Evaluation of Adsorption Isotherm of Plantain Activated Carbons for Simultaneous Adsorption of Pb2+ and Cd2+ Ions

ABSTRACT

The study evaluated the adsorption isotherms of plantain stalk activated carbon (PSAC) and plantain stalk activated carbon (PTAC) for simultaneous adsorption of Pb²⁺ and Cd²⁺ ions from aqueous solution. Langmuir, Freundlich and Temkin adsorption isotherms were used to evaluate the adsorption capacities PSAC and PTAC. The results of the Langmuir isotherm show that the maximum adsorption capacity (Q_m) onto PSAC and PTAC adsorbents are 6.25 mg/g and 6.21 mg/g for Pb²⁺ adsorption and 6.01 mg/g and 6.09 mg/g for Cd²⁺ adsorption. For Freundlich isotherm, the adsorption capacity (K_F) onto PSAC and PTAC is 3.2152 mg/g and 3.5877 mg/g for Pb²⁺, and 2.5294 mg/g and 2.9414 mg/g for Cd²⁺ ion. Adsorption energy estimated by the Temkin isotherm for adsorption onto PSAC and PTAC are 2624.65 J/mol and 2748.35 J/mol for Pb²⁺, and 2414.59 J/mol and 2604.84 J/mol for Cd²⁺. The adsorption capacities from the different isotherms show that the adsorption capacity for Pb²⁺ adsorption onto PSAC and PTAC is generally higher than that for Cd²⁺, while the adsorption capacity of PTAC adsorbent is slightly higher than PSAC adsorbent. Generally, Langmuir, Freundlich and Temkin isotherms have high correlations with the experimental data, but R² values from the Langmuir isotherm are consistently higher than the Freundlich and Temkin isotherms for both adsorbents. Hence, the adsorption process is predominantly a monolayer adsorption. Nevertheless, both derivatives of plantain biomass adsorbents proved to be potential and alternative adsorbents for adsorption of Pb²⁺ and Cd²⁺ from aqueous solution.

Keywords: Adsorption, Isotherms, Plantain Activated Carbon, Lead, Cadmium