Visible-Light Driven H2O-to-H2O2 Reaction by Nitrogen-Enriched Resins for Photocatalytic Oxidation of an Organic Pollutant in Wastewater.

A photocatalytic H2O-to-H2O2 reaction for sustainable organic wastewater treatment is environmentally attractive. Phenolic resins, inexpensive metal-free photocatalysts, are capable of harvesting visible light. Herein, novel nitrogen-enriched resin photocatalysts with a desired band-gap energy (1.83-1.98 eV) for harvesting visible light were prepared by copolymerization of resorcinol and melem for simultaneous photocatalytic H2O-to-H2O2 and oxidation of methylene blue. Under visible light irradiation for 5 h, very high yields of H2O2 (870-975 µM of H2O2/g/h) by RFM resin photocatalysts could be achieved. The photocatalytic H2O2 for reactive oxygen species (•OH) and photogenerated h+ could account for high conversion (40% conversion under visible light irradiation within 3 h) in oxidation of methylene blue. Such unique low-cost metal-free resins demonstrate the visible light photocatalytic H2O-to-H2O2 reaction which can synergize with the oxidation of organic pollutants in wastewater.

Simultaneous determination of nitrate and nitrite in vegetables by poly(vinylimidazole-co-ethylene dimethacrylate) monolithic capillary liquid chromatography with UV detection.

Simultaneous determination of nitrate (NO3‾) and nitrite (NO2‾) in vegetables was performed on a poly(1-vinylimidazole-co-ethylene dimethacrylate) (VIM-EDMA) monolithic column by capillary liquid chromatography (LC) with UV detection. Good linearity (0.5-100 µg mL-1 i.e. 12.5 -2500 µg g-1 in vegetables) was obtained with coefficient of determination > 0.996. Limits of detection (signal-to-noise ratio: S/N= 3) were estimated at 0.06 and 0.05 µg mL-1, which corresponded to 1.50 and 1.25 µg g-1 for NO2‾ and NO3‾, respectively, in vegetables. The limits of quantification (S/N= 10) were estimated at 0.17 and 0.16 µg mL-1 (4.25 and 4.00 µg g-1 in vegetables) for NO2‾ and NO3‾, respectively. Although the detection limits were relatively higher than other LC-UV techniques, this proposed method offered satisfactory sensitivity for complying the Acceptable Daily Intake (ADI) levels set by EU to monitor the occurrence of NO2‾ and NO3‾in vegetables. The intra-day/inter-day precision (0.14-3.35%/0.06-6.93%) and accuracy (90.33-103.32%/96.00-101.26%) were also examined for method validation. No obvious carry-over and decline of separation efficiency were observed for more than 200 analyses of real samples. The occurrence of NO2‾ and NO3‾in various vegetable samples was investigated to demonstrate the potential of utilizing the developed polymeric monolith-based capillary LC-UV method for food safety application.