Sustainable and green persulfate-based chemiluminescent method for on-site estimation of chemical oxygen demand in waters

The standard method for estimating the chemical oxygen demand (COD) of water bodies uses dichromate as the main oxidant, a chemical agent whose use has been restricted in the European Union since 2017. This method is hazardous, time-consuming, and burdensome to adapt to on-site measurements. As an alternative and following the current trends of sustainable and green chemistry, a method using the less toxic reagent sodium persulfate as the oxidizing agent has been developed. In this method an excess of persulfate, activated through heating in an alkaline solution, oxidizes the chemically degradable organic fraction through a 2-step radical mechanism. The remaining persulfate is evaluated by chemiluminescence (CL) using luminol and a portable charge-coupled device (CCD) camera. The method provided quantitative recoveries and a sample throughput of >60 samples h. It was validated in river water samples by comparison of COD estimations with the standard dichromate method (R = 0.973, p < 0.05) and with a UV–Vis permanganate-based method (R = 0.9998, p < 0.05), the latter being also used for drinking waters. The proposed method is a sustainable and green alternative to the previous used methods. Overall, the method using activated persulfate is suitable for use as COD quantitation/screening tool in surface waters. Considering that its main components are portable, it can be ultimately adapted for in situ analysis at the point of need

New silica based adsorbent material from rice straw and its in-flow application to nitrate reduction in waters: Process sustainability and scale-up possibilities

[EN] This paper shows a particular example to move to a sustainable circular economical process from valorization of rice straw ashes by developing a green synthesis for obtaining a useful sub-product. This strategy can palliate negative effects of the agriculture waste practices on the environment and also the obtained silica reduced nitrate content in waters. It is demonstrated that the silica synthesis developed at lab was scalable more than a hundred times with good results. Adsorption studies of nitrate in standards and real well waters at lab scale and scaling-up provided similar results. Adsorption values near to 15 mg/g for nitrate standards and 8.5 mg/g for well water were obtained until achieving the initial nitrate concentration. Experimental breakthrough curves fitted to Thomas model, which gave similar results for adsorption capacities. The adsorption capacity was checked with that obtained by a commercial resin, providing improved results. The method at large scale was compared with industrial traditional methods and green adsorbents.The authors are grateful to EU (EASME LIFE and CIP ECO-Innovation) LIBERNITRATE. LIFE 16 ENV/ES/000419; EU FEDER and the Gobierno de Espana MCIU-AEI (CTQ2017-90082-P) and the Generalitat Valenciana (PROMETEO 2020/078) and EU FEDER-Generalitat Valenciana (ID-FEDER/2018/049) for the financial support received. H. R. Robles-Jimarez expresses his grateful to EU-LIBERNITRATE. L. Sanjuan-Navarro expresses his gratitude for the FPU-grant (MCIU-AEI) .Robles-Jimarez, H.; Sanjuan-Navarro, L.; Jornet-Martínez, N.; Primaz, C.; Teruel-Juanes, R.; Molins-Legua, C.; Ribes-Greus, A.... (2022). New silica based adsorbent material from rice straw and its in-flow application to nitrate reduction in waters: Process sustainability and scale-up possibilities. Science of The Total Environment. 805:1-12. https://doi.org/10.1016/j.scitotenv.2021.15031711280

More about sampling and estimation of mercaptans in air samples

[EN] Several strategies have been developed for sampling and determination of volatile thiols. The selectivity and sensitivity of the proposed methodologies are achieved by using a specific derivatizing reagent. The different procedures assayed are based on air sampling followed by derivatization of the analytes with OPA and isoleucine in alkaline solution. The derivatization products are separated and determined by liquid chromatography and fluorescence detection. To start, the derivatization conditions and stability of the derivates have been studied in order to establish the storage conditions. In general, the strategies studied consisted on trapping and detivatization the thiol compound on different support; a solution (Impinger) or sorbent (C-18 cartridges or glass fiber filter). The analytical properties of the different strategies have been obtained and compared. Procedures are recommended upon specific situations. (C) 2012 Elsevier B.V. All rights reserved.The authors are grateful to the Spanish Ministerio de Economia y Competitividad (project CTQ2011-26760) and to the Generalidad Valenciana (Prometeo Program 2012/45). Y.M.M expresses her grateful for a JdC research contract.Moliner Martínez, Y.; Herráez Hernández, R.; Molins Legua, C.; Verdú Andrés, J.; Avella-Oliver, M.; Campins Falcó, P. (2013). More about sampling and estimation of mercaptans in air samples. Talanta. 106:127-132. doi:10.1016/j.talanta.2012.12.001S12713210