Non-thermal Oxygen-Helium Plasma Modification and Regeneration of Sawdust Biochar to Promote Aniline Removal

Abstract

The pollutant adsorption performance of produced biochar could be dramatically improved by low-energy cost plasma technology. Non-thermal oxygen-helium plasma was proposed to modify and regenerate sawdust biochar by enhancing oxygen-containing functional groups on the surface of the biochar. The effect of discharge gas, discharge time, carrier gas flow rate, and discharge power on the product’s performance for aniline removal was investigated in detail. Scanning electron microscope (SEM) analysis showed that plasma treatment could etch the surface of biochar and form pits. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and elemental analysis showed that the oxygen content of the modified biochar increased from 20.15% to 23.88%, and more oxygen-containing functional groups were formed on the surface. After the oxygen-helium non-thermal plasma modification, the aniline adsorption capacity of the biochar increased by about 23.5%. Meanwhile, water vapor was introduced into the plasma regeneration system. The regeneration ratio maintained at 80% after ten times of regeneration, which was much higher than the thermal regeneration ratio of 55.28%. It was speculated that the adsorption mechanism was that the amino group of aniline forms a hydrogen bond with a carbonyl group and a carboxyl group, and the carbonyl group forms an electron donor-acceptor structure with the aromatic ring of aniline.