Broussonetia papyrifera leaves were successfully converted into new magnetic adsorbents, including pretreatment using ionic liquid and magnetization via a coprecipitation technology. The resultant magnetic adsorbent was characterized with infrared spectroscopy (IR), transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. Then, it was selected to adsorb methylene blue from aqueous solutions. The adsorption behaviors could be described well by pseudo-second-order kinetic and Langmuir isotherm models. The thermodynamic analysis for adsorption displayed that the process was exothermic and feasible spontaneous. Moreover, it exhibited a well reusability in the regeneration test. This adsorbent might be an alternative candidate with the advantageous properties of simplicity, repeatability, and convenient separation for pollutant removal.