Green synthesis of akaganéite (β-FeOOH) nanocomposites as peroxidase-mimics and application for discoloration of methylene blue

Nanosorbent based on coprecipitation of ZnO in goethite for competitive sorption of Cd(II)-Pb(II) and Cd(II)-Pb(II)-Ni(II) systems

Amongst the various water pollutants, heavy metal ions require special attention because of their toxic nature and effects on humans and the environment. Preserving natural resources will have positive impacts on living conditions by reducing diseases and water treatment by nanotechnology is effective in solving this problem owing to the properties of nanomaterials. In this study, a goethite nanoparticle was prepared by hydrothermal method, while ZnO/goethite nanocomposite by co-precipitation was developed. The nanoparticles were characterized using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transform Electron Microscopy (TEM), Thermogravimetric Differential Thermal Analysis (TGA-DTA), Dynamic Light Scattering (DLS), and Breunner-Emmet-Teller (BET) surface area analysis. The adsorption of Cd(II)-Pb(II) and Cd(II)-Pb(II)-Ni(II) ions systems on ZnO/goethite nanocomposite was investigated in a batch mode. The findings of the study showed that nanoparticles ZnO/goethite composite were mixed of spherical and rod-like shapes. The BET results revealed average particle sizes of 41.11 nm for nanoparticles for ZnO/goethite while TGA/DTA confirmed the stability of the adsorbents. The optimum adsorption capacities of the nanocomposite for Pb(II), Cd(II), and Ni(II) ions from the Pb-Cd-Ni ternary system were 415.5, 195.3, and 87.13 mg g-1, respectively. The adsorption isotherm data fitted well with the Langmuir isotherm model. The study concluded that the nanoparticle adsorbents are efficient for the remediation of toxic pollutants and are, therefore, recommended for wastewater treatment.

Cell-shape assemblage and nanostructure of akaganéite bioformed in FeCl2 solutions

Akaganéite (β-FeOOH) with a tunnel structure typically occupied by chloride can undergo anion-exchange reactions in aqueous solutions for pollutant removal. In this work, we studied bioformation of akaganéite in FeCl₂ solutions with Acidithiobacillus ferrooxidans cells at pH 2.9, during 36-h incubation. The obtained products were analyzed and characterized by XRD, FTIR, EDS, FETEM, and HRTEM. Results showed that in acidic media with pH 2.9, the cells facilitated ferrous biooxidation and ferric precipitation. The resulting ferric precipitates were identified as polycrystalline akaganéite powders and had a morphology of nanospindles with a length of less 100 nm. The correlatively chemical formula for akaganéite collected at 1 h was reckoned as Fe₈O₈(OH)_6.71(Cl)_1.29 with 6.6% Cl. It was observed that ferric precipitates along exterior structures of cells or their extruded organic polymers grew and assembled into cellular shape. The evolved cell-shape akaganéite assemblages were twice of cells (about 2 µm) in size. These results could contribute to understanding of laboratorial bioformation of akaganéite and its biomineralization in acidic environments and promoting its practical applications.