Pinewood pyrochar-based green catalyst as powerful persulfate activation tool for the removal of contaminants of emerging concern from wastewater

Contaminants of emerging concern (CECs) are very tenacious water pollutants, and due to their suspect or proven toxicity, persistence, and bio-accumulation, represent a significant threat to human and ecosystem safety. These compounds, ranging from pharmaceutical active substances to industrial chemicals, are not the subject of routine monitoring or emission control. The concentration of CECs in environmental samples is commonly at a very low level, indicating that traditional water treatment methods may be inadequate for their effective removal. Sulfate radical based advanced oxidation processes using heterogeneous catalysts have recently received significant attention as a viable technology for the removal of CECs. Since waste reutilization is always highly desired in the environmental engineering, biomass waste represents an excellent precursor for the production of carbon material – biochar (pyrochar and hydrochar), serving as the main component for the development of green catalysts for persulfate activation.

The aim of this study was to develop a facile one-pot green strategy for the synthesis of metal-free (heteroatom doped) pyrochar-based catalysts as efficient persulfate activators for the degradation of selected CECs belonging to pharmaceutically active compounds and pesticides. Due to comparison, a series of iron-based heteroatom doped catalyst samples was prepared using the same preparation procedure. The pinewood sawdust, as highly abundant biowaste material in Serbia, was used as carbon precursor. The catalytic abilities of the synthesized samples were tested on a water solution model mixture of 22 CECs (10 μg/l concentration of each compound). Metal-free pyrochar-based catalysts exhibited significantly higher activity compared to their Fe-based counterparts. The single doped ones showed excellent catalytic performance in relation to the co-doped ones, achieving 100% removal of 17 CECs within the first 30 min of the reaction. It is expected that this work provides new insights into the rational design of pyrochar-based catalysts for persulfate activation in practical applications of CECs-related pollution control.