Construction of heterojunction photoanode via facile synthesis of CoOx/CN nanocomposites for enhanced visible-light-driven photoelectrochemical degradation of clofibric acid

An insight into the role of experimental parameters in advanced oxidation process applied for pharmaceutical degradation

The advanced oxidation process (AOP) is an efficient method to treat recalcitrance pollutants such as pharmaceutical compounds. The essential physicochemical factors in AOP experiments significantly influence the efficiency, speed, cost, and safety of byproducts of the treatment process. In this review, we collected recent articles that investigated the elimination of pharmaceutical compounds by various AOP systems in a water medium, and then we provide an overview of AOP systems, the formation mechanisms of active radicals or reactive oxygen species (ROS), and their detection methods. Then, we discussed the role of the main physicochemical parameters (pH, chemical interference, temperature, catalyst, pollutant concentration, and oxidant concentration) in a critical way. We gained insight into the most frequent scenarios for the proper and improper physicochemical parameters for the degradation of pharmaceutical compounds. Also, we mentioned the main factors that restrict the application of AOP systems in a commercial way. We demonstrated that a proper adjustment of AOP experimental parameters resulted in promoting the treatment performance, decreasing the treatment cost and the treatment operation time, increasing the safeness of the system products, and improving the reaction stoichiometric efficiency. The outcomes of this review will be beneficial for future AOP applicants to improve the pharmaceutical compound treatment by providing a deeper understanding of the role of the parameters. In addition, the proper application of physicochemical parameters in AOP systems acts to track the sustainable development goals (SDGs).

Plasma-assisted assembly of Co3O4/TiO2-NRs for photoelectrocatalytic degradation of bisphenol A in solution and muddy systems

Herein, Co3O4/TiO2-NRs electrodes with excellent photoresponse have been prepared via the plasma-assisted modification of Co3O4 on TiO2. With the combination of Co3O4 and TiO2, the composite electrode exhibited a red-shift phenomenon and the absorption of UV and visible light were enhanced to improve the light utilization efficiency. The Mott-Schottky diagram showed that a P-N heterojunction was successfully formed between Co3O4 and TiO2 on the electrode, which inhibited the recombination of electrons and holes, and had a high photocurrent density. In our photoelectrocatalysis (PEC) degradation experiments, the degradation rates of bisphenol A (BPA) by Co3O4/TiO2-NRs electrode in Na2SO4 and simulated seawater system reached 69.44 and 100%, respectively. The important role of ·O2-, ·OH, h+, and active chlorine (Cl·, HClO/ClO-, and Cl2) on the Co3O4/TiO2-NRs electrode during the degradation of BPA in simulated seawater was revealed. In addition, PEC combined with electrokinetic (EK) studies with the Co3O4/TiO2-NRs electrode were used for the degradation of BPA in muddy water, initially expanding the application scope of the PEC performance of the Co3O4/TiO2-NRs electrode for pollutants degradation, and had great potential for the subsequent treatment of muddy water pollutants.

Design strategies and mechanisms of g-C3N4-based photoanodes for photoelectrocatalytic degradation of organic pollutants in water

Emerging photoelectrocatalytic (PEC) systems integrate the advantages of photocatalysis and electrocatalysis and are considered as a promising technology for solving the global organic pollution problem in water environments. Among the photoelectrocatalytic materials applied for organic pollutant degradation, graphitic carbon nitride (CN) has the combined advantages of environmental compatibility, stability, low cost, and visible light response. However, pristine CN has disadvantages such as low specific surface area, low electrical conductivity, and high charge complexation rate, and how to improve the degradation efficiency of PEC reaction and the mineralization rate of organic matter is the main problem faced in this field. Therefore, this paper reviews the progress of various functionalized CN used for PEC reaction in recent years, and the degradation efficiency of these CN-based materials is critically evaluated. First, the basic principles of PEC degradation of organic pollutants are outlined. Then, engineering strategies to enhance the PEC activity of CN (including morphology control, elemental doping, and heterojunction construction) are focused on, and the structure-activity relationships between these engineering strategies and PEC activity are discussed. In addition, the important role of influencing factors on the PEC system is summarized in terms of mechanism, to provide guidance for the subsequent research. Finally, suggestions and perspectives are provided for the preparation of efficient and stable CN-based photoelectrocatalysts for practical wastewater treatment applications.

Bi@BiOx(OH)y modified oxidized g-C3N4 photocatalytic removal of tetracycline hydrochloride with highly effective oxygen activation

A novel Bi@BiOx(OH)y-modified oxidized g-C₃N₄ photocatalyst was successfully prepared via wet chemical reduction under alkaline conditions for the tetracycline hydrochloride removal. The prepared materials were characterized comprehensively and fully. Sufficient structural representation analyses confirmed the successful loading of Bi in the form of Bi@BiOx(OH)y complex beads. Based on basic photocatalytic studies, 10% (mass percentage) was found to be the best metal Bi loading. DRS, PL, transient photocurrent and EIS have explored the improvement of the photochemical properties of materials by loading Bi@BiOx(OH)y groups, particularly the improvement of photocatalytic properties by the SPR effect and electron traps. 10%Bi-OxCN exhibited the most suitable particle size of nonagglomerated Bi-metal groups, the largest specific surface area (43.53 m² g^-1), the most adsorption sites and the most significant photocurrent (8.694 × 10^-2 mA cm^-2) (7.78 times that of OxCN). This indicated that 10%Bi-OxCN had good adsorption capacity and excellent light response capability. In addition, 10%Bi-OxCN showed the best tetracycline hydrochloride removal efficiency (96.0%), with ∙O₂^- as the main active substance and ¹O₂ as the second most important substance made of ∙O₂^- and h⁺. The excellent photocatalytic effect and good reusability were fundamentally dependent on the modification of OxCN by Bi@BiOx(OH)y groups to produce a large number of active substances (including the separation efficiency of electron-hole pairs and the generation efficiency of ∙O₂^- and ¹O₂). These advantages are all related to the high specific surface area, a large number of active sites, narrow bandgap width, Bi-SPR effect, and BiOx(OH)y electron trap caused by successful loading of Bi groups.