Enhanced the photocatalytic degradation of titanium dioxide nanoparticles synthesized by different plant extracts for wastewater treatment

Synthesis and performance evaluation of zinc oxide tubes/alginate microfibre composites for photodegradation of methylene blue: a novel reporting approach

This research investigates the efficacy of zinc oxide (ZnO) tubes in decontaminating polluted water using a substrate-free hydrothermal synthesis process for ZnO tubes. The synthesized tubes are impregnated into calcium alginate microfibres, strategically chosen for their high surface area to enhance photocatalytic degradation performance and for practical handling during decontamination and subsequent collection, thereby preventing secondary contamination. Structural and morphological analyses, conducted using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), thoroughly characterize the properties of the ZnO tubes and the composite material. The efficacy of this composite is demonstrated through the photocatalytic degradation of methylene blue (MB), as a representative organic pollutant, resulting in an 88% degradation of MB after 5 hours of irradiation by a sun simulator. Cyclic tests exhibit consistent degradation levels in the first four cycles (81-89%), followed by a subsequent decrease to 72% in the fifth cycle, coinciding with the breakdown of the microfibres into shorter fragments. Innovatively, this study introduces an approach to reporting photocatalytic degradation results, utilizing normalized pollutant concentration plotted against irradiated energy instead of time, as energy encompasses irradiated power, time, and surface area. This reveals that the 88% degradation of MB is achieved by irradiating the sample with an approximately 18 kJ. Additionally, a new metric, Specific Energy Efficiency (SEE), is introduced. It expresses the ratio of degraded pollutant mass to the mass of photocatalytic active material per unit of irradiated energy, with the maximum and cumulative SEE in this study being 1.044 μg g-1 J-1 and 326 ng g-1 J-1, respectively. This research not only contributes to the understanding of ZnO tubes' efficiency in polluted water decontamination but also introduces valuable insights for standardized reporting in photocatalytic degradation studies.

Low-cost photocatalytic membrane modified with green heterojunction TiO2/ZnO nanoparticles prepared from waste

The combination of photocatalysis and membrane procedures represents a promising approach for water treatment. This study utilized green synthesis methods to produce TiO2 nanoparticles (NPs) using Pomegranate extract and ZnO nanoparticles using Tangerine extract. These nanoparticles were then incorporated into a polyvinyl chloride (PVC) nanocomposite photocatalytic membrane. Different devices were used to examine the properties of nanocomposite membranes. The prepared membranes' morphology was examined using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The hydrophilicity of the membrane surface was assessed through the measurement of contact angle, while the crystal structure and chemical bonding were analyzed using Raman and Fourier transform infrared spectroscopy (FT-IR). The study also encompassed an examination of the mechanical properties. The hydrophilicity of the modified membrane exhibited a significant improvement. Additionally, there was an observed increase in both the pure water flux and rejection values. The photocatalytic activity of the membrane was found to be enhanced when exposed to sunlight as compared to when kept in the dark. The TiO2/ZnO nanocomposites membrane exhibited the highest level of photocatalytic degradation, achieving a rejection rate of 98.7% compared to the unmodified membrane. Therefore, it was determined that the TiO2/ZnO nanocomposites membrane exhibited superior performance to the other membranes assessed. The potential utility of our research lies in its application within the water treatment industry, specifically as an effective technique for modifying PVC membranes.

Exploring the Paradigm of Phyto-Nanofabricated Metal Oxide Nanoparticles: Recent Advancements, Applications, and Challenges

The development of nanotechnology, in particular metal oxide nanoparticles, has captured immense scientific attention in the global arena due to their unique properties leading to their unique diverse applications. But the use of toxic precursors and high operational cost make existing methodologies inefficient for synthesising metal oxide nanoparticles (MONPs). Biogenic synthesis of MONPs has been hailed as a more sustainable approach for the synthesis of NPs due to its alignment with the principles of green chemistry. Microorganisms (bacteria, yeast, algae), animal sources (silk, fur, etc.), and plants are effective, low-cost, and eco-friendly means of synthesizing MONPs since they possess a high bio-reduction abilities to produce NPs of various shapes and sizes. The current review encompasses recent advancements in the field of plant-mediated MONP synthesis and characterisation. The detailed evaluation of various synthesis processes and parameters, key influencing factors affecting the synthesis efficiency and product morphology, practical applications with insight into the associated limitations and challenges presents a valuable database that will be helpful in developing alternative prospects and potential engineering applications.

Efficient photocatalytic degradation of organic pollutants over TiO2 nanoparticles modified with nitrogen and MoS2 under visible light irradiation

Investigate the use of visible light to improve photocatalytic degradation of organic pollutants in wastewater. Nitrogen-doped titania and molybdenum sulfide nanocomposites (NTM NCs) with different weight ratios of MoS₂ (1, 2, and 3 wt.%) synthesized by a solid state method applied to the photodegradation of methylene blue(MB) under visible light irradiation. The synthesized NTM composites were characterized by SEM, TEM, XRD, FT-IR, UV-Vis, DRS and PL spectroscopy. The results showed enhanced activity of NTM hybrid nanocrystals in oxidizing MB in water under visible light irradiation compared to pure TiO₂. The photocatalytic performance of NTM samples increased with MoS₂ content. The results show that the photodegradation efficiency of the TiO₂ compound improved from 13 to 82% in the presence of N-TiO₂ and to 99% in the presence of MoS₂ containing N-TiO₂, which is 7.61 times higher than that of TiO₂. Optical characterization results show enhanced nanocomposite absorption in the visible region with long lifetimes between e/h+ at optimal N-TiO₂/MoS₂ (NTM₂) ratio. Reusable experiments indicated that the prepared NTM NCs photocatalysts were stable during MB photodegradation and had practical applications for environmental remediation.

Novel morphological mono-metallic substituted polyoxometalate immobilized 3-(aminopropyl)-imidazole photocatalysts for visible-light driven degradation: Anti-bacterial activity, membrane bacterial activity applications

A novel keggin-type tetra-metalates substituted polyoxometalate was functionalized by 3-(aminopropyl)-imidazole (3-API) supporting a ligand substitution method. In this paper, polyoxometalate (POMs) (NH₄)₃ [PMo₁₂O₄₀] and transition metal substituted of (NH₄)₃ [{PM^IVMo₁₁O₄₀}.(H₂O)] (M = Mn, V) are used as one of the adsorbents. The 3-API/POMs hybrid have been synthesized and used as adsorbent for the photo-catalysis of azo-dye molecule degradation after visible-light illumination as a simulated organic contaminant in water. The transition metal (M = M^IV, V^IV) substituted keggin-type anions (MPOMs) were synthesized, which reveals the degradation of methyl orange (MO) of about 94.0 % and 88.6 %. Immobilizing high redox ability POMs as an efficient acceptor of photo generated electron, on metal 3-API. In the presence of visible light irradiation result reveals that 3-API/POMs (89.9 %) have incredibly achieved after certain irradiation time and at specific conditions (3)-API/POMs; photo-catalysts dose = 5mg/100 ml, pH = 3 and MO dye concentration = 5 ppm). As the surface of POM catalyst has strong absorption of azo-dye MO molecule engaged as a molecular exploration through photo catalytic reactant. From the SEM images it is clear that the synthesized POMs based materials and POMs conjugated MO have varieties of morphological changes observed such as flakes, rods and spherical like structures. Anti-bacterial study reveals that the process of targeted microorganism occur higher activity against pathogenic bacterium for 180 min of visible-light irradiation is measured in terms of zone of the inhibition. Furthermore, the photo catalytic degradation mechanism of MO using POM, metaled POMs and 3-API/POMs also has been discussed.

Fabrication and characterization of magnetic nanomaterials for the removal of toxic pollutants from water environment: A review

The success of any sustainable growth represents an advancement of novel approaches and new methodologies for managing any ecological concern. Magnetic nanoparticles have gained recent interest owing to their versatile properties such as controlled size, shape, quantum and surface effect, etc, and outcome in wastewater treatment and pollutant removal. Developments have progressed in synthesizing magnetic nanoparticles with the required size, shape and morphology, surface and chemical composition. Magnetic nanoparticles are target specific and inexpensive compared to conventional treatment techniques. This review insight into the synthesis of magnetic nanoparticles using physical, chemical, and biological methods. The biological method of synthesizing magnetic nanoparticles serves to be cost-effective, green process, and eco-friendly for various applications. Characterization studies of synthesized nanoparticles using TEM, XRD, SARS, SANS, DLS, etc are discussed in detail. Magnetic nanoparticles are widely utilized in recent research for removing organic and inorganic contaminants. It was found that the magnetic nanosorption approach together with redox reactions proves to be an effective and flexible mechanism for the removal of pollutants from waste effluents.

Sustainable approaches towards green synthesis of TiO2 nanomaterials and their applications in photo-catalysis mediated sensingtomonitor environmental pollutions

Nanomaterials are gaining enormous interests owing to their novel applications that have been explored nearly in every field of our contemporary society. In this scenario, preparations of nanomaterials following green routes have attracted widespread attention in terms of sustainable, reliable and environmentally friendly practice to produce diverse nanostructures. In this review, we summarized the fundamental processes and mechanisms of green synthesis approaches of TiO₂ NPs. We explore the role of plants and microbes as natural bioresources to prepare TiO₂ NPs. Particularly, focused have been made to explore the potential of TiO₂ based nanomaterials to design variety of sensing platforms by exploiting the photo-catalysis efficiency under the influence of light source. Such types of sensing can of massive importance to monitor the environmental pollutions and thereby to invent advanced strategies to remediate hazardous pollutants to offer clean environment.

In vitro toxicological assessment and biosensing potential of bioinspired chitosan nanoparticles, selenium nanoparticles, chitosan/selenium nanocomposites, silver nanoparticles and chitosan/silver nanocomposites

Hydrogen peroxide (H₂O₂) is widely used in various industries and biological fields. H₂O₂ rapidly contaminants with water resources and hence simple detection process is highly wanted in various fields. The present study was focused on the biosensing, antimicrobial and embryotoxicity of bioinspired chitosan nanoparticles (Cs NPs), selenium nanoparticles (Se NPs), chitosan/selenium nanocomposites (Cs/Se NCs), silver nanoparticles (Ag NPs) and chitosan/silver nanocomposites (Cs/Ag NCs) synthesized using the aqueous Cucurbita pepo Linn. leaves extract. The physico-chemical properties of as-synthesized nanomaterials were confirmed by various spectroscopic and microscopic techniques. Further, hydrogen peroxide (H₂O₂) sensing properties and their sensitivities were confirmed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) methods, in which Cs/Ag NCs showed pronounced sensing properties. In addition, the mode of antibacterial interaction results clearly demonstrated the effective inhibitory activity of as-prepared Ag NPs and Cs/Ag NCs against Gram negative pathogenic bacteria. The highest embryotoxicity was recorded at 0.19 μg/ml of Ag NPs and 1.56 μg/ml of Se NPs. Intriguingly, the embryo treated with Cs/Se NCs and Cs/Ag NCs significantly reduced the toxicity in the presence of Cs matrix. However, Cs/Se NCs did not show good response in H₂O₂ sensing than the Cs/Ag NCs, implying the biocompatibility of Cs/Ag NCs. Overall, the obtained results clearly suggest that Cs/Ag NCs could be suitable for dual applications such as for the detection of environmental pollutant biosensors and for biomedical research.

A type II heterojunction α-Fe2O3/g-C3N4 for the heterogeneous photo-Fenton degradation of phenol

The heterogeneous photo-Fenton reaction is an effective method of chemical oxidation to remove phenol in wastewater with environmental friendliness and sustainability. Herein, the composite α-Fe₂O₃/g-C₃N₄, as a catalyst of the heterogeneous photo-Fenton reaction, has been synthesized by hydrothermal-calcination method using the abundant and low-cost FeCl₃·6H₂O and g-C₃N₄ as raw materials. The influence of the annealing temperature during calcination was also investigated. The UV-Vis diffuse reflectance spectra of samples show that the composite α-Fe₂O₃/g-C₃N₄ possesses the widest light response range. Furthermore, the transient photocurrent response curves demonstrated the strongest intensity of α-Fe₂O₃/g-C₃N₄. The annealed α-Fe₂O₃/g-C₃N₄ is indicative of the highest degradation efficiency in all samples due to the improvement of the charge transfer ability caused by the tight heterojunction structure. The results of the scavenger trapping experiments show that the hydroxyl radical was the main active species in degradation. Based on experimental results, a type II heterojunction should be built in the composite α-Fe₂O₃/g-C₃N₄, driving the photoelectrons transfer and migration by internal electronic field. This work provides a facile and new method to synthesize α-Fe₂O₃/g-C₃N₄ as an effective heterogeneous photo-Fenton catalyst for environmental remediation.

Composite α-Fe₂O₃/g-C₃N₄ with type II heterojunction to degrade phenol by heterogeneous photo-Fenton reaction.

Fabrication of a zinc oxide/alginate (ZnO/Alg) bionanocomposite for enhanced dye degradation and its optimization study

This paper studies a new response surface methodology (RSM) based on the central composite design (CCD) modeling method to optimize the photocatalytic degradation of methylene blue (MB) and methyl orange (MO) by using a synthesized ZnO/Alg bionanocomposite under UV irradiation. ZnO with different content of sodium alginate (Alg) (10, 20, and 30% by weight) has been synthesized by a one-step sol–gel method. Zinc oxide (ZnO) nanoparticles were impregnated on the alginate polymer. Various characterization techniques were used to describe the physical and chemical properties of each catalyst such as XRD, FTIR, UV-vis, PL, FESEM, Raman, and BET. The optimal catalyst for MB and MO photocatalytic degradation process was discussed mathematically as a function of catalyst dose, irradiation time, and MB and MO concentration, which was modeled by CCD-RSM based on a statistical model (quadratic regression) and an optimization process (ANOVA analysis). The photocatalytic degradation efficiency of 98% was achieved for the optimal conditions of a dye concentration of 20 mg L⁻¹, the catalyst dose of 0.34 g L⁻¹, and an irradiation time of 90 min at pH 6. The measurement result (R² = 0.9901) showed that the considered model is very suitable, and the selected CCD-RSM successfully optimized the photodegradation conditions of MB and MO.

Here, we reported the synthesis of ZnO/Alg bionanocomposite and analyzed photocatalytic degradation efficiency for MB and MO dyes under UV light. We also performed optimization studies using the RSM-CCD method and obtained 98% degradation efficiency.