del Rio, A. V., Stachurski, A., Mendez, R., Campos, J. L., Surmacz-Gorska, J., & Mosquera-Corral, A. (2017). Short- and long-term orange dye effects on ammonium oxidizing and anammox bacteria activities. Water Sci. Technol., 76(1), 79–86.
Abstract: The effects of orange azo dye over ammonia oxidizing bacteria (AOB) and anammox bacteria activities were tested. Performed batch tests indicated that concentrations lower than 650 mg(orange)/L stimulated AOB activity, while anammox bacteria activity was inhibited at concentrations higher than 25 mg(orange)/L. Long-term performance of a continuous stirred tank reactor (CSTR) for the partial nitritation and a sequencing batch reactor (SBR) for the anammox process was tested in the presence of 50 mg(orange)/L. In the case of the partial nitritation process, both the biomass concentration and the specific AOB activity increased after 50 days of orange azo dye addition. Regarding the anammox process, specific activity decreased down to 58% after 12 days of operation with continuous feeding of 50 mg(orange)/L. However, the anammox activity was completely recovered only 54 days after stopping the dye addition in the feeding. Once the biomass was saturated the azo dye adsorption onto the biomass was insignificant in the CSTR for the partial nitritation process fed with 50 mg(orange)/L. However, in the SBR the absorption was determined as 6.4 mg(orange)/g volatile suspended solids. No biological decolorization was observed in both processes.
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Shanmugaraj, K., Vinoth, V., Pugazhenthiran, N., Valdes, H., Salvo, C., Sepulveda, E., et al. (2023). Ferrihydrite- Graphene oxide foams as an efficient adsorbent for Arsenic (III) removal from an aqueous solution. Inorg. Chem. Commun., 153, 110892.
Abstract: We report the synthesis of a new range of ferrihydrite-graphene oxide (FH-GO) foams using chitosan as cross linker, with varying iron content (5 wt%, 10 wt%, and 20 wt% of FH) as highly efficient adsorbents for the removal of arsenic (III) (As(III)) in an aqueous solution. The sonochemical methods were adopted to synthesize various FH-GO foams and were further characterized by XRD, SEM, TEM, FTIR, Raman, and XPS techniques. The synthesized materials were used for the removal of As(III) in both batch and fixed bed absorbent column methods. The adsorption isotherm results showed that the 10 wt% of FH-GO foams demonstrated a superior adsorbent for the As(III) with high adsorption capacities than that of the other two FH-GO foams (5 wt% and 20 wt% of FH). Moreover, 10 wt% of FH-GO foams was also demonstrated to be nearly a complete (>98.4%) removal of As(III) ions at neutral pH 7. The adsorption isotherm fitted very well with the Langmuir model with the highest accuracy data for all the synthesized adsorbent materials. In addition, the fixed bed absorbent column method was also adopted for the removal of As(III) ions in the water sample, which showed > 99.2% of removal efficiency. The outstanding adsorption capabilities, along with their easy and low-cost synthesis, make these kinds of adsorbents extremely capable for commercial applications in wastewater treatment and drinking water purification.
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Suresh, R., Alvarez, A., Sandoval, C., Ramirez, E., Santander, P., Mangalaraja, R. V., et al. (2023). Fe2O3/NiO nanocomposites: synthesis, characterization and roxarsone sensing by Fourier transform infrared photoacoustic spectroscopy. New J. Chem., 47(27), 12806–12815.
Abstract: The Fe2O3/NiO nanocomposite was prepared through facile mixing of pure Fe2O3 and NiO nanoparticles. Pure metal oxides were synthesized by the glycine aided hydrothermal method. The crystal structure was determined by X-ray diffraction (XRD) analysis. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) clearly show that the NiO nanospheres were homogeneously distributed on Fe2O3 nanoplates. Fourier transform infrared (FTIR) spectra reveal that functionalization by glycine induces carboxylic and amino groups on the surface of nanoparticles. The optical properties such as light absorption behavior and band gap of the Fe2O3/NiO nanocomposite were determined by UV-Visible diffuse reflectance spectroscopy (DRS UV-Vis). The roxarsone (ROX) sensing behavior of the Fe2O3/NiO nanocomposite was evaluated by using Fourier transform infrared (FTIR) – photoacoustic spectroscopy (PAS) that allowed quantitative sensing of the ROX@Fe2O3/NiO complex. The photoacoustic signals of ROX were clearly observed in the FTIR-PAS spectra, particularly in the range of 1700 to 1000 cm(-1) without spectral interference from the composite. Furthermore, principal component analysis (PCA) and partial least square (PLS) regression models were applied to calibrate and validate ROX quantification. The PLS model exhibited the best performance in predicting the ROX concentration through ROX@Fe2O3/NiO samples. This proof of concept suggests that the Fe2O3/NiO nanocomposite has improved adsorption and spectral features by FTIR-PAS for sensing of organometallic compounds such as ROX.
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