Adsorption study of Pb(II), Cu(II) and Zn(II) from simulated acid mine drainage using dairy manure compost

Dairy manure compost (DMC) was used to be one efficient biosorbent for the removal of heavy metals from simulated acid mine drainage. Single and competitive adsorption of Pb, Cu and Zn by DMC were studied. The adsorption isothermal data fit the Langmuir isotherm better than the Freundlich isotherm model. The maximum adsorption capacities calculated by applying the Langmuir isotherm were 0.460 mmol/g for Pb, 0.428 mmol/g for Cu, and 0.237 mmol/g for Zn at pH 4.0. The single and competitive adsorption studies showed that the adsorption affinity order of the three heavy metals was Pb > Cu > Zn. The rate of adsorption of the three metals was fast, which reached equilibrium in 60 min, and followed the pseudo-second-order model well. Adsorption efficiency of the heavy metals was pH dependent and the maximum adsorption was found to occur at around 3.5 for Pb, 4.5 for Cu, 5.5 for Zn. An increase of ionic strength caused a decrease in adsorption capacity for Zn and Cu, while negligible effect for Pb. The regeneration experiments showed that the adsorbent could be regenerated and reused at least three cycles without significant decrease in adsorption capacity. The results showed DMC could have great potential in treating heavy metals in acid mine drainage. Finally, ion exchange was found to be the primary mechanism of adsorption. (C) 2011 Elsevier B.V. All rights reserved.