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.