Cationic Red GTL Research Articles

Fe2O3-CeO2-Bi2O3/γ-Al2O3 catalyst in the catalytic wet air oxidation (CWAO) of cationic red GTL under mild reaction conditions

The Fe2O3-CeO2-Bi2O3/γ-Al2O3 catalyst, a novel environmental-friendly material, was used to investigate the catalytic wet air oxidation (CWAO) of cationic red GTL under mild operating conditions in a batch reactor. The catalyst was prepared by wet impregnation, and characterized by special surface area (BET measurement), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Fe2O3-CeO2-Bi2O3/γ-Al2O3 catalyst exhibited good catalytic activity and stability in the CWAO under atmosphere pressure. The effect of the reaction conditions (catalyst loading, degradation temperature, solution concentration and initial solution pH value) was studied. The result showed that the decolorization efficiency of cationic red GTL was improved with increasing the initial solution pH value and the degradation temperature. The apparent activation energy for the reaction was 79 kJ·mol–1. Hydroperoxy radicals (HO2·) and superoxide radicals (O2–·) appeared as the main reactive species upon the CWAO of cationic red GTL.

Novel-structured Mo-Cu-Fe-O composite for catalytic air oxidation of dye-containing wastewater under ambient temperature and pressure

AbstractA novel-structured Mo-Cu-Fe-O composite was successfully prepared by co-precipitation and impregnation method. The properties of the as-prepared samples were determined using X-ray diffraction, temperature-programmed reduction by H2, cyclic voltammetry, and temperature-programmed desorption by O2. The results showed that Mo6+ diffused into the Cu-Fe-O crystal lattice and then formed a new crystalline phase of CuMoO4. The Mo-Cu-Fe-O catalyst had redox properties, and its surface contained active sites for oxygen adsorption. In addition, the catalytic activity of the Mo-Cu-Fe-O composite was evaluated by the degradation of Cationic Red GTL, Crystal Violet, and Acid Red in catalytic wet air oxidation (CWAO) at ambient temperature and pressure. The Mo-Cu-Fe-O catalyst showed excellent activity at basic conditions for the degradation of Cationic Red GTL. High removal efficiencies of 91.5% and 92.8% were achieved for Cationic Red GTL and Crystal Violet, respectively, in wastewater, and the efficiency remained high after seven cycles. However, almost no degradation of Acid Red occurred in the CWAO process. Furthermore, hydroxyl radicals were formed in the CWAO process, which induced the decomposition of the two cationic dyes in wastewater, and the toxicity of their effluents was decreased after degradation. The results indicate that the Mo-Cu-Fe-O composite shows excellent catalytic activity for the treatment of wastewater contaminated with cationic dyes.

Synthesis of Na2Mo4O13α/-MoO3 Hybrid Material Using Different Sodium Precursors for the Degradation of Cationic Red GTL

Synthesis of Na<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB><I>α</I>/-MoO<SUB>3</SUB> Hybrid Material Using Different Sodium Precursors for the Degradation of Cationic Red GTL

The influence of Na species addition on the synthesis and catalytic activity of Na2Mo4O13/α-MoO3 as CWAO catalyst

The influence of added Na species amount on the formation of Na2Mo4O13/α-MoO3 hybrid catalysts and their catalytic wet air oxidation activity for the degradation of cationic red GTL at ambient conditions were systematically investigated. The structure and morphology of the catalyst precursors and the final Na2Mo4O13/α-MoO3 hybrid catalysts were examined using XRD and SEM analyses, which suggested that the active catalyst Na2Mo4O13/α-MoO3 with nanofiber morphology could be obtained in a much wider pH range by adding more Na species. The influence of some key parameters including reaction time, the volume of dye wastewater, testing temperature, and calcination temperature were evaluated. The mechanism involved was also explored using UV–vis and ESR analyses, which suggested that the benzene ring and azo linkage of dye molecules could be destroyed within 30–45min and the formation of OH radicals is critical for the high activity. By adding more Na species, the removal of both total organic carbon (TOC) and chemical oxygen demand (COD) could also be accelerated. Cycling tests suggested that the catalysts were very robust, and the degradation efficiency was still 99.6–99.9% even after 5 cycles.

Synthesis, characterization, and catalytic activity of alkali metal molybdate/α-MoO3 hybrids as highly efficient catalytic wet air oxidation catalysts

To develop new catalysts which can be used in catalytic wet air oxidation (CWAO) with ambient temperature and atmospheric pressure, a series of M2Mo4O13/α-MoO3 (M=Li, Na or K) hybrid catalysts for cationic red GTL removal were synthesized by a facile hydrothermal method. The growth of crystals under different synthesis pH and the phase evolution during thermal treatment were carefully monitored using various analytical tools. The influence of synthesis pH, calcination temperature, reaction temperature, degradation time, and bubbling with air or N2 on the decolorization efficiency, and the removal rates of total organic carbon (TOC) and chemical oxygen demand (COD) were systematically investigated. For all three catalysts, approximately 100% of color and over 93% of TOC could be removed within 30min. Compared to many catalysts reported in literature, these novel catalysts showed higher catalytic activity in dye wastewater degradation. The catalytic activity tests in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy-N-oxyl (TEMPO) and the electron spin resonance (ESR) analysis suggested that the existence of M2Mo4O13 (M=Li, Na or K) promotes the formation of OH radicals and is critical for their superior catalytic activity. Considering the ambient operating condition and the excellent catalytic activity, these novel CWAO catalysts are very promising for practical applications.

Novel Na₂Mo₄O₁₃/α-MoO₃ hybrid material as highly efficient CWAO catalyst for dye degradation at ambient conditions.

We report a novel hybrid material Na2Mo4O13/α-MoO3 as highly efficient catalytic wet air oxidation (CWAO) catalyst, which showed the highest ever activity at room temperature and atmosphere pressure for the degradation of cationic red GTL. SEM and TEM analyses indicated that this hybrid catalyst has bamboo-shaped nanofiber morphology. In view of practical applications, the influence of some key parameters including operation temperature, catalyst calcination temperature, and the volume of dye wastewater have been optimized. The mechanism for the superior catalytic performance was investigated. XRD, XPS, and ESR suggested the Na2Mo4O13/α-MoO3 hybrid catalyst possesses more O2− ions in the oxygen deficient regions than neat α-MoO3, promoting the formation of active ·OH radicals and resulting in a higher activity. Considering the facile preparation and its superior activity, this novel catalyst is promising for practical dye wastewater treatment.

Catalytic mechanism of cationic red GTL at wide pH using the Mo-Zn-Al-O nanocatalyst under room conditions.

Catalytic mechanism of cationic red GTL at wide pH using the Mo-Zn-Al-O nanocatalyst under room conditions was investigated. The experimental results indicate that initial pH significantly affected the removal of cationic red GTL, the removal of COD, the pH value and residual oxygen in the reaction. In the range of pH value from 4 to 10, decolorization of cationic red GTL was almost above 90%. COD removal efficiency was enhanced with the decrease of pH in CWAO process and 79% of the COD was removed at pH 4.0, whereas only 57% COD removal was observed at pH 10.0. The terminal pH was in the range of 5.0-6.0 and the highest terminal concentrations of aqueous oxygen with 5.5 mg/L were observed at pH = 4.0. The radical inhibition experiments also carried out and the generation of *OH and 1O2 in catalytic wet air oxidation process were detected. It was found that the degradation of cationic red GTL occurs mainly via oxidation by 1O2 radical generated by Mo-Zn-Al-O nanocatalyst under acid conditions and *OH radical under alkaline conditions.

Study on coupling with catalytic wet air oxidation and membrane separation in the treatment of cationic red GTL

Coupling with the advantages of catalytic wet air oxidation (CWAO) and membrane separation under room condition, a new type of integrated fluidized-bed reactor was designed, with a PVDF hollow fiber membrane module submerged in. Its performance was investigated by the simulation of catalytic degrading cationic red GTL wastewater with initial concentration of 50 mg/L. The experimental results showed that the decolorization of cationic red GTL rose with the increase in residence time, the dosage of Mo/Zn/Al/O catalysts and aeration intensity, whereas it decreased against the increase in pH value. The optimal conditions of residence time catalyst dosage, pH value, and aeration intensity were 1.5 h, 1.5 g, 4, and 0.036 m3/h, respectively. The decolorization efficiency was above 98%, and TOC removal efficiency was more than 67%, which were apparently superior to the performance of single CWAO process in the batch test, and moreover, the interception efficiency on catalyst was approximately 100%. It can be found from the FT-IR analysis of original influent and effluent of membrane that the bonds of C=C, C–N as well as N=N were destroyed, while new bonds of C=O, –NO3, and N–H were formed. The BOD/COD ratio of the treated effluent been improved from 0.05 to 0.41.

Degradation of Cationic Red GTL by Catalytic Wet Air Oxidation over Mo–Zn–Al–O Catalyst under Room Temperature and Atmospheric pressure

To overcome the drawback of catalytic wet air oxidation (CWAO) with high temperature and high pressure, the catalytic activity of Mo-Zn-Al-O catalyst for degradation of cationic red GTL under room temperature and atmospheric pressure was investigated. Mo-Zn-Al-O catalyst was prepared by coprecipitation and impregnation. XRD, TG-DTG, and XPS were used to characterize the resulting sample. Central composition design using response surface methodology was employed to optimize correlation of factors on the decolorization of cationic red GTL. The results show that the optimal conditions of pH value, initial concentration of dye and catalyst dosage were found to be 4.0, 85 mg/L and 2.72 g/L, respectively, for maximum decolorization of 80.1% and TOC removal of 50.9%. Furthermore, the reaction on the Mo-Zn-Al-O catalyst and degradation mechanism of cationic red GTL was studied by Electron spin resonance (ESR) and GC-MS technique. The possible reaction mechanism was that the Mo-Zn-Al-O catalyst can efficiently react with adsorbed oxygen/H(2)O to produce ·OH and (1)O(2) and finally induce the degradation of cationic red GTL. GC-MS analysis of the degradation products indicates that cationic red GTL was initiated by the cleavage of -N ═ N- and the intermediates were further oxidized by ·OH or (1)O(2).

Structure and catalytic activity of Mo[sbnd]Zn[sbnd]Al[sbnd]O catalyst for degradation of cationic red GTL under room conditions

A series of MoZnAlO catalysts with different Zn/Al molar ratios were prepared. The structure of the catalysts was characterized using ICP-OES, zeta potential, XRD, BET, FTIR, H2-TPR, O2-TPD and ESR. The catalytic activity of these catalysts on the degradation of cationic red GTL wastewater under room condition was investigated. The experimental results showed that the highest color removal efficiency and TOC removal efficiency of cationic red GTL can reach 90.9% and 65.8% by the MoZnAlO catalyst with 1:1 of Zn/Al molar ratio respectively. Associated with the characterization results of these catalysts, MoZnAlO catalyst with 1:1 of Zn/Al molar ratio with highest catalytic activity could be contributed to its lowest zeta potential, largest specific surface area, special crystalline phases, special Mo valences, largest number of active adsorption sites and the maximum active species of 1O2 or OH. The stable of these catalysts was also studied. Due to the lower leaching concentrations of Zn, Mo and Al, MoZnAlO catalyst with Zn/Al molar ratio from 1:1 to 1:3 has a good stability. It is thought that Al3+ plays a more important part in determining the distance between metals, thus it affects the leaching of metals.

Removal and recovery of cationic dyes from aqueous solutions using spherical sulfonic lignin adsorbent

AbstractA novel spherical sulfonic lignin adsorbent, denoted as SSLA, was adopted to removal and recover the cationic dyes from aqueous solutions, e.g., Cationic Red GTL, Cationic Turquoise GB, and Cationic Yellow X‐5GL, and various affecting factors were optimized. It was found that the adsorption of cationic dyes on the adsorbent was initially concentration‐ and temperature‐dependent, and followed both the Freundlich and Langmuir isothermal adsorption. The positives values for ΔH indicated that the process was endothermic. The breakthrough adsorption capacities for GTL, GB, and X‐5GL were 536.0, 550.0, and 582.0 mg/g, respectively, which prevailed over the commercial powdered activated carbon and strongly acidic cation‐exchange resin R732 evidently. Additionally, the maximum recovery percentage could reach 93.2, 97.1, and 96.5% separately for GTL, GB, and X‐5GL, when a mixture of 3.0 mol/L HCl and alcohol with the volume ratio of 1 : 4 was adopted as eluant. Moreover, the results of the mobile desorption and recovery tests indicated that the maximum concentrations of GTL, GB, and X‐5GL in the eluants could reach 13,108, 13,980, and 13,520 mg/L, respectively. Only 6.3, 5.0, and 4.6% of adsorption capacities for GTL, GB, and X‐5GL decreases individually after 20 replicates of adsorption and desorption. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2284–2291, 2006

Photocatalytic degradation of a cationic azo dye by TiO 2/bentonite nanocomposite

Titanium dioxide/bentonite clay nanocomposite prepared by acid-catalyzed sol–gel method was used as photocatalyst in the reaction of cationic azo dye decomposition in water. The incorporation of TiO 2 was confirmed by powder X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS). The photocatalytic activity of those nanocomposite photocatalysts was much higher than that of the pure titanium dioxides. The nanocomposite created a kinetic synergy effect in Cationic Red GTL (GTL) disappearance with an increase of the rate constant by a factor of 2.57 for neat TiO 2 (P-25). The photo-activities were greatly dependent on the solution pH, and it was more effective for GTL to be degraded under alkaline condition. That was likely to contribute for the acid–base equilibria on the surface of the nanocomposite. Results also indicated that the proper addition of hydrogen peroxide could improve the decolorization rate, but the excess hydrogen peroxide could quench the formation of OH.