Facile ammonium oxidation to nitrogen gas in acid wastewater by in situ photogenerated chlorine radicals

A Bipolar Membrane-Integrated Electrochlorination Process for Highly Efficient Ammonium Removal in Mature Landfill Leachate: The Importance of ClO• Generation

“…for calculations. It is apparent that the [HO • ] SS and [Cl • ] SS remained at relatively low values and did not vary much, as they are considered to have ultrashort lifetimes and are the precursors of ClO • and Cl 2 •– . − The concentrations of the latter two species considerably increased in all the EC reactors, and the values were closely linked to the type of reactor architecture. For instance, the [HO • ] SS , [Cl • ] SS , [ClO • ] SS , and [Cl 2 •– ] SS in the BPM-EC system were calculated to be 14.5 × 10 –14 , 3.7 × 10 –14 , 5.0 × 10 –12 , and 3.3 × 10 –12 M, respectively, showing ClO • as the high-abundance species in accordance with the aforementioned results.…”

“…Previous studies have shown that the reactions between FC and Cl • also contribute to the formation of ClO • (eqs and ). , Its high reactivity and selectivity toward ammonium oxidation to nitrogen even at acidic pH values is noteworthy (eq ). ,, Small amounts of nitrate resulting from HClO-mediated ammonium oxidation (eq ) are directed to the cathode via internal recycling and expected to be reduced by the electrons and/or adsorbed H (H*) from the cathode (eqs and ). , H 2 O → H + + OH − OH − + MO x → ≡MO x false( normalHO • false) + e − Cl − + ≡MO x false( normalHO • false) → Cl • + OH − + MO x …”

“…Nevertheless, operational experiences have shown us that one of the outstanding issues in this technique is related to the enormous drop in pH as a consequence of protons released from ammonium oxidation, which ultimately deteriorates NH 4 + -N removal efficiency and causes severe corrosion of metal materials (e.g., the Cu current collector; see Figure S1) due to the volatilization of Cl 2 . This motivates us to develop a strategy to promote ammonium oxidation kinetics by either elevating the pH in the restricted area or converting FC into chlorine radicals, because the latter species can accelerate ammonium oxidation at high rate constants (10 7 –10 9 M –1 s –1 ). − …”

Metal-encapsulated carbon nanotube arrays for enhancing electrocatalytic nitrate reduction in wastewater: importance of lying-down to standing-up structure transition

“…5b presents that the presence of NaCl significantly suppressed ammonium selectivity (decreasing from 90% in the absence of NaCl to 73%, 0.9%, and 0% with 0.5, 1, and 1.5 mg L −1 NaCl, respectively) because of the electrochemical breakpoint chlorination reaction between ammonium and active chlorine species. 35–37 The increasing NaCl concentration did not alter the rate of nitrate removal. The increase in the reactor volume was found to negatively affect the reaction rate (Fig.…”

Construction of Hexagonal Prism-like Defective BiOCL Hierarchitecture for Photocatalytic Degradation of Tetracycline Hydrochloride

“…The newly discovered vibration band at 95 cm −1 is produced from the E g and A 1g vibration modes of Bi metal, revealing that 3D-BiOCl contains crystal defects as well as trace amounts of reduced Bi [ 38 ]. Additionally, the vibration band broadening and position shifting may be related to the novel shape and oxygen vacancy of the 3D-BiOCl sample [ 39 , 40 ]. A similar phenomenon was also observed in ultra-thin and defective BiOCl [ 41 ].…”