Fabrication of novel magnetic Mg0.8Cu0.2Fe2O4/SiO2/CeO2 nanocomposite synthesized by a simple ultrasonic-assisted route for organic dye removal using Fenton-like reaction.

Fenton-like degradation of contaminants is considered to be a feasible method for eliminating environmental pollution. In this study, a novel ternary Mg0.8Cu0.2Fe2O4/SiO2/CeO2 nanocomposite was fabricated using a novel ultrasonic-assisted technique, and investigated as a Fenton-like catalyst for the removal of tartrazine (TRZ) dye. The nanocomposite was synthesized by first coating the SiO2 shell around the Mg0.8Cu0.2Fe2O4 core via a Stöber-like process to form Mg0.8Cu0.2Fe2O4/SiO2. Then, a simple ultrasonic-assisted route was used to synthesize Mg0.8Cu0.2Fe2O4/SiO2/CeO2 nanocomposite. This approach provides a simple and environmentally friendly way to produce this material without the use of any additional reductants or organic surfactants. The fabricated sample demonstrated excellent Fenton-like activity. The efficiency of Mg0.8Cu0.2Fe2O4 was significantly enhanced by the incorporation of SiO2 and CeO2, and complete removal of TRZ (30 mg/L) was achieved within 120 min using 0.2 g/L of Mg0.8Cu0.2Fe2O4/SiO2/CeO2. The scavenger test shows that the main active species is the strong oxidizing of hydroxyl radicals (HO•). Consequently, the Fenton-like mechanism of Mg0.8Cu0.2Fe2O4/SiO2/CeO2 is explained based on the coexistence of Fe3+/Fe2+, Cu2+/Cu+, and Ce4+/Ce3+ redox couples. The removal efficiency of TRZ dye remained around 85% after the third recycling run, revealing that the nanocomposite could be employed to eliminate organic contaminants in water treatment. This research opened up a new avenue for expanding the practical application of new-generation Fenton-like catalysts.

Electrochemical sensor based on a ZnO-doped graphitized carbon for the electrocatalytic detection of the antibiotic hydroxychloroquine. Application: tap water and human urine.

Abstract: In December 2019, the world experienced a new coronavirus, SARS-CoV-2, causing coronavirus disease 2019 originating from Wuhan.The virus has crossed national borders and now affects more than 200 countries and territories. Hydroxychloroquine has been considered as a drug capable of treating COVID-19. The objective of this work is to establish a simple platform for electrocatalytic detection of hydroxychloroquine in human urine samples and pharmaceutical samples (tablets) using a ZnO@CPE sensor constructed by simple and inexpensive hydrothermal methods using a square wave voltammetry method. The best results are obtained in a PBS electrolyte with irreversible behavior of the hydroxychloroquine complement and controlled by diffusion coupled with absorption phenomena. The ZnO@CPE shifts the oxidation potential of hydroxychloroquine with the formation of a single very intense peak at the position of Epa = 0.5 V/(vs Ag/AgCl) with a shift is ΔEp = 0.1 V(vs Ag/AgCl) compared to the unmodified electrode. The obtained ZnO@CPE hybrid nanocomposite was characterized by different techniques and showed excellent electrocatalytic activity and higher active surface area compared to the bare carbon paste electrode. Under the optimized experimental conditions, the ZnO@CPE sensor showed good analytical performance for the determination of trace amounts of hydroxychloroquine, a wide linearity range from 10-3 M to 0.8 × 10-6 M with a very low detection limit in the range of 1.33 × 10-7 M, satisfactory selectivity, acceptable repeatability and reproducibility. The calculated recovery and coefficient of variation for the two samples analyzed are very satisfactory, ranging from 97.6 to 102% and 1.2 to 2.3% respectively. The proposed applied method and the fabricated sensor offer the possibility to analyze traces of hydroxychloroquine in real human urine and water samples. Graphical abstract: Strategy for the electro-oxidation reaction of hydroxychloroquine on the electro-catalytic surface of the ZnO@Carbon graphite electrode and real-time detection of hydroxychloroquine.

The solvent-free mechano-chemical grinding of a bifunctional P25-graphene oxide adsorbent-photocatalyst and its configuration as porous beads.

Owing to their use in water-cleaning technology, titanium-dioxide-based nanomaterials have dominated the photocatalysis scene, with so-called Degussa (P25) being the most promising under UV light. However, this is not the case under visible light, where it is necessary to combine titanium dioxide with other photosensitising nanomaterials. Unfortunately, most of the strategies aimed in this direction are chemically non-facile, energy-intensive, economically expensive, and not suitable for large-scale production. We herein describe a straightforward solvent-free approach for accessing visible-light-activated titanium-dioxide-based photocatalysts via the mechanochemical grinding of Degussa P25 with a second solid partner. Upon comparing several solid-material benchmarks, P25-graphene oxide is the best combination. The resulting material showed efficient performance for the adsorption and photodegradation of different dye pollutants, namely methylene blue, malachite green, Congo red, and methyl orange. The recorded performance was nearly comparable to that reached using sol-gel materials, with the ultimate advantage of being more sustainable and industrially scalable. The recyclability can be improved through a porous-bead configuration using biomass waste chitosan hydrogel, an approach that can further fulfill the requirement for more sustainable photocatalyst designs.

Adsorption of disperse blue SBL dye by synthesized poorly crystalline hydroxyapatite.

The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO3)2 and (NH4)2HPO4 reagents in aqueous solution at room temperature. The adsorption experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent dosage, initial dye concentration, solution temperature, and pH. The experimental results show that the percentage of dye removal increases with increasing the amount of adsorbent, until the total discoloration. The adsorption isotherms follow the model of Langmuir with a high adsorption capacity. The adsorption was pH and temperature dependent.

Photocatalytic degradation and adsorption of 2-naphthol on suspended TiO2 surface in a dynamic reactor.

The photocatalytic oxidation of 2-naphthol has been investigated at room temperature in a dynamic photoreactor with system UV/O2 (air) and aqueous suspension of titanium dioxide TiO2 irradiated under a variety of conditions. The kinetics of disappearance of pollutant were affected by several operating parameters such as TiO2 mass, concentration of the substrate and reaction pH. The experiments were measured by high performance liquid chromatography. A Langmuir-Hinshelwood model was found to be accurate for photocatalytic degradation and indicates that adsorption of the solute on the surface of semiconductor particles plays a role in photocatalytic reaction.