Mechanisms of radical generation in the removal of phenol derivatives and pigments using different Fe-based catalytic systems

IVANA MAGARIO; F.S. GARCIA EINSCHLAG; E.H. RUEDA; JULIO A. ZYGADLO; M. L FERREIRA

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 352 p. 1 - 20

1381-1169

a b s t r a c tPhenolic compounds removal is a very active research field due to occurrence and the toxicity of phenolicpollutants in industrial wastewaters. In order to make an a priori selection of the most efficient removalprocess for a target structure this contribution reviews and compares some of the mechanistic aspectsof the oxidation in the presence of hydrogen peroxide and catalyzed by complexed iron which is thein-common element in Fenton systems, plant peroxidases and biomimetics. Different substrates wereconsidered from the most basic phenol molecule to complex structures such as phenolic dyes and lignins.The reactivity of iron is related to its microenvironment generated by ligands and their electron withdrawingcapacity thus conditioning the type of cleavage induced on hydrogen peroxide and the oxidationstate change on iron upon reaction. The relative concentrations of organic to inorganic free radicals generatedcontrol the main catalytic action; i.e. from degradation up to mineralization in Fenton systems oroligomerization up to polymerization in plant peroxidases systems. Moreover, some reaction conditionsas the peroxide concentration, the initial molar ratio of organic compounds to peroxide and the type ofreaction solvent are identified as key factors to promote a desired action mechanism by peroxidases (andtheir biomimetics).