Immersion enthalpy and the constants of Langmuir model in the 3-chloro phenol adsorption on activated carbon

The adsorption process of 3-chloro phenol from aqueous solution on a activated carbon prepared from African palm stone and which presents a specific surface area of 685 m(2) g(-1), a greater quantity of total acid groups and a pH(PZC) of 6.8 is studied. The adsorption isotherms are determined at pH values of 3, 5, 7, 9 and 11. The adsorption isotherms are fitted to the Langmuir model and the values of the maximum quantity adsorbed that are between 96.2 and 46.4 mg g(-1) are obtained along with the constant K-L with values between 0.422 and 0.965 L mg(-1). The maximum quantity adsorbed diminishes with the pH and the maximum value for this is a pH of 5. The immersion enthalpies of the activated carbon in a 3-chloro phenol solution of constant concentration, of 100 mg L-1, are determined for the different pH levels, with results between 37.6 and 21.2 J g(-1). Immersion enthalpies of the activated carbon in function of 3-chloro phenol solution concentration are determined to pH 5, of maximum adsorption, with values between 28.3 and 38.4 J g(-1), and by means of linearization, the maximum immersion enthalpy is calculated, with a value of 41.67 J g(-1). With the results of the immersion enthalpy, maximum quantity adsorbed and the constant K-L, establish relations that describe the adsorption process of 3-chloro phenol from aqueous solution on activated carbon.