Photocatalytic degradation of methyl red using seaweed mediated zinc oxide nanoparticles

Recent advancements in sustainable synthesis of zinc oxide nanoparticles using various plant extracts for environmental remediation

The sustainable synthesis of zinc oxide nanoparticles (ZnO-NPs) using plant extracts has gained significant attention in recent years due to its eco-friendly nature and potential applications in numerous fields. This synthetic approach reduces the reliance on non-renewable resources and eliminates the need for hazardous chemicals, minimizing environmental pollution and human health risks. These ZnO-NPs can be used in environmental remediation applications, such as wastewater treatment or soil remediation, effectively removing pollutants and improving overall ecosystem health. These NPs possess a high surface area and band gap of 3.2 eV, can produce both OH° (hydroxide) and O2-° (superoxide) radicals for the generation of holes (h+) and electrons (e-), resulting in oxidation and reduction of the pollutants in their valence band (VB) and conduction band (CB) resulting in degradation of dyes (95-100% degradation of MB, MO, and RhB dyes), reduction and removal of heavy metal ions (Cu2+, Pb2+, Cr6+, etc.), degradation of pharmaceutical compounds (paracetamol, urea, fluoroquinolone (ciprofloxacin)) using photocatalysis. Here, we review an overview of various plant extracts used for the green synthesis of ZnO NPs and their potential applications in environmental remediation including photocatalysis, adsorption, and heavy metal remediation. This review summarizes the most recent studies and further research perspectives to explore their applications in various fields.

Efficient photodegradation of methyl red dye by kaolin clay supported zinc oxide nanoparticles with their antibacterial and antioxidant activities

Kaolin clay-supported Zinc oxide (ZnO/KC) and ZnO NPs nanoparticles (NPs) were prepared by a chemical reduction process and used for the photodegradation of methyl red (MR) dye as a photocatalyst. Due to the interlayered porous structure of the KC, we achieved an extremely good association between ZnO NPs and KC. The product confirmation was conducted by Scanning electron microscopy (SEM), X-Ray diffraction (XRD), energy dispersive X-Ray (EDX), and Fourier transforms infrared (FTIR). SEM showed the irregular morphology of ZnO NPs, while ZnO/KC NCs were predominately round-shaped. Moreover, in both cases, NPs were present in both dispersed as well as agglomerated forms with an average particle size below 100 nm. The results acquired from photodegradation analyses show that ZnO NPs and ZnO/KC NCs degraded about 90 and 99% of MR dye respectively, under UV light in a short irradiation time of 10 min. The recovered and re-recovered ZnO NPs and ZnO/KC NCs also considerably photodegraded MR dye in an aqueous medium. The same NPs also exhibit promising bioactivities against two pathogenic bacteria, i.e., Citrobacter and Providencia. The antioxidant activity of ZnO/KC NCs reached to reasonable 70% compared to the 88% activity of the standard ascorbic acid.

Green synthesis of ZnFe2O4@ZnO nanocomposites using Chrysanthemum spp. floral waste for photocatalytic dye degradation

The occurrence of textile dyeing wastewater discharged into the environment has been recently increasing, resulting in harmful effects on living organisms and human health. The use of green nanoparticles for water decontamination has received much attention. Floral waste can be extracted with the release of natural compounds, which act as reducing and stabilizing agents during the biosynthesis of nanoparticles. Herein, we report the utilization of Chrysanthemum spp. floral waste extract to synthesize green ZnFe₂O₄@ZnO (ZFOZx) nanocomposites for the photocatalytic degradation of Congo red under solar light irradiation. The various molar ratio of ZnFe₂O₄ (0-50%) was incorporated into ZnO nanoparticles. The surface area of green ZFOZx nanocomposites was found to increase (7.41-42.66 m² g^-1) while their band gap energy decreased from 1.98 eV to 1.92 eV. Moreover, the results exhibited the highest Congo red dye degradation efficiency of 94.85% at a concentration of 5.0 mg L^-1, and a catalyst dosage of 0.33 g L^-1. The ^•O₂^- reactive species played a vital role in the photocatalytic degradation of Congo red dye. Green ZFOZ3 nanocomposites had good recyclability with at least three cycles, and an excellent stability. The germination results showed that wastewater treated by ZFOZ3 was safe enough for bean seed germination. We expect that this work contributes significantly to developing novel green bio-based nanomaterials for environmental remediation as well as reducing the harm caused by flower wastes.

Isothermic and Kinetic Study on Removal of Methylene Blue Dye Using Anisomeles malabarica Silver Nanoparticles: An Efficient Adsorbent to Purify Dye-Contaminated Wastewater

Remediation of industrial discharged dyes to the water bodies is much needed in the current scenario. Here in this, we prepared silver nanoparticles using Anisomeles malabarica. The synthesized nanoparticles were characterized by Fourier transform infrared study, scanning electron microscopy, dynamic scanning calorimetry, and thermogravimetric analysis. All the characterization studies suggested that the formation of silver nanoparticles was successful. The synthesized silver nanoparticles were used as an adsorbent to adsorb the methylene blue. To achieve this, optimum pH of the adsorbent to adsorb the dye was studied, and it was found to be pH 7. The adsorbent dose to adsorb the dye was found to be 0.1 g/L. From the isotherm theoretical studies, it was found that the adsorption isotherm follows Langmuir adsorption, and the $q_{\max }$ was found to be 97.08. From the kinetic study, the rate of the reaction follows the pseudosecond-order kinetics with $\text{regression}>0.9$ . From the study, it was inferred the nanoparticles synthesized can act as a good adsorbent and can be used to purify the wastewater contaminated with methylene blue.