Papers by Keyword: Congo Red

Abstract: Cyclodextrin metal-organic frameworks (CD-MOFs) are synthesized from green precursors, making them an ideal material for green adsorbents. However, CD-MOFs are unstable in water, thus limiting their applications. Here, we report encapsulating CD-MOFs in polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) polymeric support to produce PAN/PVP/CD-MOF composite beads. Batch adsorption studies showed that high dye adsorption capacities could be obtained at intermediate PVP, high PAN, and low CD-MOF loadings. Maximum MB and CR sorption capacities under optimum bead formulation: PAN = 6.96 wt.%, PVP = 2.20 wt.%, and CD-MOF = 2.88 wt.%. The optimized composite beads have a sorption capacity of 37.40 mg/g for MB and 18.42 mg/g for CR. We showed that PAN/PVP/CD-MOF composite beads could be an excellent adsorbent for textile dye removal in water.

Abstract: One step polyacrylamide gel method was used to synthesize the ZnO/MgO adsorbents and the adsorption behavior with Congo red (CR) from wastewater was extensively investigated. Various advanced techniques were applied to confirm the ZnO/MgO adsorbents consist of Zn, C, Mg and O elements and do not contain any other impurity elements. With the increase of MgO content, the morphology of ZnO/MgO adsorbent changes from the agglomeration of large particles to evenly dispersed fine particles and then to icicle structure. Results demonstrated that the adsorption process of ZnO/MgO adsorbents was significantly affected by the change in initial dye solution pH, initial adsorbent dosage, contact time and reaction temperature. The optimum pH, adsorbent dosage, contact time and reaction temperature is 9.81, 2 g /L, 65 min and 293 K, respectively. The maximum adsorption capacity of ZnO/MgO (nZnO:nMgO = 8:2) adsorbents (295.138 mg/g) for the adsorption of CR dye was approximately double that of previous reports (125 mg/g). The adsorption equilibrium data are well fitted by the Freundlich and Langmuir isotherm models. Thermodynamic studies indicate that the adsorption process of ZnO/MgO adsorbents is an exothermic process. Based on the experimental and theoretical analysis, the adsorption mechanism for the ZnO/MgO adsorbents consisted of hydrogen bonding, n-π interaction and electrostatic interaction. The present work pioneers the potential application of ZnO/MgO adsorbents for the adsorption of CR dye and further provides experimental evidence for the synthesis of other adsorbents.

Abstract: The photo-catalytic degradation of Congo red (CR) was examined in presence of visible light at various operating condition, pH and amount of catalyst and time. The CR dye degradation rate was 97% about 80 minute of exposure, respectively, indicating that pH 7 was the optimal pH for degradation. The photo degradation processes of dyes were considered to be connected to a kinetic models, which was later shown incorrect. The effective degradation process might be used to explain the degradation of congo red dye.

Abstract: We investigated the fabrication of Ca/Al layered double hydroxide (LDHs) via a one-step hydrothermal approach with slow hydrolysis of urea at a low temperature without further annealing required. The as-synthesized Ca/Al LDHs nanostructures obtained were defined using Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results demonstrated that Ca/Al LDHs exhibit excellent adsorption performance on Congo red anionic dyes in aqueous solution. The adsorption capacity of the Ca/Al LDHs toward Congo red was found to be 59.41 mg/g.

Abstract: Mesoporous boehmite (γ-AlOOH) was synthesized from naturally occurring coal-bearing kaolinite (CBK) by direct sulfuric acid leaching and hydrothermal method to explore a new possible route to the synthesis of product with high value added using the CBK. The Brunauner-Emmett-Teller (BET) surface area and the average crystallite size of the γ-AlOOH powder could be controlled in the range from 6.3 to 192.5 m² g^-1 and from 5.5 to 14.4 nm, respectively, by varying the reaction temperature and reaction time. Owing to its porous structure and high surface area, the synthesized mesoporous γ-AlOOH powder exhibited better adsorption abilities for CR and fluoride in contrast to commercial boehmite, and it only took 20 min to reach removal efficiency of 99.6% for CR and 90.5% for fluoride, when the initial concentration of CR and fluoride was 100 and 10 mg L^-1, respectively.

Abstract: A novel lanthanum/modified fly ash (La/MFA) composite adsorbent prepared by simple solution reaction was used for the adsorption of Congo Red (CR) dye from aqueous solution. The morphology and particle size distribution of the composite were characterized, and the equilibrium adsorption was researched. The results show that the adsorption of CR onto La/MFA can reach equilibrium in 30 minutes. The entire adsorption process can be well described by pseudo-second-order kinetic equation at different temperatures. The value of apparent adsorption activation energy is 16.2kJ/mol. The isothermal data conform to the Langmuir model with the maximum adsorption capacity of 714 mg/g at 298K. According to the negative values of Gibbs free energy change (ΔG°) and enthalpy change (ΔH°), and reduction of Langmuir adsorption coefficient with the increase of temperature, the adsorption system from 298K to 328K is confirmed to be of spontaneous and exothermic nature. The results of SEM and particle size analysis indicate that the particle sizes and specific surface of La/MFA are smaller and coarser than those of FA. As a low-value composite adsorbent, La/MFA is especially effective for the removal of high concentration CR.

Abstract: Bi₂O₃ nanostructures were synthesized through a simple electrolysis based oxidation using NaOH electrolyte and annealed at 300 °C, 400 °C, 500 °C and 600 °C. The obtained Bi₂O₃ nanostructures were characterized using X-ray diffraction and photoluminescence spectroscopy (PL). Bi₂O₃ crystal structure was confirmed by XRD. When free electron and holes are combined together then emission signals are emitted from PL spectra. With this process, it is studied about the recombination and separation of photo generated holes and electrons. The photocatalytic activities of Bi₂O₃ films were evaluated for the degradation of Congo red in aqueous solution under UV light irradiation. Among the four samples, Bi₂O₃ films annealed at 300 °C have better efficiency in removing the congo red dye. For Bi-3, the initial concentration of 10 ppm decreases to 1.11 ppm after 420 min.

Abstract: The present study evaluates the photocatalytic degradation of congo red as a model of organic pollutant over LaFe- and CeFe-codoped ZnO nanoparticles under UV light irradiation. Both photocatalysts were synthesized using co-precipitation method and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, diffuse reflectance spectroscopy. The photodegradation efficiency of congo red using two 20W UV lamp was higher for LaFe-codoped ZnO nanoparticles compared with CeFe-codoped ZnO nanoparticles. Photocatalytic mechanism was investigated by measuring the photocatalytic degradation rate in the presence of ammonium oxalate, natrium sulfate, tert-butyl alcohol as photogenerated holes, photogenerated electrons and hydroxyl radical species scavenger. The results revealed that electrons are the main species in the photocatalytic process.

Abstract: Fly ash/CeO₂ composite (FA/CeO₂) was prepared by acid modification and precipitation method using a low-cost waste fly ash (FA) as a raw material and characterized by X-ray diffraction (XRD) and the BET surface analysis. The adsorption of FA and FA/CeO₂ for Congo Red (CR) from simulated dye wastewater was studied. The different regeneration methods for the CR-saturated FA/CeO₂ were investigated. The results show that the adsorption capacity and removal rate of CR on FA/CeO₂ can respectively reach 175.35mg/g and 97.42%, 4.5 times higher than those on FA. The adsorption process of FA/CeO₂ for CR at different temperatures (25°C~55°C) can well be described by the pseudo-second-order adsorption model and is mainly controlled by intraparticle diffusion. The adsorption rate decreased slightly with increasing temperature, and the obtained adsorption apparent activation energy is 15.08kJ/mol. This indicates that CR is easily adsorbed on FA/CeO_2, and the adsorption of the process is mainly physical adsorption with exothermic nature. The room temperature is favorable to the adsorption and actual operation. NaOH solution of 0.01 mol/L can make CR-saturated FA/CeO₂ regenerated three times, and corresponding removal rate for CR can reach 97.82%, 80.21% and 66.04%, respectively. As a new kind of low-cost and high-efficient adsorbent, FA/CeO₂ composite has the potential value in the application of wastewater treatment.

Abstract: Series of silicon-substituted hydroxyapatite were prepared and characterized, and their ability to degrade methyl orange and Congo red in aqueous solutions were studied. The effect of substituted silicon amount on the photocatalytic degradation efficiency of the dyes was investigated. The substitution of SiO₄⁴⁻ groups for PO₄³⁻ groups caused OH⁻ loss and difference in the microstructure of hydroxyapatite, and the elimination rates of silicon-substituted hydroxyapatite decreased with the increasing of substituted silicon amount compared to that of pure hydroxyapatite.