Probing the interaction effects of metal ions in Mn x Fe(3-x)O4 on arsenite oxidation and adsorption

Optimization studies of BTX removal by magnetite coated oleic acid obtained from microwave-assisted synthesis using response surface methodology

Benzene, toluene and xylene (BTX) are volatile organic compounds released into the environment, that require urgent removal to avoid adverse health effects. In this work, the modelling and optimization of the preparation factors for magnetite coated oleic acid (MNP-OA) composite from microwave synthesis using response surface methodology were conducted to maximize BTX removal, and iron content. The influence of five crucial preparation variables: the Fe^3+/Fe²⁺ solution volumes, microwave power, volume of ammonia water (VAW), reaction time and volume of oleic acid (VOA) on the iron content (% Fe), and BTX adsorption capacity were investigated. The analysis of variance results revealed that VOA and VAW were the most influential factors for high % Fe content, and improved BTX removal. The % Fe, and BTX adsorption capacity for MNP-OA composite at optimized experimental conditions were estimated to be 85.57%, 90.02 mg/g (benzene), 90.07 mg/g (toluene), and 96.31 mg/g (xylene).

Optimizing Cr(VI) adsorption parameters on magnetite (Fe3O4) and manganese doped magnetite (MnxFe(3-x)O4) nanoparticles

Magnetite as an adsorbent is efficient since iron oxides have high affinities for heavy metal pollutants and are environmentally friendly. Manganese oxides provide catalytic properties which are desirable during the remediation of multi valent pollutants. Magnetite (Fe3O4) and manganese doped magnetite (MnxFe(3-x)O4) nanoparticles were synthesized and characterized to determine the manganese doping effects on magnetite’s crystal and surface properties. Fe3O4 and MnxFe(3-x)O4 showed similarities in crystal morphology indicating that manganese doping did not alter the nature of Fe3O4 nanoparticles. Manganese doping improved magnetite’s thermal properties as well as its surface area providing improved adsorption characteristics. The as-synthesized particles were applied in the optimization of hexavalent chromium adsorption. Adsorption proceeded under similar conditions for both adsorbents indicating their structural similarities. Higher efficiencies were observed on the doped adsorbent due to increased surface area and the presence of additional functional groups. Solution pH significantly affected the adsorption process aiding in the reduction of Cr(VI) ions to the less toxic Cr(III) species. The adsorption distribution coefficient KD indicated that manganese doping significantly improved magnetite’s affinity for hexavalent chromium. Adsorption and reduction were determined to responsible for pollutant reduction in solution at optimal conditions of pH 2, 5 g/L and 100 mg/L for adsorbent mass and solution concentration.