Persulfates to degrade a mixture of dyes (rhodamine B, methylene blue) in the presence of glucose and visible light

A treatment process utilizing visible-light-activated (Vis) persulfates (PS) in the presence of an organic promoter (glucose) was developed for the simultaneous decolorization of a rhodamine B (RhB) and methylene blue (MB) mixture. Various doses of glucose, PS concentrations, pH values, initial dye concentrations and process time were tested to find out the most appropriate parameters for degrading the RhB/MB mixture in the PS/Vis/Glucose process. Under optimal conditions (C0[RhB/MB] = 5 ppm; pH = 4; glucose dosage = 230 mM; PS concentration = 30 mM; time = 120 min), the degradation of MB and RhB in the mixture was set to 87.8% and 54.7%. The degradation process followed the pseudo-first-order kinetic model with the correlation coefficient R2 = 97%-99%. The PS/Vis/Glucose process is more economical than other existing studies and technologies. The energy efficiency at the optimal conditions were 1.2 and 2.1 kWh m–3 for RhB and MB, respectively. The domination of MB degradation over RhB was confirmed and found to appear as a result of the different physicochemical properties of the dyes and their state of charge, which enables the direct transfer of electrons from the dyes to the PS and leads to the decolorization of the dyes. This work provides an important source of information on the parameters influencing the simultaneous degradation of mixtures of dyes (rhodamine B, methylene blue). The experimental results showed that the PS/ Vis/Glucose process may have a positive role in treating color solution mixtures with various dye concentrations (1-20 ppm).