Removal of NO at low concentration from air in urban built environments by activated miscanthus biochar

This work presents an innovative and sustainable approach to remove NO emissions from urban ambient air in confined areas (underground parking areas or tunnels) using low-cost activated carbons obtained from Miscanthus biochar (MSP700) by physical activation (with CO2 or steam) at temperatures ranging from 800 to 900 °C. The NO removal capacity of the activated biochars was evaluated under different conditions (temperature, humidity and oxygen concentration) and compared against a commercial activated carbon. This last material showed a clear dependence on oxygen concentration and temperature, exhibiting a maximum capacity of 72.6% in air at 20 °C, whilst, its capacity notably decreased at higher temperatures, revealing that physical NO adsorption is the limiting step for the commercial sample that presents limited oxygen surface functionalities. In contrast, MSP700-activated biochars reached nearly complete NO removal (99.9%) at all tested temperatures in air ambient. Those MSP700-derived carbons only required low oxygen concentration (4 vol%) in the gas stream to achieve the full NO removal at 20 °C. Moreover, they also showed an excellent performance in the presence of H2O, reaching NO removal higher than 96%. This remarkable activity results from the abundance of basic oxygenated surface groups, which act as active sites for NO/O2 adsorption, along with the presence of a homogeneous microporosity of 6 Å, which enables intimate contact between NO and O2. These features promote the oxidation of NO to NO2, which is further retained over the carbon surface. Therefore, the activated biochars studied here could be considered promising materials for the efficient removal of NO at low concentrations from air at moderate temperatures, thus closely approaching real-life conditions in confined spaces.J. Fermoso gratefully acknowledges the financial support from the Comunidad de Madrid through the Talent Attraction Programme (2018-T1/AMB-10023)

Enhanced Recovery of Natural Antioxidants from Grape Waste Using Natural Eutectic Solvents-Based Microwave-Assisted Extraction

The evaluation of sustainable solvents as alternatives to more harmful conventional solvents combined with intensification techniques to recover phenolic compounds from agri-food waste is in the spotlight. The wine industry generates large amounts of waste as a consequence of grape processing operations, which can be revalued by solvent extraction of valuable antioxidants for food and fine chemical applications. Therefore, the present study focuses on the use of natural eutectic solvents (NAESs) with benign environmental, health, and safety profiles, for valorization of grape waste in the context of a circular economy. Herein, up to 15 NAESs consisting of combinations of three hydrogen bond acceptors (choline chloride, L-proline, and betaine) and four hydrogen bond donors (1,2-propanediol, glycerol, and 1,2- and 1,3-butanediol) were evaluated for antioxidant recovery. After an initial screening of the performance of NAESs by conventional extraction, the process was intensified by microwave-assisted extraction (MAE). The extracts were analyzed by UV/VIS spectrophotometric and HPLC methods. Promising results were obtained with the solvent betaine, 1,2-butanediol [1:4], using MAE at 100 °C for 3 min. Overall, the proposed NAESs-based MAE method was successfully applied to recover target compounds from grape waste, with great prospects for the antioxidants market and sustainable development for the winery sector

Enhanced Recovery of Natural Antioxidants from Grape Waste Using Natural Eutectic Solvents-Based Microwave-Assisted Extraction

The evaluation of sustainable solvents as alternatives to more harmful conventional solvents combined with intensification techniques to recover phenolic compounds from agri-food waste is in the spotlight. The wine industry generates large amounts of waste as a consequence of grape processing operations, which can be revalued by solvent extraction of valuable antioxidants for food and fine chemical applications. Therefore, the present study focuses on the use of natural eutectic solvents (NAESs) with benign environmental, health, and safety profiles, for valorization of grape waste in the context of a circular economy. Herein, up to 15 NAESs consisting of combinations of three hydrogen bond acceptors (choline chloride, L-proline, and betaine) and four hydrogen bond donors (1,2-propanediol, glycerol, and 1,2- and 1,3-butanediol) were evaluated for antioxidant recovery. After an initial screening of the performance of NAESs by conventional extraction, the process was intensified by microwave-assisted extraction (MAE). The extracts were analyzed by UV/VIS spectrophotometric and HPLC methods. Promising results were obtained with the solvent betaine, 1,2-butanediol [1:4], using MAE at 100 °C for 3 min. Overall, the proposed NAESs-based MAE method was successfully applied to recover target compounds from grape waste, with great prospects for the antioxidants market and sustainable development for the winery sector

Valorisation of Sargassum muticum through the extraction of phenolic compounds using eutectic solvents and intensification techniques

Seaweeds are naturally abundant and spread all over the globe. They have several biologically active secondary metabolites of great interest. In this work, Sargassum muticum was the algae employed as biomass and the aim was to extract phenolic compounds (PCs) using eutectic solvents (ESs). Several betaine-based, proline-based, and choline-based ESs were tested for the extraction of PCs. All extracts were evaluated according to the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (DPPH). Afterwards, the extracts were characterized using HPLC in terms of 9 target PCs (gallic acid, 3,4-dihydroxybenzoic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, salicylic acid, catechin and quercetin). Proline combined with propylene glycol (Pro[thin space (1/6-em)]:[thin space (1/6-em)]PPG) exhibited a higher yield according to HPLC results, followed by proline[thin space (1/6-em)]:[thin space (1/6-em)]1,2-butanediol (Pro[thin space (1/6-em)]:[thin space (1/6-em)]1,2-But) and choline[thin space (1/6-em)]:[thin space (1/6-em)]citric acid (ChCl[thin space (1/6-em)]:[thin space (1/6-em)]CA). Pro[thin space (1/6-em)]:[thin space (1/6-em)]PPG also presented high selectivity towards salicylic acid, while ChCl[thin space (1/6-em)]:[thin space (1/6-em)]CA towards gallic acid. Optimization studies of water content and temperature were performed for the three best ESs, the optimum conditions being 30% (v/v) water and 60 °C extraction temperature. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were two intensification methods evaluated to enhance the extraction process, proving their ability to reduce the extraction time when compared with the conventional solid–liquid extraction (SLE) process. In particular, Pro[thin space (1/6-em)]:[thin space (1/6-em)]PPG-based MAE provided a significantly higher extraction yield in comparison with conventional extraction and with the other extraction solvents. In summary, the combination of ESs with intensification techniques was shown to be a valuable valorization strategy of a marine macroalgae waste, in particular Sargassum muticum.info:eu-repo/semantics/publishedVersio