Wheat straw derived biochar with hierarchically porous structure for bisphenol A removal: Preparation, characterization, and adsorption properties

Biochar has emerged as an inexpensive adsorbent for various contaminants, but its adsorption performance is limited by low specific surface area and porosity, and its adsorption mechanism also needs to be further elucidated. Herein, hierarchically porous biochar (HBC) derived from straw via template strategy coupled with chemical activation was applied to remove bisphenol A (BPA). HBC had abundant micro/mesopores, high surface area (2944 m2 g−1), high pore volume (1.33 cm3 g−1) and graphitic defects. Due to these advantages, HBC showed a adsorption capacity of 246.13 mg g-1, much higher than mesoporous biochar. HBC also showed a stable adsorption capacity within wide pH range and excellent selective adsorption in the presence of co-existing ions and humic acid. BPA adsorption by HBC was spontaneous and endothermic and followed Langmuir-type adsorption and pseudo-second-order kinetics. The analysis of adsorption mechanism showed that pore-filling and hydrophobic interactions dominated BPA adsorption onto HBC. This work provides mechanistic views for designing efficient biochar-based adsorbents for organic contaminant removal.