Abstract
Chicken eggshell (ES) is a waste from the food industry with a high calcium content produced in substantial quantity with very limited recycling. In this study, eco-friendly sorbents from raw ES and calcined ES were tested for sulfur dioxide (SO2) and hydrogen sulfide (H2S) removal. The raw ES was tested for SO2 and H2S adsorption at different particle size, with and without the ES membrane layer. Raw ES was then subjected to calcination at different temperatures (800 °C to 1100 °C) to produce calcium oxide. The effect of relative humidity and reaction temperature of the gases was also tested for raw and calcined ES. Characterization of the raw, calcinated and spent sorbents confirmed that calcined eggshell CES (900 °C) showed the best adsorption capacity for both SO2 (3.53 mg/g) and H2S (2.62 mg/g) gas. Moreover, in the presence of 40% of relative humidity in the inlet gas, the adsorption capacity of SO2 and H2S gases improved greatly to about 11.68 mg/g and 7.96 mg/g respectively. Characterization of the raw and spent sorbents confirmed that chemisorption plays an important role in the adsorption process for both pollutants. The results indicated that CES can be used as an alternative sorbent for SO2 and H2S removal.
Highlights
Sulfur dioxide (SO2 ) and hydrogen sulfide (H2 S) are both considered toxic gases
SO2 can be removed from flue gas in many ways and this process is named as flue gas desulfurization (FGD)
raw eggshell (RES) and Calcined ES (CES) sorbents were tested for SO2 and H2 S adsorption
Summary
Sulfur dioxide (SO2 ) and hydrogen sulfide (H2 S) are both considered toxic gases. SO2 is mainly part of the flue gases while H2 S is naturally present in many fossil fuels and quickly oxidizes to SO2 upon burning. Effective utilization of biogas as biomethane is a challenge because of its costly purification steps [10] Many technologies such as adsorption, alkaline washing (absorption), membrane separation, and cryogenic distillation have been tested to efficiently removes H2 S [11]. Chicken eggshell (ES) is a waste product from the food industry and is mostly disposed in landfills in Malaysia. ES based sorbent was used for CO2 adsorption and the removal capacity was reported as 10.47 mg/g at 1 bar and 30 ◦ C [19]. The possibility of replacing conventional calcite-based sorbents with raw and calcined chicken eggshell for acidic gases removal at low temperature was appraised. Various characterization techniques like FTIR, XRD, EDX, and FESEM were used to further investigate the adsorption mechanism
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