Kinetic, Equilibrium and Thermodynamic Studies of the Biosorption of Heay Metals by Ceratonia Siliqua Bark

Biosorption of Zn(II), Ni(II), Cu(II) and Cd(II) ions from aqueous solutions onto Ceratonia siliqua (Carob tree) bark has been investigated in a batch biosorption process. The biosorption process was found to be dependent on pH of solution, initial metal ion concentration, biosorbent dose, contact time and temperature. The experimental equilibrium biosorption data were analyzed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevic isotherm models. The Langmuir model gave a better fit than the other three models by higher correlation coefficient, R2. The maximum biosorption capacity calculated from the Langmuir isotherm was 42.19 mg/g, 31.35 mg/g, 21.65 mg/g and 14.27 mg/g for Ni(II), Zn(II), Cu(II) and Cd(II), respectively at optimum conditions. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second-order model. The negative values of Go and the positive Ho revealed that the biosorption process was spontaneous and endothermic. According to the biosorption capacity, Ceratonia siliqua bark considered as an effective, low cost, and environmentally friendly biosorbent for the removal of metal ions ions from aqueous solutions.