Electrochemical mineralization of 1-naphthol and 2-naphthol using boron-doped diamond anodes: Factor analysis and mechanisms study

Abstract 1-naphthol (1-NAP) and 2-naphthol (2-NAP) are both hazardous pollutants which pose great threat to our living environment. In the current work, a comparative investigation on the electrochemical mineralization of 1-NAP and 2-NAP using boron-doped diamond (BDD) anode was presented. Experiments were carried out using synthetic 1-NAP or 2-NAP solutions containing Na2SO4 as supporting electrolyte. A two-level factorial design methodology was adopted to optimize the mineralization process, six mathematical models were thus constructed and used to explore the structure-property relation involved. The results obtained suggested that 1-NAP was easier and faster to break down than 2-NPA under the same oxidation conditions, which were in line with the outcome obtained from cyclic voltammetry, HPLC and TOC measurements. To understand the destruction mechanism, the electron structures of 1-NAP and 2-NAP were further examined by the quantum chemistry calculations with density functional theory. It was also found that the results from frontier orbital analysis could well explain the differing mineralization performances recorded in BDD anode cell. Finally, with the aid of LC/MS analysis, the oxidation pathways of 1-NAP or 2-NAP on BDD anodes were proposed.