On-site regeneration by ultrasound activated persulfate of iron-rich Antipyrine-loaded biochar

Abstract

Adsorption process has proven its efficiency in the abatement of pharmaceuticals in liquid media, even if large volumes of wastewater need to be treated. Nevertheless, exhausted adsorbent regeneration is economically and environmentally necessary. For this reason, recent studies are aimed at finding new methods of regeneration. In this study, an on-site adsorption-regeneration method was assessed. Initially, a model pharmaceutical, Antipyrine (Apy), has been adsorbed onto a low-cost biochar. Apy adsorption followed a pseudo-second order kinetic and a Langmuir isotherm. In a second step, spent biochar was regenerated by oxidation using SO4•−. To do this, SO4•− was generated by activation of persulfate by ultrasound and assisted by the iron inherently into the biochar. To facilitate the availability of this iron, the addition of an enhancing agent such as oxalic acid was evaluated. The regenerated biochar proved its stability and reusability achieving an uptake percentage of around 87% after the third adsorption-regeneration cycle. Therefore, this on-site regeneration method could be promising for treating other kinds of adsorbents and resolving the pollution problems caused by the non-controlled throw of the exhausted adsorbents.