Porous hydrochar loaded nZVI as an efficient catalyst to activate persulfate for phenol degradation: Performance and mechanism

Persulfate (PS) activation by nano zerovalent iron (nZVI) is promising for water purification, which is restricted due to its easy agglomeration and oxidation. Herein, porous hydrochar loaded nZVI (nZVI@PHC) was successfully synthesized by one-step process. nZVI@PHC not only had excellent adsorption capacity (178.6 mg/g) and abundant functional groups, but also possessed highly dispersed nZVI for PS activation to produce reactive oxygen species. Impressively, 0.2 g/L of nZVI@PHC (PHC/nZVI = 5:3) and 0.4 g/L of PS could achieve 99.7 % of phenol removal within 10 min. Moreover, nZVI@PHC/PS system showed superior applicability among wide range of initial pH (3.0–9.0) and temperatures (25–55 °C). Phenol removal mechanisms were elaborated by dissolved iron ions, scavenging experiments, and electronic paramagnetic spectrometer. As a result, both non-free radical pathway mediated by O21 and free radical pathway (SO4•−, HO•, and O2•−) participated in phenol degradation. Additionally, nZVI@PHC/PS system had favorable reusability and high tolerance to co-existing substance and different water bodies. This study provides a promising strategy to tailor highly active nZVI for PS activation to organic contaminants degradation. [Display omitted] •nZVI@PHC was successfully prepared and used for PS activation to degrade phenol.•nZVI@PHC/PS system had favorable tolerance to pH value and reaction temperature.•In nZVI@PHC/PS system, slowly released Fe2+ contributed to phenol degradation.•Phenol degradation processes included free radical and non-free radical pathways.