RESUMO
La presencia de metales pesados, como el plomo (Pb+2), en los cuerpos de agua genera alteraciones sobre la calidad ambiental y la salud pública, debido a su solubilidad y su capacidad de acumulación en la cadena trófica, problemática que se puede incrementar por la acumulación de Eichhornia crassipes, una maleza acuática con alta capacidad invasora, cuya presencia en los ecosistemas acuáticos favorece los procesos de eutrofización y crecimiento de microorganismos patógenos, vectores de enfermedades. Como alternativa para la eliminación de metales pesados y el aprovechamiento de tallos TEC y hojas HEC de E. crassipes, se evaluó la capacidad de adsorción y de eficiencia de remoción de Pb+2 en solución acuosa, de dicha biomasa. Inicialmente, se realizaron ensayos batch, para analizar la influencia de la dosis de adsorbente, tiempo de contacto y pH de la solución. Como método de disposición final, se analizó la calcinación, a temperaturas de 700 y 800°C. Los datos experimentales de equilibrio fueron correlacionados, utilizando los modelos de Langmuir y Freundlich. El modelo que mejor se ajustó fue el de Langmuir, con R² = 0,9816 TEC y R² = 0,9854 HEC, lográndose una máxima capacidad de adsorción de 172,41mg/g TEC y 131,58mg/g HEC, con 0,2g de biomasa/200mL, pH 5,5 y 3h de contacto. En todos los ensayos, se lograron remociones de Pb+2 superiores al 97%. Los ensayos de calcinación indican que, a temperaturas ≥800°C, es posible estabilizar la biomasa residual, impidiendo que los cationes metálicos removidos sean liberados de la matriz biológica, por efectos de soluciones lixiviantes de bajo pH.
The presence of heavy metals such as lead (Pb+2) in water bodies causes alterations in environmental quality and public health due to their solubility and capacity of accumulation in the food chain. Problems that can be increased by the accumulation of Eichhornia crassipes an aquatic weed with high invasive capacity whose presence in the aquatic ecosystems favors the processes of eutrophication and growth of pathogenic microorganisms vectors of diseases. As an alternative for the removal of heavy metals and the use of TEC stems and HEC leaves of E. crassipes, the adsorption capacity and removal efficiency of Pb+2 in aqueous solution of this biomass were evaluated. Initially batch tests were performed to analyze the influence of the adsorbent dose, contact time and solution pH. As final disposal method, the calcination was analyzed at temperatures of 700 and 800°C. The equilibrium experimental data were correlated using the Langmuir and Freundlich models. The best fit model was the Langmuir model with R²=0.9816 TEC and R²=0.9854 HEC, achieving a maximum adsorption capacity of 172.41mg/g TEC and 131.58mg/g HEC with 0.2 g Of biomass/200mL, pH 5.5 and 3h of contact. Pb+2 removals above 97% were achieved in all tests. Calcination tests indicate that at temperatures ≥800°C it is possible to stabilize the residual biomass by preventing the removed metal cations from being released from the biological matrix by the effects of low pH leaching solutions.
RESUMO
A ocorrência de florações de cianobactérias em mananciais de abastecimento público prejudica a qualidade da água, podendo, inclusive, ocasionar a presença de cianotoxinas. A dificuldade de remover as cianotoxinas da água motivou o presente trabalho, cujo objetivo foi o de avaliar a remoção da cianotoxina microcistina empregando diferentes carvões ativados em pó (CAPs). Os CAPs foram caracterizados quanto ao número de iodo, granulometria, distribuição e volume de poros, além das isotermas de Freundlich. Os resultados mostraram que os CAPs de madeira apresentaram os maiores valores do número de iodo, capacidade máxima adsortiva (qe, máx) e volume de microporos secundários e mesoporos. A adequada caracterização do CAP é uma etapa importante na sua aquisição pelas estações de tratamento de água, pois índices isolados podem não avaliar corretamente o CAP.
The cyanobacterial bloom's occurrence in sources of public supplying harms water quality, even causing cianotoxins presence. The difficulty of the cianotoxins removal from the water has motivated the present work, which objective was to evaluate the removal of the cianotoxin microcystin through the use of different powdered activated carbons (PACs). The PACs were characterized according to its iodine number, granulometry, distribution and volume of pores, besides the Freundlich isotherms. The results showed that the wood PACs presented the highest values of iodine number, maximum adsorptive capacity (qe, max) and volume of secondary micropores and mesoporos. The adequate characterization of the PACs is an important stage in its acquisition by the water treatment plants, because isolated indices can not evaluate the PACs correctly.