Delta SARS-CoV-2 inactivation and bactericidal performance of cotton wipes decorated with TiO2/Ag nanoparticles like Brazilian heavy-fruited Myrciaria cauliflora

The current pandemic of Coronavirus Disease 2019 (COVID-19) raised several concerns about using conventional textiles for manufacturing personal protective equipment without self-disinfecting properties since the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is transmitted mainly by aerosols that can transpose cotton masks. Therefore, developing new cotton fibers with high self-disinfecting ability is essential to avoid a new pandemic due to new SARS-CoV-2 variants. Herein, we developed cotton wipes (CFs) with fibers coated by Ag, TiO₂, and Ag/TiO₂ hybrid nanoparticles like Brazilian heavy-fruited Myrciaria cauliflora by a sonochemical approach. Moreover, the coated CFs present high antimicrobial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), being able to inactivate infectious SARS-CoV-2 (Delta variant) by the destruction of the spike, membrane, and nucleocapsid proteins while the viral RNA is not significantly affected, according to the molecular biological findings.

Influence of pH on the Kinetics and Products of Photocatalytic Degradation of Sulfonamides in Aqueous Solutions

The aims of the study were to determine the kinetics of the photocatalytic degradation of six sulfonamides in the presence of TiO₂-P25 in acidic, neutral, and alkaline solutions and to identify the structures of the stable products. It was stated that the pH of the solution significantly affected the photocatalytic degradation rate of sulfonamides in acidic and alkaline environments, and the effect likely depended on the susceptibility of sulfonamides to attack by hydroxyl radicals. In the post-reaction mixture, we identified the compounds resulting from the substitution of the aromatic rings with a hydroxyl group; the amide hydrolysis products; the hydroxylamine-, azo, and nitro derivatives; and the compounds formed via the elimination of the sulfone group. Moreover, previously unknown azo compounds were detected. Some degradation products of sulfonamides may exhibit marked bacteriostatic activity and high phytotoxicity. The azo and nitro compounds formed in an acidic environment may be potentially more toxic to aquatic ecosystems than the initial compounds.

Effective photocatalytic degradation of amoxicillin using MIL-53(Al)/ZnO composite

A promising hierarchical nanocomposite of MIL-53(Al)/ZnO was synthesized as a visible-light-driven photocatalyst to investigate the degradation of amoxicillin (AMX). MIL-53(Al)/ZnO ultrafine nanoparticles were obtained by preparing Zn-free MIL-53Al and employing it as a reactive template under hydrothermal and chemical conditions. The synthesized nanocomposite (MIL-53(Al)/ZnO) has a low content of Al > 1.5% with significantly different characterizations of the parent compounds elucidated by various analyses such as SEM, TEM, XRD, EDX, and UV-Vis. The effect of operational parameters (catalyst dose (0.2-1.0 g/L), solution pH (3-11), and initial AMX concentration (10-90 mg/L)) on the AMX removal efficiency was studied and optimized by the response surface methodology. A reasonable goodness-of-fit between the expected and experimental values was confirmed with correlation coefficient (R²) equal to 0.96. Under the optimal values, i.e., initial AMX concentration = 10 mg/L, solution pH ~ 4.5, and catalyst dose = 1.0 g/L, 100% AMX removal was achieved after reaction time = 60 min. The degradation mechanism and oxidation pathway were vigorously examined. The AMX degradation ratios slightly decreased after five consecutive cycles (from 78.19 to 62.05%), revealing the high reusability of MIL-53(Al)/ZnO. The AMX removal ratio was improved with enhancers in order ([Formula: see text]> H₂O₂ > S₂O₈^-2). The results proved that 94.12 and 98.23% reduction of COD were obtained after 60 and 75 min, respectively. The amortization and operating costs were estimated at 3.3 $/m³ for a large-scale photocatalytic system.

Degradation of ramipril by residues from the brewing industry: A new carbon-based photocatalyst compound

This study is a pioneer in the use of hydrochar as a support for photocatalytic oxide and its application and evaluation as a catalyst in degradation reactions of ramipril. Novel composites were easily prepared by the support TiO₂ or ZnO nanoparticles on the malt bagasse hydrochar. The preparation of the hydrochar requires low synthesis temperature (250 °C), generating the energy savings of the process. The production of the new composites was well supported by different analytical techniques XRD, FTIR, SSA, SEM, EDS, and reflectance diffuse. The effect of different proportions of TiO₂ or ZnO on the composites was investigated on the degradation efficiency of the pharmaceutical ramipril, without pH adjustment. Composites with a 5:1 hydrochar/TiO₂ or ZnO ratio (MH5T and MH5Z, respectively) showed degradations of 72 and 98% of ramipril at 120 min. This remarkable performance may be associated with the decrease in band gap energy and the electron-hole recombination rate. In addition, the composites were more efficient than metal oxides pristine, and this may be related to the fact that hydrochar have a high concentration of phenolic, hydroxyl, and carboxylic functional groups on their surface. Radical identification tests indicated that h⁺, O₂•^-, and •OH were the reactive species involved in the degradation. The proposed mechanism was studied via LC-MS/MS indicated that the ramipril molecule degrades into low m/z intermediates in the first 60 min of reaction using the MH5Z.

Synergic effect of Guggul gum based hydrogel nanocomposite: An approach towards adsorption-photocatalysis of Magenta-O

The article is related to sunlight and UV-visible mineralization of harmful magenta-O (FB) dye. The nanocomposite used is a cross linked network of acrylic acid synthesized inside poly(acrylamide) grafted Guggul gum in the presence of UV-visible respondent bismuth ferrite nanoparticles. The synthesis of poly(acrylamide) grafted Guggul gum (Sample I) and synthesizing a crosslinked network inside it (Sample II) involved a two-step synthesis for optimizing various reaction parameters. The maximum % water uptake obtained for polymeric samples I and II was calculated as 1227.78% and 387.97%, respectively. Average particle size of bismuth ferrite nanoparticles was 47.34 nm. The nanocomposite could maximum uptake-mineralize FB dye as 97.3% and 98.8% under sunlight and photochemical reactor, respectively for 500 mg nanocomposite dose in 10 mg/L concentrated FB solution. Dye uptake occurs through ionic interactions. However, mineralization is a consequence of advanced oxidation process involving free radical species (OH and O₂^-.). The overall process of uptake-mineralization resembled second order kinetics and Langmuir theorem (monolayer adsorption). Intraparticle diffusion model gave an idea about the multistep (three steps) process of adsorption. Physico-chemical properties of FB dye got changed after mineralization except for the pH. The maximum uptake-mineralization was observed to be 76.2% after consecutive reuse of the nanocomposite hydrogel for five cycles.

Synthesis of N-Doped ZnO Nanocomposites for Sunlight Photocatalytic Degradation of Textile Dye Pollutants

Undoped and N-doped ZnO nanocomposites are produced by a simple and low-cost mechanochemical method. The characterizations of all nanocomposites are examined by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), scanning electron microscopy (SEM) and UV-Vis-NIR spectroscopy. The XRD measurements show that the crystal sizes of undoped and N-doped ZnO nanocomposites are ~29 and ~28 nm, respectively. The UV-Vis-NIR spectroscopy results illustrate that the transmittance of the 7 wt% N/ZnO in the visible and infrared region is a bit higher than the undoped ZnO. The photocatalytic activity of undoped and N-doped ZnO nanocomposites is investigated for the degradation of Methylene Blue (MB) and Rhodamine B (RhB) aqueous solution with direct sunlight irradiation. The photocatalytic degradation percentages with 7 wt% N/ZnO for 5 and 10 mg/L MB dye solution are found to be 93.70% and 98.11%, respectively, whereas 78.40% and 89.15% degradation percentages are found with undoped ZnO, after 3 h sunlight irradiation. Under the same conditions, the photocatalytic degradation value of RhB dye (10 mg/L) solution is measured to be 86.21% for 7 wt% N/ZnO and 64.75% for undoped ZnO. The N-doped ZnO nanocomposites are found to exhibit enhanced photocatalytic performance for both dyes’ degradation under sunlight irradiation in comparison with the undoped ZnO. Therefore, the photocatalytic degradation treatment of wastewater including dye pollutants with sunlight is an easy and simple technique, and cost-effective.

Enhanced photocatalytic degradation of methyl orange dye on interaction with synthesized ligand free CdS nanocrystals under visible light illumination

Methyl orange is widely used dye in textile industry and later, it becomes the major component of industrial waste and pollutes different water body. So, its degradation is required especially in the case of drinking water. Here, chemically synthesized ligand free CdS nanocrystals have been utilized as a photocatalyst to degrade this dye in water. The mean size of the CdS nanocrystal has been found to be 7 nm approximately from TEM analysis, and SAED pattern shows that these are crystalline in nature. Further, the XRD patterns confirms the cubic structure of CdS nanoparticles and mean size calculated from XRD analysis matches well with the obtained size from TEM study. NMR study clearly verifies that CdS nanocrystals are ligand free stable nanoparticles. Due to this absence of ligand on the surface of CdS nanocrystals, a much enhanced MO degradation has been observed, as the e^--h⁺ pair in the CdS and subsequent generation of free radicals such as hydroxyl, can efficiently oxidize the organic material MO and therefore, degrade this pollutant faster under visible light illumination. The degradation efficiency is found to be 95% after 300 min of illumination, which is much better than the other similar reports.

Highly efficient SrTiO3/Ag2O n-p heterojunction photocatalysts: improved charge carrier separation and enhanced visible-light harvesting

Strontium titanate (SrTiO₃) with perovskite structure has recently received significant attention in t he area of photocatalysis. However, challenges remain relating to its industrial applications; the high charge carrier recombination rate and low light-harvesting efficiency being the main two. Herein, a novel strategy based on fabrication of a typical n-p heterojunction has been proposed and the typical narrow-bandgap p-type semiconductor Ag₂O was chosen to be coupled with SrTiO₃ using a facile chemical precipitation method. The phase compositions, microstructures and optical properties of the prepared SrTiO₃/Ag₂O heterostructured photocatalysts have been systematically investigated with an x-ray diffractometer, scanning electron microscope, high resolution transmission electron microscope, x-ray photoelectron spectroscope and UV-vis spectrophotometer. The photocatalytic properties were evaluated through photodegradation of a common organic dye Rhodamine B (RhB). The results demonstrated that the heterostructured photocatalyst SrTiO₃/Ag₂O-0.15 outperformed pristine SrTiO₃ and Ag₂O. Specifically, the reaction rate of SrTiO₃/Ag₂O-0.15 is about 69 times and 4 times that of bare SrTiO₃ and Ag₂O respectively in photodegradation of RhB. The excellent photocatalytic performance was attributed to the synergetic effect between the improved visible-light harvesting efficiency and inhibited electron-hole recombination rate arising from the built-in electric field in a p-n heterojunction, as evidenced by the transient photocurrent and photoluminescence spectrum investigation. Furthermore, the excellent recyclability of the heterostructured photocatalyst was confirmed and holes were verified to be the major active species contributing to the overall degradation. Our findings demonstrate construction of p-n heterojunctions with narrow-bandgap semiconductors as a feasible avenue to promote overall photocatalytic efficiency, through simultaneously boosting charge-carrier separation and expanding photon-absorption range.

Complete removal of endocrine disrupting compound and toxic dye by visible light active porous g-C3N4/H-ZSM-5 nanocomposite

Photocatalytic degradation of toxic pollutants is an efficient technique to completely remove the toxic pollutants from water bodies. In the present investigation, photocatalytic degradation of pollutants was studied over porous g-C₃N₄/H-ZSM-5 nanocomposite under visible light irradiation. The composite g-C₃N₄/H-ZSM-5 was synthesized by mixing an aqueous solution of H-ZSM-5 zeolite (increases surface area and provides active sites for degradation) with melamine (precursor of g-C₃N₄) for 10-12 h followed by calcinations at 550 °C. The photocatalyst was characterized by XRD, BET, HRTEM, FESEM, EDS and elemental mapping analysis. These techniques confirmed that, g-C₃N₄/H-ZSM-5 composite have layered and porous structure with uniform distribution of g-C₃N₄ on H-ZSM-5 surface. The BET N₂ adsorption-desorption analysis verified that the catalyst has high surface area (∼175 m²/g) having mesopores and micropores. The prepared catalyst was then used for the photodegradation of a model dye, Methylene Blue (MB) and an endocrine disrupting compound, Fipronil (FIP). Effects of various parameters such as pH, catalyst dose and scavengers were also studied. The % photocatalytic degradation of MB and FIP were around ∼92% and ∼84% with a high rate constants of 0.00997 and 0.00875 min^-1, respectively. From the scavenger study, OH (hydroxyl radical) and radical was found to be the major reactive species for MB and FIP degradation. From these studies it is revealed that, the catalyst is visible active, easy to prepare and an efficient photocatalyst for toxic pollutant degradation.

Preparation of pod-shaped TiO2 and Ag@TiO2 nano burst tubes and their photocatalytic activity

The pod-shaped TiO2 nano burst tubes (TiO2 NBTs) were prepared by the combination of electrospinning and impregnation calcination with oxalic acid (H2C2O4), polystyrene (PS) and tetrabutyl titanate. The silver nanoparticles (AgNPs) were loaded onto the surface of TiO2 NBTs by ultraviolet light reduction method to prepare pod-shaped Ag@TiO2 NBTs. In this work, we analysed the effect of the amount of oxalic acid on the cracking degree of TiO2 NBTs; the effect of the concentration of AgNO3 solution on the particle size and loading of AgNPs on the surface of TiO2 NBTs. Scanning electron microscopy and transmission electron microscopy investigated the surface morphology of samples. X-ray diffraction and X-ray photoelectron spectroscopy characterized the structure and composition of samples. Rhodamine B (RhB) solution was used to evaluate the photocatalytic activity of pod-shaped TiO2 NBTs and Ag@TiO2 NBTs. The results showed that TiO2 NBTs degraded 91.0% of RhB under ultraviolet light, Ag@TiO2 NBTs degraded 95.5% under visible light for 75 and 60 min, respectively. The degradation process of both samples was consistent with the Langmuir-Hinshelwood first-order kinetic equation. Therefore, the catalytic performance of the sample is: Ag@TiO2 NBTs > TiO2 NBTs > TiO2 nanotubes.

Treatments for color removal from wastewater: State of the art

It is evident from many recent papers that release of colored wastewater into the environment is source of pollution and this is a problem that particularly affect textile, dyeing and food industries. The review: (i) presents an analysis of various mechanisms involved in the different processes for color removal; (ii) describes conveniences and disadvantages that may exist in adopting one type of treatment in spite of another; (iii) reports the results of approximately 180 experimental tests. Both examples of treatments already widely applied to the real scale and still in the experimental phase are reported. This work focuses on different types of chemical/physical, chemical, electrochemical and biological processes applied in the field of color removal from industrial wastewater. Common chemical/physical treatments such as coagulation/flocculation, adsorption and membrane filtration as well as chemical-type processes are discussed, both those that exploit the traditional oxidizing chemical agents such as Ozone, H₂O₂ and reactive based on chlorine and those based on the principle of advanced chemical oxidation. In particular, both Hydroxyl radical based Advanced Oxidation Processes (AOPs) and Sulfate radical based AOPs are reported. The most commonly used Electrochemical processes for the removal of color are also presented as well as biological treatments. Based on more than 200 papers, this review provides important information on the use, effectiveness, advantages and downsides of the various treatments aimed at removing the color from the wastewater with a look at the technologies still under development.