Integrated "adsorption-catalysis-adsorption" green strategy for efficient adsorption for the removal of methylene blue and catalytic preparation of hydrocarbon-rich, low N/O bio-oil.

• This study promoted the cycling of carbon and nitrogen in wastewater systems. • The "adsorption-catalysis-adsorption" strategy improved the recovery of waste. • Improved quality of bio-oil obtained with regenerated catalyst. • The maximum adsorption capacity of regenerated bio-char was 554.38 mg·g−1. This study proposes an "adsorption-catalysis-adsorption" strategy to improve the recycling capacity of bio-char, which has implications for improving bio-char utilization and reducing greenhouse gas emissions. A porous bio-char (EPAC) was prepared and used for effective methylene blue (MB) adsorption. The adsorbent after MB adsorption was used to fabricate a new carbon catalyst (EPMCC), which exhibited an excellent catalytic capacity for low N/O bio-oil. The nitrogen content of the bio-oil catalyzed by EPMCC decreased from 34.46 wt% to 17.04 wt%, and the hydrocarbon content increased from 15.52 wt% to 29.09 wt% compared to the pyrolysis of Enteromorpha clathrate alone. The used EPMCC was then regenerated to obtain a new EPMNC adsorbent with a high specific surface area (1097.99 m2·g−1). The maximum adsorption capacity of EPMNC was 554.38 mg·g−1, and the adsorption mechanisms involved electrostatic interactions, π-π interactions, and hydrogen bonding. This study promotes the cycling of carbon and nitrogen in organic wastewater systems containing nitrogen. [ABSTRACT FROM AUTHOR]