ABSTRACT
Oxygen vacancies are crucial to the production of reactive oxygen species (ROS) in the metal oxide electrocatalytic membrane (MOx EM) process. Here, using cathodic TiOx EM as a model, we thoroughly reveal the roles of oxygen vacancies in ROS generation and transformation. Oxygen vacancies significantly promote H2O2 and â¢OH production at low concentrations (increment <35%) but inhibit their production at high concentrations (increment >35%). Electrochemical analysis discloses that the enhancement of ROS production profits from the acceleration of charge transfer kinetics by both bulk and surface oxygen vacancies, whereas we attribute the decline in ROS production to the strong adsorption of ROS by surface oxygen vacancies. It is strongly supported by theoretical calculations that reveal the promoted adsorption of *OOH and *OH by oxygen vacancies, which intensifies the capture and scavenging of H2O2 and â¢OH. Moreover, the gradual increase of interaction time between ROS and oxygen vacancies (from â¼1 to â¼5 s) notably reduces the generation and transformation efficiency of ROS, further highlighting the detrimental impact of oxygen vacancies. In summary, oxygen vacancies show "two faces" toward ROS generation and transformation, acting as ROS promoters at low concentrations but inhibitors at high concentrations. A medium oxygen vacancy concentration is preferred for ROS production, thus causing impressive pollutant removal (>95% removal of bisphenol A within 1.2-1.5 s at 360-440 LMH). This study provides guidance on regulating ROS generation and transformation by manipulating the oxygen vacancy concentration to enhance the decontamination efficiency of MOx EMs.
Subject(s)
Hydrogen Peroxide , Oxygen , Reactive Oxygen Species , AdsorptionABSTRACT
A low-cost natural silicate ore supported Fe2O3 (FeSO) was synthesized for catalytic ozonation of sulfamethoxazole (SMX). XRD, SEM-EDS, BET, FTIR and XPS results of the FeSO catalyst confirmed that the natural silicate ore was successfully modified with iron oxide. The effects of key factors, such as catalyst dosage, initial solution pH, reaction temperature, inorganic anions and initial concentration, on ozonation degradation were systemically investigated. The degradation rate of SMX (20 mg L-1) was 88.1% after 30 min, compared with only 35.1% SMX degradation rate in the absence of the catalyst, and the total organic carbon (TOC) removal reached 49.1% after 60 min. Reaction mechanisms revealed that surface hydroxyl groups of FeSO were a critical factor for hydroxyl radical (ËOH) production leading to fast SMX degradation in the ozone decomposition process. The degradation products were detected, and the possible pathways of SMX were then proposed. This study provides guidance for preparing a low-cost catalyst and analyzing the degradation products and pathways of SMX in the ozonation process, which is of significance in practical industrial applications.
ABSTRACT
Based on the finite element theory, a joint-plane modeling method is employed to connect the corresponding nodes at the joint surface of the woodworking computer numerical control (CNC) machining center bed with a 2-node 12-degree-of-freedom unit. A spatial element model is established, which can show the state of the nodes between joint surfaces when they are stretched, compressed, or twisted; and it can help build a woodworking CNC machining center on a finite element model of bed with the characteristics of the joint surface. The simulated analysis is performed on the model and is compared with the result of simulated analysis on the bed model that ignores the characteristics of the joint surface and modal experiment. The comparison verifies the effectiveness of the modeling method based on the characteristics of the joint surface. The weak link of the machine bed structure is analyzed and optimized. The natural frequency of the bed is improved by2.55% ~ 11.3%. The displacement is reduced by a maximum of 19.4%, and dynamic performance of the bed is improved.
