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Conselho Nacional de Desenvolvimento Científico e Tecnológico This work was intended to evaluate the performance of sequential hybrid bioreactor systems, without aeration and with intermittent aeration, when removing chrome (VI), Total chrome, Total organic carbon (COT) from an effluent containing Cr (VI). Chemical Oxygen Demand (DQO) and the biomass concentration also were monitored. As inoculum in the bioreactors, mixed cultures were used from microorganisms originated in the industrial sludge, previously adapted, and with Cr source (VI), the potassium dichromate (K2Cr2O7). It was initially performed a blank test, before adding chrome to the system, with the purpose to verify the influence of the metal presence in the COT removal. Were performed 3 kinetic assays, in chrome hexavalent initial concentrations of 80, 120 and 150 mg/L. After each kinetic, it was evaluated the removal during the bioreactor regeneration, with the same effluent, but with no chrome. The Cr (VI) concentration was defined by the colorimetric method using diphenylcarbazide 3500-Cr D, according to APHA (2005). The total chrome concentration was measured in the atomic absorption Spectrophotometer AA-7000 Shimadzu. The characterization regarding COT was performed by the using the technique catalytic combustion at high temperature, using the TOC-VCPH-ASI+TNM-1 analyzer from Shimadzu. For kinetic with concentration of 80 mg/L de Cr (VI), the results showed that after 600 hours of operation the bioreactors did not saturated, obtaining 87% of global removal of Cr (VI) and 62% of total chrome. For kinetics of 120 and 150 mg/L, inside the operation time studied, only the nor aerated bioreactor had saturation, after 228 and 216 operation hours, respectively. The chrome removal, in the TDH adopted, were satisfactory in all concentrations studied. In the regeneration, it was verified, in all assays performed, that the chrome concentration in the bioreactor output became practically nil in a maximum of 72 hours of operation. In the blank test, the COT removal reached was 64% while in the 3 assays using chrome, it was around 55 % (80 mg/L), 41 % (120 mg/L) and 31 % (150 mg/L). In the bed regeneration, the COT removal increased, indicating that the presence of chrome affects the COT removal, due to the possible metal accumulation. The DQO concentration had a similar profile to the COT concentration kinetic. After addition of a new inoculum to the system, the kinetic assay was repeated in concentration of 150 mg/L of Cr (VI), being that in 600 operation hours, the bioreactors did not saturated, obtaining removal of 67% for Cr (VI) and 46% for total Cr. The COT removal was not significantly changed. The biomass concentration remained practically constant in the experiment, except in the beginning of each kinetic, where it was verified the occurrence of death and cell lysis, due to the increase of the Cr (VI) concentration added. However, during the process the mixed culture readapted to the new conditions. It was performed the cell opening by ultra sound where its noticed a low quantity of chrome retained inside it, by bioaccumulation. This indicates that most of the chrome is bio-absorbed in the cell surface (deposited), of living and dead cells, or bio accumulated in living cells. Given the above, the hybrid bioreactor system, operating in series, showed promising to the chrome removal. However, some changes in the system and in the process itself, as the periodical reposition of biomass, are needed to a better performance. O presente trabalho avaliou o desempenho do sistema de biorreatores híbridos sequenciais, sem aeração e com aeração intermitente, na remoção de Cromo (VI), Cromo Total, Carbono Orgânico Total (COT) de um meio sintético (afluente) contendo Cr (VI). A Demanda Química de Oxigênio (DQO) e a concentração de biomassa também foram monitoradas. Como inóculo nos biorreatores, foram utilizadas culturas mistas de micro-organismos originária de lodo industrial, previamente adaptadas, e como fonte de Cr (VI), o dicromato de potássio (K2Cr2O7). Incialmente foi realizado um teste em branco, antes da adição de cromo ao sistema, com o propósito de se verificar a influência da presença do metal na remoção de COT. Foram realizados três ensaios cinéticos, nas concentrações iniciais de cromo hexavalente de 80, 120 e 150 mg/L. Após cada cinética, avaliou-se a remoção durante a regeneração dos biorreatores, com o mesmo efluente, porém sem cromo. A concentração de Cr (VI) foi determinada pelo método colorimétrico utilizando difenilcarbazida 3500-Cr D, conforme APHA (2005). A concentração de Cromo Total foi medida em Espectrofotômetro de absorção atômica AA-7000 Shimadzu. A caracterização em relação ao COT foi realizada pela técnica de combustão catalítica a alta temperatura, empregando o aparelho analisador TOC-VCPH-ASI+TNM-1 da Shimadzu. Para a cinética com concentração de 80 mg/L de Cr (VI), os resultados mostraram que após 600 horas de operação não ocorreu a saturação dos biorreatores, obtendo-se 87% de remoção global de Cr (VI) e 62% de Cromo Total. Para as cinéticas de 120 e 150 mg/L, dentro do tempo de operação estudado, apenas o biorreator não aerado atingiu a saturação, após 228 e 216 horas de operação, respectivamente. As remoções de cromo, no TDH adotado, foram satisfatórias em todas as concentrações estudadas. Na regeneração, verificou-se, em todos os ensaios realizados, que a concentração de cromo na saída dos biorreatores se tornou praticamente nula em no máximo 72 horas de operação. No teste em branco, a remoção de COT alcançada foi de 64% enquanto que nos três ensaios, na presença de cromo, esta foi em torno de 55 % (80 mg/L), 41 % (120 mg/L) e 31 % (150 mg/L). Na regeneração dos leitos, a remoção de COT aumentou, indicando que a presença de cromo afeta a remoção de COT, devido à possível acumulação do metal. A concentração de DQO teve um perfil semelhante à cinética de concentração de COT. Após adição de novo inóculo ao sistema, repetiu-se o ensaio cinético na concentração de 150 mg/L de Cr (VI), sendo que em 600 horas de operação, os biorreatores não saturaram, obtendo remoções de 67% para o Cr (VI) e 46% para o Cr Total. A remoção de COT não foi alterada significativamente. A concentração de biomassa permaneceu praticamente constate nos experimentos, exceto no início de cada cinética, onde se verificou a ocorrência de morte e lise celular, devido ao aumento da concentração de Cr (VI) adicionada. No entanto, com o decorrer do processo a cultura mista se readaptou às novas condições. Foi realizada a abertura de células por ultrassom, onde foi constatada uma quantidade baixa de cromo retido no interior das mesmas, em relação à quantidade presente no meio. Isso indica que a maior parte do cromo está biossorvido na superfície celular de células vivas e mortas, ou bioacumulado em células vivas. Diante do exposto, o sistema de biorreatores híbridos, operando em série, mostrou-se promissor para a remoção de cromo. No entanto algumas alterações no sistema e no próprio processo, como a reposição periódica de biomassa, são necessárias para um melhor desempenho. Mestre em Engenharia Química

In this study, kinetics of the removal of Cr (III) from the waters by adsorption have been investigated using montmorillonite natural clay that was obtained from the vicinity of Narman, Erzurum in Turkey. Activation energy, thermodynamic values and adsorption kinetics were determined. In addition, the trials were repeated by subjecting to the same adsorbent activation process. The values ​​found for these two adsorbents were compared. As a result of the experiments, the parameters affecting the adsorption kinetics were examined. It was determined that the adsorption process could be best depicted by pseudo second order reaction kinetics. Using pseudo second order reaction rate constants, ΔH° = -25.791 kJ mol-1 and ΔS° = 106.19 joule mol-1 were calculated for raw adsorbent. For the activated adsorbent, ΔH° = -18,806 kJ mol-1 and ΔS° = 79.37 joule mol-1 were calculated. That ΔG° increases as temperature increases indicates; adsorption is more spontaneous at high temperatures. Negative ΔH° values show that the reaction is exothermic. The positive values of ΔS° indicate increased randomness at the adsorbent/solution interface during the adsorption of chrome., EQA - International Journal of Environmental Quality, Vol. 45 (2021)

The present work studies the possibility of using two solid industrial wastes TERMOPAIPA'S fly ash and ECOPETROUS FCC catalyzer waste in removing and recovering chrome from tanneries’ liquid effluent. Fly ash was subjected to two alkaline hydrothermal treatments for obtaining zeolytic structures having better properties; waste catalyser was calcined for eliminating surface coke. Solids were characterized following treatment including DRX, BET area and CEC. A colorimetric method was standardized for determining chrome in solution; a response surface experimental design was implemented for finding optimum removal conditions. The most efficient adsorbent was fly ash treated with increased NaOH concentration; optimum conditions for removing chrome were: 58 minutes at 36°C, 5.9 pH and 31% w/v solid removal. When reused, it was found that the two batches of treated fly ash became saturated following 6 cycles of use, whilst original ash and FCC catalyzer became saturated the second time they were used. Four de-absorbent agents were used for recovering chrome from adsorbent product, H2SO4 0.6 M being the best. Field trials showed that removal efficiency became reduced by the effect of other contaminants, depending on the solution’s initial concentration.

El presente trabajo estudia la posibilidad de utilizar dos desechos sólidos industriales: la ceniza volante de TERMOPAIPA y el catalizador de equilibrio gastado (FCC) de ECOPETROL, en la remoción y recuperación de cromo de los efluentes líquidos de las curtiembres. La ceniza volante se sometió a dos tratamientos hidrotérmicos alcalinos para obtener estructuras zeolíticas de mejores propiedades, y el catalizador gastado se calcinó para eliminar el coque de su superficie. La caracterización de los sólidos que se obtuvieron luego de los tratamientos incluyó DRX, área BET y CEC. Se estandarizó un método colorimétrico para la determinación de cromo en solución y se implementó un diseño de experimentos del tipo superficies de respuesta para encontrar las condiciones óptimas de remoción. El absorbente más eficiente fue la ceniza volante tratada con la mayor concentración de NaOH, y sus condiciones óptimas de remoción de cromo fueron 36ºC, 58 minutos, pH de 5.9 y una relación sólido a solución de 31% p/v. En la reutilización se encontró que las dos cenizas volantes tratadas se saturan con 6 ciclos de uso, mientras que la ceniza original y el catalizador FCC se saturan en la segunda vez. La recuperación de cromo desde el absorbente se intentó con cuatro agentes desorbentes, de los cuales el mejor fue el H2SO4 0.6 M. Finalmente, las pruebas de campo realizadas demostraron que la eficiencia de la remoción disminuye por el efecto de otros contaminantes y que depende de la concentración inicial de la solución. The present work studies the possibility of using two solid industrial wastes TERMOPAIPA's fly ash and ECOPETROL's alkaline hydrothermal treatments for obtaining zeolytic structures having better propierties; waste catalyser was calcined for eliminatin surface coke. Solids were characterised following treatment including DRX, BET area and CEC. A colorimetric method was standardised for determining chrome in solution; a response surface experimental design was implemented for finding optimum removal conditions. The most efficient adsorbent was fly ash treated with increased NaOH concentration; optimum condictions for removing chrome were: 58 minutes at 36ºC, 5.9 pH and 31% w/v solid removal. When reused, it was found that the two batches of treated fly ash became saturated following 6 cycles of use, whilst original ash and FCC Catalyser became saturated the second time they were used. Four de-absorbent agents were used for recovering chrome from adsorbent product H2SO4 0.6M being the best. Field trials showed that removal efficiency became reduced by the effect of other contaminantsm depending on the solution's initial concentration.