Fig. 3a shows the effect of contact time on adsorption of Pb by CMTAB. The Pb removal efficiencies at different time intervals ranging from 0 to 300 min are obtained. It is observed that equilibrium is approximately achieved within 20 min and the corresponding Pb removal efficiency reaches 85.9%.
The kinetics data were fitted by pseudo-second-order model expressed by Eq. (4) [31]: