Dynamic adsorption of hydrogen sulfide using copper-doped hydroxyapatite synthesized from industrial waste

Hydrogen sulfide (H₂S) is a toxic, corrosive, and malodorous gas frequently detected in both industrial and indoor environments. H₂S can also originate from the breakdown of sulfur-containing household chemicals such as cleaners, degreasers, and detergents under humid conditions in indoor environments. H₂S poses significant risks to human health in enclosed spaces with poor ventilation, even at trace concentrations as low as 0.05 ppm. Adsorption-based techniques are suitable for integration into compact indoor air filtration systems for H₂S removal in confined settings at low concentrations. This study explores the H₂S removal potential of sustainable adsorbent synthesized by doping with varying levels of copper (0.31%, 0.94%, and 2.13% w/w) on carbide slag-derived hydroxyapatite (CS-HAp) via ion exchange route. Comprehensive characterization of prepared Cu-CS-HAp adsorbents was performed. The H₂S adsorption experiments were carried out in a lab-scale fixed-bed column reactor under dynamic continuous flow conditions to simulate indoor air purification scenarios. The influence of H₂S concentration and the presence of humidity on adsorption performance was systematically evaluated. Among all prepared adsorbents, Cu-CS-HAp-2.13% exhibited the highest performance with H₂S adsorption capacity of 7.78 mg/g at 100 ppm H₂S concentration in dry conditions. However, H₂S adsorption capacity dropped significantly under high humidity. Moreover, regeneration studies confirmed moderate reusability for second cycles. Overall, this work demonstrates Cu-CS-HAp as a promising, sustainable, and efficient adsorbent for H₂S removal in indoor air environments. Further research is still needed with focus on improving humidity resistance, enhancing long-term stability, and evaluating performance in the presence of co-existing indoor air contaminants.