Effective photocatalytic degradation of sulfamethoxazole using tunable CaCu3Ti4O7 perovskite.

Sulfamethoxazole (SMX) is largely prescribed for bacterial infections but raises a major concern over generation of antibiotic-resistant bacteria in the environment. This study employed various perovskite-type photocatalysts, made by two-step synthesis procedures, to remove SMX. The as-synthesized CaCu3Ti4O7 (CCTO) perovskites were characterized by XRD, SEM-EDX, and DLS. Complete degradation (∼99%; kobs = 0.0279 min-1) of SMX was recorded under UV-light irradiation for 90 min in the presence of CCTO. SMX removal rate was investigated under various reaction conditions including pH, catalyst dose, electrolyte (NaCl and NaBr). The astonishing rate of SMX removal (kobs = 0.0614 min-1) was observed with the addition of 50 mM NaBr electrolytes in the reaction, which might imply that the appearance of halogen reactive species. CCTO-MS particles were aggregated in traces when the electrolytes concentration increases, resulting in reduced rate of SMX. The SMX concentration abatement and the formation of possible intermediates during photocatalytic reaction were analyzed. The upshot of this study reveals that the inexpensive and environmentally benign CCTO perovskite photocatalyst could be applied for the treatments of emerging contaminants in the future.

New insights of metal free 2D graphitic carbon nitride for photocatalytic degradation of bisphenol A.

Polymeric oxygen rich exfoliated graphitic carbon nitride (exfoliated GCN, EGCN) was synthesized by the acid treatment of bulk GCN. The photocatalyst was characterized using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and point of zero charge. EGCN shows high valance band hole transfer under short-time visible light (λ > 420 nm) exposure for photocatalytic mineralization of bisphenol A (BPA). Enhanced BPA removal was achieved by EGCN (99 %) due to formation of OH● radicals (H2O/hVB+ →OH●/H+). Major factors affecting BPA degradation including catalyst dose, wide pH range, and pollutant concentration were optimized. Repeated cycles of BPA degradation were performed with negligible rate decreased from 0.045 to 0.029 min-1. The degradation profile and plausible reaction mechanism of BPA was established and well justified by the byproducts identified by mass analysis HR-ESI-MS. Therefore, the as-synthesized metal free EGCN, active under visible light, offers a new platform for complete mineralization of byproducts of halogenated organic contaminants.

Mechanism of Nanoformulated Graphene Oxide-Mediated Human Neutrophil Activation.

Understanding the molecular mechanisms of graphene oxide (GO)-based biomaterials is important for logical biomedical applications. Previous studies have revealed biointeractions between GO and immune effector cells, but the effects on neutrophils, crucial cells in the immune system, have not been thoroughly discussed. In this study, GO nanoformulations were synthesized with different functional groups, including GO, GO-carboxylated (GO-COOH), and PEGylated GO (GO-PEG), with different surface features, which were elucidated using imaging methods and surface-sensitive quantitative spectroscopic techniques, including atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoemission spectroscopy (XPS). The GO-based nanoformulations elicited reactive oxygen species (ROS) generation and neutrophil extracellular trap (NET) formation in human neutrophils. Nanoformulated GO stimulates NET development via the formation of ROS. An endocytosis study revealed that nanoformulated GO facilitated internalization by neutrophils via macropinocytosis and actin-dependent phagocytosis. Importantly, calcium mobilization and phosphorylation proteins such as mitogen-activated protein kinases (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38) and AKT were involved in the activation of neutrophils. These findings offer the first verification that nanoformulated GO exhibits direct effects on human neutrophils.

Bimetallic Fe/Al system: An all-in-one solid-phase Fenton reagent for generation of hydroxyl radicals under oxic conditions.

In the classic Fenton reaction, both H2O2 and ferrous ion (Fe(II)) are required under a narrow low pH range to produce hydroxyl radicals (OH). The modified Fenton processes including heterogeneous Fenton-like reaction, photo-Fenton reaction and electro-Fenton reaction developed to overcome the drawbacks of the homogeneous Fenton reaction have recently received increasing attention. However, all the modifications of the classic Fenton reaction cannot be assembled into one system and require external supply of reagents or energy. We present here, bimetallic Fe/Al, a novel solid-phase Fenton reagent capable of in situ generation of H2O2 and Fe(II) to form OH under near neutral pH conditions without an external energy supply. Aluminum acts as an electron donor to maintain the electron supply and preserve the outer layer of iron at the zero-valence state with enhanced surface areas. The production of OH by bimetallic Fe/Al was quantified and further detected by an electron paramagnetic resonance (EPR) analysis under oxic conditions. Radical scavenging tests were performed by adding isopropanol or 1,4­benzoquinone in the system to investigate the nature of the oxidants produced during the oxidative process. Bimetallic Fe/Al system for the Fenton reaction in water involves both surface-mediated and aqueous-phase reactions. A pilot scale test using a continuous-flow column packed with Fe/Al (9.8 kg) demonstrated the capability of bimetallic Fe/Al for COD removal of acidic dye solutions. The novelty of bimetallic Fe/Al is that it is an all-in-one solid-phase Fenton reagent that can be readily applied to a wide variety of environmental applications.