MULTI-METAL-SUBSTITUTED-GOETHITE AS AN EFFECTIVE CATALYST FOR OXIDATION OF AZO DYE WASTEWATER

A. S. DIEZ; M. ALVAREZ; S. SCHLICHTER; M. DENNEHY; M. C. ZENOBI

CLEAN-SOIL AIR WATER

WILEY-V C H VERLAG GMBH

Lugar: Weinheim; Año: 2016 vol. 44 p. 1652 - 1660

1863-0650

Different samples of goethite modified with cobalt, manganese or aluminum were synthesized andcharacterized by means of X-ray diffraction, chemical analysis, scanning electron microscopy, zetapotential measurements and N2 adsorption?desorption isotherm analysis. The goethite oxides were testedas efficient catalysts for the degradation of methyl orange (MO, sodium 4-[(4-dimethylamino)phenylazo]benzenesulfonate), a sulfonated azo dye indicator, employing potassiumpersulfate (PS) in water, at pH 3. The Mn, Co and Al substitution in goethite gave rise to active sites forPS activation. The most effective catalyst reached 93 % of degradation at 120 min of reaction. Theincrease of temperature led to an expected conversion enhancement, and kinetic parameters werecalculated for one of the evaluated catalysts. MO degradation curves best fitted to pseudo-second orderkinetics. The extent of mineralization, measured as total removed organic carbon (TOC), was alsomonitored. A significant degree of mineralization was achieved and confirmed by TOC analysis. Amechanism for MO oxidation with SO4?− radicals was discarded and a pathway involvingperoxymonosulfate species was proposed. The results indicate that the goethite-substituted oxides areeffective catalysts for the studied azo dye degradation in aqueous solution.