3.3. Adsorption kinetics
Batch studies were conducted in order to study the rate of adsorption and the effect of contact time on the adsorption of TCP onto SMB. The adsorption of TCP as a function of time for different concentrations is shown in Fig. 3. The relatively long adsorption time denotes the slow diffusion mechanism of the TCP molecules inside the microporous structure of the SMB. Nevertheless, the experimental data obtained indicates that the adsorption process during the first phase is quite rapid, where it attains 2.0–15 mmol/g (depending on initial concentration) after 30 min. Afterwards, the rate of TCP adsorption decreases appreciably to achieve the adsorption equilibrium in about 6 h. The removal efficiency at equilibrium was 97.31% (4.86 mmol/g), 93.20% (11.65 mmol/g), 87.97% (21.99 mmol/g) and 75.99% (28.49 mmol/g) at an initial concentrations of 10, 25, 50 and 75 mmol/L, respectively. It was also observed that an increase in TCP concentration decreased the percentage removal and increased the amount of adsorption per unit weight of the adsorbent (mmol/g).