An inhibitory effect of self-assembled soft systems on Fenton driven degradation of xanthene dye Rhodamine B

• Presence of surfactants in wastewaters influences the Fenton driven decay of RhB.
• Cationic surfactants retard the decay of RhB more than non-ionic surfactants.
• SDS inhibits the decay process completely.
• Mixed micelles exhibit intermediate effect on decay kinetics of RhB.

Rhodamine B (RhB) is known to be a common organic pollutant despite having various technical applications. Treatment of effluents containing such compounds is important so as to minimize their effect on environment. Advanced Oxidation Processes (Fenton and Fenton like reactions) are such methods that can oxidize the contaminants powerfully and non-selectively. This work investigates the oxidation kinetics of dye RhB by hydroxyl radical (OH) generated via Fenton reaction in presence of surfactant assemblies of varying architectures using spectrophotometric, spectrofluorometic and tensiometric methods. The presence of surfactants viz. cationics, non-ionics and some binary mixtures in the pre-micellar and post micellar concentration ranges were found to inhibit the degradation of RhB to a varying degree. However, the reaction was totally inhibited in anionic surfactant. The experimental data was fitted to a pseudo first order kinetic model and the kinetic parameters obtained thereof were explained on the basis of the nature and type of interaction between the cationic form of RhB and the surfactants of varying architectures. The work has a critical significance in view of the fact that degradation studied in presence of surfactant assemblies is more representative than studied in aqueous solution because such conditions compare well with the conditions prevailing in the environment.