Wet-stable cellulose-biochar renewable composite foams with selective antibiotic decontamination from water

A simple yet efficient approach to fabricate porous biobased foams for wastewater purification containing antibiotics such as norfloxacin and ciprofloxacin is shown. Cellulose pulp is utilized as a cheap and environmentally sustainable platform material. To enhance its mechanical durability in water, essential towards practical deployment, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNFs) and biochar were added, increasing the specific surface area from 0.64 m² g^-1 to 47.27 m² g^-1. Mechanical compression tests prove enhanced stability and shape-recovery, where 0.4 wt% biochar enhances the modulus from 0.9 to 38.1 kPa when compared against neat cellulose pulp foam. The achieved limited pore-collapse allows potentially active internal surfaces to remain accessible for pollutants over multiple cycles. The hybrid foams were tested for the remediation of two antibiotics (norfloxacin, ciprofloxacin), two common dyes (methylene blue, methyl orange), and two endocrine disruptors (bisphenol A, bis(2-ethylhexyl) phthalate), showing contaminant removal rates of >60% after 24 h for norfloxacin, ciprofloxacin, and methylene blue. Pollutant removal is dominated by the affinity of the carboxylate groups in the TOCNFs and the accessibility of the pollutants to the active sites, rather than by the swelling of the foam. This work proves the implementation of easily manufacturable yet functionally performing cellulose/biochar foams for the purification of wastewater containing emerging contaminants.