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In the present article, the synthesis of TiO2/diazonium/graphene oxide and its photocatalytic activity for methylene blue (MB) degradation have been demonstrated. The functionalization of graphene oxide (GO) with diazonium salt (diazonium-GO) was conducted for enhancing the dispersibility of GO in distilled water. TiO2 was highly dispersed in diazonium-GO to form TiO2/diazonium/graphene. The obtained specimens were characterized by X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, UV-Vis spectroscopy, scanning electron microscope, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was found that the TiO2 phase in TiO2/diazonium/GO composites can be controlled by adjusting the amount of ethanol or titanium oxide in the reactant mixture. The obtained composites exhibited photocatalytic activities for methylene blue degradation (MB). The composite with ac. 70% anatase can provide the highest MB degradation efficiency. The studying of some intermediates for MB photocatalytic degradation using LC-MS showed that structure of MB by the cleavage and oxidation of one or more of the methyl group substituent on the amine groups lead to form compounds with low molecular masses. Total organic carbon studies confirmed a complete mineralization of MB. The present catalyst was stable and recyclable after three times with a negligible loss of catalytic activity. In addition, the TiO2/diazonium/GO can also photocatalyze for the degradation of some other dyes (phenol, methyl red, and Congo red).

In this paper, the synthesis of nickel ferrite and its use for voltammetric determination of uric acid (UA) are presented. Nickel ferrite was synthesized via a hydrothermal process using spherical carbons as hard template followed by calcination at 500 °C. It was found that iron and nickel compositions in nickel ferrite can be controlled by the initial Fe/Ni molar ratio. The stoichiometric nickel ferrite (NiFe2O4) with hollow spherical morphology was obtained from a reaction mixture with Fe/Ni molar ratio of around 1.2–1.5. Glassy carbon electrode modified with nickel ferrite was employed to quantitatively determine UA by different pulse voltammetric method. Under the optimum conditions, the anodic peak current was linearly proportional to UA concentration in the range of 0.398 to 6.761 μM. The detection limit (3σ) was found to be 0.15 μM. The proposed method has been employed to determine UA in human urine samples with acceptable recoveries of 95.15–104.8%. On the other hand, the results obtained from this method were also compared with that from standard HPLC method, showing no statistical difference.

In the present article, the synthesis of zeolite imidazolate framework-67/reduced graphene oxide (ZIF-67/rGO) and voltammetric determination of Rhodamine B (RhB) are demonstrated. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption/desorption isotherms. It was found that the ZIF-67/rGO composite consists of ZIF-67 nano-particles highly dispersed on the rGO matrix and possesses a high specific surface area. Because of the synergistic effect of good conductivity of rGO and high surface area of ZIF-67, the ZIF-67/rGO—modified glassy carbon electrode exhibits good electrochemical behavior toward Rhodamine B (RhB) oxidation. The use of this electrode to quantitate RhB with differential pulse voltammetric method was successful with a broad linear range, from 0.96 to 44.07 μg.L-1 of RhB and a low limit of detection of 1.79 μg.L-1. The procedure was able to be applied to quantitatively determine RhB content in several food samples with an exceptional recovery rate (98-103%). The quantitative results highly agreed with that provided by high-performance liquid chromatography, revealing that this material is promising in in situ monitoring of other illegal additives in food.

The synthesis and degradation of methyl orange (MO) in an ultraviolet-assisted heterogeneous Fenton-like process via the iron terephthalate (MIL-53) catalyst are demonstrated. MIL-53 material was characterized by means of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectra (DR-UV-Vis), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherms. It was found that the obtained material shares an identical pattern of the MIL-53 structure with high crystallinity and also demonstrates the mesoporous phase with a pore diameter of around 4.2 nm and specific surface area, SBET, of 88.2 m2·g−1. MIL-53 with UV irradiation exhibits high catalytic activity for MO degradation by hydrogen peroxide. The factors affecting the efficiency of MO decomposition including pH of the solution, H2O2 concentration, catalyst dosage, initial MO concentration, and reaction temperature were addressed. The present catalyst is stable after four recycles with slight catalytic activity loss which makes it a potential candidate for environmental restoration.

In the present study, the synthesis of metal organic framework (MOF) template-derived materials is reported. Cubic Fe2O3·TiO2 material was synthesized by using Prussian blue as the sacrificed template and aqueous soluble TiOSO4 as a TiO2 precursor. The obtained material was characterized by Fourier transform infrared (FT-IR) and Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), and nitrogen adsorption/desorption isotherms. The characterization confirmed the existence of cubic α-Fe2O3 core and anatase TiO2 shell in the composite. Furthermore, the appearance of TiO2 shell has significantly enhanced the Brunauer–Emmett–Teller (BET) surface area yet still retained small bandgap energy of around 2.0 eV. This material was employed to degrade chosen organic dyes, including cationic dyes and anionic dye, in a heterogeneous photo-Fenton like system. The experimental results showed that this material exhibited higher adsorption and degradation capacity toward cationic dyes than anionic dye. The fitting of experimental data into two kinetic models revealed that the removal of the dyes can be better described by Langmuir-Hinshelwood model. The recyclability of the catalyst was also examined.

Peat (Mekong River Delta, Vietnam) was naturally dried, and then mixed with coal slag in the ratio of 70:30 by weight to use as adsorbent to treat wastewater from Pangasius catfish ponds in batches. The adsorbent was used in a specific designed system to treat Pangasius pond wastewater in a continuous flow model at a speed of 0.3 m 3 .h −1 . The treatment system has operated for 9 consecutive hours in each experiment batch. The results show that the system can treat a large amount of wastewater (64.8 m 3 ) with the efficiency (%) of BOD5 of 95.78%, COD of 95.3%, total phosphorous of 73% and total nitrogen of 89.79%. After treatment, the quality of wastewater has met the standards to be discharged into the environment.

Ferromagnetic nanoparticles (FeNPs) have been successfully prepared by using solvothermal reduction method with polyethylene glycol as a solvent. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, nitrogen adsorption/desorption isotherms, and vibrating sample magnetometer. The magnetic properties and morphology of iron oxides was found to depend on the solvothermal temperatures. An increase in heating temperature from 120 to 240 °C did not only enhance the saturation magnetization from 21 to 81 emu g−1 but also produced larger, highly crystalline cubic particles of FeNPs. The development of FeNPs-modified glassy carbon electrode (GCE) using Nafion as a binder for sildenafil (SIL) detection was studied. Cyclic voltammetry and differential pulse voltammetry methods were employed for the electrochemical analysis of SIL using the modified electrode. The proposed sensor exhibited excellent electrocatalytic activity towards SIL oxidation with an enhancement in oxidation peak current. Under the optimum conditions, the current response for the determination of SIL was linear in two concentration ranges of 1.33–9.20 and 9.20–80.76 ppm and the limit of detection was 1.01 ppm. This sensor was then used for the determination of SIL in real samples with satisfactory results.

In the present paper, the composite of zeolite imidazolate framework-11 (ZIF-11) and activated carbon derived from rice husks (RHAC) was synthesized. The obtained materials were characterized by XRD, SEM, EDX-mapping, and nitrogen adsorption/desorption isotherms. The final composite ZIF-11/RHAC exhibits an even dispersion of ZIF-11 particles on activated carbon matrix. Herein, an electrochemical sensor based on a ZIF-11/RHAC was developed for a rapid determination of triclosan (TCS). It was found that the oxidation of TCS is irreversible and involves the transfer of one electron. The linear range for TCS detection in the optimized experimental conditions was found to be 0.1-8 μM with the limit of detection of 0.076 μM. Finally, the proposed method was successfully employed to detect TCS in different personal care product samples with high accuracy, which was confirmed by a good agreement between these results and those obtained using high-performance liquid chromatography (HPLC).

A TiO2/graphene quantum dots composite (TiO2/GQDs) obtained by in situ synthesis of GQDs, derived from coffee grounds, and peroxo titanium complexes was used as electrode modifier in the simultaneous electrochemical determination of uric acid and hypoxanthine. The TiO2/GQDs material was characterized by photoluminescence, X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray mapping. The TiO2/GQDs-GCE exhibits better electrochemical activity for uric acid and hypoxanthine than GQDs/GCE or TiO2/GCE in differential pulse voltammetry (DPV) measurements. Under optimized conditions, the calibration plots were linear in the range from 1.00 to 15.26 μM for both uric acid and hypoxanthine. The limits of detection of this method were 0.58 and 0.68 μM for uric acid and hypoxanthine, respectively. The proposed DPV method was employed to determine uric acid and hypoxanthine in urine samples with acceptable recovery rates.A TiO2/graphene quantum dots composite (TiO2/GQDs) obtained by in situ synthesis of GQDs, derived from coffee grounds, and peroxo titanium complexes was used as electrode modifier in the simultaneous electrochemical determination of uric acid and hypoxanthine. The TiO2/GQDs material was characterized by photoluminescence, X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray mapping. The TiO2/GQDs-GCE exhibits better electrochemical activity for uric acid and hypoxanthine than GQDs/GCE or TiO2/GCE in differential pulse voltammetry (DPV) measurements. Under optimized conditions, the calibration plots were linear in the range from 1.00 to 15.26 μM for both uric acid and hypoxanthine. The limits of detection of this method were 0.58 and 0.68 μM for uric acid and hypoxanthine, respectively. The proposed DPV method was employed to determine uric acid and hypoxanthine in urine samples with acceptable recovery rates.

In the present article, the adsorbent prepared from laterite with lanthanum and cerium oxides (La2O3-CeO2/laterite (LCL)) was efficiently employed for the removal of arsenite and fluoride from an aqueous environment. The obtained materials were characterized by XRD, SEM, and nitrogen adsorption/desorption. The synthesized LCL exhibited a high adsorption capacity towards arsenite (As(III)) and fluoride. The adsorption of both analytes on LCL, which was well-fitted to a pseudo-second-order equation, was found to be kinetically fast in the first 20 minutes and reached equilibrium at around 180 minutes. Weber’s intraparticle diffusion model in multilinearity using the piecewise linear regression combined with Akaike’s criteria was addressed. The adsorption capacities of LCL calculated from Langmuir’s isotherm model were found to be 67.08 mg·g-1 for arsenite and 58.02 mg·g-1 for fluoride. Thermodynamic parameters presented an endothermic nature of arsenite adsorption but an exothermic nature for fluoride and a negative Gibbs free energy for the spontaneous process of arsenite or fluoride adsorption at the studied temperature range. The excellent adsorption performance and stability make the composite of laterite and La-Ce binary oxides an alternative efficient and cheap adsorbent for the removal of arsenite and fluoride in an aqueous solution.