Pb (II) Adsorption over Activated Carbon Prepared from Cedrus Deodara Bark by Na₂CO₃ Activation: Optimal Design for Modelling and Process Optimization

Abstract

Cedrus deodara is an evergreen cone‐bearing tree and its bark is a common timber industry waste. Activated carbon (CDAC) was prepared from Cedrus deodara bark through Na2CO3 – activation for efficient adsorption of Pb (II) ions. D‐optimal design based on RSM revealed that optimum conditions for preparation of activated carbon involved impregnation ratio=1.02 : 1 (w/w) and pyrolysis temperature=604.7 °C. Using 0.1 g CDAC in 200 ml of 10 ppm Pb (II) solution provided 99.4 % removal at pH 6. D‐optimal design was also employed to optimize the adsorption process and to examine influence of operational parameters including pH, initial Pb (II) concentration and contact time. CDAC was characterized using FE‐SEM, EDS, FTIR, XRD and BET analysis. Adsorption followed pseudo‐second‐order kinetic model and Langmuir isotherm model with maximum monolayer adsorption capacity 236.41 mg g−1. The free energy change (▵G̊=−12.66 kJ mol−1), entropy change (▵S̊=0.28 kJ K−1 mol−1), and enthalpy change (▵H̊=72.07 kJ mol−1) revealed spontaneous and endothermic characteristics of adsorption. For evaluating the performance of CDAC, river water samples from Sangam, a pilgrimage site of India, were treated using a vertical column packed with CDAC. Additionally, the effective cost of CDAC was also evaluated.