Resumo

Polychlorinated biphenils (PCBs) are compounds of high toxicity, widely used as dielectric fluids in capacitors and transformers. Brazilian government estimates that 100,000 tons of equipments containing PCBs were commercialized, which must be properly destroyed until 2025. The main objective of this research was to evaluate the feasibility of applying a standard solution of PCBs congeners in anaerobic degradation in reactors undergoing fermentative-methanogenic conditions. Anaerobic biomass from an UASB reactor used in the treatment of poultry wastewater was used as inoculum in the assays of extraction and adsorption. Anaerobic reactors were inoculated with 10% (w/v) of biomass under nitrogen flow (100%) in the Angelidaki medium containing co-substrates (ethanol and sodium formate), 12 mg mL^-1 of polyurethane foam and 0.5 mg mL^-1 of the standard solution of PCBs (Congener Mix1 - Sigma-Aldrich). The reactors were incubated at 30°C and 150 rpm for 48 hours. Different conditions were tested to standardize the method of PCBs extraction, searching for the best results for the recovery of the analytes. Calibration curves were prepared with six concentrations of PCBs mix (0.05, 0.1, 0.2, 0.3, 0.4 and 0.5 mg mL^-1) and octachloronaphtalen (0.1 mg L^-1) as internal standard, in triplicate. After 48 hours of incubation, differential extraction of PCBs present in the liquid and in the polyurethane foam was made with 20 ml of n-hexane without any other purification step (as glass column chromatography, for example) and the samples were concentrated, suspended in 0.3 mL of n-hexane and injected in a gas chromatograph with electron capture detector. The analysis of the response factors of each substance showed that the six congeners were adsorbed on polyurethane foam. The calibration curves obtained showed linearity in the concentration range from 0.05 to 0.5 g mL^-1 and the correlation coefficients (R²) varied from 0.74 to 0.98 due to the great difficulty of reproducibility of the extraction, impaired by the presence of the biomass. This method of liquid-liquid extraction was suitable for the recovery of such compounds from the reaction medium and can be efficiently used for later studies of quantification of the removal of PCBs by anaerobic microbial consortium.