Grape pomace and its secondary waste management: Biochar production for a broad range of lead (Pb) removal from water

Grape pomace (GP) management has been a challenge worldwide. We have previously demonstrated a biorefinery process to recover oil and polyphenols, and produce biofuels from GP sequentially, although over 50% of GP solid waste remains post-processing. To approach zero solid waste during GP processing, herein a pyrolysis process was designed for converting GP and its secondary processing wastes to biochars, which were then evaluated for lead (Pb) adsorption from water. GP lignin pyrolyzed at 700 °C (GPL2₇₀₀ biochar) with specific surface area of 485 m²/g showed the highest Pb adsorption capacity, and achieved 66.5% of Pb removal from an initially high concentration of 300 mg/L within 30 min. At low initial Pb concentrations (50–3000 μg/L), GPL2₇₀₀ biochar could reduce Pb concentrations to 0.208–77.2 μg/L. In addition, experimental and modeling results revealed that both physisorption and chemisorption mechanisms were involved in the adsorption process of GPL2₇₀₀ biochar.