Tunable nanoarchitectonics of porous biochar through sequential calcium and potassium salt activation for high-efficiency removal of emerging pollutants.

Biomass-derived porous biochars perform exceptionally well in various fields due to their highly developed pore structures and low cost. Existing preparation methods lack diversity, limiting the ability to tailor pore architectures. This study introduces an innovative sequential activation method that uses different activating agents on biowaste to produce nanopore-rich porous biochars (NPBs). Using bamboo biomass, activation with calcium carbonate followed by potassium carbonate yielded NPBs with a well-developed pore network containing abundant mesopores and micropores, a specific surface area of 2061 m2/g, and a pore volume of 1.16 cm3/g. After two high-temperature activation steps, NPBs showed reduced oxygen content, increased hydrophobicity, and the formation of graphite-like structures. NPBs can rapidly remove emerging contaminants from water-including the plasticizer diethyl phthalate (652 mg/g) and the antibiotic sulfamethoxazole (689 mg/g)-exceeding the capacities of most reported sorbents. The primary sorption mechanisms involved pore filling, partitioning, π-π stacking, and hydrogen bonding. While phosphate ions interfered with sorption, other common coexisting solutes had limited effects, and NPBs performed well in real water samples. Seed germination tests revealed minimal short-term impacts on plant growth, with some promotion of stem elongation. This study presents a tunable strategy for porous carbon synthesis, with the derived products showing promise for applications in environmental remediation, energy, healthcare, and beyond.