Preparation of Zn/Zr-MOFs by microwave-assisted ball milling and adsorption of lomefloxacin hydrochloride and levofloxacin hydrochloride in wastewater.

The Zn/Zr-MOFs were synthesized via microwave-assisted ball milling and subsequently characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The thermal stability of the Zn/Zr-MOFs was evaluated through thermogravimetry (TGA). The results demonstrated the exceptional adsorption properties of the Zn/Zr-MOFs towards Lomefloxacin hydrochloride and Levofloxacin hydrochloride. At a concentration of 30 ppm for Lomefloxacin hydrochloride, the addition of 30 mg of Zn/Zr-MOFs material resulted in an adsorption capacity of 179.2 mg•g-1. Similarly, at a concentration of 40 ppm for Levofloxacin hydrochloride, the addition of 30 mg Zn/Zr-MOFs material led to an adsorption capacity of 187.1 mg•g-1. Kinetic analysis revealed that the experimental data aligned well with a pseudo-second order kinetic model. Overall, these findings highlight the significant potential application of Zn/Zr-MOF materials in wastewater treatment.

Preparation of Fe/Ni-MOFs for the Adsorption of Ciprofloxacin from Wastewater.

This work studies the use of Fe/Ni-MOFs for the removal of ciprofloxacin (CIP) in wastewater. Fe/Ni-MOFs are prepared by the solvothermal method and characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and a thermal gravimetric analyzer (TG). Under the conditions of the concentration of 50 ppm, a mass of 30 mg, and a temperature of 30 °C, the maximum adsorption capacity of ciprofloxacin removal within 5 h was 232.1 mg/g. The maximum removal rate was 94.8% when 40 mg of the Fe/Ni-MOFs was added to the solution of 10 ppm ciprofloxacin. According to the pseudo-second-order (PSO) kinetic model, the R2 values were all greater than 0.99, which proved that the adsorption theory of ciprofloxacin by Fe/Ni-MOFs was consistent with the practice. The adsorption results were mainly affected by solution pH and static electricity, as well as other factors. The Freundlich isotherm model characterized the adsorption of ciprofloxacin by Fe/Ni-MOFs as multilayer adsorption. The above results indicated that Fe/Ni-MOFs were effective in the practical application of ciprofloxacin removal.

Highly stable and Active Cu1 /CeO2 Single-Atom Catalyst for CO Oxidation: A DFT Study.

We carried out density functional theory simulations to examine the stability and CO oxidation activity of single Cu atoms supported on CeO2 (111). Both the strong binding energy and high activation energy for Cu single atom diffusion indicate a high stability of the Cu1 /CeO2 single-atom catalyst. Electronic structure analysis verifies the formation of Cu+ cation due to electron transfer. The frequency analysis further corroborates that the experimentally observed IR bands around 2114-2130 cm-1 of CO adsorption at the boundary of Cu/CeO2 correspond to Cu+ -carbonyl species. Cu1 /CeO2 single-atom catalyst displays a promising catalytic activity for CO oxidation via Mars van Krevelen mechanism.

Enhanced Fenton removal of phenol catalyzed by a modified red mud derived from the reduction of oxalic acid and L-ascorbic acid.

Red mud, a bauxite residue generated during alumina production through the Bayer process, contains oxides of Fe, Ti, Al, Mn, and rare earths, and has a latent performance for catalytic removal of phenol. We proposed a novel and facile approach for red mud modification by the reduction of oxalic acid and L-ascorbic acid in the acidic solution. By surveying characteristics of modified red mud and influencing factors of phenol removal, the optimum experiment conditions and the possible mechanism were explored, respectively. The results demonstrated that RO2V2 (treated red mud using 2 g of oxalic acid dehydrate and 2 g of L-ascorbic acid) and RO3V3 (treated red mud using 3 g of oxalic acid dehydrate and 3 g of L-ascorbic acid) showed the most efficient catalytic capacity for the phenol removal and removal efficiency of over 99.1% for the 200 mg/L of phenol solution within 5 min among investigated catalysts with the pH decreasing from 6.7 to 3. The excellent catalytic performance of modified red mud profited from the production of Fe3O4, Fe2O3, Mn2O3, Fe2SiO4, and FeTiO3 in the catalysts. It was motivating for removal of phenol to increase the dosage of catalyst and H2O2. The rate constants of the pseudo-first-order kinetics model of RO2V2 and RO3V3 were 1.0 and 1.073, respectively. The results of continuous experiments provided a positive reference for a future pilot scale test.

Removal of tetracycline hydrochloride from wastewater by Zr/Fe-MOFs/GO composites.

Zirconium-iron metal-organic frameworks (Zr/Fe-MOFs) and Zr/Fe-MOF/graphene oxide (GO) composites were prepared via solvothermal synthesis using ferrous sulfate heptahydrate, zirconium acetate, and 1,3,5-benzenetricarboxylic acid. The MOFs and composites were measured using scanning electron microscopy (SEM), infrared spectrometry (IR), and thermogravimetric analysis (TGA). In this study, we explored the ability of Zr/Fe-MOFs and Zr/Fe-MOF/GO composites to adsorb tetracycline hydrochloride from an aqueous solution. Additionally, we optimized the adsorption performance by varying the ratio of MOFs and MOF composites to tetracycline hydrochloride solution, the concentration of tetracycline hydrochloride solution, and the pH of the solution. The results were investigated and fit to both pseudo-first-order and pseudo-second-order kinetic models. The results of the Freundlich and Langmuir isotherm models indicate that Zr/Fe-MOFs and Zr/Fe-MOF/GO composites have heterogeneous adsorption surfaces and that tetracycline hydrochloride is adsorbed over Zr/Fe-MOFs and Zr/Fe-MOF/GO by multilayer adsorption. Overall, our findings indicate that Zr/Fe-MOFs and Zr/Fe-MOF/GO composites can effectively treat wastewater, providing an inexpensive alternative to other methods.

Removal of organic contaminants from wastewater with GO/MOFs composites.

Graphene oxide/metal-organic frameworks (GO/MOFs) have been prepared via solvothermal synthesis with ferrous sulfate heptahydrate, zirconium acetate and terephthalic acid for the purpose of removing organic pollutants from wastewater. The composites were analyzed using scanning electron microscopy, infrared spectrometry, and XRD. Tetracycline hydrochloride and orange II were implemented as model pollutants to evaluate the efficacy of the GO/MOFs in water purification, in which 50 mg of Zr/Fe-MOFs/GO was mixed with 100 mL of 10 mg/L, 20 mg/L, 30 mg/L, or 50 mg/L tetracycline hydrochloride solution and 25 mg/L, 35 mg/L, 45 mg/L, or 60 mg/L orange II solution, respectively. The removal efficacy after 4 hours was determined to be 96.1%, 75.8%, 55.4%, and 30.1%, and 98.8%, 91.9%, 71.1%, and 66.2%, respectively. The kinetics of pollutant removal was investigated for both tetracycline hydrochloride and orange II and excellent correlation coefficients of greater than 0.99 were obtained. The high efficacy of these MOFs in pollutant removal, coupled with their inexpensive preparation indicates the feasibility of their implementation in strategies for treating waste liquid. As such, it is anticipated that Zr/Fe-MOFs/GO composites will be widely applied in wastewater purification.

Fluorescence Invigoration in Carbon-Incorporated Zinc Oxide Nanowires from Passage of Field Emission Electrons.

We demonstrate that carbon incorporated Zinc Oxide (C-ZnO) nanowires (NWs) exhibit remarkable improvement in the extent and quality of fluorescence emission after they are utilized as an electron source in a field emission experiment. After the passage of field emission electrons, the intensity of the fluorescence emitted from these NWs in the visible light range exhibits a 2.5 to 8 fold enhancement. The intrinsic exciton peak of the ZnO also becomes heightened, along with the crystalline quality of the NWs showing marked improvement. This invigoration of fluorescence across the entire fluorescence spectrum is attributed to concurrent removal of oxygen and carbon atoms in C-ZnO NWs due to electro-migration of atoms and joule heating during the field emission process. Applications based on ZnO NWs emission from excitonic emissions or visible wavelength emissions or both can benefit from this straightforward method of defect engineering.

Comparison Study on the Adsorption Capacity of Rhodamine B, Congo Red, and Orange II on Fe-MOFs.

Using a microwave-assisted ball-milling approach, Fe-based metal-organic frameworks (Fe-MOFs) were prepared from FeSO4·7H2O and trimesic acid. Scanning electron microscopy, Fourier-transform infrared spectrometry, X-ray, and thermogravimetric analysis were utilized to characterize the thermal stability and structure of the prepared Fe-MOFs. These Fe-MOFs were used to remove organic dyes from aqueous solutions. Specifically, they removed 96.97% of 23.3592 mg/L of Congo red in a 200 mL solution within 300 min of treatment with natural light at 15 °C. Likewise, 88.21 and 70.90% of 22.7527 mg/L of Orange II and 17.8326 mg/L of Rhodamine B, respectively, were removed from 200 mL solutions within 300 min of treatment at 15 °C. At 35 °C, 99.57, 95.98, and 99.38% of 23.3855 mg/L of Congo Red, 22.7365 mg/L of Orange II, and 17.9973 mg/L of Rhodamine B, respectively, were removed from 200 mL solutions within 300 min of treatment. The adsorption kinetics were investigated and the pseudo-first-order kinetic model was found to be superior to the pseudo-second-order kinetic model. Overall, using metal-organic frameworks to treat dye wastewater was found to be inexpensive, feasible, and efficient. Therefore, this material has future prospects in research and applications in the purification of wastewater.

Removal of Congo red dye from aqueous solution with nickel-based metal-organic framework/graphene oxide composites prepared by ultrasonic wave-assisted ball milling.

Metal-organic frameworks (MOFs) were successfully synthesized by ultrasonic wave-assisted ball milling. In the absence of organic solvent, the coupling effect of ultrasonic wave and mechanical force played an significant role in the synthesis of MOFs. Adsorption of Congo red (CR) was studied in view of adsorption kinetic, isotherm and thermodynamics. The adsorbent was carried out using X-ray diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption-desorption isotherms, Raman spectroscopy and scanning electron microscope (SEM) methods. It was found that pseudo-second-order kinetic model and Freundlich adsorption isotherm matched well for the adsorption of CR onto nickel-based metal-organic framework/graphene oxide composites (Ni-MOF/GO). The results of the adsorption thermodynamics indicated that the adsorption process was a spontaneous and endothermic process. The adsorption capacity of graphene oxide/metal-organic frameworks (GO/MOFs) for CR reached 2489mg/g, much higher than previous reports. It was demonstrated that an increase in the number of active metal sites can dramatically improve the adsorption capacity of dye. A suitable dry temperature is beneficial for the improvement of adsorption capacity for dye. In this paper, the adsorption results indicated that ultrasonic wave-assisted ball milling has a good prospect for synthesis of MOFs with excellent adsorption performance.

Preparation of Fe-MOFs by microwave-assisted ball milling for reducing Cr(vi) in wastewater.

Fe-Based metal-organic frameworks (Fe-MOFs) were prepared with trimesic acid and FeSO4·7H2O via a microwave-assisted ball milling approach. The structure and thermal stability of the as-prepared Fe-MOFs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). When used to degrade 20 mg L-1 hexavalent chromium in aqueous solution, the Fe-MOFs were found to completely reduce a 100 mL solution within 120 min under natural light and a 400 mL solution within 90 min under Xe lamp irradiation. Under natural sunlight, 98% of the Cr(vi) was removed from a 40 mL solution after 40 min.

Biodiesel Production by Catalytic Esterification of Oleic Acid over Copper (II)-Alginate Complexes.

A systematic study on copper (II)-alginate beads as catalysts for the synthesis of biodiesel via esterification of oleic acid and methanol is here reported for the first time. The chemical structure and morphologies of these catalysts were fully characterized by XRD, FT-IR, and SEM. The copper (II)-alginate beads showed a tubular structure with entangled reticulation. In the presence of copper (II)-alginate catalyst, the biodiesel conversion of 71.8% was achieved from oleic acid with methanol under the most mild conditions (1/10 oleic acid to methanol molar ratio, 250 mg catalyst, 70°C for 3 h), optimized by single-factor experiments. The catalyst could be easily separated from the reaction mixture and stabilized for a certain time. This material can also catalyze other esterification of fatty acids with different carbon chain lengths, as well as the pretreatment of non-edible oils with high acid value. Our findings showed that the copper (II)-alginate is a suitable catalyst for esterification and would provide more choices for industrial application in the future.