Solar Photocatalytic Degradation of Trace Organic Pollutants in Water by Bi(0)-Doped Bismuth Oxyhalide Thin Films

Visible-Light-Active Iodide-Doped BiOBr Coatings for Sustainable Infrastructure

The search for efficient materials for sustainable infrastructure is an urgent challenge toward potential negative emission technologies and the global environmental crisis. Pleasant, efficient sunlight-activated coatings for applications in self-cleaning windows are sought in the glass industry, particularly those produced from scalable technologies. The current work presents visible-light-active iodide-doped BiOBr thin films fabricated using aerosol-assisted chemical vapor deposition. The impact of dopant concentration on the structural, morphological, and optical properties was studied systematically. The photocatalytic properties of the parent materials and as-deposited doped films were evaluated using the smart ink test. An optimized material was identified as containing 2.7 atom % iodide dopant. Insight into the photocatalytic behavior of these coatings was gathered from photoluminescence and photoelectrochemical studies. The optimum photocatalytic performance could be explained from a balance between photon absorption, charge generation, carrier separation, and charge transport properties under 450 nm irradiation. This optimized iodide-doped BiOBr coating is an excellent candidate for the photodegradation of volatile organic pollutants, with potential applications in self-cleaning windows and other surfaces.

A review on bismuth-based materials for the removal of organic and inorganic pollutants

Modernized lifestyle and increased industrialization threaten living organisms because of the pollutants released from industries and household wastes. The presence of even small amounts of pollutants (organic pollutants (OPs) and inorganic pollutants-heavy metals (HMs)) shows significant effects. Thus wastewater treatment is urgently needed before being subjected to use. Many methods and materials have been developed and reported for the removal of pollutants from wastewater. This review focused on the removal of both OPs and HMs using bismuth-based (Bi-based) materials because of their low toxicity and excellent properties compared to other metals. Bi-based materials as a photocatalyst for photodegradation of OPs are discussed in detail with synthesis methods. Further, since few reviews are available on the Bi-based material for the removal and sensing of HMs, this topic was intentionally summarized. About 200 published articles and reviews have been reviewed here. Additionally, the key point that needs to be focused on the development of Bi-based photocatalysts for the removal of OPs and for upgrading the Bi-based materials as adsorbents for HMs are conferred in the outlook. This will help many researchers in their upcoming work.

The room temperature synthesis of a CuO-Bi-BiOBr ternary Z-scheme photocatalyst for enhanced sunlight driven alcohol oxidation

The room temperature synthesis of an all-solid-state Z-scheme CuO-doped BiOBr (CuO-Bi-BiOBr) photocatalyst has been described. These CuO-Bi-BiOBr ternary heterojunctions exhibit efficient photocatalytic activities for selective alcohol oxidation. The structures, morphologies, and compositions of the nanostructures were well characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic absorption spectroscopy (AAS). The X-ray diffraction (XRD) pattern of the as-synthesized nanostructures confirms the formation of phase-segregated CuO and BiOBr nanocrystals, whereas X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) analyses clearly indicate the formation of metallic bismuth nanoparticles (NPs). Next, the developed CuO-Bi-BiOBr ternary heterojunctions were applied as an efficient photocatalyst for the oxidation of alcohols into their corresponding aldehydes/ketones with high selectivity (>99%) and high conversion ratios (>99%). Herein, Bi metal NPs act as an electron mediator and bridge the connectivity between the two semiconductors, BiOBr and CuO, and, thus, a Z-scheme heterojunction is established. As expected, CuO-Bi-BiOBr has shown significantly superior activities compared to those of pure BiOBr. A possible mechanism for the photocatalytic oxidation process has been proposed. Radical scavenging experiments suggest that the active species, h⁺, ˙OH, e^-, and ˙O₂^-, are dominant in the alcohol oxidation process. The as-synthesized CuO-Bi-BiOBr was reused several times without any significant deterioration in the original activities and it thus possesses relatively high stability for practical applications.

Development of novel BiOBr0.75I0.25 nanostructures with remarkably High dark phase bactericidal activities

Semiconductor materials with promising photocatalytic activities are being developed for numerous applications including their use in the development of antibacterial products. However, the light may not be available everywhere, which restrict the use of semiconductor photocatalytic materials in real applications. In this area, we report a novel nanostructure of BiOBr_0.75I_0.25 to show enormously high bactericidal activities even at dark. We used a solution based single step method at room temperature to produce highly porous and crystalline BiOBr_xI_1-x (x = 0-1) nanostructures. Next, the developed materials were thoroughly characterized by different analytical techniques, such as FESEM, XRD, XPS, etc. To evaluate the bactericidal activities Escherichia coli (gram-negative bacteria) and Bacillus subtilis (gram-positive bacteria) were selected. Interestingly we found that the solid solutions exhibited high potential towards both the bacteria and among them, BiOBr_0.75I_0.25 showed extremely high efficiencies even at dark. Due to their semiconductor behavior, the materials have shown higher activities in the presence of any light source. The knowledge about the behavior of these unique materials revels a new area of research and would certainly help to find out the solution for ever-increasing environmental issues.

Bismuth Oxyhalides for NOx Degradation under Visible Light: The Role of the Chloride Precursor

Photocatalysis is a green technology for tackling water and air contamination. A valid alternative to the most exploited photocatalytic material, TiO2, is bismuth oxyhalides, which feature a wider bandgap energy range and use visible radiation to attain photoexcitation. Moreover, their layered structure favors the separation of photogenerated electron–hole pairs, with an enhancement in photocatalytic activity. Controlled doping of bismuth oxyhalides with metallic bismuth nanoparticles allows for further boosting of the performance of the material. In the present work, we synthesized Y%Bi-doped BiO(Cl0.875Br0.125) (Y = 0.85, 1, 2, 10) photocatalysts, using cetyltrimethylammonium bromide as the bromide source and varying the chloride source to assess the impact that both length and branching of the hydrocarbon chain might have on the framing and layering of the material. A change in the amount of the reducing agent NaBH4 allowed tuning of the percentage of metallic bismuth. After a thorough characterization (XRPD, SEM, TEM, UV-DRS, XPS), the photocatalytic activity of the catalysts was tested in the degradation of NOx under visible light, reaching a remarkable 53% conversion after 3 h of illumination for the material prepared using cetylpyridinium chloride.

Fe(II)-activated persulfate oxidation to degrade iopamidol in water: parameters optimization and degradation paths

Iodinated contrast media (ICM), which was widely used in medical imaging and was difficult to remove by conventional wastewater treatment methods, attained much attention due to its potential environmental impacts. Herein, iopamidol (IPM), one typical compound of ICM, was found to be rapidly degraded by ferrous activated persulfate oxidation (Fe(II)/PS) as compared with PS or Fe(II) alone. With a persulfate concentration of 1 mmol L⁻¹, n(Fe(II))/n(PS) of 1:10, and a pH of 3.0, 78% IPM was degraded within 60 min, with a degradation rate of 0.1266 min⁻¹. It was demonstrated that IPM degradation and deiodination were favored by a high temperature, while affected positively by acidic and neutral conditions. Radical quenching experiments and Electron Paramagnetic Resonace (EPR) spectra showed that the combined effects of SO₄⁻· and ·OH contributed dominantly to degrade IPM, while the ·OH played an essential role during the degradation reaction. Through the Discrete Fourier Transform quantum chemical calculation, the possible reaction pathways for the oxidation of IPM by ·OH are as follows: IPM-TP651-TP667-TP541-TP557, IPM-TP651-TP525-TP557, IPM-TP705-TP631-TP661, and IPM-TP705-TP735. The obtained results showed that IPM could be degraded effectively by Fe(II)/PS system, giving a promising technique for IPM removal from water.

Innovative and Cost-Efficient BiOI Immobilization Technique on Ceramic Paper-Total Coverage and High Photocatalytic Activity

In the present work, visible light active bismuth oxyiodide (BiOI) was immobilized on a commercial, non-conductive support (an Al2O3 based ceramic paper) using a novel two-step spray coating technique and investigated with different characterization methods (e.g., SEM, Raman, XPS). Our main goal was to eliminate the separation costs after the photocatalytic measurement and investigate the chemical relevance and opportunity to use this technique in the industry. Our as-prepared uniform BiOI layer had similar properties to the well-known reference BiOI powder. The Raman and XPS measurements confirmed that the enriched amount of the surface iodine defined the color and as well the band gap of the BiOI layer. The durable BiOI layers have prominent photocatalytic activity under UV and visible light irradiation as well. The scale-up procedure proved that the designed BiOI coated paper was reusable and potentially applicable in the industry by straightforward scale-up, which is due to the elaborated non-conventional BiOI coverage estimation method. This immobilization technique could open several opportunities for immobilizing many other visible light active photocatalysts with simple materials and low cost.

Highly efficient degradation of iohexol on a heterostructured graphene-analogue boron nitride coupled Bi2MoO6 photocatalyst under simulated sunlight

Iohexol (IOH), as a typical iodinated X-ray contrast media (ICMs) with potential threat to human health, is difficult to be removed with the conventional wastewater treatment methods. In this work, new boron nitride coupled Bi₂MoO₆ layered microspheres (BN/Bi₂MoO₆) composites were applied to remove IOH from water via photocatalytic degradation. The degradation constant k_app of IOH over 3.5 wt% BN/Bi₂MoO₆ was 0.016 min^-1, which was 3.2 times that of Bi₂MoO₆ (0.005 min^-1). The degradation rate of IOH on 3.5 wt% BN/Bi₂MoO₆ reached 92% in 150 min. The enhanced photocatalytic activity of BN/Bi₂MoO₆ can be attributed to the heterojunction between BN and Bi₂MoO₆. The matched type-I band alignment heterojunction of two semiconductors prominently improved the charge separation. Based on the trapping experiments, holes and superoxide radicals were proved to be the main active species for photocatalytic IOH degradation. Besides, the degradation products of IOH were analyzed by LC-HRMS and the possible degradation mechanism of IOH was also proposed in this work.

The pH dependent surface charging and points of zero charge. VIII. Update

A critical review of the points of zero charge (PZC) obtained by potentiometric titration and of isoelectric points (IEP) obtained by electrokinetic measurements. The results from the recent literature are presented with experimental details (temperature, method, type of apparatus, etc.), and they are compared with the zero points of similar materials reported in older publications. Most studies of PZC and IEP reported in the recent papers were carried out for metal oxides and hydroxides, especially alumina, iron oxides, and titania, and the results are consistent with the PZC and IEP of similar materials reported in older literature, and summarized in previous reviews by the same author. Relatively few studies were carried out with less common materials, and IEP of (nominally) VO₂ and BN have been reported for the 1st time.

Effect of Ag–Fe–Cu tri-metal loading in bismuth oxybromide to develop a novel nanocomposite for the sunlight driven photocatalytic oxidation of alcohols

Metal-doped BiOBr was synthesized and used as a reusable sunlight driven photocatalyst for the selective oxidation of alcohols into corresponding aldehydes/ketones.