The performance and pathway of indole degradation by ionizing radiation

Selective oxidation of nitrogenous heterocyclic compounds by heat/peroxymonosulfate in phenol-rich wastewater

In phenol-rich wastewater, such as coking wastewater, due to the high reactivity of phenol to various reactive oxygen species, it is difficult to selectively oxidize pollutants having lower biodegradability and higher toxicity than phenol. As one kind of such pollutants in coking wastewater, some nitrogenous heterocyclic compounds (NHCs) are more difficult to be removed by SO4•- or HO• than phenol, but this study found that NHCs (quinoline, isoquinoline, and pyridine) can be selectively removed by peroxymonosulfate (PMS) direct oxidation in the presence of 10 mM phenol under thermal condition. The selective oxidation of NHCs needs a suitable pH range (4 < constant pH < 9) because protonated state of NHCs (pH < 4) is unfavorable to their oxidation and high pH would improve the extra PMS consumption by phenol. Under the conditions benefiting the removal of NHCs in heat/PMS system, there was no generation of SO4•- and HO•. Being treated by 60 °C/PMS for 60 min, the biodegradability (BOD5/COD) of real coking wastewater (RCW) was improved from 0.21 to 0.44 with low removal rate of phenols (about 10 %). Quinoline and indole, as the two typical NHCs in the studied RCW, their removal rates can be up to 45 % and 85 %, respectively. Thus, heat/PMS pretreatment is a potential good way to selectively remove high toxic pollutants in phenol-rich wastewater.

Synthesis of MnFe2O4/activated carbon derived from durian shell waste for removal of indole in water: Optimization, modelling, and mechanism

While durian shell is often discharged into landfills, this waste can be a potential and zero-cost raw material to synthesize carbon-based adsorbents with purposes of saving costs and minimizing environmental contamination. Indole (IDO) is one of serious organic pollutants that influence aquatic species and human health; hence, the necessity for IDO removal is worth considering. Here, we synthesized a magnetic composite, denoted as MFOAC, based on activated carbon (AC) derived from durian shell waste incorporated with MnFe2O4 (MFO) to adsorb IDO in water. MFOAC showed a microporous structure, along with a high surface area and pore volume, at 518.9 m2/g, and 0.106 cm3/g, respectively. Optimization of factors affecting the IDO removal of MFOAC were implemented by Box-Behnken design and response surface methodology. Adsorption kinetics and isotherms suggested a suitable model for MFOAC to remove IDO. MFOAC was recyclable with 3 cycles. Main interactions involving in the IDO adsorption mechanism onto MFOAC were clarified, including pore filling, n-π interaction, π-π interaction, Yoshida H-bonding, H-bonding.

Investigation into the characteristics of electron beam-aged microplastics and adsorption behavior of dibutyl phthalate

Microplastics are increasingly prevalent in the environment, and their ability to adsorb various organic additives, posing harm to organisms, has attracted growing attention. Currently, there are no effective methods to age microplastics, and there is limited discussion on the subsequent treatment of aged microplastics. This study focuses on micro polyethylene (PE) and employs electron beam technology for aging treatment, investigating the adsorption and leaching behavior between PE and dibutyl phthalate (DBP) before and after aging. Experimental results indicate that with increasing doses of electron beam irradiation, the surface microstructure of PE worsens, inducing the generation of oxygen-containing functional groups on the surface of polyethylene. Comparative evaluations between electron beam aging and existing methods show that electron beam technology surpasses existing aging methods, achieving a level of aging exceeding 0.7 within an extremely short period of 1 min at doses exceeding 350 kGy. Adsorption experiments demonstrate that the adsorption between PE and DBP conforms to pseudo-second-order kinetics and the Freundlich model both before and after aging. The adsorption capacity of microplastics for DBP increases from 76.8 mg g-1 to 167.0 mg g-1 after treatment, exceeding that of conventional DBP adsorbents. Electron beam irradiation causes aging of microplastics mainly through the generation of ·OH, which lead to the formation of oxygen-containing functional groups on the microplastics' surface, thereby enhancing their adsorption capacity for DBP. This provides a new perspective for the degradation of aged microplastics and composite pollutants.

Decolorization and degradation of various dyes and dye-containing wastewater treatment by electron beam radiation technology: An overview

The treatment of dye-containing wastewater generated from textile industries is still a challenge, and various technologies, including physical, chemical and biological ones have been used. In recent years, the ionizing radiation (usually including gamma ray generated by radionuclide, such as 60Co and 137Cs, and electron beam generated by electron accelerator) technology has received increasing attention for degrading refractory or toxic organic pollutants in wastewater because of its unique advantages, such as no chemical additives, fast reaction rate, strong degradation capacity, high efficiency, flexibility, controllability. Compared to the conventional wastewater treatment processes, ionizing radiation technology, as a disruptive wastewater treatment technology, is more efficient for the decolorization and degradation of dyes and the treatment of dye-containing wastewater. In this paper, the recent advances in the treatment of dye-containing wastewater by ionizing radiation, in particular by electron beam (EB) radiation were summarized and analyzed, focusing on the decolorization and degradation of various dyes. Firstly, the formation of various reactive species induced by radiation and their interactions with dye molecules, as well as the influencing factors on the removal efficiency of dyes were discussed. Secondly, the researches on the treating dye-containing wastewater by electron beam radiation technology were systematically reviewed. Then, the decolorization and degradation mechanisms by electron beam radiation were further discussed in detail. And the integrated processes that would contribute to the advancement of this technology in practical applications were examined. More importantly, the recent advances of electron beam radiation technology from laboratory to application were reviewed, especially successful operation of dye-containing wastewater treatment facilities in China. And eventually, current challenges, future research directions, and outlooks of electron beam radiation technology were proposed for further advancing this technology for the sustainable development of water resources.

Nano-remediation technologies for the sustainable mitigation of persistent organic pollutants

The absence of novel and efficient methods for the elimination of persistent organic pollutants (POPs) from the environment is a serious concern in the society. The pollutants release into the atmosphere by means of industrialization and urbanization is a massive global hazard. Although, the eco-toxicity associated with nanotechnology is still being debated, nano-remediation is a potentially developing tool for dealing with contamination of the environment, particularly POPs. Nano-remediation is a novel strategy to the safe and long-term removal of POPs. This detailed review article presents an important perspective on latest innovations and future views of nano-remediation methods used for environmental decontamination, like nano-photocatalysis and nanosensing. Different kinds of nanomaterials including nanoscale zero-valent iron (nZVI), carbon nanotubes (CNTs), magnetic and metallic nanoparticles, silica (SiO₂) nanoparticles, graphene oxide, covalent organic frameworks (COFs), and metal organic frameworks (MOFs) have been summarized for the mitigation of POPs. Furthermore, the long-term viability of nano-remediation strategies for dealing with legacy contamination was considered, with a particular emphasis on environmental and health implications. The assessment goes on to discuss the environmental consequences of nanotechnology and offers consensual recommendations on how to employ nanotechnology for a greater present and a more prosperous future.

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.