2D–3D graphene-coated diatomite as a support toward growing ZnO for advanced photocatalytic degradation of methylene blue

Defective multi-element hydroxides nanosheets for rapid removal of anionic organic dyes from water and oxygen evolution reaction

Water pollution by dyes is one of the biggest environmental problems. Adsorption technology has been widely used in wastewater treatment. In this work, high-entropy concept is used to design surface defective hydroxides realizing the rapid removal of dyes from water. Multi-element hydroxides (MEHs) containing three (CoMnNi, MEH-Ternary), four (CoMnNiZn, MEH-Quaternary), and five (CoMnNiZnFe, MEH-Quinary) metal elements are successfully synthesized through a polyol process. These as-synthesized MEHs are composed of nanosheets with a brucite-like structure. Along with the increase in compositional complexity (i.e., configurational entropy), the thickness of the nanosheets in these MEHs decreases, while the degree of surface defects increase. These surface defects are probably the active sites for anionic dyes adsorption, suggesting rapid adsorption kinetics with shortened diffusion path length. For MEH-Quinary in 0.2 mM Congo red (CR) and MEH-Ternary in 0.4 mM methyl orange (MO) aqueous solutions, respectively, high removal efficiency > 99.0% is achieved in the first 30 s. Their pseudo-second-order rate constants are two orders of magnitude higher than that of activated carbon and hydrotalcite. MEH-Quinary has maximum CR and MO adsorption quantity of 546.4 and 404.9 mg g^-1, respectively, by Langmuir model. The MEH-Quinary is also a potential electrocatalyst for oxygen evolution reaction.

Active Packaging Material Based on Immobilized Diatomaceous Earth/Zinc Oxide/High-Density Polyethylene Composite for Sea Food and Products

One of the key factors of supporting the rapidly expanding seafood product industry in terms of quality control is the utilization of active packaging materials. Microorganisms are primarily responsible for the perishability and rapid disintegration of seafood. The incorporation of an inorganic compound, such as silica-based diatomaceous earth (DE), and a metal oxide, such as zinc oxide (ZnO), is proposed to develop active packaging materials with excellent antibacterial activity, minimized fishy odor, and brittleness at subzero temperatures. The mechanical, morphological, and physicochemical properties of these materials were investigated. The results show that the addition of DE/ZnO improved the antibacterial activity of high-density polyethylene (HDPE) samples by up to approximately 95% against both gram-positive and -negative bacteria. Additionally, it enhanced the Izod strength and stability at subzero temperatures of the samples. The odor evaporation test revealed that trimethylamine can be minimized in proportion to increasing DE/ZnO composite concentration. As a result, the development of active packaging materials from DE/ZnO composites is an emerging polymeric packaging technology for seafood products, wherein packaging and seafood quality are linked.

A review of graphene-based semiconductors for photocatalytic degradation of pollutants in wastewater

Water is the lifeblood of all living things; we often overlook the fact that the water cycle and the life cycle are inextricably linked. However, it has become contaminated as a result of industrialization, which has impacted the ecosystem by emitting numerous dyes, organic solvents, petroleum products, heavy metals, chemicals, diseases, and solid wastes. The absence of treatment in reusing wastewater is the root of the issues. Hence it is essential to treat the water to preserve the ecosystem and also for human health. In recent years, graphene-based photocatalysts are attracted much in the waste water treatment process due to their outstanding physical, chemical, and mechanical properties. Since in the graphene-based photocatalyst, graphene has exceptional electron conductivity, a broad range of light absorption, a large surface area, and a high adsorption capacity. When it is integrated into metals, metal-containing nanocomposites, semiconductor nanocomposites, polymers, MXene, and other compounds, it can greatly boost the photocatalytic activity towards the photo destruction of contaminants. Hence in this review, water pollution, methods of waste water treatment, fundamental principles of photocatalysis, the photocatalytic activity of other materials in wastewater treatment, and how the photocatalytic efficiency against the removal of organic dyes can be enhanced when coalesced with graphene are detailed.