Preparation of Cu-Loaded Biomass-Derived Activated Carbon Catalysts for Catalytic Wet Air Oxidation of Phenol

Anchoring catalytic wet air oxidation to biomass waste management with focus on distillery stillage

Wet air oxidation is an advanced chemical reaction process involving the use of moisture and air and is applied to purposes such as to degrade existing and emerging pollutant, especially to waste types of too liquid for combustion process but too solid for biodigestion. The traditional wet air oxidation process operates on a temperature of 150-300 °C and a pressure of 0.5-20 bar whereas the supercritical oxidation applies a temperature > 374 °C and a pressure of > 2.2 bar. Wet air oxidation process technology is well matured; however, it is still a flashpoint to researchers, especially on economizing the system from applying catalysts and their supports. Wet air oxidation process catalysis is performed to improve reaction efficiency performing it at lower temperature and pressure. Such catalyzed processes are preferred based on the catalyst's selective activity and stability as well as recoverability while economizing the process energy requirement. Consequently, a catalyzed subcritical wet air oxidation is considered as an environmentally friendly and economically feasible alternative. In the past decades, plenty of studies have been done on wet air oxidation but are performed piece by piece, not comprehensively. Additionally, biologically coupled wet air oxidation of pollutants is not well revised. This paper uniquely elucidates the recent advancements in wet air oxidation and it is integral with other waste treatments to an environmentally friendly management. Structurally, this review presents the basics and state of the art of wet air oxidation, the chemical process, its catalytic and catalyst support progresses, and its application in waste and bioenergy with focus to stillage.

Copper-supported thiol-functionalized cellulose as a paper-based catalyst for imine synthesis

This study presents an appealing approach to sustainable catalysis using cellulose filter paper as a support for copper-catalyzed reactions. The paper was functionalized with thiol groups through a reaction with thioglycolic acid, which served a dual purpose: partially reducing Cu(II) to Cu(I) and stabilizing active copper species via Cu-S interactions. Spectroscopic analysis confirmed the formation of highly dispersed multi-valent Cu2O/CuO on the thiol-functionalized cellulose, resulting in a highly efficient copper catalyst. This catalyst demonstrated excellent performance in the oxidative coupling of various amines to imines, achieving yields of 39-99% within 10-30 min. A key advantage of this system is its reusability; the catalyst maintained remarkable stability and activity over ten reaction cycles with straightforward recovery. This paper-based catalyst offers a promising strategy for eco-friendly and cost-effective synthetic processes, with significant implications for green chemistry and industrial applications.

Enhanced treatment of multiphase extraction wastewater from contaminated sites with Cu-Ce modified GAC three-dimensional electrodes

A three-dimensional (3D) electrode system is widely recognized as an effective technology for enhancing electrocatalytic effect. In this study, Cu-Ce modified granular activated carbon (GAC) particle electrodes were prepared using the impregnation method and applied to handle multiphase extraction wastewater. Structural and electrochemical characterization revealed that while the specific surface area of Cu-Ce/GAC decreased by 13.94%, the active area was 2.6 times greater than that of GAC. In addition, the influences of distinct impregnation concentrations, calcination temperatures, and calcination times on the performance of Cu-Ce/GAC electrodes were investigated. The results suggested the optimal preparation conditions of 15 mmol/L, 500 °C and 2 h. Under these conditions, the Cu-Ce/GAC electrode achieved a 92.39% removal of chemical oxygen demand (COD) from a multi-extract of groundwater, with an energy consumption of 13.44 kWh/(kg∙COD). The degradation efficiency improved by 62% compared to the conventional 2D system, while energy consumption decreased by 60%. The main organic pollutants in the multiple extracts, including benzene, toluene, dichloromethane, trichloromethane, were removed at rates exceeding 90% after 60 min treatment. This study yields a methodological and engineering approach for treating multiple extracts wastewater from contaminated groundwater.

Oxygen activation and transfer for catalytic wet-air oxidation of wastewater: a short review

With the rapid growth of population and industrial production, wastewater pollution has become a major environmental issue. Wastewater pollution also poses a threat to water resources and human health. Catalytic wet-air oxidation (CWAO) is one of the most economical and environmentally friendly technologies, especially for the treatment of toxic and non-biodegradable pollutants in wastewater. Various heterogeneous catalysts have been reported for use in wastewater treatment; however, most of these catalysts are effective only under high temperatures and high pressures. The increasing demand for the removal of wastewater pollutants necessitates the development of low-temperature, high-efficiency catalysts for CWAO technology. To achieve this, the ability of the catalyst to activate O2 and transfer active oxygen species plays a key role in determining the catalytic performance. In this review, we summarize recent advances in various noble and non-noble metal catalysts, oxide catalysts and carbon catalysts for CWAO reactions, focusing on the positive effect of O2 activation and transfer on catalytic performance. We also propose future directions for developing novel CWAO catalysts by optimizing the catalyst's ability to activate O2 and transfer active oxygen species.

Modified high-efficiency carbon material for deep degradation of phenol by activating persulfate

A series of cobalt-nitrogen modified catalysts were prepared and applied to the degradation of phenol. The Mott Schottky catalyst (CoO/NGr@C) with high pyridine nitrogen content was designed to activate potassium peroxodisulfate (PDS) to generate active free radicals for phenol degradation. The structural properties of the materials are analyzed by XPS, TEM and then the charge density calculation is performed by DFT, which proves the existence of the highly active interface effect. Co-N-C_MCM-41 can only degrade phenol into benzoquinone and it is difficult to achieve further degradation of benzoquinone, while the modified CoO/NGr@C can achieve deep mineralization of the intermediate benzoquinone through UV spectrum. EPR was used to prove that both hydroxyl radicals and sulfate radicals exist in the degradation process of phenol. Through the DFT simulation calculation of the material, it is proved that the existence of carbon activated by nitrogen and the electron rearrangement between cobalt and nitrogen-rich carbon lead to the catalytic activity of the material. The degradation conditions of phenol were optimized and the reaction kinetics of further phenol degradation were studied. The activation energy of phenol degradation on CoO/NGr@C is calculated to be 34.38 kJ mol^-1.