Preparation of Sewage Sludge–Based Activated Carbon for Hydrogen Sulphide Removal

The circular economy concept boosts the use of wastes as secondary raw materials in the EU renewable and sustainable framework. In wastewater treatment plants (WWTP), sludge is one of the most important wastes, and its management is being widely discussed in the last years. In this work, sewage sludge from WWTP was employed as raw material for producing activated carbon (AC) by physical-chemical activation. The prepared AC was subsequently tested for hydrogen sulphide removal in view of its further use in deodorization in a WWTP. The effects of the activation temperature and the chemical agent used (NaOH and KOH) during the activation process were studied. On the one hand, the characteristics of each AC fabricated were analysed in terms of BET (Brunauer-Emmett-Teller) surface area, pore and micropore volume, pore diameter, surface morphology and zeta potential. On the other hand, BET isotherms were also calculated. Finally, both the prepared AC and a commercial AC were tested for H2S removal from a gas stream. Results demonstrated that the optimum physical and chemical activation temperature was 600 °C and 1000 °C, respectively, and the best activated agent tested was KOH. The prepared AC showed excellent properties (specific surface area around 300 m2/g) for H2S removal, even better efficiencies than those achieved by the tested commercial AC.