ABSTRACT
Manganese ferrite nanopowder was prepared by thermal decomposition at 400°C of the gel synthesized from manganese and iron nitrates and polyvinyl alcohol. X-ray diffractometry evidenced that manganese ferrite was formed as single crystalline phase at this temperature. Scanning electron microscope images evidenced the formation of very fine spherical particles (d<11nm) of manganese ferrite, with specific surface area of 147m2/g. The powder obtained at 400°C was used as a catalyst for the oxidative degradation of phenol in aqueous solutions, in the presence of potassium peroxydisulfate as oxidant. High phenol removal efficiencies above 90% were reached at: pH 3-3.5, phenol initial concentration around 50mg/L, peroxydisulfate:phenol mass ratio 10:1, and catalyst dose 3g/L. Total organic carbon measurements showed that the degradation of phenol goes, under these conditions, to mineralization in an extent of 60%.
Subject(s)
Ferric Compounds/chemistry , Manganese Compounds/chemistry , Nanoparticles/chemistry , Phenol/chemistry , Water Pollutants, Chemical/chemistry , Catalysis , Oxidation-Reduction , Sulfates/chemistry , Water Purification/methodsABSTRACT
Hybrid inorganic-organic materials, silica - diol, were prepared by the sol-gel process from mixtures of tetraethyl orthosilicate (TEOS) and two diols (1,2-propanediol and 1,4-butanediol), using different molar ratios TEOS: diol, in acidic catalysis. The resulted materials were studied by thermal analysis, FT-IR spectroscopy, 29Si-NMR and nitrogen adsorption measurements. The thermal analysis of the gels, in air and nitrogen, has clearly evidenced the chemical bonding of the studied diols with the Si-OH groups resulting from the hydrolysis of TEOS, forming hybrid gels. The mass loss registered on TG in the range 250-300 °C, corresponding to the burning of the organic chains from the hybrid network allowed us to calculate the fraction of the bonded diol. This fraction depends on the initial molar ratio TEOS:diol and on the diol's nature. By annealing the hybrid gels at 600 °C we have obtained silica matrices with different textural parameters.
