Hongying Quan

Adsorption Behaviors of Organic Micropollutants on Zirconium Metal–Organic Framework UiO-66: Analysis of Surface Interactions

Herein, we studied the adsorption behaviors of organic micropollutants, such as anticonvulsant carbamazepine (CBZ) and antibiotic tetracycline hydrochloride (TC), on zirconium metal-organic framework UiO-66 in water. The maximum adsorption capacities of CBZ and TC on the UiO-66 were 37.2 and 23.1 mg·g-1 at 25 °C, respectively. The adsorption isotherms and kinetics of CBZ and TC were well described by using the Langmuir model and pseudo-second-order model, respectively, and the adsorptions on UiO-66 are endothermic reactions. The adsorption capacities of CBZ and TC on UiO-66 were decreased with the increase of solution pH. The presence of humic acid could improve the adsorption of CBZ and TC on UiO-66, but K+ ion inhibited their adsorption obviously. In addition, Ca2+ and Al3+ ions also suppressed the adsorption of TC on UiO-66. The competitive adsorption suggested that the adsorption sites for CBZ on UiO-66 were different from those for TC. The surface interactions between UiO-66 and the two micropollutants were demonstrated by powder X-ray diffraction, Fourier transform infrared (FT-IR) spectra, scanning electron microscopy, nitrogen adsorption/desorption isotherms, and X-ray photoelectron (XPS) spectra. The characterizations showed that the adsorption of CBZ on UiO-66 is mainly a physisorption, and the hydrophobic effect played a crucial role during the adsorption of CBZ; meanwhile weak π-π electron donor-acceptor interaction and electrostatic attraction also existed. However, the adsorption of TC on UiO-66 is mainly a chemisorption; in addition to the strong electrostatic attraction and π-π electron donor-acceptor interaction forces, the nitrogenous groups of TC played an important role, which can replace the carboxylic groups coordinated with Zr-O clusters. The obtained results will aid us to comprehend the surface interaction between organic micropollutants and UiO-66 and expand the application of UiO-66 as sorbent for removal of pollutants from water.

Enhanced photocatalytic properties of ZnFe2O4-doped ZnIn2S4 heterostructure under visible light irradiation

ZnFe2O4-doped ZnIn2S4 heterostructures were fabricated with a series of different proportions of ZnFe2O4 using a two-step solvothermal method. The as-synthesized ZnFe2O4–ZnIn2S4 heterostructure exhibited enhanced photocatalytic performance in the degradation of organic pollutants compared to bare ZnIn2S4 and ZnFe2O4 under visible light irradiation, and the 2.5 wt% ZnFe2O4–ZnIn2S4 showed the highest activity. The enhanced mechanism of photocatalytic activity can be mainly attributed to the stable heterojunction interface between ZnFe2O4 and ZnIn2S4, which can efficiently improve the separation of photogenerated carriers. Meanwhile, the increased surface-active sites and extended light absorption of ZnIn2S4 after the decoration of ZnFe2O4 nanoparticles may also play a certain role in enhancing photocatalytic activity.

Heterogeneous Fenton-like catalysis of Fe-MOF derived magnetic carbon nanocomposites for degradation of 4-nitrophenol

Magnetic carbon nanocomposites (Fe–Cx) as heterogeneous Fenton-like catalysts were synthesized by the pyrolysis of iron based metal-organic frameworks (Fe-MOF), and the degradation removal of 4-nitrophenol (4-NP) in aqueous solution was used to evaluate the catalytic activity of Fe–Cx. The results showed that 4-NP could be effectively degraded by Fe–Cx in the presence of hydrogen peroxide. Pyrolysis temperature significantly affected the component, structures and performances of the catalysts, and the as-prepared Fe–C500 exhibited the best catalytic performance. Furthermore, the effects of several reaction conditions, such as catalyst loading, H2O2 dosage, reaction temperature, and initial pH, on the catalytic degradation of 4-NP were extensively analyzed for the practical applications of Fe–C500. At an initial circumneutral pH of 6.21, 89.0% of 0.36 mM 250 mL of 4-NP solution could be degradated after 75 min by the heterogeneous Fenton-like oxidation on the 0.08 g L−1 of Fe–C500 in the presence of 7.8 mM H2O2. The results of activation energy and the reaction kinetics showed Fe–C500 possessed a high catalytic activity in the heterogeneous Fenton reaction of 4-NP. Moreover, the prepared Fe–C500 could be reused by an external magnet, and still retained good catalytic activity with 52.4% degradation of 4-NP at the fourth cycle.