Adsorption Kinetics and Equilibrium Isotherms Modeling of H2S on Hydrogel Biochar and Biochar Adsorbent from Rice Husk

Abstract

Hydrogen sulphide is a poisonous gas that is commonly found in swamps and areas of high volcanic activities. Due to the dangers and hazards that it may impose such as neurological disorders and miscarriages, continuous innovative attempts to remove the gas are in place. A study was conducted to synthesize an adsorbent that is made from activated rice husk biochar and also hydrogel biochar. This study is complementary to that study where the adsorption processes using the two adsorbents are mathematically modelled. Three parameters were studied which were the adsorbent mass, the gas flow rate, and the gas temperature. It was found that for rice husk-based activated biochar, for all three parameters, the adsorption processes could be mathematically represented using Thomas Model and Yoon-Nelson Model. Meanwhile, for rice husk-based hydrogel biochar, the adsorption process could be mathematically represented using Thomas and Yoon-Nelson Model for the effect of mass of adsorbent, and Adam-Bohart for the effect of gas flow rate and gas temperature. Although the coefficient of determination (R2) suggested that Thomas and Yoon-Nelson Model are more appropriate to be used to model the latter two parameters, because the exit concentration reached the point when it was greater than half the inlet concentration well before 0-th second, the linearly regressed equation became mathematically inconsistent with the isotherm models. Kinetic studies were also done, and it was found that the adsorption processes using the activated biochar fit both pseudo-first and pseudo-second order equation. This means that the adsorption processes using the activated biochar are both physisorption and chemisorption. Meanwhile, the adsorption processes using the hydrogel biochar fit only the pseudo-second order equation, suggesting that the adsorption process is chemisorption.