Complete mineralization of acetic acid using catalytic ozonation with a high energy efficiency enhanced by MnO2/γ-Al2O3

The complete mineralization of acetic acid in a biodegradation process is difficult due to the α-position methyl on the carboxyl group of acetic acid. This study explores the complete oxidation of acetic acid by catalytic ozonation. Metal oxides of MnO2, Co3O4, Fe3O4, and CeO2 loaded on γ-Al2O3 power were used as the catalysts. The experimental results showed that MnO2/γ-Al2O3 catalyst had the best mineralization performance for acetic acid. Typically, the mineralization of acetic acid is as high as 88.4% after 300 min ozonation of 100 mL of 1.0 g L‒1 acetic acid catalysed by 3.0 g 1.0wt.% MnO2/γ-Al2O3 catalyst powder with an energy efficiency of 15 g kWh‒1. However, without a catalyst, the mineralization of acetic acid is only 33.2% with an energy efficiency of 5.1 g kWh−1. The effects of MnO2 loading, catalyst dosage, acetic acid concentration, O3 concentration, ozonation temperature, and initial pH value of the acetic acid solution were systematically investigated. Radical quenchers and in-situ DRIFTS analyses indicated that •OH radical and reactive oxygen species on catalyst surface played an important role in the ozonation of acetic acid to CO2 and H2O. The mechanism of acetic acid oxidation on MnO2/γ-Al2O3 is proposed.

Decomposition of diclofenac in sewage from municipal wastewater treatment plant using ionizing radiation

The decomposition of diclofenac (DCF) in sewage sludge from municipal wastewater treatment plant was investigated. It was found that adsorption of DCF on sludge is about 40%. Compared to previous studies, where the degradation yield in aqueous solution was 100%, in those experiments at the dose up to 5 kGy, only 50% of initial DCF concentration of 50 mg L−1 was decomposed in sediment and in solution over the sediment. The experiments were carried out using both gamma radiation and electron beam. It has been observed that DCF in the aqueous phase, above the sediment, was decomposed with the same efficiency using both gamma radiation and electron beam. Whereas for DCF in the sediment, a higher degradation efficiency was found when gamma radiation was applied. This is most likely due to the limited penetration depth of the electron beam into the sludge layer. It was shown that the applied peroxide addition (in a stoichiometric amount needed for complete mineralization of 50 mg L−1 DCF) did not cause increase in yield of DCF decomposition.

Nonthermal Mechanochemical Destruction of POPs

The present chapter is dedicated to all relevant theoretical and application aspects of mechanochemical destruction technology for mineralization of POPs, both stockpiled ones and as contaminants in environmental and waste matrices. It will show that such solid-state technology, realized by high energy milling of POPs with a co-milling solid reagent, can achieve complete mineralization of haloorganics into graphitic/amorphous carbon, carbon oxides, and halides; it takes place at near environmental temperature, thus limiting unintentional formation of dioxins (if treatment conditions are selected carefully); and, in some cases, it can be used to produce useful materials instead of just detoxified waste. The chapter will also give a comprehensive picture of complex mechanochemical destruction mechanism, including mechanochemical activation of the co-milling reagent and the cascade of radical reactions that cause POP molecules mineralization. Finally, technological and economic considerations will be provided, which corroborate the validity and feasibility of the mechanochemical destruction as an effective and safe technology to treat POPs.

Insights on Mycoremediation of Contaminated Soil with Kerosene

Bioremediation of hydrocarbon contaminated soil is inexpensive and involves complete mineralization of organic contaminants to simple organic compounds, carbon dioxide, water and other inorganic compounds by the action of biological agents, according to their metabolic capacities.

Photodegradation of Ciprofloxacin, Clarithromycin and Trimethoprim: Influence of pH and Humic Acids

In view of the rising relevance of emerging pollutants in the environment, this work studies the photodegradation of three antibiotics, evaluating the effects of the pH of the medium and the concentration of dissolved organic matter. Simulated light (with a spectrum similar to that of natural sunlight) was applied to the antibiotics Ciprofloxacin (Cip), Clarithromycin (Cla) and Trimethoprim (Tri), at three different pH, and in the presence of different concentrations of humic acids. The sensitivity to light followed the sequence: Cip > Cla > Tri, which was inverse for the half-life (Tri > Cla > Cip). As the pH increased, the half-life generally decreased, except for Cla. Regarding the kinetic constant k, in the case of Cip and Tri it increased with the rise of pH, while decreased for Cla. The results corresponding to total organic carbon (TOC) indicate that the complete mineralization of the antibiotics was not achieved. The effect of humic acids was not marked, slightly increasing the degradation of Cip, and slightly decreasing it for Tri, while no effect was detected for Cla. These results may be relevant in terms of understanding the evolution of these antibiotics, especially when they reach different environmental compartments and receive sunlight radiation.

Zirconium-Doped Chromium IV Oxide Nanocomposites: Synthesis, Characterization, and Photocatalysis towards the Degradation of Organic Dyes

Degradation of organic dyes and their byproducts by heterogeneous photocatalysts is an essential process, as these dyes can be potentially discharged in wastewater and threaten aquatic and xerophyte life. Therefore, their complete mineralization into nontoxic components (water and salt) is necessary through the process of heterogeneous photocatalysis. In this study, Zr/CrO2 (Zirconium-doped chromium IV oxide) nanocomposite-based photocatalysts with different compositions (1, 3, 5, 7 & 9 wt.%) were prepared by an environmentally friendly, solid-state reaction at room temperature. The as-prepared samples were calcined under air at 450 °C in a furnace for a specific period of time. The synthesis of Zr/CrO2 photocatalysts was confirmed by various techniques, including XRD, SEM, EDX, FT-IR, UV-Vis, and BET. The photocatalytic properties of all samples were tested towards the degradation of methylene blue and methyl orange organic dyes under UV light. The results revealed a concentration-dependent photocatalytic activity of photocatalysts, which increased the amount of dopant (up to 5 wt.%). However, the degradation efficiency of the catalysts decreased upon further increasing the amount of dopant due to the recombination of holes and photoexcited electrons.

Ce3+ triggers fenton-like processes in neutral solutions for effective catechol degradation

Classical Fenton and Fenton-like processes destruct organic pollutants in water non-selectively to complete mineralization. However, the usage of classical Fenton or Fenton-like processes is often limited due to the narrow operational pH window, sludge accumulation, inefficient H2O2 and efficiency decline. To overcome these constraints, in this study, we used a homogeneous Fe3+-Ce3+-H2O2 Fenton-like process to degrade catechol at different experimental conditions. At pH 7, almost 97% of 10 mM catechol can be destructed within 60 min while the degradation by Classical Fenton or Fe3+-H2O2 Fenton-like process only 36.2% and 23.7%. The resultant solution after the degradation contains only traces of cerium ions. The sludge created by the process was extensively characterized by FTIR and XPS spectroscopy to elucidate the fate of cerium ions. Electron spin resonance (ESR) data confirmed •OH as the major free radical in Fe3+-Ce3+-H2O2 process. Our Fenton-like process widens the optimal pH values to neutral condition.