Mathematical modeling of low-pressure H2S adsorption by babassu biochar in fixed bed column

Abstract

The H2S removal by a microporous babassu-derived biochar (BBC) in fixed bed column under low pressure and temperature conditions was evaluated. For this, a mathematical model was coded to describe equilibrium and mass transfer kinetics in the column. The BBC showed desirable textural properties, namely, elevated external and micropore surface areas (584 m2 g−1 and 322 m2 g−1) with super- and ultramicropores (7.8 Å and 5.8 Å) favoring the H2S diffusion. Also, various oxygenated groups provided high affinity for BBC-H2S system. The mathematical model was able to adequately describe the experimental data and to determine equilibrium (qmax = 20.61 mg g−1 and b = 16.84 L mg−1) and kinetic parameters (kG = 1.404 × 10−2 to 2.378 × 10−2 min−1 and Dax = 422.06 cm2 min−1). Laminar flow (Rep = 16.74) and small pressure drops were identified under the fluid dynamics conditions. Sensitivity analysis evidenced axial dispersion presents a minor effect over the bed performance, however for other flow conditions it should not be neglected. Also, the model showed predictive capacity, hence can support the adsorption systems design and scale-up. Overall, the BBC showed remarkable features for the H2S adsorption in fixed bed column, especially considering low-pressure and temperatures, since it allows straightforward infrastructure facilities.