Fast and environmental-friendly degradation of tert-butyl mercaptan from contaminated soil using bimetallic-modified Fenton process

Abstract

In this work, the fast remediation of <em>tert</em>-butyl mercaptan from the polluted soil via a bimetallic Fenton treatment that included Fe²⁺/Fe³⁺/Fe⁰/Cu²⁺ in the presence of gasoline was studied. The analysis of variance and the Pareto analysis resulting from the central composite design (CCD) showed that the H₂O₂, CuSO₄, Fe₃O₄ nanoparticles, nano zerovalent iron (nZVI), and gasoline initial concentrations as a secondary contaminant were influential factors on the removal efficiency of tert-butyl mercaptan (with an effectiveness of 2.09%, 13.38%, 1.92%, 2.01%, and 39.73% respectively). Moreover, the interaction of H₂O₂/nZVI, H₂O₂/nFe₃O₄, H₂O₂/CuSO₄, nZVI/nFe₃O₄, and nZVI/CuSO₄ had a positive effect on removal efficiency, while nFe₃O₄/CuSO₄had a negative one. Surprisingly, the mixing of nZVI and nFe₃O₄ before adding them to the reactor did not affect the removal efficiency. The optimum conditions suggested for the maximum removal efficiency of tert-butyl mercaptan were the minimum levels of the initial gasoline concentration (2.5 %w/w), a maximum level of CuSO₄ (0.12 %w/w), and an optimum concentration of H₂O₂, nano-ZVI, and nano-Fe₃O₄ (8.92 %w/v, 0.1194 %w/w and 0.0898 %w/w, respectively) in the studied intervals. This condition led to a 99.27% efficiency removal of tert-butyl mercaptan removal in 20 minutes without pH and temperature adjustments.