Ag doped α-Fe2O3 nanoparticles: Synthesis, characterization and application as heterogeneous photocatalyst for removal of organic dye from aqueous media without any oxidizing agents

Efficient photocatalytic methylene blue dye degradation from green-synthesized silver-doped iron oxide (Ag@Fe2O3) nanostructures

This study presents an environmentally friendly method for synthesizing Ag@Fe2O3 nanostructures through a hydrothermal technique that utilizes Saussurea obvallata leaf extract as a reducing and capping agent. The material was characterized using UV-Vis, FTIR, XRD, SEM-EDX, and TEM-SAED-line profile analysis. The UV-Vis shows a maximum absorbance peak at 380 nm, showing a band gap of 3.26 eV. FTIR analysis revealed several functional groups (vibrational modes), including 944 and 514 cm-1 (Fe-O) and 445 cm-1 (Ag-O). XRD spectra analysis confirmed the crystalline nature and, using the Scherrer equation, showed an average crystallite size of 49.57 nm. EDX confirmed the presence of only Ag, Fe, and O elements. SEM and TEM-SAED analyses revealed an echinus-like morphology with an interplanar spacing of 126 pm of the nanostructures. The photocatalytic activity of Ag@Fe2O3 was investigated through the degradation of methylene blue (MB) dye in the presence of UV-visible light irradiation. It was observed that 97.10% MB dye degradation occurred within 60 min, with the rate constant and half-life being 0.03025 min-1 and 22.90 min, respectively. It was deduced that the synergistic interaction of Ag with Fe2O3 promoted the separation of charge, significantly diminishing electron-hole recombination. This research presents plant extract as a readily available, cost-effective, and environmentally friendly way to produce highly efficient photocatalysts for degrading wastewater dye compounds.

Biosorbent silver nanoparticles decorated coffee-ground waste composite for cleaning water and antimicrobial applications

A sustainable biosorbent, silver nanoparticles-decorated coffee-ground waste (CWAg), was synthesized through a simple in-situ reduction method. CWAg is extensively characterized via SEM-EDX, PZC, FTIR, XRD, HR-TEM, and XPS analyses. The biosorbent was tested to remove chromium (Cr(VI)) and methylene blue (MB) from wastewater, and its antibacterial properties was evaluated. CWAg demonstrated efficient sorption efficiencies, achieving ⁓149.9 mg/g at 323 K and pH: 2.0 for Cr(VI) and ⁓113.4 mg/g at 293 K and pH: 6.0 for MB, at a biosorbent dose of 1 g/L. The equilibration times were 90 and 120 min for Cr(VI) and MB, with half-sorption times (tHST) of 9.2 and 13.9 min, respectively. The sorption mechanisms were successfully fitted with Sips isotherm and Pseudo-second-order models. Simultaneous sorption of MB and Cr(VI) at pH 2.0 exhibited antagonism, while a synergistic effect was observed at pH 6.0. Desorption and regeneration were achieved using NaOH and HCl solutions for Cr(VI) and MB, respectively. The efficiencies were just reduced by 9-13%. Finally, CWAg exhibited remarkable effectiveness for removing Cr(VI) from complex tannery effluent. Moreover, CWAg demonstrated positive antibacterial effects against both Gram-positive and Gram-negative bacteria, surpassing raw coffee-ground waste, underscoring the significant role of silver nanoparticles in enhancing bacterial inhibition.

Sunlight-driven photocatalytic degradation of industrial dyes using Withania somnifera decorated MnO2 nanoparticles

This study presents a unique, fast, and environmentally friendly approach for synthesizing MnO2 nanoparticles (MnO2 NPs) utilizing Withania somnifera (Ashwagandha) extract. The formation of nanoparticles was indicated by a color change from dark purple to dark brown within 10 min and validated through techniques including UV-Vis spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), and Energy Dispersive X-ray (EDX). Bromocresol green and Bromothymol blue were established as standards for assessing the photocatalytic efficiency of the synthesized nanoparticles. The synthesized nanocatalyst exhibited remarkable removal efficiency upon sunlight exposure, achieving 92% for Bromothymol blue and 95% for Bromocresol green within a duration of 1 h. The influence of variables including duration, photocatalyst dosage, and photodegradation kinetics was carefully examined to assess the efficacy of the created photocatalyst. The devised procedure is environmentally benign, facile to execute, and does not necessitate any chemical agents or advanced instrumentation for synthesis. This presents a new opportunity for the advancement of green photocatalysts, which may serve as an outstanding nanomaterial for wastewater clean-up.

Modification of nickel ferrite nanoparticles by sodium docusate surfactant for superior crystal violet dye removal from aqueous solutions

In this study, nickel ferrite (NiFe2O4) nanoparticles were synthesized using the Pechini sol-gel method and modified with sodium docusate surfactant. The modified nanoparticles showed an enhanced adsorption capacity of 384.62 mg/g for crystal violet dye, compared to 237.53 mg/g for unmodified NiFe2O4. Characterization was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) techniques. The adsorption process was spontaneous, exothermic, and followed the Langmuir isotherm and pseudo-second-order kinetic model. Optimal conditions for maximum dye removal were achieved at pH 10, 50 min, and 298 K. Additionally, the synthesized adsorbents demonstrated excellent regeneration and reusability over five adsorption-desorption cycles with minimal efficiency loss.