Spent coffee-based activated carbon: specific surface features and their importance for H2S separation process.

Area of Science:

• Materials Science
• Environmental Chemistry
• Chemical Engineering

Background:

• Hydrogen sulfide (H2S) is a toxic and corrosive gas requiring efficient removal from air.
• Activated carbons are widely used for gas adsorption, but developing cost-effective and sustainable precursors is crucial.
• Spent coffee grounds represent an abundant and underutilized organic waste stream.

Purpose of the Study:

• To prepare activated carbons from spent coffee grounds using zinc chloride activation.
• To investigate the efficacy of these activated carbons as adsorbents for hydrogen sulfide removal from air at ambient conditions.
• To characterize the prepared materials and understand the relationship between their properties and H2S separation performance.

Main Methods:

• Preparation of activated carbons via chemical activation of spent coffee grounds with zinc chloride.
• Characterization of the activated carbons using nitrogen adsorption, elemental analysis, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and thermal analysis.
• Evaluation of H2S separation performance using adsorption studies at ambient conditions.

Main Results:

• The surface properties and pore structure of the activated carbons were significantly influenced by the amount of zinc chloride used.
• The prepared carbons exhibited optimal pore sizes (10–30 Å) for both water and hydrogen sulfide adsorption.
• While inorganic residues contributed to H2S retention via salt formation, the porous surface characteristics were the primary factor governing the separation process.
• The presence of nitrogen functional groups, derived from caffeine in the coffee precursor, played a catalytic role in the oxidation of hydrogen sulfide.

Conclusions:

• Spent coffee grounds are a viable precursor for producing activated carbons suitable for hydrogen sulfide removal.
• The developed activated carbons demonstrate effective H2S separation from air due to their optimized porous structure and the catalytic activity of nitrogen functional groups.
• Further optimization of the activation process could enhance the performance of these sustainable adsorbents for air purification applications.