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Biochar-derived C-Dots from Picea, Molinia caerulea and Elaeis guineensis were synthesized through a hydrothermal process, and their physicochemical and optical characteristics and environmental effects were compared. These C-Dots were characterized by techniques such as Attenuated Total Reflection–Fourier Transform Infrared (ATR-FTIR), UV-Vis spectrophotometry, fluorescence spectroscopy, dynamic light scattering (DLS), Z potential, and High-Resolution Transmission Electronical Microscopy (HR-TEM). The ecotoxicity tests were performed using the Microtox™ test, making this study one of the few that use this method. The C-Dots from Molinia caerulea showed the best quantum yield (QY) of 8.39% and moderate ecotoxicity, while Elaeis guineensis has the lowest QY (2.31%) but with zero toxicity. Furthermore, the C-Dots from Picea presents good optical properties but showed high toxicity and limits its use. Finally, all C-Dots showed functional groups that could be biofunctionalized with biomolecules, especially C-Dots from Molinia caerulea and Elaeis guineensis show potential for use in the development of optical biosensors.

Graphical Abstract

Effluents from the textile industry have a negative environmental impact due to their high load of dyes and hard-to-remove compounds: additives, detergents, and surfactants; these must be treated before effluents can be discharged into water. White-rot fungi show great potential for the bioremediation of water and soil matrices contaminated with recalcitrant pollutants (these are generally toxic). In this work, we designed a 5 L fixed bed reactor and evaluated its performance on the degradation of pollutants in effluents from the textile industry in continuous-operation mode under non-sterile conditions, using ligninolytic fungus Bjerkandera sp. (anamorphic state R1). This setup was based on a previous design of a 0.25 L fixed-bed model bioreactor. The system was designed by taking into account the geometric and hydrodynamic similarities of both setups. In continuous-mode color-removal assays, the bioreactor was operated at a 36 h Hydraulic retention time (HRT), a 1 L/min air flux at 33°C, and a dye concentration of 75 g/L (sulfur black 1) and 6.5 g/L (indigo Vat blue 1). 69% of the dye was removed, and changes in the chemical structures of the dyes confirmed the ligninolytic activity of the microorganism as the main dye removal mechanism.. RESUMEN: Los efluentes provenientes de industrias textiles generan impactos ambientales negativos, debido a altas cargas de colorantes y compuestos de difícil remoción como aditivos, detergentes y surfactantes, los cuales deben ser tratados antes de ser descargados a cuerpos de agua. Los hongos ligninolíticos han mostrado gran potencial para procesos de biorremediación de aguas y suelos contaminados con compuestos recalcitrantes y generalmente tóxicos. Este trabajo, se enfoca en el diseño y evaluación del desempeño de un reactor de 5L de lecho fijo para la degradación de efluentes de la industria textil en condiciones no estériles y operación continua, usando el hongo ligninolítico Bjerkandera sp. en su estado anamorfo R1. Dicha tecnología se desarrolló tomando como base para realizar el diseño un biorreactor modelo de lecho de fijo de 0,25 L. El sistema de 5L se diseñó teniendo en cuenta la similitud geométrica e hidrodinámica. En los ensayos de decoloración en continuo el reactor se operó a un tiempo de retención hidráulica (TRH) de 36 h, aireación de 1 L/min y 33°C, además de una carga de colorante de 75g/L para el Negro sulfuroso y 6,5g/L para índigo Vatblue; se alcanzó una decoloración del 69% y se identificaron cambios en las estructuras químicas de los colorantes presentes en el agua residual después del tratamiento, mostrando la actividad ligninolítica del microorganismo como el principal mecanismo de remoción de color.

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