Simultaneous adsorption behavior of heavy metals onto microporous olive stones activated carbon: analysis of metal interactions

The present work reports the synergistic and inhibitory adsorption effects involved in the multicomponent adsorption of heavy metal ions (Cu(II), Ni(II), and Cd(II)) from binary systems using chemically olive stone activated carbon (COSAC) as adsorbent. In order to evaluate the adsorption capacity of COSAC to remove studied heavy metals, adsorption of metal ions in single and binary systems were conducted. Kinetics adsorption rates in binary systems are very fast as compared to that in single ones and well represented by the pseudo second-order. Langmuir and Sips model fit mono-solute adsorption isotherms and the maximum adsorption capacity of COSAC decreased in the following order: Cd(II) > Ni(II) > Cu(II). In binary equilibrium systems, the effect of initial concentration of interfering metal ions on the removal of target ones was studied. Different mutual interactions between metal ions dealing with the decrease and the enhancement of inhibitory and synergetic effects were detected. Results showed that the effects on the adsorption of the metal ions in binary mixture strongly depend on the initial concentration of both metal ions in the solution. In most of the scenarios studied, the total amount of metal ions adsorbed was higher than the sum of the ones obtained in single solutions, suggesting synergetic interactions between the two metal ions. This study proves that COSAC is an effective adsorbent for the removal of heavy metals from multicomponent solutions.