Ensaios de tratabilidade empregando catalisador sintetizado à base de argila em processo oxidativo avançado para remediação de solo com HPAs

Abstract

The remediation of contaminated areas with polycyclic aromatic hydrocarbons (PAHs), which are persistent organic pollutants and have varied toxicity, becomes a great challenge due to the complexity of the soil and the pollutants. Several strategies for contaminated soils remediation with PAHs have been proposed with different degrees of success, among them is the advanced oxidative process. Different oxidants with varied activation forms for radical generation have been investigated. The oxidant activation can occur by homogeneous process, with iron as the most commonly agent, or heterogeneous, with solid catalysts supporting an active phase, for example. The effectiveness of the remediation technique is predicted by laboratory treatability studies. Thus, the present work evaluated the chemical oxidation of PAHs in artificially contaminated soil aiming an in-situ application. Hydrogen peroxide or sodium persulfate processes with activation by homogeneous reaction using iron sulfate and pH adjustment or heterogeneous reaction using solid catalyst were evaluated. Solid catalyst synthesis was developed employing iron ions as active phase supported on clay. The experiments were optimized applying an experimental design technique to appraise concentrations that would provide better contaminant removal efficiency. Kinetic studies and distribution evaluation of each contaminant in different phases were performed. The oxidation process employing the clay-based catalyst provided 80% removal of phenanthrene and 94% removal of naphthalene, with reproducible assays. Although homogeneous processes have slightly higher removals compared to heterogeneous processes under the applied conditions, the amount of iron required in the heterogeneous reaction was lower and the non-adjustment pH are significant advantages related to cost reduction and environmental caution. PAHs selected as creosote representants have greater affinity with the solid phase, observed in partitioning evaluation tests. In addition, a difference between the initial amount of contamination, from a freshly contaminated dry soil, and the amount determined at the end of the tests was observed, most likely due to sorption and water interference in extraction, for example. 96% of contaminants removal was achieved in oxidation assays of creosote contaminated soil. The removal was related to degradation and sorption processes, both in soil and in clay-based catalyst.