Highly N2-Selective Activated Carbon-Supported Pt-In Catalysts for the Reduction of Nitrites in Water

Fabrication of a Disposable Amperometric Sensor for the Determination of Nitrite in Food

Silver nanoparticles (AgNPs) were synthesized through an environmentally friendly method with tea extract as a reduction agent. By immobilizing them on the surface of a low-cost pencil graphite electrode (PGE) with the aid of a simple and well-controlled in-situ electropolymerization method, a novel nanosensing interface for nitrite was constructed. The film-modified PGE showed good electrocatalytic effects on the oxidation of nitrite and was characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. Characterization results clearly show that the successful modification of AgNPs improved the surface area and conductivity of PGEs, which is beneficial to the high sensitivity and short response time of the nitrite sensor. Under the optimal detection conditions, the oxidation peak current of nitrite had a good linear relationship with its concentration in the range of 0.02-1160 μmol/L with a detection limit of 4 nmol/L and a response time of 2 s. Moreover, the sensor had high sensitivity, a wide linear range, a good anti-interference capability, and stability and reproducibility. Additionally, it can be used for the determination of nitrite in food.

Concentrate and degrade PFOA with a photo-regenerable composite of In-doped TNTs@AC

"Concentrate-and-degrade" is an effective strategy to promote mass transfer and degradation of pollutants in photocatalytic systems, yet suitable and cost-effective photocatalysts are required to practice the new concept. In this study, we doped a post-transition metal of Indium (In) on a novel composite adsorptive photocatalyst, activated carbon-supported titanate nanotubes (TNTs@AC), to effectively degrade perfluorooctanoic acid (PFOA). In/TNTs@AC exhibited both excellent PFOA adsorption (>99% in 30 min) and photodegradation (>99% in 4 h) under optimal conditions (25 °C, pH 7, 1 atm, 1 g/L catalyst, 0.1 mg/L PFOA, 254 nm). The heterojunction structure of the composite facilitated a cooperative adsorption mode of PFOA, i.e., binding of the carboxylic head group of PFOA to the metal oxide and attachment of the hydrophobic tail to AC. The resulting side-on adsorption mode facilitates the electron (e^‒) transfer from the carboxylic head to the photogenerated hole (h⁺), which was the major oxidant verified by scavenger tests. Furthermore, the presence of In enables direct electron transfer and facilitates the subsequent stepwise defluorination. Finally, In/TNTs@AC was amenable to repeated uses in four consecutive adsorption-photodegradation runs. The findings showed that adsorptive photocatalysts can be prepared by hybridization of carbon and photoactive semiconductors and the enabled "concentrate-and-degrade" strategy is promising for the removal and degradation of trace levels of PFOA from polluted waters.

Mussel-Inspired Magnetic Dissolving Pulp Fibers Toward the Adsorption and Degradation of Organic Dyes

In this work, a simple synthetic method was used to prepare a new type of magnetic dissolving pulp (MDP) @polydopamine (PDA) fibers. The hydroxyl groups of the fibers were converted into carboxyl groups after succinylation. Fe₃O₄ nanoparticles were grown in situ on the fibers. The prepared MDP@PDA fibers have catalytic reduction efficiency and adsorption performance for methylene blue organic dyes, and it has been thoroughly tested under various pH conditions. Fe₃O₄@PDA fibers have high reusability, are easy to separate, and regenerate quickly. The catalytic and adsorption efficiency barely decreases after repeated use. The surface of dissolving pulp fibers with a functionalized multifunctional PDA coating is used to create multifunctional catalysts and adsorbent materials. This study presents a very useful and convenient method for the synthesis and adjustment of MDP@PDA fibers, which have a wide range of potential applications in catalysis and wastewater treatment.