Effect of Sonochemical Treatment on Thermal Stability, Elemental Mercury (Hg0) Removal, and Regenerable Performance of Magnetic Tea Biochar

Elemental mercury (Hg-0) removal from a hot gas is still challenging since high temperature influences the Hg-0 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-0 from syngas. A sonochemically synthesized magnetic sorbent (TUF0.46) exhibited a more prodigious surface area with developed pore structures, ultra-paramagnetic properties, and high dispersion of Fe3O4/gamma-Fe2O3 particles than a simply synthesized magnetic sorbent (TF0.46). The results showed that TUF0.46 demonstrated strong thermostability and attained a high Hg-0 removal performance (similar to 98.6%) at 200 degrees C. After the 10th adsorption/regeneration cycle, the Hg-0 removal efficiency of TUF0.46 was 19% higher than that of TF0.46. Besides, at 23.1% Hg-0 breakthrough, TUF0.46 achieved an average Hg-0 adsorption capacity of 16.58 mg/g within 24 h under complex syngas (20% CO, 20% H-2, 5% H2O, and 400 ppm H2S). In addition, XPS results revealed that surface-active components (Fe+, O2-, O*, C = O) were the key factor for high Hg-0 removal performance over TUF0.46 from syngas. Hence, sonochemistry is a promising practical tool for improving the surface morphology, thermal resistance, renewability, and Hg-0 removal efficiency of a sorbent.

Automated summary

A thermally stable magnetic tea biochar was synthesized using a facile yet innovative sonochemical method to capture elemental mercury (Hg-0) from syngas. The synthesized magnetic sorbent demonstrated improved surface area, pore structures, paramagnetic properties, and Hg-0 removal efficiency compared to a simply synthesized magnetic sorbent. Additionally, surface-active components were identified as the key factor for the high Hg-0 removal performance of the sorbent in complex syngas.