Characteristics and mechanisms for highly efficient adsorption of Pb(II) from aqueous solutions by engineered vinasse biochar with cold oxygen plasma process

Vinasse based biochar was engineered by cold oxygen plasma for different treatment time between 1 and 10 min to obtain highly efficient adsorbent for Pb(II) in the aqueous solutions. The engineered biochar with largest surface area (307 m2/g) and primarily microporous structure was achieved when cold oxygen plasma is processed for 3 min, providing the highest adsorption capacity (481 mg/g) derived from 500 mg/L of Pb(II) solution. For the equilibrium time (90 min) and the favorite solution pH (5.0), the best-fitting isotherm model was Langmuir isotherm one with Qo (714 mg/g), which is superior to those of many biochar based Pb(II) adsorbents in the literature. On the basis of XRD, XPS, FT-IR instruments and surface charge measurements, the adsorption mechanisms included ion-exchange, precipitation, electrostatic attraction, cation-π interaction and complexation. The reusable engineered vinasse biochar has also applicability to real water samples without matrix effects.