Adsorptive removal capacity of gravel for metal cations in the absence/presence of competitive adsorption

Locally available and low cost granular gravel as an adsorbent material was employed to determine its capacity to remove metal cations Cu(II), Fe(II), Ni(II), and Zn(II) from single metal solution and landfill leachate samples. Adsorption kinetics and mechanism under different parameters including dosage, time, and pH were studied. It was found that the experimental results fitted to the Freundlich model suggesting an adsorption process on a multilayer heterogeneous surface for both single metal solution and landfill leachate samples. The adsorption of metal cations followed second-order kinetics occurring in a single step on the surface of gravel. The order of removal efficiency of metals was found to be Cu(II)(98%) > Fe(II)(87.5%) > Zn(II)(76.05%) > Ni(II)(36.38%) in single metal solution and Cu(II)(98.3%) > Fe(II)(83%) > Zn(II)(48%) > Ni(II)(27.32%) in landfill leachate sample at pH 7. The regeneration efficiency of the metals adsorbed on the gravel resulted in the order of Fe(II)(99.54%) > Cu(II)(99%) > Ni(II)(49.46%) > Zn (II)(2.25%).