Single-step sustainable production of activated carbon from microalgal biomass: An approach to waste recovery from urban wastewater

The growing need for sustainable waste management and the increasing demand for eco-friendly materials have driven the exploration of microalgae as a renewable resource for activated carbon production. Microalgae offer advantages such as rapid growth, high photosynthetic efficiency, and the ability to utilize wastewater for cultivation, making them an appealing alternative to traditional biomass sources. Activated carbon was produced from microalgal biomass grown in high-rate aerobic ponds fed with the effluent from an up-flow anaerobic sludge blanket reactor treating urban wastewater. The microalgal biomass was subjected to different harvesting (physical, flocculation, and coagulation) and pretreatment (thermal and thermochemical) methods to investigate the influence of these factors on the physicochemical properties of activated carbons. Fourier-transform infrared spectroscopy showed that biomass pretreatment influenced the composition of activated carbons. Pretreatment reduced yield by up to 5 % and increased the thermostability of activated carbons, indicating a reduction in the presence of less recalcitrant compounds. The combined use of Tanfloc (R) for biomass harvesting and thermochemical pretreatment resulted in a high specific surface area, as observed for ACT-pH 3 (415 m2/g) and ACT-pH 8 (382 m2/g). This study provides recommendations for optimizing the production of activated carbon from microalgal biomass grown on urban wastewater, offering a route to waste recycling and promising prospects for the sustainable development of activated carbon materials.