A nivalenol imprinted quartz crystal microbalance sensor based on sulphur-incorporating cobalt ferrite and its application to rice samples

Nivalenol as a mycotoxin pesticide is toxic to humans and animals and causes major health problems including hemorrhage, anemia, and vomiting. Thus, the need for fast and reliable analytical systems in terms of the management of health risks resulting from nivalenol exposure has increased in recent years. The aim of this study involved a novel molecularly imprinted quartz crystal microbalance sensor preparation based on sulphur-incorporating cobalt ferrite for nivalenol detection in rice samples. For this aim, cobalt ferrite and sulfur incorporated cobalt ferrite were successfully synthesized by sol-gel and calcination methods, respectively. Then, nivalenol imprinted quartz crystal microbalance chips based on cobalt ferrite and sulfur incorporated cobalt ferrite were prepared by an ultraviolet polymerization technique including N,N'-azobisisobutyronitrile as the initiator, ethylene glycol dimethacrylate as the cross-linker, methacryloylamidoglutamic acid as the monomer, and nivalenol as the analyte. After some spectroscopic, electrochemical and microscopic characterization studies, the developed sensor was applied to rice grain samples for the determination of nivalenol. The linearity of the prepared sensor was observed to be 1.0-10.0 ng L-1 and the limit of quantification and detection limit were found to be 1.0 and 0.33 ng L-1, respectively. Finally, the high selectivity, repeatability, and stability of the prepared sensor based on sulphur-incorporating cobalt ferrite and a molecularly imprinted polymer can ensure safe food consumption worldwide.

Effect of copper ions on transformation of organic sulfur in cationic exchange resins in Li2CO3-Na2CO3-K2CO3 molten-salt system

Cationic exchange resins (CERs) were applied for purification and clarifying process of radioactive wastewater in nuclear industry, which was a kind of sulfur-containing organic material. Molten-salt oxidation (MSO) method can be applied for the treatment of spent CERs and the absorption of acid gas (such as SO₂). The experiments about the molten salt destruction of the original resin and Cu ions doped resin were conducted. The transformation of organic sulfur in Cu ions doped resin was investigated. Compared with the original resin, the content of tail gas (such as CH₄, C₂H₄, H₂S and SO₂) released from the decomposition of Cu ions doped resin was relatively high at 323-657 °C. Sulfur elements in the form of sulfates and copper sulfides were fixed in spent salt through XRD analysis. The XPS result revealed that the portion of functional sulfonic acid groups (-SO₃H) in Cu ions doped resin was converted into sulfonyl bridges (-SO₂-) at 325 °C. With the enhancement of temperature, sulfonyl bridges (-SO₂-) were further decomposed to sulfoxides sulfur (-SO-) and organic sulfide sulfur. The destruction of thiophenic sulfur to H₂S and CH₄ was prompted by copper ions in copper sulfide. Sulfoxide were oxidized to the sulfone sulfur in molten salt. Sulfones sulfur consumed by reduction of Cu ions at 720 °C was more than it produced by oxidation of sulfoxide through XPS analysis, and the relative proportion of sulfone sulfur was 16.51%.

Applications of Heterogeneous Photocatalysis to the Degradation of Oxytetracycline in Water: A Review

Photocatalytic processes are being studied extensively as potential advanced wastewater treatments for the removal of pharmaceuticals, pesticides and other recalcitrant micropollutants from the effluents of conventional wastewater treatment plants (WWTPs). Oxytetracycline (OTC) is a widespread antibiotic which is frequently detected in surface water bodies as a recalcitrant and persistent micropollutant. This review provides an update on advances in heterogeneous photocatalysis for the degradation of OTC in water under UV light, sunlight and visible-light irradiation. Photocatalysts based on pure semiconducting oxides are rarely used, due to the problem of rapid recombination of electron–hole pairs. To overcome this issue, a good strategy could be the coupling of two different semiconducting compounds with different conduction and valence bands. Several methods are described to enhance the performances of catalysts, such as doping of the oxide with metal and/or non-metal elements, surface functionalization, composites and nano-heterojunction. Furthermore, a discussion on non-oxidic photocatalysts is briefly provided, focusing on the application of graphene-based nanocomposites for the effective treatment of OTC.

Cobalt ferrite-modified sol-gel synthesized ZnO nanoplatelets for fast and bearable visible light remediation of ciprofloxacin in water

Currently, metal oxide photocatalysts is a green and facile tool for the elimination of emerging pollutants utilizing light illumination. Though, the wide bandgap energy (E_g), rapid recombination of photogenerated carriers, and photostability of these oxides represent critical issues before the actual application. Herein, we familiarise a sol-gel based synthesis of ZnO hexagonal nanoplatelets modified with CoFe₂O₄ (CFO) nanoparticles at minor loading (1.0-4.0 wt %) to yield CFO/ZnO nanoheterojunctions. The CFO/ZnO unveiled mesostructured surfaces at surface areas of 102-120 m² g^-1 and photoactive in the visible region with high. The CFO addition to ZnO reduced its E_g from 3.14 to 2.66 eV. The formed nanoheterojunctions were applied to remediate ciprofloxacin (CPF), as an antibiotic pollutant in wastewater. The 2.4 g L^-1 3.0 wt % CFO-added ZnO exhibited a 100% removal of 10-ppm CPF within 45 min of visible-light irradiation and sustainable recycling ability for five consecutive runs at 97%. The sustainable performance of CFO/ZnO is ascribed to the suppression of photogenerated carriers and reduction of E by p-n nanoheterojunction formation. This study broadens the way for nanoheterojunction oxides for the destruction of pharmaceutical wastes under visible-light illumination.

Construction of magnetically recoverable ZnS-WO3-CoFe2O4 nanohybrid enriched photocatalyst for the degradation of MB dye under visible light irradiation

Easily recyclable photocatalysts have received considerable attention for their practical application, in order to address the wastewater treatments. Here, we report efficient and magnetically recyclable ZnS-WO₃-CoFe₂O₄ nanohybrid prepared through wet impregnation method. The photophysical and optical properties of as-prepared photocatalysts was investigated by different spectroscopic techniques. The photocatalytic activity of as synthesized samples were assessed by the photodegradation of methylene blue (MB) dye under visible light irradiation. Amongst, ZnS-WO₃-CoFe₂O₄ nanohybrid exhibit higher photodegradation activity than the other bare and hybrid samples. The enhanced light absorption and lower emission intensity provide the improved photocatalytic activity of ZnS-WO₃-CoFe₂O₄ nanohybrid. The ZnS-WO₃-CoFe₂O₄ nanohybrid exhibit excellent photostability after four consecutive cycles. The ferromagnetic behavior of the hybrid sample using easily recover from the dye solution using an external bar magnet.

CoFe2O4@HNTs/AuNPs Substrate for Rapid Magnetic Solid-Phase Extraction and Efficient SERS Detection of Complex Samples All-in-One

Fast and accurate practical sample detection is a great challenge in on-site detection. Herein, we developed a CoFe₂O₄@HNTs/AuNPs substrate for rapid and efficient magnetic solid-phase extraction (MSPE) surface-enhanced Raman scattering (SERS) detection of aromatic amines and nitrofuran in real samples all-in-one. Magnetic CoFe₂O₄ beads filled inside halloysite nanotubes (HNTs) can avoid aggregation of particles, endow the substrate with the rapid magnetic separation ability to simplify the pretreatment procedure, and reduce complex matrix interference. Meanwhile, outer surface AuNPs can generate electromagnetic enhancement and hot spots to amplify Raman signals of target molecules enriched/concentrated by HNTs. The CoFe₂O₄@HNTs/AuNPs substrate exhibited excellent SERS activity (high sensitivity, good reproducibility, and repeatability), pH stability (3.0-11.0), and good MSPE ability (fast magnetic enrichment/separation ability within 5 min). The CoFe₂O₄@HNTs/AuNPs MSPE SERS substrate can be applied for the determination of 4,4'-thioaniline and nitrofurantoin with a linear range of 0.054-21.7 mg/L and 0.05-1.0 mg/L, and the limits of detection were down to 0.026 mg/L and 0.014 mg/L, respectively. Furthermore, the enhancement factor (EF) of the substrate to 4,4'-thioaniline is up to 2.7 × 10⁷. Besides, the substrate can realize practical SERS determination of trace 4,4-thioaniline in cosmetics and nitrofurantoin in fish feed and aquatic samples. The recoveries were varied from 71.6% to 103.6% for 4,4-thioaniline in hair dyes and 81.9% to 116.3% for nitrofurantoin in fish feed and aquatic samples, respectively. Such a robust and efficient MSPE SERS substrate possesses great potential in rapid detection (within 15 min) for a practical sample, and it also provides a methodology for the preparation of other HNTs-based composites.

A Z-Scheme Polyimide/AgBr@Ag Aerogel with Excellent Photocatalytic Performance for the Degradation of Oxytetracycline

A novel Z-scheme polyimide (PI)/AgBr@Ag aerogel photocatalyst has been successfully synthesized by combining an in situ precipitation method and a supercritical drying method. The as-prepared PI/AgBr@Ag-50 (50 wt % AgBr@Ag in PI/AgBr@Ag) aerogel photocatalyst exhibited excellent photocatalytic activity for oxytetracycline degradation with a rate constant of 0.025 min^-1 , which was 6.9 and 2.6 times higher than that of the PI aerogel or the AgBr@Ag nanoparticles, respectively. More significantly, the PI/AgBr@Ag-50 aerogel photocatalyst showed stable cycling, which could be attributed to the high mechanical strength and 3D network of the PI aerogel. The introduction of AgBr@Ag on PI with a heterojunction structure efficiently promoted the separation of electron-hole pairs by a Z-scheme mechanism. The reduced metallic Ag nanoparticles were found to function as centers for the transfer of electrons from AgBr to PI. This work has revealed a new application for the aerogel PI/AgBr@Ag photocatalyst in environmental protection.