Synergetic Effect of Ultrasound, the Heterogeneous Fenton Reaction and Photocatalysis by TiO₂ Loaded on Nickel Foam on the Degradation of Pollutants

Degradation of nitrogen-containing hazardous compounds using advanced oxidation processes: A review on aliphatic and aromatic amines, dyes, and pesticides

Nitrogen-containing amino and azo compounds are widely used in textile, agricultural and chemical industries. Most of these compounds have been demonstrated to be resistant to conventional degradation processes. Advanced oxidation processes can be effective to mineralize nitrogen-containing compounds and improve the efficacy of overall treatment schemes. Due to a global concern for the occurrence of toxic and hazardous amino-compounds and their harmful degradation products in water, it is important to develop technologies that focus on all the aspects of their degradation. Our focus is to present a state-of-the-art review on the degradation of several amine- and azo-based compounds using advanced oxidation processes. The categories reviewed are aromatic amines, aliphatic amines, N-containing dyes and N-containing pesticides. Data has been compiled for degradation efficiencies of each process, reaction mechanisms focusing on specific attack of oxidants on N atoms, the effect of process parameters like pH, initial concentration, time of treatment, etc. and identification of intermediates. Several AOPs have been compared to provide a systematic overview of available literature that will drive essential aspects of future research on amine-based compounds. Ozone is observed to be highly reactive to most amines, dyes and pesticides, followed by Fenton processes. Degradation of amines is highly sensitive to pH and mechanisms differ at different pH values. Cavitation is a promising alternative pre-treatment method for cost reduction. Hybrid methods under optimized conditions are demonstrated to give synergistic effects and must be tailored for specific effluents in question. In conclusion, even though nitrogen-containing compounds are recalcitrant in nature, the use of advanced oxidation processes at carefully established optimum conditions can yield highly efficient degradation of the compounds.

Ultra-Highly Efficient Removal of Methylene Blue Based on Graphene Oxide/TiO2/Bentonite Sponge

An ultra-highly efficient Graphene Oxide/TiO₂/Bentonite (GO/TiO₂/Bent) sponge was synthesized using an in situ hydrothermal method. GO/TiO₂/Bent sponge with a GO mass concentration of 10% exhibited the highest treatment efficiency of methylene blue (MB), combining adsorption and photocatalytic degradation, and achieved a maximum removal efficiency of 100% within about 70 min. To further prove the ultra-high removal capacity of the sponge, the concentration of MB in water increased to ten times the original concentration. At so high a MB concentration, the removal rate was still as high as 80% in 90 min. The photocatalytic mechanism of GO/TiO₂/Bent sponge was discussed through XPS, PL and radicals quenching experiments. Here Bent can immobilize TiO₂ and react with a photo-generated hole to increase the amount of hydroxyl radical; effectively enhancing the degradation of MB.GO sponge enlarges the sensitivity range of TiO₂ to visible light by increasing the charge separation of TiO₂ and reducing the recombination of photo-generated electron–hole pairs. Additionally, GO sponge with an interconnected porous structure provides an effective platform to immobilize TiO₂/bent and makes them be easily recovered. The as-prepared sponge develops a simple and cost-effective strategy to realize the ultra-highly efficient treatment of dyes in wastewater.

Effective Degradation of Rh 6G Using Montmorillonite-Supported Nano Zero-Valent Iron under Microwave Treatment

Nano zero-valent iron has drawn great attention for the degradation of organic dyes due to its high reactivity, large specific surface area, lightweight, and magnetism. However, the aggregation and passivation of iron nanoparticles may prohibit the wide use of it. A new composite material was prepared by loading nano zero-valent iron (nZVI) on montmorillonite (MMT) to overcome the above shortcomings and it was further used for the removal of Rhodamine 6G (Rh 6G) under microwave treatment in the present work. The effects of various parameters, including the initial concentration of Rh 6G, microwave power, and pH value were investigated. The new composite material (nZVI/MMT) showed an excellent degradation ability for removing Rh 6G, and the removal amount reached 500 mg/g within 15 min. The degradation rate reached 0.4365 min⁻¹, significantly higher than most previous reports using other removal methods for Rh 6G.

Ag nanoparticles supported on nickel foam: a flexible 3D electrode for methanol electrocatalytic oxidation

Ag nanoparticles were prepared on nickel foam electrode coated Nafion membranes for eletrocatalytic oxidation methanol.