Effect of bismuth doping on the crystal structure and photocatalytic activity of titanium oxide.

The doping of TiO2 with metals and non-metals is considered one of the most significant approaches to improve its photocatalytic efficiency. In this study, the photodegradation of methyl orange (MO) was examined in relation to the impact of Bi-doping of TiO2. The doped TiO2 with various concentrations of metal was successfully synthesized by a one-step hydrothermal method and characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and UV-vis spectroscopy. The XRD results revealed that the anatase phase, with an average crystallite size of 16.2 nm, was the main phase of TiO2. According to the anatase texture results, it was found that the doping of TiO2 increased the specific surface area for Bi2O3@TiO2 without a change in the crystal structure or the crystal phase of TiO2. Also, XPS analysis confirmed the formation of Ti4+ and Ti3+ as a result of doping with Bi. The activities of both pure TiO2 and Bi-doped TiO2 were tested to study their ability to decolorize MO dye in an aqueous solution. The photocatalytic degradation of MO over Bi2O3@TiO2 reached 98.21%, which was much higher than the 42% achieved by pure TiO2. Doping TiO2 with Bi increased its visible-light absorption as Bi-doping generated a new intermediate energy level below the CB edge of the TiO2 orbitals, causing a shift in the band gap from the UV to the visible region, thus enhancing its photocatalytic efficiency. In addition, the effects of the initial pH, initial pollutant concentration, and contact time were examined and discussed.

Cobalt doped titania-carbon nanosheets with induced oxygen vacancies for photocatalytic degradation of uranium complexes in radioactive wastes.

The photocatalytic degradation of uranium complexes is considered among the most efficient techniques for the efficient removal of uranium ions/complexes from radioactive wastewater. Described here is a nanostructured photocatalyst based on a cobalt-doped TiO2 composite with induced oxygen vacancies (Co@TiO2-C) for the photocatalytic removal of uranium complexes from contaminated water. The synergy between oxygen vacancies and Co-doping produced a material with a 1.7 eV bandgap, while the carbon network facilitates electron movement and hinders the e-h recombination. As a result, the new photocatalyst enables the decomposition of uranium-arsenazo iii complexes (U-ARZ3), followed by photocatalytic reduction of hexavalent uranium to insoluble tetravalent uranium. Combined with the nanosheet structure's high surface area, the photocatalytic decomposition, reduction efficiency, and kinetics were significantly enhanced, achieving almost complete U(vi) removal in less than 20 minutes from solution with a concentration as high as 1000 mL g-1. Moreover, the designed photocatalyst exhibits excellent stability and reusability without decreasing the photocatalytic performance after 5 cycles.

Characteristic Aspects of Uranium(VI) Adsorption Utilizing Nano-Silica/Chitosan from Wastewater Solution.

A new nano-silica/chitosan (SiO2/CS) sorbent was created using a wet process to eliminate uranium(VI) from its solution. Measurements using BET, XRD, EDX, SEM, and FTIR were utilized to analyze the production of SiO2/CS. The adsorption progressions were carried out by pH, SiO2/CS dose, temperature, sorbing time, and U(VI) concentration measurements. The optimal condition for U(VI) sorption (165 mg/g) was found to be pH 3.5, 60 mg SiO2/CS, for 50 min of sorbing time, and 200 mg/L U(VI). Both the second-order sorption kinetics and Langmuir adsorption model were observed to be obeyed by the ability of SiO2/CS to eradicate U(VI). Thermodynamically, the sorption strategy was a spontaneous reaction and exothermic. According to the findings, SiO2/CS had the potential to serve as an effectual sorbent for U(VI) displacement.

Design and synthesis of a combined meso-adsorbent/chemo-sensor for extraction and detection of silver ions.

We synthesized a new pH-dependent meso-captor/sensor for the visual monitoring and selective sequestering of Ag(I) ions from wastewater. The SBA-16 microspheres were successfully synthesized via a direct hydrothermal treatment through surfactant-assisted cooperative self-assembly. The meso-captor/sensor was designed via the direct immobilization of the chromogenic Acid Blue 90 (AB90) chelate into cubical large, open mesoporous SBA-16 carriers and investigate of its ability to detect and retain silver ions from aqueous solutions. Results show that the synthesized SBA-16 microspheres were retained after modification and the AB90 functional groups were immobilized hierarchically inside the mesopore channels. This was evidenced by the N2 adsorption, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HR-TEM), and elemental analyses. Batch adsorption experiments were carried out and the effects of various parameters on Ag(I) ions removal and detection were determined. The optimum adsorption/detection of Ag(I) ions were recorded at a pH of 6.2 within 30 min with color change from a brilliant blue to a pale blue-gray. The spectral response for [SBA-16@AB90 â†’ Ag(I)] complex showed a maximum reflectance at λmax = 385 nm within 2.5 min response time (tR); the LOD was close to 3.87 µg/L while the LOQ approached 12.83 µg/L, this was attributed to the concentration range at which a linear signal has been observed against Ag(I) analyte concentration (i.e., 5 to 1000 µg/L) at pH 6.2 with standard deviation (SD) of 0.077 (RSD% = 9.5 at n = 8).

Cubically cage-shaped mesoporous ordered silica for simultaneous visual detection and removal of uranium ions from contaminated seawater.

A dual-function organic-inorganic mesoporous structure is reported for naked-eye detection and removal of uranyl ions from an aqueous environment. The mesoporous sensor/adsorbent is fabricated via direct template synthesis of highly ordered silica monolith (HOM) starting from a quaternary microemulsion liquid crystalline phase. The produced HOM is subjected to further modifications through growing an organic probe, omega chrome black blue G (OCBBG), in the cavities and on the outer surface of the silica structure. The spectral response for [HOM-OCBBG → U(VI)] complex shows a maximum reflectance at λmax = 548 nm within 1 min response time (tR); the LOD is close to 9.1 µg/L while the LOQ approaches 30.4 µg/L, and this corresponds to the range of concentration where the signal is linear against U(VI) concentration (i.e., 5-1000 µg/L) at pH 3.4 with standard deviation (SD) of 0.079 (RSD% = 11.7 at n = 10). Experiments and DFT calculations indicate the existence of strong binding energy between the organic probe and uranyl ions forming a complex with blue color that can be detected by naked eyes even at low uranium concentrations. With regard to the radioactive remediation, the new mesoporous sensor/captor is able to reach a maximum capacity of 95 mg/g within a few minutes of the sorption process. The synthesized material can be regenerated using simple leaching and re-used several times without a significant decrease in capacity.

Nanoporous colorant sensors and captors for simultaneous recognition and recovery of gold from E-wastes.

Platinum group metals have gained significant interest due to their unique characteristics, which make them the main constituents in advanced applications. In this work, we introduce new pH-dependent optical mesocaptors for the colorimetric monitoring and separation of Au(III) from E-waste leach liquors without a preconcentration process. The mesoporous silica nanospheres are fabricated via simple, reproducible, and low-cost procedures. The optical mesocaptor is designed via indirect immobilization of thiazole yellow G (TYG) and amacid yellow M (AYM) chromogenic probes onto mesoporous nanostructured scaffolds. The silanol groups in the mesopores of silica surface robustly anchored dilauryl dimethyl ammonium bromide (DDAB) linker to induce the interactions with the TYG and AYM chelates, thereby leading to the fashioning of a stable optical mesocaptors without releasing of the chelates throughout adsorption and sensing assays. The finding provides evidence of the capability of the synthesized decorated new nanostructured sensor shows excellent sensitivity toward Au(III) with a limit of detection (LOD) as low as 1.16 µg L-1. Furthermore, the new sensors were able to selectively detect Au(III) in solution with multi ions components.

Decontamination of radioactive cesium ions using ordered mesoporous monetite.

We report herein the fabrication of an environmentally friendly, low-cost and efficient nanostructured mesoporous monetite plate-like mineral (CaHPO4) as an adsorbent for removal of radioactive cesium ions from aqueous solutions. The phase and textural features of the synthesized mesoporous monetite were well characterized by XRD, FTIR, SEM, HRTEM, DLS, TGA/TDA, and N2 adsorption/desorption techniques. The results indicate that the cesium ions were effectively adsorbed by the mesoporous monetite ion-exchanger (MMT-IEX) above pH 9.0. Different kinetic and isotherm models were applied to characterize the cesium adsorption process. The fabricated monetite exhibited a monolayer adsorption capacity up to 60.33 mg g-1 at pH of 9.5. The collected data revealed the higher ability of CaHPO4 for the removal of Cs(i) from aqueous media in an efficient way.

Nanomembrane Canister Architectures for the Visualization and Filtration of Oxyanion Toxins with One-Step Processing.

Nanomembrane canister-like architectures were fabricated by using hexagonal mesocylinder-shaped aluminosilica nanotubes (MNTs)-porous anodic alumina (PAA) hybrid nanochannels. The engineering pattern of the MNTs inside a 60 µm-long membrane channel enabled the creation of unique canister-like channel necks and cavities. The open-tubular canister architecture design provides controllable, reproducible, and one-step processing patterns of visual detection and rejection/permeation of oxyanion toxins such as selenite (SeO3(2-)) in aquatic environments (i.e., in ground and river water sources) in the Ibaraki Prefecture of Japan. The decoration of organic ligand moieties such as omega chrome black blue (OCG) into inorganic Al2O3@tubular SiO2/Al2O3 canister membrane channel cavities led to the fabrication of an optical nanomembrane sensor (ONS). The OCG ligand was not leached from the canister as observed in washing, sensing, and recovery assays of selenite anions in solution, which enabled its multiple reuse. The ONS makes a variety of alternate processing analyses of selective quantification, visual detection, rejection/permeation, and recovery of toxic selenite quick and simple without using complex instrumentation. Under optimal conditions, the ONS canister exhibited a high selectivity toward selenite anions relative to other ions and a low-level detection limit of 0.0093 µM. Real analytical data showed that approximately 96% of SeO3(2-) anions can be recovered from aquatic and wastewater samples. The ONS canister holds potential for field recovery applications of toxic selenite anions from water.

Monolithic scaffolds for highly selective ion sensing/removal of Co(II), Cu(II), and Cd(II) ions in water.

High exposure to metals, such as cobalt (Co), copper (Cu) and cadmium (Cd), potentially has adverse effects, and can cause severe health problems, leading to a number of specific diseases. This study primarily aims to monitor, detect, separate, and remove the trace concentrations of Co(II), Cu(II), and Cd(II) ions in water, without a preconcentration process, using aluminosilica optical sensor (ASOS) monoliths. These monolithic scaffolds with advantageous physical features (i.e., large surface area-to-volume ratios of the scaffolds, active acid sites and uniform mesocage cubic pores) can strongly induce H-bonding and dispersive interactions with organic chelating agent, resulting in the formation of stable ASOS. In this engineering process, ASOS offers a simple and one-step sensing/capture procedure for the quantification and visual detection of the target elements from water, without requiring sophisticated instrumentation. The key result in this study is the ion selectivity exhibited by the designed ASOS toward the targets, Co(II), Cu(II), and Cd(II) ions, in environmental and waste disposal samples, as well as its reproducibility over a number of analysis/regeneration cycles. These findings can be useful in the fabrication of ASOS can be tailored to suit various applications.

Hierarchical inorganic-organic multi-shell nanospheres for intervention and treatment of lead-contaminated blood.

The highly toxic properties, bioavailability, and adverse effects of Pb(2+) species on the environment and living organisms necessitate periodic monitoring and removal whenever possible of Pb(2+) concentrations in the environment. In this study, we designed a novel optical multi-shell nanosphere sensor that enables selective recognition, unrestrained accessibility, continuous monitoring, and efficient removal (on the order of minutes) of Pb(2+) ions from water and human blood, i.e., red blood cells (RBCs). The consequent decoration of the mesoporous core/double-shell silica nanospheres through a chemically responsive azo-chromophore with a long hydrophobic tail enabled us to create a unique hierarchical multi-shell sensor. We examined the efficiency of the multi-shell sensor in removing lead ions from the blood to ascertain the potential use of the sensor in medical applications. The lead-induced hemolysis of RBCs in the sensing/capture assay was inhibited by the ability of the hierarchical sensor to remove lead ions from blood. The results suggest the higher flux and diffusion of Pb(2+) ions into the mesopores of the core/multi-shell sensor than into the RBC membranes. These findings indicate that the sensor could be used in the prevention of health risks associated with elevated blood lead levels such as anemia.