Continuous Photocatalytic Antibacterial Activity of AgNPs doped TiO2 Digital Printed on Commercial Porcelain-grès Tiles

Photocatalytic finishing materials, such as tiles or paints, are a productive as well as scientific reality. One of the most interesting photocatalytic material currently on the market is the porcelain stoneware which combines the beauty of a design product with hardness and absence of porosity and thus used for both floors and walls. The Ag- micrometric TiO2 allowed active ceramic slabs to be active under LED lights, bypassing the problem of the UVA radiation. SEM/TEM images in Fig. 1 indicate the full coverage of the porcelain surface (left image), besides a nanometric though heterogenous spreading of the AgNPs on top of the TiO2 matrix (right image). Figure 1. HR-SEM of the Active ceramic surface (left), TEM image of 8% AgNPs-TiO2(center); possible photocatalytic mechanistic pathways in Ag doped TiO2 system (right) An important question concerns the antibacterial action: in fact, today the role of silver is unknown when the metal is physically blocked on a surface and cannot penetrate and therefore interfere at the DNA level in the cellular barrier. The prepared porcelain Ag-TiO2 printed surfaces were tested against E. coli under solar and visible illumination and in the dark. To differenciate the semicondutor behavior and the ions mediated bacterial inactivation mechanism, porinless E. coli were used under band-gap irradiation. Stereomicroscopy analysis showed dead bacteria within 180 and 240 min respectively for normal E. coli and porinless E. coli. Using appropriate quenchers, the bacterial inactivation mechanisms under solar and visible light are proposed

Synthesis of Magnetic Recoverable Electron-rich TCTA@PVP based Conjugated Polymer for Photocatalytic Water Remediation and Disinfection

In this study, we report the synthesis of magnetic electron-rich CP@Fe3O4(Conjugated Polymer (CP) = TCTA-PVP-bipyridine) by hydrothermal method. For this aim, the Fe3O4nanoparticles were incorporated into photoactive TCTA-PVP-bipyridine based Conjugated Polymer. The photo-redox abilities of CP@Fe3O4and bare CPwere tested for oxidation of methylene blue and reduction of Cr(VI) under UV\u2013visible light and visible light(\u3bb> 420 nm). The CP@Fe3O4showed a good ability for performing the Fenton-like reaction by adding H2O2asoxidizing agent. Additionally, reveals high photocatalytic reduction ability of Cr(VI) for CP@Fe3O4in compare with bare CP. Furthermore the photocatalytic antibacterial ability of CP@Fe3O4towardsE. coliandPseudomonasAerogenosain water was studied. The obtained CFU reduction efficiencies were found about 85% and 90% forE.coliandP. Aeruginosa, respectively. Interestingly the collecting and recyclability of CP@Fe3O4after photo-catalytic reactions were done easily due to its magnetic property

Removal of Crystal Violet and Hexavalent Chromium using TiO2-Bentonite under Sunlight: Effect of TiO2 Content

The main objective of this study was to investigate the correlation between TiO2 content in photoactive bentonite (B-TiO2) and the pathway by which crystal violet (CV) and hexavalent chromium (Cr (VI)) are removed from water under sunlight. B-TiO2 samples were prepared by impregnation with TiCl4 with different weight ratios (g/g) (namely, 5, 10, 20 and 30%). Materials were characterized using different techniques, among which: SEM, FT-IR, XRD, HRTEM, EDX and Zeta potential measurements. Results show that, only the anatase TiO2 polymorph was formed in the bentonite and the porosity of materials decreases with the increase of TiO2 content. Furthermore, zeta potential measurements indicate that, when TiO2 content increases, the negative charge of materials decreases. On the other hand, experimental results show that these materials combine both adsorption and photocatalytic reactions to remove CV molecules from water. As the TiO2 content increases, the adsorption capacity decreases, while the photocatalytic activity is more important. In the case of Cr (VI) species, all samples show a few adsorption because of the repulsion effect between these species and the negative charge of the bentonite. Therefore, under sunlight, the Cr (VI) removal occurred mainly by the photoreduction reaction that is more efficient when the TiO2 content increases

Oxidative inactivation of SARS-CoV-2 on photoactive AgNPs@Tio2 ceramic tiles

The current SARS-CoV-2 pandemic causes serious public health, social, and economic issues all over the globe. Surface transmission has been claimed as a possible SARS-CoV-2 infection route, especially in heavy contaminated environmental surfaces, including hospitals and crowded public places. Herein, we studied the deactivation of SARS-CoV-2 on photoactive AgNPs@TiO2 coated on industrial ceramic tiles under dark, UVA, and LED light irradiations. SARS-CoV-2 inactivation is effective under any light/dark conditions. The presence of AgNPs has an important key to limit the survival of SARS-CoV-2 in the dark; moreover, there is a synergistic action when TiO2 is decorated with Ag to enhance the virus photocatalytic inactivation even under LED. The radical oxidation was confirmed as the the central mechanism behind SARS-CoV-2 damage/inactivation by ESR analysis under LED light. Therefore, photoactive AgNPs@TiO2 ceramic tiles could be exploited to fight surface infections, especially during viral severe pandemics

Bioelectrochemical recovery of silver from wastewater with sustainable power generation and its reuse for biofouling mitigation

Precious metals recovery and wastewater treatment using the microbial fuel cell (MFC) is an attractive approach for a sustainable environment. Silver recovery from wastewater and its valorization in the form of silver nanoflakes (AgNFs) brings back waste material to production stream and helps in transition from linear to circular economy. In the present study, bioelectrochemical performance of MFC fed with silver laden artificial wastewater (MFC-Ag) was compared with MFC fed with potassium ferricyanide (MFC-FC) and MFC fed with phosphate buffer as catholyte (MFC-blank). High silver removal (83 ± 0.7%) and recovery (67.8 ± 1%) efficiencies were achieved from MFC-Ag after 72 h operation. The maximum power density (3006 mW/m3) and current density (34100 mA/m3) of MFC-Ag were found to be significantly higher than the MFC-FC and MFC-blank. High chemical oxygen demand (COD) removal efficiency of MFC-Ag (82.7 ± 1.5%) compared with MFC-FC (76 ± 2) highlighted the suitability of silver laden wastewater as a cost effective catholyte. The high coulombic efficiency (8.73 ± 0.9 %) and low solution resistance (24.38 Ω) for MFC-Ag also indicate the potential of silver laden wastewater for large scale applications. Analytical characterizations of electrochemically recovered silver revealed the pure (99%) and crystalline AgNFs with a mean diameter of 18 ± 1.2 nm on the cathode surface. Furthermore, a significant anti-biofouling activity of recovered AgNFs indicate the valorization of waste by current study with potential applications in several industrial and environmental processes. Our method has diverse potential to scale up the MFC technology for industrial waste management as a closed loop process with minimum facilities and higher sustainability

Photoactive TiO2-montmorillonite composite for degradation of organic dyes in water

TiO2\u2013montmorillonite composite (TiO2\u2013M) was prepared by impregnation with TiCl4 followed by calcination at 350 C. The synthesized material was characterized by FTIR, TG\u2013DTA, BET, XRD and SEM\u2013 EDX. The results show that TiO2 was efficiently formed in Na\u2013montmorillonite (Na\u2013M) framework, and only a crystalline, pure anatase phase was produced. Photoactivity tests were carried out under UV-A irradiation using five selected organic dyes. The results indicate that the activity of TiO2\u2013M is more important for cationic dyes, where the removal rates are in the order: crystal violet (97.1%) > methylene blue (93.20%) > rhodamine B (79.8%) > methyl orange (36.1%) > Congo red (22.6%). The results of the TiO2\u2013 M activity were compared with that of the commercial P25. The comparison demonstrates that the synthesized TiO2\u2013M exhibits a higher adsorptive behavior and can be used as low-cost alternative to the commercial TiO2 for wastewater treatment, showing also an extreme easiness to completely recover the composite catalyst at the end of the test

Photocatalytic oxidation of pollutants in gas-phase via Ag3PO4-based semiconductor photocatalysts: Recent progress, new trends, and future perspectives

Air pollution has become a significant challenge for both developing and developed nations. due to its close association with numerous fatal diseases such as cancer, respiratory, heart attack, and brain stroke. Over recent years, heterogeneous semiconductor photocatalysis has emerged as an effective approach to air remediation due to the ease of scale-up, ready application in the field, use of solar light and ready availability of a number of different effective photocatalysts. To date, most work in this area has been conducted using UV-absorbing photocatalysts, such as TiO2 and ZnO; However, recent studies have revealed Ag3PO4 as an attractive, visible-light-absorbing alternative, with a bandgap of 2.43 eV. In particular, this material has been shown to be an excellent photocatalyst for the removal of many types of pollutants in the gas phase. However, the widespread application of Ag3PO4 is restricted due to its tendency to undergo photoanodic corrosion and the poor reducing power of its photogenerated conductance band electrons, which are unable to reduce O2 to superoxide •O2−. These limitations are critically evaluated in this review. In addition, recent studies on the modification of Ag3PO4 via combination with the conventional heterojunctions or Z-scheme junctions, as well as the photocatalytic mechanistic pathways for enhanced gas-pollutants removal, are summarized and discussed. Finally, an overview is given on the future developments that are required in order to overcome these challenges and so stimulate further research into this promising field

Photo-reduction of Hexavalent Chromium in Aqueous Solution in the Presence of TiO

The objective of this work is to determine the optimal conditions for the reduction of the hexavalent chromium in water using the photocatalytic system TiO2/ UV. The results show that the effectiveness of this system was significantly higher compared to direct photolysis. The influence of parameters such as photocatalyst loading and initial concentration of the substrate was studied. The study of the influence of pH shows that the reduction rates are grater for acid solutions. Furthermore the experimental results show that the presence of H2O2 at small concentration (10-6M) accelerates the reduction. However at higher concentration (10-4M) H2O2 inhibits the reduction. The presence of inorganic ions such as Cl- and SO42- does not seem to have any significant influence on the reduction rate of Cr (VI)