H 2 S removal using cellular concrete waste as filtering material Reactions identification and performance assessment

The removal of hydrogen sulfide (H 2 S) 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 H 2 S removal. It was demonstrated that wet conditions are required to obtained H 2 S removal. For a H 2 S 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 H 2 S was mainly due to reactions occurring between H 2 S 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 ), H 2 S filtration using cellular concrete waste could be carried out beneficially as the humidification step of biofiltration systems.