REMEDIAÇÃO DE SOLO CONTAMINADO COM GASOLINA VIA PROCESSO TIPO-FENTON E AVALIAÇÃO DA TOXICIDADE.

Abstract

The contamination of soils by gasoline spills is a biggest environmental problem, mainly due to the hydrocarbons that derived from gasoline such as benzene, toluene and xylene. In this way, studies of modern remediation techniques of contaminated areas are important. The Advanced Oxidative Processes (AOPs) have are widely employed in remediation of areas contaminated by hydrocarbons, among the Fenton-type process, which has been used quite frequently in soil remediation. This process basically consists of the decomposition of hydrogen peroxide catalyzed by Fe3+ ions, and this process can also be catalyzed by the mineral forms of iron present in the soil. As a result, this work had as objective to evaluate and compare the efficiency of the Fenton-type process with addition of Fe3+ and using the mineral iron. As well as evaluating the effect of the presence of ethanol in gasoline during treatment and the phytotoxicity. For the determinations, gas chromatography coupled to the headspace system was used, where there was also a previous extraction associating the addition of sodium chloride, vortex and ultrasound, presenting recovery rates between 79,25% and 108,41% for benzene. The determination of BTX through CG-headspace proved to be a reliable method since in the studied linear range (0,05 to 80 mg Kg-1) showed good linearity with R2= 0.9989 for benzene and the precision evaluated was between 0,87 and 3,18%. The results obtained from the degradation studies showed that the processes were efficient in the removal of BTX. The obtained results showed that the processes were efficient in the removal of BTX. For reactions with iron addition (Fe3+) the reduction of BTX was greater than 93 ± 0,08% and 91 ± 0,24% for gasolines with and without ethanol, respectively after 120 minutes of reaction. And for reactions using only mineral iron, the removal was greater than 89 ± 0.78% and 67 ± 0.49% with ethanol and without ethanol, respectively. Evidence for the efficiency of iron oxides present in this soil sample. Despite the high efficiency of BTX removal, the phytotoxicity tests performed after treatment with Lactuca sativa seeds showed an increase in phytotoxicity. The results showed that after the treatment and regardless of the process used no germination of seeds occurred. Thus, the results indicate that by-products formed during degradation, present higher toxicity to the bioindicator Lactuca sativa. Thus, although the remediation processes used in this study prove to be efficient in removing BTX (removal> 67%), the treatment time of 120 minutes is not enough to remove phytotoxicity.