Glucose-assisted ball milling preparation of silver-doped biphasic TiO2 for efficient photodegradation of Rhodamine B: Effect of silver-dopant loading

Synthesis and preliminary evaluation of Ag-TiO2/CNT hybrid nanocomposite for the degradation of polystyrene microplastics under solar irradiation

Currently, microplastics (MPs) are considered as emerging aqueous pollutants. However, existing methods for the separation and treatment of MPs from an aquatic environment are limited by their low efficiency. Advanced oxidation processes (AOPs) are novel techniques that employ photo-induced electron/hole pairs to generate active radicals for MP mineralization. Thus, in this study, a photocatalyst, i.e., Ag+ ion-doped TiO2, heterojunctioned with carbon nanotubes (CNT), was synthesized to study the degradation of typical MPs such as polystyrene (PS) under solar irradiation. Effectiveness of the prepared photocatalyst for the PS degradation was estimated through FESEM, FTIR, total organic carbon (TOC) analyzer, and gas chromatography-mass spectroscopy (GC-MS). Quantitatively, 31.7% degradation of PS microbeads was achieved within 48 h. Therefore, this study provides an efficient and cost-effective strategy for the degradation of MPs from the aqueous medium.

Semiconductors Application Forms and Doping Benefits to Wastewater Treatment: A Comparison of TiO2, WO3, and g-C3N4

Photocatalysis has been vastly applied for the removal of contaminants of emerging concern (CECs) and other micropollutants, with the aim of future water reclamation. As a process based upon photon irradiation, materials that may be activated through natural light sources are highly pursued, to facilitate their application and reduce costs. TiO2 is a reference material, and it has been greatly optimized. However, in its typical configuration, it is known to be mainly active under ultraviolet radiation. Thus, multiple alternative visible light driven (VLD) materials have been intensively studied recently. WO3 and g-C3N4 are currently attractive VLD catalysts, with WO3 possessing similarities with TiO2 as a metal oxide, allowing correlations between the knowledge regarding the reference catalyst, and g-C3N4 having an interesting and distinct non-metallic polymeric structure with the benefit of easy production. In this review, recent developments towards CECs degradation in TiO2 based photocatalysis are discussed, as reference catalyst, alongside the selected alternative materials, WO3 and g-C3N4. The aim here is to evaluate the different techniques more commonly explored to enhance catalyst photo-activity, specifically doping with multiple elements and the formation of composite materials. Moreover, the possible combination of photocatalysis and ozonation is also explored, as a promising route to potentialize their individual efficiencies and overcome typical drawbacks.

Adsorption of persistent organic pollutants (POPs) from the aqueous environment by nano-adsorbents: A review

The intensification of urbanisation and industrial activities significantly exacerbates the distribution of toxic contaminations into the aqueous environment. Persistent organic pollutants (POPs) have received considerable attention in the past few decades because of their persistence, long-distance migration, potential bioaccumulation, latent toxicity for humans and wildlife. There is no doubt that POPs cause serious effects on the global ecosystem. Therefore, it is necessary to develop a simple, safe and sustainable approach to remove POPs from water bodies. Among other conventional techniques, the adsorption process has proven to be a more effective method for eliminating POPs and to a larger extent meet discharge regulations. Nanomaterials can effectively adsorb POPs from aqueous solutions. For most POPs, a >70% adsorptive removal efficiency was achieved. The major mechanisms for POPS uptake by nano-adsorbents includes electrostatic interaction, hydrophobic (van der Waals, π-π and electron donor-acceptor) interaction and hydrogen bonding. Nano-adsorbent can sustain a >90% POPs adsorptive removal for about 3 cycles and reuseable for up to 10 cycles. Challenges around adsorbent ecotoxicity and safe disposal were also discussed. The present review evaluated recent research outcomes on nanomaterials that are employed to remove POPs in water systems.

Photodegradation under UV Light Irradiation of Various Types and Systems of Organic Pollutants in the Presence of a Performant BiPO4 Photocatalyst

In this study, we prepared spheroid microstructures of monoclinic bismuth phosphate BiPO4 by a facile solid-state reaction at 500 °C. The crystal structure was refined using the Rietveld method, where the crystal cell was resolved using a monoclinic system (parameters a, b, c, β) with space group P21/n. SEM images showed that the solid catalyst presented homogeneous morphologies. These BiPO4 microparticles (BiP-500) have been used as photocatalysts to photodegrade, under UV light irradiation, three cationic dyes (Rhodamine B, RhB; Methylene Blue, MB; and Toluidine Blue, TB), three anionic dyes (Congo Red, CR; Orange G, OG; and Methyl Orange, MO) and mixtures of RhB-MB, RhB-OG and MO-OG organic dyes. The photodegradation efficiency of these BiP-500 microparticles is found to be optimal in the case of RhB solutions, RhB-MB and RhB-OG binary mixtures. The BiP-500 catalyst shows a high selectivity for the conversion of the mixture of dyes into CO2 and H2O. Total organic carbon analysis of an anionic dye and a cationic dye (RhB, OG and RhB-MB) confirms the mineralization of the pollutants in the presence of BiP-500 particles. The photocatalytic efficiency of our BiP-500 photocatalyst has been confirmed, with a view to facilitate applications in the field of the depollution of wastewater in the agricultural environment by the degradation of parathion-methyl (PM) as a pollutant.

Ag Nanoparticles for Biomedical Applications-Synthesis and Characterization-A Review

Silver nanoparticles have been intensively studied over a long period of time because they exhibit antibacterial properties in infection treatments, wound healing, or drug delivery systems. The advantages that silver nanoparticles offer regarding the functionalization confer prolonged stability and make them suitable for biomedical applications. Apart from functionalization, silver nanoparticles exhibit various shapes and sizes depending on the conditions used through their fabrications and depending on their final purpose. This paper presents a review of silver nanoparticles with respect to synthesis procedures, including the polluting green synthesis. Currently, the most commonly used characterization techniques required for nanoparticles investigation in antibacterial treatments are described briefly, since silver nanoparticles possess differences in their structure or morphology.

Phase Transformation, Photocatalytic and Photoluminescent Properties of BiPO4 Catalysts Prepared by Solid-State Reaction: Degradation of Rhodamine B

Polycrystalline bismuth phosphate BiPO4 was synthesized by solid-state reaction at different temperatures varying from 500 to 900 °C. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and Raman spectroscopy. The low-temperature phase of BiPO4 has monoclinic structure with a space group P21/n, and was transformed into the monoclinic phase P21/m with a slight distortion of monoclinic lattice when it was heated above 500 °C. The effect of the transformation on the structure, morphology and photocatalytic properties was examined. The photocatalytic activity of each sample, in presence of Rhodamine B (RhB) in aqueous solution, was carried out and analyzed under UV light irradiation. Photoexperiments showed that the material prepared at 500 °C is the best catalyst with degradation efficiency of the order of 96% after 12 min of reaction time under UV light irradiation. This high photocatalytic efficiency could be due to their structural and morphological changes. The photocatalytic degradation mechanism of RhB in the presence of the best photocatalyst BiP-500 °C is proposed. The stability of the catalyst was also examined by carrying out four successive tests of the degradation in the presence of BiP-500 °C. Total organic carbon (TOC) was used to further estimate the rate of mineralization in the presence of BiP-500 °C (83% TOC removal). Photoluminescence experiments performed under UV-laser light irradiation revealed emissions in the green-orange range, with optimal intensities for the mix systems observed at 550 °C.