The simultaneous high-effective removal of As(III) and Cd by a modified biochar derived from rice straw

The highly-effective removal of arsenic (As) and cadmium (Cd) at the same time has always been a hot and challenging topic in the world. This experiment was designed to study the removal efficiency and mechanisms of the potassium permanganate (KMnO4) modified biochar (MBC) on As(III) and Cd. The results indicated that the maximum sorption capacities of As and Cd by MBC were 141.1 and 224.4 mg/g in As(III)-Cd coexisting solution at pH 7, which were significantly higher than that in a single As(III) or Cd solution (75.0 and 122.1 mg/g, respectively). The formation of type-A ternary complex (MBC-Cd-As) and type-B ternary complex (MBC-As-Cd) in high Cd concentration (>150 mg/L) were the predominant synergy mechanisms for MBC to remove As and Cd, respectively. Moreover, the Cd reacted mainly electrostatic adsorption and & pi;-& pi; interactions with the aromatic complexes on the MBC surface. The As mainly reacted with the MnO2 and the oxidation of As(III) to As(V) was also accompanied by the sorption by MBC. In general, MBC is a highly-effective material to remove As(III) and Cd simultaneously from contaminated water.