Electrochemical degradation of indigo carmine, P-nitrosodimethylaniline and clothianidin on a fabricated Ti/SnO2-Sb/Co-βPbO2 electrode: Roles of radicals, water matrices effects and performance

Insights into electrochemical oxidation of tris(2-butoxyethyl) phosphate (TBOEP) in aquatic media: Degradation performance, mechanisms and toxicity changes of intermediate products

Tris (2-butoxyethyl) phosphate (TBOEP) has gained significant attention due to its widespread presence and potential toxicity in the environment. In this study, the degradation of TBOEP in aquatic media was investigated using electrochemical oxidation technology. The anode Ti/SnO2-Sb/La-PbO2 demonstrated effective degradation performance, with a reaction constant (k) of 0.6927 min-1 and energy consumption of 1.24 kW h/m3 at 10 mA/cm2. CV tests, EPR tests, and quenching experiments confirmed that indirect degradation is the main degradation mechanism and ·OH radicals were the predominant reactive species, accounting for up to 93.8%. The presence of various factors, including Cl-, NO3-, HCO3- and humic acid (HA), inhibited the degradation of TBOEP, with the inhibitory effect dependent on the concentrations. A total of 13 intermediates were identified using UPLC-Orbitrap-MS/MS, and subsequent reactions led to their further degradation. Two main degradation pathways involving bond breaking, hydroxylation, and oxidation were proposed. Both Flow cytometry and the ECOSAR predictive model indicated that the intermediates exhibited lower toxic than the parent compound, resulting in a high detoxification rate of 95.9% for TBOEP. Although the impact of TBOEP on the phylum-level microbial community composition was found to be insignificant, substantial alterations in bacterial abundance were noted when examining the genus level. The dominant genus Methylotenera, representing 17.4% in the control group, decreased to 6.9% in the presence of TBOEP and slightly increased to 8.7% in the 4-min exposure group of degradation products. Electrochemical oxidation demonstrated its effectiveness for the degradation and detoxification of TBOEP in aqueous solutions, while it is essential to consider the potential impact of degradation products on sediment microbial communities.

Preparation of Ti/SnO2-Sb/La-βPbO2 electrode and its application in the degradation of some pollutants including prednisolone and 8-Hydroxyquinoline

In this work, a novel La-doped βPbO₂ (Ti/SnO₂-Sb/La-βPbO₂) was prepared using electrodeposition method and applied to the degradation of prednisolone (PRD), 8-Hydroxyquinoline (8-HQ), and other typical organic pollutants. Compared with the conventional electrode Ti/SnO₂-Sb/βPbO₂, La₂O₃ doping enhanced oxygen evolution potential (OEP), reactive surface area, stability and repeatability of the electrode. The 10 g L^-1 of La₂O₃ doping exhibited the highest electrochemical oxidation capability of the electrode with [•OH]ss being determined at 5.6 × 10^-13 M. The quenching experiments were conducted to confirm the main oxidizing species (here: •OH) in the electrochemical process. The study showed that the pollutants were removed in the electrochemical (EC) process with different degradation rates and indicated that the second-order rate constant of organic pollutants towards •OH (k_OP,•OH) has a linear relationship with the degradation rate of organic pollutants (k_OP) in the electrochemical process. Another new finding in this work is that a regression line of k_OP,•OH and k_OP can be used to estimate k_OP,•OH of an organic chemical, which cannot be determined using the competition method. k_PRD,•OH and k_8-HQ,•OH were determined to be 7.4 × 10⁹ M^-1 s^-1 and (4.6-5.5) × 10⁹ M^-1 s^-1, respectively. Compared with conventional supporting electrolyte (like SO₄^2-), H₂PO₄^- and HPO₄^2- improved k_PRD and k_8-HQ by 1.3-1.6-fold, while SO₃^2- and HCO₃^- inhibited k_PRD and k_8-HQ significantly, down to 80%. Additionally, the degradation pathway of 8-HQ was proposed based on the detection of intermediates from GC-MS.