Effect of Sonochemical Treatment on Thermal Stability, Elemental Mercury (Hg) Removal, and Regenerable Performance of Magnetic Tea Biochar.

Elemental mercury (Hg) removal from a hot gas is still challenging since high temperature influences the Hg removal and regenerable performance of the sorbent. In this work, a facile yet innovative sonochemical method was developed to synthesize a thermally stable magnetic tea biochar to capture the Hg from syngas. A sonochemically synthesized magnetic sorbent (TUF) exhibited a more prodigious surface area with developed pore structures, ultra-paramagnetic properties, and high dispersion of FeO/γ-FeO particles than a simply synthesized magnetic sorbent (TF). The results showed that TUF demonstrated strong thermostability and attained a high Hg removal performance (∼98.6%) at 200 °C. After the 10th adsorption/regeneration cycle, the Hg removal efficiency of TUF was 19% higher than that of TF. Besides, at 23.1% Hg breakthrough, TUF achieved an average Hg adsorption capacity of 16.58 mg/g within 24 h under complex syngas (20% CO, 20% H, 5% HO, and 400 ppm HS). In addition, XPS results revealed that surface-active components (Fe, O, O*, C=O) were the key factor for high Hg removal performance over TUF from syngas. Hence, sonochemistry is a promising practical tool for improving the surface morphology, thermal resistance, renewability, and Hg removal efficiency of a sorbent.