INDIGO BLUE DEGRADATION: PROBABLE PRESENCE OF DYE ADSORBED BY IRON HYDROXIDE DURING FENTON PROCESS

A chemical method using FeSO4 and H2O2 was selected for indigo blue (IB) degradation in aqueous medium. The initial experiments demonstrated that high concentrations of hydrogen peroxide (H2O2) and iron sulfate heptahydrate (FeSO4.7H2O) were capable of total degradation of IB (approximately 100%). Controlled tests, varying the concentrations of both reagents, revealed that the mixture containing approximately 350 mg/L (v/v) of FeSO4.7H2O and 0.57% (v/v) of H2O2wasconsiderablyefficient in the degradation of IB (1,000 mg/L). The decay kinetics revealed rapid IB degradation and possible IB adsorption on iron (III) hydroxide precipitate [Fe(OH)3]↓. However, the adsorbed IB also subsequently, leaves the residue of [Fe(OH)3]↓, which suggests the occurrence of not only chemical degradation of IB but also its possible adsorption by Fe(OH)3 precipitate.