Oxidation of p-hydroxybenzoic acid by Fenton's reagent.
Fenton's reagent has been shown to be a feasible technique to treat phenolic-type compounds present in a variety of food processing industry wastewaters. A model compound, p-hydroxybenzoic acid was oxidised by continuously pumping two solutions of ferrous iron and hydrogen peroxide. Typical operating variables like reagent feeding concentrations and flowrate, temperature and pH were studied. A mechanism of reactions based on the classical Fenton's chemistry was assumed, and computed concentration profiles of the parent compound, ferrous ion and dihydroxybenzene were compared to experimental results. The model qualitatively predicted the influence of several operating variables, however, calculated results suggested the presence of parallel routes of substrate elimination and/or a initiating rate constant with a higher value. The low efficiency of a well-known hydroxyl radical scavenger (tert-butyl alcohol) also supports the contribution of oxidising species different from the hydroxyl radical to substrate removal. Further evidence of the presence of reactions different from the hydroxyl radical oxidation was observed from comparison of the simultaneous Fenton's or UV/H2O2 oxidations of p-hydroxybenzoic acid, tyrosol and p-coumaric acid.
Departamento de Ingenieria Quimica y Energética, Universidad de Extremadura, Avenida de Elvas S/N, 06071 Badajoz, Spain. fjrivas@unex.es
F J
FJ
Rivas
F J
FJ
Beltrán
J
J
Frades
P
P
Buxeda
D002851:Chromatography, High Pressure Liquid; D003373:Coumaric Acids / Q000737:chemistry; D005525:Food-Processing Industry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D010226:Parabens / Q000737:chemistry*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000737:chemistry; D011422:Propionates; D013885:Thiosulfates / Q000737:chemistry; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000379:methods; D020002:tert-Butyl Alcohol / Q000737:chemistry
D003373:Coumaric Acids; C045076:Fenton's reagent; D007220:Industrial Waste; D010226:Parabens; D011422:Propionates; D013885:Thiosulfates; D014874:Water Pollutants, Chemical; C011867:4-hydroxyphenylethanol; D006861:Hydrogen Peroxide; D007501:Iron; C017717:sodium thiosulfate; C495469:p-coumaric acid; C038193:4-hydroxybenzoic acid; D020002:tert-Butyl Alcohol; D010626:Phenylethyl Alcohol