We have explored the simultaneous degradation of cyanides and thiocyanate present in wastewaters from a cokemaking factory using photoassisted methods under varied illumination conditions (from simulated solar light to UV light). Overall, the photochemical degradation of cyanides was more efficient than that of thiocyanates, regardless of the illumination conditions, the effect being more pronounced in the absence of a photocatalyst. This is due to their different degradation mechanism that in the case of thiocyanates is dominated by fast recombination reactions and/or charge transfer reactions to electron scavengers. In all cases, cyanate, ammonia, nitrates, and nitrites were formed at different amounts depending on the illumination conditions. The conversion yield under simulated solar light was almost complete for cyanides and quite high for thiocyanates after 6 h of illumination. Regarding toxicity, photochemical oxidation at 254 nm and under simulated solar light decreased significantly the toxicity of the pristine wastewater, showing a correlation with the intensity of the irradiation source. This indicate that simulated light can be effectively used to reduce the toxicity of industrial effluents, opening an interesting perspective for optimizing cyanide detoxification systems based on natural light.

El objetivo de este trabajo es evaluar la viabilidad del uso de permanganato de potasio como método eficaz para la degradación de aguas residuales procedentes del sector de la minería aurífera que contienen cianuros y tiocianatos. Para ello se llevó a cabo la degradación simultánea de ambas especies cianuradas en aguas industriales. Los resultados indican que el permanganato de potasio es un agente oxidante eficaz para la eliminación de cianuro de aguas residuales de la minería aurífera. Se lograron porcentajes de eliminación de cianuro entre 95 y 100 %, en aguas con una concentración inicial de cianuros de 312 mg/L y de tiocianatos de 314 mg/L. En cambio, la eficiencia de degradación de tiocianatos es mucho menor, con porcentajes de eliminación inferiores al 50 % para altas concentraciones de oxidante. Los estudios oxidativos en aguas sintéticas mostraron que la oxidación parcial de tiocianatos da lugar a la liberación de cianuros en el agua. Por este motivo, la oxidación simultánea de cianuros y tiocianatos en las aguas residuales estudiadas no es completa, encontrándose concentraciones residuales, no despreciables, de ambas especies cianuradas, tras la reacción con el permanganato. Esto hace necesario aplicar otros métodos de oxidación para la eliminación total de las especies cianuradas.

The paper presents the design, implementation and results of a microbial single-well stimulation test performed at the Diadema field in Argentina. The purpose of the test was to achieve increased production by injecting a microbial formulation and nutrients, and to gain experience with this procedure under actual field conditions. Two out of five treated wells showed excellent oil production response to the microbial stimulation.The results suggest that a microbial-enhanced waterflood could be implemented successfully at the Diadema field.