Caracterização e avaliação do processo de adsorção como alternativa de tratamento para efluente gerado durante a gaseificação de resíduos sólidos

Abstract

The gasification of solid waste, although an efficient alternative for energy generation, produces liquid effluents with a high pollutant load, which require proper treatment to enable their disposal or reuse. In this context, the present study aimed to evaluate the adsorption process as a treatment alternative, with emphasis on the reuse of the effluent in the industrial process itself. For this purpose, two adsorbents were tested: commercial activated carbon and biochar produced from açaí seed. Initially, the effluent was characterized in terms of physicochemical parameters, showing high acidity (pH 3.7), outside the range permitted by CONAMA Resolution No. 430/2011, which establishes a pH between 5.0 and 9.0 for discharge into water bodies. In addition, the effluent presented a high organic load, measured as chemical oxygen demand – COD (6875 ± 321 mg O₂/L), high dissolved organic carbon – DOC (1620 ± 9 mg/L), significant presence of oils and greases (392 ± 83 mg/L), and intense true color (1399 ± 49 mg/L Pt/Co), all considerably high according to the same resolution, reinforcing the need for pretreatment prior to disposal or reuse. To verify the efficiency of the adsorption process, different operational conditions were evaluated: adsorbent concentration (0.5 to 5.0 g/L), contact time (5 to 80 minutes), and application in sequential cycles. Increasing the activated carbon concentration from 0.5 to 3.0 g/L improved the removal efficiency of color and COD, reaching a maximum of 51% and 10%, respectively, while higher concentrations (4.0 and 5.0 g/L) showed no significant gains. Regarding contact time, no expressive improvements were observed above 5 minutes, which was defined as the optimum time for combining efficiency and operational simplicity. In sequential adsorption tests, the fractionation of 3.0 g/L into three cycles of 1.0 g/L was evaluated. However, no relevant increase in removal was observed compared to the direct application of 3.0 g/L. It was also observed that açaí seed biochar presented better efficiency in the removal of true color and COD. Based on this study and considering the low removal of color and especially COD, future studies are suggested to evaluate the effect of pH as well as the use of other adsorbent materials.