What happens to inorganic nitrogen species during conductive diamond electrochemical oxidation of real wastewater?

Abstract

This work describes the oxidation of caffeine, metoprolol, SMX and progesterone in real wastewater in terms of inorganic nitrogen speciation and help to clarify the mechanisms that affect inorganic nitrogen species as final products. In synthetic solutions containing ammonium or nitrates ions, it has been confirmed that reduction of nitrates is a very favored process while oxidation of ammonium is negligible. Role of chloride is demonstrated to be important in the formation of chloramines, as well. These results allow to clarify the production of nitrates as main product of the oxidation of organic chemicals and the occurrence of ammonium and chloramines in the reaction media, as well as the depletion of nitrogen by gaseous nitrogen production. Results are of a great relevance to interpret the mechanisms proposed in the literature for the treatment of organic wastes by conductive diamond electrochemical oxidation.

Thiamethoxam removal by Fenton and biological oxidation

“…Similarly, the stoichiometric H 2 O 2 dose led to 35% TN recovery in the form of NO 3 − and NO 2 − . The N mass balance also was incomplete, probably because of the release of N‐containing byproducts such as chloramines or gaseous nitrogen oxides (N x O y ) …”

“…Similarly, the stoichiometric H 2 O 2 dose led to 35% TN recovery in the form of NO 3 − and NO 2 − . The N mass balance also was incomplete, wileyonlinelibrary.com/jctb probably because of the release of N-containing byproducts such as chloramines 48 or gaseous nitrogen oxides (N x O y ). 47,49 Ecotoxicity and biodegradability Fenton-like oxidation was used here to increase the biodegradability of the effluent before its biological treatment.…”

Removal of imidazolium- and pyridinium-based ionic liquids by Fenton oxidation

“…On the other hand, for effluents of Fenton oxidation with lower H2O2 doses, the concentration of nitrite and nitrate became more similar (4 mg L -1 for NO2and 4.5 mg L -1 for NO3 -), indicating an increase in the oxidation rate was related with the high conversion of nitrite in nitrate. For all the H2O2 doses, the nitrogen mass balance was incomplete, due to the possible formation of nitrogen-containing by-products as chloramines (Vidales et al 2016) and NOx species in gas phase (Garcia-Segura et al 2017).…”

“…Finally, the chlorine balance was almost completely closed. Probably, the unidentified fraction could corresponds to the formation of chloramines (Vidales et al 2016) or other chlorine species. Comparing these results with those described for Fenton oxidation of ionic liquids separately, it can be concluded that the presence of both compounds lead to similar results in terms of IL removal, mineralization of the starting compounds and COD conversion and no synergistic effect, interference or competition between HmimCl and BmpyrCl was observed.…”

On the performance of HOCl/Fe2+, HOCl/Fe2+/UVA, and HOCl/UVC processes using in situ electrogenerated active chlorine to mineralize the herbicide picloram

“…where Δ[TOC] t is the measured TOC removal (mg L −1 ) after a certain treatment time, t (h), n the number of exchanged electrons (see Eq. 2and assuming that only NO 3 − ions are produced [37]) considering that the applied electric charge was consumed solely by the mineralization process, F the Faraday constant (96485C mol −1 ), V the solution volume (L), 4.32 × 10 7 is a compounded conversion factor…”