Sulfate-enhanced degradation of Rhodamine B in the hydrogen peroxide/hydroxylamine system

Abstract

Hydroxyl radicals are commonly produced either by metal activation or by using external energy. However, the application of these methods is limited by low working pH and secondary contamination with metal ions. Alternatively, the reaction between hydrogen peroxide (H2O2) and hydroxylamine is an environmentally friendly process that generates active radicals, but the reaction rate is slow. To improve this, we report here a novel and efficient activator for the H2O2/hydroxylamine system that uses sulfate ions ($${\text{SO}}_{4}^{2 - }$$). We tested the effects of different systems, concentrations of H2O2, hydroxylamine and $${\text{SO}}_{4}^{2 - }$$, and pH on the degradation of Rhodamine B. The mechanism was also investigated by kinetic calculation, a radical scavenging experiment, and anions comparison. Results show that the addition of $${\text{SO}}_{4}^{2 - }$$ effectively improved Rhodamine B degradation and widened the working pH. The hydroxyl radical was found to be the primary radical responsible for dye degradation. Moreover, only $${\text{SO}}_{4}^{2 - }$$ shows an enhanced effect under the same ionic strength conditions. Overall, our findings reveal a new method for water purification at acidic and near-neutral pH, especially for sulfate-rich wastewater treatment.