Optimization of porous carbons for methane adsorption from South African coal wastes

Abstract

ABSTRACT The preparation of porous carbons by KOH activation from three different coal wastes in South Africa was modeled and optimized using an artificial neural network and whale optimization algorithm (ANN-WOA). The potential for methane adsorption of the optimized porous carbons was investigated. The optimal conditions for preparing the porous carbons, as determined by maximum surface area and micropore volume, according to ANN-WOA results, were as follows: Temperature of reaction: 800°C; activation time: 120 minutes; impregnation ratio: 1:4. SEM/EDS and BET methods were used to examine the surface properties and structural morphology of the optimized activated carbons. The methane adsorption isotherm on the three optimized porous carbons was fitted with the Toth isotherm model, which had an average R2 value of 0.9999. The maximum adsorption capacity of the three optimized porous carbons were 158.4, 147.6, and 123.1 cm3/g at 25°C and an average pressure of 37 bar. In addition, because of their high surface area and methane adsorption capacity, these materials have the potential to be used in natural gas storage, demonstrating that coal wastes in South Africa have the potential to be used as a sustainable starting material for the synthesis of porous carbons for gas storage.