Comparative Study on the Adsorption Characteristics of Heavy Metal Ions by Activated Carbon and Selected Natural Adsorbents

Abstract

In this study, adsorption of the heavy metal ions (Pb(II), Cu(II) and Cd(II)) from water by peanut shells (PS), sawdust (S) and commercial activated carbon (AC) were comparatively studied. Thus, the relationship between different adsorption parameters and different heavy metal ion removal rates was investigated. The adsorption capacity of the three adsorbents for heavy metal ions increased with an increase in temperature, pH value, contact time, adsorbent dosage, and heavy metal ion concentration, however, it decreased with an increase of adsorbent particle size. All the adsorption processes are better described by Langmuir isotherm or Freundlich isotherm. Thus, the results show good agreement with pseudo-second-order kinetics and the adsorption processes are spontaneous heat absorption processes. Herein, all adsorbents have higher affinity for Pb(II) ions, and hence possess higher removal rates. In addition, heavy metal ions were desorbed significantly at acidic conditions in the desorption experiments. The results demonstrate that PS can be used as a green adsorbent instead of AC for the adsorption of heavy metal ions from the water.