Preparation of Multi-Group Magnetic Biochar (MMBC) and Its Mechanism for Adsorption of Pb(II) in Aqueous Solution

Abstract

Multi-group magnetic biochar (MMBC) was prepared by encapsulating rice husk biochar (BC) in magnetic nanoiron by the liquid-phase reduction-coprecipitation method. MMBC was characterized, and its adsorption of Pb(II) was investigated. Single-factor influence experiments showed that the efficiency for removal of Pb(II) by MMBC reached 90.85% with a pH of 5.0, an adsorbent addition amount of 1 g•L-1 and a contact time of 2 h. Kinetic analyses showed that pseudo-second-order kinetics express the adsorption process of Pb(II) on MMBC more comprehensively than the pseudo-first-order or Elovich kinetic equations. The adsorption process showed good fitting to the Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm models. The maximum saturated adsorption capacity was 66.83 mg•g-1, as calculated by fitting the Langmuir equation (303 K±1). The mechanism for adsorption of Pb(II) involved electrostatic attraction, functional group complexation and ion exchange caused by the surface energy of the material. The rate for removal of Pb(II) by MMBC still reached 65% after five adsorption-desorption and regeneration cycles, which indicated that MMBC was effectively regenerated. Therefore, MMBC is a potential economical and effective remediation agent that can be employed to remove Pb(II) from wastewater.