Optimization of Pb(II) Adsorption onto Australian Pine Cones-Based Activated Carbon by Pulsed Microwave Heating Activation

This study proposed a novel method for preparing activated carbon from Australian Pine cones (APCs) to optimize Pb(II) adsorption. Based on an analysis conducted, the APCs dried powder consisted of approximately 51.32 wt% of cellulose and 21.15 wt% of lignin on average. Experiments in batch mode at 100-rpm stirring speed, pH 4.7 (± 0.3) and 27 oC (± 2 oC) were conducted to obtain the maximum adsorption capacity of Australian Pine cones activated carbon(the APCs AC) over the independent variables of contact time, initial Pb(II) concentration in solution, the concentration of NaOH activator and Pulsed Microwave Heating (PMH). As the result, the maximum Pb(II) adsorption capacity was obtained when using the APCs AC with 1 M NaOH and the PMH activation. It follows Langmuir Isotherm Model (LIM) and the pseudo-second-order kinetics model (PSOKM) with the correlation coefficients (R2) being  0.993 and 1, respectively. The LIM maximum Pb(II) adsorption capacity was 166.667 mg/g, the PSOKM maximum equilibrium Pb(II) adsorption capacity was 151.515 mg/g reached in 120-min contact time, and the PSOKM kinetics constant was 0.295 g/mg.min for 1571.89 mg/L of initial Pb(II) concentration. This optimum condition was reasonable because the PMH resulted from the dominant active site of the functional group of hydroxyl on the APCs AC for Pb(II) adsorption as shown by Fourier Transform Infrared Spectroscopy analysis, and more pores were shown in Scanning Electron Microscopy (SEM) analysis.