Kinetic Equilibrium and Isotherm Modeling Adsorbed Methane Assessment on Synthesized PEEK-Porous Sorbent Carbon of Sustainable Coconut Shell Kernel

Abstract

It is important to understand methane (CH₄) adsorption onto available biomass surfaces quantitatively for its storage as Adsorbed Natural Gas (ANG). Coconut shell being among the abundant agro-waste in Malaysia has chosen with polyetheretherketone (PEEK) as a precursor for preparation of hybrid activated carbon via microwave induced potassium hydroxide activation for methane storage. M33P15 Porous carbon prepared at 300 Microwave power with 3 min irradiation and 15 wt% amount of PEEK and M33P0 was prepared under the same condition as M33P15 but without addition of PEEK. The porous carbons were used for CH₄ adsorption as the interactions between carbon and methane is based the pore diffusion and partly film diffusion. The ideal CH₄ adsorption capacities of the activated carbons were conducted using volumetric adsorption equipment at pressures (5-30 bar). The obtained experimental data at initial pH of 8.0 and 9.0 were correlated using linear regression analysis with common adsorption kinetic (Pseudo-first order, Pseudo-second order, Elovich) and isotherm models (Freundlich, Langmuir, Sip, and Toth). The pseudo-second-order kinetics describe the best fitness with a correlation coefficient of 0.9998 for sample M33P15. For adsorption isotherms, Sip model shows better fitness for sample M33P15 with the regression coefficient (R²) 0.9800 and with lowest RSMD value (0.1438) than other models. The findings revealed the potential of kinetic and isotherm models in methane adsorption applications.