H2S removal using cellular concrete waste as filtering material: Reactions identification and performance assessment

Abstract

The removal of hydrogen sulfide (H2S) in air using cellular concrete waste as packing material was investigated and compared to results obtained with expanded schist. Air filtration was performed under abiotic conditions. Experiments were carried out in 3 laboratory-scale PVC columns (internal diameter of 100 mm) filled with a volume of 7.8 L of material (1 m height). Filter “BF1” was filled with a mixture of cellular concrete waste and expanded schist (65%/35% volume, respectively). Filters “BF2” and “BF3” were filled with 100% expanded schist and 100% cellular concrete waste, respectively. The difference in composition between cellular concrete and expanded schist allowed the identification of major components involved in H2S removal. It was demonstrated that wet conditions are required to obtained H2S removal. For a H2S concentration of 50 ppm, removal efficiency around 40–45% was obtained at an EBRT of 56 s (whereas 28% and 4% were measured for filters filled with the mixture of packing materials and expanded schist, respectively). It was identified that the ability of cellular concrete waste to remove H2S was mainly due to reactions occurring between H2S and calcium carbonate leading to gypsum formation. A maximum elimination capacity of 7.8 g m−3 h−1 was calculated. Considering that pressure drops were low for this material (around 12 Pa m−1), H2S filtration using cellular concrete waste could be carried out beneficially as the humidification step of biofiltration systems.