Bentonite-supported nano zero-valent iron composite as a green catalyst for bisphenol A degradation: Preparation, performance, and mechanism of action.

Bisphenol A (BPA) is a toxic environmental pollutant commonly found in wastewater. Using non-toxic materials and eco-friendly technology to remove this pollutant from wastewater presents multiple advantages. Treatment of wastewater with clay minerals has received growing interest because of the environment friendliness of these materials. Bentonite is a 2:1 layered phyllosilicate clay mineral that can support nano-metal catalysts. It can prevent the agglomeration of nano-metal catalysts and improve their activity. In this article, a green catalytic nano zero-valent iron/bentonite composite material (NZVI@bentonite) was synthesized via liquid-phase reduction. The average size of NZVI was approximately 40-50 nm. Good dispersion and low aggregation were observed when NZVI was loaded on the surface or embedded into the nanosheets of bentonite. Degradation of BPA, a harmful contaminant widely found in wastewater at relatively high levels, by NZVI@bentonite was then investigated and compared with that by pristine NZVI through batch Fenton-like reaction experiments. Compared with pristine NZVI and bentonite alone, the NZVI@bentonite showed a higher BPA degradation ratio and offered highly effective BPA degradation up to 450 mg/g in wastewater under optimum operating conditions. Adsorption coupled with the Fenton-like reaction was responsible for BPA degradation by NZVI@bentonite. This work extends the application of NZVI@bentonite as an effective green catalyst for BPA degradation in aqueous environments.

Pepsin as a marker for pulmonary aspiration.

BACKGROUND: Although assessment for aspiration of small volumes of gastric contents in tube-fed patients receiving mechanical ventilation is important, available methods for this purpose are not wholly satisfactory. A potential method is immunoassay of tracheal secretions for the gastric enzyme pepsin. OBJECTIVES: To determine the frequency with which pepsin in suctioned tracheal secretions from acutely ill, tube-fed patients receiving mechanical ventilation could be detected via an immunoassay. METHODS: A convenience sample of 136 specimens of suctioned tracheal secretions was collected from 30 acutely ill, tube-fed adults receiving mechanical ventilation. Multiple samples were obtained from 26 of the 30 patients (range, 2-11 per subject). An immunoassay with rooster polyclonal antibodies to purified human pepsin was used to detect pepsin in the secretions. RESULTS: Fourteen specimens tested positive for pepsin. Secretions from 5 patients accounted for the 14 pepsin-positive results. A significant relationship was found between the position of the head of the bed and the presence of pepsin in tracheal secretions (P<.001). Of the 14 pepsin-positive specimens, 13 (92.9%) were obtained from subjects in a flat position. CONCLUSIONS: A pepsin immunoassay can be used to detect pepsin in human tracheal secretions. If pepsin in tracheal secretions is considered an indicator of aspiration of gastric contents, aspiration occurred in 5 of the 30 subjects. A flat position is strongly associated with the presence of pepsin in tracheal secretions.