boron and benzotriazole

Electrochemical systems were built to investigate the degradation of benzotriazole (BTA) on boron-doped diamond (BUU) and PbO2 anodes and give an insight into the mineralization ability of two electrodes in terms of the amount and activity of hydroxyl radicals. Results of bulk electrolysis showed that both BDD and PbO2 displayed perfect BTA degradation performance after 12 hours' electrolysis, with the removal percentages of 99. 48% and 98. 36%, respectively, while the mineralization ability of BDD was much stronger than that of PbO2, with the efficiency of 87. 69% for BDD and 35. 96% for PbO2. Less hydroxyl radical and hydrogen production in BDD system suggested the less amount of active sites on BDD surface, thus further verified that the generated hydroxyl radical amount was not the primary factor determining the mineralization ability of anodes. However, BDD displayed larger binding energy of adsorbed oxygen and thinner adsorption layer than those of PbO2, indicating that the BDD electrode surface was of greater catalytic activity, thus the generated hydroxyl radicals were more free, which was the key to its better mineralization ability.

Topics: Boron; Diamond; Electrodes; Electrolysis; Hydroxyl Radical; Lead; Oxidation-Reduction; Oxides; Oxygen; Triazoles

Nitrogen-heterocyclic compounds (NHCs) are toxic and bio-refractory contaminants widely spread in environment. This study investigated electrochemical degradation of NHCs at boron-doped diamond (BDD) anode with particular attention to the effect of different number and position of nitrogen atoms in molecular structure. Five classical NHCs with similar structures including indole (ID), quinoline (QL), isoquinoline (IQL), benzotriazole (BT) and benzimidazole (BM) were selected as the target compounds. Results of bulk electrolysis showed that degradation of all NHCs was fit to a pseudo first-order equation. The five compounds were degraded with the following sequence: ID>QL>IQL>BT>BM in terms of their rates of oxidation. Quantum chemical calculation was combined with experimental results to describe the degradation character of NHCs at BDD anode. A linear relationship between degradation rate and delocalization energy was observed, which demonstrated that electronic charge was redistributed through the conjugation system and accumulated at the active sites under the attack of hydroxyl radicals produced at BDD anode. Moreover, atom charge was calculated by semi empirical PM3 method and active sites of NHCs were identified respectively. Analysis of intermediates by GC-MS showed agreement with calculation results.

Topics: Benzimidazoles; Boron; Diamond; Electrochemical Techniques; Electrodes; Heterocyclic Compounds; Hydroxyl Radical; Indoles; Isoquinolines; Nitrogen; Oxidation-Reduction; Quinolines; Triazoles; Waste Disposal, Fluid; Water Pollutants, Chemical