Preparation and characterization of cattle manure-based activated carbon for hydrogen sulfide removal at room temperature

Abstract

The presence of H2S limits the use of biogas. Activated carbons (ACs) provide economic and environmental advantages with a high removal efficiency for biogas purification compared to other H2S adsorbents. In this study, ACs were prepared by steam and an increased flow of CO2 activation from dairy cattle manure at 850 ℃ and applied to remove H2S at room temperature. The H2S breakthrough capacities were evaluated using a lab-designed test. The compositional and textural properties of ACs were characterized by nitrogen adsorption, FTIR, TGA-MS, SEM and X-ray photoelectron spectroscopy (XPS) techniques before and after H2S adsorption. The 2D-NLDFT model was applied for pore size distribution. Additionally, the manufacturing cost of the best AC was estimated. The results showed that all ACs are microporous carbons with pore widths of 0.67~0.690.67–0.69 nm. The ACs prepared by CO2 activations exhibit better H2S removal performance than those activated with steam. AC4 activated by CO2 with a flow of 1000 ml/m has the largest BET surface area of 408.36 m2/g and the highest H2S breakthrough capacity of 868.45 mg/g. The micropore volume and basic surface pH play a crucial role in H2S removal, and the self-catalytic role of intrinsic sulfur on AC4 may also contribute to the oxidation of H2S. The characterization results indicate that the H2S is oxidized to elemental sulfur, sulfates/sulfuric acid and sulfites/sulfonic acids in the presence of O2 during the adsorption process. Due to the higher efficiency in removing H2S and a total feasible manufacturing cost of $1.05 per kg, AC4 can be considered a cost-effective and promising alternative for biogas desulfurization.