Kinetic, isotherm and equilibrium study of adsorption of hydrogen sulfide from wastewater using modified eggshells

The studies of adsorption equilibrium isotherms and the kinetics of hydrogen sulfide-water systems on calcite-based adsorbents prepared from eggshells were undertaken. The effects of operating variables, such as contact time and initial concentration, on the adsorption capacity of hydrogen sulfide are investigated. The modified eggshells are characterized using different analytical approaches such as Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR). The batch mode adsorption process is performed at optimum removal conditions: dosage of 1 g/L, pH level of pH 6, agitation speed of 150 rpm, and contact time of 14 h for adsorbing hydrogen sulfide with an initial concentration of 100-500 mg/L. In the current study, the Langmuir, Freundlich, Temkin, and Dubinin models are used to predict the adsorption isotherms. Our equilibrium data for hydrogen sulfide adsorption agrees well with those of the Langmuir equation. The maximum monolayer adsorption capacity is 150.07 mg/g. Moreover, the kinetics of H2S adsorption using the modified calcite of eggshells follows a pseudo-second-order model. From the current work, it has been found that the calcite eggshells are a suitable adsorbent for H2S containing wastewater. Most importantly, chicken eggshells are waste products that are vastly available; hence, they could serve as a practical means for H2S adsorption.