Water hyacinth derived hierarchical porous biochar absorbent: Ideal peroxydisulfate activator for efficient phenol degradation via an electron-transfer pathway.

In this paper, a facile hydrothermal pretreatment and molten salt activation route was presented for preparing a self-doped porous biochar (HMBC) from a nitrogenous biomass precursor of water hyacinth. With an ultrahigh specific surface area (2240 m2 g−1), well-developed hierarchical porous structure, created internal structural defects and doped surface functionalities, HMBC exhibited an excellent adsorption performance and catalytic activity for phenol removal via peroxydisulfate (PDS) activation. Specifically, the porous structure promoted the adsorption of PDS on HMBC, forming a highly active HMBC/PDS* complex and thereby increasing the oxidation potential of the system. Meanwhile, the carbon defective structure, graphitic N and C O groups enhanced the electron transfer process, favoring the HMBC/PDS system to catalyze phenol oxidation via an electron transfer dominated pathway. Thus, the system degraded phenol effectively with an ultralow activation energy of 4.9 kJ mol−1 and a remarkable oxidant utilization efficiency of 8.2 mol mol-oxidant−1 h−1 g−1. More importantly, the system exhibited excellent resistance to water quality and good adaptability for decontaminating different organic pollutants with satisfactory mineralization efficiency. This study offers valuable insights into the rational designing of a low-cost biochar catalyst for efficient PDS activation towards organic wastewater remediation. [Display omitted] • A hierarchical porous biochar HMBC was prepared via a facile two-step pyrolysis. • HMBC exhibited good adsorption capacity and catalytic activity for PDS activation. • Phenol was completely degraded in 30 min with high oxidant utilization efficiency. • The degradation of PE was mainly attributed to the electron transfer pathway. • The defects, graphitic N, and C C=O groups favored the electron transfer process. [ABSTRACT FROM AUTHOR]