A versatile CeO2/Co3O4 coated mesh for food wastewater treatment: Simultaneous oil removal and UV catalysis of food additives

Interface reconstruction of MXene-Ti3C2 doped CeO2 nanorods for remarked photocatalytic ammonia synthesis

Prospective photocatalytic ammonia synthesis process has received more attentions but quite challenging with the low visible light utilization and weak N2 molecule absorption ability around the photocatalysts. Herein, interface reconstruction of MXene-Ti3C2/CeO2 composites with high-concentration active sites through the carbon-doped process are presented firstly, and obvious transition zones with the three-phase reaction interface are formed in the as-prepared catalysts. The optimal co-doped sample demonstrates an excellent photo response in the visible light region, the strongest chemisorption activity and the most active sites. Moreover, much more in-situ extra oxygen defects are also produced under light irradiation. It is expected that the double decorated catalyst shows a remarked ammonia production rate of above 0.76 mmol gcal-1·h-1 under visible-light illumination and a higher apparent quantum efficiency of 1.08 % at 420 nm, which is one of the most completive properties for the photocatalytic N2 fixation at present.

Nanozyme-assisted molecularly imprinted polymer-based indirect competitive ELISA for the detection of marine biotoxin

Saxitoxin (STX), which is produced by certain dinoflagellate species, is a type of paralytic shellfish poisoning toxin that poses a serious threat to human health and the environment. Therefore, developing a technology for the convenient and cost-effective detection of STX is imperative. In this study, we developed an affinity peptide-imprinted polymer-based indirect competitive ELISA (ic-ELISA) without using enzyme-toxin conjugates. AuNP/Co3O4@Mg/Al cLDH was synthesized by calcining AuNP/ZIF-67@Mg/Al LDH, which was obtained by combining AuNPs, ZIF-67, and flower-like Mg/Al LDH. This synthesized nanozyme exhibited high catalytic activity (Km = 0.24 mM for TMB and 132.5 mM for H2O2). The affinity peptide-imprinted polymer (MIP) was imprinted with an STX-specific template peptide (STX MIP) on a multi-well microplate and then reacted with an STX-specific signal peptide (STX SP). The interaction between the STX SP and MIP was detected using a streptavidin-coated nanozyme (SA-AuNP/Co3O4@Mg/Al cLDH). The developed MIP-based ic-ELISA exhibited excellent selectivity and sensitivity, with a limit of detection of 3.17 ng/mL (equivalent: 0.317 μg/g). Furthermore, the system was validated using a commercial ELISA kit and mussel tissue samples, and it demonstrated a high STX recovery with a low coefficient of variation. These results imply that the developed ic-ELISA can be used to detect STX in real samples.

Pioneering superior efficiency in Methylene blue and Rhodamine b dye degradation under solar light irradiation using CeO2/Co3O4/g-C3N4 ternary photocatalysts

In this research work, we have successfully synthesized the CeO2/Co3O4/g-C3N4 ternary nanocomposite for hydrothermal method for photocatalytic applications. The synthesized nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy TEM, Photoluminescent spectra (PL), X-ray photoelectron spectroscopy (XPS), Brunauer- Emmett-Teller (BET) and Ultraviolet diffuse reflectance spectroscopy (UV-DRS) technique. As per the optical spectroscopic investigations CeO2/Co3O4/g-C3N4 ternary nanocomposite exhibited the high optical absorption range and its band gap is reduced from 2.95 eV to1.83 eV. The PL spectra showed the lowered emission peak intensity of ternary nanocomposite which is revealed that the better charge separation and slow recombination of electron hole pairs. The highest photocatalytic degradation efficiency of CeO2/Co3O4/g-C3N4 ternary nanocomposite showed 93 % and 86 % towards the pollutant methylene blue and Rhodamine B. Moreover, photodegradation of the pollutants followed pseudo-first order kinetics with a very high-rate constant of 0.02211 min-1 and 0.017756 min-1. Additionally, the ternary nano catalyst was delivered the remarkable stability performance even after five cycles. This research may provide a low-cost approach for synthesized visible light responsive catalysts for use in environmental remediation applications.

Modulating band structure through introducing Cu0/CuxO composites for the improved visible light driven ammonia synthesis

The photocatalytic performance of ceria-based materials can be tuned by adjusting the surface structures with decorating the transition-metal, which are considered as the important active sites. Herein, cuprous oxide-metallic copper composite-doped ceria nanorods were assembled through a simple hydrothermal reduction method. The photocatalytic ammonia synthesis rates exhibit an inverted "V-shaped" trend with increasing Cu0/CuxO mole ratio. The best ammonia production rate, approximately 900 or 521 µmol·gcal-1·h-1 under full-spectra or visible light, can be achieved when the Cu0/CuxO ratio is approximately 0.16, and this value is 8 times greater than that of the original sample. The absorption edge of the as-prepared samples shifted towards visible wavelengths, and they also had appropriate ammonia synthesis levels. This research provides a strategy for designing noble metal-free photocatalysts through introducing the metal/metallic oxide compositesto the catalysts.

CeO2-CDs clusters decorated Co(OH)2 nanosheets for improved photocatalytic ammonia synthesis

The green synthesis process of photocatalytic ammonia production has received more and more attentions. Herein, a Z-scheme heterojunction with all-solid-state structures is constructed, in which carbon dots can act as electron transferring mediators. The photocatalytic measurement shows that the modified photocatalysts exhibit much higher activities, in which the ammonia production rates can reach above 232 µmol·g_cal^-1·h^-1 under the light irradiation. The improved catalytic properties can be credited to the significantly increased number of photoinduced oxygen vacancies, the excellent visible-light adsorption abilities and photogenerated electron-hole separation efficiencies for the carbon dots bridged heterostructures. More hydroxyl and superoxide radicals can be simultaneously produced in the composites. This work provides reasonable guidance for applications in photocatalytic ammonia synthesis and a promising construction strategy of efficient Z-scheme photocatalysts.

A novel g-C3N4/g-C3N4-x homojunction with efficient interfacial charge transfer for photocatalytic degradation of atrazine and tetracycline

The abuse of pesticides and antibiotics and their harm to the environment are the disadvantages of modern agriculture and breeding industry. g-C₃N₄ has shown great potential in photocatalytic water pollution purification under visible light irradiation, however, the conventional g-C₃N₄ suffers from the disadvantage of limited optical absorption and serious charge recombination, resulting in inefficient light energy conversion and pollutant degradation. This study provides a strategy of combining defect engineering with a built-in electric field to prepare homojunction a photocatalyst with high optical absorption rate and charge separation efficiency. Experiments and DFT simulation revealed the mechanism of significant improvement in the photocatalytic performance of the prepared catalyst, and proposed the pollutant degradation pathway. In addition, the photocatalytic effects of the prepared catalysts on different natural water bodies, natural light, and various water conditions were investigated, revealing the applicability of the catalysts in the purification of pollutants in various water environments.

Wastewater in the food industry: Treatment technologies and reuse potential

Water is the most extensively used raw material in the food and beverage industry. This industrial sector has a negative impact on the environment and economy as a result of rising water demand and wastewater production. With the increasing scarcity of drinking water, the reuse of wastewater streams has become an important economic and ecological concern. Therefore, the optimisation of water consumption and wastewater reuse in the food industry is essential. On the other hand, several countries limit the reuse of wastewater because of legal curtailment, public health and safety concerns. This represents a major challenge for both industries and administrations due to the technical complexity and financial costs involved. The present review aims at addressing the key issues related to water consumption, wastewater generation, treatment and successful implementation cases of water reuse in the food and beverage industry. Moreover, the various case studies of already employed technologies for the food industry wastewater treatment and reuse have been analysed for their performance. Also, this review reveals future research on the application of other innovative technologies such as ultraviolet irradiation and micro electrolysis. However, the successful implementation of reuse strategies is associated with the holistic evaluation of local factors such as governmental incentives, social acceptance and legislation harmonisation related to the cost, risks, and environmental performance.

Prussian blue modified CeO2 as a heterogeneous photo-Fenton-like catalyst for degradation of norfloxacin in water

The heterogeneous photo-Fenton-like process is emerging as a promising treatment of antibiotics-containing wastewater. The preparation of new efficient and stable catalysts is one of the research fields. A composite catalyst, prussian blue (PB) modified CeO₂ was prepared, characterized, and applied for photo-Fenton oxidation of norfloxacin (NOR) in this study. It was found that chemical doping of PB leaded to more oxygen vacancies and increased the surface area of CeO₂ obviously. PB/CeO₂ with more Ce³⁺ facilitated electron transfer between Fe³⁺/Fe²⁺ with Ce³⁺/Ce⁴⁺. PB could also improve the separation rate of photoexcited electron-hole pairs in CeO₂ nanostructures. When the doping ratio of PB and CeO₂ was 10%, PB/CeO₂ show the highest catalytic degradation ability and 88.93% of NOR could be degraded within 30 min. PB/CeO₂ composite showed well reactivity at the wide pH value range of 3-8. The reusable experiments and low iron dissolution with less than 1 mg/L indicated that PB/CeO₂ could be employed as an efficient heterogeneous photo-Fenton-like catalyst in organic contaminants degradation.

Oxygen vacancy engineering of cerium oxide for the selective photocatalytic oxidation of aromatic pollutants

The engineering of oxygen vacancies in CeO₂ nanoparticles (NPs) allows the specific fine-tuning of their oxidation power, and this can be used to rationally control their activity and selectivity in the photocatalytic oxidation (PCO) of aromatic pollutants. In the current study, a facile strategy for generating exceptionally stable oxygen vacancies in CeO₂ NPs through simple acid (CeO₂-A) or base (CeO₂-B) treatment was developed. The selective (or mild) PCO activities of CeO₂-A and CeO₂-B in the degradation of a variety of aromatic substrates in water were successfully demonstrated. CeO₂-B has more oxygen vacancies and exhibits superior photocatalytic performance compared to CeO₂-A. Control of oxygen vacancies in CeO₂ facilitates the adsorption and reduction of dissolved O₂ due to their high oxygen-storage ability. The oxygen vacancies in CeO₂-B as active sites for oxygen-mediated reactions act as (i) adsorption and reduction reaction sites for dissolved O₂, and (ii) photogenerated electron scavenging sites that promote the formation of H₂O₂ by multi-electron transfer. The oxygen vacancies in CeO₂-B are particularly stable and can be used repeatedly over 30 h without losing activity. The selective PCOs of organic substrates were studied systematically, revealing that the operating mechanisms for UV-illuminated CeO₂-B are very different from those for conventional TiO₂ photocatalysts. Thus, the present study provides new insights into the design of defect-engineered metal oxides for the development of novel photocatalysts.

Self-Locked and Self-Cleaning Membranes for Efficient Removal of Insoluble and Soluble Organic Pollutants from Water

A feasible and efficient membrane for long-term treatment of complex oily wastewater is especially in demand, but its development still remains a challenge because of serious membrane fouling and incomplete/destructive reclamation methods. Herein, an interpenetrating TiO₂ nanorod-decorated membrane with self-locked and self-cleaning properties is rationally fabricated via coaxial electrospinning and hydrothermal synthesis. The self-locked membrane shows full reinstatement of the original state and exhibits satisfactory mechanical strength, superhydrophilicity, underwater superoleophobicity, and robust solvent resistance, which endow the membrane with successful separation for 16 types of highly emulsified oil-in-water emulsions (e.g., surfactant-free; anionic, cationic, and nonionic surfactant-stabilized). Moreover, successful sequencing treatment of soluble organic emulsions using the separated "bait-hook-destroy" strategy indicates that the pristine membrane can be used to treat multipollutant wastewater with various limits. Most importantly, the fouled membrane can easily be reinstated by light irradiation without reduction of both mechanical strength and separation performance. As a proof of concept, the as-synthesized membrane shows an ultrahigh flux over 5000 L m^-2 h^-1 with a removal efficiency of >99.92%. The present development would provide a highly efficient strategy for the fabrication of an inorganic-organic revivable electrospinning membrane for various applications.

Application of Various Metal-Organic Frameworks (MOFs) as Catalysts for Air and Water Pollution Environmental Remediation

The use of metal-organic frameworks (MOFs) to solve problems, like environmental pollution, disease, and toxicity, has received more attention and led to the rapid development of nanotechnology. In this review, we discuss the basis of the metal-organic framework as well as its application by suggesting an alternative of the present problem as catalysts. In the case of filtration, we have developed a method for preparing the membrane by electrospinning while using an eco-friendly polymer. The MOFs were usable in the environmental part of catalytic activity and may provide a great material as a catalyst to other areas in the near future.