66 / 2021-06-30 12:47:18

Degradation of pyrene in polluted water using agricultural straw-derived biochar/persulfate system: performance and mechanism insight

pyrene; biochar; adsorption; persulfate; oxidation; degradation

Polycyclic aromatic hydrocarbons (PAHs) were toxic to humans and difficult to eliminate from ecosystem due to their stable molecule structures. Aiming to eliminate pyrene which was a typical PAHs in contaminated water rather than transfer only, this study attempted to use biochar/persulfate system to degrade pyrene, where persulfate acted as oxidant, and biochar acted both as adsorbent and activator. Adsorption performance of different biochars, degradation performance and the corresponding removal mechanism of pyrene in biochar/persulfate system were investigated. Three types of biochar were studied prepared from sawdust, coconut shell and agricultural straw (named BC₁, BC₂ and BC₃), and results of adsorption experiments showed that pH and biochar dosage would affect pyrene adsorption on biochar significantly. Minimized C/C₀ value could reach to 0.12, 0.09 and 0.05 for BC₁, BC₂ and BC₃, respectively (at pH 3 and biochar dosage 0.9 g/L). Among them, BC₃ was chosen to study the synergy effect to degrade pyrene with persulfate. When pH at 3, persulfate concentration at 10 mM and BC₃ dosage at 1.5 g/L, 96.0% of pyrene (C/C₀ = 0.04) could be degraded, which meant that BC₃ also could act as an activator for persulfate system to remove pyrene in further. In addition, results of XPS and FI-TR analysis proved that the catalysis of persistent free radicals (PFRs) on biochar surface was the main mechanism for persulfate activation to produce SO₄^•− to degrade pyrene, which was achieved by inducting oxygen-containing groups on biochar surface to form reactive oxygen species by PFRs. All in all, from the advantages in pyrene degradation, agricultural straw-derived biochar/persulfate system would be a feasible way to eliminate PAHs in polluted environments.