where ce is the equilibrium concentration in equilibrium aqueous
phase (mg L1), qe is the amount adsorbed at equilibrium
(mg g1) in Eqs. (2)–(4). In addition to that, in Eq. (2) b is the
equilibrium adsorption coefficient (L g1) and qmax is the maximum
adsorption capacity (mg g1). In Eq. (3) kf is expressed
as adsorption capacity coefficient. n is adsorption intensity,
reflecting the trend of isotherm, and the value of n is usually
greater than 1. If the value of 1/n is greater than 2, it is believed
that the process of absorption is difficult to go on. In Eq. (4),
BT =RT/bT, T is the absolute temperature in Kelvin and R is
the universal gas constant (8.314 J mol1 K1), the constant
BT is related to the heat of adsorption; AT is the equilibrium
association constant (L min1), corresponding to the maximum
bonding energy.