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 βPbO 2 (Ti/SnO 2 –Sb/La-βPbO 2 ) 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/SnO 2 –Sb/βPbO 2 , La 2 O 3 doping enhanced oxygen evolution potential (OEP), reactive surface area, stability and repeatability of the electrode. The 10 g L −1 of La 2 O 3 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 × 10 9  M −1  s −1 and (4.6–5.5) × 10 9  M −1  s −1 , respectively. Compared with conventional supporting electrolyte (like SO 4 2− ), H 2 PO 4 − and HPO 4 2− improved k PRD and k 8-HQ by 1.3–1.6-fold, while SO 3 2− and HCO 3 − 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.