5.1. Adsorption Capacity

To trace the adsorption capacity changes in the adsorption process, isotherms of n-butane on AC were fitted by the Langmuir model^38,39 with the following formula (eq 10).

where q_max is the maximum adsorption capacity (g·g^–1), b is the Langmuir constant (L·mg^–1), C_e is the mass concentration after adsorption equilibrium (mg·L^–1), and q_e is the equilibrium adsorption capacity (g·g^–1).

The adsorption capacity of n-butane on AC could be fitted well by the Langmuir model, as indicated by the good relative coefficients (R² = 0.9871). According to the fitting equation in Figure ​Figure1212, q_max = 0.2674 g·g^–1 and b = 0.00299 L·mg^–1. Therefore, the maximum adsorption capacity q_max of AC was 0.2674 g·g^–1.

Fitting diagram of the adsorption capacity based on the Langmuir equation.