Sludge-based biochar adsorbent: pore tuning mechanisms, challenges, and role in carbon sequestration

Highlights

•	Utilizing sludge's unique feature can unlock many new and feasible biochar modulation strategies.
•	Sludge carbonization and activation mechanisms reveal the crucial factors for micropore decorating.
•	Sludge biochar is compared with activated carbon to reveal requirements for practicality.
•	Sludge-based biochar application supports carbon sequestration and economic sustainability.

Abstract

Sludge biochar, a carbonized product of raw sludge, contains porous architectures that can act as epicenters for adsorbing external molecules through physical or chemical bonding. Sludge biochar also immobilizes innate micropollutants, which is advantageous over conventional sludge disposal methods. To date, numerous strategies have been discovered to improve sludge biochar morphology, but the influential factors, pore tuning mechanisms, and process feasibility remain imprecise. This knowledge gap limits our ability to design a robust sludge-based biochar. Herein, we present state-of-the-art sludge biochar synthesis methods with insight into structural and chemical transformation mechanisms. Roadblocks and novel concepts for improving sludge biochar porous architecture are highlighted. For the first time, sludge biochar properties, adsorption performances, and techno-economic perspectives were compared with commercial activated carbon (AC) to reveal the precise challenges in sludge biochar application. More importantly, sludge biochar role in carbon sequestration is detailed to demonstrate the environmental significance of this technology. Eventually, the review concludes with an overview of prospects and an outlook for developing sludge biochar-based research.

Funding

United Envirotech Water Treatment (Dafeng) Co., Ltd(04150700723)