Equilibrium Isotherm, Kinetic, and Thermodynamic Studies of Divalent Cation Adsorption onto Calamus gracilis Sawdust-Based Activated Carbon

Activated carbon (RSAC) was prepared using the two steps of hydrothermal carbonization (HTC) and chemical activation from the sawdust of Calamus gracilis, commonly known as Rattan (RS). The HTC process was carried out using a Teflon-lined autoclave to produce hydrochar, followed by chemical activation using phosphoric acid (H3PO4). The highest removal percentage obtained for lead, Pb(II), and zinc, Zn(II), cations were 86.71% and 64.26%, respectively, using the initial adsorbate concentration of 350 mg/L at 30 degrees C. These values strongly indicated the promising adsorption potential of the newly prepared hydrochar-based activated carbon (RSAC) for the better management of industrial wastewater and effluents. The analysis of the equilibrium sorption data revealed that these adsorptions followed the Langmuir isotherm model and the pseudo-second order kinetic model. The adsorption process was endothermic and spontaneous. The prepared carbon (RSCAC) showed enhanced surface area with porous texture, which could effectively aid for elimination of Pb(II) and Zn(II) cations from waste water.