Performance of alkaline impregnated biochar derived from rice hull for hydrogen sulfide removal from gas

Hydrogen sulfide (H2S) causes malodor, health disorders, and equipment corrosion, but is a constituent of a wide range of valuable gases. For efficient H2S removal, biochars derived from rice hull and loaded with four alkalis (NaOH, KOH, Na2CO3, and K2CO3) were prepared by impregnation. The H2S removal characteristics were investigated by continuous adsorption column tests. The alkaline impregnated biochars (IBCs) showed superior H2S removal performance compared to that of coconut shell activated carbon (AC) due to the enhanced chemical adsorption. The removal capacity varied depending on the alkalis and their concentration of aqueous solution for impregnation. The IBC with 5 M of NaOH solution afforded the highest removal capacity of 24.41 mg/g, which greatly exceeded 7.65 mg/g of the AC. Moreover, the height-to-diameter ratio, inlet gas flow rate, H2S gas concentration, temperature, and inlet gas moisture influenced the adsorption capacity, which mainly affect the contact and reaction between H2S and the alkali impregnated on rice hull biochar.