Ronn Goei

Construction of WO3–g-C3N4 composites as efficient photocatalysts for pharmaceutical degradation under visible light

Emerging organic contaminants (EOCs) like pharmaceuticals in the environment have become an emerging issue, which pose a threat to human health and environmental biodiversity. Many researchers have devoted their efforts to the development of novel technologies to effectively eliminate such pollutants from water cycles. In this work, we aimed to develop and employ heterogeneous WO3–g-C3N4 as an efficient photocatalyst for antibiotic degradation under visible light irradiation. Synthesis of WO3–g-C3N4 (WCN) composites was optimized with various g-C3N4 dosages and a facile hydrothermal method was used for material preparation. Sulfamethoxazole (SMX), which is one of the most commonly used antibiotics, was utilized as a model pharmaceutical to evaluate the degradation performance of the as-prepared WCN composites under visible light. Results showed that SMX removal efficiency can be largely improved by the WO3–g-C3N4 composites compared to bare WO3. In particular, the photocatalytic efficiency was raised to 91.7% when the optimized material WCN-8 was applied at a dosage of 1.0 g L−1. Such enhanced photocatalytic activity can be ascribed to the formation of direct solid-state Z-scheme heterojunctions between g-C3N4 and WO3, which could improve the photogenerated electron–hole pair separation efficiency as well as the redox capability. At the same time, the larger surface area and better visible light absorption capability can also contribute to the enhanced efficiency.

Mechanistic and thermodynamic studies of oxyanion sorption by various synthetic Mg/Al layered double hydroxides

In this study, Mg/Al layered double hydroxides (LDHs) were investigated for their potential in scavenging several harmful oxyanions from aqueous solution. LDHs could effectively remove oxyanions and the selectivity of LDHs was governed by both the valencies and the ionic radii of the oxyanions. LDHs prepared by the fast coprecipitation with hydrothermal treatment (FCHT) method and sol-gel with solvothermal treatment method (SGST) had higher oxyanion (i.e. arsenate) removal efficiency than those prepared by the conventional routes, owing to their lower carbonate content, higher surface area, larger pore volume, larger pore size, and nanocrystalline characteristic. The sorption of arsenate by FCHT-LDH was found primarily due to anion exchange mechanism and might involve a secondary sorption mechanism. The negative DeltaG degrees for arsenate sorption confirmed the spontaneity of the removal process. The positive values of DeltaH degrees and DeltaS degrees provided further evidence of the anion exchange process in the removal mechanism.

One-step construction of heterostructured metal-organics@Bi 2 O 3 with improved photoinduced charge transfer and enhanced activity in photocatalytic degradation of sulfamethoxazole under solar light irradiation

A facile one-step assembly method was developed for the preparation of metal-organics @Bi2O3 composites for photocatalysis. Two kinds of metal-organics (Ti-bdc and Cu-btc)@Bi2O3 composites were synthesized via the coordination of btc3-/bdc2- and metal ions (Ti4+/Cu2+) as well as OH on the surface of Bi2O3. Compared with pure Bi2O3, Ti-bdc@Bi2O3 shows a 1.7 times higher photocatalytic activity in the degradation of sulfamethoxazole (SMX) under a simulated solar irradiation with a cumulative removal of 62% within 60 min. The high photocatalytic activity could be attributed to the high charge separation, enhanced electron transfer as well as the low recombination rate of photo-generated electrons and holes due to the construction of hetero-structures. The stability test showed that Ti-bdc@Bi2O3 is more stable in water than Cu-btc@Bi2O3. Furthermore, through the radical-trapping experiments and main intermediates detection, it is demonstrated that the photo-generated holes as well as the OH and O2- formed dominate the photocatalytic decomposition of SMX. These findings demonstrate the potential usage of a facile method to synthesize metal-organics and metal oxides composites, some of which possess high water stability and thus could be employed for water treatment.

CHAPTER 5:Combined Photocatalysis–Separation Processes for Water Treatment Using Hybrid Photocatalytic Membrane Reactors

This chapter presents an overview of photocatalysis and its synergistic coupling with separation process to realize process intensification in a hybrid photocatalytic membrane. The review specifically covers photocatalytic ceramic membranes since the ceramic membrane has high permeability, good thermal, mechanical, chemical and biological stability, excellent UV resistance, and durability. Examples of novel photocatalytic ceramic membranes, the fabrication techniques and their performances are discussed. The challenges of scaling up the water treatment process incorporating a hybrid photocatalytic membrane reactor are addressed and the possible solutions covered include advances in photonic technology, innovative photocatalytic membrane reactor module, and proper treatment process design.