Fenton and solar Fenton processes: inexpensive green technologies for the decontamination of wastewater from toxic Rhodamine B dye pollutant

Abstract Advanced oxidation processes (AOPs) are projected as relatively cleaner technologies for the abatement of water pollution. This paper investigates the Fenton process as a potential tool for the degradation and eventual mineralization of a textile dye, Rhodamine B (RhB), in water. The effects of activation sources such as microwave (MW), ultrasound (US), and solar energy (SL) on the efficiency of the process were tested. Solar and solar catalytic Fenton processes are identified as the best processes and accordingly, relevant reaction parameters are identified and optimized. The optimum ratio of Fe2+:H2O2 obtained is 1:3 at 15 mg/l of RhB concentration and at pH 3–3.5, showing a degradation efficiency of 47% within 30 min of solar irradiation. ZnO enhanced solar Fenton mineralization of RhB. Persulfate (PS) enhances degradation moderately. The study demonstrated the potential of recycling Fe2+ by periodic replenishment of H2O2. Major reaction intermediates formed were identified by the LC-MS method. Photoluminescence (PL) spectral studies showed a progressive increase in •OH radical formation during solar irradiation. The study has proven that solar Fenton and solar catalytic Fenton processes are efficient AOPs for the complete mineralization of RhB and thus present an economic and environment-friendly technology to remove recalcitrant RhB pollutants from water.