Removal of Tetracycline Hydrochloride by Ball-Milled Mulberry Biochar

The recovery and utilization of Chinese medicine residue are increasingly becoming a concern. In this study, mulberry waste (a typical Chinese medicine residue) was selected as a raw material for biochar production at different pyrolysis temperatures (300, 500, and 700 °C, representing low, median, and high temperatures). This biochar was then modified by ball-milled technology a different ball-milled time of 1 to 6 h to obtain a good modification biochar for tetracycline hydrochloride (TC) adsorption. The results showed that the best modification biochar, produced by ball milling biochar (derived at 500 °C) for 3 h, referred to as QMB500. Compared to the pristine biochar (MB500), the QMB500 had higher surface area (increased by 14 times) and larger pore volume (increased by 8 times); besides, the oxygen-containing functional groups of QMB500 was richer than that of MB500, evidenced by Fourier transform infrared spectroscopy analysis. Due to these improved properties, the TC maximum adsorption capacity (modeled via Langmuir isotherms) of QMB500 increased by 4.2 times (103.7 mg·g −1 ). In addition, TC adsorption kinetic of modified QMB500 was well fitted by the pseudo-second-order model, and the TC adsorption is spontaneous; heat absorption and disorder increase process. TC adsorption greater capacity was at pH = 4 and ion strengths = 0.01 mol·L −1 NaNO 3 . These results indicate that mulberry biochar modified by ball-milled treatment is promising in environmental applications that require TC removal. Graphical Abstract