an electrochemical method to investigate adsorbed Pb(II) from spent GO absorbent provides valuable information about heavy metal transportation in environments containing GO under varying redox conditions.

[Determination of 16 phthalate acid esters in infant formula by gas chromatography-tandem mass spectrometry].

A method was established for the determination of 16 phthalate acid esters (PAEs) in infant formula by gas chromatography-tandem mass spectrometry (GC-MS/MS). PAEs in infant formula samples were homogenized by deionized water, extracted with acetonitrile, and purified by a solid-phase extraction (SPE) method using primary secondary amine (PSA) sorbents. The separation was performed on a DB-5 MS UI (30 m×0.25 mm×0.25 µm) capillary column. Effects of different elution solvents on alumina/PSA and PSA SPE columns were investigated. Fair recoveries of 16 PAEs were achieved on the PSA column upon elution by mixed n-hexane-acetone (60:40, v/v). All the 16 PAEs were quantified by matrix-matched isotopic-dilution mass spectrometry (IDMS); the 16 PAEs showed linear relationships in the concentration range of 0.01-2.0 mg/kg with linear coefficients (R2) greater than 0.9996. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.15-2.5 µg/kg and 0.50-8.33 µg/kg, respectively. The recoveries of the 16 PAEs, obtained using the IDMS method, were 96.1%-104.0% with relative standard deviations (RSDs) lower than 3.3% (n=5). These results established the method described here as sensitive and precise for the simultaneous determination of 16 PAEs in infant formula, even at trace concentrations.

Water quality characteristics and corrosion potential in blending zones in X city drinking water distribution system.

Blended water, always existing in a drinking water distribution system (DWDS) with different sources, can cause some unintended results, including corrosion and/or release of corrosion by-products. Although some studies have specially focused on the blended water in DWDSs, the water quality characteristics, variations, and mechanisms for corrosion and metal release have not been fully understood. This study aims to examine the characteristics and evaluate the corrosion potential of blended water in X city DWDS using four indices of Langelier saturation index (LSI), Ryznar stability index (RSI), Puckorius scaling index (PSI), and calcium carbonate precipitation potential (CCPP). Physical and chemical analysis showed that the values of pH, total dissolved solids (TDS), sulfate (SO42-), and chloride (Cl-) in blended water were always at acceptable levels, while some free residual chlorine concentrations fell outside the regulatory standards (≥ 0.05 mg/L) with the minimum of 0.01 mg/L. Most parameters except pH varied in large ranges with maximum to minimum ratios (MMRs) over 2.25. The mean values of the LSI, RSI, PSI, and CCPP indices were - 0.44, 8.65, 8.79, and - 1.95 mg/L CaCO3, respectively, indicating that the blended water was slightly corrosive. For the three zones, Z2 had the highest mean levels of TDS (320.84 mg/L), alkalinity (188.70 mg/L CaCO3), SO42- (13.69 mg/L), Cl- (36.37 mg/L), calcium hardness (Ca2+) (28.99 mg/L), and magnesium hardness (Mg2+) (15.22 mg/L) and the lowest mean level of dissolved oxygen (DO) (6.72 mg/L). Thus, the corrosion potential in Z2 was the lowest with the LSI, RSI, PSI, and CCPP values of - 0.17, 8.11, 8.08, and 2.87 mg/L CaCO3, respectively. During a year, the corrosion in blended water was more serious in winter with the LSI, RSI, PSI, and CCPP indices of - 0.79, 9.25, 9.37, - 7.54 mg/L CaCO3, respectively. The water corrosivity reached the minimum level in summer (LSI - 0.12, RSI 8.05, PSI 8.03, and CCPP 5.22 mg/L CaCO3) owing to the decrease of DO concentrations and the increase of temperature and groundwater supplies with higher alkalinity. During rainy season, the concentrations of TDS, alkalinity, SO42-, Cl-, Ca2+, and Mg2+ in blended water were reduced by 41.05%, 40.48%, 35.83%, 47.48%, 23.47%, and 55.73%, respectively, resulting in the increase of water corrosivity. More decreases of water parameters were recorded in Z2 (TDS, 221.80 mg/L; alkalinity, 139.50 mg/L CaCO3; SO42-, 9.97 mg/L; Cl-, 13.74 mg/L; Ca2+, 7.10 mg/L; and Mg2+, 11.37 mg/L), because most groundwater from No. 5 WTP was pumped paretic water with more variations of water quality by rainfall. Moreover, it was suggested that Mg2+ should be considered in the corrosion indices, and the corrosion tendency of blended water could be reduced by adjusting the levels of pH, alkalinity, Ca2+, and Mg2+. The results of this research may pave the way for several opportunities to improve the management and corrosion prevention of blended water.

Characteristics and Kinetic Analysis of AQS Transformation and Microbial Goethite Reduction:Insight into "Redox mediator-Microbe-Iron oxide" Interaction Process.

The characteristics and kinetics of redox transformation of a redox mediator, anthraquinone-2-sulfonate (AQS), during microbial goethite reduction by Shewanella decolorationis S12, a dissimilatory iron reduction bacterium (DIRB), were investigated to provide insights into "redox mediator-iron oxide" interaction in the presence of DIRB. Two pre-incubation reaction systems of the "strain S12- goethite" and the "strain S12-AQS" were used to investigate the dynamics of goethite reduction and AQS redox transformation. Results show that the concentrations of goethite and redox mediator, and the inoculation cell density all affect the characteristics of microbial goethite reduction, kinetic transformation between oxidized and reduced species of the redox mediator. Both abiotic and biotic reactions and their coupling regulate the kinetic process for "Quinone-Iron" interaction in the presence of DIRB. Our results provide some new insights into the characteristics and mechanisms of interaction among "quinone-DIRB- goethite" under biotic/abiotic driven.

The characteristics and two-step reaction model of p-nitroacetophenone biodegradation mediated by Shewanella decolorationis S12 and electron shuttle in the presence/absence of goethite.

The current study mainly focused on the biodegradation process of p-nitroacetophenone (NP) in the presence and absence of goethite mediated by iron-reducing microbe (Shewanella decolorationis S12) and electron shuttle. The results showed that introduction of electron shuttle could obviously lead to an accumulation of biodegradation intermediate, especially in reaction systems containing high content of electron shuttle in the absence of goethite. Goethite could enhance the degree and rate of NP biodegradation. The microbial reductively generated Fe(II) played an active role in the biodegradation process. The relationship between the concentrations of biodegradation end product and the reaction times could be fitted by a consecutive reaction model with correlation coefficients (adjusted R(2)) in the range from 0.9241 to 0.9831 during the biodegradation stage from the beginning to about 250 h of incubation. However, during the subsequent biodegradation stages, in the presence and absence of goethite, transitions from the consecutive reaction model to zero-order reaction model and from the consecutive reaction model to exponential growth reaction model were observed, respectively. The newly proposed two-step reaction model will help understand the mechanism of the biodegradation process of nitroaromatic compounds and related pollutants.

A new method of inhibiting pollutant release from source water reservoir sediment by adding chemical stabilization agents combined with water-lifting aerator.

Source water reservoirs easily become thermally and dynamically stratified. Internal pollution released from reservoir sediments is the main cause of water quality problems. To mitigate the internal pollution more effectively, a new method, which combined chemical stabilization with water lifting aerator (WLA) technology, was proposed and its efficiency in inhibiting pollutant release was studied by controlled sediment-water interface experiments. The results showed that this new method can inhibit pollutant release from sediment effectively. The values of mean efficiency (E) in different reactors 2#-5# (1# with no agent, 2# 10 mg/L polymeric aluminum chloride (PAC) was added, 3# 20 mg/L PAC was added, 4# 30 mg/L PAC was added, 5# 20 mg/L PAC and 0.2 mg/L palyacrylamide (PAM) were added) for PO4(3-) were 35.0%, 43.9%, 50.4% and 63.6%, respectively. This showed that the higher the PAC concentration was, the better the inhibiting efficiency was, and PAM addition strengthened the inhibiting efficiency significantly. For Fe2+, the corresponding values of E for the reactors 2#-5# were 22.9%, 47.2%, 34.3% and 46.2%, respectively. The inhibiting effect of PAC and PAM on Mn release remained positive for a relatively short time, about 10 days, and was not so effective as for PO4(3-) and Fe2+. The average efficiencies in inhibiting the release of UV254 were 35.3%, 25.9%, 35.5%, 38.9% and 39.5% for reactors 2#-5#, respectively. The inhibiting mechanisms of the agents for different pollutants varied among the conditions and should be studied further.

[The influence of the redox conditions on the three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy of the dissolved organic matter (DOM) in the overlying water].

In the present study three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy was applied to characterize the dissolved organic matter (DOM) in the overlying water under aerobic and anaerobic condition. The effects of redox condition were significant on 3DEEM fluorescence spectra of DOM, and in the aerobic condition, the peak intensities of protein-like fluorophores were both higher than those of the humic-like fluorophores, however, the phenomenon of the oxidative degradation of humic-original DOM could be seen. While in anaerobic condition, the peak intensities of the humic-like fluorescence were increased with increasing the incubation time. After the 21 day anaerobic incubation, the peak intensities of the humic-like fluorescence can be as 3.51 and 3.78 times higher than those of protein-like fluorescence. The differences in the DOM fluorescence parameters, e.g., peak intensities, locations and fluorescence index, indicate the difference in the chemical structures and various origins of the DOM in the overlying water between sediment-water interfaces.

[Separation of geometrical isomers of {Fe [3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine]3} 2+ ([Fe(PDT)3] 2+) using ion-pair reversed-phase high performance liquid chromatography].

A method has been developed for the separation of two geometrical isomers of the {Fe[3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine]3}2+([Fe(PDT)3]2+) using ion-pair reversed-phase high performance liquid chromatography (RP-HPLC). The effects of the chromatographic conditions, such as the content of acetonitrile and the type and concentration of the ion-pair reagents (sodium perchlorate (NaClO4) or sodium dodecyl sulfate (SDS)) in the binary mobile phase (acetonitrile and water), on the retention factor (k), resolution, and selectivity were iscussed. It was found that no matter how the ion-pair reagent was NaClO4 or SDS at different concentrations, the acetonitrile content in the mobile phase has good linear regression equations with the ln k of the two isomers. It was also observed that SDS showed more positive effect on the k of the two geometrical isomers than that of NaClO4. Moreover, the separation of the two isomers in the ternary mobile phase (acetonitrile, methanol and water) was developed. The chromatographic conditions, including the content of the organic modifier (acetonitrile and methanol) and the type and concentration of the ion-pair reagents (SDS and NaClO4), were optimized. Two geometrical isomers were rapidly and successfully separated under the optimized conditions, which used acetonitrile/methanol/water (20: 50: 30, v/v/v) as the mobile phase and 60 mmol/L NaClO4 as the ion-pair reagent. Good linear regression equations between the peak areas and concentrations for the two isomers were obtained. The detection limits of the fac-isomer and mer-isomer were 4.28 and 3.44 ng/mL (S/N = 3), respectively.