Gas-solid reactions for "zero-pollution" industries: investigation of acid gas removal by solid sorbents in a sustainable perspective

The growing concern over industrial pollutant emissions has driven increasingly stringent environmental policies aimed not only at reducing atmospheric pollution but also at limiting indirect burdens associated with reagent consumption and waste disposal. In this framework, the removal of acid gases such as hydrogen halides and sulfur oxides from flue gases has been widely tackled since the late 1970s. Nevertheless, challenges remain in process optimization, sorbent efficiency, and understanding the physicochemical mechanisms governing gas-solid reactions. In this context, this Ph.D. thesis investigates the reaction fundamentals of dry acid gas removal through an integrated experimental approach and proposes sustainable pathways for stabilizing and valorizing the resulting byproducts, namely Air Pollution Control residues (APCRs), usually landfilled as hazardous waste. A laboratory-scale campaign examined the removal of conventional acid gases (HCl and SO2) and an emerging pollutant (HBr) using commercial sorbents (NaHCO3 and Ca(OH)2) and surface-enhanced Ca(OH)2. Under representative conditions, NaHCO3 showed preferential reactivity toward hydrogen halides over SO2, while surface-enhanced sorbents consistently outperformed conventional materials. A major novelty lies in the multi-component testing of simultaneous acid gas removal under realistic flue-gas conditions. These experiments revealed synergistic and competitive interactions among pollutants, providing insight into reaction pathways and highlighting limitations of single-component testing. For APCRs management, residues from waste-to-energy, glass, and ceramic sectors were subjected to accelerated dry carbonation and tested in cyclic carbonation-calcination loops, demonstrating potential reuse as cost-free substitutes for virgin limestone in Calcium Looping for CO2 capture. Wet carbonation and water washing were comparatively assessed as stabilization treatments; both reduced chlorides and total dissolved solids, supporting potential reclassification of many samples from hazardous to non-hazardous waste. In conclusion, this thesis provides novel experimental evidence and integrated strategies that advance the sustainability of industrial emission control by coupling pollutant capture with circular management options for residues at an industrial scale.