A magnetic-void-porous MnFe2O4/carbon microspheres nano-catalyst for catalytic ozonation: Preparation, performance and mechanism

Preparation of Cu/Cu2O/BC and Its Performance in Adsorption-Photocatalytic Degradation of Methyl Orange in Water

In this study, we prepared a low-cost novel Cu/Cu2O/BC nanocomposite visible-light photocatalyst by the impregnation method using CuSO4·5H2O and rice husk biochar (BC) as raw materials and Na2S2O4 as a single reductant to improve the stability and dispersion of the Cu/Cu2O nanoparticles, in order to solve their aggregation tendency during photocatalysis. The morphology and structure of the Cu/Cu2O/BC were characterized using various analytical and spectroscopic techniques. The photocatalytic effect and cyclic stability of the synthesized photocatalyst on methyl orange (MO) removal were investigated under visible light radiation and various parameter conditions, including the mass ratio of BC to Cu/Cu2O, initial MO concentration, pH, temperature, and catalyst dosage. The results show that the synthesized Cu/Cu2O/BC nanocomposite composed of Cu/Cu2O spherical particles was loaded on the BC carrier, which has better stability and dispersion. The best adsorption-photocatalytic effect of the Cu/Cu2O/BC is exhibited when the mass ratio of BC to Cu/Cu2O is 0.2. A total of 100 mg of Cu/Cu2O/BC can remove 95% of the MO and 88.26% of the COD in the aqueous solution at pH = 6, T = 25 °C, and an initial MO concentration of 100 mg/L. After five cycles of degradation, the MO degradation rate in the sample can still remain at 78.41%. Both the quasi-secondary kinetic model and the Langmuir isothermal adsorption model describe the adsorption process. Additionally, the thermodynamic analysis demonstrates that the photocatalytic process follows the quasi-primary kinetic model and that the removal process is of spontaneous heat absorption. The photocatalyst described in this paper offers a cost-effective, easily prepared, and visible-light-responsive solution for water pollution treatment.

Highly efficient reduction of bromate by vacuum UV/sulfite system

Bromate (BrO3-), a worldwide regulated by-product after ozone disinfection, is often detected in bromide-containing water, and has a strict limit of 10 μg L-1 in potable water. BrO3- degradation by advanced reduction processes (ARPs) has gained much attention because of efficient removal and easy integration with ultraviolet disinfection (UV at 254 nm). In the vacuum UV (VUV, 185/254 nm)/sulfite system, the elimination kinetics of BrO3- increased by 9-fold and 15-fold comparing with VUV alone and UV/sulfite system. This study further demonstrated the hydrated electron (eaq-) works as the dominant species in BrO3- degradation in alkaline solution, while in the acidic solution the H• became a secondary reactive species besides eaq-. Hence, the influences of pH, sulfite concentration, dissolved gas and water matrix on effectiveness of degradation kinetics of BrO3- was explored in details. With increasing pH, the proportion of SO32- species increased and even became the major ones, which also correlated well with the kobs (min-1) of BrO3- degradation. The stability of eaq- also climbs with increasing pH, while that of H• drops significantly. Higher sulfite dosage favored a more rapid degradation of BrO3-. The presence of dissolved oxygen inhibited BrO3- removal due to the scavenging effect of O2 toward eaq- and transformed VUV/sulfite-based ARP to an advanced oxidation process (AOP), which was ineffective for BrO3- removal. BrO3- removal was inhibited to varying degrees after anions (e.g., bicarbonate (HCO3-), chloride (Cl-), nitrate (NO3-)) and humic acid (HA) being added.

Greening the economy: how culture values shape environmental policies in America and Europe

This research explores the theory that cultural factors shape how people feel about the environment. Both theoretical and empirical approaches are used in our investigation of this problem. In the theoretical part of the study, we provide a model for transferring cultural practices from one generation to the next. To provide empirical evidence for the existence of this cultural factor in environmental views, we analyze survey data from the European Values Research. Using a comparative method, we use differences caused by migration patterns in Europe and America. According to our research, cultural influences on migrants' ecological beliefs are long-lasting and statistically significant. Variations in migrants' environmental views may be traced back to societal norms that endure in their home countries. We also demonstrate that ecological views are robust in the face of incentives originating from the external environment, demonstrating that migrants' choices in the host nation are not much influenced by the environmental circumstances they were exposed to in their home countries. We uncover fascinating variations in the cultural transfer procedure, and our results hold up under various hypotheses. These findings suggest that, in light of the prevalence of ecological problems requiring community action, it is crucial to formulate policies that consider the factors that led to the development of ecological cultures.

A thorough observation of an ozonation catalyst under long-term practical operation: Deactivation mechanism and regeneration

Heterogeneous catalytic oxidation, as an efficient advanced treatment technology, has been gradually applied in industrial wastewater treatment. The fixed bed technique is one of the most popular catalytic ozonation methods. However, few studies have concentrated on the long-term operation effects on catalysts. In this study, we conducted long-term (~5 years) observations of the operation of the largest petrochemical wastewater treatment plant (treatment capacity 120,000 m³/d) with catalytic ozonation technology in China. A commercial catalyst, which uses Al₂O₃ pellets supporting copper oxide was applied in this plant. The results showed that the catalytic efficiency gradually decreased from 60.65% to 25.98% since 2018, and the ozone dosage to COD removal ratio (ozone/COD) also increased from 0.82 to 1.93 mg/mg as the running time continued. By means of the comparison and characterization of fresh catalyst and used catalyst, a "mucus layer" was formed by the adsorption of negatively charged extracellular polymeric substances on the positively charged catalyst surface and the interception of the catalyst layer. The mucus layer significantly reduced the catalytic efficiency by isolating ozone with catalytic active sites and releasing extra organic contaminants during the catalytic process resulting in 53.97% TOC increase in the batch test. Meanwhile, regeneration experiments revealed that the TOC removal efficiency was 4.76% and 43.48% in presence of washed catalysts and calcinated catalysts, respectively. Compared with the fresh catalyst, 73% of the catalytic activity was recovered for calcinated catalyst. Consequently, this study provides much practical information, showing positive effects on the promotion of catalytic ozonation application in actual wastewater treatment.

A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety

The synthetic dyes used in the textile industry pollute a large amount of water. Textile dyes do not bind tightly to the fabric and are discharged as effluent into the aquatic environment. As a result, the continuous discharge of wastewater from a large number of textile industries without prior treatment has significant negative consequences on the environment and human health. Textile dyes contaminate aquatic habitats and have the potential to be toxic to aquatic organisms, which may enter the food chain. This review will discuss the effects of textile dyes on water bodies, aquatic flora, and human health. Textile dyes degrade the esthetic quality of bodies of water by increasing biochemical and chemical oxygen demand, impairing photosynthesis, inhibiting plant growth, entering the food chain, providing recalcitrance and bioaccumulation, and potentially promoting toxicity, mutagenicity, and carcinogenicity. Therefore, dye-containing wastewater should be effectively treated using eco-friendly technologies to avoid negative effects on the environment, human health, and natural water resources. This review compares the most recent technologies which are commonly used to remove dye from textile wastewater, with a focus on the advantages and drawbacks of these various approaches. This review is expected to spark great interest among the research community who wish to combat the widespread risk of toxic organic pollutants generated by the textile industries.

Carbamazepine degradation by visible-light-driven photocatalyst Ag3PO4/GO: Mechanism and pathway

Carbamazepine (CBZ), as one of the most frequently detected pharmaceuticals, is of great concern due to its potential impact on the ecosystem and human health. This study provides an effective approach to remove CBZ by using photocatalyst silver phosphate combined with graphene oxide (Ag3PO4/GO) under visible irradiation. The morphology, composition, and optical properties of Ag3PO4/GO were characterized employing SEM, XRD, and DRS. Graphene oxide could improve the visible-light utilization and promote electron's charge to enhance the photocatalytic performance of Ag3PO4/GO. With the optimal reaction condition of 5.86 mW/cm2 light intensity, 15-25 °C temperature, 5-7 pH, and 0.5 mg/L catalytic dosages, 5 mg/L CBZ could be completely degraded in 30 min, and the apparent rate constant could reach 0.12 min-1. Additionally, the radical trapping experiments indicated •OH and O2-• were the main reactive oxygen species employed to eliminate CBZ. The decay pathways of CBZ had been proposed accordingly, and the main product was the low-molecular products.

Wood-feeding termite gut symbionts as an obscure yet promising source of novel manganese peroxidase-producing oleaginous yeasts intended for azo dye decolorization and biodiesel production

BACKGROUND

The ability of oxidative enzyme-producing micro-organisms to efficiently valorize organic pollutants is critical in this context. Yeasts are promising enzyme producers with potential applications in waste management, while lipid accumulation offers significant bioenergy production opportunities. The aim of this study was to explore manganese peroxidase-producing oleaginous yeasts inhabiting the guts of wood-feeding termites for azo dye decolorization, tolerating lignocellulose degradation inhibitors, and biodiesel production.

RESULTS

Out of 38 yeast isolates screened from wood-feeding termite gut symbionts, nine isolates exhibited high levels of extracellular manganese peroxidase (MnP) activity ranged between 23 and 27 U/mL after 5 days of incubation in an optimal substrate. Of these MnP-producing yeasts, four strains had lipid accumulation greater than 20% (oleaginous nature), with Meyerozyma caribbica SSA1654 having the highest lipid content (47.25%, w/w). In terms of tolerance to lignocellulose degradation inhibitors, the four MnP-producing oleaginous yeast strains could grow in the presence of furfural, 5-hydroxymethyl furfural, acetic acid, vanillin, and formic acid in the tested range. M. caribbica SSA1654 showed the highest tolerance to furfural (1.0 g/L), 5-hydroxymethyl furfural (2.5 g/L) and vanillin (2.0 g/L). Furthermore, M. caribbica SSA1654 could grow in the presence of 2.5 g/L acetic acid but grew moderately. Furfural and formic acid had a significant inhibitory effect on lipid accumulation by M. caribbica SSA1654, compared to the other lignocellulose degradation inhibitors tested. On the other hand, a new MnP-producing oleaginous yeast consortium designated as NYC-1 was constructed. This consortium demonstrated effective decolorization of all individual azo dyes tested within 24 h, up to a dye concentration of 250 mg/L. The NYC-1 consortium's decolorization performance against Acid Orange 7 (AO7) was investigated under the influence of several parameters, such as temperature, pH, salt concentration, and co-substrates (e.g., carbon, nitrogen, or agricultural wastes). The main physicochemical properties of biodiesel produced by AO7-degraded NYC-1 consortium were estimated and the results were compared to those obtained from international standards.

CONCLUSION

The findings of this study open up a new avenue for using peroxidase-producing oleaginous yeasts inhabiting wood-feeding termite gut symbionts, which hold great promise for the remediation of recalcitrant azo dye wastewater and lignocellulosic biomass for biofuel production.