Catalytical degradation of diesel contaminated soil using smectite-fe catalyst with h2o2

Currently, the types of treatment for oil-contaminated soil include soil vapor extraction (SVE), biological decomposition, solvent extraction, air stripping, activated carbon adsorption, and oxidation. Among these, solvent extraction, air stripping and activated carbon adsorption can only deal with the transfer between phases and must be supported with other types of treatment to complete remediation. Moreover, they are costly and could destroy local ecological systems. The objective of this study is to explore the fastest degradation rate of diesel contaminated soil and conditions needed for it through batch experiments, in which commercially available smectite is used as a catalyst carrier, modified into nano smectite-Fe catalyst using Fe+3, and reacted withH2O2to treat diesel contaminated soil. In terms of the basic properties of the test soil: the Lo series soil, it is characterized by high clay content, microscopic particles, relatively large specific surface area, extremely high cation exchange capacity, high soil density, and high organic matter content, which all contribute to the high diesel adsorption. As for the effects of smectite-Fe catalyst of various wt%and H2O2of different concentrations on the degradation rate of diesel contaminated soil, the result shows that the higher the concentration of H2O2, the higher the degradation rate of diesel, since smectite-Fe catalyst facilitated the formation of •OH at high H2O2 concentration during the beginning of the reaction. However, the degradation rate of diesel declined, and the shielding effect occurred more often when H2O2 of more than 5~10% of the total weight and more smectite-Fe catalyst were added to the catalytic reaction. Hence, it can be inferred that excessive H2O2 and smectite-Fe catalyst will exhaust catalytic sites. Although more electrons and •OH were formed when H2O2 reacted with the smectite-Fe catalyst, the amount of formed •OH decreased when the two reactedin the Lo series soil, signifying a decline in the catalytic activity.