Ag2O/TiO2 nanostructures for the photocatalytic mineralization of the highly recalcitrant pollutant iopromide in pure and tap water

Green synthesis of ZnO-TiO2/RGO nanocomposites using Senna surattensis extract: a novel approach for enhanced anticancer efficacy and biocompatibility

The purpose of the present study is to enhance the anticancer and biocompatibility performance of TiO2 NPs, ZnO NPs, ZnO-TiO2 (NCs), and ZnO-TiO2/reduced graphene oxide (RGO) NCs against two types of human cancer (HCT116) and normal (HUVCE) cells. A novel procedure for synthesizing ZnO-TiO2/RGO NCs has been developed using Senna surattensis extract. The improved physicochemical properties of the obtained samples were investigated using different techniques such as XRD, TEM, SEM, XPS, FTIR, DLS and UV-visible spectroscopy. XRD results showed that the addition of ZnO and RGO sheets affects the crystal structure and phase of TiO2 NPs. SEM and TEM images displayed that the TiO2 NPs and ZnO NPs were small with uniform spherical morphology in the prepared ZnO-TiO2/RGO NCs. Besides, it is shown that ZnO-TiO2 NCs anchored onto the surface of RGO sheets with a particle size of 14.80 ± 0.5 nm. XPS data confirmed the surface chemical composition and oxidation states of ZnO-TiO2/RGO NCs. Functional groups of prepared NPs and NCs were determined using FTIR spectroscopy. DLS data confirmed that the addition of ZnO and RGO sheets improves the negative surface charge of the prepared pure TiO2 NPs (-22.51 mV), ZnO NPs (-18.27 mV), ZnO-TiO2 NCs (-30.20 mV), and ZnO-TiO2/RGO NCs (-33.77 mV). Optical analysis exhibited that the bandgap energies of TiO2 NPs (3.30 eV), ZnO NPs (3.33 eV), ZnO-TiO2 NCs (3.03 eV), and ZnO-TiO2/RGO NCs (2.78 eV) were further enhanced by adding ZnO NPs and RGO sheets. This indicates that the synthesized samples can be applied to cancer therapy and environmental remediation. The biological data demonstrated that the produced ZnO-TiO2/RGO NCs show a more cytotoxic effect on HCT116 cells compared to pure TiO2 NPs and ZnO-TiO2 NCs. On the other hand, these NCs displayed the lowest level of toxicity towards normal HUVCE cells. These results indicate that the ZnO-TiO2/RGO NCs have strong toxicity against HCT116 cells and are compatible with normal cells. Our results show that the plant extract enhanced the physicochemical properties of NPs and NCs compared with the traditional chemical methods for synthesis. This study could open new avenues for developing more effective and targeted cancer treatments.

Occurrence of iodinated contrast media (ICM) in water environments and their control strategies with a particular focus on iodinated by-products formation: A comprehensive review

Iodinated contrast media (ICM), one of the pharmaceutical and personal care products (PPCPs), are frequently detected in various water bodies due to the strong biochemical stability and recalcitrance to conventional water treatment. Additionally, ICM pose a risk of forming iodinated by-products that can be detrimental to the aquatic ecosystem. Consequently, effectively removing ICM from aqueous environments is a significant concern for environmental researchers. This article provides a comprehensive review of the structural characteristics of ICM, their primary source (e.g., domestic and hospital wastewater), detected concentrations in water environments, and ecological health hazards associated with them. The current wastewater treatment technologies for ICM control are also reviewed in detail with the aim of providing a reference for future research. Prior researches have demonstrated that traditional treatment processes (such as physical adsorption, biochemical method and chemical oxidation method) have inadequate efficiencies in the removal of ICM. Currently, the application of advanced oxidation processes to remove ICM has become extensive, but there are some issues like poor deiodination efficiency and the risk of forming toxic intermediates or iodinated by-products. Conversely, reduction technologies have a high deiodination rate, enabling the targeted removal of ICM. But the subsequent treatment issues related to iodine (such as I- and OI-) are often underestimated, potentially generating iodinated by-products during the subsequent treatment processes. Hence, we proposed using combined reduction-oxidation technologies to remove ICM and achieved synchronous control of iodinated by-products. In the future, it is recommended to study the degradation efficiency of ICM and the control efficiency of iodinated by-products by combining different reduction and oxidation processes.

Origin of Cycle Performance in the Ag2O/TiO2 Heterostructure Photocatalyst

In recent years, many studies on photocatalysis focused on improving efficiency. However, the cycle performance is also an important index for industrialization. Here, an Ag2O/TiO2 heterostructure photocatalyst is prepared for continuous photodegradation of methylene blue (MB) under visible light, and the samples after the first and fifth round reactions are recycled to study the microstructure evolution of the photocatalyst. The results show that the performance is obviously improved in the second round and remains stable in the following reaction round. Due to the charge transfer, Ag2O/TiO2 gradually changes to Ag2O@Ag-TiO2-x during the photocatalytic reaction. The resulting localized surface plasmon resonance effect and the change of the interface structure greatly increase the number of carriers and prolong the lifetime of carriers. Such variations of microstructures and photoelectric properties of the samples due to the charge transfer and redox reaction on the surface of the photocatalyst dominate the cycle performance.

ZrO2-Ag2O nanocomposites encrusted porous polymer monoliths as high-performance visible light photocatalysts for the fast degradation of pharmaceutical pollutants

This work reports a unique ZrO₂-Ag₂O heterojunction nanocomposite uniformly dispersed on a macro-/meso-porous polymer monolithic template to serve as simple and effective visible light-driven heterogeneous plasmonic photocatalysts for water decontamination. The monolithic photocatalysts' structural properties and surface morphology are characterized using various surface and structural characterization techniques. The photocatalytic performance of the proposed photocatalysts is evaluated by optimizing multiple operational parameters. The photocatalytic properties of the fabricated monolithic nanocomposite are monitored through time-dependent photocatalytic disintegration of norfloxacin drug, a widely employed antimicrobial, with considerable aquatic persistence. The analytical results conclude that a (60:40) ZrO₂-Ag₂O nanocomposite embedded polymer monolith exhibits superior photocatalytic activity for the complete mineralization of norfloxacin molecules under optimized conditions of solution pH (3.0), photocatalyst quantity (100 mg), pollutant concentration (15 mg/L), photosensitizers (2.0 mM KBrO₃), visible light intensity (300 W/cm² tungsten lamp) and irradiation time (≤ 1 h). The proposed new-age inorganic-organic hybrid visible light photo-catalysts with superior structural and surface properties exhibit brilliant performance and fast responsiveness for water decontamination applications, in addition to their excellent chemical stability, high durability, multi-reusability, and cost-effectiveness.

The enhanced photocatalytic activity of TiO2(B)/MIL-100(Fe) composite via Fe–O clusters

An integrated TiO2(B)/MIL-100(Fe) composite was designed for improving photocatalytic activity via Fe–O–Ti electronic tunnel and Fe–O clusters.

Efficient Degradation of Iopromide by Using Sulfite Activated with Mackinawite

Iopromide (IOP), an iodinated X-ray contrast medium (ICM), is identified as a precursor to iodide disinfection byproducts that have high genotoxicity and cytotoxicity to mammals. ICM remains persistent through typical wastewater treatment processes and even through some hydroxyl radical-based advanced oxidation processes. The development of new technologies to remove ICMs is needed. In this work, mackinawite (FeS)-activated sulfite autoxidation was employed for the degradation of IOP-containing water. The experiment was performed in a 500 mL self-made temperature-controlled reactor with online monitoring pH and dissolved oxygen in the laboratory. The effects of various parameters, such as initial pH values, sulfite dosages, FeS dosages, dissolved oxygen, and inorganic anions on the performance of the treatment process have been investigated. Eighty percent of IOP could be degraded in 15 min with 1 g L-1 FeS, 400 μmol L-1 sulfite at pH 8, and high efficiency on the removal of total organic carbon (TOC) was achieved, which is 71.8% via a reaction for 1 h. The generated hydroxyl and oxysulfur radicals, which contributed to the oxidation process, were identified through radical quenching experiments. The dissolved oxygen was essential for the degradation of IOP. The presence of Cl- could facilitate IOP degradation, while NO3- and CO32- could inhibit the degradation process. The reaction pathway involving H-abstraction and oxidative decarboxylation was proposed, based on product identification. The current system shows good applicability for the degradation of IOP and may help in developing a new approach for the treatment of ICM-containing water.

Hydrogen peroxide-assisted photocatalytic water treatment for the removal of anthropogenic trace substances from the effluent of wastewater treatment plants

Supported titanium dioxide catalysts were used in a photocatalytic flat cell reactor to remove organic micropollutants from real wastewater. Catalysts based on stainless steel mesh with a porous coating made of titanium dioxide nanoparticles with predominantly anatase modification were used. The influence of the retention time, and light output, and the effect of hydrogen peroxide on the degradation were examined. The kinetics of the degradation of the parent substances was determined by liquid chromatography-tandem mass spectrometry. As a result, first-order degradation kinetics could be confirmed for all substances. The irradiance had no linear influence on the degradation of the compounds. Hydrogen peroxides were added to the wastewater to be treated, as electron acceptors and boosters, and alone had no great oxidative effect on the parent substances. The combination of photocatalysis with the addition of hydrogen peroxide as an electron acceptor had great synergetic effects which can reduce the required energy of the process through a short retention time. The process is suitable for the removal of micropollutants from wastewater.