Recent research advances in adsorption removal of gaseous hydrogen sulfide by biochar

Biochar is considered as a promising gaseous hydrogen sulfide (H2S) adsorbent due to its several advantages, such as wide availability of raw materials, low cost, environmental friendliness, easy surface regulation, etc. The recent research advances in adsorption removal of gaseous H2S using biochars are reviewed. The modification methods and effects of biochar, as well as the adsorption effects and mechanisms of H2S by various modified biochars, are systematically introduced. The main process parameters, technical performance, adsorption mechanism, and advantages and disadvantages of biochar modification and H2S adsorption are summarized in detail. The main modification methods include acid/alkali high-temperature activation, microwave activation, nitrogen doping modification, metal oxide modification and some emerging modification methods. These modification methods can effectively improve the H2S adsorption performance of biochar by improving the pore structure of biochar and increasing the functional groups or/and active sites on the surface of biochar. Multimetals modification usually can achieve higher H2S adsorption capacity due to synergistic effects of multimetallic components compared to single metal modification. Free radical-induced advanced oxidation technologies (AOTs) can simultaneously improve the pore structure of biochar and increase surface functional groups, and its modification process is environmentally friendly, indicating a promising development prospect. This article is likely to offer some useful information and suggestions for developing new modified biochar adsorbents for the removal of gaseous H2S.