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. •Grape pomace (GP) and its secondary waste were used for biochar production.•GP lignin derived biochar (GPL2700) showed the highest Pb adsorption capacity.•GPL2700 showed good adsorption at a low Pb level in contaminated drinking water.•Chemisorption and physisorption mechanisms accounted for Pb removal of GPL2700.