Abstract

The presence of hydrogen sulfide (H2S) and ammonia (NH3) in biogas pose serious human health and environmental challenges. In this study, H2S and NH3 were successfully removed from biogas using water hyacinth-derived carbon (WHC) nanomaterials. Carbonization temperature, biogas flow rate, mass of the adsorbent and activating agent (KOH/water hyacinth (WH)) ratio were found to greatly influence the efficiency of the H2S and NH3 removal. The adsorption capacity of both H2S and NH3 was found to increase with the carbonization temperature as carbon materials prepared at 450, 550, and 650°C afforded removal efficiencies of 22, 30, and 51% for H2S and 42, 50, and 74% for NH3, respectively, after contact time of 2 h. Similarly, the KOH/WHC ratio showed huge impact on the adsorptive removal of the two species. WH materials carbonized at 650°C and activated at 700°C using 1:4, 1:2, and 1:1 KOH/WHC ratios showed removal efficiencies of 80, 84, and 93% for H2S and 100, 100, and 100% for NH3, correspondingly after 2 h contact time. The adsorption capacity of NH3 increased with the decrease in flow rate from 83 to 100% at flow rates of 0.11 and 0.024 m3/h, respectively, while that of H2S increased from 22 to 93% with flow rate 0.11 and 0.024 m3/h, respectively. The removal of H2S and NH3 increased with adsorbent mass loading. With the 0.05, 0.1, 0.2, and 0.3 g of the adsorbent, the adsorption of H2S after 1.5 h contact time was 63, 93, 93, and 95%, respectively while that of NH3 was 100% for all the adsorbent masses.

Key words: Waste water, KOH, activation ratio, carbonization temperature, flow rate.