Degradation of surfactant used in iron mining by oxidation technique: Fenton, photo-Fenton, and H2O2/UV-A comparative study

Reuse of water in mining helps reduce the volume of tailings directed to dams, avoiding overloads and ruptures, as occurred in Brumadinho, Brazil. Water reuse in mining requires treatment mainly for removing the surfactant substances used. Photo-Fenton and UV/H2O2 showed 96% to 98% degradation results of anionic surfactants within 5 minutes, suggesting this technique is faster than biological systems that can take days. This paper aims to study the degradation of a surfactant used in the flotation process by UV/H2O2, Fenton, and photo-Fenton oxidation techniques. The compound was characterized by FTIR and MALDI-TOF. In degradation experiments, the variation in reactants concentrations was evaluated with hydrogen peroxide, iron sulphate heptahydrate, and oxalic acid. We used a synthetic solution of surfactant in the reverse flotation of ore with 180 mg/L. The reaction was monitored with TOC analysis and a spectrophotometer throughout the reaction. The UV/H2O2 and Fenton system were studied by varying peroxide and iron concentrations, with 120 minute tests. Additionally, photo-Fenton concentrations, the pH variation (1.5-8.0), temperature (15 degrees C, 21 degrees C, and 60 degrees C), and time were evaluated. The results showed the most efficient degradation was that using photo-Fenton, which achieved total TOC removal using 4500 mg/L of peroxide and 364 mg/L of iron for 330 minutes, while the UV/H2O2 system achieved 29% and 49% TOC removal of the Fenton. It is verified that the oxidative processes can be applied to degrade the surfactants present in the water recovered from the flotation processes.