Effect of lignocellulosic biomass composition on the performance of biochar for the activation of peroxymonosulfate to degrade diclofenac

In this study, poplar flour (PF) and walnut shell flour (WSF) with different proportions of lignocellulosic composition were selected as representative plant-based biomass precursors to prepare biochars (PB and WSB) for the activation of peroxymonosulfate (PMS). The structure of biochars and the removal performance of diclofenac (DCF) were examined in detail. Generally, the PB derived from PF that contained higher ratio of cellulose outperformed the WSB derived from WSF that contained higher ratio of lignin in the adsorption and degradation of DCF due to the more graphitized and aromatic structure of PB than that of WSB. Moreover, the adsorption and catalytic performance of two kinds of biochars were improved with the increase of pyrolysis temperature. The superior porosity property, abundant oxygen containing functional groups and good electrical conductivity of PB1000 led to the stronger capability than that of WSB1000. Nonradical oxidation mechanism including the singlet oxygen (1O2) and electron transfer was found to contribute to DCF degradation. Moreover, the PB1000 also demonstrated stronger adaptability to complex water environment than WSB1000. The findings of this work may provide enlightenment in the selection of lignocellulosic bio-wastes to prepare biochar for the degradation of organic pollutants.