Sewage sludge ash-derived materials for H₂S removal from a landfill biogas

H₂S removal is a key step for biogas cleaning because this component can lead to premature corrosion of the equipment and its cleaning has a significant cost. The aim of the present work was to assess the use of sewage sludge derived ash (SSA)-materials for H₂S removal from a landfill biogas. SSA and mixtures made with SSA, activated carbon (AC) and sand were tested for H₂S removal. The best removal efficiency was obtained with the mixture 80%m SSA and 20%m AC, while SSA alone was not a good adsorbent under tested experimental conditions. The materials characterization helped the adsorption mechanism understanding. Indeed, results highlighted that SSA presence stabilizes the pH on a basic range, favorable for H₂S dissociation into HS^- then its chemisorption. On the other hand, with the microporosity of AC, the contact surface between H₂S and oxygen was sufficiently large for chemisorption kinetics. It also appeared that the mixture with sand and AC adorbs non selectively H₂S but also other volatile organic pollutants present in biogas. Contrariwise, with SSA/AC mixtures, H₂S seems to be selectively chemisorbed.