Efficiently catalytic degradation of tetracycline via persulfate activation with plant-based biochars: Insight into endogenous mineral self-template effect and pyrolysis catalysis

Abstract

Endogenous mineral of plant such as potassium, calcium and iron may play a crucial role in boosting the physicochemical structure and catalytic activity of high temperature pyrolyzed plant-based biochar while it is often neglected owing to its relative less content. Herein, self-template pyrolyzed plant-based biochars were prepared from two different ash-contained agricultural wastes of peanut hull (PH, 3.2% ash) and cotton straw (CS, 0.8% ash), and aimed at investigating the relationship among the endogenous mineral fractions of plant-based biomass, physicochemical active structure and persulfate (PS) catalytic degradation activity for tetracycline (TC). The results of energy/spectral characterization showed that under the self-template effect and pyrolysis catalysis of endogenous minerals, PH biochar (PBC) possessed much more specific surface area, conjugated graphite domain, C=O and pyrrolic-N surface active functional sites than CS biochar (CBC), enhancing TC removal rate of PBC/PS to 88.37%, twice that of CBC/PS (44.16%). Meanwhile, reactive oxygen quenching and electrochemical experiments showed that electrons transfer and non-free radical pathways based on singlet oxygen contributed 92% of TC removal in PBC/PS system. Remarkably, by comparing the differences in structure and TC removal performance of pre-deashing and non-deashing prepared plant-based biochars, a possible mechanism for endogenous mineral components' self-template effect and pyrolysis catalysis role of plant-based biomass was proposed. This study provides a new insight for revealing the intrinsic mechanism of mineral elements enhancing the active surface structures and catalytic properties of plant-based biochars derived from distinct feedstocks.

Keywords: Biochar; Endogenous mineral; Non-radical pathway; Persulfate catalysis; Tetracycline removal.